US3885161A

US3885161A - Strand detection arrangement

Info

Publication number: US3885161A
Application number: US298189A
Authority: US
Inventors: John W Tarbox; Walter E Hinds; Rodolfo Castro; Raymond C Bell
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1970-12-31
Filing date: 1972-10-17
Publication date: 1975-05-20
Anticipated expiration: 1992-05-20

Abstract

A wire-dispensing system provides for ordered dispensing and forming of wires along predetermined paths to produce cables and including automating the production of cable harnesses. A wiredispensing head is controlled to selectively dispense wires from a group of supply spools, laying the wire along predetermined paths according to the desired harness pattern configuration, cutting the wires to conform to the individual path lengths, and securing the wires at respective termination sites. The wiredispensing head includes feed tubes selectively actuated to secure the wires at the termination sites wherein movements of the dispensing head are controlled to accurately move the selected feed tubes along the paths determined by the harness pattern configuration. The desired length of an individual precoded wire is determined by optically sensing the configuration of a wire mark which controls wire payout by a rotatable capstan, while feed rate of the tension of the wires is regulated by the same capstan at a low level capable of accurately locating the wires along the wire layout paths of the cable harness wherein the tension is requested so as not to exceed the level of wire retention at the termination sites. The termination sites include openings having resilient retaining means comprising a slit pattern in neopreme at each opening for receiving the end portion of a feed tube and retaining wires on withdrawal of the feed tube.

Description

United States Patent [1 1 Tarbox et a1.

1 1 STRAND DETECTION ARRANGEMENT [75] Inventors: John W. Tarbox, Oceanside; Walter E. Hinds, Beverly Hills; Rodolfo Castro, La Palma; Raymond C. Bell, Fallbrook, all of Calif.

[73] Assignee: Hughes Aircraft Company, Culver City, Calif.

[22] Filed: Oct. 17, 1972 [21 Appl. No.: 298,189

Related US. Application Data [62] Division of Ser. No. 103,233, Dec. 31, 1970, Pat. No.

[52] US. Cl. .1 250/571; 250/559; 250/560; 356/159 [51] Int. Cl. G011) 7/12 [58] Field of Search 356/199, 200,238, 159, 356/199; 250/219 S, 559, 571, 560

[ 56] References Cited UNITED STATES PATENTS 3,051,841 8/1962 Crosfield et al, 356/199 3,088,035 4/1963 Neil 250/219 5 X 3,421,819 1/1969 Anderson et a1. I 250/560 X 3,626,196 12/1971 Arnaudin, .lr 1 A 250/219 S 3,659,950 5/1972 Troll et a1. 356/199 3,699,630 10/1972 Tarboy et a1. 29/203 MW 3,702,404 11/1972 McDermitt 250/559 FOREIGN PATENTS OR APPLICATIONS 1,137,878 10/1962 Germany 356/159 [451 May 20,1975

Primary ExaminerWalter Stolwein Attorney, Agent, or FirmRichard J. Rengel; W. H. MacAllister [57] ABSTRACT A wire-dispensing system provides for ordered dispensing and forming of wires along predetermined paths to produce cables and including automating the production of cable harnesses. A wire-dispensing head is controlled to selectively dispense wires from a group of supply spools, laying the wire along predetermined paths according to the desired harness pattern configuration, cutting the wires to conform to the individual path lengths, and securing the wires at respective termination sites. The wire-dispensing head includes feed tubes selectively actuated to secure the wires at the termination sites wherein movements of the dispensing head are controlled to accurately move the selected feed tubes along the paths determined by the harness pattern configuration. The desired length of an indi vidual precoded wire is determined by optically sensing the configuration of a wire mark which controls wire payout by a rotatable capstan, while feed rate of the tension of the wires is regulated by the same capstan at a low level capable of accurately locating the wires along the wire layout paths of the cable harness wherein the tension is requested so as not to exceed the level of wire retention at the termination sites. The termination sites include openings having resilient retaining means comprising a slit pattern in neopreme at each opening for receiving the end portion of a feed tube and retaining wires on withdrawal of the feed tube.

11 Claims, 8 Drawing Figures PATENIED MAY 20 SHEET 10F 4 PATENTED HAY 2 0 I975 STRAND DETECTION ARRANGEMENT CROSS REFERENCE This application is a division of Ser. No. 103,223 filed Dec. 3l, l970, now US. Pat. No. 3,699,630, granted Oct. 24, l972.

BACKGROUND OF THE INVENTION Automatic assembly of electronic equipment has progressed substantially with technology advancements in microelectronics including integrated circuit systems. Several types of automatic wiring machines have been developed and are in extensive use to provide cir cuit interconnections between circuits, e.g., printed circuit boards mounted on circuit panel boards. These interconnections are made between rows of terminal pins projecting from one side of the panel board to provide power and signal distribution to circuits mounted on the other side of the panel board. Because of the greater efficiency and accuracy of these machines over other methods of making extensive wire interconnections required for complex electronic equipment, these wiring machines provide a substantial advantage in production of electronic equipment.

Despite the successful operation and use of these automatic wire machines in wiring of circuit panel boards, many other types of circuit interconnections are being made manually. One of these latter types of interconnection commonly in use in electrical or electronic equipment is the cable harness which provides power and signal distribution internally between circuit board panels of subassemblies and between individual units including distant units of electronic or electrical equipment.

Automatic assembly of these latter types of interconnections has not progressed due to the many difficult problems encountered in providing a system arrange ment or machine which is versatile, i.e., a machine eapable of accommodating diverse requirements of the electrical and electronic industry without the complexity of foregoing wire wrapping machines. In this field, there is little standardization in wire use including color coding, multiple wire colors and gauges which has re sulted in difficult problems of wire manipulation, and particularly in those instances where long cables are required for interconnection of distant terminals. Further. a machine for automatic assembly of cable harnesses, for example, must also provide a high degree of realibility in providing the proper interconnections to multiple terminal sites.

Accordingly, the present invention is directed to a system providing ordered dispensing of wire along predetermined paths to produce cables interconnecting a plurality of terminal sites according to a stored program including data for locating the wire between terminal sites.

SUMMARY OF THE INVENTION The system arrangement provides. in response to a digital stored program including data for termination points and the paths therebetween. for selectively dis pensing of individual wires by wire-dispensing heads movably disposed on the carriage of a controlled positioning device disposed above respective cable harness forms, each harness form including a plurality of termination sites having openings for retaining terminal portions of individual wires laid along predetermined paths between designated sites to form the cable harness. The common paths for individual wires form the branches and main trunks, and the branches lead to termination sites where the individual wires are separated and retained. Selection of individual wires is provided by system control of wire payout and feed tubes threaded from a precoded wire supply wherein the length ofindividual ones of the wires is designated by marks which are detected prior to securing the lead-ends of the wires at the beginning of respective wire paths to form a cable harness having each wire coded and located according to the code identification. ln dispensing an individual wire of a harness in a wire-dispensing cycle of the system, the wire is removably secured in a selected one of a plurality of wire retention positions of a termi nation site and the tension on the wire during movement along a predetermined path to another termination site is regulated by a capstan drive in order to ac curately place the length of wire along the path while not exceeding the retention capability at the initial termination site.

ln a cycle of operation, one of a plurality of wires supplied to each dispensing head is paid-out by the cap stan into a corresponding feed tube aligned with the wire feed position on the capstan. The feed tube is lowered to secure the lead-end of the wire at the termina' tion site, then raised to the proper wire laying level whereupon the dispensing head is moved along the layout path to the desired termination site for securing the other end of the wire. The tension of wire is regulated during layout by the capstan operating in a feed mode and the wire is cut upon approaching the termination site whereby the end of the wire is drawn from the feed tube to be secured at the latter site.

The cable harness pattern of the preferred embodiment comprises a form board disposed on a work table of the machine and this board includes wire retainers and termination sites located at the end of branches of the cable harness, each site comprises a plurality of openings for receiving the end of a feed tube and a resilient layer having slit pattern coaxially disposed in the respective openings. The slit pattern provides for passing the end of a feed tube while retaining the wire projecting therefrom upon feed tube withdrawal. After the wires of cable harness have been dispensed, the cable harness can be removed from the board for assembly of other cable harnesses. Preferably, any additional processing of the cable harness desired is performed prior to removal from the board. For example. when the wire retainers are fixed to the board and are not removed with the cable harness formed, the wires are tied or otherwise secured to maintain the desired configuration required for use, including branch separation and orientation in two or more axes on individual configurations desired.

lndividual wires are precoded to identify each wire and the length thereof. Accordingly, mark sensors provide for detection of the beginning of each wire length by the physical configuration of a wire-mark. The absence of a wire-mark, or the exhausting of a supply of wire selected to be dispensed, is also detected to interrupt wire-dispensing operations for the selected wire.

While the system of the present invention, as described herein, is directed to wire-dispensing, strand material including fibers, fiber optical strands and tubing, other corresponding elongated materials which are capable of being dispensed between points by the systern are intended to be included in the present invention. Further, the term cable harness," as used herein, refers to strand material dispensed to form intercon nections between termination sites in which common paths between these sites form branches of the cable harness.

Accordingly, it is an object of the present invention to provide a system for ordered dispensing of wire or other strand material and the like, having the foregoing features and advantages.

Another object of the invention is the provision of an improved system for automatic dispensing of strand material and the like to form a desired cable harness configuration of individual strands.

A further object of the present invention is to provide a system arrangement for dispensing strand material about strand retainers, according to a stored program which controls the dispensing operations to dispense the strand material about the retainers, in order to locate the strand material in the desired cable harness configuration.

Another object is to provide a cable harness or the like by dispensing a length of strand material in a pat tern which is determined, in combination, by the path of strand dispensing and retainers on a forming board providing for layout and removal of the strand material.

A further object of the invention is to provide a feed arrangement for regulating the tension of strand material being dispensed.

Still another object is to provide a system arrangement for facilitating the securing of strands at termination sites during automatic strand dispensing.

Another object is the provision of strand-dispensing arrangement providing for selection, payout and regulated feed of any strand of a group being selectively dispensed.

Other objects and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following detailed description of the preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view showing the wire dispensing system arrangement of the preferred embodiment of the invention for ordered dispensing of wires to form wire harnesses;

FIG. 2 is a front view of one of the wire dispensing heads shown in the system of FIG. I, having covers removed to show the structural arrangement thereof and partly broken away to show a typical feed tube assemy;

FIG. 3 is a sectional view of the dispensing head shown in FIG. 2 taken along a sectional line 3-3 and showing a selected one of the feed tubes lowered into position for securing a wire at a termination site;

FIG. 4 is an enlarged detailed view of a section of a termination block of the site shown in FIG. 3 for showing certain details in the securing of a wire at the termination site;

FIG. 4a is a detailed view of the preferred radial pattern for securing the end of the wire in the termination block shown in FIGS. 3 and 4;

FIG. 5 is a top view of the termination block;

FIG. 6 is a schematic diagram for the wire-mark sensors of the wire guide-sensor assembly including a sectional view ofa typical sensor and the logical circuit diagram therefor;

FIG. 7 is a top view of the wire guide-sensor assembly including six {6) wire-mark sensors for individual wires for each wire dispensing head.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, FIG. I shows the system of the preferred embodiment of the invention comprising a dual arrangement of wire dispensing heads I0 mounted on opposite ends of a head positioning carriage 13 including a boom I4 which is made operative to move the heads 10 to automatically dispense individual wires I6 along separate paths of a wire harness pattern defined by wire retainers I7 and wire termination sites 15 on wire harness form boards 18.

Positioning and movement of the wire dispensing heads 10 relative to the form boards 18 are provided by a numerically programmed control system to produce incremental positioning of the heads 10 in accordance with a discrete signal program, for example, or other numerical or computer controlled systems providing for controlled movements from point to point or along continuous paths. In this connection, illustrative reference is made for the first-mentioned system described in US. Pat. Nos. 3,252,l47 and 3,262,105. A positioning control system found in machine tool control is described wherein movable platens or tables, spindles, and workpiece are positioned in one or several axes in accordance with programs defined by a numerical code in individually programmed blocks of a product tape or by other suitable information input.

As shown in FIG. 1 by arrows X and Y, operational movements of heads 10 parallel to the form boards 18 provides concurrent and selective dispensing of wires 16 by heads 10 along individually programmed wire paths between termination sites 15 which pass about projecting arms of retainers 17 to produce a wire harness 20, for example. The wire harness form boards 18 are mounted on work tables 19 by suitably positioned fixtures or clamps which provide for positioning individual boards uniformly on tables 19 for ordered wire dispensing operations. In addition to providing for control of movement of the heads I0 over the form boards 18, the preferred numerically controlled system controls certain auxiliary and preparatory functions for internal operations of heads 10 including wire selection, pay-out and feed intervals of selected wires, wire cutting, and operating levels of feed tubes 22 in a manner described more fully hereinafterv Considering now the details of construction of the wire-dispensing heads 10, a wire supply is shown in FIG. 1 to comprise groups of precoded spools I1 disposed above platforms 10a for respective ones of wiredispensing heads 10. Wires 16 are selectively supplied from spools 11 to corresponding capstans 2S and then to feed tubes 22, for example, feed tube 22a. As pro vided for each of the dispensing heads 10, wires 16 from the respective group of spools II are guided to the feed tubes 22 by peripheral channels in guide rollers 26 and in the capstans 25. The capstan drive assemblies of the respective heads 10 provide individual operating modes, including a positive payout mode in which the capstans selectively pay out one or more of the wires 16 into corresponding feed tube 22a, and a regulated feed mode in which the capstan assembly regulates the tension of the selected wires 16 being dispensed along individual wire paths of harnesses 20.

DETAILED DESCRIPTION OF A TYPICAL WIRE DISPENSING HEAD Referring now to FIGS. 2 and 3 for a more detailed description of the structure of a typical one of the wire dispensing heads 10, FIG. 2 is a front view which shows the internal construction with the feed tubes 22 in their retracted position prior to wire dispensing operations, and FIG. 3 shows the wire dispensing head in payout operating mode securing a selected wire [60 at a selected location at a wire group termination site at the beginning of a layout run". A frarne 30 supports cooperating members of the wire dispensing head 10 to guide the wires 16 laterally from the supply spools 11 to respective channels 27 of the guide roller 26, and vertically to respective channels 29 of the capstan 25 to be fed through respective wire mark sensors 60 and guide tubes 39 of a cutter bar assembly 32. The ends of the wires 16 in guide tubes 39 are thus disposed to be fed into feed tubes 22 which are coaxially disposed along the axes of respective guide tubes 39. In the preferred embodiment therefore, provision is made in each head 10 for guiding seix wires 16 from the supply spools 11 to the capstan 25, maintaining uniform separation ofthe wires 16 by guiding the wires 16 in annular channels 27 of the guide roller 26. The spools 11 on respective spindles are constructed to provide drag during pay-out and wire feed intervals. Each of the wires 16 is wrapped one or more times around the capstan 25 in respective channels 29 to provide pay-out of the wires 16 and regulate the feed rate thereof. For example, any selected wire 16a is paid-out by actuation of a corresponding pinch roller 34 and frictional engagement of the wire 16a with the rotating capstan 25 as shown more clearly in FIG. 3. Subsequently, the driving force transmitted to the wire 16a, during regulated feed while laying of the wire along paths of the wire harness 20 is determined by the degree of frictional engagement of the wire 16a and the annular surface formed by the bottom of the channel 29 for translation of the rotary motion of a capstan to linear movement of the wire 160 through the feed tube 22a to regulate the tension during layout of the selected wire 160. In actual operation of the preferred embodiment, by way of example, the feed tension of wire 16a is regulated to a constant low level of the two (2) pounds for l4l6 gauge insulated wire. By regulation of feed tension, i.e., frictional engagement without pressure of an engaged pinch roller 34, wires 16 in the harness 20 will be maintained taut during wire feed from feed tubes 22 to as sure that the wires will precisely follow along the layout paths to produce the programmed wire harness. Concurrently, the tension of the wires during feeding is regulated by the capstan drive to prevent excessive tension and possible damage thereto as they are passed out of tapered openings at the lower ends of the feed tubes 22 to be disposed about retainers 17 on the form board 18. Further, the regulation of wire tension to a low level assures retention by gripholes 40 in individual positions at the wire termination sites 15 of the wire harness form board 18 (FIG. 3).

In FIG. 2, the capstan drive assembly 24 is shown to comprise a continuously rotating capstan 25 driven by a motor 31 via a belt drive including a belt 31a and pulleys 31b which Couple the drive shaft of the motor 31 to the drive shaft of the capstan 25. The motor 31 drives the capstan 25 continuously at a speed corresponding to the desired rate of pay-out of the selected wire 160. As shown more clearly in FIG. 3, the selected wire 16a is driven down by the capstan 25 into feed tube 220, e.g., during a payout interval. In the preferred embodiment of the control arrangement, which is described in detail in the description in FIG. 3, the selected wire 16a is paid out in sections before and after lowering of the selected feed tube 220. In general, the length of wire paid out must project out of the feed tube 22a for securing an end portion thereof in the slit pattern of the selected griphole 40 at the wire termination site 15, as shown in FIG. 3.

At the beginning of pay-out interval, the end of selected wire 16a is moved from its position at shearing edge 33 of the cutter bar assembly 32 through the lower section of guide tube 34 and into the selected guide tube 22a. After the feed tube 22a is lowered to plunge into griphole 40, an additional length of wire 16a is paid out to provide an exposed end position which is retained by the layer 53 as the tube 22a is withdrawn from the griphole 40 as will be explained in detail later.

The pay-out interval occurs at the beginning of each wire dispensing cycle in the process of forming a wire harness 20, and is followed by a wire feed interval in which the capstan 2S maintains a constant feed tension on the selected wire 16a during traversal of the harness layout pattern. During the pay-out interval, a positive drive is applied to the wire 16a as a result of engagement and pressure applied by pinch roller 34 as shown in FIG. 3. An individually actuated pinch roller 34 is provided for each of the six (6) wires 16, and only the pinch roller 34 corresponding to the selected wire 16a, for example, is energized to engage wire 16a by entering the corresponding groove in the capstan 25. As the pinch roller 34 engages wire 16a, it forces the selected wire into frictional engagement with the bottom of the groove of the constantly rotating capstan 25 to payout wire 16a.

In the pay-out interval, the selected wire 160 must be paid out past the cutter assembly 32 and into the corresponding feed tube 220 to provide a length of wire projecting from the end of the selected feed tube 22a which is retained by the griphole 40. Accordingly, at the beginning of each dispensing cycle, the pinch roller 34 shown in FIG. 3, which corresponds to the selected wire 16a, is moved laterally by actuation of the corresponding linkage 34a coupled to a pneumatic actuator 35a. As shown in FIG. 2, six (6) pneumatic actuators 35 are individually connected to a regulated air supply and electromagnetically actuated to selectively control the supply of air to individual ones of the actuators 35 for corresponding pinch rollers 34.

The cutter bar assembly 32, shown in FIGS. 2 and 3, is disposed below the capstan assembly 24 and consists of a stationary lower section secured to a laterally projection 41 of the frame 30; and a slidable upper section disposed on the lower section to form a wire cutting edge 33. A cutter actuating solenoid 42 is mounted on the opposing wall of frame 30. The armature of solenoid 42 is connected to the movable upper section of the wire cutter assembly 32 by an arm 47a. The solenoid is energized to produce relative movement of the upper section to cut the wire 16a, for example, at a predetermined point approximately 10 inches from the end of the layout run which is at a predetermined one of termination sites 15 for the selected wire 16a.

Each of the feed tubes 22 is slidably disposed for vertical movement to different plunging and operating levels for inserting a respective one of the wires 16 in gripholes 40 and for operational layout movements over the wire harness form board 18 at different operating levels, eg, wire laying levels No. I, No. 2 and No. 3, as shown in FIG. 3. Selective vertical movement and positioning of feed tubes 22 at these levels is provided by an actuator bar 36. Tube guides 30a formed in the lower section 43 of the frame 30 guide the lower sections of feed tubes 22 which are biased upwardly by helical springs 38 having lower sections seating on the lower section 43 of frame 30. Springs 38 bias respective feed tubes 22 into respective seats 46 formed in an opposing lower surface of upper frame section 4]. Annular end sections 37 of feed tubes 22 are secured to the upper ends of the tubing and sections 37 are formed to pass through respective tapered openings 45 in the ac tuator bar 36 to pass all but selected feed tubes 22. As shown in FIG. 3, the selected feed tube 22a is positioned in griphole 40 of one of the termination sites 15 by energization of the corresponding one of the solenoids 46 which positions the end of plunger 47 in an annular channel 48a in the end section 37 of feed tubes 22a. Asa result, when the actuator bar 36 is lowered,

only one selected feed tube 221:, for example, is low ered to plunge the end thereof into griphole 40.

Thus. a selected one of the feed tubes 22a is lowered along with the actuator bar 36 in the bars movement from the upper position, indicated by dashed line 36', to the lower position as shown in FIG. 3. In a wire lay out cycle. the feed tube selection is made prior to lowering actuator bar 16. Accordingly, only the selected feed tube 22a is lowered and the remaining feed tubes 22 remain seated in their respective seats 46 by the bias of the helical springs 38.

As noted, the selected feed tube 22a is positioned by actuator bar 36 to locate the mouth thereof at any one of several operating levels during X-Y movements, indicated as wire laying levels No. I, No. 2, No. 3 in FIG. 3 and also a lower-most position in which the mouth of the feed tube 220 is located in griphole 40 for securing the selected wire 160 at the desired termination site 15. Positioning of the actuator bar 36 to a desired level is controlled by pneumatically actuated positioners or other suitable positioning devices (not shown) coupled to cables 48. In a preferred arrangement the positioners for actuator bar 36 comprise a primary pneumatically operated positioner (not shown) which when actuated applies tension to the lower cable 48 to move the actuator bar 36 down from the top position 36' to plunge the selected feed tube 22a into griphole 40. Additional positioners are subsequently energized to return the primary positioner in increments to position the selected feed tube 22a to the desired operating level and at the end of the cycle to return the feed tube 220 actuator bar 36 to the initial position 36'. As evident from the showing, the position of feed tube and actuator bar 36 corresponds to the location of the primary positioner.

In FIGS. 2 and 3, actuator bar 36 is shown secured to guide tubes 49 for limited vertical travel on guide posts 50. As shown in FIG. 3, the downward travel of the actuator is limited by engagement of guide tubes 49 with shoulders on the guide posts 50. Cam operated switches 51 and 52 (FIG. 21 disposed on either side of the actuator bar 36 are operated by respective cam surfaces to provide an indication of the extreme positions of the actuator bar 36. these positions are the return position as shown in FIG. 2 and the plunged position in which the mouth of the selected feed tube 220 in positioned in the griphole 40 as shown in FIG. 3. Switches 51, 52 provide signals for the logic circuits for determining the location of the feed tubes prior to layout travel, for example. In this instance. switch 52 being operated, the logic signal would inhibit travel in the layout run because the feed tube has not been raised.

TERMINATION SITES Referring to FIGS. 4 and 40 for a more detailed description of the termination sites 15 and gripholes 40, a plurality of gripholes 40 are located at each of the wire termination sites l5 of the wire harness form board 18. As described in connection with FIG. I, the wire harness form board 18 includes a plurality of wire termination blocks 15a located at respective termination sites 15, a typical one of these blocks is shown in FIG. 5.

A wire termination block 15a comprises a metal plate 52 which is secured to a baseboard 54 to firmly and uniformly seat the entire area of a layer 53 of resilient material, such as neoprene, against the opposing area of baseboard 54. A uniform array of openings is provided in the plate 52 for gripholes 40 including a slit pattern formed in the resilient layer 53 and located co axially over openings in the baseboard 54 as shown in FIGS. 4 and 4a. In the preferred embodiment as shown, the wire termination block is spaced from the work table 19, as indicated in FIG. 3, to accommodate the length of wire 16a which is paid out through the mouth of the feed tube 22a after insertion thereof into the griphole 40.

An important feature of the present invention is the provision of the wire termination sites 15 having gripholes 40, each of which is capable of receiving the end of a feed tube and retaining the end of the wire 16a upon withdrawal of the feed tube and against the force of tension applied to the wire during the layout between sites lS. In the feed time period regulation of feed to maintain constant low wire tension is provided by frictional engagement of the wire 16a and the cap stan 25 due to the tension exerted on the wire 16a during head movement in the layout of wire 16a in the harness pattern. Various parameters such as size and diameter of the wires 16, type of insulating material on the wire and composition of the material of the resilient layer 52 determine the level of holding force of the griphole 40. In general, the diameter of the wires, including the insulation, varies from O.l to 0.3 inches and the coefficient of friction between a neoprene layer 53 and the insulating plastic of a wires 16 should be adequate to retain the wires in the gripholes 40 when the feed tension is regulated to approximately two pounds or in the range of approximately one to three pounds, for example. The preferred slit pattern in the layer 53 is shown in FIG. 4a and provides for deflection of the radial sections thereof during plunging of the end of feed tubes 22 therein, and return of these sections during withdrawal of the end of feed tubes 22 to engage the plastic insulation of the wires 16. The radial sections of layer 53 retain the end of the wires against the force of the tension applied to the wires 16 during feed and layout thereof in the harness pattern.

In the preferred embodiment, gripholes 40 were provided for insertion of a 0. I25 inch diameter insulated wire (lo-gauge) for example, by a feed tube 220. Feed tubes 22 have an outside diameter of 0.250 inch and an internal diameter of().187 inch wherein the mouths of the feed tubes are tapered internally and externally to accomodate frictional engagement with the wires and layer 53. In order to accommodate the plunging of the end of the feed tube into the gripholes, and provide for retaining the wires 16 upon withdrawal of the feed tubes 22, the griphole openings are made substantially larger than the feed tubes 22a relying upon the thickness and the shoe of the neoprene layer 53 to retain the wires 16 in the gripholes 40 by the radial sections of the slit patterns in the respective gripholes.

Accordingly, for feed tubes having a 0.250 inch outside diameter, v2 inch diameter openings are provided in an aluminum plate 52 and baseboard 54, and the slit pattern is located coaxially with respective concentric openings in the plate 52 and baseboard 54. The diameter of the cut in the slit pattern can vary from the size of the openings to a lesser diameter of approximately 75 percent of the opening, and in a particular structural embodiment, the cuts of the slit patterns extended substantially across the openings of the respective gripholes 40. The thickness and the hardness of the neoprene layer 53, as well as the extent of the slit diameter, determine in part the gripping force produced on the wires 16. The limitation on the retaining force provided by the gripholes to the wires 16 is primarily due to the need for insertion of the feed tubes 22 into the gripholes without damaging or bending the feed tubes, and preferably to facilitate ease of insertion and removal thereof while providing sufficient frictional force on the wires 16.

The preferred slit pattern of gripholes 40 is shown in FIG. 4a which consists of six (6) radial sections formed by three cross cuts passing through the center of the gripholes 40. Other suitable gripholes 40 have been formed by an H grid pattern, for example, in the neoprene layer 53 in which the cross bar of the H projects across the center of the griphole opening. The H pattern can be modified to provide a grid pattern I-I-I-I having additional cuts normal to the cross bar to facilitate passage of the end of feed tube 220 allowing for deflection of the individual sections of the grid'pattern according to the location and diameter of the feed tube projecting into particular sections.

In general, the thickness of the neoprene layer 53 varied from A3 to A inch in thickness having a shore hardness of 40. A resilient layer 53 formed of neoprene of Va inch thickness and having a shore hardness of 40 was preferred to provide for ease in insertion and withdrawal of the feed tubes 22 while providing more than adequate retaining force on wires 16. In the testing of the griphole construction, it was found that with larger diameters of wire 16, having the same insulation material, the larger the holding force for the same griphole construction. Also, it was found that with increasing thickness of a resilient layer 53 of neoprene, and the higher hardness or shore, the greater is the holding force, while the shape of the slit or grid pattern did not produce any significant change on the wire holding force value which varied from two to four pounds for smaller range of wire sizes, i.e., 0.125 inch or less in diameter.

Further it was found that a force of four pounds is required to plunge the end of feed tube 22a into griphole 40, in a manner as shown in FIG. 3, in which the layer had a A inch thickness and a shore hardness of 40. At a shore hardness of 70, the force increased from four pounds to within the range of six to eight pounds with a radial slit pattern diameter of inch in a /2 inch opening having a pattern as shown in FIG. 4a.

Further, it should be noted that the retaining force of the griphole 40 on the wire 16a does not vary with direction in which the wire is being fed, i.e., a pull exerted coaxially with the griphole or in a direction normal thereto, such as produced in movements of withdrawal of the feed tube 22 from a griphole or during travel parallel to the surface of the board 18. Thus, the retention by the resilient material of layer 53 is directly related to the elasticity of the material and the coefficient of friction between the material of layer 53 and insulating plastic of the wire 16a. Preferably, the gripholes 40 are formed by an opening of minimum diameter suitable to accommodate the outside diameter of feed tubes 22 and tolerances required for positioning of the feed tubes coaxially with the opening. Assuming these latter conditions are satisfied, the maximum feed tension on a selected wire 16a while retaining the wire in the griphole 40 is independent of the amount of wire passed through the griphole, i.e., only sufficient wire must be passed through the pattern in layer 53 to provide engagement of the wire with the engaging edges or surfaces of the material in the layer 53 in the pattern.

In an alternate arrangement of the present invention, the wire dispensing head 10 pays-out a length of wire out of the feed tube before plunging the end of any se lected feed tube 22a into the griphole, and as a result, a loop of wire is retained by the pattern in the griphole 40 with the end of the wire 16a remaining above the form board 18. Thus, if it is desired to provide for ends of wires 16 remaining above the board, pay-out of wire 16 past the end of the feed tube 220 precedes plunging of the end of the feed tube 22a into the griphole 40. It should be noted that a loop of wire 16 is formed at the end of each run of wire 16 of the wire harness formed by either arrangement of the system of the present invention as described and illustrated by the preferred embodiment. Avoidance of loops or wire 16 at the end oflayout runs is readily provided by more precisely cutting the wires 16 or providing for deeper penetration of the gripholes 40 at the end of each run to pull the end of the wires through the gripholes 40, or both. No need presently exists for elimination of wire loops at gripholes 40 and accordingly, the preferred embodiment actually constructed produced wire loops at gripholes located at the end of layout paths of the harness pattern.

WIRE MARK SENSORS Referring to FIGS. 6 and 7 for a detailed description of the wire detecting arrangement of the system of the present invention, each wire dispensing head 10 includes wiremark sensors 60 for each of the six (6) wires 16 as shown by the top view of FIG. 7 and by the front view of the head assembly of FIG. 2. Referring to FIG. 6 for a detailed description of the wire-mark sensors 60, the wire detection arrangement is indicated in the drawing by the plurality of differential amplifiers 62 coupled to a driver amplifier 64 (including a rectifier to provide a unidirectional output) and a typical one of six wire-mark sensing chambers 66. The wire-mark sensors 60 perform two functions in the detection of the difference in output of upper and lower photodetcctors 65 and 67 which are illuminated by a light source 68 located on the opposite side of the sensing chamber 66. Each of the wire'mark sensors 60 detects a wire-mark 63 which consists of adjacent flattened areas of the wire 16a disposed normal to one another which produces a difference in light intensity at the photodetectors 65 and 67 when the mark passes photodetectors 65, 67. Also each of the sensors 60 detects the end of a wire passing these photodetectors 65, 67.

In operation, a difference in output of photodetec tors, 65 and 67 in sensing chamber 66, in response to a wire mark 63 on wire 16a, for example, will be detected by differential amplifier 62 having an output connected to the driver 64. The signal output of amplifier 64, in response to the difference signal at its input is represented in FIG. 6 by a pulse MS which is coupled to the logical circuitry 70 shown in the lower portion of FIG. 6. The mark pulse MS is passed by an OR gate 69c via AND gate 69 which is enabled by a logical input from timing circuit 0530 which input is present during the mark detection period to trigger a timing circuit 0515 at

input os Circuits

058, 0515, 0530 and 0531, i.e., one-shot timing circuits, define the payout interval at the beginning of each wire dispensing cycle wherein circuit 058 is triggered by a signal 357 upon selection of a feed tube 22 and prior to plunging thereof to pay-out an 8-inch length of wire 16a into feed tube 22, for example. The length of wire paid out during the period of circuit 058 is less than the length of feed tube 22 but greater than the maximum downward travel of feed tube 22 to maintain the wire 16a threaded in feed tube 22a, for example.

After the end of the feed tube 22a is inserted into the griphole 40, as shown in FIG. 3, timing circuit 0530 is triggered to define a mark sensing interval in which an additional length of wire 16a is paid-out. The time period of 0530 provides for a maximum pay-out of 30 inches of wire 16a, for example, but circuit 0530 is reset when the wire-mark 63 is sensed and circuit 0515 is triggered to payout a maximum of inches of wire from the time circuit 0515 is triggered. Timing circuit 0515 is triggered by mark pulse MS passed by a gate 69 enabled by the (true) output 05 During the time period of circuit 0515, the wire 16a is paid out to assure that an end portion of sufficient length projects out of the mouth of feed tube 220 for gripping by the layer 53 at griphole 40. To provide for variances in location of wire-mark 63, i.e., located in the length of wire paid out during the time. period of 058, a flip-flop M2 is provided to store the mark pulse MS for later triggering of the circuit 0515, Le, after the 058 time period. Accordingly, a gate 69b, enabled by output 05 provides for passing pulse MS for storage by flipflop M2 which is reset by output 05 The OR gate 69c passes pulse MS or the output of AND gate 690 to trigger the timing circuit 0515. The flip-flop circuits M1 and M2 and timing

circuits

058, 0530 and 0531 are triggered by the leading edge of the signal coupled to the set or reset inputs. Thus, upon detection of the mark pulse M5. an output 0S is produced which extends the pay-out interval for a period sufficient to allow fifteen inches, for example, of wire 16a to be paid out of the feed tube 22a after detection of the wire mark 63.

in order to detect the absence of a mark pulse MS during the maximum pay-out interval and the end of the wire 16a, logic circuit 700 is provided to interrupt the wire dispensing operations, In the event that the predetermined pay-out interval is passed for mark sensing. flip-flop M1 is set to provide a true output M, which interrupts operation of the wire dispensing head and system.

The maximum time period for wire-mark sensing is determined by timing circuit 0530 and at the end of the sensing period, circuit 0530 times out to produce output 05 in the absence of a wire-mark pulse MS, outputs 05, and 05;, gate the output 05 to trigger flip-flop Ml. A timing circuit 0531 provides an overlap in the mark sensing time period for gating output 05 and is triggered along with circuit 0530 by control sig nal g58 at the beginning of the wire sensing period.

In addition, the gates 73, 73a are provided to detect an output from amplifier 64 indicating the end of wire 16a, for example, passing through the sensing chamber 66, i.e., a wire-mark 63 is not expected outside the mark sensing interval defined by output 05 (and 05 As indicated previously, timing circuit 0515 defines the pay-out interval after wire-mark 63 is detected and a pulse output from amplifier 64 during this period of 0515 indicates the end of the wire, or a second wiremark 63 has occurred erroneously. Preferably, the out put 05 in response to a mark pulse MS, is delayed to avoid detection of an extended or double pulse output from amplifiers 63 when a single wire mark passes photodetectors 65 and 67. Outputs of AND gate 73, 73a are passed by OR gate 72 to trigger flip-flop M1 to produce an output M, to terminate the wire dispensing operations. Thus, flip-flop M1 is set by outputs of gates 71, 73, or 73a to terminate wire dispensing operations due to the absence of a wire-mark during the sensing period or due to the end of the wire passing through the sensing chamber 63.

In order to maintain alignment of wire 16a in the sensing chamber 63, a wire guide assembly is shown in FIG. 6 to comprise a flanged guide tube 74 seated in an opening in the top of the enclosure of the sensing chamber 66. The upper, radial surface of the guide tube 74 is beveled at an angle of 20 relative to the radius for coaxial seating of a diaphragm 76 formed of a resilient material, such as neoprene, to provide resilient, frictional engagement with the wire 160, as it passes through the guide tube 74 and into the wire sens ing chamber 66. A ferrule 75, formed of nylon, for example, is retained in the position shown by a cap 77 having an annular channel for receiving the periphery of the ferrule to maintain the rubber disphragm 76 deformed between opposing beveled radial surfaces of the guide tube 74 and ferrule 75. A coaxial passageway is formed in the wire guide by center apertures including a protruding edge of the diaphragm 76 which frictional engages the periphery of wire 16a as the wire passes through the wire guide. The aperture of dia phragm 76 is cut at an angle of 30 relative to the axis thereof before deflection and the aperture formed therein has a minimum diameter of approximately 20 percent less than the outer diameter of the wire passing through the guide tube. This wire guide assembly provides for accurately aligning wire 16a in the interior of the sensor chamber 66 to position the wire 16a precisely along the longitudinal axis of the chamber to be centrally located along this axis which passes between the photodetectors 65, 67 and the light source 69.

The frictional engagement of the diaphragm 76 with the periphery of the wire 16a passing therethrough is slight in the direction of the wire movement into the sensing chamber 66 while inhibiting reverse movement of backlash of the wire 16a to provide uniform movement of the wire coaxially through the sensing chamber 66. As a result, the wire-mark sensor for wire 16a is not subjected to lateral movements or deflections of the wire 160 along the length of the wire in the chamber which would otherwise tend to produce undesired differences in outputs of the photodetector 65 and 67 due to deflections of the wire 16a from the axis of the sensing chamber while passing opposite these detectors.

FIG. 7 is a top view of the six (6) wire-mark sensors 60 for the six (6) wires 16 for the wire dispensing head 10 shown in FIG. 2 and 3, a typical wire guide assembly having been described and shown in FIG. 6. In the preferred embodiment of the invention, the wire guide assemblies for sensors 60 are removable and interchangeable to accommodate different ranges in sizes of wires 16 where the diaphragm 76 is approximately 20 percent smaller in diameter than the midrange diameter wire in a particular range. In the present arrangement, two (2) sets of wire guide assemblies were found adequate for accommodating different wire sizes for all wire harnesses in a particular industrial application wherein the most common wire size is 0.125 inch diameter including insulation for No. 16 gauge wire. The preferred shore of the neoprene diaphragm 76 is sixty (60) although neoprene in the range of 40 to 80 shore was found to provide many of the advantages of the invention for wire guiding in the assembly. The thickness of the diaphragm 76 is approximately 0.125 inch, i.e., including the range of thicknesses from O.l to 0.156 inches, for example. Another less common wire size in a smaller range of sizes in a No. 26 gauge wire having an outside diameter of 0.025 inch including insulation. In this smaller range of sizes, the diameter of wire was more common in the range of 0.025 to 0.30 inch.

The wires 16 can be either a strand or solid conductors of copper, aluminum or other electrically conductive material capable of being formed in the harness pattern. The insulation most common is a uniform thickness of solid plastic although woven glass threads or other insulating threads forming a woven insulation is suitable. A common insulation which provides the advantage of tolerance to heat is tetrafluoroethylene.

OPERATION In operation, wire dispensing by the system arrangement of the present invention to form a cable harness, comprising a group of wires formed to a desired layout pattern, is preceded by loading respective heads from spools 11 of preceded wires 16 and threading the wires from these spools to the cutting edge 33 of the cutter bar assembly 32. Individual wires are passed through channels in the roller guide 26 and the capstan 25 including one or more loops around the capstan by each wire. After the wires 16 have been loaded in the respective heads 10 and the wire harness form boards 18 have been properly positioned on respective tables 19, as shown in FIG. 1, the heads 10 are positioned to locate the respective feed tubes 22a for the selected wires 16a above the first gripholes programmed in the harness layout. Initial positioning of the heads 10 and selected feed tubes 2 is programmed according to the tape or other record provided by the numerical or computer programmed control system. Assuming the tape or other record has been properly loaded into the control for system, the operator need only to press a start button which moves the tape to read the first block of the program. After the heads have been positioned over the first gripholes 40 of the programmed layout the tape is moved to read the next block of the program which includes selection of feed tubes 22a, for example, by actuation of the corresponding solenoids 46 as shown in FIG. 3 for one of the heads 10. Prior to movement of the feed tube 220 downwardly into the griphole 40 for the head 10 shown in FIG. 3, wire 16a is paid-out into feed tube 220 by energization of pneumatic actuator 35 which positions pinch roller 34 to engage and press wire into channel 29 and against the continuously rotating capstan 25. Actuator 35 retracts the pinch roller 34 after wire 16a is paid-out into feed tube 220 a sufficient distance to be retained therein when lowered to plunging position, e.g., eight (8) inches, in accordance with the prior description of control by the logic shown in FIG. 6.

Continuing the description of the operation of only the dispensing head 10 shown in FIGS. 2 and 3, the actuator bar 36 is then moved downwardly carrying the selected feed tube 22a to its lowermost position in which the lower end of this feed tube is positioned in griphole 40, as shown in FIG. 3. Wire 16a is again paid out until a wire-mark 63, shown in FIG. 6, is detected by the corresponding wire-mark sensor 60, or until the end of the wire-mark sensing time period, as discussed more fully in the discussion of the wire-mark sensor 60 in FIG. 6 supra. Assuming the wire-mark 63 is sensed, wire 16a is again paid out for a predetermined time period, corresponding to a length of approximately 15 inches, for example, which assures that the end of the wire 16a extends beyond the end of the feed tube 22a and into the griphole 40. The feed tube 22a is then withdrawn to any selected one of the wire laying levels, No. I, No. 2, No. 3, as shown in FIG. 3 for example, by positioning of the actuator bar 36 by cables 48 connected to a primary positioner (not shown).

After the selected feed tube 22a has been positioned at the proper one of the operating levels No. I, No. 2, or No. 3, depending upon the amount of clearance needed to pass over previously laid wires, if any; the wire dispensing head 10 is moved along the desired path towards a termination site 15 laying the selected wire 16 along the programmed path of the wire harness pattern. For example, as shown in FIG. 1, the movement of the head 10 parallel to the wire harness form board 18 follows a path from a termination site 15 to lay the wire 16a via the retainers 17 and then to the wire terminating griphole 40 at one of the termination sites 15 at the other end of the board. Accordingly, wire dispensing head 10 is controlled to be moved at the selected wire length level from point to point or along a contour in order to follow a predetermined path between termination sites 15 (and gripholes 40) for the selected wire 16a.

Also, during the feed interval, the wire dispensing heads 10 are controlled to maintain a fuel tension at a level which does not exceed the retentive force of gripholes 40. Further, the regulated tension is maintained sufficiently low to insure that no damage occurs as the wires 16a passes out of the rounded or tapered mouths of the feed tubes 22a. Regulation of feed tension at a constant level is maintained by wire-wraps around the rotating capstans 25 of the respective head 10. If the feed tension exceeds the desired level, the wire-wraps around the capstans become taut engaging the knurled surface in the bottoms of channels 29 of capstans 25 to produce positive feed to assist movement of the wires from the capstans into the feed tubes 22a. It is important to note that the capstans operate in the feed mode when the wires are being positively fed during the fed interval as contrasted with the payout interval in which the pinch rollers 34 are moved into actuated position to produce engagement of the selected wires 160 with the respective knurled surfaces of the capstans during the pay-out interval at the beginning of the wire dispensing cycle. Further, the knurled surface is only one form of providing sufficient frictional engagement of the wire 160 with the capstan 25 to provide the positive feed or payout of the wire 16a to provide pay-out or regulation of tension at a constant desired level of tension. Other surfaces providing frictional engagement and capable of withstanding a high degree of abrasion or wear over long periods of time under these conditions are suitable.

At the end of each individual wire dispensing cycle of the wire 16a, for example, feed tube 220 is again in serted into a griphole 40 at the end of the run termination site 15 to secure the end of the wire 16a in the latter griphole 40 for retaining both the end of the wire and the length of the wire and in the wire harness pattern. After insertion of the wire 16a in the latter griphole 40. the feed tube 220 is retracted by actuator bar 36 to the position shown in FIG. 3 by dashed line 36'. Solenoid 46 is then de-energized to complete the wire dispensing cycle. The wire dispensing head is then moved to the next griphole 40 and the next selected feed tube 22 is positioned in the following programmed griphole 40 to dispense the desired wire 16 in the wire harness layout pattern.

In the light of the above teachings of the preferred embodiment disclosed, various modifications and variations of the present invention are contemplated and will be apparent to those skilled in the art without departing from the spirit and scope of the invention. For example, it is anticipated in accordance with the foregoing description that dual dispensing head 10 are operated concurrently and in parallel to produce two cable harnesses in a single cycle. Alternatively, the program for the individual cable harnesses can be employed to set up form boards 18 by substituting a tool on one end of the boom 14 for a dispensing head and forming openings for gripholes 40 and also for placement of retainers 17 on the board 18. Since the locations of the gripholes 40 is recorded on the programmed tape, boards 18 can be readily set up on the same work tables and control equipment. Further, it is contemplated that the cable harness be formed in three dimensions by providing control of movement in 3 axes or 5 axes, although such need rarely exists due to the flexibility of cables for electronic and electrical equip ment. For heavy conductors for high power transmission in interconnections is uncommon and forming in 3 dimensions can usually be accumulated more readily by forming after planar layout. These and other variations of the preferred embodiment of the invention are readily apparent in view of the foregoing disclosure. Further, it is readily apparent that the invention is not limited to dispensing of wire but is equally capable of dispensing strand materials including, but not limited to fibers, fiber optic material, tubing, and other strand materials or variations thereof.

What is claimed is:

l. A strand detection arrangement comprising:

5 means for detecting the profile of individual portions of a length of strand material to produce corresponding output signals, means for moving said strand and means for comparing said output signals for detecting changes in profile of said strand material in which said strand material includes portions deformed in a predetermined manner marking predetermined sections along the length of the strand.

2. The strand detection arrangement according to claim 1 in which said strand material comprises insulated wire having predetermined sections along the length marked by deformed portions.

3. The strand detection arrangement according to claim 2 in which said deformed portions comprise flattened areas formed for marking predetermined sec 20 tions along the length of the strand material.

4. The strand detection arrangement according to claim 3 in which a single deformed portion comprises adjacent flattened segments in which the planes of the flattened segments are displaced about the axis of the strand material.

5. A strand material detection arrangement comprising:

means for passing said strand material, said strand material including portions deformed in a predetermined manner marking predetermined sections along the length of the strand;

a triangular detection area for axially passing a length of strand material for scanning the profile thereof, said area being located between oppositely disposed detection elements including a source of light disposed on one side and a plurality of photodetectors disposed opposite thereto in opposing relation thereto to receive light passing around a portion of the strand material passing through the area, a plurality of said photodetectors being disposed along a line parallel to the axis of the portion of strand material in the area;

said plurality of said photodetectors disposed along a line and being spaced to received light around adjacent segments of said portion of strand material in the area;

differential means coupled to said spaced photodetectors to be responsive to detected different levels of received light by said spaced photodetectors to produce an output signal indicating a change in profile of the portion of strand material located in said area.

6. The strand material detection arrangement of claim 5 in which said strand material comprises insulated wire having at least temporary deformable insulating material which is flattened to provide a change in profile.

7. The strand material detection arrangement of claim 5 in which said means for passing includes alignment means including means for restricting the direction of passing the length of strand material through the area.

8. The strand material detection arrangement of claim 7 in which said means for passing includes control means coupled to said differential means and responsive to said output signal for feeding sections of predetermined length.

disabling said feeding means in response to detection of the end of said strand material.

H. The strand material detection arrangement of claim 5 in which means are provided for indicating a predetermined interval including a change in profile of the strand material and control means responsive to the passing of said predetermined interval without detection of a change in profile to provide an output for interrupting the feeding of said strand material.

Claims

1. A strand detection arrangement comprising: means for detecting the profile of individual portions of a length of strand material to produce corresponding output signals, means for moving said strand and means for comparing said output signals for detecting changes in profile of said strand material in which said strand material includes portions deformed in a predetermined manner marking predetermined sections along the length of the strand.

3. The strand detection arrangement according to claim 2 in which said deformed portions comprise flattened areas formed for marking predetermined sections along the length of the strand material.

5. A strand material detection arrangement comprising: means for passing said strand material, said strand material including portions deformed in a predetermined manner marking predetermined sections along the length of the strand; a triangular detection area for axially passing a length of strand material for scanning the profile thereof, said area being located between oppositely disposed detection elements including a source of light disposed on one side and a plurality of photodetectors disposed opposite thereto in opposing relation thereto to receive light passing around a portion of the strand material passing through the area, a plurality of said photodetectors being disposed along a line parallel to the axis of the portion of strand material in the area; said plurality of said photodetectors disposed along a line and being spaced to received light around adjacent segments of said portion of strand material in the area; differential means coupled to said spaced photodetectors to be responsive to detected different levels of received light by said spaced photodetectors to produce an output signal indicating a change in profile of the portion of strand material located in said area.

9. The strand material detection arrangement of claim 8 in which said control means includes timing means for providing timing signals after said output signal and said control means further includes means for interrupting feeding of the strand material in response to an output signal and a timing signal.

10. The strand material detection arrangement of claim 5 in which the spaced photodetectors detect different levels of light upon scanning the end of a length of strand material and control means are provided for disabling said feeding means in response to detection of the end of said strand material.

11. The strand material detection arrangement of claim 5 in which means are provided for indicating a predetermined interval including a change in profile of the strand material and control means responsive to the passing of said predetermined interval without detection of a change in pRofile to provide an output for interrupting the feeding of said strand material.