阅读说明：本技术 用于监控用于运输挤压物料的加载有润滑剂的环绕的带的润滑状态的设备 (Device for monitoring the lubrication state of a circulating belt loaded with lubricant for transporting extruded material ) 是由 K·加尔茨 于 2020-02-26 设计创作，主要内容包括：本发明涉及一种用于监控用于运输挤压物料的加载有润滑剂的环绕的带(4)的润滑状态的设备和方法。此外,本发明涉及一种包括这样的监控设备的连续的压机以及用于运行这样的压机的方法。在此,在带(4)的区域中设有一个或多个传感器(9),利用所述传感器能产生与带(4)上的润滑剂量有关的至少一个测量信号(M)。按照本发明,所述传感器(9)构成为电容式工作的传感器,所述传感器分别具有与所述带(4)间隔开距离地设置的至少一个感应板(10),所述感应板与带(4)分别形成电容器(11),所述电容器的电容与设置在带(4)上的润滑剂量有关。(The invention relates to a device and a method for monitoring the lubrication state of a circulating belt (4) loaded with lubricant for transporting extruded material. The invention further relates to a continuous press comprising such a monitoring device and to a method for operating such a press. One or more sensors (9) are provided in the region of the belt (4), with which at least one measurement signal (M) can be generated, which is dependent on the amount of lubricant on the belt (4). According to the invention, the sensors (9) are designed as capacitive sensors, each having at least one sensor plate (10) which is arranged at a distance from the belt (4) and which forms a capacitor (11) with the belt (4), the capacitance of said capacitor being dependent on the amount of lubricant arranged on the belt (4).)

1. In particular in a continuously operating press (1), for monitoring the lubrication state of a circulating belt (4) loaded with lubricant for transporting extruded material,

comprising one or more sensors (9) arranged in the region of the belt, with which at least one measurement signal (M) relating to the amount of lubricant on the belt (4) can be generated,

it is characterized in that the preparation method is characterized in that,

the sensors (9) are designed as capacitive sensors, each having at least one sensor plate (10) which is arranged at a distance from the belt (4) and forms a capacitor (11) with the belt (4), the capacitance of the capacitor being dependent on the amount of lubricant arranged on the belt (4).

2. Device according to claim 1, characterized in that a plurality of sensor plates (10) are arranged side by side over the width of the belt (4), which sensor plates form a plurality of capacitors (11) arranged side by side with the belt, which capacitors are assigned to different width positions of the belt (4).

3. The device according to claim 1 or 2, characterized in that one or more sensor plates (10) are arranged movably relative to the belt (4) and/or in that one or more sensor plates (10) have an inlet edge which is formed at an angle or in a wedge-shaped manner.

4. Apparatus according to claim 2 or 3, characterized in that a plurality of sensor plates (10) are arranged one after the other in the direction of belt travel and offset from one another in the width direction in order to form a width-wise overlap of two adjacent sensor plates.

5. Apparatus according to one of claims 1 to 4, wherein the distance of the sensing plate or plates from the belt is less than 50mm, for example 2mm to 40mm, preferably 2mm to 30mm, particularly preferably 5mm to 25 mm.

6. Device according to one of claims 1 to 5, characterized in that the one or the plurality of sensors (9) each have an (electrical) circuit arrangement (10) which is connected to the sensor board (10) or integrated into the sensor board (10) and with which a measuring signal (M) can be generated which is dependent on the quantity of lubricant.

7. Device according to claim 6, characterized in that the circuit arrangement (12) is designed as an electrical circuit arrangement, by means of which the displacement current and/or the charge carrier compensation between the sensor plate and the strip can be measured.

8. Device according to claim 7, characterized in that the circuit arrangement (12) is designed as a resonant circuit (LC oscillator) having a capacitor (11) and additionally a coil (13), the frequency of which resonant circuit as the measurement signal (M) is dependent on the capacitance of the capacitor (11) and thus on the amount of lubricant provided within the capacitor (11).

9. Device according to one of claims 1 to 8, characterized in that the one or the plurality of sensors (9) are connected to or provided with one or more evaluation means (15), such as a filter circuit, by means of which an information signal (S) which is dependent on the measurement signal (M) and which is representative of the lubrication state can be generated by evaluating the measurement signal (M).

10. Device according to claim 9, characterized in that in the one or the plurality of analysis means (15) the measurement signal (M) is compared with one or more comparison values or with a comparison interval and that an information signal (S) can be generated depending on the comparison result, for example in the case of exceeding or falling below the comparison values or the comparison interval.

11. Device according to one of claims 1 to 10, characterized in that the one or more measurement signals (M) or the one or more information signals (S) can be transmitted to at least one reporting means (16) or a control means, with which reporting means (16) for example deviations from a predetermined lubrication state can be displayed or with which control means for example application means (8, 8') for the lubricant can be controlled.

12. The apparatus according to one of claims 1 to 11, characterized in that the belt is provided with a coating device (8, 8 ') with which a lubricant can be applied, preferably width-selectively applied, to the belt (4), preferably with which the coating device (8, 8') can be controlled by a control device on the basis of one or more measurement signals (M) or one or more information signals (S).

13. An apparatus according to one of claims 1 to 12, characterized in that the belt (4) is guided around one or more guide rolls (17), the sensor plates (10) being arranged in the region of the guide rolls (17) or of the support rolls supporting the belt.

14. Method for monitoring the lubrication state of a circulating belt (4) loaded with lubricant, in particular using a device according to one of claims 1 to 13,

generating at least one measurement signal (M) related to the amount of lubricant on the belt (4) by means of one or more sensors (9) arranged in the area of the belt,

characterized in that a measurement signal (M) relating to the quantity of lubricant is generated by means of one or more capacitive sensors (9) and the lubrication state is determined therefrom or a deviation of the lubrication state from one or more comparison values or from a comparison interval is determined.

15. Method according to claim 14, characterized in that an information signal (S) comprising information representative of the lubrication state is generated from the measurement signal (M) by means of the analysis device (15), said information being transmitted, for example, to the reporting device (16) or to the control device.

16. A method according to claim 14 or 15, characterized in that the lubrication state of the belt (4) is monitored selectively for a plurality of individual width position widths of the belt (4) by means of a plurality of sensors (9) distributed side by side over the width of the belt (4).

17. Method according to one of claims 14 to 16, characterized in that the application device (8, 8') for applying lubricant onto the strip (4) is controlled or regulated by means of a control device on the basis of the measurement signal (M) or the information signal (S).

18. A continuously operating press (1) comprising an upper continuously circulating belt (4) and a lower continuously circulating belt (4),

the extrusion material is guided through an extrusion gap between an upper belt and a lower belt (4) and is pressed using pressure and/or heat into a plate or a continuous plate belt,

and at least one application device (8, 8') with which a lubricant can be applied directly or indirectly to the upper belt (4) and/or the lower belt (4),

characterized in that the press (1) is equipped with a device for monitoring the lubrication status according to one of claims 1 to 13.

19. Method for operating a press according to claim 18, characterized in that the lubrication state of the press is monitored by means of a method according to one of claims 14 to 17.

Technical Field

The invention relates to a device for monitoring the lubrication state of a circulating belt loaded with lubricant for transporting extruded material, in particular in a continuously operating or continuously operable press, comprising one or more sensors arranged in the region of the belt, by means of which at least one measurement signal can be generated which is dependent on the amount of lubricant on the belt.

The invention further relates to a method for monitoring the lubrication state of a circulating belt loaded with lubricant, in particular in a continuously operating press.

The invention further relates to a continuous press comprising an upper continuous circulating belt or press belt and a lower continuous circulating belt or press belt, wherein the press material is guided through a press gap between the upper belt and the lower belt and is pressed using pressure and/or heat to form a plate or a continuous plate strip. The continuously circulating belt of such a press is also referred to as an extrusion belt and is preferably designed as a steel belt.

Finally, the invention relates to a method for operating a continuously operating press.

Background

Preferably, such a continuously operable press is a double belt press, wherein an upper (heatable) press plate is provided in the upper press part and a lower (heatable) press plate is provided in the lower press part, and the continuously circulating upper press belt is guided in the upper press part and the continuously circulating lower press belt is guided in the lower press part. The press belt is preferably supported on the press plate with the interposition of rolling elements, for example, rollers or roller shafts. The required pressing force is applied by means of a force mechanism, in particular a hydraulic compression cylinder, with which, for example, the upper and/or lower press platen is acted upon and which is supported on the press frame, for example, a press frame of the press frame. The stick is connected, for example, to a stick chain and is guided in a circulating manner by means of such a stick chain.

Such presses, also referred to as continuously operating presses, are used, for example, for producing wood material boards. Wood material boards are especially referred to as fibre boards, particle boards or OSB boards. Alternatively, however, the invention also relates to such a press for producing composite plates or composite components (for example from fiber composite materials or the like) or also for producing plastic plates or plastic mats.

The press material (e.g. a press material mat) is pressed between the circulating steel or press belts in the press gap of a continuously operating press using pressure and heat, so that, for example, plate-shaped products, such as wood material plates, are produced from the press material. The roller bars roll on the pressure plate as a rolling element assembly. Due to usual manufacturing tolerances or minimal deviations of the stick shape from a perfect cylinder, stroke or length differences on the two outer ends of the stick may occur during the rolling movement, which are compensated by micro-sliding. Against this background, it is generally necessary in practice and technically for the cylindrical surface of the stick or stick and/or the corresponding surface of the surrounding band to be lubricated with a lubricant. Such a lubricant is preferably designed as a liquid lubricant (e.g., oil) and is applied, for example, sprayed, onto the stick and/or the press belt, in practice, for example, by means of nozzles or the like in the inlet region or in the periphery of the stick. Accordingly, the (inner) surface of the continuously circulating belt facing the roller bars is loaded with lubricant and, more precisely, either directly (e.g. by spraying the belt surface) or indirectly through the roller bars loaded with lubricant (e.g. sprayed).

In order to operate a continuously operable press perfectly, perfect lubrication is particularly important, wherein inadequate lubrication and excessive lubrication should generally be prevented. In practice, it is therefore provided to monitor the lubrication state or the amount of lubricant or oil applied by spraying, and more precisely to monitor it manually or visually, usually by service personnel, on the basis of empirical values. It should be noted here that the amount of lubricant applied to the belt surface for lubrication is distributed uniformly and that no areas are created where the lubrication is insufficiently distributed due to lack of lubricant, e.g. lack of oil. In principle, these simple measures have proven to be feasible in practice. There is however a need to optimize and in particular automate the monitoring. In particular, there is therefore a need to design a reliable and quantifiable monitoring in order to reliably prevent inadequate lubrication on the one hand and to keep the lubricant consumption within the necessary limits, for example for economic reasons, on the other hand.

Continuously operating presses comprising associated lubricating systems are known, for example, from DE 3148412 a1, DE 4015706 a1 and DE 4126717C 1.

Furthermore, DE 102016102931B 4 discloses a device for monitoring and/or regulating the lubrication state in a continuously operating press, in which one or more sensors are provided for measuring physical phenomena related to the amount of lubricant on the belt. For this purpose, an evaluation unit is provided for determining the lubrication parameter as a characteristic parameter of the amount of lubricant on the belt on the basis of the measured values of the sensors. The sensor can be, for example, a light sensor for measuring light reflection values of the belt and/or the roller bar or a light sensor for measuring light absorption values of the belt and/or the roller bar of the press. Alternatively, a conductivity sensor, a laser distance sensor, or an ultrasonic sensor may be used. Furthermore, pressure sensors, tension sensors, power sensors and/or force sensors are mentioned. A controllable lubricating unit for applying the lubricant should be provided, which lubricating unit is designed with an adjusting device for adjusting the amount of lubricant to be applied by the lubricating unit on the basis of the determined lubricating parameter.

Disclosure of Invention

Based on the prior art known in the prior art, the object of the present invention is to provide a device and a method with which the lubrication state of a circulating belt can be monitored particularly reliably in a simple manner, in particular in a continuously operating press.

In order to achieve this object, the invention teaches in a device of the generic type mentioned at the outset that the sensor or the sensors are designed as capacitively operating sensors, each having at least one sensor plate (made of an electrically conductive material, for example metal) which is arranged at a distance (parallel) from the belt and which forms a capacitor with the (electrically conductive and, for example, grounded) belt, the capacitance of the capacitor being dependent on the amount of lubricant arranged on the belt (between the sensor plate and the belt).

The invention is based on the finding that the lubrication state of the press or the amount of lubricant present on the belt surface can be monitored or determined particularly easily and reliably by means of capacitive means, and more precisely by including an electrically conductive belt, for example a steel belt. The strip may be made entirely of an electrically conductive material, for example steel. Alternatively, however, it is also possible to use a belt which is (only) provided with an electrically conductive surface, wherein it is in principle sufficient for the belt surface (wetted with the lubricant) to be electrically conductive. One or more sensing plates are arranged at a predetermined fixed distance from the belt, so that they form a capacitor with the belt, the capacitance of which is sensitively influenced by the dielectric action of a lubricant, for example oil. Since the dielectric constant or relative dielectric constant of a lubricant, such as oil, is of a value of about 2, it differs very significantly from the dielectric constant of air of a value of about 1. Because based on the relation C ═ ε x ε_rxA/d, which is linearly contained in the capacitance of the plate capacitor formed by the sensing plate and the band, the capacitance of the capacitor formed in this way with the band (e.g. the compression band of a continuous press) is a sensitive and reliable measure for the amount of lubricant provided on the band and hence within the plate capacitor.

Although capacitive sensors which operate on the basis of a change in capacitance of a capacitor are known from the prior art, they are used, for example, as pressure sensors, distance sensors, proximity switches, gap sensors, travel sensors or also as humidity sensors. However, such a technique has not been considered until now for use in continuous presses and in particular for monitoring the lubrication state of a circulating belt loaded with lubricant.

According to the invention, it is possible in a particularly advantageous manner to analyze or monitor the lubrication state of the belt selectively or individually over the width of the belt, so that not only the lubrication state, which is averaged over the width, but in particular also an uneven distribution over the width can be detected. In a preferred further development of the invention, provision is made for a plurality of sensor plates to be arranged next to one another over the width of the strip, which sensor plates form a plurality of capacitors next to one another, which capacitors are each assigned to different width positions of the strip. In this case, for example, it is possible to implement at least five sensor plates and thus five capacitors across the width of the strip, so that the lubrication state can be monitored in five tracks arranged next to one another. By means of the division and the number of the tracks, an adaptation to the respective given conditions can be carried out, and more precisely in such a way that a fine or selective monitoring of the band over the bandwidth can be achieved by means of a high number of tracks.

Of interest is the fact that belts, for example press belts of continuous presses, are usually produced from an electrically conductive material (for example as steel belts) and such belts are usually grounded, so that one or more capacitors can be realized with the induction plates in a simple manner for capacitive lubricant monitoring. In principle, however, it is also possible to use a circumferential band or extruded band which is not made completely of an electrically conductive material, but only has an electrically conductive band wetted with a lubricant.

Alternatively, it is possible for one or more sensor plates to be arranged movably relative to the belt, and more precisely preferably in a direction extending transversely to the plate plane. In this case, the sensor plate can be in a working position (which defines a desired distance from the belt) in normal operation and can be displaced from the working position into an offset position (which increases the distance from the belt) during operation, for example when an object is present on the belt surface. Interference and/or damage can thereby be reliably avoided, for example when objects are undesirably present on the belt and/or when a large number of interfering particles, for example wood-based materials, are present on the belt. In this case, the plate can be displaced from the theoretical position and thus from the operating position, and more precisely in a displacement direction oriented transversely to the plate plane. In addition, it can be advantageous if the sensor plate is loaded by a force, for example by a spring force, in the operating position and thus in the theoretical position, so that the plate is displaced by the interfering body counter to the force, for example the spring force, and then automatically again reaches the operating position, in order to ensure a desired and predetermined plate distance that avoids measurement errors in normal operation.

In particular, in the embodiment with movable sensor plates, it can be advantageous if one or more sensor plates have an angled or wedge-shaped entry edge, and more precisely on the edge of the entry side of the sensor plate which is arranged opposite to the circumferential direction, so that a wedge-shaped entry gap which tapers in the direction of travel is produced between the sensor plate and the belt in the region of one or more sensor plates. This can be achieved, for example, by the respective sensor plate being simply chamfered in the inlet region or on the inlet edge and thus having an inlet chamfer. Alternatively, angled or curved entry regions of the sensor plate may be used. Such a design, which comprises an angled or wedge-shaped entry edge, is advantageous in particular in connection with the movable sensor plate, since in this way the deflection of the sensor plate is simplified and thus interference is prevented.

In particular in the case of movable and thus displaceable sensor plates, it can be advantageous if the displacement from the operating position of the sensor plate can be detected directly or indirectly by a control unit or by the control unit. In this way, by means of the assignable belt position and/or in the case of a calculation of the speed of the belt around, a targeted discharge of the objects detected in conjunction with the deflection of the sensor plate can be initiated.

It is also advantageous here for the sensor plates to be arranged in the region of the press belt, in such a way that the press belt is subjected to as little positional fluctuations as possible, so that the capacitor gap does not change or does not change appreciably. For this purpose, it may be expedient to arrange the sensor plate in the region of a roller in the press, for example in the region of a guide roller or in the region of a support roller which is present for the belt in the press. There is also the possibility of providing separate support rollers and of arranging the sensor plates in the region of these support rollers. For this purpose, the sensor plates can be designed in an arched manner according to the course of the strip around the respective roller and according to the desired distance from the strip. However, depending on the thickness of the strip, the preferred region can also begin or end up to 500mm or even up to 1500mm before or after the nip formed by the strip and the roll.

According to a further, optionally implementable concept of the invention, a plurality of sensor plates can be arranged one after the other in the direction of belt travel and offset from one another in the width direction in order to form an overlap with respect to the width position. Thus, at least two sensor plates are arranged one above the other, viewed over the width of the strip. For this purpose, one of the sensor plates can be arranged so as to be moved forward or backward relative to the other sensor plate in the direction of belt rotation. It is advantageous here for the sensor plate to have a triangular or trapezoidal area on its side facing the belt.

From the relationship already described it can be derived that if d is small and a is large, it can be advantageous for measuring thin lubricating film thicknesses for obtaining as accurate a measurement result as possible. Experiments have shown that the ratio of the area to the distance, which is formed as a dimensionless value, lies between 100 and 10000, in particular between 500 and 5000, preferably between 1000 and 4000.

In principle, it is advantageous if the distance d between the belt and the sensor plate is not more than 50mm and, depending on the application, is preferably designed in the range between 2mm and 30mm, in particular in the range between 5mm and 25 mm.

In a preferred further development, it is provided that the sensor or sensors (respectively) have (electronic) circuit arrangements which are connected to the respective sensor board or in which the sensor board is integrated and with which a measuring signal dependent on the quantity of lubricant can be generated. The components of the sensor are thus not only the capacitor itself, but also an electronic circuit arrangement in which, however, known measures can be used to wire the capacitor or the capacitor plates during the capacitive measurement. The circuit arrangement can thus be, for example, an electronic resonant circuit and thus an LC oscillator, which is formed on one side by at least the capacitor (including the sensor plate and the strip) and on the other side by an additional coil, wherein the frequency of the resonant circuit or the oscillator as a measurement signal is dependent on the capacitance of the capacitor and thus on the amount of lubricant provided in the capacitor. Thus, the change in capacitance due to the electrical effect of the oil can be detected in the form of a change in the frequency of the LC oscillator, which changes when the amount of oil between the plate and the belt becomes smaller or larger, e.g., smaller or larger than the desired amount of oil. The lubricant-or oil-dependent capacitor according to the invention therefore serves as a frequency-influencing element in the LC oscillator and therefore as a frequency-determining component. As soon as the oil quantity changes, the frequency also changes.

The sensor or sensors can be connected to or equipped with an (common) or with a plurality of (individual) evaluation devices, by means of which, by evaluating the measurement signals, information signals can be generated which are dependent on the measurement signals and which represent the lubrication state. For this purpose, the measurement signal can be compared, for example, in the one or more evaluation devices with one or more comparison values or with one or more comparison intervals, wherein an information signal can be generated by comparing the measurement signal with the one or more comparison values or comparison intervals, for example when the comparison value or comparison interval is exceeded or undershot. Such an evaluation device can be realized very simply in terms of circuitry, for example, by a filter circuit known in principle, which generates an information signal in the presence of a corresponding deviation, which information signal can be transmitted, for example, to a reporting device.

It goes without saying that, on the one hand, the circuit arrangement of the sensor (into which the capacitor is integrated) and the evaluation device (for example, a filter circuit) connected to the circuit arrangement can be combined in circuit terms in a common device or in a common circuit. Alternatively, however, it is also possible to provide a common evaluation device for a plurality of sensors, each equipped with a circuit arrangement, which may also be integrated into a computer, for example. The same applies to optionally provided reporting devices, which may be designed in terms of component technology together with the analysis device or may be formed by separate units or, if appropriate, also by a computer, for example a central computer.

As an alternative to this circuit arrangement in the form of an LC oscillator, it is also possible to use further circuit arrangements known in principle, for example PLL (phase locked loop) circuits.

There is the possibility of transmitting a measurement signal (e.g. frequency) or in particular an information signal resulting therefrom (e.g. below the lubrication specification) to at least one reporting device or reporting system. The reporting system can be used, for example, for the visual and/or acoustic display of defective lubrication, for example, by generating a warning message on the basis of an information signal representing excessive lubrication or insufficient lubrication. Based on such warning messages, the operator can intervene in the process, for example. Alternatively, however, there is also the possibility of automated reactions in the sense of control or regulation. In this case, for example, it is possible to connect the circuit arrangement and/or an evaluation device, which is preferably connected to the circuit arrangement, to a (common) control device, with which the lubrication process can be automatically influenced as a function of the measurement signals or information signals, and more particularly preferably in the sense of control or regulation.

Since the device according to the invention for monitoring the lubrication state preferably has not only the monitoring device but also at least one application device with which the lubricant can be applied to the strip, and more precisely either directly or indirectly (for example via a circulating roller bar). Such a coating device can be, for example, a spray coating device known in principle for liquid lubricants (e.g. oil). In particular, such a coating device is preferably designed for the width-selective application of a strip, so that a defined width region can be applied with different amounts of lubricating material in a targeted manner by means of the coating device. It is thus possible to connect the control device to the application device, so that with the application device, the control or regulation of the application of lubricant can take place taking into account the determined measurement or information signal. Particularly preferably, this is also effected width-selectively. If, for example, a sensor is used to determine that there is insufficient or excessive lubrication in a defined width region (i.e. the track) of the belt, the control device can automatically influence the application device and the lubricant profile over the width.

The invention also relates to a device for monitoring the lubrication state, and to a corresponding method for monitoring the lubrication state, which is preferably carried out using a device of the type described. The method is characterized in that a measurement signal relating to the quantity of lubricant is generated by means of the one or the plurality of capacitive sensors and the lubrication state or the deviation of the lubrication state from one or more comparison values is determined therefrom. From the measurement signal, the evaluation device can generate an information signal, which contains information representing the lubrication state, for example, in the described manner, for example, by transmitting said information to a reporting device and/or a control device. In this way, it is possible to control or regulate the application device for applying the lubricant to the strip by means of the control device as a function of the measurement signal or the information signal. In the described manner, the lubrication state of the belt can be selectively monitored for a plurality of individual width positions of the belt by means of a plurality of sensors distributed side by side over the width of the belt.

The invention also relates to a continuously operating press having at least one upper continuously circulating belt (press belt) and a lower continuously circulating belt (press belt), wherein the press material is guided through a press gap between the upper belt and the lower belt. Preferably, the invention relates to an extrusion device in which the extrusion material is pressed into a plate or a continuous plate strip using pressure and/or heat. Alternatively, such a press can also be a preheating device, which is used, for example, in a continuous extrusion process for preheating the extrusion material, which is then introduced into the continuously operating press for producing the actual plate. Such a continuously operating press is preferably tested in the manner of a double belt press, in which the press belt is supported on the respective press plate with the interposition of rolling elements, for example roller bars or rods. However, the invention alternatively also relates to a press of another type of construction, for example a calender press, comprising a circulating press belt. Such presses are always equipped with devices for monitoring the lubrication state of the type in question, i.e. the description of the lubrication and monitoring bands preferably relates in the press to the respective upper and/or the respective lower press band. The technical solutions of such presses are also usually coating devices with which a lubricant can be applied (directly or indirectly) to the upper and/or lower belt. The press according to the invention is therefore characterized in that it is equipped with a device for monitoring the lubrication state of the type in question.

In a corresponding manner, the invention finally also relates to a method for operating such a press, wherein the method is characterized in that the lubrication state is monitored by means of one or more capacitive sensors of the type described.

Drawings

The invention is explained in more detail below with the aid of the drawings, which show only one exemplary embodiment. In the figure:

fig. 1 schematically and in a simplified manner shows a continuously operating press, which comprises a device for monitoring the lubrication state of the press belt,

fig. 2 schematically shows a simplified illustration of a device for monitoring the lubrication state in the press according to fig. 1, and

fig. 3 shows a circuit arrangement of the device according to fig. 2.

Detailed Description

Fig. 1 shows a continuously operating press 1 which is suitable and intended, for example, for pressing mats of press material into press material boards in the production of chipboards, fibre boards or other wood-based material boards. The continuous press 1 has in its basic configuration an upper press part with an upper heatable press plate 2 and a lower press part with a lower heatable press plate 3. The heatable press plates 2, 3 are also referred to as heating plates. A continuously circulating belt 4, which is also referred to as a press belt 4 (or simply belt 4) and is made of steel, for example, is guided in the upper press part and in the lower press part. Between the press belts 4, a press gap P is formed, through which the press material is guided. The press belt 4 is supported on the press plates 2, 3 with the interposition of a stick or roller 5. The rods 5 are guided here, for example, on a rod chain, which is not shown in detail. The press material is pressed in a press using pressure and heat to form a strip of strip which is discharged from the press. The pressing force required for this purpose is applied by means of a force mechanism, in particular by means of a hydraulic compression cylinder 7, to which the upper pressing plate 2 or the lower pressing plate 3 is, for example, loaded. The compression cylinder 7 is supported on a press frame 6 of a press frame, for example a press frame. Fig. 1 shows here, by way of example only, an upper piston press in which the upper press plate 2 is loaded with a compression cylinder 7.

The press belt is loaded with a lubricant, in particular a liquid lubricant, for example oil. Fig. 1 shows the possibility of directly applying lubricant to the respective press belt, for example by means of a suitable application device 8, which may be designed, for example, as a spray device extending across the belt width transversely to the direction of belt travel. Alternatively or additionally, however, a coating device 8', which is also shown in fig. 1, can be provided, which applies a lubricant to the revolving roller bar 5, so that the press belt is indirectly acted on by the roller bar. Fig. 1 shows only the lubrication of the upper belt. It goes without saying that corresponding measures are also provided in the region of the lower belt. The "inner" surface of the respective press belt 4 facing away from the press material is always loaded.

The press 1 is equipped with a device for monitoring the lubrication state of the circulating belt loaded with lubricant. The apparatus is shown in fig. 2. The device has a plurality of sensors 9 which are arranged in the region of the belt and are distributed over the belt width and with which at least one measurement signal M is generated in each case in relation to the respective amount of lubricant on the belt. According to the invention, these sensors 9 are designed as capacitive sensors, each having at least one sensor plate 10, which is arranged at a distance from the belt 4 and forms a capacitor 11 with the belt 4, the capacitance of which depends on the amount of lubricant arranged on the belt. In this case, fig. 2 shows that a plurality of sensor plates 10 are arranged next to one another over the width of the strip 4, which together with the strip form a plurality of capacitors 11 arranged next to one another, which are assigned to different width positions of the strip. In the illustrated embodiment, five sensor plates 10 and thus five sensors are shown arranged side by side, so that the lubrication state on the belt can be monitored in five separate tracks. The sensing plate 10 is arranged spaced apart from the belt 4 by a distance d.

The sensors 9 each have a circuit arrangement 12 which is connected to the respective sensor board 10 or into which the respective sensor board 10 is integrated (see, for example, fig. 3). With this circuit arrangement 12, a measuring signal M relating to the amount of lubricant can be generated (for the respective width position). In the exemplary embodiment shown, the circuit arrangement 12, which has the capacitor 11 on the one hand and the coil 13 on the other hand, is designed as a resonant circuit and thus as an LC oscillator. Fig. 3 shows a variant in which a basic resonant circuit is initially provided, which comprises a coil 13 and a directly associated capacitor 11 ', which is connected in parallel with the capacitor 11 formed by the sensor plate 10 and the strip 4, so that the capacitances 11 and 11' add up. Furthermore, an amplifier 14 comprising an input E and an output a and an impedance R are shown. The output of the circuit arrangement 12 according to fig. 3 provides a frequency signal as a measurement signal, i.e. the frequency of the resonant circuit is dependent on the capacitance of the capacitor 11 and thus on the amount of lubricant provided on the belt 4 within the capacitor 11. When the amount of oil between the plate and the belt becomes smaller or larger, the frequency of the oscillator changes accordingly. The lubricant-dependent capacitor 11 thus serves as a frequency-determining component in the LC oscillator, so that said frequency serves as the measuring signal M.

The sensor 9 (or the circuit 12 of the sensor) is connected to one or more evaluation devices 15, which are embodied in this exemplary embodiment as filter circuits 15. The filter circuits are shown schematically and in a simplified manner in the figure as individual components, but it goes without saying that they can also be combined with one another and/or with the circuit 12 in terms of circuitry. By evaluating the measurement signals, the evaluation device 15 generates an information signal S, which is dependent on the measurement signal M and which represents the lubrication state. For this purpose, the evaluation device 15 can compare the measurement signal M with one or more comparison values or with a comparison interval, respectively, and depending on the result of the comparison, for example if the comparison value or the comparison interval is exceeded or undershot, the information signal S can be generated. This makes it possible, for example, for an information signal S to be generated and transmitted to the reporting device 16 when an insufficient or excessive lubrication is determined for the respective width position. The information signal can be realized in circuitry technology, for example by a filter circuit, i.e. the information signal is generated when the measured frequency deviates from a predetermined frequency or leaves a predetermined frequency range. In this case, a simple variant is shown in the figures, in which a report or a visual and/or acoustic warning signal is generated by the reporting device 16, for example, which the operator can react to when operating the press.

Alternatively, however, it is also possible to combine the device with a control device or to supply the measurement signal M or the information signal S to a control device, with which, for example, the application devices 8, 8' for applying lubricant to the press belt 4 can be controlled or regulated. If necessary, a closed-loop control loop can be implemented. There is always the possibility of automatically controlling or regulating the lubricant application as a function of the monitoring result generated with the measuring device.

It is also advantageous here for the sensor plates 10 to be arranged in the region of the press belt in which the press belt is subjected to as little positional fluctuations as possible, so that the capacitor gap does not change or does not change appreciably. For this purpose, it may be expedient to arrange the sensor plate in the region of a roller within the press, for example in the region of a guide roller or in the region of a support roller which is present for the belt in the press. There is also the possibility of providing separate support rollers and of arranging the sensor plates in the region of these support rollers. Details are not shown.

Furthermore, in the exemplary embodiment described, the sensor plate 10 is arranged at a fixed predetermined or fixed defined distance d from the strip 4. Alternatively, it is possible that the defined distance d relates to a theoretical or operating position of the sensor plates, and that these sensor plates, starting from this operating position, can be moved in a transverse direction oriented transversely to the plate plane or strip plane and can therefore be displaced, so that the plates, for example in the presence of interfering bodies, impurities or the like, can be displaced, for example, against the force of a spring or the like, in order to enlarge the gap, so that the sensor plates then automatically come into the operating position with the defined gap d. Details are not shown in the figures.