METHOD AND DEVICE FOR STRIPPING A CABLE COMPRISING A MULTI-LAYER SHEATH

Abstract

In a novel method for stripping a cable (3) with a multilayer sheath (5), a first layer (10) of the cable's sheath (5) is first applied to a stripping device (6) with at least one scraper blade (4, 4"). A layer (11) of the sheath (5) located on the inside opposite the first layer is then cut by a laser beam from a laser cutting device (8). The stripping process is completed by peeling the cut sheath (5) using the stripper blade (4, 4") and the laser beam (7).

Description

[0001] The invention relates to a method and a device for stripping a cable with a multi-layer sheathing.

[0002] Simple electrical cables consist of at least one conductor, such as a wire or one or more strands, and an insulating sheath, for example made of PVC. Such cables are typically stripped using mechanically operated stripping devices that include a wire stripper.

[0003] For certain applications, more complex cables are used, whose sheathing has a multi-layered structure. An example of such a cable with a multi-layered sheath is found in... Fig. 2The cable 3 contains an internal electrical conductor 2 consisting of several strands. The strands are encased in a foil 12, for example, made of plastic. The foil 12 can be designed as a shielding foil to create a signal cable. Such shielding foils can be formed by plastic films coated with copper, aluminum, or other metals. The thickness of common shielding foils is approximately 0.03 mm. Another layer 11 consists, for example, of a fiberglass fabric. To protect the cable 3, an outer sheath 10 made of PVC or another electrically insulating elastic base material is provided. In practice, it has been found that cables with multilayer sheaths are difficult to strip using mechanical methods. Cleanly cutting through the fiberglass fabric with wire strippers is hardly possible.Particular problems arise with foil 12, as undesirable damage to the strands can occur when cutting it with wire strippers.

[0004] US Patent 2015 / 162729 discloses a method for stripping a multilayer cable using a laser. In this method, a laser beam rotates around a stationary cable to make a cut in the sheathing. However, it is difficult to adjust the laser so that it completely and cleanly cuts through all layers of the sheathing in a single pass. Alternatively, an incomplete laser cut could be made, and the partially cut sheathing then peeled off. However, in this case, unacceptable contaminants remain on the strands, which must be laboriously removed in a subsequent processing step, for example, with brushes.

[0005] CN 104113016 A discloses a cable stripping machine with a heating chamber, a laser cutting unit, and a stripping unit; US 2010 / 0126665 A1 discloses a laser-based method for stripping fiber optic cables; US 2004 / 182837 A1 relates to a method for stripping flat cables.

[0006] US 5,142,121 A relates to a method for stripping cables. EP 2,887,475 A1 relates to a method and a device for cutting the shielding of a coaxial cable. It is an object of the present invention to avoid the disadvantages of the known methods and to optimize and improve the known methods for stripping cables with multilayer sheathing.

[0007] According to the invention, this problem is solved by a method having the features of claim 1.

[0008] The cable to be stripped can comprise a conductor (for example, a wire or one or more strands made of copper or another electrically conductive metal) and a multi-layered sheath. However, the cable could also be a multi-core cable, in which the individual conductors are surrounded by a multi-layered sheath. The method described below is particularly suitable for round cables. A multi-core round cable is, for example, a cable with a circular cross-section, comprising a sheath forming a ring and twisted conductors arranged in a circle.

[0009] The inventive method for stripping a cable with a multi-layer sheath is characterized in that at least one layer of the cable sheath is mechanically cut or severed at least partially, and at least another layer of the cable sheath is cut or severed at least partially using a thermal cutting process. Cutting methods using knives or blades are preferably employed for mechanically cutting or severing a layer. If, for example, stripping knives are used for mechanical cutting, which are only moved translationally in a radial direction against the cable for the cutting action, it is generally hardly possible to completely sever the respective layer of the sheath for stripping. Although the commonly used stripping knives have cutting geometries adapted to the cable (e.g.,V-blades, form-cutting blades), however, after the cutting process, an uncut area of ​​the layer practically always remains, which is finally separated by tearing during the peeling process. An ideal, evenly distributed cut across the circumference is hardly possible with this method. In contrast, using one or more stripping blades rotating around the cable, the respective layer could be separated across the entire circumference, not just in certain areas. The aforementioned thermal cutting can be achieved, for example, by laser cutting. A laser beam directed at the cable can be moved around the cable with respect to its axis, whereby after a rotation of less than 360° around the cable, only a partial cut of the respective layer or layers would occur.

[0010] The process could include the following steps: cutting a first layer of the cable sheathing with a laser beam from a laser cutting device; cutting an inner layer of the sheathing in a stripping device with at least one stripping knife; and removing the sheathing cut by means of a stripping knife and laser beam.

[0011] The inventive stripping method is characterized by the following process steps: In step a), the first layer of the cable sheath is cut in a stripping device with at least one stripping blade. In step a), the sheath is not completely cut, but only partially. The aforementioned first layer is generally the outermost layer of the sheath, for example, an outer sheath made of PVC or another plastic material for insulation and protection of the cable from the elements. For cutting, the at least one stripping blade can be moved translationally against the cable. Preferably, the direction of movement for the cutting process is radial to the cable. After the cutting process, the at least one stripping blade can be returned to a starting position.The cutting preferably continues until a second layer of the sheathing is reached; the cutting depth of each stripping blade therefore corresponds approximately to the thickness of the aforementioned first layer. However, this second layer need not necessarily be the layer immediately following the outermost layer of the sheathing (such as the outer sheath already mentioned). With the at least one stripping blade, several layers could also be cut simultaneously or sequentially in step a).

[0012] In step b), an inner layer of the cladding, opposite the first layer, is cut by a laser beam from a laser cutting device. The layer to be cut by the laser beam can, for example, be a tissue layer (such as tissue layer 11 according to...). Fig. 2This layer, located inside the first layer, will be referred to as the "second layer" for simplicity. If, in step a), several layers are cut simultaneously or sequentially with the at least one wire stripper, the "second layer" would then be the layer following the aforementioned multiple "first layers".

[0013] To cut the second layer, the laser beam, directed radially towards the cable, can be guided around the cable while the cable is held in place. Alternatively, instead of rotating the laser, it is also conceivable to hold the laser source generating the laser beam in place and rotate the cable around its axis.

[0014] In step c), the sheathing, which has been cut by the stripping blade and laser beam, is finally peeled off, thus ending the stripping process. The peeling according to step c) can be carried out using the aforementioned stripping device by moving the at least one stripping blade in the longitudinal direction relative to the cable. This relative movement for removing the sheathing includes, for example, moving the stripping blade(s) while the cable is held in place, or moving the cable while the stripping blade(s) are held in place. Combinations of the aforementioned movement patterns would also be conceivable.

[0015] After the outer sheath is removed, the conductor is exposed, or—in the case of a multi-core cable—the individual conductors are exposed and can be further processed. For example, the stripped cable ends could be crimped to the exposed conductors. Thanks to the two-stage, or even multi-stage, stripping process, which advantageously combines mechanical and laser stripping methods, multi-layer cables can be stripped easily and efficiently to a high standard. This ensures excellent stripping results; time-consuming post-processing of the cable ends, which can occur with incomplete cuts, for example, is unnecessary.

[0016] If the cable sheath has more than two layers, it can be advantageous to repeat at least one of steps a) and b) before stripping the sheath according to step c). For example, after cutting the first layer with at least one stripping knife and after cutting the second layer with a laser beam, a third layer can be cut with a stripping knife. Alternatively, the third layer could also be cut by the laser beam of the laser cutting device.

[0017] The third layer can be, for example, a foil layer. This foil can have a thickness of less than 1 mm. If the cable is to be used as a signal cable, it must be well shielded electromagnetically to ensure high data transmission quality and to prevent electromagnetic waves radiated by the cable from causing unwanted interference, for example, in the on-board electronics of vehicles. Shielding foils can be used to shield the cable. Such a shielding foil often consists of a plastic film, for example, made of PET, onto which an aluminum layer has been applied. The thickness of common shielding foils is approximately 0.3 mm. However, shielding foils made entirely of a metal such as copper or aluminum are also known. These shielding foils are also known as all-metal foils.

[0018] According to the invention, after step a), the cut first layer is preferably displaced longitudinally relative to the cable by means of at least one stripping blade such that a gap is created to expose the second layer to be cut by the laser beam. This ensures that the laser cut can be carried out precisely and accurately.

[0019] Between the aforementioned steps a) and b), the cable, or the cable end to be stripped, can be transferred from the stripping device to the laser cutting device using a transfer device. This cable transfer can be achieved, for example, by sliding, pivoting, and / or longitudinally moving the cable.

[0020] Particularly preferably, after completion of step b), the cable can be returned to the stripping device by means of the transfer device. By moving the at least one stripping blade of the stripping device longitudinally, the sheathing, which has been completely or only partially cut, can be completely or partially removed. Partial removal of the cut sheathing creates a gap into which the laser beam of the laser cutting device can be directed to cut another layer.

[0021] Another aspect of the invention relates to a device for stripping a cable with a multi-layered sheath, particularly for carrying out the method described above. The device according to the invention comprises a stripping unit with at least one stripping blade and a laser cutting unit. The aforementioned stripping unit with the at least one stripping blade is a mechanically operated stripping unit, which for the sake of simplicity will hereinafter be referred to as the "stripping unit". Individual or multiple layers of the sheath can be selectively cut either in the stripping unit or in the laser cutting unit.

[0022] The stripping unit and the laser cutting unit can be geographically separated. This geographical separation can be achieved, for example, by assigning the stripping unit and the laser cutting unit to separate, unconnected cable processing machines, or by assigning the stripping unit and the laser cutting unit to a common cable processing device (e.g., by arranging them on a common machine table), but by placing the stripping unit and the laser cutting unit next to each other or otherwise apart.

[0023] Particularly in the latter case, it can be advantageous if the device includes a transfer mechanism that allows the cable to be transferred between the stripping unit and the laser cutting unit. However, it would also be conceivable to provide a dedicated stripping station with both a stripping unit and a laser cutting unit, so that the cable does not need to be moved between the individual stripping steps.

[0024] A swivel unit with a gripper for grasping the cable can be used as a transfer device, for example. Longitudinal conveyors such as belt or roller conveyors are also suitable as transfer devices.

[0025] For a cable comprising an outer sheath as the first layer, an underlying fabric layer as the second layer, and optionally a fabric layer or other reinforcing layer as the third layer, the outer sheath is cut in the stripping device with the at least one stripping blade, and subsequently the fabric layer is cut by the laser beam of the laser cutting device. Depending on the layer structure of the cable's sheathing, it might also be necessary to first cut the first layer of the sheathing with a laser beam and only then use the mechanical stripping device with the at least one stripping blade to cut the second layer of the sheathing. With the device according to the invention, it would therefore be possible to carry out the inventive method described above, relating to steps a) and b), in reverse order.

[0026] The device can include a control unit configured and connected to the stripping device and the laser cutting device in such a way that the control unit can be used to control both the cutting process for cutting at least one layer of the cable sheath using the stripping device and the cutting process for cutting at least another or further layer of the cable sheath using the laser cutting device. This arrangement results in a further increase in efficiency. Stripping the cable with its multilayer sheath can be easily automated with the aid of the control unit.

[0027] Preferably, the control device can be connected to the transfer device, wherein the control device is designed to automatically feed the cable from the stripping device to the laser cutting device or from the laser cutting device to the stripping device after completion of a cutting process in the stripping device or in the laser cutting device.

[0028] Further individual features and advantages of the invention will become apparent from the following description of exemplary embodiments and from the drawings. These show: Fig. 1 a top view of a device according to the invention for stripping a cable with a multi-layer sheath, Fig. 2 an enlarged side view of a cable with a three-layer sheath with a stripped cable end, Fig. 3 a cable with a two-layer sheath with the first layer cut by means of stripping knives and shifted to form a gap, Fig. 4 the cable made of Fig. 3 During the cutting of a second layer using a laser beam, Fig. 5 the cable after the laser cutting of the second layer and with the stripping blades retracted, Fig. 6 the fully stripped cable and a two-layer sheathing separated with the stripping blades, Fig. 7 a cable with a three-layer sheathing with the first layer cut by means of stripping blades and shifted to form a gap to expose a second layer, Fig. 8 the cable according to Fig. 7During the cutting of a second layer using a laser beam, Fig. 9 the cable after the laser cutting of the second layer and with the stripping blades retracted, Fig. 10 the cable after the second layer has been moved to form a gap to expose a third layer, Fig. 11 the cable according to Fig. 10 During the cutting of the third layer using a laser beam, Fig. 12 the cable after the laser cutting of the third layer and with the stripping knives retracted, and Fig. 13 the finished stripped cable and a three-layer sheathing cut off with the stripping knives.

[0029] Fig. 1Figure 1 shows a device, designated 1 in general, for stripping multi-layer cables 3. The device 1 has a feed unit 13 designed as a belt conveyor, which moves the cable 3 along a longitudinal direction designated 15, which essentially corresponds to the longitudinal axis of the device 1, to a pivoting unit 9. The pivoting unit 9 has a gripper for holding the cable 3; the gripper allows the cable to be guided in the longitudinal direction 15 to the stripping device designated 6.

[0030] The stripping device 6 is a known stripping station for cutting cables to length and stripping them using stripping knives (not shown here). Such a stripping station is shown and described, for example, in EP 1 515 410 A2; for details regarding the operation and design of the stripping device 6, reference is made to this document. The stripping knives can be designed as V-knives with V-shaped cutting edges. Such V-knives are also known from EP 1 515 410 A2. Alternatively, the stripping knives can be designed as V-knives, as known, for example, from EP 389 107 A1. Of course, knives with other cutting edges and geometries are also conceivable.For separating layers of woven material, especially glass fiber reinforced plastics or textiles, wire strippers with interlocking blades, such as those disclosed in US 6,370,759, have proven effective. Such wire strippers have the advantage that the two blades are forced apart less in the direction of the cable.

[0031] In contrast to the stripping unit 6, which is arranged along the longitudinal axis of the machine, a second stripping station, designated 8, is arranged beside the longitudinal axis of the machine. This stripping station 8 is designed as a laser cutting unit. The cable sheathing can be at least partially cut by means of a laser beam. Details of a possible design of such a laser cutting unit 8 can be found, for example, in US 2015 / 162729.

[0032] The swivel unit 9 is rotatable about a vertical axis. In the illustration according to Fig. 1 The swivel unit 9 is in the swiveled position in front of the laser cutting unit 8. The swivel unit 9 thus clearly forms a transfer device with which the cable 3 can be transferred from the stripping unit 6 to the laser cutting unit 8 (and of course back again) in a single swiveling motion. The two stripping stations 6 and 8 can strip the leading cable ends of the cable 3 in the manner described in detail below. A second swivel unit 9' and a second laser cutting unit 8' are provided for stripping the trailing cable end of the cable 3, with the aforementioned stripping unit 6 also being used for the trailing cable ends.

[0033] The stripping stations 6, 8, 8' are in the embodiment according to Fig. 1The device 1 is arranged on a common machine table or platform 16. The machine table or platform 16 can be designed as a single unit or in multiple parts. The device 1 is designed as a swiveling machine, as is already known and commonly used, for example, in conventional cable processing devices for cable assembly (see, e.g., EP 1 447 888 A1). The device 1 for stripping multilayer cables 3 could, for example, also be designed as a linear transfer machine in which all stripping stations (6, 8, 8') are arranged on a longitudinal machine axis (15). Such a linear transfer machine is known, for example, from EP 1 073 163 A1.

[0034] In Fig. 1Device 1 only includes the aforementioned stripping stations 6, 8, and 8'. However, it would also be conceivable to provide further processing stations. Examples of additional processing stations (not shown here) include crimping stations, crimping stations, and housing assembly stations.

[0035] The device 1 has a control unit 17 which is connected to the stripping unit 6, the laser cutting unit 8, and the swivel unit 9 as a transfer unit. The control unit 17 controls the respective cutting processes in the stripping unit 6 and the laser cutting unit 8. Furthermore, the control unit 17 controls the transfer unit 9 for the necessary transfer of the cable between the stripping unit and the laser cutting unit.

[0036] Fig. 2Figure 1 shows a typical multilayer cable 3, as is commonly used. The cable 3, which comprises a conductor 2, has a multilayer sheath 5, which in this case is composed of three layers. The outermost layer 10, or the first layer from the outside, is an outer sheath 10. This outer sheath 10 can be made of PVC or another flexible plastic material and serves to insulate and protect the cable from the elements. The subsequent second layer, i.e., the layer located inside the first layer 10, is a fabric layer 11 or another reinforcing layer, which can, for example, be a fiberglass fabric. Finally, the third layer of the sheath is formed by a thin film 12, which can be made of a plastic material. The film 12 can also be designed as a shielding film.In this case, conductor 2 consists of several strands, which are usually made of copper or aluminum.

[0037] In the Figures 3 to 6 Individual process steps of a method according to the invention for stripping a cable 3 with a two-layer sheath 5 are shown. The sheath 5 of the cable 3 basically corresponds to the sheath structure of the cable made of Fig. 2 , in contrast to the in Fig. 2 However, the foil (12) is missing from cable 3 shown.

[0038] The corresponding stripping procedure for stripping the cable 3 with the two-layer sheathing 5 is as follows: First, the cable 3 is cut by means of two stripping blades 4 and 14 of a stripping device, which can be moved towards each other. The respective cutting depths are set so that they correspond to the thickness of the outer sheath 10. The cutting is thus carried out until the second layer, which is formed by the fabric layer 11, is reached. The directions of movement for the cutting process are indicated by arrows e 1. After the cut, the stripping blades 4, 14 are moved longitudinally 15 relative to the cable 3. The movement is indicated by arrows f 1. The movement can be effected by moving the stripping blades 4, 14 and / or by moving the cable 3 (for example, by means of the in Fig. 1The aforementioned gripper of the swivel unit 9) is used. The part of the outer shell 10 thus partially removed is designated 10'.

[0039] This displacement creates a gap, exposing the second layer 11 by a gap width s. The creation of this gap with a gap width s allows a laser beam to be applied to cut into the second layer 11. The gap width s depends on the cable being processed and its dimensions, and is typically between 0.1 mm and 1 mm.

[0040] After the outer sheath 10 has been cut and this cut layer or sheath section 10' has been moved within a limited range in the stripping device, the cable 3 can be transferred to a laser cutting device 8 by means of a transfer device (not shown here). The associated Fig. 1The control device (17) mentioned is preferably designed to automatically feed the cable 3 from the stripping device 6 to the laser cutting device 8 after completion of the cutting process.

[0041] The laser cutting process is in Fig. 4 The laser cutting device 8 directs a laser beam 7 radially towards the cable 3. By rotating the cable or by rotating the beam source to generate the laser beam 7 around the cable 3, a circumferential cut is produced, which completely severs the tissue layer 11.

[0042] After the laser beam cuts the second layer 11, the stripping blades 4, 14 are used again. The stripping blades 4, 14 are positioned in the gap between the outer sheaths 10, 10', which are separated by a width s. Fig. 5Figure 6 shows the stripping device with stripping blades 4, 14 positioned as shown. By moving the stripping blades 4, 14 in the f2 direction, the completely cut sheath 10' can now be pulled off the conductor 2. Fig. 6 The fully stripped end of cable 3 is shown. By moving the stripping blades 4, 14, the detached sleeve part of the sheath, labeled 5', was removed from cable 3. The sleeve part 5' consists of the detached sheath part 10' and the detached part 11' of the second layer.

[0043] The Figures 7 to 13 show a method for stripping a cable 3 with a three-layer sheathing 5, which is similar to the one in Fig. 2 The cable shown is set up. Figures 7 to 9 These essentially correspond to the Figures 3 to 5 The cable 3 is first cut using stripping knives 4, 14 and then partially stripped by a gap width s 1 ( Fig. 7), then the second layer 11 is cut by the laser beam 7 ( Fig. 8 ) and then the stripping knives 4, 14 are repositioned in the gap ( Fig. 9 ).

[0044] Now the stripping knives 4, 14 - in contrast to the stripping process according to the Figures 3 to 6 - moved only a small distance in the direction of the longitudinal direction 15 (arrows f 2 ). In this way a gap is created around which the third layer 12 is exposed. Fig. 10 The cable 3 is shown after this displacement movement. The gap width by which the third layer 12 is exposed is in Fig. 11 denoted by s 2.

[0045] Now the laser cutting device can be used again. The laser beam 7 is moved in a rotational motion around the cable 3 and the foil 12 is thus completely cut through ( Fig. 11). After the third layer 12 is cut by the laser beam, the stripping blades 4, 14 are positioned such that they laterally grasp the shoulder of the detached sheath part 10' of the outer sheath created by the stripping blades ( Fig. 12 ). By moving the stripping blades 4, 14 in the f 3 direction, the sheathing can now be completely removed ( Fig. 13 ). The sleeve part 5' obviously consists of three layers, namely the jacket part 10', the part 11' of the second layer and a detached foil part, which is designated 12'.

Claims

1. A method for stripping a cable (3) having a multi-layered sheath (5), comprising the following steps: a) cutting a first layer (10) of the sheath (5) of the cable (3) in a stripping device (6) using at least one stripping blade (4, 4'), b) cutting an inner layer (11) of the sheath (5) located opposite the first layer by means of a laser beam of a laser cutting device (8), and c) removal of the sheath (5) cut by means of the stripping blade (4, 4') and laser beam (7), wherein, after step a), the cut first layer (10) is displaced in such a manner that a split forms to expose the layer (11) to be cut using the laser beam.

2. The method according to claim 1, characterized in that at least one of steps a) and b) is repeated before the removal of the sheath (5) in accordance with step c).

3. The method according to claim 1 or 2, characterized in that between steps a) and b), the cable (3) is transferred from the stripping device (6) to the laser cutting device (8) by means of a transfer device (9).

4. The method according to any of claims 1 to 3, characterized in that after the end of step b), the cable (3) is returned to the stripping device (6) by means of the transfer device (9) and in that by means of a displacement of the at least one stripping blade (4, 4') of the stripping device (6), the cut sheath (5) is partly or fully removed.

5. The method according to claim 4, characterized in that a split is formed by the partial removal of the cut sheath (5), into which split the laser beam of the laser cutting device (8) is introduced in order to cut an additional layer (12).

6. A device (1) for stripping a cable (3) having a multi-layered sheath (5) for carrying out the method according to any of claims 1 to 8, having a stripping device (6) with at least one stripping blade (4, 4'), the device (1) having a laser cutting device (8), and it being possible for one or more layers (10, 11, 12) of the sheath (5) to be selectively cut in the stripping device (6) or in the laser cutting device (8), characterized in that the device (1) has a control device (17), which is designed and which is connected to the stripping device (6) and the laser cutting device (8) in such a manner that, using the control device (17), the cutting process for cutting at least one layer (10, 12) of the sheath (5) of the cable (3) by means of the stripping device (6), the displacement of the layer (10, 12) cut by the stripping device (6) in order to form a split to expose the layer (11) to be cut using the laser beam by means of the at least one stripping blade of the stripping device (6), and the cutting process for cutting at least one different or additional layer (11) of the sheath (5) of the cable (3) is controllable via the laser cutting device (8).

7. The device (1) according to claim 6, characterized in that the device (1) has a transfer device (9) to transfer the cable (3) between the stripping device (6) and the laser cutting device (8).

8. The device (1) according to claim 7, characterized in that the control device (17) is connected to the transfer device (9) and the control device (17) is designed to automatically feed the cable (3) from the stripping device (6) to the laser cutting device (8) or from the laser cutting device (8) to the stripping device (6) after the end of a cutting procedure in the stripping device (6) or in the laser cutting device (8).