DEVICE FOR PRESSING FLAT MATERIAL

Description

[0001] The invention relates to a device for the pressing processing of flat material according to the preamble of claim 1.

[0002] Such devices can be used, for example, for pressing processes, particularly for the continuous lamination and / or impregnation of flat material webs or material segments. Heating elements can also be provided to heat the flat material for pressing. The device can be, for example, a double-belt press, which is used, for example, for the production of fiber-reinforced plastics.

[0003] A device of the type mentioned above is known from EP 2 540 475 B1. This is a double belt press in which two endless steel belts are driven and pressed against each other with their respective working strands, with the material to be processed being guided and pressed between the steel belts in the direction of transport. The steel belts and thus indirectly the flat material to be pressed are heated for processing by means of inductive heating elements. The flat material is a composite material made of thermoplastic and filaments. A cooling unit comprising press rollers is provided behind the heating elements in the direction of transport, which presses the top and bottom of the flat material via the steel belts. For cooling purposes, cooling water flows through at least one of the press rollers. When the double belt press is in use, the inductive heating elements surround each of the two steel belts in the heating area.The heating elements are designed to have a lower half and an upper half, which can be temporarily separated from each other at connection points, thus allowing an opening movement of the working strand of at least one of the steel belts. The press rollers create linear contact with the steel belt, thus applying pressure that is strictly limited in time and location.

[0004] EP 0236905 B1 discloses a device for applying surface pressure to advancing workpieces, which also represents a double-belt press. The pressing pressure is generated by pressure plates arranged on either side of the respective working strand of the press belts. The transport of the flat material is made possible by closed paths of roller strands that are guided between the respective pressure plate and the associated press belt, roll on the pressure plates and transport the press belt and the workpiece clamped between the press belts. It is proposed that the rollers on each roller strand be positively and / or non-positively connected to one another, enclose an axle rod with a large annular gap that exceeds the bearing clearance, and are elastically deformable up to the axle contact with the axle rod. The elastic deformability of the rollers can have a tolerance-compensating effect.In addition, the aforementioned annular gap can act as a heat-insulating layer to protect the axle rod when the printing plates are heated or cooled. This prior art does not describe how active heating could be achieved.

[0005] DE 24 14 762 C2 discloses a double-belt press comprising a plurality of pairs of press rollers, the gap between which allows the passage of the flat material being adjustable. The gap is regulated by a pressure measured by a pressure measuring device in a calibration section of the double-belt press. The steel belt can be heated by sliding shoes arranged between two pairs of press rollers. The sliding shoes cause abrasion and thus increase the wear of the double-belt press.

[0006] EP3 061 859 A1 discloses a device for producing films using waste paper fibers. A thin, web-like flat material is first formed on a mesh belt and then fed to a pressing process via a conveyor belt. Pressing is performed by pairs of press rollers, with a first pressing process without heating the flat material, followed by a further pressing process at lower pressure and simultaneous heating. Both pressing processes act directly on the flat material. A double-belt press is therefore not implemented. The flat material can be heated by halogen heaters provided in the heating press rollers.

[0007] It is disclosed to provide the press rollers with an elastic layer, e.g., made of plastic. The elastic properties of the press rollers are intended to ensure contact between the press rollers over their entire axial length.

[0008] WO2010 / 031364 A1 discloses a device for producing composite components, in which a rolling, roller-shaped pressure unit with an elastically flexible pressure pad presses onto a strip-shaped workpiece lying on a solid substrate, the latter being heated with laser radiation immediately before pressing. A pair of pressure rollers with counteracting pressure rollers is not disclosed. Special measures are provided to protect the pressure pad from overheating due to incident laser radiation, such as a pressure pad material that is (partially) transparent to laser radiation, shading the pressure pad from the laser radiation, or a cooling fluid passed through the pressure pad. The elastically flexible pressure pad serves here to compensate for height differences on three-dimensional workpiece surfaces when applying strip material.

[0009] The invention is based on the technical problem of providing a device of the type mentioned at the outset which enables a more favorable pressure distribution of the press rollers acting on the flat material.

[0010] This object is achieved in a device of the type mentioned above by the characterizing feature of claim 1. Preferred embodiments of the device according to the invention emerge from the dependent claims.

[0011] According to claim 1, a device according to the preamble of claim 1 is characterized in that both press rollers of the press roller pair or at least one of the press roller pairs have, at least on their circumference in the radial direction, an increased elastic deformability compared to steel press rollers.

[0012] Compared to the conventional hard press rollers used in stationary press roller pairs, the elastic deformability distributes the pressing force over a larger area. This surface pressure results in a longer pressure application time compared to the linear contact pressures of conventional steel rollers or steel press rollers, thus resulting in an improved and more homogeneous pressing effect.

[0013] Compared to the use of fluid pressure pads, which can also create a flat pressure zone, the system engineering effort is significantly lower, and highly wear-prone sealing systems are avoided. The equally conceivable creation of flat pressure zones through the use of sliding plates would result in severely limited process pressures and increased wear. According to the invention, however, a flat pressure is possible despite the rolling movement of the pressure rollers.

[0014] The device according to the invention can advantageously be designed such that at least two pairs of press rollers are arranged one behind the other in the transport direction. The device according to the invention is particularly advantageous because it is designed as a double belt press. In this case, the at least one pair of press rollers acts indirectly, namely via one of the belts on the flat material. The elastic deformability of the rollers of the at least one pair of press rollers is gentle on the belts used, without losing the advantage of surface pressure compared to pure line contact. In the case of the double belt press, in which usually at least one of the belts is driven, the belt pair and the at least one pair of press rollers form the means for transporting the flat material to be processed.

[0015] The device according to the invention has at least one heating element for heating the flat material. Heating elements are typically used for the production of composite materials or for lamination. One or more heating elements may be useful for the invention. Although the heating elements are generally referred to in the plural in the following description of the invention for the sake of simplicity, the invention also relates to corresponding embodiments with only one heating element.

[0016] In the double-belt press, the heating elements can act on the flat material indirectly via the belts of the double-belt press. According to the invention, inductive heating is used. One or more inductors are preferably arranged on both sides of the working areas of the press belts.

[0017] The device according to the invention can also be designed such that at least a portion of the heating means is configured to generate magnetic fields having a predominantly magnetic field component oriented perpendicular to a center plane of the flat material. This can be achieved by means of a flat inductor or a similarly constructed inductor with a corresponding effect. For example, it can be provided that the heating means or at least a portion of the heating means have a meandering course, at least in sections. The meandering course can be aligned such that the loops of the meander, during use, run parallel to the center plane of the flat material to be heated.

[0018] Furthermore, it can be provided that at least some of the heating means are designed to surround a portion of the flat material to be heated in a U-shape. In this case, the inductors can be configured such that they can be pushed into a working position along a longitudinal side of the flat material. This does not completely enclose the flat material, which is why a relative movement of two parts of the same inductor to each other, associated with the opening and closing of electrical contacts, is not required.

[0019] The effect of the heating element on the material to be heated can depend considerably on the distance between the material and the workpiece. This is particularly true for inductive heating with its interaction with the inductively coupled material. The latter can be the flat material to be processed. In the case of a double belt press, however, the induction currents are generally generated in the belt material of the double belt press, which in turn conductively heats the flat material to be processed. The elastic deformability of the press rollers of at least one of the press roller pairs can result in the position of a center plane of the flat material running parallel to the transport direction and parallel to the axes of rotation of the press rollers shifting perpendicular to this center plane. The shift can occur, for example, if the position of the axis of rotation of one of the press rollers in a press roller pair remains constant in the device during pressure build-up, while the axis of rotation of the other press roller shifts.

[0020] In order to ensure that the flat material is heated as reproducibly as possible, it may be particularly advantageous to design the device according to the invention in such a way that means are provided which enable the position of the at least one heating element to be adapted to the position of the central plane.

[0021] Such adjustment can be achieved by passively tracking the at least one heating element, for example, by means of spacers between the flat material or the associated belt of the double-belt press and the at least one heating element. Such a spacer can be achieved, for example, by means of a rolling or sliding spacer element. At the same time, elastic forces can press the at least one heating element toward the flat material or the associated belt of the double-belt press. To prevent the heating elements from shifting parallel to the centerline of the flat material, guide means can be provided.

[0022] However, it may also be advantageous to design the device according to the invention such that the distance between the heating elements and the center plane of the flat material is controlled by means for controlling or regulating this distance. These means may include, for example, electric motors and linear guides, whereby the control or regulation may be based on sensor values ​​from distance sensors that determine the position of the center plane relative to the rotational axes of the press rollers. This has the advantage that, unlike with passive spacers, deliberate changes in the distance can be brought about in order to further influence the extent or type of heating.

[0023] It may also be advantageous to design the device according to the invention such that at least two pairs of press rollers can be subjected to different pressing forces in a controllable or adjustable manner. In this way, different pressure profiles can be set, for example, with pressures that vary over the course of the pressing range.

[0024] The device according to the invention can also be designed such that at least one of the rollers of at least one pair of rollers has a cavity for the passage of a cooling fluid. This protects the elastic material on the circumference of the press rollers from potentially harmful high temperatures.

[0025] Furthermore, it may be advantageous to design the device according to the invention such that at least one of the press rollers of at least one pair of press rollers is protected on its outer circumference by a heat-insulating layer. This provides further effective protection for the respective press roller against the influence of the temperature of the flat material or the belt of the double-belt press. The heat-insulating layer can be an integral part of the press roller. Alternatively, the heat-insulating layer can also be formed by a separate belt guided around a partial circumference of the roller. This has the advantage that the heat-insulating layer is easily replaceable and / or can be guided through a cooling zone spaced apart from the press roller as it rotates. Materials for the heat-insulating layer or the heat-insulating belt can be, for example:These can be textile structures, for example, made of glass, carbon, aramid, basalt, or high-performance elastomers such as Kalrez ®< from DuPont ™< , or coated metal strips. Advantages include low thermal conductivity, high temperature resistance, pressure and abrasion resistance, and elasticity, at least in the circumferential direction of the press roll. The latter is particularly advantageous when deformation of the elastically deformable layer leads to a change in its circumference, which the heat-insulating layer must follow.

[0026] Finally, the device according to the invention can be designed in such a way that, during use, a cooling fluid is directed from the outside onto the circumference of the press roller and / or onto the end faces of the press roller, thereby providing an additional cooling effect.

[0027] Advantageous embodiments of the device according to the invention are illustrated below with reference to figures.

[0028] It shows schematically: Fig. 1: a double belt press, Fig. 2: a pair of press rollers before and after pressure build-up with heating elements and flat material to be processed without heating medium feed, Fig. 3: a pair of press rollers before and after pressure build-up with heating elements and flat material to be processed with heating element feed, Fig. 4: the principle of heating medium feed with spacers, Fig. 5: the principle of motor-driven heating element feed, Fig. 6: press roller with integrated heat-insulating layer, Fig. 7: press roller with separate heat-insulating band guided around a deflection roller, Fig. 8: press roller with separate heat-insulating band guided around two deflection rollers, Fig. 9: perspective side view of a workpiece with inductively acting heating elements and Fig. 10: an inductive heating element surrounding the workpiece in a side view.

[0029] Fig. 1shows a schematic side cross-section of a double belt press with an upper press belt 1 and a lower press belt 2. The endless press belts 1 and 2 are each guided around an upper drive roller 3 and lower drive roller 4, respectively, as well as around an upper deflection roller 5 and a lower deflection roller 6, respectively. Between a working strand 7 of the upper press belt 1 and a working strand 8 of the lower press belt 2, flat material to be processed, not shown here, is guided, which in a transport direction (in Fig. 1 from left to right) is carried along by the circulating press belts 1 and 2. Along the working strands 7 and 8, a plurality of press roller pairs 9 are arranged, with which the upper working strand 7 and the lower working strand 8 are pressed against the flat material to be processed, not shown here. Furthermore, along the working strands 7 and 8 in Fig. 1Heating elements (not shown individually) are arranged in a main heating zone 10 and in intermediate heating zones 11, which act inductively. Either the material of the press belts 1 and 2 is inductively coupled, or the flat material to be processed. Due to the large number of heating elements and their positioning between the press roller pairs 9, a temperature required for processing the flat material can be maintained over a long distance. The arrangement shown here of one intermediate heating zone 11 between two press roller pairs 9 is only an example. The number of intermediate heating zones 11 and the arrangement of the press roller pairs 9 adjacent to the intermediate heating zones 11, e.g. individually or in groups of two or more press roller pairs 9, can be designed differently depending on the operating requirements of the double belt press. Cooling sections 12 are optionally arranged at the end of the work sections 7 and 8, viewed in the direction of transport.

[0030] Fig. 2shows schematically a pair of press rollers 9 with an upper press roller 13 and a lower press roller 14, wherein in a) the situation before application of a pressing pressure is shown and in b) the situation under a certain pressing pressure. Between the press rollers 13 and 14, a workpiece 15 made of flat material to be machined is schematically shown, wherein in the illustration the press belts 7 and 8 taking the workpiece 15 between them (see Fig. 1 ) are not visible. The pressing rollers 13 and 14 have an elastically deformable area 16 on their outer circumference. The contact pressure of both pressing rollers 13 and 14 is determined according to Fig. 2symmetrically constructed, ie due to the flexibility of the elastically deformable area 16, the axes of rotation 17 and 18 of the press rollers 13 and 14 move towards the workpiece 15 with the same distance ΔI, which is why the vertical position of a center plane 19 of the workpiece 15 is not changed by the application of the pressing pressure. Fig. 2 also shows schematically the position of heating elements 20 as they are used in the main heating zone 10 or in the intermediate heating zones 11 (see Fig. 1 ) may be provided. The distance between these heating elements 20 perpendicular to the center plane 19 remains unchanged despite the displacement of the positions of the rotational axes 17 and 18 caused by the application of the pressing pressure. However, in order to achieve a symmetrical movement of the press roller pairs 13 and 14 with respect to the center plane 19, a considerable control effort is required.

[0031] Fig. 3 shows a Fig. 2similar situation. The same reference numbers refer to the same device elements, so that the description can be Fig. 2 The starting position of the press rollers 13 and 14 shown in part a) is identical to the starting position in Fig. 2a ). One difference is that the rotational axis 18 of the lower press roller 14 in the arrangement according to Fig. 3is fixed in its position. To apply the pressing pressure, only the axis of rotation 17 of the upper pressing roller is moved by a distance 2ΔI in the direction of the lower axis of rotation 18. Since the deformation of the pressing rollers 13 and 14 is the same due to the otherwise identical structure, the center plane 19 of the workpiece 15 will move by the distance ΔI towards the lower pressing roller 14. In order to prevent the effect of the heating elements 20 on the workpiece 15 from changing due to the application of the pressing pressure, it is provided that the distance of the heating elements 20 from the center plane 19 is not changed and that the heating elements 20 are also moved by the distance ΔI. With this measure, the advantage of the surface pressure achieved by means of the elastically deformable region 16 is achieved without being restricted by an effect of the heating elements 20 on the workpiece 15 which would otherwise only be reproducible to a limited extent.

[0032] Fig. 4shows a schematic cross-section perpendicular to the material transport direction of a double belt press with two heating elements 20, one above and the other below the workpiece 15, and the workpiece 15 is held between press belts 1 and 2. The heating elements 20 are held on holders 21 in such a way that, during operation of the double belt press, the distance between the respective heating element 20 and the associated press belt 1 or 2 is as constant as possible. Spacers 23 are provided here for this purpose. In order to be able to follow a possible vertical movement of the respective press belt 1 or 2, the heating elements 20 are pressed in the direction of the associated press belt 1 or 2 with a force which is symbolized here in each case by a spring element 22.For the upper heating element 20, this force can also be composed of its weight and a supporting force counteracting gravity, with the supporting force intended to reduce the load on the upper press belt 1. The spacers 23 are preferably fixed to the respective heating element 20 and can roll along the associated press belt 1 or 2. Sliding spacers can of course also be provided alternatively or additionally. Guide elements 24 are provided to guide the holders 21.

[0033] Fig. 5 also shows a cross-section of a double belt press, in which - unlike Fig. 4- the distance between the heating elements 20 and the workpiece 15 arranged between the press belts 1 and 2 is adjusted by means of electric motors 25 and linear guides 26. Sensor values ​​from distance sensors 27, which measure, for example, mechanically, optically, or capacitively, serve as the basic variable for the control or regulation of the electric motors 25 via a control or regulating device 28.

[0034] Fig. 6shows schematically a press roller 29 pressing on the upper press belt 1 with a heat-insulating layer 30 firmly arranged on its outer circumference, which is applied directly to an elastically deformable region 31 of the press roller. The elastically deformable region 31 in turn surrounds a hollow cylinder 33 made of a material that is stiff in comparison, e.g. stainless steel. An inner cavity 32 of the hollow cylinder 33 can be used for the flow of a cooling fluid. The elastically deformable region 31, e.g. made of silicone, can have a thickness of 1 to 20 mm, preferably 5 to 15 mm, and a hardness between, for example, 20 Shore-A and 65 Shore-A, preferably between 50 Shore-A and 60 Shore-A.

[0035] Fig. 7shows a press roller 34 in which the heat-insulating layer is not fixed over the entire circumference, but is realized by a circumferential belt 35, which only rests on the elastically deformable region 36 over part of its circumference and is otherwise guided at a distance from the press roller 34 via a deflection roller 37. In the spaced area between the press roller 34 and the deflection roller 37, there is an improved possibility of separate cooling of the belt 35. In addition, the seal-affixed belt 35 is easily replaceable. Fig. 8 shows a Fig. 7 A similar variant, in which the belt 35 is guided over two deflection rollers 37, whereby a smaller wrap angle of the belt 35 with the press roller 34 is realized and a better cooling possibility can be provided. For further details, please refer to the description. Fig. 7 referred to.

[0036] For all designs, the press rollers do not necessarily have to be hollow cylinders. Other shapes, with or without passages for a cooling fluid, are also conceivable.

[0037] Fig. 9 shows a perspective oblique view of a workpiece 15 to be machined, whereby the double belt press only has one in a main heating zone 10 (see also Fig. 1) arranged, inductively acting first heating element 38 with a connection element 42 and a further inductively acting heating element 39, 40 and 41 arranged in intermediate heating zones 11 with a collective connection element 43 are shown schematically. In the main heating zone 10, the first heating element 38 is guided in a plurality of heating loops, one above the workpiece 15 and the other below the workpiece 15. In the intermediate heating zones 11, the second heating element 39, the third heating element 40 and the fourth heating element 41 each have a heating loop above and a heating loop below the workpiece 15. In the intermediate heating zones 11, more than one heating loop each and different numbers of heating loops in different intermediate heating zones 11 are also conceivable. The heating elements 39, 40 and 41 can be arranged as in Fig. 9shown, they can be supplied with power and cooling water via the collective connection element 43 by a preferably controllable AC source (not shown here), or individually, without a collective connection element, directly with a controllable AC source. The latter offers the advantage of individual power control and thus individual heating in the holding zones 11.

[0038] Fig. 10 shows the first heating element 38 guided around the workpiece 15 with the connecting element 42 in a side view. The illustrations of Fig. 9 and Fig. 10 differ slightly, especially in the connecting element 42, but this is not important here. The connecting element 42 is - as is the collective connecting element 43 ( Fig. 9) - prepared for contacting a preferably controllable alternating current source (not shown here). The heating loops of the first heating element 38 are mechanically stabilized against each other by two parallel cross-connectors 44 made of an electrically insulating material.

[0039] The electrical connection between the upper loops and the lower loops of the first heating element 38 is realized by two transition pieces 45, each of which is guided around the edge of the workpiece 15 on the side facing the connection element 42. On the side facing away from the transition pieces 45, the first heating element 38 is open and can thus be guided laterally over the workpiece 15 or the workpiece 15 can be inserted laterally, so that maintenance or replacement of the first heating module 38 is possible even when the workpiece 15 is in the double-belt press.

[0040] The illustrated path of the loops of the first heating element 38 above and below the workpiece results in the magnetic fields generated during operation of the first heating element 38 being aligned perpendicular to the center plane of the workpiece 15, i.e., transverse magnetic fields are generated. Such transverse fields can be technically and economically more efficient than longitudinal fields running parallel to the center plane when heating flat material, i.e., when the ratio of material width to thickness is high.

[0041] The statements regarding the first heating element 38 also apply correspondingly to the other heating elements 39, 40 and 41 in the intermediate heating zones 11.

[0042] Of course, other design variants for the heating elements are also possible, e.g. those in which the part running below the workpiece 15 and the part running above the workpiece are movable independently of each other at least over a certain distance, e.g. in order to implement the design according to Fig. 5 To achieve this, the two parts can be assigned to separate connection elements, for example, or the electrical connection between the two components can be made via flexible or length-adjustable transition pieces. It should be noted that the vertical movement of the heating elements is important to ensure a largely constant distance between the heating element and the workpiece (see, for example, Figs. 4 and 5 ) requires only short distances in the mm or cm range. List of reference symbols

[0043] 1 Upper press belt 32 cavity 2 Lower press belt 33 hollow cylinder 3 Upper drive roller 34 Press roll 4 Lower drive roller 35 band 5 pulley 36 elastically deformable area 6 pulley 37 pulley 7 Working strand upper press belt 38 first heating element 8 Working strand lower press belt 39 second heating element 9 Pair of press rollers 40 third heating element 10 Main heating zone 41 fourth heating element 11 Intermediate heating zone 42 connecting element 12 Cooling section 43 Collective connection element 13 upper press roller 44 Cross connectors 14 lower press roller 45 transition piece 15 workpiece 16 elastically deformable area 17 axis of rotation 18 axis of rotation 19 Middle level 20 heating element 21 bracket 22 spring element 23 spacers 24 Guide element 25 electric motor 26 Linear guide 27 Distance sensors 28 Control or regulating device 29 Press roll 30 heat-insulating layer 31 elastically deformable area

Claims

1. A device for pressing processing flat material, comprising means for transporting the flat material (15) in a transport direction and at least one pressing roller pair (9) which is stationary in the transport direction and acts on the flat material (15) on both sides, wherein the device is a double-belt press, and heating means (20) for heating the flat material (15), wherein at least a number of the heating means (20) act inductively characterized in that,' both pressing rollers (13, 14, 29, 34) of the pair of pressing rollers (9) or both pressing rollers (13, 14, 29, 34) of at least one of the pairs of pressing rollers (9) have, at least on their circumference, an increased elastic deformability in the radial direction compared to pressing rollers made of steel.

2. Device according to claim 1, characterized in that the pressing rollers (13, 14, 29, 34) with increased elastic deformability each have an elastically deformable region (16, 31, 36) with a thickness of 1 to 20 mm, preferably 5 to 15 mm, and a hardness of between 20 Shore-A and 65 Shore-A, preferably between 50 Shore-A and 60 Shore-A, in that the pressing rollers (13, 14, 29, 34) with increased elastic deformability each have a heat-insulating layer (30) arranged fixedly on their outer circumference, the heat-insulating layer (30) being applied in each case directly to the elastically deformable region (16, 31, 36) of the pressing roller (13, 14, 29, 34), and in that the elastically deformable region (16, 31, 36) in each case surrounds a hollow cylinder (33) made of a material which is stiffer in comparison.

3. The device according to any one of the preceding claims, characterized in that there are at least two pressing roller pairs (9) arranged one behind the other in the transport direction.

4. The device according to any one of the preceding claims, characterized in that the heating means (20) act indirectly on the flat material (15) via the belts (1, 2) of the double-belt press.

5. The device according to any one of the preceding claims, characterized in that at least a number of the heating means (20) are designed to generate magnetic fields which have a predominant magnetic field component oriented perpendicular to a center plane (19) of the flat material (15).

6. The device according to any one of the preceding claims, characterized in that the heating means (20) or at least a number of the heating means (20) have a meandering course at least in sections.

7. The device according to any one of the preceding claims, characterized in that at least a number of the heating means (20) are designed to encompass a section of the flat material (15) to be heated in a U-shape.

8. The device according to any one of the preceding claims, characterized by means for controlling or regulating a distance between the heating means (20) and a center plane (19) of the flat material (15) running parallel to the transport direction and parallel to the axes of rotation of the pressing rollers (13, 14, 29, 34).

9. The device according to any one of the preceding claims, characterized by spacers (23) to ensure a constant distance between the heating means (20) and a center plane (19) of the flat material (15) running parallel to the transport direction.

10. The device according to any one of the preceding claims, characterized in that at least two pressing roller pairs (9) can be acted upon in a controllable or regulatable manner with different pressing forces.

11. The device according to any one of the preceding claims, characterized in that at least one of the pressing rollers (13, 14, 29, 34) of at least one pressing roller pair (19) comprises a cavity (32) for the passage of a cooling fluid.

12. The device according to any one of the preceding claims, characterized by cooling means which, during use, direct a cooling fluid from the outside onto the circumference of the pressing roller and / or onto the end faces of the pressing roller.