Method for producing a cable end crimp connection

Abstract

A method for producing a crimp connection includes initially guiding a cable end of a cable with a gripper to a crimping press. For this feed movement the gripper is moved by an actuator in an axial direction along the cable axis. The cable end is thereafter connected with a crimp contact. During the crimping process the gripper is, for compensation for length extension of the cable during crimping, moved along the cable axis in a return movement in an opposite direction to the feed movement.

Claims

1. A method for producing a crimp connection comprising the steps of: providing a crimping device including a crimping press and a gripper, a cable having a stripped conductor cable end and a crimp contact; feeding the cable end of the cable to the crimping press with the gripper; and connecting the cable end with the crimp contact by simultaneously crimping with the crimping press while moving the gripper along an axis of the cable in a return movement opposite in direction to the movement during the feeding to provide compensation for length extension of the cable during the crimping.

2. The method according to claim 1, wherein: the gripper includes an actuator configured to move the gripper in an axial direction along the axis of the cable; feeding the cable end of the cable to the crimping press with the gripper includes using the actuator to move the gripper in the axial direction along the axis of the cable; and moving the gripper along an axis of the cable in a return movement opposite in direction to the movement during the feeding includes using the actuator to move the gripper in the return movement opposite in direction to the movement during the feeding.

3. The method according to claim 2, wherein: the actuator is an electric motor configured to apply a predetermined holding moment to the gripper; and using the actuator to move the gripper in the return movement opposite in direction to the movement during the feeding includes activating the electric motor to reduce the predetermined holding moment.

4. The method according to claim 3, wherein: connecting the cable end with the crimp contact includes contacting the crimp contact with a movable press member of the crimping press, the contacting determined by at least one of a travel of the movable press member and a time from which the movable press member executes a lowering movement from a starting position; and using the actuator to move the gripper in the return movement is started or permitted upon contact between the crimp contact and the movable press member.

5. The method according to claim 2, wherein: moving the gripper along an axis of the cable in a return movement opposite in direction to the movement during the feeding includes using the actuator to move the gripper in the return movement opposite in direction to the movement during the feeding using a predetermined compensation value for the return movement.

6. The method according to claim 2, wherein: using the actuator to move the gripper in the return movement opposite in direction to the movement during the feeding includes using a drive power that is reduced compared to a drive power used during the feeding.

7. The method according to claim 2, wherein: moving the gripper along an axis of the cable in a return movement opposite in direction to the movement during the feeding includes measuring and monitoring a tension force on the cable.

8. A method for producing a crimp connection using a crimping press, a gripper for feeding a stripped conductor cable end of a cable to the crimping press, and an actuator for axial movement of the gripper along an axis of the cable, comprising the steps of: providing the cable with the stripped conductor cable end and a crimp contact; feeding the cable end of the cable to the crimping press with the gripper moved by the actuator; and connecting the cable end with the crimp contact by simultaneously crimping with the crimping press while moving the gripper by the actuator along the axis of the cable in a return movement opposite in direction to the movement during the feeding to provide compensation for length extension of the cable during the crimping.

9. The method according to claim 3, wherein: crimping with the crimping press includes measuring a crimping force; and moving the gripper along an axis of the cable in a return movement is started or permitted upon exceeding a predetermined value for the crimping force.

Description

DESCRIPTION OF THE DRAWINGS

(1) Further individual features and advantages of the invention are evident from the following description of an embodiment and from the drawings, in which:

(2) FIG. 1 shows a side view with partly sectional illustration of a crimping device;

(3) FIG. 2 shows a plan view of a feed unit with a gripper for the crimping device according to FIG. 1;

(4) FIG. 3 shows a schematic illustration of a crimping device according to the invention; and

(5) FIG. 4 shows the sequence of a crimping process with graphical illustrations for the press position of the crimping press as well as control signal and holding movement of the servomotor driving the gripper.

DETAILED DESCRIPTION

(6) FIG. 1 shows a crimping device, which is denoted overall by 1, for producing crimp connections. The crimping device 1 comprises a crimping press 2 having a press member 6, which is drivable by way of an electric motor and movable in vertical direction and by which a cable end 11 (FIG. 3) of a cable 3 is connectible with a crimp contact 9. The longitudinal axis of the cable 3 is denoted by x. The press member 6 comprises a carriage, on the underside of which a tool holder is arranged. The tool holder carries a crimping tool at which a crimping die for pressing the crimping contact together with the cable end is arranged. This crimping die co-operates in a mode and manner known per se with an anvil 7 which forms the counter-member relative to the crimping die. With respect to constructional details, reference is made by way of example to the crimping devices shown in EP 1 351 349 A1 or EP 1 447 888 A1. The cable 3 is held by a gripper 4. The gripper 4 has a gripper head with gripper jaws 16, which are movable relative to one another, for gripping the cable 3. The gripper jaws can, for example, be pneumatically actuable. The gripper head with the gripper jaws 16 is mounted to be vertically movable relative to a gripper arm 15 of the gripper 4. In the illustration according to FIG. 1 the press member 6 is disposed in a lowermost position in which the crimp contact 9 has been completely pressed together with the conductor of the cable end of the cable 3. The closing movement of the press member 6 necessary for that purpose is indicated by an arrow k. The gripper head with the gripper jaws 16 can be vertically moved by way of a lowering device 12 rigidly connected with the carriage of the press member 6.

(7) Since the gripper 4 during the crimping process in accordance with the known method is stationary with respect to the cable axis x it can happen that the piece of cable clamped in place between the gripper jaws 16 and crimping tool bulges out as a consequence of the length extension of the cable due to the deformation of the conductor material. This cable bulging of the piece of cable is schematically illustrated in FIG. 1 and denoted by 23. In the case of excessive bulging out it is possible for buckling of the cable to occur, whereby the finished cable counts as faulty and can no longer be used for the intended purpose of use. In order to avoid this, the solution described in the following has been developed.

(8) FIG. 2 shows a feed unit with a gripper 4 for feeding the cable end to a crimping press (not illustrated here). The gripper 4 has a gripper arm 15, at the front end of which the gripper head with the gripper jaws 16 is arranged. The feed movement is indicated by an arrow f. The gripper 4 has an actuator by which the gripper head is reciprocatingly movable in the x direction. This adjusting mechanism for the axial movement of the gripper comprises a drivable pinion 13, which co-operates with a rack 14 attached to the gripper arm 15. In addition, it can be seen in FIG. 2 that the entire gripper 4 is pivotable about a vertical axis. The axial direction x isas apparent in, for example, FIG. 2determined by the cable end. When the cable end is pivoted out, the rear part of the cable can have a different orientation. The x axis also corresponds with the machine axis of the crimping press (cf. FIG. 1). For the pivot movement, the feed device has a drivable pinion 17 and a cogged belt 22. The two motors for the pivot movement and for the axial feed movement (motor 5 shown in FIG. 3) have angle encoders for positional feedback. The opposite direction to the feed movement is indicated by an arrow e. Drawing-off of the insulation during the stripping can also be realized by the gripper 4. The gripper 4 can consequently also be a component of a pull-off axis for an upstream pulling-off process for creating a stripped cable end.

(9) In order to produce the crimp connection initially the cable end 11 of the cable 3 has to be fed by means of the gripper 4 to the crimping press 2. The feed movement in the axial direction x is indicated by the arrow f. The thus-fed cable 3 is now ready for the crimping process. The cable with the previously stripped cable end is disposed in the correct axial position. During the crimping process, in which the press member (not illustrated here) of the crimping press is moved in vertical direction against the cable end and the crimp contact, the gripper for compensation for the length extension of the cable as a consequence of plastic deformation of the conductor during crimping is moved passively or actively along the cable axis of the cable in the opposite direction e to the feed movement. This return movement indicated by the arrow e ensures that undesired buckling out of the piece of cable between the connecting point and place of action by the gripper can be excluded. The undesired effects of the length extension during crimping can thus be avoided.

(10) FIG. 3 shows the crimping device 1 in a highly schematic illustration. The crimping press 2 comprises a vertically movable press member 6, which is drivable by way of the motor 24. The crimping press is equipped with crimping force monitoring means 18 which can detect the crimping force over the travel. The press member 6 is equipped with a force sensor 19 by which the crimping force can be measured. Moreover, it is possible by way of the encoder 20 to detect the travel w for the lowering movement of the press member 6. Signals generated by the sensor 19 and the encoder 20 are sent to the crimping force monitor 18 over a line 21. Additionally or alternatively the crimping press could also comprise a linear measuring system at the press carriage. The gripper 4 can be so activated with the help of the motor control 10 that the gripper 4 for compensation for the length extension of the cable during crimping is axially movable or mobile (compensation mode) in a return movement (arrow e).

(11) FIG. 4 relates to a configuration in which the gripper for compensation for the length extension of the cable during crimping is passively moved in a return movement. The first or upper plot shows the vertical position of the press member of the crimping press (press position w) as a function of time t. The middle plot relates to the activation of the gripper during the crimping process. The control signal for the gripper is denoted by S. Finally, the lower plot shows the holding moment H of the servomotor for the axial movement of the gripper in dependence on time t. At the start to of the crimping process the gripper is axially fixed. Only after a first vertical movement of the press member can the gripper axially move. This time instant is denoted by t.sub.1. The time instant t.sub.1 can be approximately the instant in time of loading of the crimp contact and/or the conductor of the cable by the press member. At the time instant t.sub.1 the servomotor connected with the pinion is instructed by way of a control signal S to reduce the holding moment H from 100% to, for example, 5%. Depending on the respective type of motor and cable to be crimped it could, however, also be sufficient to reduce the holding moment from 100% to 30%. The reduced holding moment now makes possible the desired return movement for compensation for the length extension of the cable during crimping. The control signal is maintained until the time instant t.sub.2 (control at ON) and thereafter the original holding moment is again set (holding moment H=100%). As evident from FIG. 4, the time instant t.sub.2 is located approximately at half the upward movement of the press member 6. The time instant at which the press member is again disposed in its original starting position is denoted by t.sub.3.

(12) Alternatively, an embodiment is also conceivable in which the gripper is actively moved during the crimping process by activation of a drive or actuator. The gripper is in that case advantageously moved through a predetermined compensation travel. Moreover, the gripper in the compensation mode advantageously has to be operated in such a way that the drive power is reduced by comparison with the drive power for the feed process. Finally, for a reliable procedure the tension force on the cable during the return movement for compensation for the length extension of the cable during crimping should be measured and monitored.

(13) In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.