US3083653A

US3083653A - Work indexing mechanism for sewing machines

Info

Publication number: US3083653A
Application number: US831894A
Authority: US
Inventors: Thomas A Mcgill
Original assignee: Singer Co
Current assignee: Singer Co
Priority date: 1959-08-05
Filing date: 1959-08-05
Publication date: 1963-04-02
Anticipated expiration: 1980-04-02
Also published as: GB898180A

Description

WORK INDEXING MECHANISM FOR SEWING MACHINES Filed Aug. 5, 1959 T. A. M GILL April 2, 1963 6 Sheets-Sheet 1 A ril 2, 1963 T. A. M GILL WORK INDEXING MECHANISM FOR SEWING MACHINES 6 Sheets-Sheet 2 Filed Aug. 5, 1959 April 2, 1963 T. A. M GILL WORK INDEXING MECHANISM FOR SEWING MACHINES Filed Aug. 5. 1959 6 Sheets-Sheet 5 A ril 2, 1963 T. A. mam. 3,083,653

WORK INDEXING MECHANISM FOR SEWING MACHINES Filed Aug. 5, 1959 6 Sheets$heet 4 Fig.7

April 2, 1963 1'. A. M GILL 3,083,653

WORK INDEXING MECHANISM FOR SEWING MACHINES Filed Aug. 5, 1959 6 Sheets-Sheet 5 April 1963 T. A. MOGILL 3,083,653

WORK mozxmc MECHANISM FOR smwmc MACHINES Filed Aug. 5, 1959 6 Sheets-Sheet 6 v JJCZA s I M/ a V EW NG C 23% INDEXING DRIVE JICZD MOTOR 3 5 If Q Q 9 Q 1.40 I50 MAIN ON EMERGENCY 6 STOP 1: CIB CIA CIC DRIVE |60 '1' MOTOR 0N q Q ane" LOADER U wo :r mom 0N AL 4} L m \J me BUTTON @LoAoER me \JTAOTQR CYCLE m0 LASTART I W R30 IP-M V RZA H R48 msz S-l l BUTTON LOADER 28 NOHC J/AMS-I s-z ONE REV. CLUTCH NOHC r f; coumms COUNTING R38 CLUTCH I CLUTCH Al V COIL FOOT/90 I swncu \f o.c. POWER SUPPLY cl i bn ||R4C H l is! M/ m. A 882%? i n I R4A A s-a cum? OPENER m s-4 CLAMP OPENER S-GII/CLOTH DEFLECTOR AIA s-s CONVEYOR STOP Fig.l0

United States Patent F 3,083,653 WQRK IINEEXING MECHANISM FGR SEWENG MACHINES Thomas A. McGill, Lunenburg, Mass, assignor, by mesne assignments, to The Singer Manufacturing Company,

Elizabeth, N.J., a corporation of New Jersey Filed Aug. 5, 1959, Ser. No. 831,894 4 Claims. (Ci. 1122) This invention relates to sewing machines and, more particularly, to a sewing unit for producing automatically a plurality of separate stitching operations on a garment or other fabric article.

It is an object of this invention to provide a fabric manipulating mechanism which may be loaded and unloaded with a minimum of attention by an operator, and which will operate unattended.

It is also an object of this invention to provide a new and improved work indexing mechanism for shifting a work fabric between successive stitching operations.

Another object of this invention is to provide a novel unloading and storing means for finished articles.

With the above and other objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawings of a preferred embodiment in which:

FIG. 1 represents a front elevational View of a button sewing unit having this invention applied thereto,

FIG. 2 represents a top plan view of the sewing unit of FIG. 1,

FIG. 3 represents a side elevational View of the Sewing unit of FIG. 1,

FIG. 4 is a cross-sectional view taken substantially along the line 44 of FIG. 1, illustrating the microswitch control on the cam-shaft as well as the work indexing cam thereon,

FIG. 5 is a cross-sectional view taken substantially along line 5-5 of FIG. 1 illustrating the one revolution clutch and solenoid control for the cam shaft,

FIG. 6 is an enlarged cross-sectional view taken substantially along line 66 of FIG. 2 illustrating the work grippers of the indexing device together with the gripper locating device and the gripper opener,

FIG. 7 is an enlarged cross-sectional view taken substantially along line 7-7 of FIG. 2 illustrating the work pp FIG. 8 represents an enlarged front elevational view of a fragment of the sewing unit of FIG. 1 illustrating the finished article holder and the sewing frame for carrying a finished article over the holder,

FIG. 9 is an enlarged cross-sectional view taken substantially along line 99 of FIG. 8, and

FIG. 10 is a circuit diagram of the sewing unit of this invention.

Referring particularly to FIGS. 1, 2 and 3, this invention is illustrated in preferred form as embodied in a sewing unit for manipulating a fabric panel relatively to a button sewing machine 11 of a conventional type having an endwise reciprocable needle 12 defining a stitching point, a starting lever 13 to initiate operation of the sewing machine, a stop motion mechanism 14 to stop the machine after a predetermined number of stitches have been made, a button holding work clamp 15 of which the motion is controlled by a pattern cam '16, and a work clamp opening lever "17.

The sewing machine preferably operates in cooperation with a button loading device which may be of any form known in the art and preferably is of the type having a control shaft 21 which is driven by a constantly operating button loader motor 22 and turns one revolu- Patented Apr. 2, 1963 tion for each button loading operation but accomplishes that revolution in two separate increments. During the first increment of turning movement, the control shaft 21 effects the movement of a button inserting arm 23 to load a button into the sewing machine work clamp, closes the sewing machine work clamp by way of a lever 24 connected to the sewing machine Work clamp opening lever 17 by a pull rod 25, and actuates the sewing machine starting lever 13 by way of a lever 26 connected to the sewing machine starting lever by a rod 27.

Upon completion of the sewing machine operation, the sewing machine stop motion mechanism, in releasing the starting lever 13, releases the rod 27 and the lever 25, which movement initiates the second increment of turning of the control shaft 21 of the button loader. During the second increment of turning movement, the control shaft 21 shifts the button inserting arm 23 to pick up another button from the hopper feed chute 28, opens the sewing machine work clamp by way of the lever 24 and the pull rod 25, and finally, shortly before completion of the revolution, pulses a microswitch MS- 1 for initiating operation of the work indexing mechanism. The button loading device 29 is preferably called into operation by a solenoid 8-1 which triggers the button loading device by means of a pull rod 29.

The sewing machine ll and the button loading device 24) are supported on a cabinet 30 which together with an auxiliary supporting section 31 also carries the work indexing mechanism and the electric circuitry necessary to effect automatic sequential operation of the sewing and work indexing operation of this sewing unit.

Supported on pairs of sprocket wheels 32 carried on spaced

horizontal shafts

33 and 34 disposed one at each side of the sewing machine are a pair of endless link belts 35 providing an endless conveyor extending transversely across the front of the sewing machine 11 and having vertically spaced substantially parallel horizontal limbs extending between the pairs of sprocket wheels. The link belts 35 are stabilized on guide rails 36 fastened on the cabinet 30 and supporting section 31 and have secured thereon at spaced intervals pairs of work gripping clamps 37. As will be described hereinbelow, the conveyor is adapted to be driven in only one direction and of each pair of work gripping clamps, one will be the leading clamp 37L and the other will be the trailing clamp 37T as illustrated in FIG. 2. Preferably four pairs of clamps are secured to the endless belts 35 and are secured on the belts with equal spaces between pairs of clamps. Therefore, when a leading clamp 37L is positioned adjacent to the stitching point on the upper limb of the link belts in readiness to begin a cycle of operation of the sewing unit, that pair of clamps which is disposed on the under limb of the link belts will be disposed in substantially vertical alignment beneath the clamps on the upper limb.

The endless link belts 35 are driven from a drive shaft 40 journaled in the cabinet 30 by Way of a link belt 41 interconnecting a sprocket wheel 42 on the shaft 33 and a sprocket wheel 43 connected by means of gearing with the drive shaft 40.

An electric motor 44, which is adapted to run continuously, is drivingly connected with the sewing machine by means of a belt 45 and is provided with alternative driving connections with the drive shaft 40. A speed reducer 46 driven by a belt 47 from the motor 44 is operatively connected by

link belts

48 and 49 to drive continuously a clutch sprocket wheel 50 on a cam shaft 51 journaled in the cabinet 30 and a clutch sprocket wheel 52 on the drive shaft 40.

The clutch sprocket wheel 59 on the cam shaft 51 is associated with a one revolution clutch 53 controlled by 3 a solenoid S-Z, actuation of which serves to turn a cam 54- on the cam shaft 51 to oscillate a feed lever 55 having a follower 56 engaging the cam 54. A link 57 con' nects the feed lever with a rock arm 58 of a ratchet device 59. on the 'drive shaft 40 which imparts an increment of turning movement to the drive shaft 46 on the upstroke of the feed lever to index a work fabric between successive button sewing operations. A lug 6i! fast on the cam shaft 51 engages a microswitch WIS-2 upon completion of the cam operated work indexing motionrto trigger the next sewing operation.

The clutch sprocket wheel 52 on the drive shaft 46 is associated with an electric clutch 61 which is actuated, as will be described hereinbelow, to drive the work indexing mechanism to a starting position after completion of the last sewing operation on each work fabric panel. 7 Referring to FIGS.- 6 and 7, each work gripping clamp 37 includes a jaw 70 fixed relatively to said endless link belt-s35 and formed with a lengthwide slot 71 opening onto a hooked portion 72 at the outer extremity, which hooked portion is turned back upon the slotted portion. Pivoted in the slot 71 is a movable jaw member 73 formed with a serrated portion '74- disposed to engage the hooked portion 7 2 of the fixed jaw to clamp work fabric inserted in the hooked portion. A spring 75 biases the serrated portion 74 into work clamping relation with the hooked portion 72 and each movable jaw is formed with an angularly extending limb '76 for shifting the jaws out of work clamping relation. 7

For opening the work gripping clamps a pair of levers 80 are provided, each fulcrumed on a vertical pin 81 in the link belt guide rail member and disposed one on each side of the sewing machine, as illustrated in FIG. 2. The levers 80 are controlled by solenoids S3 and S-4. The levers 80 are arranged, as illustrated in FIG. 6, each to engage the limbs 76 of two work gripping clamps one carried on the upper limb of the endless conveyor 35 and the other carried on the under limb thereof when the clamps occupy the starting position. As mentioned above, in the starting position, alternate pairs of the work gripping clamps are disposed in vertical alignment with each other, andthe starting position is accurately defined by a conveyor stop solenoid S-S carried between the upper and under limbs of the endless link belt and having a stop lug 85 carried on the armature thereof in the path of stop blocks 86 carried by screws 87 on each leading. work gripping clamp 37L. When the leading work gripping clamps 37L traverse the upperlimb of the conveyor belts 35, the stop blocks 86 have'two functions as illustrated in FIG. 6, i.e., one of engaging the stop lug 85 todetermine a starting position, and the second of underlying the guide rails 36 to hold the work clamps and link belts thereon. When solenoid S- is energized, the stop lug S5 is drawn out of the path of the stop block 86 to release the indexing mechanism for each cycle of operation.

When the leading work gripping clamps 37L traverse the under limb of the conveyor belts 35, the stop blocks 86 perform an additional function of actuating a microswitch MS-3, as illustrated in FIG. 2. The microswitch MS-3, as will be described in detail later, senses movement of the work gripping clamps into stopped position in response to which the cycling circuits of the sewing unit are dis abled. Microswitch MS-3 also senses the initial movement of the work gripping clamps out of stopped position and acts to restore the conveyor stop 85 to effective stopping position.

The trailing work gripping clamps 37T are formed with blocks 88 having the sole purpose of retaining the trailing work gripping clamps on the guide rails. The blocks 87 a are formed with a clearance slot 89 to prevent engagement with the stop lug 85.

'The solenoids S-3 and S-4 for opening the work gripping clamps 37 are controlled by an operator influenced foot switch 96. The foot switch 90 also serves to actuate a solenoid 5-6 simultaneously with actuation of the solenoids S-3 and S-4. The solenoid S-6 is operatively connected with a device which will now be described for handling fabric panels which are released from the work gripping clamps by the operation of the solenoids S-3 and s 4 As illustrated in FIGS. 1, 2, 3 and 6, a smooth cover plate 1% overhangs the endless link belts 35 and covers a considerable portion of the fixed jaw '70 of the work gripping clamps 37. When a work fabric panel is inserted in the work gripping clamps on the upper limb of the endless conveyor 35, it is preferably draped over the cover plate 1% and the panel slides along the cover plate until the clamps in which it is gripped traverse the sprocket 32. As the work gripping clamps are advanced along the under limb of the endless conveyors 35, the fabric panel will depend substantially vertically from the inturned hooked extremities 72 of the work gripping clamps.

Referring to FIG. 3, a finished work holder in the form of an upstanding folded sheet metal plate is secured on a bracket 111 carried on the front of the cabinet 30. The work holder 11% is preferably disposed beneath the Work gripping clamps 37 and outside of the vertical planes in which the finished work panels will depend from the inturned hooked extremities 72' of the work gripping clamps.

Pivoted in bearing lugs 112 secured beneath the bracket 111 is a work deflecting frame 113 carrying at its upper extremity a rod 114 disposed to swing across the vertical plane in which the finished work panels will depend from the work gripping clamps and to occupy a position between the work gripping clamps and the top of the work holder 119. The solenoid S-6 is connected to the frame 113 beneath the bearing lugs 112 by a tension spring 115. A stop arm "116 carried by the work deflecting frame 113 is fitted with a pad of cushioning material 117 and disposed to engage behind a portion of the auxiliary support 31 limiting the extreme position of the work engaging rod 114 outwardly beyond the work holder 110, as illustrated in dashed lines in FIG. 9. A cushion 118 carried on the cabinet 30 determines the at-rest position of the work defleeting frame 113, the frame preferably being balanced to return to the at-rest position by gravity.

. 'When the foot switch 90 is depressed, therefore, and the work gripping clamps occupy the starting position, i.e., the position between cycles of operation of the sewing unit as determined by the solenoid S-S, the solenoids S-3, S-4 and S-6 will be energized simultaneously to open the work gripping clamps on the top of the conveyor to receive new work, to open the work gripping clamps beneath the conveyor to release the finished work panel and simultaneously to swing the rod 114 of the work deflecting frame 113 across the work holder 110 to fold the finished work panel across'the work holder.

When the work holding clamps are opened by the depression of the foot switch 90, new work may be located accurately in the clamps. by means of adjustable edge guides 12% carried on the cabinet 30 and the auxiliary support 31. The edge guides 120 are preferably spring loaded upwardly so as to yield to permit the work gripping clamps to pass thereover. An adjustable locating guide 121 secured to the cabinet is useful in establishing proper button orientation with respect to the top or bottom edge of a garment panel.

A box 'carried at the rear of the auxiliary support 31 is provided for the electrical components of the control circuit which need not be readily accessible or physically related with the mechanism of the sewing unit. With reference to the circuit diagram of FIG. 10, the following is a description of the preferred circuitry and the operation of the sewing unit of this invention.

In FIG. 10, the contactors are designated C, plain relays R, a counting coil T, and a time delay relay A. The designation of each of the contacts includes the desig- 5 nation of the relay or other device by which it is controlled, as for instance contacts CIA, ClB and 01C being controlled by contactor C-l.

In the diagram, the source of electrical current is indicated as being three phase, supplying power directly to the drive motor 44 with contacts C213, C2C and C2D, one in each of the three phase lines. A transformer 140 provides low voltage single phase current for the control circuits including a main power control circuit having an emergency stop switch 151 and a main power switch 155 for energizing a contactor C! to close contacts ClA holding in the switch 150, and to close contacts ClB and C10 for supplying current to control buses between which the various control circuits are made.

The start and stop

switches

160 and 161 for the sewing machine and indexing drive motor 44 are in series with a contactor C-Z between the control buses, contacts CZB, CZC, and C2D in the three phase lines supplying the motor 44 being controlled by the contactor -2 as well as the holding contacts C2A in parallel with the start switch 169.

The button loader motor 22 is in series between the control buses with contacts RIB and RlC controlled by a relay R-l in series between the control buses with start and stop

switches

170 and 171. The start switch 170 is in parallel with holding contacts R1A controlled by the relay R-l. The sewing unit is made ready for operation by closing the main power switch 156 and the drive and button loader motor switches 160 and 170.

The foot switch 90 operates to actuate the clamp opening solenoids S3 and 5-4 and the cloth deflector solenoid S6 by energizing a relay R-3 closing contacts R3A in series with these solenoids between the control buses. Actuation of the relay R-3 also serves to open the normally closed contacts R3B in series with a clutch coil T-l of a counting clutch to reset the counting clutch each time the work gripping clamps are opened. The relay R3 also operates to open the normally closed contacts R3C in series with the relay R-Z between the control buses. The relay R-Z as will be described more fully hereinbelow is instrumental in controlling the alternate sewing and indexing operations, and the contacts RSC provide a safety interlock preventing either sewing or indexing operations from occuring while the work gripping clamps are opened.

When a work panel is properly located in the work gripping clamps and the foot switch 9-0 is released to close the clamps, the operator can initiate operation of the sewing unit by closing the cycle start switch 18%. The switch 180, which is in series with a stop switch 181, the contacts RSC, and the relay R-Z, energizes the relay R-Z which closes the holding contacts in parallel with the cycle start switch 180 and closes contacts R2B in series with microswitch MS-2 and the button loader release solenoid S-l. Since the microswitch MS2 is held closed by the lug 6% between sewing cycles, closing of contacts RZB will release the button loader 20 which will operate as described earlier to load a button in the sewing machine clamp, close the sewing machine clamp, and start the sewing machine.

Operation of the sewing machine stop motion mechanism will signal the button loader to continued operation to pick up a new button, open the sewing machine work clamps, and momentarily close the microswitch MS-l shortly before the button loader device comes to rest.

As illustrated in the circuit diagram of FIG. 10, the microswitch MS-l is in series with the one revolution clutch releasing solenoid S-2 and also with the counting coil T of the counting clutch.

Release of the one revolution clutch 53 causing one revolution of the indexing cam 54 will shift the work gripping clamps a distance equal to the space desired between adjacent buttons, at the completion of which the microswitch MS-Z will be closed and held closed by the lug 60 on the cam shaft 51. The microswitch MS-2 signals a succeeding operation of the button loader so thit' by way of microswitches M34 and MS-Z, alternate sewing and indexing operations occur each indexing operation signaling one pulse to the counting coil T of the counting clutch.

Referring to the diagram of FIG. 10, the microswitch MS-3 which is operated by the work gripping clamps 37L when the clamps occupy starting position, comprises in etfect a pair of switches, one normally closed and the other normally open. The normally closed side of the microswitch MS-3 is in series with a relay R-4 and parallel contacts TlA controlled by the counting clutch T-l and R4A controlled by relay R-4 for holding in the contacts TIA. When the counting clutch coil T-l is energized by virtue of the counting coil T being pulsed a predetermined number of times, the contacts T1A will be closed and the relay R'4 energized. The contacts R4B in the holding in circuit in parallel with the cycle start switch will be opened, thus breaking the circuit which energizes relay R-2. The alternate operation of the sewing machine and the indexing device will stop since the contacts RZB will break the circuit to the button loader release solenoid 8-1.

In order to drive the indexing device back to a new starting position, the DC. clutch 61 is energized by closing of the contacts R40 in the series with the clutch in a DC. circuit from a DC. power supply connected between the buses. The clutch 61 will, therefore, drive the conveyor into starting position as determined by the conveyor stop 85.

Upon reaching starting position, microswitch MS3 will be engaged by the block 86, the normally closed part will be held open deenergizing relay R-4, and the normally open part will be closed.

When the relay R-4 is deenergized, the contacts R4B in the cycle start holding circuit again close in readiness for a succeeding operation, the DC. clutch 61 is disengaged by the opening of the contacts R40 and the holding contacts RA are opened.

The normally open portion of microswitch MS-3 is not immediately efiective when held closed by the arrival of the parts into starting position because of the open contacts RZC in series with that portion of MS3 and with the time delay relay A-l. When the cycle start switch 189 is again closed, however, the closing of contacts RZC completes a circuit energizing the relay A-l momentarily until the Work gripping clamps are given their initial movement to release the microswitch MS-ll. The contacts AlA in series with the conveyor stop solenoid S5 will be closed to energize the solenoid 8-5 and withdraw the stop suificiently long as to permit the indexing mechanism to partake of a succeeding cycle of work indexing movements.

Having set forth the nature of this invention, what is claimed herein is:

1. In a sewing unit having a sewing machine, a work indexing means for shifting a fabric relatively to the stitching point of said sewing machine comprising an endless conveyor supported for movement in one direction relatively to the stitching point of said sewing machine, means constraining said endless conveyor in an elongate loop having substantially straight and parallel elongate limbs, a plurality of pairs of work gripping clamps carried by said endless conveyor, the work gripping clamps of each of said pairs being carried in spaced relation along said endless conveyor for engagement with opposite extremities of a work fabric panel, each of said work gripping clamps comprising a pair of jaws, means supporting said jaws for movement relatively to each other into and out of work gripping relation, means defining a starting position of any of said plurality of pairs of Work gripping clamps relatively to said sewing machine stitching point, said plurality of pairs of work gripping clamps being spaced along said conveyor such that in the starting position the leading work gripping clamp of a pair of clamps on one of said conveyor links is disposed directly opposite the trailing work gripping clamp of another pair of clamps on the opposite con- 7 veyor limb; and a pair of work clamp opening solenoids carriedon said sewing unit, said solenoids being disposed for operative engagement in the starting position of said work gripping clamps to open simultaneously both of a directly opposite set'of leading and trailing work gripping clamps.

2. A sewing unit as set forth in claim 1 in which the endless conveyor is elongate horizontally and in which each of said pair of clamp opening solenoids is effective in the starting position of the work gripping clamps to open a work gripping clamp on the upper limb of the conveyor for loading of a work fabric panel, and a work gripping clamp on the under limb of the conveyor for unloading a sewn work fabric panel.

3. In a sewing unit as set forth in claim 2, a means for storing a work fabric panel, after stitching has been completed comprising a fabric panel supporting rail disposed beneath said under limb of the conveyor and at one side of the path of travel of a fabric panel depending from said work gripping clamps in the under limb of said conveyor, a swinging frame pivoted on said sewing unit and including a fabric deflecting bar disposed between said work gripping clamps and said fabric supporting rail, and a solenoid means operative simultaneously with said work clamp opening solenoids for swinging said frame to move said fabric deflecting bar across the path of travel of fabric panel depending from said work gripping clamps and across said fabric supporting rail to direct said released fabric panel to a position draped over said fabric supporting rail.

, 4. In a sewing unit having a sewing machine, and a work-indexing means for shifting a work fabric panel relatively to the stitching point of said sewing machine, including a workgripping clamp, means for unloading and storing a work fabric panel after stitching has been completed comprising, a work supporting member carried on said sewing unit at one side of the path of travel of a fabric panel gripped in said work gripping clamp, andv References Citedin the file of this patent UNITED STATES PATENTS 1,243,679 Allen Oct. 23, 1917 1,709,788 Greene Apr. 16, 1929 1,953,300 Holman Apr. 3, 1934 2,465,232 Jones et 'al. Mar. 22, 1949 2,674,965 Mclnerney et a1 Apr. 13, '1954 2,773,585 Caulfield Dec. 11, 1956 2,899,919 Myska Aug. 18, 1959 2,908,378 Brown et al. Oct, 13, 1959

Claims

1. IN A SEWING UNIT HAVING A SEWING MACHINE, A WORK INDEXING MEANS FOR SHIFTING A FABRIC RELATIVELY TO THE STITCHING POINT OF SAID SEWING MACHINE COMPRISING AN ENDLESS CONVEYOR SUPPORTED FOR MOVEMENT IN ONE DIRECTION RELATIVELY TO THE STITCHING POINT OF SAID SEWING MACHINE, MEANS CONSTRAINING SAID ENDLESS CONVEYOR IN AN ELONGATE LOOP HAVING SUBSTANTIALLY STRAIGHT AND PARALLEL ELONGATE LIMBS, A PLURALITY OF PAIRS OF WORK GRIPPING CLAMPS CARRIED BY SAID ENDLESS CONVEYOR, THE WORK GRIPPING CLAMPS OF EACH OF SAID PAIRS BEING CARRIED IN SPACED RELATION ALONG SAID ENDLESS CONVEYOR FOR ENGAGEMENT WITH OPPOSITE EXTREMITIES OF A WORK FABRIC PANEL, EACH OF SAID WORK GRIPPING CLAMPS COMPRISING A PAIR OF JAWS, MEANS SUPPORTING SAID JAWS FOR MOVEMENT RELATIVELY TO EACH OTHER INTO AND OUT OF WORK GRIPPING RELATION, MEANS DEFINING A STARTING POSITION OF ANY OF SAID PLURALITY OF PAIRS OF WORK GRIPPING CLAMPS RELATIVELY TO SAID SEWING MACHINE STITCHING POINT, SAID PLURALITY OF PAIRS OF WORK GRIPPING CLAMPS BEING SPACED ALONG SAID CONVEYOR SUCH THAT IN THE STARTING POSITION THE LEADING WORK GRIPPING CLAMP OF A PAIR OF CLAMPS ON ONE OF SAID CONVEYOR LINKS IS DISPOSED DIRECTLY OPPOSITE THE TRAILING WORK GRIPPING CLAMP OF ANOTHER PAIR OF CLAMPS ON THE OPPOSITE CONVEYOR LIMB, AND A PAIR OF WORK CLAMP OPENING SOLENOIDS CARRIED ON SAID SEWING UNIT, SAID SOLENOIDS BEING DISPOSED FOR OPERATIVE ENGAGEMENT IN THE STARTING POSITION OF SAID WORK GRIPPING CLAMPS TO OPEN SIMULTANEOUSLY BOTH OF A DIRECTLY OPPOSITE SET OF LEADING AND TRAILING WORK GRIPPING CLAMPS.