Chain assembly and methods for its operation

Abstract

Chain assembly (1) for driving workpieces along a machining path, comprising - a drive head (2) with a sprocket (3) that can be rotated about a pivot axis (6), - a deflection head (4) with a deflection wheel (5) rotatable about a pivot axis (7), - a self-contained chain (8) spanning the sprocket (3) and the deflection wheel (5), - a tensioning system (9) for tensioning the chain (8), wherein the sprocket (3) can be driven by means of a rotary drive, so that the chain (8) runs around the sprocket (3) and the deflection wheel (5), the clamping system (9) comprising - at least one clamping element (10), - at least one adjusting element (11) for setting a clamping force of the clamping element (10), - a support (12) against which the clamping element (10) is supported at its first end (13), - a transmission device (15) against which the clamping element (10) is supported at its second end (14), - at least two guide axes (16, 17) connected to the transmission device (15) and extending parallel to each other, wherein the clamping force introduced into the transmission device (15) as a result of the support of the second end (14) of the clamping element (10) can be transferred to the two guide axes (16, 17) by means of the transmission device (15), wherein the sprocket (3) or the deflection wheel (5) is mounted directly or indirectly by means of the guide axes (16, 17) so that the sprocket (3) or the deflection wheel (5) can be pressed against the chain (8) by means of the clamping force of the clamping element (10) and thereby the chain (8) can be tensioned with a chain tension, characterized by a strain measuring device (18) which is arranged on the transmission device (15) in such a way that it is designed to record information concerning a deformation of the transmission device (15) which occurs as a result of the action of the clamping force and its transmission towards the guide axes (16, 17).

Description

[0001] The present application relates to a chain unit for advancing workpieces along a processing path according to the preamble of claim 1. Furthermore, the present application relates to a method for operating a chain unit according to the preamble of claim 13.

[0002] A chain unit according to the present application can be used in particular in a so-called "double-end tenoner." In a double-end tenoner, several chain units, usually two chain units arranged in pairs and oriented parallel to each other, are typically used together to move workpieces along the processing line. If multiple chain units are used, they are generally oriented parallel to each other. Other devices can also use one or more chain units to transport workpieces along a processing line.

[0003] A characteristic of the double-end tenoner is that the transported workpieces can be machined along several sides simultaneously, for example along opposite lateral edges of the respective workpiece. Accordingly, it is particularly important for the feed of the workpieces that they do not twist about a vertical axis during their movement along the processing path. If multiple chain units are used, it is therefore essential that the chain units run exactly synchronously, since a (minimal) deviation between the speeds of the chain units would inevitably lead to a twisting of a workpiece mounted on both chain units about a vertical axis, which would make it impossible to machine the lateral edges of the respective workpiece, or at least not with sufficient quality.

[0004] The chain unit comprises a drive head with a sprocket that can be driven for rotation about a rotational axis. The sprocket can be driven for rotation, for example, by an electric motor, wherein the electric motor can interact with a control device that controls the operation of the electric motor and thus of the sprocket. The chain unit further comprises a deflection head that includes a deflection wheel that can be rotated about a rotational axis. The deflection wheel is generally passive, meaning that it cannot be actively driven as such. The sprocket and the deflection wheel are preferably arranged opposite one another and thus define two opposite ends of the chain unit. Typically, the chain unit does not comprise any further wheels besides the sprocket and the deflection wheel, although this is conceivable in principle.The most common case is that the sprocket and idler wheel form two opposite ends of the chain unit, and a chain circulates around the sprocket and idler wheel. The chain unit is typically horizontally oriented, with the rotational axes of the sprocket and idler wheel located in a horizontally oriented plane. A chain unit oriented in this way is used to transport workpieces along a horizontal processing path using the chain.

[0005] The chain of the chain unit is self-contained or endless and spans the sprocket and the idler pulley. The chain can, for example, be profiled on its underside so that it can interact with the sprocket and / or the idler pulley as intended. In particular, the underside of the chain can be designed to match the sprocket so that torque can be transferred from the sprocket to the chain and the chain can thereby be driven. Alternatively or additionally, it is conceivable for form-locking means, for example in the form of bolts, to protrude from the side of the chain, which are gripped on the sprocket and / or idler pulley to create a form-lock and thus ensure a flow of force between the chain and the sprocket or idler pulley. Other variants are also conceivable and known per se.Furthermore, an outer upper side of the chain can be designed with a profile and / or form-locking elements that are intended and configured to engage with workpieces so that they rest securely on the chain. It can be particularly important here to prevent unintentional relative movements between the workpiece and the chain during transport of a workpiece. In particular, the chain can be equipped with upwardly projecting cams or the like on its upper side.

[0006] The chain unit further comprises a tensioning system by means of which the chain can be tensioned or kept under tension. The tensioning system comprises at least one tensioning element, at least one adjusting element for adjusting a tensioning force of the tensioning element, an abutment against which the tensioning element rests at its first end, a transmission device against which the tensioning element rests at its second end, and at least two guide axes connected to the transmission device and extending parallel to one another. The tensioning element can in particular be formed by a spring element, which is formed, for example, by a pre-tensioned compression spring. The abutment merely serves to provide support for the tensioning element. The tensioning force is exerted as intended in the direction of the transmission device, against which the tensioning element rests with its opposite second end.

[0007] The transmission device can, for example, be formed by a plate made of steel, for example. From there, the tensioning force is transmitted directly or indirectly to the guide axles and finally, via the guide axles, to the sprocket or idler pulley, so that the sprocket or idler pulley is pressed outwards against the chain. Preferably, the transmission device is mounted exclusively by means of the guide axles, so that the tensioning force exerted by the tensioning element is completely diverted to the two guide axles. Connection points of the guide axles, at which the guide axles are connected to the transmission device, form supports for the transmission device, so that a force exerted on the transmission device (in particular the tensioning force of the tensioning element) is diverted to the connection points at which the guide axles form supports for the transmission device.It is preferred if the guide axes are arranged one above the other, i.e., extending together in a vertical plane. In this embodiment, the transmission device is preferably vertically oriented. The guide axes can be formed, for example, by elongated rods extending from the transmission device. In particular, ends facing away from the transmission device can interact with a linearly movable bearing device by means of which the sprocket or the idler wheel is mounted, depending on whether the tensioning device is operatively connected to the sprocket or the idler wheel. The bearing device can be formed, for example, by a plain bearing.

[0008] As a result of the tensioning force exerted by the tensioning element, the chain is tensioned. The higher the tensioning force of the tensioning element, the more tightly the chain is tensioned. Since the chain wheel is typically arranged in a fixed position for the purpose of interacting with a drive device, the tensioning system preferably interacts with the deflection wheel, which is preferably mounted for linear movement by means of a bearing device and is movable along a movement axis of the bearing device by means of the guide axes. The movement axis preferably extends parallel to the longitudinal axes of the guide axis and more preferably parallel to an axis of action of the tensioning element.

[0009] The adjusting element can be used to change the clamping force of the clamping element. For example, it is conceivable for the adjusting element to be formed by a nut, which either itself forms the abutment for the clamping element or by means of which the position of the abutment can be changed along an axis of action of the clamping element. An adjusting element designed as a nut can be moved axially particularly easily by rotating it about a screw axis along a threaded bolt on which the nut is mounted in a meshing manner, thereby displacing the abutment for the clamping element along an axis of the threaded bolt. The axis of action of the nut can, in particular, be oriented parallel to an axis of action of the clamping element.In particular, the adjusting element can be designed such that it is suitable for changing the distance between support points on which the clamping element rests with its two ends, thereby changing the clamping force acting in the clamping element. One support point is formed on the transmission device, and the other support point is formed on the abutment.

[0010] In practice, it is normal for the chain of the chain unit to lose tension over time, requiring adjustment of the chain tension using the tensioning system. If a certain chain tension is detected, the tensioning element can be re-tensioned by influencing the adjusting element, thereby increasing the tensioning force exerted by the tensioning element and consequently increasing the chain tension. State of the art

[0011] Double-end tenoners in which a chain unit in question could theoretically be used are known, for example, from the documents DE 10 2008 035 280 A1 and DE 10 2004 054 973 A1.

[0012] Chain units of the type described above are already known in the art. In particular, it is common practice for the chain tension to be checked and manually adjusted if necessary during routine maintenance of the respective chain unit.

[0013] This approach has the disadvantage that the chain tension drops so much before the next maintenance is due that a discrepancy occurs between the operation of the affected chain unit and a second chain unit on the same double-end tenoner. As explained above, this can lead to faulty machining of the workpieces. In the worst case, a large number of workpieces machined with the double-end tenoner over a processing period must be disposed of as scrap because the quality during the insertion of the respective profiles could not be maintained at the desired level due to an unintentional skew of the workpieces on the two chain units. Task

[0014] Accordingly, the object of the present application is to provide a chain unit whose operation is possible with a lower risk of faulty operation compared to the prior art. Solution

[0015] The underlying problem is solved according to the invention by means of a chain unit having the features of claim 1. Advantageous embodiments emerge from the associated subclaims.

[0016] The chain unit according to the invention is characterized by a strain gauge arranged on the transmission device. The strain gauge is designed and provided to detect information relating to a deformation of the transmission device. The transmission device deforms as a result of the tensioning force introduced into the transmission device by the tensioning element and transmitted to the two guide axes by means of the transmission device. The present invention follows the idea that a change in the chain tension is reflected in a change in the tensioning force of the tensioning element, which in turn leads to a change in the force acting on the transmission device. Such a change in the application of forces to the transmission device inevitably leads to a change in the deformation or deformation state of the transmission device.This change can be detected using the strain gauge. As a result, a change in chain tension can be detected by a change in the deformation of the transmission device or by a change in the measured values ​​of the strain gauge. Accordingly, the strain gauge provides a means of continuously (indirectly) monitoring the chain tension of the chain unit and, in the event of a change in chain tension, taking appropriate action to prevent faulty machining of workpieces. The strain gauge can, for example, operate according to the principle of resistance measurement, with deformations of the transmission device being detected by a change in the electrical resistance of a conductor of the strain gauge. This is the case, for example, if the strain gauge comprises at least one strain gauge.

[0017] The advantages of the chain unit according to the invention therefore lie in the ability to better monitor its operation and thus to detect and counteract any unplanned operating condition of the chain unit at an early stage, ideally preventively. A double-end tenoner equipped with such a chain unit is therefore subject to a significantly lower risk of potentially significant economic loss due to the rejection of a large number of workpieces.

[0018] In an advantageous embodiment, an effective axis of the clamping force of the clamping element is oriented parallel to the longitudinal axes of the guide axes. This has the advantage that the clamping force essentially only triggers normal forces in the guide axes, so that the guide axes remain free of transverse forces and thus bending moments. This is advantageous for the design of the guide axes and thus the entire clamping system.

[0019] Further elaborating on the chain unit, the connection points of the guide axes, where the guide axes are connected to the transmission device, are located on a rear side of the transmission device. The rear side of the transmission device refers to the side opposite a front side of the transmission device, with the front side of the transmission device describing the side where a support point is located, where the tensioning element rests on the transmission device. This support point allows the tensioning element to rest its second end on the transmission device, so that the tensioning force of the tensioning element is transmitted to the transmission device at the support point.In other words, the clamping element rests on the front side of the transmission device with its second end, while the guide axes are preferably connected to the opposite rear side of the transmission device. Therefore, in a static sense, the guide axes form supports for the transmission device at the connection points where the guide axes are connected to the transmission device, which are loaded with the clamping force exerted by the clamping element.

[0020] In a preferred embodiment, the transmission device acts statically like a beam mounted on two supports. In particular, the guide axes can be connected to opposite ends of the transmission device, while the tensioning element is supported on the transmission device in an area between the guide axes. The tensioning element is preferably supported at least substantially in the center of the field between the connection points of the guide axes, so that the tensioning force is diverted to the guide axes by means of the transmission device, at least substantially half to both guide axes. In cases where such an arrangement of the support point of the tensioning element is not possible, it is also conceivable for the support point to be located off-center rather than in the center of the field between the guide axes.This may be necessary, for example, if the installation space available for the clamping system requires off-center support of the clamping element on the transmission device.

[0021] Furthermore, a design of the chain unit in which the strain gauge is arranged on the rear side of the transmission device can be advantageous. Since, as explained above, the rear side is located opposite the front side of the transmission device, which in turn contains the support point for the tensioning element, a deflection of the transmission device towards the rear side of the transmission device can be expected as a result of a positive tensioning force (compressive force). Accordingly, tensile stresses can be expected to develop on the rear side, which cause a deformation of the transmission device at the rear in the form of stretching. Accordingly, it can be expected that, when the tensioning system is used as intended, the strain gauge arranged on the rear side of the transmission device will measure positive strains, i.e. stretches.The arrangement of the strain gauge at the rear of the transmission device has the advantage that it can be positioned independently of the support point for the clamping element, which is located at the front of the transmission device.

[0022] Particularly preferably, the strain gauge can be located in the center of the field between the connection points of the guide axes, since this is where the greatest bending moments and, consequently, the greatest deformations are generally expected. This has the advantage that the measured values ​​recorded by the strain gauge also have the greatest magnitude and are significantly above any measurement inaccuracies of the respective strain gauge. If, as explained above, the support point of the clamping element on the front of the transmission device is also located in the center of the field, it is particularly preferable if the strain gauge is located opposite the support point, i.e., along an axis of action of the clamping force of the clamping element on the rear of the transmission device.

[0023] In a further advantageous embodiment of the chain unit, the unit comprises an evaluation device that is connected to the strain gauge in a data-transmitting manner. For example, the evaluation device can be formed by a data processing system with a memory and a microprocessor for executing programs. The evaluation device is provided and configured to receive and process information acquired by the strain gauge. Corresponding information can be processed by the evaluation device to, for example, produce a graphic display for a machine operator.Additionally or alternatively, it is conceivable for the evaluation device to directly convert the measured values ​​of the strain gauge into the chain tension of the chain unit, allowing a machine operator of the chain unit to make a quantitative assessment of the chain tension. For example, this allows the machine operator to assess whether the displayed chain tension is within specified limits.

[0024] Accordingly, it can be particularly advantageous if the evaluation device is provided and configured to continuously evaluate the actual deformation of the transmission device and to use this to determine the effective tensioning force of the tensioning element at the time of the evaluation. In addition, it can be advantageous if the evaluation device is provided and configured to automatically send out information when the tensioning force of the chain falls below a predetermined minimum value. This assessment of the tensioning force can only be carried out implicitly, whereby the evaluation device effectively monitors not the tensioning force of the chain as such, but rather the actual deformation of the transmission device and continuously compares it, for example, with a predetermined minimum value. Furthermore, it is also conceivable that, in addition to checking at least one minimum value, a check concerning at least one maximum value also takes place.It is therefore conceivable that the chain tension could inadvertently increase, for example due to temperature changes, and exceed a technically favorable value. Such a check could also be measured using the strain gauge and processed by an evaluation device.

[0025] Furthermore, a particularly advantageous embodiment of the chain unit includes an actuator that interacts with the adjusting element. The actuator is designed and configured to act on the adjusting element, thereby changing the tensioning force of the tensioning element. Such an actuator allows the tensioning force of the tensioning element to be changed without requiring manual access to the adjusting element.

[0026] In a particularly advantageous embodiment, such an actuator can interact and be connected to an evaluation device described above as advantageous in a data-transmitting manner, wherein the evaluation device is provided and configured to control the actuator in order to influence the actuating element and thus the clamping force of the clamping element. In particular, if the clamping force of the clamping element falls below a predetermined minimum value, the evaluation device can control the actuator so that it adjusts the actuating element and thereby increases the clamping force of the clamping element. This increase is then reflected in a greater deformation of the transmission device, which in turn is detected by the strain gauge. The evaluation device can thereby conclude that the clamping force has increased, so that it is (again) above the minimum value.In this embodiment, the strain gauge, in conjunction with the evaluation device, the actuator, and the control element, forms a control system in which the deformation state of the transmission device represents the input variable measured by the strain gauge ("input device"). The information generated from this is sent to the evaluation device ("processing unit") and processed there, particularly in the form of a comparison of the input variable with a target variable. This results in an instruction for the actuator ("output device"), whose operation influences the input variable.

[0027] From a process engineering perspective, the underlying object is achieved according to the invention by means of a method having the features of claim 13. Advantageous embodiments emerge from the associated subclaims.

[0028] The method serves to operate a chain unit according to the present invention, which is correspondingly equipped with a strain gauge. According to the invention, the method provides that the strain gauge continuously records information relating to a deformation of the transmission device resulting from the action of the clamping force of the clamping element and the dissipation of this clamping force to the guide axes. The resulting advantages have already been explained above in connection with the chain unit. In particular, it creates the possibility of indirectly continuously monitoring the chain tension of the chain of the chain unit, thus preventing an unintentional drop in chain tension and the resulting damage to machined workpieces.

[0029] In a particularly advantageous embodiment of the method, the information acquired by the strain gauge is processed by an evaluation device. This enables automatic transmission of information when a preset minimum value for the tensioning force of the tensioning element (and thus for the chain tension) is detected. Based on this information, the respective machine operator can take measures that lead to an increase in the chain tension to a desired value. In particular, the machine operator has the option of changing the tensioning force of the tensioning element using the adjusting element and thus indirectly influencing the chain tension.

[0030] In a particularly preferred embodiment, this process can also be automated, with the evaluation device interacting with an actuator, which in turn interacts with the actuating element. According to the above explanation, the evaluation device is provided and configured to control the actuator, particularly when the minimum value for the tensioning force of the tensioning element is undershot. In this case, the actuator can adjust the actuating element in such a way that the tensioning force of the tensioning element is increased. This, in turn, leads to an increase in the chain tension of the chain of the chain unit. Examples of implementation

[0031] The invention is explained in more detail below using an exemplary embodiment illustrated in the figures. It shows: Fig. 1: An isometric view of a double-end tenoner, Fig. 2: An isometric view of a chain unit according to the invention, Fig. 3: A detail of a tensioning system of the chain unit according to Fig. 2, Fig. 4: A schematic representation of a transmission device of the clamping system according to Fig. 3.

[0032] An example of implementation that is shown in the Fig. 1 to 4, relates to a chain unit 1 according to the invention, which can be particularly well understood from Fig. 2. Such a chain unit 1 can be used in particular in a double-end tenoner 29, as shown for example in Fig. 1. There, a total of two chain units 1 cooperate, oriented parallel to one another. As a result, the chain units 1 are jointly suitable for conveying workpieces (not shown in the figures) along a conveying direction 30, so that they can be machined using processing devices of the double-end tenoner 29 (not shown individually). The special feature of the double-end tenoner 29 is that a respective workpiece can be machined on two opposite sides simultaneously using processing devices.

[0033] In the example shown, the chain unit 1 has a chain wheel 3 on a drive head 2 and a guide wheel 5 opposite it on a guide head 4. The chain wheel 3 is designed to be rotatably driven about a rotational axis 6 by means of a drive (not shown), which can be formed by an electric motor. The guide wheel 5, on the other hand, is designed to be passive, with the guide wheel 5 being mounted so as to be rotatable about a rotational axis 7. The guide wheel 5 and the chain wheel 3 are jointly spanned by a chain 8, which is of endless design. As a result of the drive of the chain wheel 3, the chain 8 is driven in rotation, so that workpieces which are positioned on an upper side of the chain 8 can be conveyed along the conveying direction 30. In the example shown, the chain 8 is equipped with laterally projecting form-locking means which are gripped on the chain wheel 3 to form a form-locking connection.As a result, a torque acting on the sprocket 3 can be transmitted to the chain 8, so that the chain 8 can be driven as intended in the manner described. Furthermore, the chain 8 can have guide elements on its underside, by means of which the chain can be guided laterally. These guide elements can, in particular, be designed in the form of guide rollers, by means of which the chain 8 rolls on a guide surface of a base body of the chain unit 1.

[0034] The chain unit 1 further comprises a tensioning system 9, which can be particularly well adjusted by means of Fig. 3. The tensioning system 9 serves to effect and maintain a chain tension of the chain 8. For this purpose, the tensioning system 9 comprises a tensioning element 10, which in the example shown is formed by a spring element pre-tensioned with a compressive force. At a first end 13 of the tensioning element 10, the latter is supported against an abutment 12. At its opposite second end 14, the tensioning element 10 is supported on a transmission device 15, which is described in further detail below in connection with Fig. 4 is explained.

[0035] In the example shown, the clamping element 10 is guided along a threaded bolt, which interacts with an adjusting element 11 beyond the first end 13 of the clamping element 10. In the example shown, the adjusting element 11 is formed by a nut whose internal thread meshes with an external thread of the threaded bolt. Furthermore, the adjusting element 11 interacts with the abutment 12 in such a way that the abutment 12 is movable along a longitudinal axis of the threaded bolt as a result of an adjustment of the adjusting element 11. In this way, the adjusting element 11 can be used to change the effective length of the clamping element 10, the effective length being understood as the distance, measured parallel to the threaded bolt, between the first end 13 and the second end 14 of the clamping element 10.Since the clamping element 10 has a spring constant, a change in the effective length of the clamping element 10 is proportionally accompanied by a change in the clamping force, which acts on the abutment 12 on one side and on the transmission device 15 on the other side by means of the clamping element 10. Accordingly, it is possible to adjust or change the clamping force of the clamping element 10 by means of the adjusting element 11.

[0036] As explained above, the clamping element 10 is supported at its second end 14 on the transmission device 15. This occurs at a support point 24, which in the example shown is located approximately centrally on the transmission device 15. The transmission device 15 serves to transmit the clamping force introduced at the support point 24 to two guide axes 16, 17, which are connected to the transmission device 15 at opposite ends. In other words, connection points 22, 23 of the guide axes 16, 17 are arranged at opposite ends of the transmission device 15, wherein the connection points 22, 23 are formed on a side of the transmission device 15 opposite the support point 24. In the example shown, longitudinal axes 20, 21 of the guide axes 16, 17 are oriented parallel to an axis of action 19 of the clamping force of the clamping element 10.The guide axes 16, 17 are formed by elongated rods. They form supports for the transmission device, allowing the clamping force of the clamping element 10 to be transferred to the guide axes 16, 17.

[0037] The transfer of the clamping force of the clamping element 10 to the guide axes 16, 17 takes place in the example shown in the manner of a beam on two supports, with the guide axes 16, 17 forming the supports for the clamping force of the clamping element 10. In the example shown, the support point 24 for the clamping element 10 is arranged centrally between the connection points 22, 23 of the guide axes 16, 17, so that the clamping force acts in the center of the field of the transmission device 15. The clamping force, which, as a result of the prestressing of the clamping element 10, presses with a compressive force onto the surface of the transmission device 15 on which the support point 24 is located (“front side” of the transmission device 15), leads to a deformation of the transmission device 15 in the form of a deflection of the same between the guide axes 16, 17 and the associated connection points 22, 23. This is shown in Fig. 4 by means of a qualitative bending line 32.

[0038] In the example shown, the guide axes 16, 17 interact indirectly with the deflection wheel 5, so that the tensioning force exerted by the tensioning element 10 is ultimately transmitted via the guide axes 16, 17 into the deflection wheel 5. This presses the deflection wheel 5 against the chain 8, tensioning the chain 8. The chain 8 accordingly exerts a counterforce that prevents further outward movement of the deflection wheel 5. Accordingly, movement of the guide axes 16, 17 along their respective longitudinal axes 20, 21 is only possible until an equilibrium is reached between the tensioning force of the tensioning element 10 and the counterforce caused by the chain tension of the chain 8.This obstruction of further movement of the guide axes 16, 17 results in these opposing forces acting on the transmission device 15 against the clamping element 10 and, accordingly, serving the transmission device 15 as a static support for the clamping force of the clamping element 10. For this reason, the described bending line 32 forms in the transmission device 15, which results from the formation of a bending moment in the transmission device 15. This bending moment is equal to a quarter of the clamping force multiplied by an effective length 31 of the transmission device 15 between the longitudinal axes 20, 21 of the guide axes 16, 17.

[0039] The deflection wheel 5 is mounted by means of a linearly movable bearing device, which is designed to be movable in a direction parallel to the longitudinal axes 20, 21. In this way, the deflection wheel 5 can be moved linearly in the manner described under the action of the tensioning force of the tensioning element 10, thereby influencing the chain tension of the chain 8.

[0040] Accordingly, the tensioning force of the tensioning element 10 is proportional to the chain tension of the chain 8. In the example shown, the transmission device 15 is equipped on its underside, which is opposite the front side of the transmission device 15, with a strain gauge 18 that is intended and configured to metrologically detect deformations of the transmission device 15. In particular, the strain gauge 18 can be formed by one or more strain gauges, wherein an alignment parallel to a connecting line between the connection points 22, 23 of the guide axes 16, 17 is of particular interest for a measurement. In the example shown, the strain gauge 18 is arranged directly along the effective axis 19 of the tensioning force of the tensioning element 10, opposite the support point 24 on the transmission device 15.

[0041] By means of the strain gauge 18, it is now possible to register a change in the chain tension 8, which, as explained above, is reflected in a change in the tensioning force of the tensioning element 10, since this change is also accompanied by a change in the deformation state of the transmission device 15. Consequently, by means of the strain gauge 18, it is possible to continuously monitor the chain tension of the chain 8. However, this monitoring does not take place directly on the chain 8, but indirectly by monitoring a deformation state of the transmission device 15.

[0042] In the example shown, the strain measuring device 18 interacts with an evaluation device 27, which is connected to the strain measuring device 18 in a data-transmitting manner. The evaluation device 27 is suitable for processing the information acquired by the strain measuring device 18. In this way, the evaluation device 27 can be configured, in particular, to transmit information to a machine operator of the double-end tenoner 29 upon detection of a minimum value for the deflection of the transmission device 15 or, analogously, upon detection of a minimum value for the chain tension of the chain 8.

[0043] In a further embodiment, the evaluation device 27 in the example shown interacts with an actuator 28, so that the evaluation device 27 can control the actuator 28. The actuator 28 acts directly on the actuating element 11, so that by operating the actuator 28, the actuating element 11 can be adjusted and, as explained above, the tensioning force of the tensioning element 10 can be changed. In this way, it is possible to automatically adjust the chain tension of the chain 8, for example, by continuously comparing an actual value of the chain tension with a target value. These values ​​correspond directly to an actual deformation or a target deformation of the transmission device 15, which is directly measured by the strain measuring device 18. List of reference symbols 1 chain unit 2 drive head 3 sprocket 4 Deflection head 5 Deflection wheel 6 axis of rotation 7 axis of rotation 8 Chain 9 clamping system 10 clamping element 11 Control element 12 abutments 13 first end 14 second end 15 Transmission device 16 Guide axis 17 Guide axis 18 Strain gauge 19 Axis of influence 20 Longitudinal axis 21 Longitudinal axis 22 Junction 23 Junction 24 support point 25 Front 26 Back 27 Evaluation device 28 Actuator 29 double-end tenoners 30 Conveying direction 31 length 32 bending line

Claims

[1] Chain unit (1) for driving workpieces along a processing path, comprising - a drive head (2) with a chain wheel (3) which can be driven in rotation about a rotation axis (6), - a deflection head (4) with a deflection wheel (5) rotatable about a rotation axis (7), - a self-contained chain (8) spanning the chain wheel (3) and the idler wheel (5), - a tensioning system (9) for tensioning the chain (8), wherein the chain wheel (3) is rotatably driven by means of a rotary drive, so that the chain (8) rotates around the chain wheel (3) and the deflection wheel (5), the clamping system (9) comprising - at least one clamping element (10), - at least one adjusting element (11) for adjusting a clamping force of the clamping element (10), - an abutment (12) against which the clamping element (10) is supported at its first end (13), - a transmission device (15) against which the clamping element (10) is supported at its second end (14), - at least two guide axes (16, 17) connected to the transmission device (15) and extending parallel to one another, wherein the clamping force introduced into the transmission device (15) as a result of the support of the second end (14) of the clamping element (10) can be diverted to the two guide axes (16, 17) by means of the transmission device (15), wherein the chain wheel (3) or the deflection wheel (5) is mounted directly or indirectly by means of the guide axes (16, 17), so that the chain wheel (3) or the deflection wheel (5) can be pressed against the chain (8) by means of the tensioning force of the tensioning element (10) and thereby the chain (8) can be tensioned with a chain tension, characterized by a strain measuring device (18) which is arranged on the transmission device (15) in such a way that it is designed to detect information relating to a deformation of the transmission device (15) which occurs as a result of the action of the clamping force and its derivation towards the guide axes (16, 17). [2] Chain unit (1) according to claim 1, characterized by that an axis of action (19) of the clamping force and longitudinal axes (20, 21) of the guide axes (16, 17) are oriented parallel to each other. [3] Chain unit (1) according to one of the preceding claims, characterized bythat connection points (22, 23) at which the guide axes (16, 17) are connected to the transmission device (15) are located on a rear side (26) of the transmission device (15) which, with respect to an axis of action (19) of the clamping force, is opposite a front side (25) of the transmission device (15), at which a support point (24) is located, at which the clamping element (10) is supported with its second end (14) on the transmission device (15). [4] Chain unit (1) according to one of the preceding claims, characterized by that the transmission device (15) is statically designed in the manner of a beam on two supports, wherein the guide axes (16, 17) form supports of the transmission device (15), wherein the supports are preferably arranged opposite one another at the ends of the transmission device (15). [5] Chain unit (1) according to claim 4, characterized bythat a support point (24), at which the tensioning element (10) is supported with its second end (14) on the transmission device (15), is arranged at least substantially in the middle of the field between connection points (22, 23) at which the guide axes (16, 17) are connected to the transmission device (15). [6] Chain unit (1) according to one of the preceding claims, characterized by in that the strain measuring device (18) is arranged on a rear side (26) of the transmission device (15), which is opposite a front side (25) of the transmission device (15), wherein a support point (24), at which the clamping element (10) is supported with its second end (14) on the transmission device (15), is located on the front side (25) of the transmission device (15). [7] Chain unit (1) according to claims 4 to 6, characterized bythat the strain measuring device (18) is arranged along an axis of action (19) of the clamping force opposite the support point (24) of the second end (14) of the clamping element (10) at least substantially in the field center of the transmission device (15) on the rear side (26) of the transmission device (15). [8] Chain unit (1) according to one of the preceding claims, characterized by an evaluation device (27) which is operatively connected to the strain measuring device (18) in a data-transmitting manner, wherein the evaluation device (27) is provided and configured to process information relating to the deformation of the transmission device (15) detected by means of the strain measuring device (18). [9] Chain unit (1) according to claim 8, characterized bythat the evaluation device (27) is provided and arranged to continuously evaluate an actual deformation of the transmission device (15) and to deduce an acting clamping force of the clamping element (10) from the actual deformation. [10] Chain unit (1) according to claim 9, characterized by that the evaluation device (27) is provided and arranged to automatically send out information in the event that the clamping force falls below a predetermined minimum value. [11] Chain unit (1) according to one of the preceding claims, characterized by an actuator (28) which cooperates with the actuating element (11) and is provided and configured to act on the actuating element (11) and thereby change the clamping force of the clamping element (10). [12] Chain unit (1) according to claims 10 and 11, characterized bythat the actuator (28) is connected to the evaluation device (27) in a data-transmitting manner, wherein the evaluation device (27) is provided and set up to control the actuator (28) in such a way that the actuating element (11) is adjusted and the clamping force of the clamping element (10) is thereby increased in the event that the clamping force falls below the predetermined minimum value. [13] Method for operating a chain unit (1), the chain unit (1) comprising - a drive head (2) with a chain wheel (3) which can be driven in rotation about a rotation axis (6), - a deflection head (4) with a deflection wheel (5) rotatable about a rotation axis (7), - a self-contained chain (8) spanning the chain wheel (3) and the idler wheel (5), - a tensioning system (9) for tensioning the chain (8), - a strain measuring device (18), wherein the chain wheel (3) is driven in rotation by means of a rotary drive, so that the chain (8) rotates around the chain wheel (3) and the deflection wheel (5), the clamping system (9) comprising - at least one clamping element (10), - at least one adjusting element (11) for adjusting a clamping force of the clamping element (10), - an abutment (12) against which the clamping element (10) is supported at its first end (13), - a transmission device (15) against which the clamping element (10) is supported at its second end (14), - at least two guide axes (16, 17) connected to the transmission device (15) and extending parallel to one another, wherein the clamping force introduced into the transmission device (15) as a result of the support of the second end (14) of the clamping element (10) is diverted to the two guide axes (16, 17) by means of the transmission device (15), wherein the chain wheel (3) or the deflection wheel (5) is mounted directly or indirectly by means of the guide axes (16, 17), so that the chain wheel (3) or the deflection wheel (5) is pressed against the chain (8) by means of the tensioning force of the tensioning element (10) and the chain (8) is thereby tensioned with a chain tension, wherein the strain measuring device (18) is arranged on the transmission device (15) in such a way that it is designed to detect information relating to a deformation of the transmission device (15) which occurs as a result of the action of the clamping force and its derivation to the guide axes (16, 17), characterized by , that by means of the strain measuring device (18) information relating to a deformation of the transmission device (15) which occurs as a result of the action of the clamping force and the derivation of the clamping force to the guide axes (16, 17) is continuously recorded. [14] Method according to claim 13, characterized by that the recorded information is processed by means of an evaluation device (27), wherein information is preferably automatically sent when a preset minimum value for the clamping force of the clamping element (10) is detected to be undershot. [15] Method according to claim 14, characterized by that an actuator (28) which interacts with the actuating element (11) is controlled by means of the evaluation device (27) when the minimum value for the clamping force is undershot, wherein the actuating element (11) is adjusted by means of the actuator (28) in such a way that the clamping force of the clamping element (10) is increased.

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