TWISTING DEVICE FOR ELECTRICAL CONDUCTORS

Abstract

A method of twisting electrical conductors includes cutting the conductors to size and transferring them to an actively displaceable twisting head and an oppositely positioned displaceable clamping device; clamping and tensioning the conductors between the twisting head and the clamping device by moving at least the twisting head away from the clamping device; activating the twisting head so that it rotates about an axis of rotation parallel to the clamped conductors while at the same time moving the twisting head towards the clamping device according to prescribed travel profile; applying a force, if need be of different magnitude, directed away from the twisting head to at least the clamping device, at least during the twisting process; and determining and evaluating a travel and/or force profile for the movable clamping device.

Claims

1. A method for twisting electrical conductors (3), comprising the steps of: cutting the conductors (3) to size and transferring them to an actively displaceable twisting head (1) and an oppositely positioned displaceable clamping device, clamping and tensioning the conductors (3) between the twisting head (1) and the clamping device by moving at least the twisting head (1) away from the clamping device, activating the twisting head (1) so that it rotates about an axis of rotation parallel to the clamped conductors (3) while at the same time moving the twisting head (1) towards the clamping device according to prescribed travel profile, characterised by the following steps: applying a force, if need be of different magnitude, directed away from the twisting head (1) to at least the clamping device, at least during the twisting process, and determining and evaluating a travel and/or force profile for the movable clamping device.

2. The method according to claim 1, characterised by motorised displacement of the twisting head (1) away from the clamping device after the conductor (3) has been clamped in place and before the actual twisting process begins, until the clamping device has been moved by a predefined travel distance or a predefined force is exerted, measuring or at least indirect determination of a characteristic value for the length of the conductor (3) from the position subsequently taken up by the twisting head (1), repeating the above steps with a second or any further conductor (3) which is to be twisted together with the first conductor (3), wherein a correction value for cutting the second or any further conductor to length is determined from the measured values or characteristic values.

3. The method according to claim 1, characterised in that the twisting head (1) completes a pre-programmed travel profile towards the clamping device for each conductor type and/or twist parameter while the clamping device is shifted towards the twisting head (1) by the force created by the shortening of the twisted conductor (3) against the effect of a force-generating element.

4. The method according to claim 1, characterised in that the conductors (3) to be twisted are clamped loosely before the start of the actual twisting process, after which the conductors are brought to the required tension after an initial loose twisting by moving the twisting head (1) until the clamping device has been displaced by about half the maximum travel path, wherein the clamping device is subjected to a force away from the twisting head (1).

5. The method according to claim 1, characterised in that the travel profile of the clamping device is evaluated during the twisting, wherein monitoring preferably covers exceeding a predetermined limit for the travel path and the associated rotation, so that a monitoring range can be represented which if required enables a detailed association of events in which the limit values are exceeded with the rotation.

6. The method according to claim 5, characterised in that the travel profile of the twisting head (1) is adapted according to the travel profile of the clamping device, preferably for a definable number of twisting processes with conductors (3) and twist parameters of the same kind.

Description

DESCRIPTION OF THE DRAWING

[0039] The list of reference signs is as much a part of the disclosure as the technical content of the claims and the figures. The figures are described in a logical, interrelated sequence. The same reference signs denote identical components, reference signs with different indices indicate functionally equivalent or similar components.

[0040] In the drawing:

[0041] FIG. 1 is a schematic side view of an exemplary twisting device according to the invention with two twisting heads,

[0042] FIG. 2 is an enlarged individual representation of the twisting device assembly of FIG. 1 with the movable clamping device for path compensation in the fully retracted position,

[0043] FIG. 3 is an enlarged individual representation of the assembly of FIG. 2 in the fully extended position, and

[0044] FIG. 4 shows an example of a pneumatic circuit diagram for actuating the preload element for the clamping device.

DESCRIPTION OF THE EMBODIMENTS

[0045] The twisting device with compensation for theoretical length shortening during the twisting process represented in FIG. 1 has a twisting head 1. A conductor pair 3 to be twisted is held in place on the side opposite twisting head 1 by a second twisting head 5, wherein the two twisting heads 1, 5 may be rotated in opposite directions about a common axis of rotation. A non-rotating clamping device may also be provided instead of second twisting head 5. As a variant, the non-rotating clamping device may also be provided instead of first twisting head 1, in which case the second twisting head 5 is rotated. In principle, twisting of three or more conductors is also conceivable, if the twisting heads 1, 5 and the clamping device, particularly the clamping mechanisms thereof are designed accordingly.

[0046] After conductor pair 3 has been transferred to twisting heads 1, 5, the conductors are initially arranged parallel with each other and the ends thereof are clamped into the grippers of twisting heads 1, 5. As soon as the twisting process is started, the two conductors are wound round each other under the effect of at least twisting head 1, wherein the axial tension should be kept as constant as possible during twisting. However, it may be beneficial to introduce a tensile force that is variable depending on the progress of the twisting process. The twisting process has the effect of shortening the length of twisted conductor 3 between twisting heads 1, 5. Shortening takes place according to a parabolic function depending on the twist revolutions. The number of twist revolutions necessary for the order is approximately equivalent to the length of the twisted conductor 3 (according to the drawing/order) divided by the pitch length. Additionally, about 40% overtwisting must be anticipated, which must then be untwisted.

[0047] The length shortening in the twisting process can be described mathematically with the aid of the variables in the twisting process (e.g., conductor diameter, conductor material, conductor length, number of twist rotations (forwards and then backwards to reduce tension), tensile force during twisting and the twist pitch length that is to be obtained as the result of twisting, etc.). The parameters of the twisting process for a specific configuration of these variable may be stored as a file (the formula). The base data for these formulas is initially calculated in preliminary tests for each conductor cross section. After it has been found, the base data may then serve as the basis for deriving other conductor lengths mathematically.

[0048] The theoretical length shortening is carried out in the twisting process by mounting first twisting head 1 on a length compensation carriage 2, which is movable during twisting according to the required formula actively and preferably on the basis of the twist revolutions via a programmable servo drive unit so as to compensate for the shortening of the conductors 3 to be twisted during the twisting process. Theoretically, the axial tensile force in the conductor pair 3 should remain substantially constant, as is also desirable for most twisting processes. However a variable tensile force profile for twisting might also be programmed on the basis of the suitable formula.

[0049] Second twisting head 5or also the non-rotating clamping deviceis mounted on another linear carriage, a travel compensation carriage 4, which can be subjected to a controllable preload force via an adjustable preload element, which force acts in a direction opposite to first twisting head 1 and parallel to the common axis of rotation of twisting heads 1, 5. Carriage 4 is preferably exposed to a constant tensile force, which is particularly unrelated to the carriage position. The tensile force acting during twisting on conductors 3 via twisting head 1 corresponds to the tensile force acting on travel compensation carriage 4.

[0050] If due to material tolerances in the process for example the shortening dimension of the twisted conductor does not exactly match the reference path of the length compensation carriage programmed in the travel profile and travelled on twister 1, travel compensation carriage 4 should compensate for this path differential on twisting head 5. The tensile force remains the same.

[0051] The preload element may consist of a pneumatic cylinder 6 for example, the working area of which is subjected to a constant pressure that is controllable and unaffected by the piston position. In this way, a defined tensile force may applied to the conductor pair 3 to be twisted in the twisting operation of the entire travel range of length compensation carriage 2 by the equalising effect of travel compensation carriage 4, which is constant for example over the entire travel range of both carriages 2, 4. As is shown in exemplary pneumatic circuit represented in FIG. 4, the pneumatic pressure for supplying cylinder 6 is adjusted from the user interface by means of a programmable pressure regulating valve, preferably a 5/2-way valve 44. The pneumatic system as a whole comprises compressed air source 41, an electropneumatic regulator 43 positioned between the compressed air source and the compressed air reservoir 42, as well as two sound dampers 47 on the outlet openings of valve 44. A plug 45 blocks off a parallel path from valve 44 to cylinder 6. Pneumatic cylinder 6 is supplied with pneumatic pressure on one side, so that the tensile force incident on the piston rod is also incident and constant over the entire travel range of the piston. Tolerances due to materials are compensated for during twisting because twisting head 2 which is now axially movable adapts its axial holding position in keeping with the constant tensile force.

[0052] Alternatively, it is also possible the vary the pneumatic pressure and therewith also the tensile force acting on conductors 3 as a function of the twist rotations, so that for example a lower tensile force is applied at the start of the twisting process, and is increased progressively. Alternative embodiments are also possible, in which the pneumatic pressure and therewith also the preload force of cylinder 6 is operated according to a programmed profile. This also applies to the subsequent untwisting process.

[0053] The twist shortening that is to be compensated for by tolerances only requires a relatively short travel path of the travel compensation carriage 4 mounted underneath twisting head 5, particularly compared with the travel path of length compensation carriage 2 for first twisting head 1, typically in the order of about 40 mm. This can also be seen by comparing FIGS. 2 and 3. If the position of the piston rod, the carriage 4 and twisting head 5,that is to say the twisting head holding positionis monitored by a path sensor 7, it is then possible to monitor the twisting process within normal tolerances quite effectively. Faults and errors outside of this normal twist process lead to a departure from the monitoring tolerance margin. This can also be detected, processed and displayed by an evaluation unit. Further actionscancellation of the twisting process, rejection of the conductor pair as faulty, etc.may also be triggered thereby, thus enabling a monitoring and quality control function. Advantageously, the maximum possible travel path of travel compensation carriage 4 defined by preferably adjustable limit 8a, 8b is kept short than the maximum travel path 8 of length compensation carriage 2.

[0054] According to the invention, therefore, the twisting process is divided into two movements. After conductor 3 has been clamped loosely in the two twisting heads 1, 5, conductor 3 is placed under tension by the servo powered length compensation either immediately or after a loose initial twist until twisting head 5 or another clamping device positioned opposite twisting head 1 has reached approximately halfway in the possible travel path of the travel compensation carriage. Pneumatic cylinder 6 then applies an adjusted, constant force to conductor 3. Then, the twisting is started and the length compensation of twisting head 1 progresses according to a prescribed travel profile, wherein twisting head 1 executes an arithmetically calculated equalisation path to reflect the shortening of the conductors 3 that are being twisted.

[0055] The second clamping device, in this case the second twisting head 5, travels towards first twisting head 1 on a guide (under certain conditions it may also travel away from twisting head 1), wherein the travel path is determined by the force for clamping conductors 3 during twisting preset at preload element 6. Twisting head 5 and the travel compensation carriage 4 that supports it only compensates for small deviations from the ideal, programmed conductor shortening path.

[0056] A displacement sensor 7 or any other transducer in conjunction with second twisting head 5 detects the travel profile thereof during a twist and the deviation of the conductor shortening is calculated in an evaluation unit. For quality monitoring, the travel profile of twisting head 5 for the twisting of conductor 3 is recorded and evaluated. In this way, faulty twisting can be detected throughout the entire operation, and a statistical evaluation is also possible.

[0057] It is also possible to optimise the machine process. For this, the travel profile of the length compensation of twisting head 1 is controlled subsequently in steps taking into account the compensation path of twisting head 5 during the first twists for similar conductors 3 and similar twist parameters.

[0058] Further advantages of the device and method according to the invention explained for exemplary purposes above:

[0059] Capability to monitor twisting with exactly constant tensile force in the automated process.

[0060] Testing/monitoring of the finished twisted length

[0061] Monitoring of shortening due to twist as quality feature

[0062] Very sensitive activation of length correction prevents load peaks in the conductor

[0063] Improved twisting quality through absolutely consistent tensile force in the automatic twisting process

[0064] Tensile force profile programmable in the automatic twisting process, with tensile force correlated to the twist rotations as the twisting process progresses and/or during subsequent untwisting

[0065] Improved detection of incorrect twisting

[0066] The conductors are not overloaded axially during twisting.

[0067] Testing/monitoring of untwisted conductor length

[0068] A variant of the invention provides that travel compensation carriage 4 or any similarly operating arrangement enables automatic calculation of the travel profile for the first twisting head 1. The travel profile typically follows a parabolic function. If the actual values for the initial range of the parabola are known, the entire parabola can be calculated from this.

[0069] According to the invention, two or even three or more conductors 3 to be twisted are cut to size and clamped between twisting heads 1, 5. For this purpose, the length of the conductors is specified beforehand, preferably via a graphical user interface, so that the length compensation carriage 2 can be positioned. The desired tensile force on conductors 3 is then set at the pressure regulator valve 44 of travel compensation carriage 4. Typical values are in the order of about 50 N. Then, carriage 1 is moved back until carriage 4 of twisting head 5 is drawn into the pneumatically regulated travel range by the clamped conductors 3.

[0070] Then, the twisting operation is started at a slow rotating speed of twisting head 1 or twisting heads 1, 5, and continued until carriage 4 reaches the end of its travel path. At the same time the correlation of the travel path to the rotations is detected via displacement sensor 7 of carriage 4. In this way, the actual data is collected for the start of the travel profile parabola. From this data, the parabola can be calculated including the progressive travel profile. In this way, the travel profile for twisting head 1 and length compensation carriage 2 is programmable. The calculated travel profile is based on a relatively small set of actual data, so the deviations of all subsequent twisting operations must be corrected as necessary. The necessary corrections can be determined with the aid of travel sensor 7 of travel compensation carriage 4 and included for purposes of correcting the travel profile parabola.

[0071] A further advantageous application of the invention is the use of travel compensation carriage 4 to make automated comparative measurements of the actual lengths of the two more single conductors 3 that have been cut to length individually one after the other, to ensure that exactly the same length of the conductors 3 to be twisted is present in the twisting area.

[0072] After the first conductor has been cut to length by means of the conductor retraction mechanism and transferred to the grippers in the two twisting heads 1, 5, length compensation carriage 2 is moved away from the opposite clamping device until conductor 3 is taut, and then travel compensation carriage 4 is moved so that the preset tensile force thereof acts axially on single conductor 3. Length compensation carriage 2 is then moved farther, as far as a defined reference point of carriage 4, which is defined as the reference point using a value from travel sensors 7 or a fixed transducer. The travel point reached by length compensation carriage 2 at this point (determined from resolver data from its servomotor) is then stored.

[0073] Length compensation carriage 2 is then retracted to its starting position, wherein the tensile force acting axially on conductor 3 is also reduced to zero and travel compensation carriage 4 returns to its starting position, and the conductor that was measured can be removed or ejected from twisting heads 1, 5.

[0074] The same procedure is then carried out with the second conductor 3. By comparing the travel point positions of length compensation carriage 2 for the first and second and possibly other single conductors 3, the length difference between the two conductors can be calculated. This differential dimension can now be used to correct the operation of cutting conductor 3 to length.