Heating device and heating method for heating a thermoplastic extruded material, and bending machine having such a heating device

Abstract

The invention relates to a heating device for heating a thermoplastic extruded material (2) to be bent, having a plurality of heating elements which define a heating region, extending axially along the longitudinal direction (4), for the extruded material (2), wherein each heating element is designed as a heating jaw group (16, 18, 20, 22) which is formed for contact heating and which consists of a plurality of heated heating jaws (24, 26, 28, 30, 32, 34, 36, 38) which have contact surfaces (42) designed to complement the lateral face (44) of the extruded material (2) in order to enclose the extruded material (2) at its lateral face (44) for contact-based heat transfer, wherein a closing drive (46, 48, 50, 52) opens each heating jaw group (16, 18, 20, 22) by moving apart the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) and closes same by bringing together the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) for contact-based heat transfer such that the axial length of the effective heating region is defined by the number and / or selection of the heating jaw groups (16, 18, 20, 22) closed around the extruded material (2).

Description

[0001] Heating device and heating method for heating a thermoplastic extruded material and bending machine with such a heating device

[0002] The invention relates to a heating device for heating a thermoplastic strand material having an outer profile that extends along a longitudinal direction and is to be bent and heated in at least one longitudinal section. The heating device comprises a heating element that defines a heating region for the strand material that extends axially along the longitudinal direction. Furthermore, the heating device comprises a closing drive for opening and closing the heating element around the strand material and a control unit that controls the closing drive to adapt the heating region to the longitudinal section.

[0003] Such a heating device is known from the generic KR 10 2 443 885 B1, which is manually operated and has a contact heater in the form of a pair of heating jaws for heating a thermoplastic strand material to be bent.

[0004] Another heating device for heating a thermoplastic strand material with an outer profile extending along a longitudinal direction and to be bent and heated in at least one longitudinal section is known from DE 10 2012 005 973 A1. It serves to heat a thermoplastic pipe to be bent. For this purpose, it has several heating elements, each in the form of a tubular sleeve, on the inside of which a plurality of infrared radiators are arranged. Each tubular sleeve can be opened and closed by means of a hinge. This makes it possible to arrange a plastic pipe to be heated in the tubular sleeve, which is then heated by radiant heat along the longitudinal extent of the respective heating element. Several such heating elements can be arranged one behind the other in the longitudinal direction in order to heat the strand material in a longitudinal section with an adjustable length.There is a design conflict with this device. In order to heat the material as quickly as possible, the infrared heaters should be operated at the highest possible temperature. This has the disadvantage that a large amount of heat is generated in the heating device and that sections of the strand material that should not be heated are also heated. In addition, it takes a comparatively long time for the infrared heaters to reach the required temperature when a heating element is switched on again, i.e. when it is moved up to the strand material in an open state and then closed around it. Likewise, it also takes a comparatively long time for the very hot infrared heaters to cool down again when a heating element is opened and moved away from the strand 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 the strand material reaches in the heating element depends on how long the strand material is in the heating element. If the heating time is too long, the strand material can be heated beyond a desired temperature, which may cause damage. After the desired heating time has elapsed, the strand material must therefore be moved as far as possible so that it is out of the area where the heating device is releasing heat. This places restrictions on the other functioning of the bending machine, since, for example, it is not possible to wait for a bend that has just been created to take a long time to cool down.

[0005] EP 3 285 985 B1 discloses a method and a device for bending plastic pipes, wherein a plastic pipe is formed by heating, bending, and cooling. This device uses hot air heating, which also adjusts the temperature over time. A movable pipe heating arrangement realizes 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 and thus represent an unwanted heat source and an interference contour in the further bending process. DE 10 2021 131 986 A1 develops this principle further by allowing the heat emission area of ​​a radiant heater to be finely adjusted using a shielding panel.

[0006] DE 32 46 845 A1 is dedicated to the coupling of a heating cylinder of a plasticizing system to a heat source. DE 10 2018 1 1 1 283 A1 relates to a device for semi-continuous blow molding for producing thermoplastic, hollow blanks. DE 41 08 152 A1 discloses a device for softening plastic pipes using a heating device comprising a heating tube formed from two half-shells.

[0007] It is an object of the invention to provide a device and a method for heating a thermoplastic strand material, wherein time specifications 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.

[0008] The invention is defined in the independent claims. The dependent claims relate to preferred developments.

[0009] A heating device is provided for heating a thermoplastic strand material having a lateral surface. The strand material extends along a longitudinal direction and is to be bent in at least one longitudinal section. It must be heated for this bending. The heating device has a plurality of heating elements which together define a heating region extending axially along the longitudinal direction, in which the strand material can be heated. Each heating element is designed as a heating jaw group, usually as a pair of heating jaws. Each heating jaw group consists of a plurality of heated heating jaws which have contact surfaces which are complementary to the lateral surface of the strand material. The heating jaws of each heating jaw group are designed to enclose the strand material at its lateral surface for contact heat transfer, i.e. to contact-enclose it.Each heating jaw group is therefore designed for contact heating of the strand material over a length determined by the axial length of its heating jaws. The maximum length of the heating area is determined by the combined axial length of all heating jaw groups.

[0010] The heating device also has a closing drive which can open each heating jaw group by moving the heating jaws apart and close them by bringing them together. When brought together, the heating jaws rest against the casing surface for contact heat transfer; they are then in an activated position. The closing drive for opening and closing the heating jaw group around the strand material can thus determine the axial length of the effective heating area through the number and / or selection of heating jaw groups closed around the strand material, because the heating jaw group only transfers heat to the casing surface of the strand material when closed. As is usual with contact heating, an air gap, i.e. a distance between the heating jaw and the casing surface, leads to a drastic drop in heat transfer, so that effective heating of the strand material is no longer possible in this state.Heating jaw groups that are not closed around the strand material are therefore inactive - even if they are heated.

[0011] Furthermore, the temperature to which the strand material is heated is precisely determined by the temperature of the heating jaws. Unlike infrared heaters, the heating jaws no longer need to be much hotter than the target temperature to which the strand material must be heated. Furthermore, the heating jaws generally have a much higher heat capacity than the strand material, so that they cool down negligibly when contacting the outer surface or can be relatively easily regulated to a constant temperature, namely the target temperature for heating the strand material. An electric heater is particularly suitable for heating the heating jaws. Heating with heat transfer fluids is, of course, equally feasible.

[0012] The opening of heating jaw groups can be used in two different ways to reduce the effective heating jaw groups, i.e. activated heating jaw groups contacting the jacket surface, compared to the maximum number of possible heating groups and to bring individual heating jaw groups into the inactivated position and thus shorten the effective heating area compared to the maximum length of the heating area.

[0013] In a first option, at least one heating jaw group is opened or closed individually, i.e. the closing drive is suitably designed for this. Preferably, the closing drive naturally opens and closes all heating jaw groups individually. In order 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, whereas the remaining heating jaw groups are closed for heating (then the activated position). The effective heating area is thus shortened by the length of the open heating jaw group(s) compared to the maximum heating area. For this purpose, it is not necessary to move the open heating jaw group(s) away from the strand material, i.e. the open heating jaw group(s) continue to surround the strand material, but without contacting the outer surface.Only the contacting heating jaw groups are active and contribute to heating the strand material. Since there are fewer of these than the maximum possible, the effective heating area is axially shortened compared to the maximum heating area. If the length of the maximum heating area is simultaneously set to the maximum longitudinal section required for a bend—this is determined by the maximum unwound length of a bend to be performed by the bending machine—the heated length can be easily adapted to the required axial length of the longitudinal section of the next bend by individually closing one or more heating jaw groups.

[0014] Since the heating jaw groups are at the target temperature for heating the strand material and are not much hotter like infrared radiators, the heat dissipation by the open heating jaw group(s) is comparatively negligible. It is therefore easily possible to keep the heating jaws at a defined target temperature regardless of whether they are open or closed. This makes heating considerably easier. Furthermore, the continuously heated heating jaws mean that the axial length of the effective heating area can be changed very quickly; this only requires opening the heating jaw groups to be switched to inactive or closing the required heating jaw groups, i.e. the heating jaw groups to be switched to active.

[0015] In a second option, unused heating jaw group(s) are first opened and then moved away from the strand material using a feed drive. Whether they are then opened or closed is unimportant, as they are by no means enclosed around the strand material. This allows, as a further development of the second option, the closing drive to be designed so that it operates all heating jaw groups simultaneously. To adjust the axial length of the effective heating area, all heating jaw groups are then opened first, the unused heating jaw groups are moved away using the feed drive, and then all heating jaw groups are closed again. Even then, only the heating jaw groups that have not been moved away from the strand material contact the shell surface and determine the axial length of the effective heating area.

[0016] Since the strand material naturally usually has to be heated in a continuous longitudinal section, it is intended for both options that the activated heating jaw groups, i.e. those contacting for heating, are all adjacent, i.e. only heating jaw groups that are not located between heating jaw groups in the activated position are brought into the inactivated position (by simply opening according to the first option or by moving them away according to the second option). If, for example, there are four heating jaw groups I, II, III and IV, a situation is excluded in which, for example, only heating jaw groups I and III or I and IV or II and IV contact the jacket surface and between contacting heating jaw groups there is a heating jaw group II and / or III that is in the inactivated position.

[0017] The concept of individually selected, i.e., activated, heating jaw groups that contact the outer surface allows the effective heating area to be adapted to the required longitudinal section in terms of axial length. This prevents strand material from being heated in sections where it is not intended to be bent. This would be disadvantageous, as the heated strand material is pliable and always requires support when it leaves the bending head. This eliminates the need to support unbent sections. The heating is preferentially directed to the exact area that will be bent in the subsequent bending process.

[0018] Each heating jaw group can preferably be a heating group 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 as heating jaws, e.g., made of copper, and have a groove-shaped recess for receiving the strand 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 strand material. This makes it possible to process strand materials with different cross-sections, e.g., plastic pipes with different outer diameters.

[0019] Due to the heat capacity of the heating jaws, which have a volume many times greater than the strand material to be heated, the heating jaws maintain their temperature even when in contact with the strand material, which is still cold at that time. The heating jaws are preferably heated conductively. In addition, temperature measurement using thermocouples and / or temperature control of the heating jaws is preferably carried out. Because each heating element is designed as a contact heater, more precise temperature control, in particular a much more precise temperature control of the strand material is possible compared to conventional heating by thermal radiation and hot air heating. Temperature control is now not time-critical, i.e. it is completely unproblematic to leave the heating jaws in contact with the casing surface even for a very long period of time. Heating above the target temperature does not occur; rather, the strand material is always only at a maximum temperature of the heating jaws.This makes it easier to coordinate with the operation of the bending machine, because even a previous bend which, for example, requires a longer period of time to cool the strand material to a stabilizing lower temperature due to a large unwound length, cannot lead to the strand material being overheated in the next section that has just been heated.

[0020] Preferably, the heating jaws of a heating jaw group can be connected to one another, for example, by at least one hinge, so that the heating jaws can then be moved apart or brought together by the closing drive via the hinge. More preferably, the heating jaws can also be mounted so that they can move along a guide transversely to the longitudinal axis. In this case, too, the heating jaws of the respective heating jaw group can be moved apart or brought together.

[0021] The optional feed drive is designed to selectively move each heating jaw group toward or away from the strand material. This can be achieved, for example, by a slider, in particular a pneumatic or electric motor-driven slider. In this way, the heating jaw groups are moved toward or away from the strand material. They can also be moved away from the strand material together to enable the strand material to be moved. The feed drive preferably moves the heating jaw groups along the strand material in the longitudinal direction so that the distance to the bending head is adjustable, thereby enabling parallel cooling and bending. The number and / or selection of heating jaw groups enclosed around the strand material preferably defines the longitudinal section such that it corresponds to a developed length in the bending process, if necessary 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 from one another in their axial length. The heating jaw groups can differ from one another in their axial length and have a length of, for example, 18 mm, 15 mm, 12 mm, etc. This enables 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 can therefore be adapted more flexibly to the longitudinal section. Different heating jaw groups can be provided for combination and variation. Some heating jaw groups can also be opened or closed using a hinge, while others can be opened transversely to the longitudinal axis using the guide described. The two drives also enable the heating jaw group(s) to be extended completely out of the engagement area of ​​the bending machine, so that no interfering contours remain in the bending area.

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

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

[0025] Particularly preferably, the bending machine comprises a control device that comprises or forms the aforementioned control unit. This control device determines the length of the longitudinal section based on the developed length of a bend to be produced and controls the closing drive and, if necessary, also the feed drive to adapt the heating area to the longitudinal section.

[0026] In particular, within the scope of the invention, a heating device is provided for heating a thermoplastic strand material to be bent, comprising a plurality of heating elements which define a heating region for the strand material which extends axially along the longitudinal direction, wherein each heating element is designed as a heating jaw group designed for contact heating, which consists of a plurality of heated heating jaws which have contact surfaces which are designed to be complementary to the outer surface of the strand material in order to enclose the strand material on its outer surface for contact heat transfer, wherein the closing drive opens each heating jaw group by moving the heating jaws apart and closes each heating jaw group by bringing the heating jaws together for contact heat transfer, so that the axial length of the effective heating region is determined by the number of heating jaw groups closed around the strand material.

[0027] Furthermore, a method for heating said strand material is provided. The heating device is used, and the heating jaw groups 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 using exemplary embodiments with reference to the attached drawings, which also disclose features essential to the invention. These exemplary embodiments are for illustrative purposes only and are not to be interpreted as restrictive. For example, a description of an embodiment with a large number of elements or components should not be interpreted to mean that all of these elements or components are necessary for implementation. Rather, other embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components of different embodiments may be combined with one another unless otherwise stated. Modifications and variations described for one of the embodiments may also be applicable to other embodiments.Because the figures show:.

[0030] Fig. 1 a bending machine with a heating device for heating thermoplastic strand material,

[0031] Fig. 2 shows a heating device for heating thermoplastic strand material, and

[0032] Fig. 3 a set of several heating jaws with varying axial length and diameter.

[0033] Fig. 1 shows a bending machine 1 for bending plastic pipes 2, which are fed in the bending machine 1 in a longitudinal direction 4 as strand material along a machine bed 6 over an internal mandrel 7. At the end of the bending machine 1 there is a bending head 10, which bends the plastic pipe 2. It is held in a pipe wrench 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 necessary for it to be bent as intended in the bending head 10. A control device 15, which preferably has a processor and a digital data memory, controls the bending machine 1. The heating device 14 can be moved in a controlled manner along the machine bed, i.e. in the direction of the longitudinal direction 4, in order 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 pipe 2 is heated. The specific design of the bending machine 1 is not important for the heating device 14 explained below. It is only important that an elongated section of a strand material is heated to the point of plasticization.

[0034] The heating device 14 is shown enlarged in one embodiment in Fig. 2. 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 – i.e., it is designed here as a pair of heating jaws. The heating jaw group 16 is formed by two heating jaws 24, 26, the heating jaw group 18 by two heating jaws 28, 30, the heating jaw group 20 by two heating jaws 32, 34, and the 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 a heat source. For the heating jaw 24, the heating cartridge 40 and the jaw element 41 are indicated by reference numerals as examples. A one-part or other multi-part construction is equally possible. E.g.The heating cartridge can also be integrated into the jaw element; the separate heating cartridge 40 is then replaced by a carrier or spacer.

[0035] The heating jaw is preferably kept at a set temperature in a controlled manner. For this purpose, a temperature sensor (not shown) may be present, for example, in or on the heat source (e.g. heating cartridge) or in or on the heating jaw itself, which is connected to the control device 15 of the bending machine or an independent control unit of the heating device. In this way, preferably by PID control, each heating jaw 24-38 is permanently heated to a set temperature. This is the target temperature to which the plastic pipe 2 should be heated for bending, or a set temperature that is higher than the target temperature by a certain amount (for any cooling of the pipe before / during the bending process). Each heating jaw 24-38 has a contact surface, of which the contact surface 42 of the heating jaw 34 is designated in Fig. 2.They are designed to complement the outer surface 44 of the plastic pipe 2, so that each heating jaw group 16-22 is capable of completely enclosing the plastic pipe 2 with the contact surfaces of its heating jaws. However, this contact occurs for closed heating jaw groups, which is shown in Fig. 2 for heating jaw groups 16 and 18.

[0036] In order to be able to open or close the heating jaw groups 16-22 individually, each heating jaw group 16-22 is provided with a drive, whereby, for example, the heating jaws 24, 26 of the heating jaw group 16 can be moved apart by a drive 46 in order to open the heating jaw group 16, or can be moved towards one another so that the contact surfaces of the heating jaws 24, 26 rest on the casing surface 44 and enclose the plastic pipe 2 for contact heating. Analogously, a drive 48 moves the heating jaw group 18, a drive 50 moves the heating jaw group 20, and a drive 52 moves the heating jaw group 22. The drives 46-50 therefore represent closing drives which close or open the heating jaw groups 16-22 individually.

[0037] In the closed state, the heating jaws of the corresponding heating jaw group are in heat-transferring contact with the jacket surface 44 and are thus actively 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 pipe 2.

[0038] In Fig. 2, the opening travel of the closing drives is designed to be large enough to allow space for the pipe wrench 12, thus preventing any interference with the movement of the plastic pipe 2 when opened. However, such a large distance is not absolutely necessary to place a heating jaw group in a position inactivated with respect to the heating effect. A comparatively small distance is sufficient for this purpose, since contact heating relies on heat-conducting contact between the contact surface of the heating jaws and the outer surface 44 of the plastic pipe 2. Only closed heating jaw groups, in this case heating jaw groups 16 and 18, contribute to the effective heating range; open heating jaw groups, here heating jaw groups 20 and 22, do not.

[0039] Fig. 1 shows another setting of the heating device 14, in which the heating jaw groups 18, 20 of Fig. 2 are in the activated position, while the heating jaw groups 16, 200 are open and thus in the inactivated position, in which they do not heat the jacket surface. It is thus 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. For this shortening, it is sufficient for the heating jaw groups to have the same axial length.

[0040] The axial length of a heating jaw group therefore represents a step size by which the maximum heating range can be gradually shortened.

[0041] However, the embodiment of Fig. 2 shows a design in which the heating jaw groups 16-22 differ from one another in length; the length decreases with increasing reference numeral. The length of the heating range thus decreases in the order of the following combinations of activated (i.e., closed and engaged) heating jaw groups: 16 + 18 + 20 + 22 (maximum heating range); 16 + 18 + 20; 18 + 20 + 22; 16 + 18; 18 + 20; 20 + 22; 16; 18; 20; 22 (minimum heating range).

[0042] In the embodiment of Fig. 2, an additional feed drive is shown, which comprises a slide 54 that adjusts a support plate 56 relative to the longitudinal direction of the plastic pipe 2. The support plate 56 carries the closing drives 46-52. In this way, after all closing drives have been opened, it is possible to move the heating jaw groups 16-22 away from the plastic pipe 2 or to feed them toward it. The feed drive can also be implemented by a robot arm.

[0043] In one embodiment (not shown), the feed drive is designed to transport the heating jaw groups 16-22 individually to the plastic pipe 2. Heating jaw groups that do not contribute to the effective heating area are then preferably retracted from the plastic pipe 2. It is then also not necessary to provide individually adjustable closing drives 46-52; rather, it is sufficient to open and close the heating jaws of the heating jaw groups collectively. A heating jaw group that does not contribute to the effective heating area is then closed but retracted from the plastic pipe 2.

[0044] 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 pipe by exchanging the jaw elements.

[0045] The heating jaws 24-38 are preferably heated electrically, e.g., conductively, 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 easily and consistently temperature-controlled. The temperature of the heating jaws 24-38 is maintained both in the open and closed state (preferably controlled), and due to the large volume difference between the plastic pipe 2 and the heating jaw 24-38, it does not change significantly even when the heating jaw group 16-22 is closed and thus comes into contact with the outer surface 44 of the plastic pipe, which is still cold at this time.

[0046] In order to adapt the possible effective heating lengths, it is preferable to provide a set 58 of heating jaws which differ in terms of their individual length L and / or in terms of the design of the contact surface 42. Such a set 58 is shown in Fig. 3, wherein the arrow 60 is intended to illustrate that the length L of the individual heating jaws of the set 58 decreases in the direction of the arrow 60. This naturally affects both the length of the heating cartridge and the jaw element 41. In the direction of the arrow 62, a diameter D of the contact surface 42, which is cylindrical in this case, increases. Since the axial length of the heating jaw is not affected by this, Fig. 3 schematically shows only one variation of the jaw element in the direction of the arrow 62. By suitable selection from the set 58, an individual heating device 14, of which FIG.3, only the upper part of the heating jaw groups is shown schematically. These groups are adapted as precisely as possible to a bending task with regard to the various combination options and also the sequences of heating jaws of different lengths in the combination. This allows for optimal adaptation to the axial lengths of the longitudinal sections to be bent in the bending task. During series production of a workpiece, the required different heating lengths are determined, for example, by the control device.From a combination of different heating lengths, the heating jaw groups to be installed on the machine are selected from a predefined set of heating jaw groups in such a way that - while maintaining a predefined maximum length exceeding the achievable over the required heating lengths - a minimum number of selected heating jaw groups is achieved, thus minimizing the interference contour caused by the heating jaw groups and minimizing the required installation space for the heating jaw groups. For example, if the set includes heating jaw groups with lengths of 18 mm, 15 mm, 12 mm, 10 mm, and 5 mm, if, for example, axial lengths of the longitudinal sections of 5 mm, 8 mm, and 25 mm are required, the heating jaw groups 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 for contact heating is achieved by selecting appropriate heating jaw groups from the set for the required heating.

[0047] The heating device 14 can have an independent control unit, preferably with a processor and digital data memory, which communicates with the control device 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 performed via an interface. The control unit can then itself determine the heating jaw groups to be activated and appropriately control the drive(s) – a function otherwise performed by the control device 15. This design can be advantageous depending on the design of the bending machine 1, e.g., particularly when a robot arm carries the heating device 14.

[0048] In principle, the number / selection is, of course, adapted to the length to be heated, which is required for a bend. The control device 15 or the independent control unit determines the number / selection from an indication of this length.

Claims

Patent claims 1. Heating device for heating a thermoplastic strand material (2) which has a lateral surface (44) and extends along a longitudinal direction (4) and is to be bent in at least one longitudinal section and is to be heated for this purpose, wherein the heating device comprises: a plurality of heating elements which define a heating region for the strand material (2) which extends 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 region to the longitudinal section, characterized in 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) consists of 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) at 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) individually by moving the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) apart and to close them 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 and / or selection of the heating jaw groups (16, 18, 20, 22) closed around the strand material (2).

2. Heating device according to claim 1, characterized 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 outer surface (44), and thus adapting the axial length of the effective heating area to an axial extension of the longitudinal section.

3. Heating device according to claim 1 or 2, characterized in 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 determined 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 adapting 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 in 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 in 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 in 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 in 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 bring them together along a guide running transversely to the longitudinal direction (4).

8. Heating device according to one of the above claims, characterized in that a heat source (40) heats the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) continuously, ie independently of whether the heating jaw group (16, 18, 20, 22) is open or closed, to a desired temperature.

9. Heating device according to one of the above claims, characterized in that the control unit is designed to determine or receive an indication of an axial length of a section of the strand material (2) to be heated for bending, to determine the necessary number and / or selection of the heating jaw groups (16, 18, 20, 22) to be closed and to control the closing drive (46, 48, 50, 52) accordingly.

10. Bending machine with a heating device for heating a thermoplastic strand material (2) according to one of the above claims.

11. Bending machine according to claim 10, characterized in 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 based on 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.

12. Bending machine according to claim 11, characterized in that 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.

13. 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 region 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 region to the longitudinal section, characterized in that each heating element (38) is designed as heating jaw groups (16, 18, 20, 22) designed for contact heating, wherein each heating jaw group (16, 18, 20, 22) consists of at least two Heating jaws (24, 26, 28, 30, 32, 34, 36, 38) are formed, which have contact surfaces (42) which are designed to be 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 contacting heat transfer, each heating jaw group (16, 18, 20, 22) is opened individually 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 contacting heat transfer and the axial length of the effective heating area is determined by the number and / or selection of the contact surfaces (42) closed around the strand material (2). Heating jaw groups (16, 18, 20, 22) are determined.

14. Heating method according to claim 13, characterized in that the heating jaws (24, 26, 28, 30, 32, 34, 36, 38) are heated continuously, ie in the activated and inactivated positions.

15. Heating method according to claim 13 or 14, characterized in that the axial length of the effective heating region is shortened compared to a maximum heating region, 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 outer surface (44) - and thus the axial length of the effective heating region is adapted to an axial extent of the longitudinal section.

16. Heating method according to claim 15, characterized in 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.

17. Heating method according to one of claims 13 to 16, characterized in 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.

18. Heating method according to one of claims 13 to 17, characterized in 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.

19. Heating method according to one of claims 13 to 18, characterized in that an indication of an axial length of a section of the strand material (2) to be heated for a bend is determined, a necessary number and / or selection of the heating jaw groups (16, 18, 20, 22) to be closed is determined and the heating jaw groups (16, 18, 20, 22) are closed accordingly.

20. Heating method according to one of claims 13 to 19, characterized in that a heating device (14) according to one of claims 1 to 9 or a bending machine (1) according to one of claims 10 to 12 is used.

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