METHOD AND DEVICE FOR UNROTATING AND SMOOTHING THE CABLE END OF A TWISTED CABLE

Description

Technical area

[0001] The present disclosure relates to a method and apparatus for untwisting and straightening a cable end of a twisted cable. State of the art

[0002] Twisted pair cables consist of individual wires that are twisted together in a single direction. Twisting significantly improves the cable's signal transmission properties.

[0003] It is sometimes desirable to untwist an end region of the cable, i.e., a cable end. The untwisting process, as used herein, involves removing the individual wires from their mutual entanglement in the limited area of ​​the cable end, thus creating a state in which the individual wires run largely parallel to one another.

[0004] Untwisting may be desirable, for example, when manufacturing a twisted cable, the individual wires are not twisted after assembly, but rather pre-twisted starting material is used for assembly. Assembly typically involves cutting the individual wires to length, stripping, and / or attaching contacts, grommets, etc. at at least one end. Occasionally, assembly requires a cleanly smoothed cable end.

[0005] Untwisting is particularly difficult when the individual wires have a comparatively small cross-section. For example, for individual wires with a small cross-section, special alloys such as copper alloys are used, whose material properties require particularly gentle untwisting.

[0006] DE 44 17 834 A1 discloses a device and method for straightening conductor wire ends. The device comprises a support plate and a straightening plate resting on the support plate. During straightening, the plates are moved toward each other in such a way that one of the two plates is pulled approximately parallel toward the conductor wire end, while simultaneously performing an oscillating back-and-forth movement of the plate approximately transverse to the cable's pull-off direction.

[0007] US 2019 / 103737 discloses an apparatus and method for untwisting and straightening the ends of a twisted pair of wires.

[0008] EP 3 886 273 A1 discloses a untwisting method, but the combined method for smoothing (straightening) conductor wire ends is not disclosed.

[0009] DE 44 17 834 A1 discloses a device and method for smoothing (straightening) conductor wire ends, with oscillating movements and pneumatic stripping cylinders, but the untwisting method is not disclosed. Problems to be solved with revelation

[0010] The known method and device result in a cable end with comparatively high residual ripple, meaning the resulting cable end is not sufficiently smoothed for subsequent assembly. Furthermore, the known method and device are not suitable for reliably untwisting a cable consisting of individual conductors with a comparatively small cross-section.

[0011] It is an object of the present disclosure to provide a device or a method for untwisting and straightening a cable end of a twisted cable, with which reliable straightening is achieved using simple, space-saving means. Solving the problems

[0012] According to the present disclosure, a method according to claim 1 or an apparatus according to claim 9 is provided.

[0013] According to one aspect, a device comprises an untwisting gripper, a clamping gripper, and a cable gripper. The untwisting gripper comprises a first untwisting jaw and a second untwisting jaw, wherein the first and second untwisting jaws can be moved toward one another to hold an inserted cable (i.e., can be closed) and can be moved away from one another (i.e., can be opened) to release or unclamp an inserted cable. The inserted cable is formed from a plurality of individual wires. The individual wires are twisted around a cable longitudinal axis, or cable axis for short, in a twisting direction. The clamping gripper comprises a first clamping plate and a second clamping plate, wherein the first and second clamping plates can be moved toward one another to clamp an inserted cable (i.e., can be closed) and can be moved away from one another (i.e.,can be opened). The clamping gripper is arranged upstream of the untwisting gripper in the cable path of a cable inserted into the device. The cable gripper is arranged upstream of the clamping gripper in the cable path. During movement, the cable is gripped with the cable gripper, in particular automatically gripped. The cable end is inserted, in particular by automatic pivoting and / or automatic movement, between the open clamping jaws and the open untwisting jaws. The clamping plates and the untwisting jaws are closed. The untwisting gripper is rotated in the untwisting direction opposite to the twisting direction of the individual wires of the cable, so that the cable end is untwisted. The untwisting jaws are opened. The distance between the untwisting jaws and the clamping plates along the cable axis is reduced. The untwisting jaws are closed again. A smoothing process of the cable end to smooth the cable end is carried out.The smoothing process comprises simultaneous steps, namely increasing the distance between the cable gripper and the clamping gripper when the cable is clamped and performing oscillating rotary movements of the untwisting gripper.

[0014] In one example, an oscillating rotary movement comprises rotating the untwisting gripper by a first angular amount in a first direction of rotation, i.e., either clockwise or counterclockwise, then rotating the untwisting gripper by a second angular amount in a second direction of rotation opposite to the first direction of rotation, i.e., either counterclockwise or clockwise depending on the direction of the first rotary movement, and then rotating the gripper by a third angular amount in the first direction of rotation. The first angular amount may, for example, be approximately equal to the third angular amount. The second angular amount may, for example, be approximately twice the first angular amount. Then, an oscillating rotary movement according to this example is completed.

[0015] In another example, an oscillating rotary movement comprises rotating the untwisting gripper by a first angular amount in a first rotational direction, i.e., either clockwise or counterclockwise, followed by rotating the untwisting gripper by a second angular amount in a second rotational direction opposite to the first rotational direction, i.e., either counterclockwise or clockwise depending on the direction of the first rotational movement. The first angular amount may be approximately equal to the second angular amount. An oscillating rotary movement according to this example is then completed.

[0016] In yet another example, an oscillating rotary movement comprises rotating the untwisting gripper by unspecified, for example random, values ​​in a first direction of rotation, i.e., either clockwise or counterclockwise, and in a second direction of rotation, i.e., either counterclockwise or clockwise depending on the direction of the first direction of rotation. An oscillating rotary movement according to this example is completed when, from a starting position of the untwisting gripper at the beginning of the smoothing process, the untwisting gripper has passed the starting position once after rotating in the first direction of rotation and in the second direction of rotation and then reaches it again.

[0017] During the straightening process, the cable end is pulled essentially along its entire length through the untwisting jaws, which are closed around the conductors, and the closed clamping jaws. During this process, the untwisting gripper performs oscillating rotations, which are transmitted to the conductors. As a result, the residual ripple at the cable end is reduced, and the individual conductors run largely parallel at the cable end.

[0018] Further training is specified in the dependent claims.

[0019] In embodiments, the oscillating rotary movements of the untwisting gripper are carried out alternately in the twisting direction and the untwisting direction.

[0020] In embodiments, the oscillating rotary movements in the twisting direction and in the untwisting direction are each carried out with less than one revolution of the untwisting gripper, preferably with less than three-quarters of a revolution or with less than half a revolution.

[0021] In embodiments, the rotation of the untwisting gripper in an untwisting direction opposite to the twisting direction for untwisting the cable end is continued beyond complete untwisting of the individual wires of the cable end, in particular by more than half a turn of the untwisting gripper or by more than one turn of the untwisting gripper. Such over-untwisting can be adapted to the elasticity of the individual wires. For example, over-untwisting can be performed for particularly elastic individual wires that have a comparatively high shape memory. Following the over-untwisting, a reversal by the excessive angular amount can be performed to complete the untwisting.

[0022] In some embodiments, the closing force of the clamping plates is reduced before the straightening process. Alternatively or additionally, preferably additionally, the closing force of the untwisting jaws is reduced before the straightening process. The closing force is the force with which the clamping plates or the untwisting jaws act on the cable end. The respective closing force is reduced relative to the processes that precede the straightening process. In particular, the respective closing force can be reduced in such a way that damage to the insulation surrounding the individual wires is prevented when the clamped cable is pulled through the untwisting jaws and the clamping plates during the straightening process.

[0023] In some embodiments, at least three complete oscillating rotary movements are performed during the smoothing process, e.g., three swiveling operations of the untwisting gripper back and forth. In particular, more than five or more than ten complete oscillating rotary movements are performed.

[0024] In embodiments, at least one parameter selected from the following group is specified before the smoothing process: speed when increasing the distance between the cable gripper and the clamping gripper; oscillation speed when performing the oscillating rotary motion; oscillation angle when performing the oscillating rotary motion. In particular, the parameter is automatically specified depending on the type of cable end being inserted, for example, depending on the conductor cross-section, the insulation thickness, the conductor material, the insulating material, and / or the number of individual wires.

[0025] In embodiments, the smoothing process is repeated, for example, once, twice, or more than twice. In particular, to repeat the smoothing process, the clamping plates and the untwisting jaws are opened; the distance between the cable gripper and the clamping gripper is reduced; the clamping plates and the untwisting jaws are closed; and another smoothing process is performed.

[0026] In some embodiments, the untwisting gripper comprises a pneumatic untwisting parallel gripper that supports the untwisting jaws. Alternatively or additionally, the clamping gripper comprises a pneumatic clamping parallel gripper that supports the clamping plates. A pneumatic actuation option is particularly reliable and fast. In this context, the pneumatic untwisting parallel gripper and / or the pneumatic clamping parallel gripper can each include a pressure control valve for specifying a clamping force. This makes it particularly easy to adjust the clamping force for a gentle smoothing process.

[0027] In some embodiments, the untwisting gripper is designed to rotate around the cable axis at a predeterminable, particularly programmable, angle. This allows for particularly simple configuration of the oscillating rotational movement.

[0028] In some embodiments, the clamping gripper is designed to be movable in the cable direction, particularly programmable. This makes it easy to process cables with different untwisted ends.

[0029] Programmable, as used herein, refers to a specification, in particular automatic specification, of the respective value for an automatic sequence control that is adaptable or adapted to the circumstances, for example the specific type and design of the cable end. Short description of the drawings

[0030] Embodiments of the disclosure are explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 (a)-(c) a twisted pair of wires to clarify the terms used herein; Fig. 2 a perspective view of a device according to an embodiment; Fig. 3 a perspective view of parts of the device Fig. 2 ; Fig. 4 a side view of the parts of the device Fig. 2 in a process sequence according to one embodiment; Fig. 5 a side view of the parts of the device Fig. 2 in the course of the procedure; Fig. 6 a side view of the parts of the device Fig. 2 in the course of the procedure; Fig. 7 a side view of the parts of the device Fig. 2 in the course of the procedure; Fig. 8 a side view of the parts of the device Fig. 2 in the procedure.

[0031] In the drawings, like reference numerals designate like or corresponding components.

[0032] Fig. 1shows above in (a) a twisted pair of wires consisting of a first single wire 11 and a second single wire 12. The twisted pair of wires forms a cable 10. The first single wire 11 is wrapped several times around the second single wire 12, specifically along a twisting direction V, so that a twisted or stranded course results along a cable longitudinal axis A (short: cable axis A). The number of single wires in the Fig. 1 The number of individual wires in the example shown is two, but is not limited to two. More than two individual wires can also be twisted into a cable, for example, three, four, or more wires. An end region of the cable 10 with a limited length along the cable axis A is defined as the cable end 15. Examples of the length of the cable end 15 along the cable axis A include a length in the range of a maximum of 10 cm and a minimum of 5 mm.

[0033] In certain applications, it is useful or necessary to untwist the cable 10 from the twisted individual wires 11, 12 at the cable end 15, i.e., to remove the entangled or stranded structure of the individual wires 11, 12 around the cable axis A. One possible reason is that the individual wires 11, 12 should be as parallel to one another as possible and / or as parallel to the cable axis A as possible and / or as smooth as possible in the area of ​​the cable end 15, for example, in order to carry out a termination process. A termination process typically includes one or more of the following steps: cutting to length, stripping, and / or fitting contacts, grommets, etc.

[0034] For untwisting, the individual wires 11, 12 are typically fixed, for example clamped, at the cable-side termination of the cable end 15, and they are rotated at the end termination of the cable 10 opposite to the twisting direction V, thus untwisting, until the mutual entanglement of the individual wires 11, 12 between the end termination of the cable 10 and the cable-side termination of the cable end 15 is eliminated. If necessary, the untwisting can be continued slightly, for example, less than one turn, less than two turns, or less than three turns, beyond the point at which the mutual entanglement of the individual wires 11, 12 between the end termination of the cable end 15 and the cable-side termination of the cable end 15 is eliminated (over-untwisting).

[0035] Following the untwisting or over-untwisting in a method and / or device according to the prior art, a cable 10 according to Fig. 1 in the middle in (b). The individual lines 11, 12 at the cable end 15 have a non-parallel, non-smooth wave structure 13 relative to each other and do not run parallel to the cable axis A.

[0036] In a method and / or device according to the present disclosure, following the untwisting and a smoothing process, a cable 10 according to Fig. 1 below in (c). The individual lines 10, 11 at the cable end 15 have a parallel, smooth structure 14 to each other and run largely parallel to the cable axis A. The cable end 15 comprises, for example, a large part of an area of ​​length a1, which extends from the end termination of the cable 10 (in Fig. 1The term "majority" refers, for example, to more than 80%, typically more than 90% or more than 95% of the length a1 from the end termination of the cable 10 to the first intersection point P1 of the individual lines 11, 12.

[0037] Fig. 2 shows a perspective view of a device 100 according to an embodiment for performing a method described herein. The device 100 is, for example, part of a cable processing machine (not fully shown). The device 100 comprises a cable gripper 130, a clamping gripper 120, and a untwisting gripper 110.

[0038] The cable 10 is held by the cable gripper 130 and can be inserted into the clamping gripper 120 and the untwisting gripper 110 by means of actuators (not shown) in the direction of a processing axis B of the device 100. It is also conceivable for the cable gripper to move the held cable linearly in the direction of the cable axis A. It is also possible for the cable gripper to be attached to a swivel arm (not shown) or to a transfer system (not shown). It is also conceivable for the cable to be inserted into the cable gripper by hand.

[0039] The clamping gripper 120 comprises two clamping plates 121, 122. The clamping plates 121, 122 can be moved toward and away from each other transversely to the cable axis A of a cable inserted into the device, i.e., generally also transversely to the processing axis B, in order to clamp the cable as needed. Generally, the clamping plates 121, 122 are aligned, i.e., they are arranged along the processing axis B with essentially no offset from one another.

[0040] It is understood that the clamping gripper 120 is not limited to two clamping plates 121, 122, and that more than two clamping plates can also be provided.

[0041] The untwisting gripper 110 comprises two untwisting jaws 111, 112. The untwisting jaws 111, 112 can be moved toward and away from each other transversely to the cable axis A of a cable inserted into the device, i.e., generally also transversely to the processing axis B, in order to grip the cable as needed. Generally, the untwisting jaws 111, 112 are aligned, i.e., they are arranged along the processing axis B with essentially no offset from each other.

[0042] It is understood that the untwisting gripper 110 is not limited to two untwisting jaws 111, 112, and that more than two untwisting jaws can also be provided.

[0043] In one example, the untwisting gripper is designed as a pneumatic parallel gripper. The closing force can be adjusted, for example, using a pressure control valve (not shown).

[0044] The rotational axis of the untwisting gripper 110 is aligned with the processing axis B. The untwisting gripper 110 is rotatable about the rotational axis, in particular automatically rotatable and typically rotatable by a predeterminable or predetermined angle, optionally in both directions of rotation (clockwise, counterclockwise when viewed from the cable end). The untwisting gripper 110 can, for example, be rotated with the aid of a Figure 2 The electric drive shown can be rotated around the machining axis B in both directions, each at a programmable angle. Programmable, as used herein, refers to a specification, in particular automatic specification, of the respective value for an automatic sequence control that is adaptable or adapted to the circumstances, for example, the specific type and design of the cable end 15.

[0045] The cable routing refers to the routing of the cable from the terminal end of the cable end 15. The clamping gripper 120 is arranged upstream of the untwisting gripper 110 in the cable routing. The cable gripper 130 is arranged upstream of the clamping gripper in the cable routing. The clamping gripper 120 is thus located between the untwisting gripper 110, which can clamp an area at the terminal end of the cable end 15, and the cable gripper 130.

[0046] Fig. 3 shows a perspective view of parts of the device 100 from Fig. 2 , namely the untwisting jaws 111, 112, the clamping plates 121, 122 and the cable gripper 130. In addition, Fig. 3a clamped cable 10 consisting of two individual lines 11, 12 is shown. In the illustrated embodiment, the cable 10 is linearly movable in the direction of the cable axis A or the processing axis B; the untwisting gripper 110 is stationary; and the clamping gripper 120 is linearly movable at least in the direction of the cable axis A or the processing axis B. It is also conceivable that the cable 10 is not moved; the untwisting gripper 110 is linearly movable at least in the direction of the cable axis A or the processing axis B; and the clamping gripper 120 is linearly movable at least in the direction of the cable axis A or the processing axis B. The movements The Fig. 4 to 8 show a side view of the parts from Fig. 3 the positional relationship of the parts in the process flow of a method according to an embodiment.

[0047] Fig. 4shows a starting position. The cable 10 is held by the cable gripper 130 and introduced into the device 100 and positioned such that the clamping plates 121, 122 of the clamping gripper 120, which is aligned in the direction of the cable axis A and processing axis B, are at the end of the cable end 15 (the beginning of the cable section to be untwisted) and the untwisting jaws 111, 112 of the untwisting gripper 110 are located at the cable-side end of the cable end 15. It can be provided that the cable 10 is aligned before the untwisting process described below, i.e. rotated and / or moved linearly in order to clamp the cable 10 in the correct place and, if necessary, with individual cables 11, 12 already lying next to one another. For example, a camera and image analysis are used for this alignment.

[0048] Fig. 5shows an untwisting process. After the clamping plates 121, 122 and the untwisting jaws 111, 112 are closed, the untwisting gripper 110 rotates against the twisting direction V of the cable 10 by a predetermined or predeterminable angle. The untwisting direction E is in Fig. 5 indicated by an arrow. The angle is generally specified so that the cable end 15 is completely untwisted. This angle can be derived, for example, from the twist pitch (the distance from one intersection point to the subsequent similar intersection point of the twisted wires when viewed from the same direction or in the same plane) and the number of twist turns. Depending on the nature of the individual wires 11, 12, for example, their elasticity, it may be appropriate to twist slightly beyond this angle and then back again (over-untwisting).

[0049] Fig. 6shows the preparation for a smoothing process following the untwisting process. The open untwisting jaws 111, 112 move to the clamping plates 121, 122 and are closed again.

[0050] Fig. 7 shows a smoothing process. The cable end 15 is smoothed as a result of a longitudinal movement of the cable gripper 130, which is indicated by an arrow in Fig. 7is indicated, through the closed clamping plates 121, 122 and the closed untwisting jaws 111, 112. Typically, the cable end 15 is pulled essentially over the entire length a1 of the cable end 15 through the closed clamping plates 121, 122 and the closed untwisting jaws 111, 112. As mentioned above, it is also possible for the cable end 15 to remain stationary while the clamping gripper 120 and the untwisting gripper 110 move, or for the untwisting gripper 110 to pull the cable through the closed clamping plates 121, 122. During this relative movement, or longitudinal movement, the untwisting gripper 110 with the untwisting jaws 111, 112 closed around the individual cables 11, 12 at the cable end 15 carries out several oscillating rotational movements, or pivoting movements, around the cable axis A, ie alternately (oscillating) in the twisting direction V and in the untwisting direction E, as indicated by the double arrow in Fig. 7 shown.

[0051] A speed of the longitudinal movement and / or a pivoting speed of the untwisting gripper 110 and / or a pivoting angle of the untwisting gripper 110 can be specified, for example as predefined or definable process parameters, in particular as a function of the properties of the cable, in a control device (not shown) of the device 100. The process parameters can, for example, be defined, in particular stored, for each cable variant to be processed.

[0052] It is conceivable to reduce the closing force of the clamping plates 121, 122 and / or the closing force of the untwisting jaws 111, 112 before the smoothing process. In particular, the respective closing force can be reduced in such a way that damage to the insulation (not shown) surrounding the individual cables is prevented when the clamped cable is pulled through the untwisting jaws and the clamping plates during the smoothing process. However, the closing force is only reduced to the extent that the clamping plates 121, 122 or the untwisting jaws 111, 112 are still closed, thus clamping the cable 10.

[0053] Fig. 8shows the completion of the smoothing process. The smoothing process is generally complete when the end of the cable end 15 reaches the untwisting gripper 110. Subsequently, the clamping plates 121, 122 and the untwisting jaws 111, 112 are opened, and the cable 10 can be transported further or removed. It is also possible to repeat the smoothing process one or more times by appropriately shifting or moving the cable 10, the clamping plates 121, 122, or the untwisting jaws 111, 112.

[0054] It is understood that the above objects, features, configurations, etc. are exemplary and may be appropriately combined with one another or partially omitted within the scope of the present disclosure.

Claims

1. A method for untwisting and smoothing a cable end (15) of a cable (10), which is formed from a plurality of single lines (11, 12) which are twisted in a twisting direction (V) about a cable axis (A), by means of a device (100), wherein the device (100) comprises: an untwisting gripper (110) having a first untwisting jaw (111) and a second untwisting jaw (112); a clamping gripper (120), which is arranged upstream of the untwisting gripper (110) in the run of the cable, having a first clamping plate (121) and a second clamping plate (122); a cable gripper (130) which is arranged upstream of the clamping gripper (120) in the run of the cable, wherein the method comprises: gripping the cable (10) using the cable gripper (130); introducing the cable end (15) between the open clamping plates (121, 122) of the clamping gripper (120) and the open untwisting jaws (111, 112) of the untwisting gripper (110); closing the clamping plates (121, 122) and the untwisting jaws (111, 112); rotating the untwisting gripper (110) in an untwisting direction (E) counter to the twisting direction (V) for untwisting the cable end (15); opening the untwisting jaws (111, 112), reducing the distance of the untwisting jaws (111, 112) from the clamping plates (121, 122) along the cable axis (A) and closing the untwisting jaws (111, 112); carrying out a smoothing process of the cable end (15) by enlarging the distance between cable gripper (130) and clamping gripper (120) when the cable (10) is clamped along the cable axis (A) and at the same time performing oscillating rotational movements of the untwisting gripper (110).

2. The method according to Claim 1, wherein the oscillating rotational movements of the untwisting gripper (110) are carried out alternately in the twisting direction (V) and untwisting direction (E).

3. The method according to one of the preceding claims, wherein the oscillating rotational movements are carried out in the twisting direction (V) and in the untwisting direction (E), with less than one revolution of the untwisting gripper (110) in each case, preferably with less than one three-quarter revolution or with less than one half revolution.

4. The method according to one of the preceding claims, wherein the rotation of the untwisting gripper (110) is continued in an untwisting direction (E) counter to the twisting direction (V) for untwisting the cable end (15) beyond a complete untwisting of the single lines (11, 12) of the cable end (15), particularly by more than one half revolution of the untwisting gripper (110) or by more than one revolution of the untwisting gripper (110).

5. The method according to one of the preceding claims, further comprising: reducing a closing force of the clamping plates (121, 122) and / or reducing a closing force of the untwisting jaws (111, 112) prior to the smoothing process.

6. The method according to one of the preceding claims, wherein during the smoothing process, at least three oscillating rotational movements are performed, preferably at least five or at least ten.

7. The method according to one of the preceding claims, further comprising: prior to the smoothing process, specifying at least one parameter from a speed during the enlargement of the distance between cable gripper (130) and clamping gripper (120), an oscillation speed when performing the oscillating rotational movements, and an oscillation angle when performing the oscillating rotational movements.

8. The method according to one of the preceding claims, further comprising, after the smoothing process: opening the clamping plates (121, 122) and the untwisting jaws (111, 112); reducing the distance between cable gripper (130) and clamping gripper (120); closing the clamping plates (121, 122) and the untwisting jaws (111, 112); carrying out a further smoothing process of the cable end (15) by enlarging the distance between cable gripper (130) and clamping gripper (120) when the cable (10) is clamped and at the same time performing oscillating rotational movements of the untwisting gripper (110).

9. A device (100) having an untwisting gripper (110) having a first untwisting jaw (111) and a second untwisting jaw (112), a clamping gripper (120), which is arranged upstream of the untwisting gripper (110) in the run of the cable, having a first clamping plate (121) and a second clamping plate (122), and a cable gripper (130), which is arranged upstream of the clamping gripper (120) in the run of the cable, wherein the device (100) is configured for carrying out the method according to one of the preceding claims.

10. The device (100) according to Claim 9, wherein the untwisting gripper (110) has a pneumatic untwisting parallel gripper, which carries the untwisting jaws (111, 112).

11. The device (100) according to one of Claims 9 to 10, wherein the clamping gripper (120) comprises a pneumatic clamping parallel gripper, which carries the clamping plates (121, 122).

12. The device (100) according to one of Claims 10 to 11, wherein the pneumatic untwisting parallel gripper and / or the pneumatic clamping parallel gripper in each case comprises a pressure control valve for specifying a clamping force.

13. The device (100) according to one of Claims 9 to 12, wherein the untwisting gripper (110) is designed for rotating about the cable axis (A) in a specifiable, particularly programmable, angle.

14. The device (100) according to one of Claims 9 to 13, wherein the clamping gripper (120) is designed to be displaceable, particularly displaceable in a programmable manner, in the cable longitudinal direction.