阅读说明：本技术 校准工具和方法 (Calibration tool and method ) 是由 E·G·凯利 J·范德弗鲁格特 N·蒂伦伯格 T·J·韦布鲁根 P·比克曼 C·J·范沃斯 于 2020-04-07 设计创作，主要内容包括：本发明涉及一种用于校准激光三角测量系统的校准工具和方法,其中,该校准工具包括限定参考平面的工具主体,其相对于测量系统可绕垂直于所述参考平面的旋转轴线旋转,其中,该工具主体设置有一个或多个校准表面,校准表面限定校准位置的图案,其中,该图案包括在远离旋转轴线的径向上延伸的至少三列和绕旋转轴线沿周向延伸的至少三排,其中,对于每列,所述相应列内的校准位置相对于参考平面的高度在垂直于所述参考平面的高度方向上有所变化,并且其中,对于每排,相应排内的校准位置的高度相对于所述参考平面在高度方向上有所变化。(The invention relates to a calibration tool and a method for calibrating a laser triangulation system, wherein the calibration tool comprises a tool body defining a reference plane, which is rotatable relative to a measurement system about an axis of rotation perpendicular to the reference plane, wherein the tool body is provided with one or more calibration surfaces, which define a pattern of calibration positions, wherein the pattern comprises at least three columns extending in a radial direction away from the axis of rotation and at least three rows extending circumferentially about the axis of rotation, wherein for each column the height of a calibration position within the respective column relative to the reference plane varies in a height direction perpendicular to the reference plane, and wherein for each row the height of a calibration position within the respective row varies in a height direction relative to the reference plane.)

1. A calibration tool for calibrating a laser triangulation system, wherein the calibration tool comprises a tool body which is rotatable relative to the measurement system about an axis of rotation which is perpendicular to a reference plane, wherein the tool body is provided with one or more calibration surfaces which define a pattern of calibration positions, wherein the pattern comprises at least three columns which extend radially away from the axis of rotation and at least three rows which extend circumferentially about the axis of rotation, wherein for each column the height of a calibration position within a respective column relative to the reference plane varies in a height direction which is perpendicular to the reference plane, and wherein for each row the height of a calibration position within a respective row varies in the height direction relative to the reference plane.

2. The calibration tool of claim 1, wherein the pattern forms a radial grid of calibration locations.

3. Calibration tool according to claim 1, wherein for each column at least half of the calibration positions within the respective column have a different height in the height direction relative to the reference plane.

4. Calibration tool according to claim 1, wherein for each column the calibration positions within the respective column decrease successively in radial direction away from the rotation axis with respect to the height of the reference plane.

5. Calibration tool according to claim 4, characterized in that the successive decrease in height has a constant decrement relative to the reference plane.

6. Calibration tool according to claim 4, characterized in that the successive decrease in height follows a certain curvature.

7. Calibration tool according to claim 1, wherein for each row at least half of the calibration positions within the respective row have a different height in the height direction relative to the reference plane.

8. The calibration tool of claim 1, wherein for each row, the height of the calibration locations within the respective row relative to the reference plane increases sequentially in a circumferential direction.

9. The calibration tool of claim 8, wherein the sequential increase in height has a constant increment relative to the reference plane.

10. The calibration tool of claim 1, wherein each calibration position within the pattern has a height in the height direction relative to the reference plane that is different from heights of other calibration positions in the same column and the same row relative to the reference plane.

11. The calibration tool of claim 1, wherein for each column, the one or more calibration surfaces comprise a separate calibration surface for each calibration position within the respective column.

12. The calibration tool of claim 11, wherein for each column, the tool body is provided with a recess extending between the calibration surfaces within the respective column to radially space the calibration surfaces apart.

13. The calibration tool of claim 12, wherein each calibration surface within a respective column defines a calibration edge at each transition from the respective calibration surface to an adjacent one of the recesses, wherein at least one calibration location is located at one of the calibration edges.

14. The calibration tool of claim 11, wherein for each column, the calibration surfaces within the respective column extend in a common plane, wherein the common plane extends at an oblique angle relative to the reference plane.

15. The calibration tool of claim 1, wherein for each row, the one or more calibration surfaces comprise a separate calibration surface for each calibration position within the respective row.

16. Calibration tool according to claim 15, characterized in that for each row the calibration surfaces in the respective row are stepped in height direction circumferentially from one calibration surface to the next.

17. The calibration tool of claim 1, wherein the pattern comprises at least five columns.

18. The calibration tool of claim 1, wherein the pattern comprises at least four rows.

19. The calibration tool of claim 1, wherein the tool body extends around the axis of rotation over only a portion of the entire perimeter.

20. The calibration tool of claim 19, wherein the tool body is formed as a circular segment.

21. A method of calibrating a laser triangulation system using a calibration tool according to claim 1, wherein the laser triangulation system comprises a laser and a camera with a field of view, wherein the method comprises the steps of:

a) providing the calibration tool at least partially within the field of view of the camera;

b) projecting a laser line onto the calibration tool with the laser triangulation system;

c) rotating the calibration tool about an axis of rotation such that the laser lines are projected at all calibration positions in a respective one of the columns; and

d) capturing images of the laser lines projected on all the calibration positions of the corresponding column with the camera.

22. The method of claim 21, further comprising the steps of:

e) repeating said steps c) and d) for another column.

23. The method as claimed in claim 22, wherein said step e) comprises the steps of: repeating said steps c) and d) for all other columns.

24. The method of claim 22, wherein the height of the calibration position of each column relative to the reference plane is predetermined, wherein the method further comprises the steps of: calibrating the laser triangulation system by associating pixels in each captured image corresponding to calibration locations in a respective column to the calibration locations within the respective column.

25. The method of claim 21, further comprising the steps of:

f) before or after said steps a) to d), providing an empty bead-apex roll with respect to the laser triangulation system, wherein the bead-apex roll has a reference plane and a base profile for supporting a bead-apex with respect to the reference plane, wherein the empty bead-apex roll is arranged with its reference plane at the same position as the reference plane of the calibration tool;

g) projecting a laser line onto the empty bead-apex drum with the laser triangulation system;

h) capturing an image of a laser line projected on the empty bead-apex roll; and

i) determining a base profile of the empty bead-apex roll relative to a reference plane of the empty bead-apex roll.

26. The method of claim 25, further comprising the steps of:

j) providing a bead-apex on the bead-apex roll;

k) measuring the bead-apex using the measurement system; and

l) subtracting the base profile of the empty bead-apex roll determined in step i) from the measured values.

27. A laser triangulation system comprising a laser, a camera and a support for supporting the laser and the camera, wherein the measurement system further comprises a drum rotatable about a rotation axis for guiding a strip through the measurement system and a calibration tool for calibrating the measurement system, wherein the support is pivotable about a pivot axis between an operating position in which the camera and the laser are directed towards the drum for measuring a strip on the drum and a calibration position in which the laser and the camera are directed towards the calibration tool.

28. The measurement system of claim 27, wherein the pivot axis is parallel to the rotational axis.

29. A measuring system according to claim 27, wherein the support is arranged to pivot about the pivot axis between the operating position and the calibration position by at least forty-five degrees.

30. The measurement system of claim 27, wherein the camera has an optical axis, wherein the calibration tool defines a reference plane perpendicular to the optical axis of the camera when the support is in the calibration position.

31. The measuring system according to claim 30, wherein the drum comprises a circumferential surface supporting the strip at a zero level relative to the camera, wherein the calibration tool comprises one or more first calibration surfaces at a predetermined height relative to the reference plane in a height direction perpendicular to the reference plane for calibrating the zero level.

32. The measuring system according to claim 30, characterized in that the laser is arranged for projecting a laser line onto the calibration tool in a lateral direction parallel to the axis of rotation of the drum, wherein the calibration tool comprises one or more second calibration surfaces which vary in the lateral direction in relation to the height of the reference plane in a height direction perpendicular to the reference plane.

33. The measurement system of claim 32, wherein the one or more second calibration surfaces vary in height in the lateral direction according to a pattern that repeats at least twice in the lateral direction.

34. A clamping strip for clamping a tyre component onto a drum, wherein the clamping strip is provided with a verification element for verifying a measuring system.

35. A clamping strip according to claim 34, wherein said clamping strip has a clamping side facing said tire component during clamping and a non-clamping side opposite to said clamping side, wherein said verification element is provided on said non-clamping side.

36. A clip strip as defined in claim 34, wherein the clip strip has a longitudinal direction, wherein the verification element is arranged at or near one end of the clip strip along the longitudinal direction.

37. The clip strip of claim 34, wherein the verification element is a slot.

38. A first cover plate covering an intermediate space between two drum segments of a tire building drum, wherein the first cover plate comprises one or more verification elements for verifying measurements of a measurement system.

39. A tire building drum comprising one or more first cover sheets according to claim 38, wherein the tire building drum is rotatable about an axially extending axis of rotation, wherein the tire building drum further comprises one or more second cover sheets, wherein each second cover sheet comprises a plurality of calibration elements arranged in a calibration pattern, wherein the verification elements of one or more first cover sheets are in different positions axially relative to the plurality of calibration elements in the one or more second cover sheets.

40. The tire building drum of claim 39 wherein the first cover plate has a longitudinal direction, wherein the measurement system comprises at least one camera for viewing a first end portion, a second end portion and a central portion of the first cover plate, respectively, arranged side by side in the longitudinal direction, wherein the one or more verification elements comprise one or more verification elements at the first end portion, one or more verification elements at the second end portion and one or more verification elements at the central portion.

41. Tyre building drum according to claim 40, wherein the one or more verification elements each comprise a group of two or more verification elements.

42. Tyre building drum according to claim 41, wherein three or more verification elements in each group form the same pattern for each group.

43. Validation tool for validating measurement values of a measurement system for measuring one or more tyre components applied around a tyre building drum, wherein the validation tool comprises an annular body extending circumferentially around a central axis and one or more reference elements arranged on the annular body and exhibiting a characteristic of the one or more tyre components, wherein the validation tool is provided with a centre reference for determining the centre of the validation tool in an axial direction parallel to the central axis.

44. A validation tool according to claim 43, wherein the validation tool is provided with one or more side references for determining one or more sides of the validation tool in the axial direction.

45. A validation tool according to claim 44, wherein the central reference and the one or more side references are arranged co-linearly in an axial direction.

46. A calibration tool for calibrating a measurement system, wherein the calibration tool comprises a calibration section with one or more calibration elements and a verification section with one or more verification elements, wherein the calibration tool is invertible about an inversion axis between a calibration position and a verification position, wherein the calibration section and the verification section exchange positions when inverted about the inversion axis.

47. The calibration tool of claim 46, wherein the calibration tool has a longitudinal direction, wherein the calibration section and the verification section are arranged adjacent to each other in a transverse direction perpendicular to the longitudinal direction, wherein the inversion axis extends between the calibration section and the verification section perpendicular to the longitudinal direction and the transverse direction.

48. The calibration tool of claim 46, wherein the calibration tool comprises one or more mounting elements for mounting the calibration tool to a support relative to the measurement system, wherein at least one of the one or more mounting elements is in the same position after inverting the calibration tool about the inversion axis.

49. The calibration tool of claim 46, wherein the one or more calibration elements comprise a plurality of calibration elements arranged in a pattern extending in a longitudinal direction of the calibration tool, wherein the one or more validation elements comprise a plurality of validation elements at different positions relative to the plurality of calibration elements in the longitudinal direction.

50. The calibration tool of claim 46, wherein the measurement system comprises first and second cameras for viewing first and second ends of the calibration tool, respectively, wherein the one or more validation elements comprise at least one validation element at the first end and at least one validation element at the second end.

51. The calibration tool of claim 50, wherein the one or more validation elements comprise a first set of two or more validation elements at the first end and a second set of two or more validation elements at the second end.

52. The calibration tool of claim 46, wherein the one or more calibration elements and/or the one or more verification elements are through holes.

53. The calibration tool of claim 46, wherein the one or more calibration elements comprise a stepped feature.

54. A method for verifying measurements of a measurement system for measuring one or more tire components, wherein the measurement system comprises at least one camera with a field of view, wherein the method comprises the steps of:

m) providing a verification element with a predetermined size in the field of view of the at least one camera;

n) measuring the one or more tire components and measuring the verification element simultaneously with or at predetermined intervals while measuring the one or more tire components;

o) verifying the measurement of said verification element with a predetermined size of said verification element; and

p) repeating steps n) and o) over time.

Technical Field

The invention relates to a calibration tool and a method for calibrating a measuring system, in particular a laser triangulation system.

Background

In the field of tire molding, measurement systems are used to measure the quality and/or characteristics of one or more tire components during various stages of production. One of said stages is the production of bead-apex (bead-apex). The bead-apex is formed by subsequently applying the bead and apex around the perimeter of a bead-apex roll. The bead-apex rollers may receive beads and apexes of various shapes and sizes. Furthermore, bead-apex rollers also come in a variety of shapes and sizes, and may be replaced by another bead-apex roller where appropriate. Finally, the portion of the bead-apex roller that supports the apex is generally conical to support the apex at an oblique angle relative to the radial direction.

Disclosure of Invention

A disadvantage of the known laser triangulation system is that it may become inaccurate over time. It is known to calibrate laser triangulation systems by measuring a stationary object having a predetermined dimension and by comparing the measured value with the predetermined dimension. However, this calibration process provides only a limited amount of feedback based on the size of the stationary object. Although the measurement system may be properly calibrated for the dimensions of the stationary object, measurements in other dimensional ranges are not yet calibrated and may be inaccurate.

It is an object of the present invention to provide a calibration tool and a method for calibrating a measuring system, in particular a laser triangulation system, wherein the calibration can be improved.

According to a first aspect, the present invention provides a calibration tool for calibrating a laser triangulation system, wherein the calibration tool comprises a tool body rotatable relative to the measurement system about an axis of rotation perpendicular to a reference plane, wherein the tool body is provided with one or more calibration surfaces defining a pattern of calibration locations, in particular a radial grid, wherein the pattern comprises at least three rows extending in a radial direction away from the axis of rotation and at least three rows extending circumferentially around the axis of rotation, wherein for each column, the calibration positions within the respective column vary with respect to the height of the reference plane in a height direction perpendicular to the reference plane, and wherein, for each row, the height of the calibration position within the respective row varies in the height direction with respect to the reference plane.

The tool body can be conveniently rotated relative to the measuring system in the same way as the bead-apex roll. By rotating the tool body, the columns can be positioned one after the other in the measuring position to measure the calibration position within each column by the measuring system. In particular, the measurement system may project laser lines onto the tool body in a radial direction or parallel to the radial direction, so that all calibration positions in the columns can be measured simultaneously along the same projected laser line. Each column of calibration locations represents or forms a particular height profile that can be used as a measurement system calibration. Since the calibration positions vary in height both in the columns and rows, the measurement values can be calibrated for a large number of calibration positions, thus providing the measurement system with a relatively large amount of feedback for various height positions.

Preferably, for each column, at least half of the calibration positions, and preferably all calibration positions within the respective column, have different heights in the height direction with respect to the reference plane. Thus, at least half of the calibration positions within the respective column generate unique calibration information for the measurement system calibration.

In one embodiment, for each column, the height of the calibration positions within the respective column relative to the reference plane decreases sequentially in a radial direction away from the axis of rotation. The successive decrease in height may be similar to or representative of the height of the drop of the bead-apex supported on the bead-apex roller, and may thus provide useful calibration information for the calibration of the measuring system.

Preferably, the successive decrease in height has a constant decrement relative to the reference plane. Thus, the calibration information generated by the calibration positions within the respective columns can be used to determine the scale of the measurement system, in particular the scale for converting pixels into actual units (i.e. millimeters). Instead, the successive decrease in height follows a certain curvature. Since a camera is used in the measurement system, the curvature may be selected, for example, to match or correct for a particular lens distortion effect.

Additionally or alternatively, for each row, at least half of the calibration positions, and preferably all calibration positions within the respective row, have different heights in the height direction relative to the reference plane. Thus, at least half of the calibration positions within the respective row generate unique calibration information for the calibration of the measurement system.

In one embodiment, for each row, the height of the calibration positions within the respective row relative to the reference plane increases sequentially in the circumferential direction. Thus, the calibration positions within the respective row may represent various heights of different bead-apexes supported on the bead-apex drum at the radial position of the respective row. When combined with the sequential decrease in height along the radial direction within a column, a pattern of several columns with radially decreasing alignment positions may be formed, wherein the height of each column increases in common with each row in the circumferential direction.

Preferably, the successive increase in height has a constant increment with respect to the reference plane. Thus, the calibration information generated by the calibration positions within the respective row can be used to determine the scale of the measurement system, in particular the scale for converting pixels into actual units (i.e. millimeters).

In one embodiment, the height of each calibration position within the pattern in the height direction relative to the reference plane is different from the height of the other calibration positions in the same column and the same row relative to the reference plane. Thus, each calibration position within the pattern generates unique calibration information for calibration of the measurement system.

Those skilled in the art will appreciate that a calibration tool according to the present invention may comprise only a single calibration surface in each column, row or whole pattern. Such a single calibration surface may for example have a gradually decreasing height in the radial direction and a gradually sloping height in the circumferential direction. The measurement system will then be configured to take measurements at certain locations on the single calibration surface, which locations correspond to the calibration locations. A single calibration surface can hold countless calibration positions.

In contrast, in the embodiment shown in the figures, for each column, one or more calibration surfaces comprise a separate calibration surface for each calibration position within the respective column. By having different, separate calibration surfaces, the calibration positions are not easily confused and can easily be identified by the measurement system, i.e. by detecting transitions from one calibration surface to another.

Preferably, for each column, the tool body is provided with a recess extending between the respective alignment surfaces within the respective column to radially space the respective alignment surfaces apart. By spacing the columns apart, the calibration positions are less likely to be confused. Furthermore, the presence of the recess between the calibration surfaces allows for measurements in the recess by sharp edges and/or a base level or zero level.

More preferably, each calibration surface within the respective column defines a calibration edge at each transition from the respective calibration surface to an adjacent one of the recesses, wherein at least one calibration position is located at one of the calibration edges. The calibration edge can be easily detected and/or measured and can therefore be used as an excellent calibration position.

In a further embodiment, for each column, the calibration surfaces within the respective column extend in a common plane, wherein the common plane extends at an oblique angle with respect to the reference plane. The common plane of inclination is similar to or represents an obliquely descending or conical surface of the bead apex supported on the bead apex roll. An additional advantage of a common plane is that all calibration positions are also located in the same common plane.

Additionally or alternatively, for each row, the one or more calibration surfaces comprise a separate calibration surface for each calibration position within the respective row. By having different, separate calibration surfaces, the calibration positions are not easily confused and can easily be identified by the measurement system, i.e. by detecting transitions from one calibration surface to another.

Preferably, for each row, the calibration surfaces within the respective row are stepped in height direction circumferentially from one calibration surface to the next. The stepped height from one calibration surface to the next means that its calibration surface can be easily distinguished from the calibration surface of the leading row in the circumferential direction of the respective row for each subsequent row. Furthermore, the height of each calibration surface may be constant in the circumferential direction between the steps, so that a representative measurement of the respective calibration position may be made at any position in the circumferential direction between the steps. Therefore, the accuracy of the rotational positioning of the calibration tool with respect to the measurement system is of less importance.

In another embodiment, the pattern comprises at least five columns, preferably at least eight columns. Additionally or alternatively, the pattern comprises at least four rows, preferably at least five rows. The number of columns determines the number of height profiles that can be calibrated. The number of rows determines the number of calibration positions within each column, i.e. within each height profile.

In a further embodiment, the tool body extends around the axis of rotation over only a part of the entire perimeter. Preferably, the tool body is formed as a circular section. When the tool body is not a complete ring or loop, the tool body may be relatively compact, i.e. relatively compact in comparison to a bead-apex roll.

According to a second aspect, the invention provides a method of calibrating a laser triangulation system using a calibration tool according to any of the preceding embodiments, wherein the laser triangulation system comprises a laser and a camera with a field of view, wherein the method comprises the steps of:

a) providing the calibration tool at least partially within the field of view of the camera;

b) projecting a laser line onto the calibration tool with the laser triangulation system;

c) rotating the calibration tool about an axis of rotation such that the laser lines are projected at all calibration positions in a respective one of the columns; and

d) images of the laser lines projected on all calibration positions in the corresponding column are captured with the camera.

This method relates to the practical implementation of the calibration tool according to the first aspect of the invention and therefore has the same technical advantages, which will not be repeated hereafter.

In a preferred embodiment of the method, step d) comprises the steps of: repeating steps c) and d) for another column or all other columns. Thus, more or all calibration positions may be measured to have the maximum amount of calibration data.

In a further embodiment of the method, the height of the calibration position of each column with respect to the reference plane is predetermined, wherein the method further comprises the steps of: calibrating the laser triangulation system by associating pixels in each captured image corresponding to calibration locations of a respective column to the calibration locations within the respective column. The correlation may produce a scale for each calibration location that converts the pixel to a real unit, i.e., microns, millimeters, or centimeters.

In a further embodiment, the method further comprises the steps of:

f) before or after steps a) to e), providing an empty bead-apex roll with respect to the laser triangulation system, wherein the bead-apex roll has a reference plane and a base profile for supporting a bead-apex with respect to the reference plane, wherein the empty bead-apex roll is arranged with its reference plane at the same position as the reference plane of the calibration tool;

g) projecting a laser line onto the empty bead-apex drum with the laser triangulation system;

h) capturing an image of a laser line projected on the empty bead-apex roll; and

i) determining a base profile of the empty bead-apex roll relative to a reference plane of the empty bead-apex roll.

During the production of the bead-apex, the base profile of the bead-apex roll is covered by the bead-apex which is currently supported on the bead-apex roll. Although the height of the bead-apex relative to the reference plane may be measured, the measurement does not indicate the actual height of the bead-apex relative to the bead-apex roller. Thus, when determining the base profile before production, i.e. when the bead-apex roll is still empty, the measuring system has more information from which the actual height of the bead-apex relative to the bead-apex roll can be determined.

Preferably, the method further comprises the steps of:

j) providing a bead-apex on the bead-apex roll;

k) measuring the bead-apex using the measurement system; and

l) subtracting the base profile of the empty bead-apex roll determined in step i) from the measured values.

The subtracted result may represent the actual height of the bead-apex relative to the bead-apex roll.

According to a third aspect, the present invention provides a laser triangulation system comprising a laser, a camera and a support for supporting the laser and the camera, wherein the measurement system further comprises a drum rotatable about an axis of rotation for guiding a strip through the measurement system and a calibration tool for calibrating the measurement system, wherein the support is pivotable about a pivot axis between an operating position in which the camera and the laser are directed at the drum for measuring a strip on the drum and a calibration position in which the laser and the camera are directed at the calibration tool.

Since the laser and the camera are supported on the same or common support, they can be pivoted together between the respective positions easily and quickly, i.e. during a short interruption in the production process of the strip or even during the production process. Since the calibration position is different from the operating position, the calibration can be performed off-line.

Preferably, the pivot axis is parallel to the axis of rotation.

In a further embodiment, the support is arranged to pivot about the pivot axis between the operating position and the calibration position by at least forty-five degrees, and preferably by at least sixty degrees. Thus, the two positions may be sufficiently spaced apart to prevent interference of the calibration tool with the production process at the operating position.

In another embodiment, the camera has an optical axis, wherein the calibration tool defines a reference plane perpendicular to the optical axis of the camera when the support is in the calibration position. Thus, the camera may be positioned directly above the calibration tool to capture an optimal image of the laser line projected on the calibration tool.

In another embodiment, the drum comprises a circumferential surface supporting the strip at a zero level relative to the camera, wherein the calibration tool comprises one or more first calibration surfaces at a predetermined height relative to the reference plane in a height direction perpendicular to the reference plane for calibrating the zero level. The calibrated zero level may be used to determine the height of the measured strip above the calibrated zero level.

In another embodiment, the laser is arranged for projecting a laser line onto the calibration tool in a lateral direction parallel to the axis of rotation of the drum, wherein the calibration tool comprises one or more second calibration surfaces which vary in the lateral direction in relation to the height of the reference plane in a height direction perpendicular to the reference plane. Thus, along a single laser line, several heights corresponding to different second calibration surfaces can be detected. The measurement data regarding the height of the second calibration surface may be used to determine the scale of the measurement system, in particular the scale for converting and/or correlating pixels in the image to actual units, i.e. micrometers, millimeters or centimeters.

Preferably, the height of the one or more second calibration surfaces varies in the lateral direction according to a pattern repeated at least twice, preferably at least three times, in the lateral direction. By repeating the pattern, the camera can be calibrated with respect to more positions in the lateral direction, i.e. across a large part of the camera's field of view in the lateral direction.

According to a fourth aspect, the invention provides a gib for clamping a tire component onto a drum, wherein the gib is provided with a verification element for verifying a measurement system.

The gib may be mounted at a predetermined position on an empty drum (i.e. no tyre components clamped to the drum). At the predetermined location, the measuring system associated with the cylinder may measure the gib including the verification element to verify that the previously calibrated measuring system is still meeting the requirements. In particular, the verification element may have a known or predetermined pattern, shape or size to check whether the measurement values still correspond to said known or predetermined pattern, shape or size. Since the gib may be mounted on the drum in a position substantially corresponding to its operating position on the drum during clamping of the tyre component. Thus, verification can be done online (i.e., at the same location where the gib is normally installed).

In a preferred embodiment, the grip strip has a gripping side facing said tire component during gripping and a non-gripping side opposite to said gripping side, wherein said verification element is provided on said non-gripping side. Thus, the verification element can be easily observed from the outside while clamping the gib on the cylinder.

In a further embodiment, the gib has a longitudinal direction, wherein the verification element is arranged at or near one end of the gib in the longitudinal direction. By arranging the verification element at or near one end of the gib, it is easy to see even if for some reason the gib is covered in the central area.

In further embodiments, the verification element is a slot. The characteristics of such slots can be easily captured using cameras and laser triangulation.

According to a fifth aspect, the invention provides a first cover plate covering an intermediate space between two drum segments of a tire building drum, wherein the first cover plate comprises one or more verification elements for verifying a measurement value of a measurement system.

The verification element on the first cover plate may be used to verify the measurement system after the initial calibration, i.e. when the measurement system has been calibrated using one or more calibration elements and/or tools. The verification element is arranged on the drum and can be detected when it is not covered by the tyre component. Since the verification element is provided on a portion of the cylinder that is also shown during operation of said cylinder, the verification of the first cover plate can be carried out on-line, i.e. at the same position where the cover plate is located during production.

According to a sixth aspect, the present invention provides a tyre building drum comprising one or more first cover plates according to the fifth aspect of the present invention, wherein the tyre building drum is rotatable about an axially extending rotation axis, wherein the tyre building drum further comprises one or more second cover plates, wherein each second cover plate comprises a plurality of calibration elements arranged in a calibration pattern, wherein the verification elements of one or more first cover plates are in different positions in axial direction with respect to the plurality of calibration elements of the one or more second cover plates. By having the verification element and the calibration element at different positions, different values can be used to verify the measurement system to determine whether the scale determined during calibration is correctly interpolated to the value expected by the verification element.

The tyre building drum has the same advantages as the first cover plate of the fifth aspect of the invention. In particular, because the verification element is in a different location than the calibration element, they can be used to verify the calibration.

Preferably, the first cover plate has a longitudinal direction, wherein the measuring system comprises one or more cameras arranged side by side for viewing a first end portion, a second end portion and a central portion of the first cover plate, respectively, arranged side by side in the longitudinal direction, wherein the one or more verification elements comprise one or more verification elements at the first end portion, one or more verification elements at the second end portion and one or more verification elements at the central portion. Thus, one or more cameras may be calibrated by capturing images of the verification element in the respective portions. Preferably, the one or more verification elements comprise a set of two or more verification elements per section, more preferably three or more verification elements per section. Most preferably, three or more verification elements in each set form the same pattern for each set. Thus, each camera may be calibrated with substantially the same pattern.

According to a seventh aspect, the present invention provides a validation tool for validating measurements of a measurement system for measuring one or more tyre components applied around a tyre building drum, wherein the validation tool comprises an annular body extending circumferentially around a central axis and one or more reference elements provided on the annular body and representing a property of the one or more tyre components, wherein the validation tool is provided with a central reference for determining the centre of the validation tool in an axial direction parallel to the central axis.

The validation tool may correspond generally to the validation tool disclosed in WO 2016/122311 a1, which is incorporated herein by reference. The position of the validation tool on or along the tire building drum may be slightly inaccurate. This can be compensated for as long as the center of the validation tool is known. Once centered, the tire building drum with the validation tool around or beside it can be moved axially until the validation tool is in the position relative to the measurement system where the tire building drum is normally located during operation. Alternatively, the measurement system may slightly offset the measurements to compensate for any deviation of the center of the validation tool relative to the measurement system.

Preferably, the validation tool is provided with one or more side references for determining one or more sides of the validation tool in the axial direction. The side may represent the side of the tire building drum.

More preferably, the central reference and the one or more lateral references are arranged co-linearly in the axial direction. Thus, the central reference and one or more lateral references can be measured simultaneously, i.e. by projecting laser lines on all references.

According to an eighth aspect, the invention provides a calibration tool for calibrating a measurement system, wherein the calibration tool comprises a calibration section with one or more calibration elements and a validation section with one or more validation elements, wherein the calibration tool is invertible about an inversion axis between a calibration position and a validation position, wherein the calibration section and the validation section swap positions when inverted about the inversion axis.

Thus, the calibration tool may also be used as a validation tool simply by changing its orientation, i.e. by flipping, reversing or causing around said inversion axis. Thus, no separate tool is required to validate the measurement system after initial calibration.

Preferably, the calibration tool has a longitudinal direction, wherein the calibration section and the verification section are arranged adjacent to each other in a transverse direction perpendicular to the longitudinal direction, wherein the inversion axis extends between the calibration section and the verification section perpendicular to the longitudinal direction and the transverse direction.

In a further embodiment, the calibration tool comprises one or more mounting elements for mounting the calibration tool to a support with respect to the measurement system, wherein at least one of the one or more mounting elements is in the same position after inverting the calibration tool about the inversion axis. Thus, the same mounting element or elements may be used to mount the calibration tool in any position.

In another embodiment, the one or more calibration elements comprise a plurality of calibration elements arranged in a pattern extending in a longitudinal direction of the calibration tool, wherein the one or more validation elements comprise a plurality of validation elements at different positions in the longitudinal direction relative to the plurality of calibration elements. By having the verification element and the calibration element at different positions, different values may be used to verify the measurement system to determine whether the scale determined during calibration is correctly interpolated to the value expected by the verification element.

In another embodiment, the measurement system comprises a first camera and a second camera for viewing the first end and the second end of the calibration tool, respectively, wherein the one or more validation elements comprise at least one validation element at the first end and at least one validation element at the second end. Thus, each camera may be calibrated by capturing an image of the verification element in the respective portion. Preferably, the one or more authentication elements comprise a first set of two or more authentication elements at the first end and a second set of two or more authentication elements at the second end. More preferably, each set comprises three or more verification elements.

In another embodiment, the one or more calibration elements and/or the one or more verification elements are through holes. Thus, the calibration tool can be used in a backlight system, wherein a light bar is provided on one side of the calibration tool and a camera is provided on the opposite side of the calibration tool to capture light passing through the through-hole.

In another embodiment, the one or more calibration elements comprise stepped features that enable the measurement system to be calibrated also in the height direction.

According to a ninth aspect, the present invention provides a method for verifying measurements of a measurement system for measuring one or more tire components, wherein the measurement system comprises at least one camera with a field of view, wherein the method comprises the steps of:

m) providing a verification element with a predetermined size in the field of view of the at least one camera;

n) measuring said one or more tire components and measuring said verification element simultaneously with or at predetermined intervals while measuring said one or more tire components;

o) verifying the measurement of said verification element with a predetermined size of said verification element; and

p) repeating steps n) and o) over time.

When the core is performed in-line, it may be repeated at any time during production, at specific intervals, or even continuously. Thus, when the measurement system is no longer properly calibrated due to wear or tolerances, immediate action can be taken.

The various aspects and features described and illustrated in this specification may be applied separately where possible. These individual aspects, in particular aspects and features described in the appended independent claims, may be the subject of divisional applications.

Drawings

The invention will be elucidated on the basis of exemplary embodiments shown in the schematic drawings, in which:

FIG. 1 shows a top view of a bead-apex roll with a bead-apex applied and a measurement system for measuring the bead-apex;

FIG. 2 shows a cross-sectional view of the bead-apex roll and bead-apex taken along line II-II in FIG. 1;

FIG. 3 shows a cross-sectional view of the bead-apex roll and bead-apex taken along line III-III in FIG. 1;

fig. 4 shows a view of a calibration tool according to a first embodiment of the invention for replacing a bead-apex roll during a calibration method.

FIG. 5 shows a top view of the calibration tool according to FIG. 4;

FIG. 6 shows a cross-sectional view of the calibration tool taken along line VI-VI in FIG. 5;

FIG. 7 shows a cross-sectional view of the calibration tool taken along line VII-VII in FIG. 5;

FIG. 8 shows a side view of a laser triangulation system according to a second embodiment of the invention in an operating position;

FIG. 9 shows a side view of the measuring system according to FIG. 8 in a calibration position;

FIG. 10 shows a top view of the measurement system in the calibration position of FIG. 8;

FIG. 11 shows a view of a tire building drum with a holding strip according to a third embodiment of the present invention;

FIG. 12 shows the gib of FIG. 11 in isolation;

FIG. 13 shows a detail of a clip strip according to circle XIII in FIG. 12;

FIG. 14 shows a view of a tire building drum with a first cover plate and a second cover plate according to a fourth embodiment of the present invention;

FIG. 15 shows the first cover plate of FIG. 14 in isolation;

FIG. 16 shows a detail of the first cover plate according to circle XVI in FIG. 15;

FIG. 17 shows a view of a tire building drum and validation tool according to a fifth embodiment of the present invention;

fig. 18 shows a front view of the calibration tool according to fig. 17 in isolation;

FIG. 19 shows an isometric view of a production line, a measurement system and a calibration tool for strips or sheets according to a sixth embodiment of the invention;

FIG. 20 shows a top view of the calibration tool of FIG. 19 in a calibration position, in isolation;

FIG. 21 shows a top view of the calibration tool of FIG. 20 in a validation position;

FIG. 22 shows a top view of a calibration tool according to a seventh embodiment of the invention; and

fig. 23 shows an isometric view of the calibration tool according to fig. 22.

Detailed Description

Fig. 1, 2 and 3 show a bead apex roll 7 for producing a bead apex 8. In the exemplary embodiment, bead-apex drum 7 is formed as a disc 70 having a central hub 71 and a bead-apex support surface 72 extending circumferentially around central hub 71. The bead-apex roll 7 has: a reference plane P, i.e. its mounting plane or its bottom surface, and a base profile B for supporting the bead-apex 8 with respect to the reference plane P. The bead-apex roller 7 is typically mounted to a roller mount or roller drive (not shown) and is driven in rotation about a rotation axis S1, which rotation axis S1 extends concentrically through the central hub 71 in a direction perpendicular to the reference plane P.

The bead apex 8 is formed by first applying a bead 80 on the bead apex support surface 72 around the central hub 71 of the bead-apex roller 7, and then by applying an apex 81 around the bead 80. The bead-apex support surface 72 may be slightly inclined to assume a tapered orientation, i.e., an inclined angle to the reference plane P. Different bead-apex rollers may be provided for different bead-apexes depending on their respective dimensions, i.e., diameter, thickness and taper.

Fig. 1, 2 and 3 also show a measuring system 9, which measuring system 9 is used for measuring a bead apex 8 on a bead apex roll 7. The measuring system 9 is preferably a laser triangulation system with a laser 90 for projecting a laser line L on the bead-apex 8 and a camera 91 for capturing an image of the projected laser line L. The camera 91 has a field of view FOV as shown in fig. 2.

Fig. 4-7 show a calibration tool 1 for calibrating a measurement system 9 as shown in fig. 1, 2 and 3. The calibration tool 1 is arranged to be placed at the same position as the bead-apex roll 7. In other words, when the measuring system 9 is to be calibrated, the calibration tool 1 temporarily replaces the bead-apex roller 7.

As shown in fig. 4, the calibration tool 1 comprises a tool body 10, which tool body 10 is rotatable relative to the measurement system 9 about a rotation axis S1 perpendicular to the reference plane P. Preferably, the calibration tool 1 replaces the bead-apex roller so that the rotation axis S1 of the calibration tool 1 corresponds to the rotation axis S1 of the bead-apex roller 7 before its removal. Moreover, the tool body 10 may have similar mounting features, i.e. a mounting plane extending in the same plane as the mounting plane of the bead-apex drum before its removal. More particularly, the reference plane P for measuring the height on the bead-apex roller 7 and the calibration tool 1 may be the same. Thus, the calibration tool 1 may exhibit at least some of the characteristics of the bead-apex roll 7.

The rotation axis S1 extends in an axial direction and defines a radial direction R perpendicular to the rotation axis S1 and a circumferential direction C around the rotation axis S1.

In the exemplary embodiment, tool body 10 extends around rotational axis S1 for only a portion of the entire perimeter. In particular, the tool body 10 is formed as a circular segment. The tool body 10 may, for example, extend about the axis of rotation S1 within a range of less than one hundred eighty degrees of the perimeter, preferably within a range of less than one hundred twenty degrees. Alternatively, the tool body may extend over the entire circumference, i.e. form a disk-shaped tool body similar to a disk-shaped bead-apex drum. The tool body may also be configured in a ring or loop shape, as long as it can still be rotatably mounted about the axis of rotation S1. The tool body 10 may have a unitary or one-piece shape. Alternatively, the tool body 10 may comprise several interconnected parts, elements, sections or sections forming different features of the tool body 10, as described below.

As best seen in fig. 4 and 5, the tool body 10 is provided with a plurality of calibration surfaces 11 defining a pattern G of calibration positions K. In the exemplary embodiment, each calibration surface 11 is distinct from the other calibration surfaces 11, i.e. is delimited from the other calibration surfaces 11 by a clear boundary. The calibration surface 11 may for example be formed by different interconnected parts of the tool body 10. Thus, each calibration surface 11 may be measured as a separate surface. Alternatively, the pattern G may be formed by a single continuous calibration surface (not shown), in which case the calibration position K is only virtual or imaginary, i.e. the calibration position K is selected by the measurement system 9 according to a predetermined pattern. The continuous surface can hold an infinite number of calibration positions K, the number of which is limited only by the accuracy of the camera 91.

In FIG. 5, the pattern G includes ten rows A1-A10 extending away from the axis of rotation S1 in the radial direction R and five rows B1-B5 extending in the circumferential direction C about the axis of rotation S1. In this way, a radial grid of calibration positions K can be formed. When a greater or lesser number of calibration positions K are desired, the number of columns A1-A10 and rows B1-B5 may be selected differently. To provide at least some useful amount of feedback to the measurement system 9, it appears that a minimum of three columns and three rows are required.

As best seen in the radial section of fig. 6, for each column a 1-a 10, the tool body is provided with recesses 12 extending between the respective alignment surfaces 11 within the respective column a 1-a 10. Each recess 12 separates two calibration surfaces 11 in the radial direction R. At each transition from the respective collimating surface 11 to an adjacent one of the recesses 12, each collimating surface 11 within the respective column a 1-a 10 defines a collimating edge 13. Conveniently, at least one calibration position K may be selected at one of said calibration edges 13.

As best seen in the radial cross-section of fig. 6, for each column a 1-a 10, the height of the calibration position K within the respective column a 1-a 10 relative to the reference plane P varies in a height direction H perpendicular to the reference plane P and/or parallel to the axis of rotation S1. Similarly, as best seen in the circumferential cross-section of fig. 7, for each row B1-B5, the height of the calibration position K within the respective row also varies in the height direction H relative to the reference plane P.

In the exemplary embodiment, for each column A1-A10, calibration surfaces 11 within the respective column A1-A10 extend in a common plane D, as shown in FIG. 6. The common plane D extends at an oblique angle with respect to the reference plane P. Alternatively, the calibration surfaces 11 may be in different planes, i.e. in stepped and/or parallel planes (not shown). When stepped calibration surfaces 11 are used in columns A1-A10, the recesses 12 do not necessarily stand out between the calibration surfaces 11. The angle of inclination may be different or the same for each column A1-A10 to reflect the different shape of the apex strips.

As shown in fig. 7, for each row, the respective calibration surfaces 11 in the respective row are stepped in the height direction H from one calibration surface 11 to the next calibration surface 11 in the circumferential direction C. The recess is not required due to the step between the calibration surfaces 11. However, if the respective calibration surfaces 11 in the respective row B1-B5 are arranged in a common plane (not shown) similar to the respective calibration surfaces 11 in the columns A1-A10, recesses may also be provided between the respective calibration surfaces 11 in the respective row B1-B5.

From the above paragraphs, those skilled in the art will appreciate that the shape and relative orientation of the calibration surface 11 are susceptible to variation, and that the scope of the present invention is not necessarily limited to any particular shape, provided that the technical effect of providing multiple calibration positions K in the pattern G is obtained. The transition from one calibration surface 11 to the other may be stepped, abrupt, gradual or smooth, for example.

As best seen in FIG. 6, for each column A1-A10, all calibration positions K within the respective column A1-A10 have different heights in the height direction H relative to the reference plane P. More specifically, the height of the calibrated positions K within the respective column a 1-a 10 with respect to the reference plane P decreases sequentially or gradually in a radial direction R away from the axis of rotation S1. Preferably, the successive reduction of the height has a constant decrement or decrement with respect to the reference plane P.

As best seen in FIG. 7, for each row B1-B5, all of the calibration positions K within the respective row B1-B5 have different heights in the height direction H relative to the reference plane P. More specifically, the height of the calibrated positions K in the respective row B1-B5 with respect to the reference plane P increases sequentially or gradually in the circumferential direction C. Preferably, the successive increase in height has a constant increment with respect to the reference plane P.

Therefore, as shown in fig. 4, the height of each of the calibration positions K within the pattern G in the height direction H with respect to the reference plane P is different from the heights of the other calibration positions K in the same column a 1-a 10 and the same row B1-B5 with respect to the reference plane P. In other words, each column a 1-a 10 of calibration positions K forms a height profile with a different height at each calibration position K, while the height of each calibration position K in the respective column a 1-a 10 is also different in height compared to the other calibration positions in the same row B1-B5. Preferably, the decrement in each column A1-A10 is the same for each column A1-A10 and/or the increment in each row B1-B5 is the same for each row B1-B5. In this case, the height profiles are offset equally from one column A1-A10 to the next.

Prior to calibration, the varying height of the calibration surface 11 relative to the reference plane P is predetermined, i.e. measured and verified, so that the measurement results of the measurement system 9 can be compared with the predetermined height of the calibration surface 11 to calibrate the measurement system 9.

A method for calibrating a measuring system 9, in particular a laser triangulation system, by using the aforementioned calibration tool 1 will be elucidated below with reference to fig. 1 to 7.

The method comprises the following steps:

a) the calibration tool 1 is at least partially arranged within the field of view FOV of the camera 91, as shown in fig. 6;

b) projecting a laser line L onto the calibration tool 1 with the laser triangulation system 9, as shown in fig. 5;

c) rotating the calibration tool 1 about the axis of rotation S1 such that the laser line L is projected in all calibration positions K of a respective one of the columns a 1-a 10;

d) capturing images of the laser lines L projected on all the calibration positions K of the respective columns A1-A10 with the camera 91; and

e) repeating steps c) and d) for another column in columns A1-A10.

In step a), the calibration tool 1 may be arranged with its reference plane P at the same position as the reference plane P of the bead-apex roller 7 during bead-apex production. Therefore, it is not necessary to adjust the measurement system 9 to capture an image of the calibration tool 1.

By capturing an image of the laser line L in step d), calibration data can be collected about the height profile of the respective column a 1-a 10. In particular, any transition, edge or height variation may be captured and processed by a suitable processor in the measurement system 9. Preferably, step e) involves repeating steps c) and d) for all other ranks A1-A10. Thus, a maximum amount of calibration data may be collected.

For each column a 1-a 10, the calibration position K may be located on the calibration edge 13, as shown in fig. 6, so that the measurement system 9 may identify the transition at the calibration edge 13 as the calibration position K.

After capturing the images in step e), the measurement system 9 may be calibrated by associating the pixels in each captured image corresponding to the calibration position K of the respective column a 1-a 10 with a predetermined height of said calibration position K within said respective column a 1-a 10. In particular, the height of the calibration position K captured within the respective column A1-A10 may be used to determine the proportion of pixels to real unit conversion, i.e. from pixels to micrometers, millimeters or centimeters.

Optionally, the method may further comprise the steps of:

f) before or after steps a) to e), providing an empty bead-apex roll 7 with respect to a laser triangulation system 9, as shown in fig. 1-3, without bead-apex 8;

g) projecting a laser line L onto the empty bead-apex drum 7 by using a laser triangulation system 9;

h) capturing an image of the laser line L projected on the empty bead-apex drum 7; and

i) the base profile B of the empty bead-apex roll 7 is determined relative to the reference plane P of the empty bead-apex roll 7.

In step f), the bead-apex roller 7 is set with its reference plane P at the same position as the reference plane P of the calibration tool. Therefore, the measurement system 9 does not have to be adjusted. Furthermore, the determined height of the base profile B can easily be compared with the height of the calibration position K, since they are measured with respect to the same reference plane P.

Finally, the method may further comprise the steps of:

j) bead apex 8 is disposed on bead apex roll 7, as shown in FIGS. 1-3;

k) measuring the bead apex 8 using a measuring system 9, as shown in fig. 1-3; and

l) subtracting the basic profile B of the empty bead-apex roll 7 determined in step i) from the measured values.

The result of the subtraction can represent the actual height of the bead apex 8 in the height direction H relative to the bead apex roller 7.

Fig. 8 and 9 show an alternative laser triangulation system 109 according to a second embodiment of the invention. The measurement system 109 includes a laser 190, a camera 191, and a guide roller, pulley, or drum 106 rotatable about an axis of rotation S2 for guiding the tape 108 through the measurement system 109. Camera 191 has an optical axis M and a field of view FOV. The laser 190 is placed at an oblique angle with respect to the optical axis M. The laser 190 is arranged for projecting a laser line L onto the calibration tool 101 in a transverse direction X1 parallel to the axis of rotation S2 of the drum 106. The drum 106 has a circumferential surface 160 that supports the tape 108 at a zero level relative to the camera 191 of the measurement system 109. The laser 190 is arranged to project a laser line L onto the circumferential surface 160 of the drum 106 and through the strip 108 to measure the height profile of the strip 108 relative to a zero level. The measurement system 109 also includes a support 192 for supporting the laser 190 and camera 191 relative to the drum 106. The measurement system 109 is further provided with a calibration tool 101 for calibrating the measurement system 109.

As shown by comparing fig. 8 and 9, the support 192 is pivotable about a pivot axis U between an operating position (fig. 8) in which the camera 191 and the laser 190 are directed towards the drum 106 to measure the strip 108 on said drum, and a calibration position (fig. 9) in which the laser 190 and the camera 191 are directed towards the calibration tool 101. Preferably, the pivot axis U is parallel to said rotation axis S2. Preferably, the support 192 is arranged to pivot about the pivot axis U between the operating position and the calibration position by at least forty-five degrees, and preferably by at least sixty degrees.

Since the laser 190 and camera 191 share the same support 192, they can pivot while maintaining the same relative orientation. Furthermore, the laser 190 and the camera 191 may be easily and quickly pivoted between the respective positions, i.e. during a short interruption in the production process of the strip 108 or even during the production process. Since the calibration position is different from the operating position, the calibration can be performed off-line.

As best seen in fig. 8 and 9, the calibration tool 101 includes a tool body 110 that defines a reference plane Q. When the support 192 is in the calibration position of fig. 9, the reference plane Q is preferably perpendicular to the optical axis M of the camera 191.

As shown in fig. 9, the calibration tool 101 comprises one or more first calibration surfaces 111 at a predetermined height with respect to the reference plane Q in a height direction H2 perpendicular to said reference plane Q for calibrating a zero level. Preferably, the one or more first calibration surfaces 111 are at the same distance from the camera 191 in the calibration position as the distance between the circumferential surface 160 and the camera 191 in the operating position of fig. 8.

As shown in fig. 10, the calibration tool 101 includes one or more second calibration surfaces 112, the height of the second calibration surfaces 112 in the height direction H2 with respect to the reference plane Q varying in the lateral direction X1. In particular, the height of the one or more second calibration surfaces 112 varies in the transverse direction X1 according to a pattern that is repeated at least twice, preferably at least three times, on said transverse direction X1. Thus, along a single laser line L, several heights corresponding to different second calibration surfaces 112 can be detected. The measurement data regarding the height of the second calibration surface 112 may be used to determine the scale of the measurement system 109, in particular the scale for converting and/or correlating pixels in the image to actual units, i.e. micrometers, millimeters or centimeters. By repeating the pattern, the camera can be calibrated with respect to more locations in the landscape X1, i.e., across most of the FOV of the camera 191 in the landscape X1.

Fig. 11 shows a tire building drum 206 and a grip strip 201 for gripping a tire component to the drum 206. Typically, a measurement system (not shown) is disposed adjacent to the drum 206 to measure the shape, size, and/or height of the tire components on the drum 206. The drum 206 has a rotational axis S3. The gib has a longitudinal direction Y1 and is arranged to be placed on the drum 206 with its longitudinal direction Y1 parallel or substantially parallel to the axis of rotation S3 of the drum 206. The gibs are arranged to be held on the drum 206 by magnetic, vacuum or mechanical holding means.

Such a clip strip is known per se. However, as shown in fig. 12 and 13, the clip strip according to the invention is provided with a verification element 211 for verifying the measuring system. In particular, the grip strip 201 has a gripping side 202 and a non-gripping side 203, the gripping side 202 facing the tire component during gripping, the non-gripping side 203 being opposite the gripping side 202. The verification element 211 is conveniently arranged on the non-clamping side 203 such that it is easily visible from the outside. More particularly, the verification element 211 is arranged at or near one end of the grip strip 201 in the length direction Y1 of the grip strip 201, so that it is less likely to be covered by tire components during production.

In this exemplary embodiment, the verification element 211 is a slot, as shown in detail in fig. 13. However, the skilled person will recognise that many variations of the verification element 211 fall within the scope of the invention, as long as it can be used to verify the measurement, accuracy, calibration and/or repeatability of the measurement system.

Fig. 14 illustrates the tire building drum 306, the tire building drum 306 being rotatable about a rotational axis S4 extending in the axial direction W to receive one or more tire components (not shown). Typically, a measurement system (not shown) is disposed near the drum 306 to measure the shape, size, and/or height of the tire components on the drum 306. The drum 306 includes a plurality of radially expandable and radially contractible sections. As the segments radially expand, the diameter and/or circumference of the drum 306 increases and an intermediate space is formed circumferentially between the segments. The drum 306 is provided with a plurality of cover plates 301, 302 for covering the intermediate spaces between the sections.

The plurality of cover plates 301, 302 comprises one or more first cover plates 301 with one or more verification elements 311 for verifying the measurement, accuracy, calibration and/or repeatability of the measurement system. The plurality of cover plates 301, 302 further comprises one or more second cover plates 302 with a plurality of calibration elements 312 for calibrating the measurement system. The calibration elements 312 are arranged on the one or more second cover plates 302 in a regular pattern in the axial direction of the drum 306. The verification elements 311 of the one or more first cover plates 301 are offset in the axial direction W relative to the plurality of calibration elements 312 in the one or more second cover plates 302.

Fig. 15 and 16 show one of the first cover plates 311 in more detail. The first cover plate 301 has a longitudinal direction Y2 and a first end portion 321, a second end portion 322 and a central portion 323 in said longitudinal direction Y2. In the exemplary embodiment, the measurement system includes a first camera, a second camera, and a third camera arranged side-by-side to view first end portion 321, second end portion 322, and central portion 323, respectively. The one or more verification elements 311 include a first set of two or more verification elements 311 at the first end 321, a second set of two or more verification elements 311 at the second end 322, and a third set of two or more verification elements 311 at the central portion 323. Preferably, each group comprises three or more verification elements 311. More preferably, three or more verification elements 311 in each set form the same pattern for each set.

Fig. 17 illustrates a tire building drum 406 for receiving one or more tire components. Typically, a measurement system (not shown) is disposed adjacent the drum 406 to measure one or more of the tire components applied around the tire building drum 406. Fig. 17 also shows a verification tool 401 for verifying the measurement values of the measurement system. The verification tool 401 includes: an annular body 410, the annular body 410 extending circumferentially about a central axis Z; and one or more reference elements 420, the reference elements 420 exhibiting characteristics of the one or more tire components disposed on the annular body 410. The annular body 410 is arranged to fit concentrically around or along the tire building drum 406. The validation tool 401 may generally correspond to the validation tool disclosed in WO 2016/122311 a1, which is incorporated herein by reference.

The position of the validation tool 401 on or along the tire building drum may be slightly off-set, particularly in the axial direction W2 along or parallel to the central axis Z. This can be compensated for as long as the center of the validation tool 401 is known. To this end, the validation tool 401 is provided with a central reference 411 for determining the centre of the validation tool 401 in the axial direction W2.

Once centered, the tire building drum 406 with the validation tool 401 around or beside it may be moved in the axial direction W2 until the validation tool 401 is in a position relative to the measurement system where the tire building drum 401 would normally be during operation. Alternatively, the measurement system may slightly offset the measurements to compensate for any deviation of the center of the validation tool 401 from the measurement system.

Optionally, the validation tool 401 is provided with one or more end or side references 412 for determining one or more sides of the validation tool 401 in the axial direction W2. Preferably, the central reference 411 and the one or more lateral references 412 are arranged collinearly in the axial direction W2.

Fig. 19 shows a strip production line 507 for producing strips 508, in particular for tyre manufacturing. The strip production line 507 comprises a conveyor 570, in this example a roller conveyor, which is broken along a measurement line T at a measurement location to allow a measurement system 509 to measure a property of the strip 508, i.e. the tread, carcass or gum layer (breaker), or the fold of the strip around the edge of the gum layer, as the strip 508 passes through the break. In particular, the width of the strip 508 is measured at the measurement line T. In this example, the measurement system 509 comprises a backlight unit 590 for emitting light towards the measurement line T and a first camera 591 and a second camera 592 opposite the backlight unit 590 for detecting light transmission at the measurement line T along the side edges of the strip 508 in a manner known per se.

In order to calibrate the measurement values of the measurement system 509, a calibration tool 501 is provided. The calibration tool 501 is arranged to be mounted between the backlight unit 590 and the cameras 591, 592 in a measuring position. As shown in more detail in fig. 20, the calibration tool 501 comprises a tool body 510 extending in a longitudinal direction Y3.

The tool body 510 includes a calibration section 502 with one or more calibration elements 521 and a verification section 503 with one or more verification elements 531. In fig. 20, the calibration tool 501 is positioned in a calibration position in which the longitudinal direction Y of the tool body 510 extends parallel or substantially parallel to the measurement line T. In the calibration position, the measurement line T extends across one or more calibration elements 521 of the calibration section 502.

The calibration tool 501 may be reversible or invertible about an inversion axis V1 between a calibration position as shown in fig. 20 and a verification position as shown in fig. 21. In the verification position, the measurement line T extends across one or more verification elements 531 of the verification section 503. Thus, the calibration section 502 and the verification section 503 are actually inverted. In other words, the calibration segment 502 and the verification segment 503 at the measurement line T alternate or swap positions when inverted about the inversion axis V1.

Preferably, the calibration section 502 and the verification section 503 are arranged adjacent to each other in a transversal direction X2 perpendicular to the longitudinal direction Y3. In the exemplary embodiment, an inversion axis V1 extends perpendicular to longitudinal direction Y3 and transverse direction X2 between calibration section 502 and verification section 503. More specifically, in this particular embodiment, the inversion axis V1 is upright, vertical, or substantially vertical. Alternatively, the inversion axis may also run parallel to the measurement line T between the calibration section 502 and the verification section 503 or through the centers of the two sections 502, 503 parallel to the transverse direction X2.

As shown in fig. 20, the calibration tool 501 comprises one or more mounting elements 505 for mounting the calibration tool 501 to a support with respect to the measurement system 509 of fig. 19. As shown by comparing fig. 20 and 21, preferably at least one of the one or more mounting elements 505 is in the same position at least after inverting the calibration tool 501 about the inversion axis V1. Thus, the calibration tool 501 can be mounted in two positions in substantially the same way.

As shown in fig. 20 and 21, the one or more calibration elements 521 includes a plurality of calibration elements 521 arranged in a pattern extending in a longitudinal direction Y3 of the calibration tool 501. Similarly, the one or more verification elements 531 comprise a plurality of verification elements 531. However, the verification element 531 is offset in the longitudinal direction Y3 with respect to the calibration element 521.

As best seen in fig. 19, a first camera 591 and a second camera 592 are arranged for viewing the first end 511 and the second end 512, respectively, of the calibration tool 501. In particular, the cameras 591, 592 view the area in the calibration tool 501 where the side edges of the strip 508 would normally cross the measurement line T. The one or more verification elements 531 include a first set of two or more verification elements 531 at the first end 511 and a second set of two or more verification elements 531 at the second end 512. Preferably, each set includes three or more verification elements 531.

In the exemplary embodiment, one or more calibration elements 521 and/or one or more verification elements 531 are through-holes. This makes the calibration tool 501 suitable for use in a backlight measurement system. Alternatively, the calibration element and the verification element may be provided as slits or protrusions, for example when calibrating and verifying laser triangulation systems.

Fig. 22 and 23 show an alternative calibration tool 601 according to a seventh embodiment of the invention, which differs from the calibration tool 501 according to the sixth embodiment of the invention in that its calibration section 602 is provided with one or more calibration elements 621 which are stepped or have a step-like feature 622 in the height direction H3 perpendicular to the longitudinal direction Y3, to allow a more accurate calibration of the height measurement of the camera. The validation section 603 likewise has a validation element 631 offset in the longitudinal direction Y3 relative to the calibration element 621. Similar to the previously discussed calibration tool 501 according to the sixth embodiment of the present invention, the alternative calibration tool 601 is reversible or invertible about the inversion axis V2 between the calibration position and the verification position. In this case, the inversion axis V2 extends in the longitudinal direction Y3 between the calibration section 602 and the verification section 603.

In some of the embodiments described above, verification of the measurements of the measurement system may be performed on-line, meaning that the tire component may be measured while measuring one or more verification elements. In such an embodiment, a verification element is disposed within the field of view of at least one camera of the measurement system. The verification step may then be repeated over time, at regular intervals, or even continuously.

It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not intended to limit the scope of the invention. From the above discussion, many variations will be apparent to those skilled in the art that still are encompassed by the scope of the present invention.

List of reference numerals

Calibration tool

10 tool body

11 calibration surface

12 recess

13 calibrating the edge

7 tire bead-apex rubber strip roller

70 disc

71 center hub

72 bead-apex support surface

8 bead-apex strip

80 bead

81 triangle adhesive tape

9 measurement system

90 laser

91 Camera

101 calibration tool

111 first calibration surface

112 second calibration surface

106 roller

160 peripheral surface

108 strips

109 measurement system

190 laser

191 Camera

192 support

201 holding strip

211 verification element

202 clamping side

203 non-clamping side

206 roller

301 first cover plate

302 second cover plate

306 tyre building drum

311 verification element

312 calibration element

321 first end part

322 second end portion

323 central portion

401 validation tool

406 tire building drum

410 tool body

411 center reference

412 side reference

420 reference element

501 calibration tool

502 calibration section

521 calibration element

503 verification section

531 verification element

510 tool body

511 first end portion

512 second end portion

505 mounting element

507 strip production line

570 conveyor

508 strip

509 measurement system

590 backlight unit

591 first camera

592 second camera

601 calibration tool

602 calibration section

621 calibration element

622 step

603 verification section

631 authentication element

Columns A1-A10

Row B1-B5

C circumferential direction

D common plane

FOV field of view

G-pattern or radial grid

H1 height direction

H2 height direction

H3 height direction

K calibration position

L laser line

M optical axis

P reference plane

Q reference plane

R radial direction

S1 rotation axis

S2 rotation axis

S3 rotation axis

S4 rotation axis

T measuring line

U pivot axis

V1 inverted axis

V2 inverted axis

W1 axial direction

W2 axial direction

X1 transverse direction

X2 transverse direction

Y1 longitudinal direction

Y2 longitudinal direction

Y3 longitudinal direction

Z central axis