Heating device and heating method for heating a thermoplastic extrusion material and bending machine with such a heating device

Abstract

A heating device for heating a thermoplastic extrusion material (2) to be bent has several heating elements which define a heating area for the extrusion material (2) extending axially along the longitudinal direction (4), wherein each heating element is designed as a contact heating jaw group (16, 18, 20, 22) consisting of several heated heating jaws (24, 26, 28, 30, 32, 34, 36, 38) which have contact surfaces (42) that are designed to be complementary to the outer surface (44) of the extrusion material (2) in order to enclose the extrusion material (2) at its outer surface (44) for contact heat transfer, wherein a closing drive (46, 48, 50, 52) closes each heating jaw group (16, 18, 20, 22) by moving the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) opens and closes by bringing the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) together for contact heat transfer,so that the axial length of the effective heating area is determined by the number of heating jaw groups (16, 18, 20, 22) enclosed around the strand material (2).

Description

[0001] The invention relates to a heating device for heating a thermoplastic extrusion material with an outer profile extending along a longitudinal direction and which is to be bent and heated for this purpose in at least one longitudinal section. The heating device comprises a heating element that defines a heating area for the extrusion material extending axially along the longitudinal direction. Furthermore, the heating device comprises a closing actuator for opening and closing the heating element around the extrusion material and a control unit that actuates the closing actuator to adapt the heating area to the longitudinal section.

[0002] Such a heating device is known, for example, from DE 10 2012 005 973 A1. It serves to heat a bendable thermoplastic tube. For this purpose, it has several heating elements, each in the form of a tubular shell, on the inside of which a multitude of infrared emitters are arranged. Each tubular shell can be opened and closed by means of a hinge. This makes it possible to place a plastic tube to be heated inside the tubular shell, which is then heated by radiant heat along the length of the respective heating element. Several such heating elements can be placed one behind the other in the longitudinal direction to heat the extruded material in a longitudinal section of adjustable length. This device presents a design conflict. To achieve the fastest possible heating, the infrared emitters should ideally be operated at the highest possible temperature.This has the disadvantage that a large amount of heat is generated in the heating device, and sections of the extruded material are also heated that should not be heated at all. Furthermore, it takes a comparatively long time for the infrared emitters to reach the required temperature when a new heating element is switched on, i.e., when it is moved into the open position and then closed around the extruded material. Similarly, it also takes a comparatively long time for the very hot infrared emitters to cool down again when a heating element is opened and removed from the extruded material. In addition, the timing of the heating device is comparatively difficult to coordinate with the operation of the bending machine equipped with it, because the temperature that the extruded material reaches in the heating element depends on how long the extruded material remains in the heating element.If the heating time is too long, the extruded material can be heated above the desired temperature, potentially causing damage. Therefore, once the desired heating time has elapsed, the extruded material must be moved as far as possible to remove it from the area where the heating element is emitting heat. This places limitations on the otherwise normal operation of the bending machine, as, for example, a potentially lengthy cooling process of a recently created bend cannot be waited for.

[0003] EP 3 285 985 B1 discloses a method and an apparatus for bending plastic pipes, wherein a plastic pipe is shaped by heating, bending, and cooling. This apparatus uses hot air heating, which also allows the temperature to be adjusted over time. A movable pipe heating arrangement enables overlapping time windows with bending and cooling at a first bending position and simultaneous heating at a second bending position. To adjust the length to be heated, specific distributors, from which heated air is supplied to the plastic pipe, can be connected to the pipe heating arrangement, so that heated air can be applied to different pipe lengths by selecting which distributors are used to supply the heated air.When switched off, the distributors remain in the immediate vicinity of the plastic pipe, thus representing an unwanted heat source and a disruptive contour in the further bending process.

[0004] DE 10 2021 131 986 A1 continues this principle by using a shielding baffle to finely adjust the heat emission range of a radiant heater.

[0005] DE 32 46 845 A1 relates to the coupling of a heating cylinder of a plasticizing system to a heat source. DE 10 2018 111 283 A1 relates to a device for semi-continuous blow molding for the production of thermoplastic, hollow blanks.

[0006] The object of the invention is to provide a device and a method for heating a thermoplastic extrusion material, whereby the time requirements for the operation of a bending machine entail fewer restrictions and at the same time the heating area can be adjusted to a longitudinal section to be heated in the simplest possible way.

[0007] The invention is defined in the independent claims. The dependent claims relate to preferred embodiments.

[0008] A heating device is provided for heating a thermoplastic extrusion material with a lateral surface. The extrusion material extends along a longitudinal direction and is to be bent in at least one longitudinal section. It must be heated for this bending process. The heating device has several heating elements which together define a heating zone extending axially along the longitudinal direction, within which the extrusion material can be heated. Each heating element is designed as a heating jaw group, typically as a pair of heating jaws. Each heating jaw group consists of several heated jaws with contact surfaces that are complementary to the lateral surface of the extrusion material. The heating jaws of each heating jaw group are designed to enclose the extrusion material at its lateral surface for contactive heat transfer, i.e., to enclose it in a contactive manner.Each heating jaw group is therefore designed to contact heat the extruded material over a length determined by the axial length of its heating jaws. The maximum length of the heating area is given by the combined axial length of all heating jaw groups.

[0009] Furthermore, the heating device features a closing actuator that can open each heating jaw group by moving the heating jaws apart and close them by bringing them together. In the closed position, the heating jaws are in contact with the outer surface for effective heat transfer; they are then in an activated position. The closing actuator for opening and closing the heating jaw group around the extruded material can thus determine the axial length of the effective heating area by the number of heating jaw groups closed around the extruded material, because the heating jaw group only transfers heat to the outer surface of the extruded material in the closed position. As is typical with contact heating, an air gap, i.e., a distance between the heating jaw and the outer surface, leads to a drastic drop in heat transfer, so that effective heating of the extruded material is no longer possible in this state.Heating jaw groups that are not enclosed around the strand material are therefore inactive - even when they are heated.

[0010] Furthermore, the temperature to which the extruded material is heated is precisely determined by the temperature of the heating jaws. Unlike infrared heaters, the heating jaws no longer need to be significantly hotter than the target temperature to which the extruded material must be heated. In addition, the heating jaws typically have a much higher heat capacity than the extruded material, so that they cool down negligibly when in contact with the outer surface or can be relatively easily regulated to a constant temperature, namely the target temperature for heating the extruded material. An electric heater is particularly suitable for heating the heating jaws. Heating with heat transfer fluids is, of course, equally viable.

[0011] Opening heating jaw groups can be used in two different ways to reduce the effective, i.e., activated and contacting the shell surface, heating jaw groups compared to the maximum number of possible heating groups, and to bring individual heating jaw groups into the inactivated position, thus shortening the effective heating area compared to the maximum length of the heating area.

[0012] In a first option, at least one heating jaw group is opened or closed individually; that is, the closing drive is designed accordingly. Preferably, the closing drive opens and closes all heating jaw groups individually. To shorten the effective heating area in its axial length compared to the maximum heating area, the closing drive opens at least one heating jaw group and leaves it in the open (inactive) state, while the remaining heating jaw groups are closed for heating (then the activated position). Thus, the effective heating area is shortened by the length of the open heating jaw group(s) compared to the maximum heating area. It is not necessary to move the open heating jaw group(s) away from the extruded material; that is, the open heating jaw group(s) continue to surround the extruded material, but without contacting the outer surface.Only the contacting heating jaw groups are active and contribute to heating the extruded material. Since there are fewer of these than the maximum possible, the effective heating area is axially shorter compared to the maximum heating area. If the length of the maximum heating area is simultaneously designed to correspond to the maximum longitudinal section required for a bend – which is determined by the maximum developed length of a bend to be performed by the bending machine – the heated length can be easily adjusted to the required axial length of the longitudinal section of the next bend to be performed by individually closing one or more heating jaw groups.

[0013] Since the heating jaws are at the temperature required to heat the extruded material, and not much hotter like infrared radiators, the heat output from the open heating jaw(s) is comparatively negligible. Therefore, it is easily possible to maintain the heating jaws at a defined setpoint temperature, regardless of whether they are open or closed. This significantly simplifies the heating process. Furthermore, the continuously heated jaws allow for very rapid adjustment of the axial length of the effective heating area; this simply requires opening the heating jaws to be deactivated or closing the required, i.e., active, heating jaws.

[0014] In a second option, any unused heating jaw group(s) are first opened and then moved away from the extruded material by means of a feed drive. Whether they are subsequently open or closed is irrelevant, as they are never completely enclosed around the extruded material. As a further development of this second option, the closing drive can be designed to actuate all heating jaw groups simultaneously. To adjust the axial length of the effective heating area, all heating jaw groups are first opened, the unused heating jaw groups are moved away by means of the feed drive, and then all heating jaw groups are closed again. Even then, only the heating jaw groups that remain in contact with the outer surface of the extruded material, thus defining the axial length of the effective heating area.

[0015] Since the strand material must typically be heated along a continuous longitudinal section, both options stipulate that the activated heating jaw groups (i.e., those in contact for heating) are all adjacent. This means that only heating jaw groups not located between activated heating jaw groups are moved to the deactivated position (by simply opening them, as in the first option, or by moving them away, as in the second option). For example, if there are four heating jaw groups (I, II, III, and IV), a situation is prevented in which, for instance, only heating jaw groups I and III, I and IV, or II and IV contact the outer surface, and a heating jaw group II and / or III in the deactivated position is located between contacting heating jaw groups.

[0016] The concept of individually activated heating jaw groups, i.e., those contacting the outer surface, allows the effective heating area to be adapted to the required longitudinal section with respect to its axial length. This prevents the extruded material from being heated in sections where it is not intended to be bent. Such a situation would be disadvantageous, as the heated extruded material is flexible and would generally require support when it leaves the bending head. The need for supporting non-bent sections is thus eliminated. Preferentially, only the area that will actually be bent in the subsequent bending process is heated.

[0017] Each heating jaw group can preferably be a heating jaw pair consisting of two heating jaws, but the heating jaw group can also be composed of three or more heating jaws. The heating jaw groups or heating elements have solid metal jaws, e.g., made of copper, and feature a trough-shaped recess for receiving the extruded material to be heated. Particularly preferably, the heating jaws have an interchangeable insert that allows the contact surface to be adapted to the outer surface of the extruded material. This makes it possible to process extruded materials with different cross-sections, e.g., plastic pipes with different outer diameters.

[0018] Due to the heat capacity of the heating jaws, which have a volume many times greater than the extruded material being heated, the heating jaws maintain their temperature even when in contact with the still-cold extruded material. The heating jaws are preferably heated conductively. Furthermore, temperature measurement using thermocouples and / or temperature control of the heating jaws is preferably implemented. Because each heating element is designed as a contact heater, more precise temperature control, and in particular, significantly more precise temperature control of the extruded material, is possible compared to conventional heating methods using thermal radiation and hot air heating. The temperature control is now time-independent; that is, it is completely unproblematic to keep the heating jaws in contact with the outer surface for very long periods. Heating above the target temperature does not occur; rather, the extruded material is always only at the temperature of the heating jaws.This makes it easier to coordinate the operation of the bending machine, because even a preceding bend, which, for example, requires a longer period to cool the extruded material to a stabilizing lower temperature due to a large unwound length, cannot lead to the extruded material being overheated in the next section that has just been heated.

[0019] Preferably, the heating jaws of a heating jaw group can be connected to each other by at least one hinge, so that the closing drive can then move the heating jaws apart or together via the hinge. More preferably, the heating jaws can also be mounted to move along a guide transverse to the longitudinal axis. In this case, too, the heating jaws of the respective heating jaw group can be moved apart or together.

[0020] The optional feed drive is designed to move each heating jaw group towards or away from the extruded material. This can be achieved, for example, by a slide, particularly a pneumatic or electric slide. In this way, the heating jaw groups are positioned towards or away from the extruded material. They can be moved away from the extruded material together to facilitate the movement of the extruded material. Preferably, the feed drive moves the heating jaw groups longitudinally along the extruded material, allowing the distance to the bending head to be adjusted, thus enabling parallel cooling and bending.

[0021] The number of heating jaw groups enclosed around the strand material preferably defines the longitudinal section such that it corresponds to a development length in the bending process, possibly plus an appropriate safety margin.

[0022] All heating jaw groups can have the same axial length, but at least two heating jaw groups can also differ in their axial length. The heating jaw groups can differ in their axial length and, for example, have lengths of 18 mm, 15 mm, 12 mm, etc. This allows for even more precise adaptation of the heating area to the longitudinal section, as the heating jaw groups can be designed with different axial lengths and thus be adapted more flexibly to the longitudinal section. Different heating jaw groups can be provided for combination and variation. Furthermore, some heating jaw groups can be hinged open or closed, while others can be guided transversely to the longitudinal axis as described. The two drives also make it possible to completely extend the heating jaw group(s) out of the engagement area of ​​the bending machine, so that no interfering contours remain in the bending area.

[0023] The heating device has one heat source per heating jaw, e.g., a heating cartridge (e.g., with dimensions 8 x 60 mm and 160 watts). The heating can be regulated to a constant temperature, e.g., using a PID controller.

[0024] Furthermore, a bending machine with the aforementioned heating device for heating a thermoplastic extrusion material is provided. It is understood that the heating device for heating the extrusion material can be used in any of the aforementioned embodiments of the bending machine.

[0025] The bending machine particularly preferably includes a control device which comprises or forms the aforementioned control unit. This control device determines the length of the longitudinal section based on the development length of a bend to be produced and controls the closing drive and, if applicable, also the feed drive in order to adapt the heating area to the longitudinal section.

[0026] In particular, the invention provides a heating device for heating a thermoplastic extrusion material to be bent, comprising several heating elements that define a heating area for the extrusion material extending axially along the longitudinal direction, wherein each heating element is designed as a heating jaw assembly for contact heating, consisting of several heated heating jaws which have contact surfaces that are designed to be complementary to the outer surface of the extrusion material in order to enclose the extrusion material at its outer surface for contact heat transfer, wherein the closing drive opens each heating jaw assembly by moving the heating jaws apart and closes them by bringing the heating jaws together for contact heat transfer, so that the axial length of the effective heating area is determined by the number of heating jaw assemblies closed around the extrusion material.

[0027] Furthermore, a method for heating the aforementioned strand material is provided. In this process, the aforementioned heating device is used, and the heating jaw assemblies of the heating device are opened and closed around the strand material to adjust the axial length of the effective heating area.

[0028] It goes without saying that all previously described variants of the device are equally suitable for variants of the bending machine and the process.

[0029] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawings, which also disclose essential features of the invention. These exemplary embodiments serve only for illustration and are not to be interpreted as limiting. For example, a description of an exemplary embodiment with a plurality of elements or components is not to be interpreted as meaning that all of these elements or components are necessary for implementation. Rather, other exemplary embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different exemplary embodiments may be combined with one another unless otherwise specified. Modifications and variations described for one of the exemplary embodiments may also be applicable to other exemplary embodiments.Because the figures show: Fig. 1 a bending machine with a heating device for heating thermoplastic extrusion material, Fig. 2 a heating device for heating thermoplastic extrusion material, and Fig. 3 a set of several heating jaws with varying axial length and diameter.

[0030] Fig. Figure 1 shows a bending machine 1 for bending plastic pipes 2, which are fed into the bending machine 1 as extruded material along a machine bed 6 over an internal mandrel 7 in a longitudinal direction 4. At the end of the bending machine 1 is a bending head 10, which bends the plastic pipe 2. It is held in a pipe clamp 12 for this bending process. Upstream of the bending head 10 is a heating device 14, which heats the plastic material of the plastic pipe 2 to a target temperature required for it to be bent as intended in the bending head 10. A control device 15, preferably comprising a processor, controls the bending machine 1. The heating device 14 can be moved along the machine bed, i.e., in the longitudinal direction 4, in a controlled manner to adjust the axial distance of the longitudinal section in which the plastic pipe 2 is heated from the bending head.The heating device 14 can be further adapted, as explained below, with regard to the axial length of the longitudinal section in which the plastic tube 2 is heated. The specific design of the bending machine 1 is not relevant for the heating device 14 described below. The only important factor is that a longitudinally extended section of extruded material is heated until it becomes plasticizable.

[0031] The heating device 14 is in one embodiment in Fig. Figure 2 is shown enlarged. It comprises four heating elements in the form of four heating jaw groups 16, 18, 20, 22. Each heating jaw group has two heating jaws – thus, it is designed here as a heating jaw pair. Heating jaw group 16 is formed by two heating jaws 24, 26, heating jaw group 18 by two heating jaws 28, 30, heating jaw group 20 by two heating jaws 32, 34, and heating jaw group 22 by two heating jaws 36, 38. Each heating jaw is preferably constructed in two parts and is formed by a jaw element that sits on a surface heated by a heating cartridge serving as the heat source. For heating jaw 24, the heating cartridge 40 and the jaw element 41 are shown by reference numerals. A one-piece or other multi-part construction is equally possible. For example, the heating cartridge can also be integrated into the jaw element; The separate heating cartridge 40 is then replaced by a carrier or spacer.

[0032] The heating jaw is preferably maintained at a setpoint temperature, for which purpose a temperature sensor (not shown) can be located in or on the heat source (e.g., heating cartridge) or in or on the heating jaw itself, which is connected to the control unit 15 of the bending machine or to a separate control unit of the heating device. In this way, preferably by means of PID control, each heating jaw 24-38 is continuously heated to a setpoint temperature. This is the target temperature to which the plastic tube 2 is to be heated for bending, or a setpoint temperature increased by a certain margin (to allow for any cooling of the tube before / during the bending process).

[0033] Each heating jaw 24-38 has a contact surface, of which the contact surface 42 of the heating jaw 34 in Fig. 2 is designated. They are designed to be complementary to the outer surface 44 of the plastic tube 2, so that each heating jaw group 16-22 is able to completely enclose the plastic tube 2 with the contact surfaces of its heating jaws. However, this contact only occurs for closed heating jaw groups, which is Fig. 2 is given for the heating jaw groups 16 and 18.

[0034] To enable the heating jaw groups 16-22 to be opened or closed individually, each heating jaw group 16-22 is equipped with a drive. This allows, for example, the heating jaws 24 and 26 of heating jaw group 16 to be moved apart by a drive 46 to open the heating jaw group 16, or moved together so that the contact surfaces of the heating jaws 24 and 26 rest against the outer surface 44 and enclose the plastic tube 2 for contact heating. Similarly, a drive 48 moves heating jaw group 18, a drive 50 moves heating jaw group 20, and a drive 52 moves heating jaw group 22. The drives 46-50 are therefore closing drives that can individually open or close the heating jaw groups 16-22.

[0035] In the closed state, the heating jaws of the corresponding heating jaw group are in heat-transferring contact with the outer surface 44 and are therefore active for heating. In the open state, which is shown as an example for heating jaw groups 20 and 22, this is not the case, and this heating jaw group does not heat the plastic tube 2.

[0036] In Fig. 2. The opening path of the closing drives is designed to be large enough to accommodate the pipe wrench 12, thus ensuring that, in the open position, there is no obstruction to the movement of the plastic pipe 2. However, such a large distance is not strictly necessary to bring a heating jaw assembly into a position inactive with respect to its heating effect. A comparatively small distance suffices, since the contact heating relies on thermally conductive contact between the contact surface of the heating jaws and the outer surface 44 of the plastic pipe 2. Only closed heating jaw assemblies, in this case heating jaw assemblies 16 and 18, contribute to the effective heating area; open heating jaw assemblies, here heating jaw assemblies 20 and 22, do not.

[0037] In Fig. Figure 1 shows a different setting of the heating device 14, in which the heating jaw groups 18, 20 of the Fig. 2 are in the activated position, while heating jaw groups 16 and 200 are open and thus in the inactivated position, in which they do not heat the outer surface. It is therefore easily possible to shorten the effective heating area compared to the maximum heating area, which is determined by the combined axial length of all heating jaw groups, by individually opening and closing the heating jaw groups.

[0038] For this reduction to occur, it is sufficient that the heating jaw groups have the same axial length. The axial length of a heating jaw group thus represents a step size by which the maximum heating area can be gradually reduced.

[0039] In the embodiment of the Fig. Figure 2, however, shows a design in which the heating jaw groups 16-22 differ in length from one another, with the length decreasing with increasing reference numeral. The length of the heating area thus decreases in the following sequence of combinations of activated (i.e., closed and in place) heating jaw groups: 16 + 18 + 20 + 22 (maximum heating area); 16 + 18 + 20; 18 + 20 + 22; 16 + 18; 18 + 20; 20 + 22; 16; 18; 20; 22 (minimum heating area).

[0040] In the embodiment of the Fig. Figure 2 shows an additional positioning drive comprising a slide 54, which adjusts a support plate 56 relative to the longitudinal direction of the plastic tube 2. The support plate 56 carries the closing drives 46-52. In this way, after all closing drives have opened, it is possible to move the heating jaw groups 16-22 away from or towards the plastic tube 2. The positioning drive can also be implemented by a robot arm.

[0041] In one embodiment (not shown), the feed drive is designed to individually transport the heating jaw groups 16-22 to the plastic tube 2. Heating jaw groups not contributing to the effective heating area are then preferably retracted from the plastic tube 2. In this case, it is also unnecessary to provide individually adjustable closing drives 46-52; rather, it suffices to open and close the heating jaws of the heating jaw groups collectively. A heating jaw group not contributing to the effective heating area is then closed, but retracted from the plastic tube 2.

[0042] In Fig. 2. It is possible to detach the jaw elements from the heating cartridges by means of screw connections, so that the heating jaws can be easily adapted to the profile of the plastic tube by exchanging the jaw elements.

[0043] The heating jaws 24-38 are preferably heated electrically, e.g., conductively, and particularly preferably by means of a heating coil. In embodiments, the heating jaws 24-38 are designed as solid metal jaws, which, due to their large volume, can be maintained at a consistently uniform temperature. The temperature of the heating jaws 24-38 is maintained in both the open and closed states (preferably controlled), and, due to the large volume difference between the plastic tube 2 and the heating jaw 24-38, it does not change significantly even when the heating jaw assembly 16-22 is closed and thus comes into contact with the outer surface 44 of the plastic tube, which is still cold at that time.

[0044] To adapt the possible effective heating lengths, it is preferred to provide a set 58 of heating jaws that differ with respect to their individual length L and / or with respect to the design of the contact surface 42. Fig. Figure 3 shows such a set 58, where arrow 60 illustrates that the length L of the individual heating jaws of the set 58 decreases in the direction of arrow 60. This naturally affects both the length of the heating cartridge and the jaw element 41. In the direction of arrow 62, the diameter D of the cylindrical contact surface 42 increases. Since the axial length of the heating jaw is not affected by this, the figure shows Fig. 3 schematically in the direction of arrow 62 only one variation of the baking element. By suitable selection from set 58, an individual heating device 14 can be created, from which in Fig.Figure 3 schematically shows only the upper part of the heating jaw groups, which are assembled to be adapted as precisely as possible to a bending task with regard to the different possible combinations and sequences of heating jaws of different lengths. This allows for optimal adaptation to the axial lengths of the longitudinal sections to be bent in the bending task. In the series production of a workpiece, the different heating lengths required are determined, for example, by the control unit.From a combination of different heating lengths, the heating jaw assemblies to be installed on the machine are selected from a predefined set of heating jaw assemblies in such a way that – while adhering to a predefined maximum length exceedance of the achievable lengths across the required heating lengths – a minimum number of the selected heating jaw assemblies is achieved. This also minimizes the interference contour caused by the heating jaw assemblies and the required installation space for the heating jaw assemblies. For example, if the set includes heating jaw assemblies with lengths of 18 mm, 15 mm, 12 mm, 10 mm, and 5 mm, and axial lengths of the longitudinal sections of 5 mm, 8 mm, and 25 mm are required, then, for example, the heating jaw assemblies with lengths of 15 mm, 10 mm, and 5 mm are selected from the set.This example shows that a more precise gradation and adjustment of the heating range in contact heating is achieved by selecting appropriate heating jaw groups from the set for the required heating.

[0045] The heating device 14 can have an independent control unit that communicates with the control unit 15 via a data connection and, in particular, receives information about the length of the longitudinal section in which the next bend is to be executed via an interface. The control unit can then itself determine the heating jaw groups to be activated and control the drive(s) accordingly – a function otherwise performed by the control unit 15. This design can be advantageous depending on the configuration of the bending machine 1, for example, especially if a robot arm carries the heating device 14. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2012 005 973 A1

[0002] EP 3 285 985 B1

[0003] DE 10 2021 131 986 A1

[0004] DE 32 46 845 A1

[0005] DE 10 2018 111 283 A1

[0005]

Claims

[1] Heating device for heating a thermoplastic strand material (2) having a lateral surface (44) which extends along a longitudinal direction (4) and is to be bent in at least one longitudinal section and heated therefor, the heating device comprising: - a plurality of heating elements defining a heating area for the strand material (2) extending axially along the longitudinal direction (4), - a closing drive (46, 48, 50, 52) for opening and closing the heating elements around the strand material (2), - a control unit (15) which controls the closing drive (46, 48, 50, 52) in order to adapt an axial length of an effective heating area to the longitudinal section, characterized by , that - each heating element is designed as a heating jaw group (16, 18, 20, 22) designed for contact heating, wherein each heating jaw group (16, 18, 20, 22) is formed from a plurality of heated heating jaws (24, 26, 28, 30, 32, 34, 36, 38) which have contact surfaces (42) which are shaped complementarily to the outer surface (44) of the strand material (2) in order to enclose the strand material (2) on its outer surface (44) for contact heat transfer, and - the closing drive (46, 48, 50, 52) is designed to open each heating jaw group (16, 18, 20, 22) by moving the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) apart and to close each heating jaw group (16, 18, 20, 22) by bringing the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) together for contact heat transfer, so that the axial length of the effective heating area is determined by the number of heating jaw groups (16, 18, 20, 22) closed around the strand material (2). [2] Heating device according to claim 1, characterized by in that the closing drive (46, 48, 50, 52) is designed to open at least one of the heating jaw groups (16, 18, 20, 22) individually and the control unit (15) is designed to shorten the effective heating area compared to a maximum heating area, which is determined by the axial length of all heating jaw groups (16, 18, 20, 22), by opening at least one of the heating jaw groups (16, 18, 20, 22), wherein this opened heating jaw group (16, 18, 20, 22) continues to surround the strand material (2) - but without contact with the lateral surface (44) - and thus to adapt the axial length of the effective heating area to an axial extent of the longitudinal section. [3] Heating device according to claim 1 or 2, characterized byin that it has a feed drive (54, 56) for moving at least one of the heating jaw groups (16, 18, 20, 22) relative to the strand material (2), and the control unit (15) is designed to shorten the effective heating area compared to a maximum heating area, which is defined by the axial length of all heating jaw groups (16, 18, 20, 22), by opening the at least one heating jaw group (16, 18, 20, 22) and then moving away this at least one heating jaw group (16, 18, 20, 22), and thus to adapt the axial length of the effective heating area to an axial extent of the longitudinal section. [4] Heating device according to one of the above claims, characterized byin that the control unit (15) has an interface for supplying an indication of a length of the longitudinal section in which the strand material is to be bent, and based on the indication, selects the heating jaw groups (16, 18, 20, 22) to be closed around the strand material (2) from the plurality of heating jaw groups (16, 18, 20, 22) and controls the closing drive (46, 48, 50, 52) accordingly. [5] Heating device according to one of the above claims, characterized by that at least two heating jaw groups (16, 18, 20, 22) have a different axial length from one another and the closing drive (46, 48, 50, 52) opens and closes these at least two heating jaw groups (16, 18, 20, 22) individually. [6] Heating device according to one of the above claims, characterized by that the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) have an exchangeable insert (41) in order to adapt the contact surface (42) to the outer surface (44) of the strand material (2). [7] Heating device according to one of the above claims, characterized by , that - the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) of at least one heating jaw group (16, 18, 20, 22) are connected to one another by a hinge, wherein the closing drive opens and closes the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) via the hinge in order to move them apart and bring them together, and / or - the closing drive (46, 48, 50, 52) moves the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) of at least one heating jaw group (16, 18, 20, 22) apart and together along a guide running transversely to the longitudinal direction (4). [8] Heating device according to one of the above claims, characterized by that a heat source (40) heats the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) continuously, ie regardless of whether the heating jaw group (16, 18, 20, 22) is open or closed, to a desired temperature. [9] Bending machine with a heating device for heating a thermoplastic strand material (2) according to one of the above claims. [10] Bending machine according to claim 9, characterized by that a control device (15) of the bending machine (1) comprises or forms the control unit and the control device (15) is configured to determine a length of the longitudinal section on the basis of a developed length of a bend to be produced and to control the closing drive (46, 48, 50, 52) and - in the case of the embodiment according to claim 3 - also the feed drive (54, 56) in order to adapt the axial length of the effective heating region to the length of the longitudinal section. [11] Bending machine according to claim 10, characterized bythat the control device (15) selects the heating jaw groups (16, 18, 20, 22) to be closed around the strand material (2) from the plurality of heating jaw groups (16, 18, 20, 22) based on the length of the longitudinal section and controls the closing drive (46, 48, 50, 52) and - in the case of an embodiment according to claim 3 - also the feed drive (54, 56) accordingly. [12] Heating method for heating a thermoplastic strand material (2) having a lateral surface (44) which extends along a longitudinal direction (4) and is heated in order to be bent in at least one longitudinal section, wherein - a heating device (14) with a plurality of heating elements (38) is used, which defines a heating area for the strand material (2) extending axially along the longitudinal direction (4), and - the heating elements (38) around the strand material (2) are opened and closed in order to adapt an axial length of an effective heating area to the longitudinal section, characterized by , that - each heating element (38) is designed as a heating jaw group (16, 18, 20, 22) designed for contact heating, wherein each heating jaw group (16, 18, 20, 22) is formed from at least two heating jaws (24, 26, 28, 30, 32, 34, 36, 38) having contact surfaces (42) which are complementary to the outer surface (44) of the strand material (2) in order to enclose the strand material (2) on its outer surface (44) for contact heat transfer, - each heating jaw group (16, 18, 20, 22) is opened by moving the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) apart into an inactivated position or closed by bringing the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) together into an activated position for contact heat transfer and the axial length of the effective heating area is determined by the number of heating jaw groups (16, 18, 20, 22) closed around the strand material (2). [13] Heating method according to claim 12, characterized by that the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) are heated continuously, ie in both the activated and inactivated positions. [14] Heating method according to claim 12 or 13, characterized bythat the axial length of the effective heating area is shortened compared to a maximum heating area, which is determined by the axial length of all heating jaw groups (16, 18, 20, 22), by opening at least one heating jaw group (16, 18, 20, 22) surrounding the strand material (2), wherein the opened heating jaw group (16, 18, 20, 22) continues to surround the strand material (2) - but without contact with the lateral surface (44) - and thus the axial length of the effective heating area is adapted to an axial extent of the longitudinal section. [15] Heating method according to claim 14, characterized by that, based on the length of the longitudinal section, the heating jaw groups (16, 18, 20, 22) to be closed around the strand material (2) are selected from the plurality of heating jaw groups (16, 18, 20, 22) and these are brought into the activated position and the remaining heating jaw groups (16, 18, 20, 22) are brought into the inactivated position. [16] Heating method according to one of claims 12 to 15, characterized by that the axial length of the effective heating area is shortened compared to a maximum heating area, which is determined by the axial length of all heating jaw groups (16, 18, 20, 22), by opening at least one heating jaw group (16, 18, 20, 22) and then moving away this at least one heating jaw group (16, 18, 20, 22), and thus the axial length of the effective heating area is adapted to an axial extent of the longitudinal section. [17] Heating method according to one of claims 12 to 16, characterized by that a predetermined set of heating jaw groups of different axial lengths is provided and, taking into account the axial lengths of the longitudinal sections in which bending is to take place, the heating jaw groups to be fitted on the bending machine are selected from the predetermined set of heating jaw groups. [18] Heating method according to one of claims 12 to 17, characterized by that a heating device (14) according to one of claims 1 to 8 or a bending machine (1) according to one of claims 9 to 11 is used.

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