ELECTRICAL HARNESS FABRICATION

Abstract: Method and apparatus for fabricating an electrical cable harness consisting of a plurality of insulated electrical conductors (80) terminated to electrical connectors (40) is described. The harness (32) is formed in a generally vertical plane, with the harness growing in a downward direction. Upon termination of the final connector (80), a cable portion (34) is left remaining so as to project beyond the trailing end of the cable harness (32). This cable portion (34) comprises a test tab which is then partially stripped at a stripping station 22 (see Fig. 1) so as to bare the electrical conductors thereof. The harness is then advanced to an electrical testing station (24) (Fig. 1) which generates an output signal indicating the test results. If the results are favorable, the test tab (34) is severed from the cable harness at a severing station (26). However, if the test results indicate a shorted condition, a ready visual indication thereof is provided by leaving the test tab (34) attached to the cable harness.

Description: The present invention pertains to improved methods and apparatus for fabricating electrical harness of the type comprising a plurality of electrical connectors terminated to a common plurality of insulated electrical conductors. Manufacturers of electronic and electrical products today employ electrical harnesses having mass termination connectors with insulation displace­ ment type electrical contacts. One particular type of harness in use today is the "daisy-chain" cable harness having several connectors terminated to a common cable segment. One example of an apparatus for conveniently forming daisy-chain harnesses is described in one European patent application No.86 30 2908.8 filed 18th April 1986. In that application, an apparatus is described for terminating a plurality of mating pairs of electrical connector parts to a continuous flat cable segment. Termination is accomplished by compressing a predetermined cable portion betwen a pair of connector parts, one of which has a plurality of insulation displacing terminals positioned therein. Each connector part is located on a rotatable indexing turret, the turrets being movable toward each other to effect termination. In the preferred embodiment, the cable is advanced past the turret in a vertical direction, with the resulting partially formed cable harness being advanced downwardly past the turret. Eventually, after termination of the final connector, the cable harness is cut free for transport to a remote location. The above-described cable harness apparatus is fully automated, for economy of manufacture. It is an object of the present invention to provide a method and apparatus for testing electrical harnesses in a fully automated fashion. The present invention provides a method of fabricating a double-ended electrical harness including a plurality of insulated electrical conductors terminated to first and second electrical connectors. The method includes the steps of terminating a first portion of the conductors to the first connector at a termination station, advancing the terminated first connector past the termination station to present a second portion of the conductors to the termination station, and terminating the second portion of the conductors to the second connector at the termination station. The conductors are cut a predetermined distance beyond the second connector at or after the second termination step to form an intermediate harness product having a test tab consisting of a portion of said insulated electrical conductors projecting beyond said second connector. Said intermediate harness product is then advanced along a delivery track extending past conductor stripping, testing, and trimming stations which strip at least a portion of the insulated conductors of the test tab, test the cable harness by wiping the stripped electrical conductors against a test probe so as to perform electrical testing thereon, generating an output signal in said test probe indicative of desired and undesired conditions of said test result, and trim said intermediate harness in response to the output signal to form a finished harness. The present invention also provides a double­ ended harness fabrication machine that terminates a plurality of insulated electrical conductors to first and second electrical connectors. The machine comprises a termination station, means for terminating a first portion of the conductors to the first electrical connector at the termination station, means for advancing the terminated first connector past the termination station to present a second portion of the conductors to the termination station, means for terminating the second portion of the conductors to the second connector at the termination station, means for cutting the conductors a predetermined distance beyond the second connector to form an intermediate harness product having a test tab consisting of a portion of the insulated electrical conductors projecting beyond the second connector, a conductor stripping station for at least partially stripping the insulated conductors of the test tab, a testing station including a test probe for testing the harness product by wiping the stripped electrical conducts thereof as said harness product is advanced therepast, generating an output signal indicative of desired and undesired conditions of the test results, a selectively actuable trimming station trimming the conductors adjacent the second connector to form a double-ended cable harness, in response to said output signal from said testing station, a delivery track, and means for advancing said harness product from said termination station along said delivery track to said stripping, testing and trimming stations. One way of carrying out the present invention will now be described by way of example and not by way of limitation with reference to drawings which show one embodiment of apparatus according to the present invention for performing a method of the present invention. In the drawings, wherein like elements are referenced alike, FIG. 1 is a plan view of the electrical cable harness testing and delivery apparatus of the present invention showing harness ejection, strip, test, and cable trimming stations; FIG. 2 is a cross sectional elevational view taken along the lines 2-2 of FIG. 1; FIG. 3 is an elevation view of the cable stripping station of FIG. 1; FIG. 4 is an elevation view of the short test station of FIG. 1; and FIG. 5 is an elevation view of the cable trimming station of FIG. 1. Referring now to the drawings, and initially to FIG. 1, a machine for fabricating cable harnesses is generally shown at 10 comprising four work stations 20, 22, 24 and 26. Briefly, an intermediate cable harness product 30 is formed above the first eject and delivery station 20, and is ejected along a delivery track 28 communicating between all four work stations. The intermediate cable harness product 30 consists of a cable harness 32, and a protruding cable portion or test tab 34 used for testing. The cable harness product is then advanced to the second work station 22 where the electrical insulation is stripped from the conductors of the test tab portion of the cable. Thereafter, the intermediate cable harness product is advanced past the third work station 24 where the harness is electrically tested. The protruding test tab portion of the intermediate cable product is then selectively removed at the fourth work station 26. Referring now to FIGS. 1 and 2, the first work station 20 will be described in greater detail. The electrical cable harness is formed above eject station 20 according to the principles shown and described in our European patent application No. 86 30 2908.8 filed 18th April 1986 the disclosure of which is herein incorporated by reference. Briefly, insulated electrical conductors 40 are stored on a reel 42 and are paid out in a downward vertical direction indicated by arrow 44. Conductors 40 pass through a conventional cable feed mechanism 46 and a cable guide 48 so as to enter a termination station 50 where they are compressed between two mating connector parts 52, 54. The first connector part 52 has a plurality of insulation displacing terminals, and the second connector part 54 is a mating cover which provides a compressive terminating force and an alignment between conductors 40 and the terminals of conductor part 52. A first termination head 56 carries the first connector part 52 and an opposed termination head 58 carries the second connector part 54. Termination heads 56, 58 are mounted on respective indexing turntables 60, 61. As described in the above mentioned European patent application, turntable 60 and the termination head 56 is moveable between a connector loading station, not shown in the figure, and termination station 50. Upon loading of the two connector parts 52, 54, and the feeding of conductors 40 so that a predetermined first conductor portion is presented to termination station 50, actuator 62 is energized to extend plunger 64, thereby extending termination head 56 toward the opposed termination head 58. Accordingly, the conductors 40 are compressed between the connector parts 52, 54 so as to effect termination of conductors 40 therebetween. Upon termination, heads 56, 58 are retracted and conductors 40, along with the first terminated connector assembly, is advanced downwardly so that a second predetermined conductor portion is presented to termination station 50. Thereafter, the termination cycle described above is repeated as many times as needed to form the desired daisy-­ chain harness, as explained in said European patent application No. 86 30 2908.8. Upon termination of the last connector assembly for a given harness configuration, the two opposed turntables are indexed to present cable cutting knives to termination station 50. With a compression stroke similar to that required for cable termination, the conductors 40 are effectively severed at station 50. However, as contemplated by the present invention, upon termination of the final connector assembly, termination heads 56, 58 are retracted and conductors 40 are again fed a predetermined amount so as to form the conductor test tab 34 which protrudes beyond the final electrical connector of a given harness assembly. The cable cutting operation thereby forms test tab 34, while freeing the resulting intermediate harness product for further processing. With reference to the lower portion of FIG. 2, the emerging cable harness is fed downwardly past eject station 20, which is provided with a pair of opposed extensible gripper arms 72, 74 which are actuated by solenoids 72', 74', respectively. Solenoids 72', 74', are activated to close the gap between gripper arms 72, 74 through which the cable harness descends (either under the force of gravity, or a positive feed system). Gripper arms 72, 74 provide a reference stop surface for the final connector of intermediate harness product 30. As can be seen in the lower portion of FIG. 2, the section line A-A is taken between termination station 50 and the eject and delivery station 20. This section A-A comprises the right hand portion of FIG. 1, the termination station 50 and its associated subassemblies being omitted for purpose of clarity. Referring now to the right hand portion of FIG. 1, the final electrical connector designated by the numeral 80, which appears at the trailing end of intermediate harness product 30, is shown captivated between gripping arms 72, 74. When in their closed position, gripping arms 72, 74 comprise a slotted delivery track extension portion 82 which mates with the aforementioned delivery track 28. As indicated in FIG. 1, the section 2-2 is taken to one side of eject and delivery station 20, so that a portion of delivery track 28 appears in the cross-section of FIG. 2. With reference to that cross section, delivery track 28 can be seen to comprise a pair of spaced-apart rail portions 86, 88 forming an intermediate slot 90 for receiving the trailing portion of intermediate harness product 30. Slot 90 can be configured to receive either a portion of conductors 40, or a portion of connector 80. In either event, the trailing end of intermediate harness product 30 is confined to slide along rails 86, 88. Referring again to the lower portion of FIG. 2, endless drive belts 92, 94 are disposed within rails 86, 88 so as to communicate with slot 90. Drive belts 92, 94 engage the trailing end of intermediate harness product 30 so as to drivingly engage the product for lateral advancement along delivery track 28. In the preferred embodiment, the drive belts engage connector 80, although conductors 40 could also be engaged to provide lateral transport. At station 20 (see Fig.1), a solenoid 96 is energized to extend ejector member 98, thereby laterally ejecting connector 80 and intermediate harness product 30 from track portion 82 onto delivery track 28, whereupon drive belts 92, 94 engage intermediate harness product 30 for lateral advancement toward second station 22. Referring now to FIGS. 1 and 3, the second work station generally indicated at 22 is seen to comprise a pair of notched stripping blades 100, 102, mounted for reciprocation transverse to connectors 40 by their associated solenoids 104, 106. Upon closing or blades 100, 102 so as to at least partially sever the electrical insulation of conductors 40, a third solenoid 108 is energized to raise the stripping blades 100, 102 (and their associated apparatus) in a direction away from connector 80 so as to at least partially strip conductor test tab portion 34. Solenoids 104, 106 and blades 100, 102 are attached to a unitary support structure generally indicated at 110, mounted for reciprocation in a vertical direction along guide pins 112, 114. Upon being raised, blades 100, 102 are retracted, and an associated gripping apparatus for holding connector 80 against the lifting force of solenoid 108 (not shown in the drawings) is released, so as to release intermediate harness product 30 for further travel toward the third working station 24. Referring now to FIGS. 1 and 4, the third electrical testing station shown generally at 24 comprises a pair of adjacent electrically separated test probes 120, 122 which wipe against the stripped portion of test tab 34 as intermediate harness product 30 is advanced past station 24. In the preferred embodiment, test probes 120, 122 measure the electrical resistance between a pair of adjacent conductors 40, and generate an electrical signal proportional to the measured resistance, at output terminals 124, 126. Test probes 120, 122 are spaced-apart a predetermined distance approximately equal to the center line spacing of conductors 40, such that test probe 120 contacts one stripped conductor, while probe 122 wipes against its immediately adjacent neighbouring conductor. By measuring the resistance between a pair of immediately adjacent conductors, the presence and absence of an electrical short in the intermediate harness product 30 can be detected. For example, at the ouput terminals, a high resistance indicates a desirable absence of a short, and a lower resistance indicates the undesired presence of a short between adjacent conductors of the cable harness. As will be seen immediately below, if a desired absence of an electric short is indicated at output terminals 124, 126, the output signal causes control unit 127 to generate a permissive command at the fourth work station 26 so as to sever the test tab 34 from the intermediate harness product 30, to thereby finish the fabrication of a harness 32. Alternatively, if an undesired presence of a short is indicated in an intermediate harness product 30, control unit 127 generates an interlock signal responsive to the low resistance signal at output terminals 124, 126, to prevent severing of test tab 34 so that, upon presentation of the intermediate harness product to a final delivery station, a ready visual indication of the undesired test result will be apparent to an operator. Although the above-described test station employs resistance measuring equipment, other electrical testing arrangements can be employed. For example, a ground plane could be positioned between the probes 120, 122 and the anvil 128 supporting stripped conductors 40, so that the capacitance between adjacent conductors and between the conductors and the ground plane can be measured. Alternatively, probe 120 could be energized with a test voltage, and the presence or absence of the test voltage or a portion thereof could be detected at the upstream probe 22. In either event, regardless of the electrical test result, the intermediate harness product 30 is transferred to the fourth work station generally indicated at 26, for selective severing of conductor tab portion 34. Referring now to FIGS. 1 and 5, work station 26 can be seen to comprise a moveable cable trimming blade 130 which is driven against an anvil portion 132 by a solenoid 134. In the preferred embodiment, intermediate harness products 30 are transported two-at-a-time along the cable harness machine 10 and accordingly, a duplicate set of severing blades, anvil portions, and solenoids are provided at the fourth work station 26, indicated by numerals 130', 132' and 134', respectively. Conductors 40 are passed through the gap 136 formed between cut-off blade 134 and anvil portion 132. If an undesired electrical test result is indicated at output terminals 124, 126, an interlock signal is generated, preventing actuation of solenoid 134. Accordingly, intermediate harness product 30 is allowed to pass through the fourth work station 26 with the test tab 34 remaining attached, providing a ready visual indication of the undesired test result. However, if the desired test signal is generated at the third work station 24, a permissive actuation signal is applied to solenoid 134 so that severing blade 130 severs the conductors or test tab 34 immediately adjacent the connector 80, to provide a ready visual indication of the desired test result generated at the third work station 24. Referring again to FIG. 5, fourth work station 26 can be seen to comprise a conventional lever arm assembly interconnecting the armature 140 of solenoid 134 and the pivotal mounting 142 of severing blade 130. Also shown in FIG. 5 is a moveable stop pin 144 raised and lowered by solenoid 146 to provide a convenient stop surface blocking the path of the connector along the delivery track, providing relative alignment between the connector 80 and severing blade 130. As can be seen from the above, a completely automated testing and harness delivery system is provided in the cable harness machine described with reference to the drawings. The harness is conveniently electrically tested, and a ready visual indication of the test results is imparted to the harness assembly. Although the harness delivery system is shown mounted in a vertical plane, a similar arrangement, horizontally oriented, could be provided according to the present invention. Also, crimp or pierce type terminals could be employed in the termination of the electrical connectors to the conductors 40 which could be separately formed.

Claims: 1. A method of fabricating a double-ended electrical harness including a plurality of insulated electrical conductors terminated to first and second electrical connectors characterised by the steps of: terminating a first portion of the conductors to the first connector at a termination station, advancing the terminated first connector past the termination station to present a second portion of the conductors to the termination station, terminating the second portion of the conductors to the second connector at the termination station, cutting the conductors a predetermined distance beyond the second connector at or after the second termination step, to form an intermediate harness product having a test tab consisting of a portion of said insulated electrical conductors projecting beyond said second connector; advancing said product along a delivery track which extends past conductor stripping, testing, and trimming stations; stripping at least a portion of the insulated conductors of the test tab; testing the harness by wiping the stripped electrical conductors against a test probe so as to perform electrical testing thereof; generating an output signal in said test probe indicative of desired and undesired conditions of said test result; and actuating said trimming station in response to the output signal to form a finished harness. 2. The method of claim 1 wherein said testing step comprises the step of testing successive pairs of adjacent harness conductors by measuring the electrical resistance therebetween, whereby the presence of an undesired shorting condition and a desired absence of a shorting condition is detected. 3. The method of claim 1 wherein said step of advancing said intermediate harness product comprises engaging an external surface of said second electrical connector with an endless drive belt disposed in said track so that said test tab projects beyond said track, being rendered accessible to said test probe. 4. The method of claim 1 further comprising the step of preventing actuation of said trimming station, in response to an undesired test condition output signal at said testing station. 5. The method of claim 3 wherein said terminated connectors are advanced downwardly past the termination station at least partially under the force of gravity, and said product is advanced in a direction along the delivery track generally transverse to the length of said intermediate harness product, so that substantial portions of said product are maintained beneath said delivery track so as not to interfere with said stripping, testing and trimming steps. 6. The method of claim 5 further comprising the steps of: passing the harness downwardly through a selectively closable gap; and closing said gap immediately prior to said cutting step so as to block passage of said second connector therethrough, whereby said product is allowed to fall upon completion of said cutting step, thereby trapping said product in said gap. 7. The method of claim 6 wherein the step of closing said gap comprises the step of drawing opposed track portions toward each other to form a track extension matable with said delivery track, thereby providing a continuous path for said intermediate harness product. 8. The method of claim 7 further comprising the step of pushing said second connector from said track extension to said delivery track so as to engage said second connector with said drive belt. 9. A double-ended electrical harness fabrication machine that terminates a plurality of insulated electrical conductors to first and second electrical connectors, characterised by a termination station, means for terminating a first portion of the conductors to the first electrical connector at the termination station, means for advancing the terminated first connector past the termination station to present a second portion of the conductors to the termination station, means for terminating the second portion of the conductors to the second connector at the termination station, means for cutting the conductors a predetermined distance beyond the second connector to form an intermediate harness product having a test tab consisting of a portion of the insulated electrical conductors projecting beyond the second connector; a conductor stripping station for at least partially stripping the insulated conductors of the test tab; a testing station including a test probe for testing the harness product by wiping the stripped electrical conductors thereof as said product is advanced therepast, and generating an output signal in said test probe indicative of desired and undesired conditions of the test results; a selectively actuable trimming station for trimming the conductors adjacent the second connector to form a double-ended electrical harness, in response to said output signal from said testing station; a delivery track extending to said stripping, testing, and trimming stations; and means for advancing said product from said termination station along said delivery track to said stripping, testing and trimming stations. 10. The machine of claim 9 wherein said test probe establishes electrical contact with pairs of adjacent harness conductors and measures the electrical resistance therebetween, generating a first output signal indicating the undesired test condition of electrical shorting between adjacent conductors, and a second output signal indicating a desired test condition of the absence of such shorting the machine further including means responsive to an undesired output signal at said testing station for preventing actuation of said trimming station. 11. The machine of claim 9 or 10 wherein said delivery track includes a central slot for receiving and guiding a portion of said product, and at least one driven endless belt disposed adjacent said slot for drivingly engaging an outside surface of said product between said stripping, testing and trimming stations. 12. The machine of claim 11 wherein said terminated connectors are advanced downwardly past the termination station at least partially under the force of gravity, and said product is advanced along the delivery track in a direction generally transverse to the product length, so that substantial portions of said product are maintained beneath said delivery track so as not to interfere with said stripping, testing and trimming steps, said machine further comprising: selectively closeable gap means positioned below said termination station and closeable in response to cutting of said conductors so as to block the passage of said second connector therethrough, thereby allowing said product to fall upon cutting of said conductors, and to thereby be trapped in said gap. 13. The machine of claim 12 wherein said selectively closeable gap means comprises opposed track sections movable toward each other to form a track extension mateable with said delivery track to thereby form a continuous path for said product. 14. The machine of claim 13 further comprising means for pushing said second connector from said track extension to said delivery track so as to engage said second connector with said drive belt.

Inventors: KOLANOWSKI, CLARENCE, PATTERSON, RICHARD L.
Applicants: MOLEX INCORPORATED
Application year: 1986
Main classification: H01R43
IPC codes: H01B13, H01R43