阅读说明：本技术 用于测量管道的横截面尺寸的方法和设备 (Method and apparatus for measuring cross-sectional dimensions of a pipe ) 是由 M·古米内里 于 2019-10-02 设计创作，主要内容包括：描述了一种用于测量由热塑性材料制成的沿直线方向(D1)进给的管道(T)的横截面的总体尺寸的设备(1),用于在笛卡尔平面(OXY)上检测管道(T)的外表面上标识的四个点(A、B、C、D)的位置的装置,这些点(A、B、C、D)位于源自笛卡尔平面(OXY)的原点的四条相应半直线上。(An apparatus (1) for measuring the overall dimensions of a cross section of a pipe (T) made of thermoplastic material fed in a rectilinear direction (D1) is described, means for detecting, on a cartesian plane (OXY), the position of four points (A, B, C, D) identified on the outer surface of the pipe (T), these points (A, B, C, D) being located on four respective half-lines originating from the origin of the cartesian plane (OXY).)

1. A method for measuring the size of a cross-section of a pipe (T) made of thermoplastic material fed in a rectilinear direction (D1), comprising the steps of:

-defining a Cartesian plane (OXY) having an origin (O) within a cross-section of the pipe (T) to be measured and substantially perpendicular to a rectilinear direction (D1) of feeding the pipe (T),

-preparing four distance measuring sensors (S1, S2, S3, S4) outside the duct (T) along respective half-lines originating from the origin (O) of the Cartesian plane (OXY), each half-line forming a respective angle (α 1, α 2, α 3, α 4) apart from each other with the axis (X) of the X-axis of the Cartesian plane (OXY),

-measuring the distance (D1, D2, D3, D4) of each of the sensors (S1, S2, S3, S4) from the outer surface of the pipe (T), the distances (D1, D2, D3, D4) being measured along the half-straight line to define the coordinates on the Cartesian plane (OXY) of the point of intersection (A, B, C, D) of the half-straight line with the outer surface of the pipe (T),

-calculating an equation of an ellipse passing through the intersection point (A, B, C, D) so as to define the shape and position of the duct (T) with respect to the sensors (S1, S2, S3, S4) and the cartesian plane (OXY).

2. The method according to claim 1, characterized in that the step of preparing the sensors (S1, S2, S3, S4) along respective half-lines comprises the step of selecting the half-lines in such a way as to respect the following conditions: at most three lines of said half-lines constitute bisectors of respective quadrants of said cartesian plane (OXY).

3. The method according to claim 1 or 2, characterized in that the step of preparing the sensors (S1, S2, S3, S4) comprises the step of positioning the sensors (S1, S2, S3, S4) along a circumference (Cs) centered on the origin (O) of the cartesian plane (OXY).

4. An apparatus for measuring the size of a cross section of a pipe made of thermoplastic material fed in a rectilinear direction (D1), comprising:

-means for detecting the position on a Cartesian plane (OXY) of four points (A, B, C, D) identified on the outer surface of the pipe (T), said points (A, B, C, D) being separated from each other and lying on four respective half-straight lines originating from the origin (O) of the Cartesian plane (OXY),

-a processing unit configured for calculating an equation of an ellipse passing through the four points (A, B, C, D), the positions of the four points being identified by the detection means.

5. The apparatus according to claim 4, characterized in that said position detection means comprise four distance measuring sensors (S1, S2, S3, S4) positioned outside said duct (T) along said half-line originating from the origin (O) of said Cartesian plane (OXY).

6. The apparatus of claim 5, wherein the distance measuring sensor (S1, S2, S3, S4) is an optical sensor.

7. The apparatus of claim 5, wherein the distance measuring sensor (S1, S2, S3, S4) is an ultrasonic sensor.

8. The apparatus according to any one of claims 4 to 7, characterized in that the semi-straight line obeys the following condition: at most three of the half-lines constitute bisectors of respective quadrants of the cartesian plane (OXY).

Technical Field

The present invention relates to a method for measuring the cross-sectional dimensions of a pipe.

Background

More specifically, the invention relates to a method for measuring the overall dimensions of a cross section of an extruded pipe made of thermoplastic material, which is also capable of measuring its deviation from a nominal cylindrical shape.

The method according to the invention is actuated along a production line of pipes made of thermoplastic material.

The invention also relates to a device for measuring the overall dimensions of a cross section of a pipe made of thermoplastic material.

The expression "pipe made of thermoplastic material" mainly refers to a pipe designed for the manufacture of conduits (conduits) for the supply and/or discharge of fluids (pressurized and non-pressurized) for example in building works, sewers, drinking water distribution networks and in general fluid (even under pressure) distribution networks.

Continuous measurement of the diameter of extruded pipes made of thermoplastic material is generally useful, since it makes it possible to know the quality conditions of the production in progress, and in particular it allows monitoring the roundness characteristics of the extruded pipe. In fact, during the extrusion process, since the pipe has not yet hardened, the pipe, due to the effect of its own weight, generally tends to deviate from the cylindrical shape set by the extruder and to adopt a shape with an elliptical section. The reference technical standard may set a maximum allowable value for deviations from the nominal cylindrical shape. Thus, knowing in real time the shape adopted by the pipe with an elliptical cross-section makes it possible to intervene quickly to correct the undesirable "out of roundness" effect.

In addition, there are extrusion lines in which the extrusion apparatus is able to modify in real time the diameter of the extruded pipe (without having to stop the extrusion process and reactivate the line for a new diameter of pipe to be produced), in such a way as to be ready on the same line for pipes of different diameters within a considerable range of diameters.

Obviously, in order to allow a quick transition from one diameter to another, the machines located downstream of the extruder, such as the feeding unit, the cutting machine, the baler, etc., should also be able to be automatically reconfigured for the new diameters produced and for this the new diameters are "warned" to them, in such a way as to thus start their respective reconfiguration.

Currently, in order to signal the variation of the diameter produced to the machine downstream of the extruder, the continuous measurement of the diameter of the extruded pipe is generally performed by an electromechanical device, usually with rollers of horizontal axis, on which the pipe made of thermoplastic material being fed rests, and two rollers with vertical axis, which are pushed by means of a suitable system (elastic, pneumatic, etc.) so as to make them adhere to the two sides of the pipe in transit, in diametrically opposite positions.

By means of suitable calibration, the mutual position of the two rollers with vertical axis defines the diameter of the pipe passing through the apparatus.

However, the known type of measuring device described above is not without limitations and drawbacks.

First of all, the devices of the type described provide only a measurement of the diameter of the pipe measured at the point of contact between the pipe and the rollers of the measuring device, without providing further information about the remaining geometry of the pipe, since only the "horizontal" diameter is actually measured, unless other rollers are inserted which are not placed vertically, but the device is significantly complex and increases in cost.

If the measuring device is used on a production line for producing pipes having a large diameter and/or thickness, the effect of the deviation from a nominal cylindrical shape to an elliptical cross-sectional shape may be particularly pronounced for them due to the relative weight (as described above) and/or poor circumferential stiffness.

After such deformation, the measuring device will have an incorrect reading, which indicates that there is a pipe with a certain diameter, whereas it may instead be a pipe with a different nominal diameter but with an elliptical deformation.

In the present description, the expression "measurement of the overall dimensions of a cross-section" refers to both the measurement of the actual shape of the cross-section (that is to say, any cross-section perpendicular to its direction of extension and fed along the production line) and the actual numerical measurement of the cross-section.

In fact, as mentioned above, an extruded pipe does not necessarily have a perfectly cylindrical shape, but due to typical deformations related to its nature it more generally adopts a shape with an elliptical cross-section, although a circular cross-sectional shape can be identified as a particular shape of an elliptical cross-section.

Generally, as previously described, the larger the diameter and thickness of the pipe, and therefore the corresponding weight per unit length of pipe, the greater the deviation from a nominal cylindrical shape.

Disclosure of the invention

The object of the present invention is to provide a method and a device for measuring the dimensions of a cross-section of a pipe made of thermoplastic material, which do not have the drawbacks of the prior art.

Another object of the present invention is to provide a method for measuring the dimensions of a cross-section of a pipe which is efficient and practical and easy to implement.

It is a further object of the present invention to provide an apparatus for measuring the overall dimensions of a cross-section of a pipe which is simple and inexpensive to manufacture and practical to use.

These and other objects, which will be more apparent in the following description, are achieved according to the present invention by a measuring method and device comprising the technical features described in one or more of the appended claims.

Brief description of the drawings

With reference to the attached drawings, which schematically illustrate a preferred embodiment of the method for an implementation of the invention, with reference to the above-mentioned objects, the technical features of the invention are clearly described in the claims, and the advantages thereof are apparent from the detailed description below.

Detailed description of the preferred embodiments of the invention

As illustrated in the accompanying drawings, reference numeral 1 denotes in its entirety an apparatus for measuring the overall dimensions of a cross-section of a pipe T made of thermoplastic material at a given instant T in the course of an extrusion process.

With reference to the figures, the cartesian plane OXY of the axis X, Y is positioned perpendicular to the feeding direction D1 of the extruded tube T made of thermoplastic material.

The cross-section of the pipe T lying on the plane OXY at the instant T is therefore shown in the drawing as an oval shape, since an oval is considered to be the most reasonable shape that the extruded pipe can take due to the deformations it may undergo in the extrusion line (due to its own weight or any mechanical action caused by the shell (containment) and/or the supporting rollers).

The direction D1 is perpendicular to the drawing plane and, for simplicity, is indicated in the origin O of the cartesian plane OXY.

The above-mentioned deformations to which the extruded tube T made of thermoplastic material is subjected are mainly due to the effect of gravity and to the fact that gravity has a vertical tendency, the ellipses approximately describing the cross section (i.e. the deformation) of the actual tube will have opposite half-axes, one parallel and the other perpendicular to the vertical, respectively.

In view of this, the cartesian plane has been oriented in such a way that the relative axis Y of the coordinates is parallel to the vertical direction.

In this way, whatever the deformation from circular to elliptical, the ellipse defining the cross section of the duct T lying on the cartesian plane OXY at the instant T will in any case have its half-axes parallel to the two axes X, Y of the cartesian plane OXY.

Referring again to the drawing, the four optical sensors S1, S2, S3, S4 are positioned along a half-straight line originating from the origin O of the cartesian plane OXY and lying on the same plane.

The optical sensors S1, S2, S3, S4 are advantageously of the laser type.

The optical sensors S1, S2, S3, S4 are configured and oriented as follows: relative measurements are performed along the respective half-straight lines, identifying respective distances d1, d2, d3, d4 at which there is an intersection A, B, C, D of the outer surface of the pipe T with each half-straight line at time T.

For each optical sensor S1, S2, S3, S4, the source position is known by the respective location coordinates (x1, y1), (x2, y2), (x3, y3), (x4, y4) in the cartesian plane OXY (not superimposed) and the respective distance is acquiredd1, d2, d3, d4 (measured by sensors), the coordinates (x) of four points A, B, C, D in the plane OXY are thus derived_A,y_A)、(x_B,y_B)、(x_C,y_C)、(x_D,y_D)。

The above half-lines define respective angles α 1, α 2, α 3, α 4 with the axis X of the cartesian plane X axis.

The above-mentioned half-lines each preferably (but not necessarily) lie on respective different quadrants of the cartesian plane OXY.

In general, there are at most three bisectors of the quadrant that can be the plane OXY in the half-line for the existence of coherent solutions to the system of equations to be described below.

The just specified condition constitutes a condition that is necessary to satisfy the solution of the above system of equations.

More generally, the above-mentioned angles α 1, α 2, α 3, α 4 are therefore separated from each other by at most three angles equal to 45 ° + k equal to 90 °, k equal to 0, 1, 2, 3, measured in a counter-clockwise direction starting from the positive X-axis of the cartesian plane OXY.

As an example, referring to the case illustrated in the drawings, α 1 ═ 45 °, α 2 ═ 145 °, α 3 ═ 220 °, α 4 ═ 330 °, by measuring the angle in the counterclockwise direction from the positive X axis.

Advantageously, the optical sensors S1, S2, S3, S4 are then positioned along the circumference Cs, the center of which is located at the origin O of the cartesian plane OXY.

In this way, the distance of each optical sensor S1, S2, S3, S4 from the origin O of the cartesian plane is the same.

The above-mentioned optical sensors S1, S2, S3, S4 define for the measuring device 1 respective means of measuring, on a cartesian plane, the position of four points A, B, C, D identified on the outer surface of the pipe T.

According to an alternative embodiment of the invention, which is not further described, the position measuring device described above comprises different types of sensors, such as for example ultrasonic sensors.

The apparatus 1 further comprises (not illustrated) a processing unit configured for calculating an equation of an ellipse lying in the plane OXY and passing through four separate points A, B, C, D, the positions of which are identified by the optical sensors S1, S2, S3, S4, with the half-axes parallel to the respective cartesian axes of the plane OXY.

After calculating the equation of the ellipse in this way, the processing unit then obtains the coordinates of the center of the ellipse in the cartesian plane OXY, and the values of the semi-axes a and b of the ellipse, and thus the average diameter and the relative eccentricity.

As previously mentioned, assuming that the most reasonable shape that an extruded T-pipe can take is a shape with an elliptical cross-section, the general equation considers an ellipse that simply translates in a plane:

where E (α, β) represents the center of the ellipse and a and b represent the larger and smaller semi-axes, respectively, of an axis parallel to the OXY plane.

The following are given:

it is possible to rewrite the equation as follows:

this is equivalent to:

q(α-x)²+p(β-y)²＝pq

referring to the drawings, assume a circle C with a center O_sThe four sensors S1, S2, S3, S4 are in the following manner: the respective angles α 1, α 2, α 3, α 4 formed by the half-straight line and the positive axis of the X axis are different from each other, and the above-described requirements are satisfied.

The radius R of the circumference Cs is such as to encompass the maximum nominal diameter of the pipe T which can be extruded in the production line on which the measuring device 1 is mounted.

Thus, in the particular example illustrated, α 1 ≠ α 2 ≠ α 3 ≠ α 4, where only α 1 has the form 45 ° + k ═ 90 °, where k ≠ 0.

By indicating, as mentioned, A, B, C, D, four separate measurement points on the outer surface of the pipe, i.e. the points identified by the optical sensors S1, S2, S3, S4, the distances thereof from the sensors having been measured by them, they are defined as follows:

to determine the four unknowns α, β, p, q, the ellipse is set to pass through four points A, B, C, D, thereby obtaining the following system of equations s 1:

subtracting equation (2) from equation (1) gives:

q[(α-xA)²-(a-xB)²]+p[(β-yA)²-(β-yB)²]＝0

from there after some steps:

(yA²-yB²)p+(xA²-xB²)q-2(xA-xB)αq-2(yA-yB)βp＝0

now, it is given:

the following formula is obtained:

(yA²-yB²)p+(xA²-xB²)q-2(xA-xB)u-2(yA-yB)v＝0

similarly, subtracting equation (3) from equation (1) and subtracting equation (4) from equation (1) we derive the following set of equations:

the system of equations described above makes it possible to express p, q and u, and thus also α and β, as a function of v.

By substituting the obtained values in any of the equations of the system of equations s1, it is possible to determine v and thus the values of p, q, α and β.

In this way, by means of simple operations performed by the processing unit described above and not illustrated, all the characteristic values of the ellipse approximating the cross-sectional shape of the pipe T at the general instant T, that is to say mainly the values of the greater and lesser half-axes a, b, respectively, are obtained.

Depending on the values of the half-axes, the processing unit is configured to obtain an average diameter of the pipe T of (a + b)/2 and a relative eccentricity in terms of the maximum deviation between the nominal diameter Dn that the pipe T should have and the maximum of the absolute values of the two differences [ Dn-a ] and [ Dn-b ].

Thus, by means of the method and apparatus according to the invention, it is possible to continuously estimate the overall dimensions (in terms of average diameter) of the pipe T and its deformation with respect to an ideal circumference, thus allowing to inform in a precise manner the machines downstream of the extruder about the ongoing variation regime of the pipe produced in the production line, which requires it and allows it to know immediately whether and to what extent the pipe deviates from the expected theoretical cylindrical shape.

The advantages associated with the present invention are due to the fact that: for the purpose of evaluating the cross section of the pipe T, it is irrelevant whether the center E of the ellipse, and therefore the center of the pipe T, lies in the direction D1 passing through the origin O of the cartesian plane OXY.

In other words, the axis of the apparatus (indicated by the perpendicular to the plane OXY passing through O) may not be perfectly centred on the axis of the pipe T in transit, without this affecting the correct determination of the ellipse approximating the cross section of the pipe T, unlike the usual apparatuses which require perfect alignment between the axis of the pipe T and the axis of the apparatus for correct measurements.

Although less advantageous than the embodiments described above, alternative embodiments of the invention may include a mechanical contact member as a position detection device that is in physical contact with the surface of the pipe T in transit and whose relative position is measured with a linear or rotary potentiometer or encoder.

According to a variant embodiment of the invention (not illustrated), there are more than four distance-measuring sensors. More specifically, for example, the presence of five sensors allows to identify an ellipse in the cartesian plane OXY, even when it has no relative half-axes of the axes parallel to the cartesian plane.