US3844462A

US3844462A - Dispensing head for strand material

Info

Publication number: US3844462A
Application number: US00274160A
Authority: US
Inventors: R Castro; J Tarbox; W Hinds
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1970-12-31
Filing date: 1972-07-24
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29

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 individual precoded wire is determined by optically sensing the configuration of a wire mark which controls wire pay-out by a rotatable capstan while the feed rate 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 regulated 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 al.

1 1 Oct. 29, 1974 DISPENSING HEAD FOR STRAND MATERIAL '[75] Inventors: John W. Tarbox, Malibu; Walter E.

Hinds, Los Angeles; Rodolfo Castro, La Palma, all of Calif.

22 Filed: July 24, 1972 21 Appl. No.: 274,160

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

[52] US. Cl 226/25, 226/35, 226/110, 226/176, 226/185 [51] Int. Cl B65h 25/00 [58] Field of Search 226/183, 185, 184, 196, 226/110, 176, 42, 25, 35; 242/45 [56] References Cited UNITED STATES PATENTS 606,424 6/1898 Lamb 226/183 X 2,621,390 12/1952 Nield 226/183 X 2,978,196 4/1961 McCoy et al. 242/45 3,119,536 l/l964 Berkeley..; 226/185 X 3,506,176 4/1970 Brown 226/183 3,694,620 9/1972 Gleason 226/110 Primary Examiner-Allen N. Knowles Attorney, Agent, or Firm-W. H. MacAllister; Richard J. Rengel [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 individual precoded wire is determined by optically sensing the configuration of a wire mark which controls wire pay-out by a rotatable capstan while the feed rate 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 regulated 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.

15 Claims, 8 Drawing Figures 1 DISPENSING HEAD FOR STRAND MATERHAL This is a division of application Ser. No. 103,233, filed Dec. 31, 1970.

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 circuit 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 arrangement or machine which is versatile, i.e., a machine capable 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 resulted 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 reliability 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 ter minal 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 dispensing 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 termi nation 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 pay-out and feed tubes threaded from a precoded wire supply wherein the length of individual 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. In dispensing an in dividual 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 termination 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 accurately place the length of wire along the path while not exceeding the retention capability at the initial termination site.

In a cycle of operation, one of a plurality of wires supplied to each dispensing head is paid-out by the capstan 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 termination site, then raised to the proper wire laying level whereupon the dispensing head is moved along the layour 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 patterns 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 as sembly 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.

Individual 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 system are intended to be included in the present invention. Further, the term cable harness, as used herein,

refers to strand material dispensed to form interconnections 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 produce a cable harness or the like by dispensing a length of strand material in a pattern 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, pay-out and regulated feed of any strand of a group being selectively dispensed.

Othei 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. 1 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. 1, having covers removed to show the structural arrangement thereof and partly broken away to show a typical feed tube assem- 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 tennination 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 of a typical sensor and the logical circuit diagram therefor;

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

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, FIG. 1 shows the system of the preferred embodiment of the invention comprising a dual arrangement of wire dispensing heads 10 mounted on opposite ends of a head positioning carriage 13 including a boom 14 which is made operative to move the heads 10 to automatically dispense individual wires 16 along separate paths of a wire harness pattern defined by wire retainers l7 and wire termination sites 15 on wire harness form boards'l8.

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. 3,252,147 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 punched 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 19a 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 10 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 hereinafter.

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 l1 disposed above platforms 10a for respective ones of wire dispensing heads 10. Wires 16 are selectively supplied from spools 11 to corresponding capstans 25 and then to feed tubes 22, for example, feed tube 22a. As provided for each of the dispensing heads 10, wires 16 from the respective group of spools 11 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 220, 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 16a at a selected location at a wire group termination site at the beginning of a layout run." A frame 30 supports cooperating members of the wire dispensing head It 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 six wires 16 from the supply spools 11 to the capstan 25, maintaining uniform separation of the wires 16 by guiding the wires 16 in annular channels 27 of the guide roller 26. The spools 11 on re spective 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 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 16a through the feed tube 22a to regulate the tension during layout ofthe selected wire 16a. 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 2 pounds for 14-16 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 assure 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 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 24 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 3! drives the capstan 25 continuously at a speed corresponding to the desired rate of payout of the selected wire 16a. As shown more clearly in FIG. 3, the selected wire 16a is driven down by the capstan 25 into feed tube 22a, e.g., during a pay-out interval. In the preferred embodiment of the control arrangement, which is described in detail in the description of FIG. 3, the selected wire 16a is paid out in sections before and after lowering of the selected feed tube 22a. 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 25 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 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 16a 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 16a must be paid out past the cutter assembly 32 and into the corresponding feed tube 22a 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 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 pro jection 41 of the frame 30; and a s'lidable 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, e.g.,

wire laying levels

1, 2 and 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 a 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 41. 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 actuator bar 36 to pass all but selected feed tubes 22. As shown in FIG. 3, the selected feed tube 22a is positioned in griphole 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 tube 220. As a result, when the actuator bar 36 is lowered, only one selected feed tube 22a, for example, is lowered 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 layout cycle, the feed tube selection is made prior to lowering actuator bar 36. 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 I, 2, 3 in FIG. 3 and also a lower-most position in which the mouth of the feed tube 22a is located in griphole 40 for securing the selected wire 16a 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 220 into griphole 40. Additional positioners are subsequently energized to return the primary positioner in increments to position the selected feed tube 220 to the desired operating level and at the end of the cycle to return the feed tube 22a actuator bar 36 to the initial position 36'. As evident from the showing, the position of feed tube 22a 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. 2) 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 22a is 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 4a 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 15 of the wire harness form board 18. As described in connection with FIG. 1, 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 coaxially 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 retainingthe 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 15. 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 capstan 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 0.] 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 I to 3 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 0.125 inch diameter insulated wire (lo-gauge) for example, by a feed tube 22a. Feed tubes 22 have an outside diameter of 0.250 inch and an internal diameter of 0.187 inch wherein the mouths of the feed tubes are tapered internally and externally to accommodate 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 shore 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, 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 radial sections formed by three cross cuts passing through the center of the gripholes 40. Other suitable gripholes 40 have been formed by an 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-H having additional cuts normal to the cross bar to facilitate passage of the end of feed tube 22a 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 one-eighth to one-fourth inch in thickness having a shore hardness of 40. A resilient layer 53 formed of neoprene of one'eighth 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 ll), in a manner as shown in FIG. .3, in which the layer had a one-fourth inch thickness and a shore hardness of 40. At a shore hardness of 70, the force increased from 4 pounds to within the range of 6 to 8 pounds with a radial slit pattern diameter of three-eighths inch in a one-half 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 need be passed through the pattern in layer 53 to provide engagement of the wire 16a 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 selected 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 22a 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 of wire 16 at the end of layout 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 detection arrangement of the system of the present invention, each wire dispensing head I0 includes wiremark sensors 60 for each of the six 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 photodetectors 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 photodetectors 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 690 via AND gate 69 which is enabled by a logical input 08 from timing circuit 0530 which input is present during the mark detection period to trigger a timing circuit 0815 at input os Circuits 088, 0815, 0830 and OS31, i.e., one-shot timing circuits, define the pay-out interval at the beginning of each wire dispensing cycle wherein circuit 058 is triggered by a signal g57 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 088 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 220, 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 0830 is reset when the wire-mark 63 is sensed and circuit 0815 is triggered to payout a maximum of 15 inches of wire from the time circuit 0815 is triggered. Timing circuit 0515 is triggered by mark pulse MS passed by a gate 69 enabled by the (true) output During the time period of circuit OS15, wire 16a is paid out to assure that an end portion of sufficient length projects out of the mouth of feed tube 22a 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 OSlS, i.e., after the 088 time period. Accordingly, a gate 69b, enabled by output 05 provides for passing pulse MS for storage by flip-flop 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, 0515, 0830 and OS31 are triggered by the leading edge of the signal coupled to the set or reset inputs. Thus, upon detection of the mark pulse MS, an output 08 is produced which extends the payout interval for a period sufficient to allow fifteen inches, for example, of wire 16a to be paid out of the feed tube 220 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 a 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 0330 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 08, and 08 gate the output 05 to trigger flip-flop Ml. A timing circuit OS31 provides an overlap in the mark sensing time period for gating output 05 and is triggered along with circuit 0530 by control signal 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 08 As indicated previously, timing circuit OSlS defines the payout interval after wire-mark 63 is detected and a pulse output from amplifier 64 during this period of 0815 indicates the end of the wire, or a second wiremark 63 has occurred erroneously. Preferably, the output 08, 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 sent 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 16a, as it passes through the guide tube 74 and into the wire sensing 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 75 to maintain the rubber diaphragm 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 this wire guide. The aperture of diaphragm 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 68.

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 or 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 ll6a 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 wire-mark sensors 60 for the six wires 16 for the wire dispensing head I shown in FIGS. 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 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 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 0.l0 to 0.156 inches, for example. Another less common wire size in a smaller range of sizes is 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 stranded 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 10 from spools ll of precoded 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. I, the heads 10 are positioned to locate the respective feed tubes 22a for the selected wires 160 above the first gripholes programmed in the harness layout. Initial positioning of the heads 10 and selected feed tubes 22 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 22a downwardly into the griphole 40 for the head 10 shown in FIG. 3, wire 16a is paid-out into feed tube 22a by energization of pneumatic actuator 35 which positions pinch roller 34 to engage and press wire 16a 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 22a a sufficient distance to be retained therein when lowered to plunging position, e.g., 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 pe riod, 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, 1, 2, 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

1, 2 or 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 l7 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 laying 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 feed 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 heads 10. If the feed tension exceeds the desired level, the wire-wraps around the capstans become taut engaging the knurled surface in the bottom 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 feed interval as contrasted with the pay-out 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 16a with the capstan 25 to provide the positive feed or pay-out 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 22a is again inserted 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 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 10 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 heads 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 location 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 equipment. For heavy donductors 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 dispensing head for strand material comprising:

means for supplying strand material; and

means for feeding said strand material including means for drivingly engaging said strand material in response to tension on the strand material applied at the drivingly engaging means from downstream thereof to produce driving engagement of said strand material and the drivingly engaging means to dispense the strand material.

2. A dispensing head according to claim 1 in which said means for drivingly engaging said strand material comprises a capstan and means for driving said capstan and the capstan is responsive to the predetermined level of tension applied thereto.

3. The dispensing head according to claim 2 in which said means for drivingly engaging the strand material further includes means selectively operative for pressing the strand material against the periphery of the capstan to produce frictional engagement of the strand material with the capstan to pay-out the strand material independently of the downstream tension on the strand material.

4. A dispensing head according to claim 2 in which said capstan is constantly driven and driving engagement of the strand material is determined by the amount of tension produced at the capstan and frictional engagement of the strand material with the capstan.

5. A dispensing head for strand material comprising:

means for supplying strand material; and

means for feeding said strand material including means for drivingly engaging said strand material wherein the feeding means includes a plurality of feed tubes disposed for individually receiving the strands of material and means for selectively positioning a feed tube for dispensing strand material.

6. A dispensing head according to claim 5 in which the selective means comprises means for positioning feed tubes to project the open ends thereof for feeding the strand material.

7. A dispensing head according to claim 6 in which the positioning means comprises means common to said plurality of feed tubes including means for selecting individual ones of the feed tubes to be projected for feeding the strand material.

8. A dispensing head according to claim 5 in which the feeding means further includes means for supporting and guiding said strand material from said supply means to said means for drivingly engaging the strand material so that individual strands of material are threaded through selected ones of the plurality of feed tubes.

9. A dispensing head according to claim 8 in which said means for drivingly engaging said strand material comprises a cylindrical capstan and means for rotatably driving said capstan about the cylindrical axis thereof.

10. A dispensing head according to claim 9 in which said capstan is constantly driven and the driving engagement is determined by the amount of frictional engagement with the rotating periphery of the cylindrical capstan.

11. A dispensing head according to claim 8 in which the strand material is disposed about the capstan periphery so that driving engagement and the capstan is a function of tension extended on the strand material.

12. A dispensing head according to claim 10 in which individual strands of material are guided to axially spaced cylindrical sections of the periphery of said capstan and said feed tubes are supported to receive individual strands from the respective sections.

13. A dispensing head for strand material comprising:

the strand material is disposed about a capstan so that driving engagement of strand material and the capstan is a function of the tension exerted on the strand material at the capstan from downstream of the drivingly engaging means.

15. A dispensing head for strand material comprising:

l means for supplying strand material; and means for feeding said strand material including means for drivingly engaging said strand material, said means for feeding said strand material including means located downstream of the drivingly engaging means, for producing tension on the strand material for dispensing the strand material at least partly in response to the amount of tension whereby the tension is regulated during dispensing of the strand material so that the amount of tension does not exceed a predetermined amount, said drivingly engaging means comprises rotatable means and said strand material forms a loop substantially encircling the periphery of said rotatable means and tension downstream thereof causes tightening of the loop of strand material for frictionally engaging said rotatable means during driven rotation thereof.

Claims

1. A dispensing head for strand material comprising: means for supplying strand material; and means for feeding said strand material including means for drivingly engaging said strand material in response to tension on the strand material applied at the drivingly engaging means from downstream thereof to produce driVing engagement of said strand material and the drivingly engaging means to dispense the strand material.

5. A dispensing head for strand material comprising: means for supplying strand material; and means for feeding said strand material including means for drivingly engaging said strand material wherein the feeding means includes a plurality of feed tubes disposed for individually receiving the strands of material and means for selectively positioning a feed tube for dispensing strand material.

13. A dispensing head for strand material comprising: means for supplying strand material; and means for feeding said strand material including means for drivingly engaging said strand material, said means for drivingly engaging said strand material is responsive to a predetermined level of tension on said strand material at the drivingly engaging means and applied from downstream thereof, to dispense the strand material so that the downstream tension is regulated so as not to exceed said predetermined level.

14. A dispensing head according to claim 13 in which the strand material is disposed about a capstan so that driving engagement of strand material and the capstan is a function of the tension exerted on the strand material at the capstan from downstream of the drivingly engaging means.

15. A dispensing head for strand material comprising: means for supplyIng strand material; and means for feeding said strand material including means for drivingly engaging said strand material, said means for feeding said strand material including means located downstream of the drivingly engaging means, for producing tension on the strand material for dispensing the strand material at least partly in response to the amount of tension whereby the tension is regulated during dispensing of the strand material so that the amount of tension does not exceed a predetermined amount, said drivingly engaging means comprises rotatable means and said strand material forms a loop substantially encircling the periphery of said rotatable means and tension downstream thereof causes tightening of the loop of strand material for frictionally engaging said rotatable means during driven rotation thereof.