US2641211A

US2641211A - Automatic bar tacking control mechanism for buttonhole sewing machines

Info

Publication number: US2641211A
Application number: US235290A
Authority: US
Inventors: Minkowitz George
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-07-05
Filing date: 1951-07-05
Publication date: 1953-06-09
Anticipated expiration: 1970-06-09

Description

June 9, i953 G, MINKOWITZ 2,641,211

- AUTOMATIC BAR TACKING CONTROL MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed July 5, 1951 4 Sheets-Sheet 1 T0 LATEAL MOVEMENT m nfig filhlllnlnnllnullinillfm 0F WQRK HOLDER 25 TO LONGITUDINAL MOVEMENT 0F 7 worm women INVENTOR.

George Minkowiiz BY ATTORNEY June 9, 1953 G. MINKOWITZ 2,641,211

' AUTQMATIC BAR TACKIM} CONTROL MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed July 5, 1951 4 Sheets-Sheet 2 INVENTOR. George Minkowitz BY ATTORNEY June 9, 1953 MINKOWITZ AUTOMATIC BAR TACKING CONTROL MECHANISM FOR BUTTONHOLE SEWING MACHINES 4 Sheets-Sheet 3 Filed July 5, 1951 ATTORNEYS ll IlllHll In a June 9,, 1953 e. MINKOWITZ 2,641,211

AUTOMATIC BAR TACKING CONTROL MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed July 5 1-951 4 Sheets-Sheet 4 ATTORNEY Patented June 9, 1953 OFFICE AUTOMATIC BAR TACKING CONTROL MECHANISM FOR BUTTONHOLE SEW- ING MACHINES George Minkowitz, New York, N. Y.

Application July 5, 1951, Serial No. 235,290

17 Claims. 1

The present invention relates to automatic bar tacking control mechanism for buttonhole sewing machines, and. particularly for buttonhole sewing machines of the type in which the needle bar carries out vertical and transverse reciprocal stitching motions and the workpiece is mounted in a work holder which moves cyclically over the bed plate of the machine first in one longitudinal direction, then for a short distance in a transverse direction, then in the opposit longitudinal direction and finally back to its starting position for accurate positioning of the workpiece relative to the needle bar in accordance with the desired size and shape of the buttonhole to be stitched.

One object of my invention is to provide bar tacking control mechanism which permits bar tacking at any desired point of the cyclic movement of the work holder.

Another object of the invention is to provide bar tacking control mechanism which causes the needle bar to carry out a predetermined number of bar tacking stitches for each bar tack.

Still another object of the invention is to provide control means in which the number of stitches for each bar tack can be varied easily and conveniently.

Still a further object of th invention is to provide a bar tacking control mechanism which operates automatically and reliably, which is relatively simple in construction and in which the several elements are sturdy and capable of continued operation for a long time Without breakdown or significant wear.

These objects are accomplished according to the present invention by the combination of elements set forth in detail in the following description, defined in the appended claims and illustratively exemplified in the accompanying drawings, in which:

Fig. 1 is a partial side view of a buttonhole sewing machine having bar tacking control mechanism according to the present invention, certain parts being broken away and others being shown in vertical section;

Fig. 2 is a more or less diagrammatic perspective view of the front part of the machine showing the mutual relation of the work holder, the I machine with the cover plate and the bar tacking control mechanism removed;

Fig. 4 is a view similar to that of Fig. 3 showing the various parts in a different position;

Fig. 5 is a view similar to that of Fig. 3 with one element of the bar tacking control mechanism according to the present invention in place;

Fig. 6 is a top view of the machine with the cover plate and some elements of the control mechanism according to the present invention mounted thereon;

Fig. 7 is an exploded perspective view of the bar tacking control mechanism according to the present invention; and

Fig. 8 is a detail view of a member carrying ex changeable cam elements.

Referrin now to the drawings, and first to Fig. 1, ll is the bed plate of a buttonhole sewing machine on which the usual hollow arm I2 with its open neck portion [2a is mounted by means of a hollow standard l3.

Lengthwise of the hollow arm [2 extends the main drive shaft I4 of the machine which can be driven, as usual, at the rear end of the arm l2 through a pulley l5. A cranked portion [6 of the main drive shaft [4 actuates a vertically reciprocating transmission member I! connected by means of a releasable clutch IS with a second vertically reciprocating transmission member l9. A crank 20 at the lower end of the transmission member I9, is mounted underneath the bed plate I l of the machine and transmits through a rocking arm 2! and pawl and ratchet means which are not shown, but which may be, for instance, of the type disclosed in the applicants prior U. S. Patent 2,119,111, a stepwise rotation to a stepping cam 22 with two cam grooves (not shown). Two cam followers 23 and 24 ride in the cam grooves of the cam 22 and transmit through

links

25 and 26 the desired longitudinal and transvers movements to the work holder 21 (see Fig. 2). The releasable clutch I8 is normally held in engaged position by a spring 28 and has secured thereto a lever 29 which projects upwardly into the hollow arm I2 of the machine and which effects the gilease of clutch [8 when rocked about its pivot When the clutch I8 is engaged, the stepping cam 22 is driven stepwise from the main drive shaft 14 of the machine and transmits by means 3 of the cam followers 23, 24 and

links

25, 26 to the work holder 21 carrying the workpiece 3| the desired longitudinal and transverse movements relative to the needle bar 32 which are necessary for the stitching of a buttonhole of the desired size and shape (see Fig. 2)

The needle bar 32 receives its transverse motions in a manner not shown but well known in the art (see, for instance, U. S. Patent 1,559,539) from a lengthwise reciprocating link member 33, the rear end of which is adjustably mounted by means of a screw 34 in a slot 35 of a rocking element 36 on top of the hollow arm l2. A second link 31 is connected to the rocking element 36 at 38 and projects rearwardly into the neck portion [2a of arm 12. The rear end 31a of link 31 is bent downwardly and then rearwardly to ex! tend adjacent to and past the upper end of lever 29 (see Figs. 1 and 3 to About half way of its length, the link 31 has inside of the neck portion l2a of arm I2 an enlarged portion 39 provided on one side with a notch 40 and having mounted thereon a downwardly projecting pin 4!. The pin 4| extends into an arcuate slot 42 provided in one arm 43 of a bell crank lever 44 pivoted on a fixed vertical fulcrum 45. A spring 46 extending between the link 31 and a stationary pin 41 tends to pull the link 31 toward the fulcrum 45 of lever 44 until a stop pin 48 on the arm 43 rests in the notch 40 of link 31. This short-stitch position of link 31 is illustrated in Figs. 3 and 5 showing the rear end 31a of link 31 spaced from the top end of lever 29, so that no force is exerted on lever 23 and clutch I8 is held engaged by its spring 28.

The bell crank lever 44 is rocked back and forth about its fulcrum 45 by means of a cam follower 49 carried at the end of the second arm 50 of the bell crank lever 44 and riding in a cam groove 54 of a'rotary cam 52 which is driven continuously from the main shaft [4 of the machine by means of bevel gears 53.

It will be seen that by moving the link 31 counterclockwise from its short-stitch position shown in Figs. 3 and 5, to its long-stitch position shown in Fig. 4, the pin 41 will be displaced in the slot 49 of the bell crank lever 44 away from the fulcrum 45. Thus when the bell crank lever 44 rocks, the lengthwise stroke of

links

31 and 33 will be greater when link 31 assumes the position shown in Fig. 4 than when it is in the position shown in Figs. 3 and 5, with a corresponding increase in the transverse movements of the needle bar 32. A cover plate 54 closes the neck portion 211 of the hollow arm [2 of the machine at the top.

The stepping cam 22 has a central shaft 55 which takes part in the stepwise rotation of the cam and projects upwardly through the bed plate I l. A gear wheel 56 is keyed to the top of shaft 55 underneath the arm 12.

Mounted on the cover plate 54 is a tension disc assembly comprising two tension discs 51 and 53 and a spring 59 surrounding a pin 60 and resting at its upper end against a pin head 6| and at its lower end against the upper tension disc 51. The upper tension disc 51 can be lifted by means of a pin 62 projecting downwardly below the cover plate 54 and into the path of the link 31 when the latter is displaced from its position shown in Fig. 3 to that shown in Fig. 4. Upon such displacement, a bevelled portion 63 provided on the link 31 engages the lower end of pin 62 and raises the same to lift tension disc 51, thus relieving the tension between disc 51 and 58 and permitting free feeding of the thread between the two discs.

The machine as described so far is old in the art and does not form part of the present invention.

In order to effect automatic control of the bar tacking operation of the machine, a device is provided for accomplishing release of the clutch [8, for instance, by a shifting of the link 31 from its short-stitch position shown in Figs. 3 and 5 to its long-stitch position shown in Fig. 4, whereby the rear end 31a of link 31 acts upon the upper end of lever 29 to shift the same to clutch release position, means actuated by a part of the work holder drive, such as shaft 55, to operate said clutch release device whenever the Work holder 21 reaches a bar tacking position, a stitch counter, means connected with the needle bar and mounted, for instance, on the bell crank lever 44, for actuating said stitch counter whenever the clutch I8 is released, means controlled by said stitch counter to render said clutch release device inoperative after a predetermined number of bar tacking stitches and means operative after said clutch release device has been rendered inoperative for restoring said stitch counter to starting position before the work clamp 21 reaches its next bar tacking position.

In the embodiment of the invention illustrated in Figs. 1 to 8, the control mechanism is composed entirely of mechanical parts.

A pin 54 is mounted in the cover plate 54 and projects vertically upward therefrom. A sector toothed ratchet gear member 65 is rotatable on the pin 64. The upper part of the periphery of the gear member 65 is subdivided into two

toothed sectors

66, 61 mutually displaced by and, in the example shown, each comprising six teeth. The peripheral portions 66a, 61a of the ratchet gear member 65 between the toothed sectors are smooth. On its lower surface, the ratchet gear member 65 is provided with two diagonally opposed radial recesses 68, 69, aligned, respectively, with the first teeth of the two toothed sectors 66, 61 (see Fig. 8). Mounted in each of the radial recesses 68, 69 is a radially projecting cam element 10, each cam element being secured interchangeably in its recess, for instance, by means of a screw 1|. The ratchet gear member 65 carries on its upper surface an eccentric pin 12 projecting upwardly parallel to the shaft 64. A gear wheel member 13 having an upwardly projecting hub portion 14 of smaller diameter is rotatably mounted on pin 64 above the ratchet gear member 65. The gear wheel member 13 and its hub are provided with an arcuate slot 15 accommodating the eccentric pin 12 of the ratchet gear member 65. A collar 16 secured to pin 64 on top of the hub 14 of gear wheel member 13 serves to hold the assembly securely in place.

In a bracket 11 projecting on one side from the hollow arm l2 (see Figs. 1, 3 to 5 and '7), a bearing sleeve 18 is provided to support a vertical shaft 19 rotatable about its own axis. but held against movement lengthwise of its axis. At the lower end of shaft 19 directly below the arm I2 of the machine, the shaft 19 carries a gear wheel 83 secured thereto and in mesh with the gear wheel 56 at a 1:1 ratio. The upper portion of the shaft 19 carries above the cover plate 54 and at the level of the gear wheel 13, a gear wheel 8| resting on a collar Sid and secured to the shaft 19. Gear wheel 8| meshes with the gear wheel 13 at a 1:1 ratio. Secured to the bell crank lever 44 is a pawl support element 82 having a horizontal portion 83 fixed to the bell crank lever 44, a vertical portion 84 extending through a slot 85 in the cover plate 54, and a second rearwardly projecting horizontal portion 86. A curved pawl carrying member 81 is mounted at one end thereof on the horizontal portion 86 of support 82 and secured thereto by screws 88. A feed pawl 8'9 is pivotally mounted on the other end of pawl-carrying element 91 and urged against the upper part of the periphery of ratchet gear member 65 by means of a spring 99.

A stationary pawl support 9| is mounted by means of screws 92 on a block 93 secured to the upper surface of the cover plate 54. The pawl support 9I carries on the side of the ratchet gear member 65 opposite that along which the feed pawl 89 moves, a pivoted holding pawl 94 which is urged against the periphery of the ratchet gear member 65 by means of a spring 95.

A stationary bracket 99 secured to the arm I2 of the machine adjacent the cover plate 54 opposite the bracket 11 has pivoted thereto a bell crank lever 91 having one arm 98 extending substantially lengthwise of the machine at a small distance from the periphery of the cover plate 54 and a second arm 99 projecting partly across the cover plate. The arm 98 has secured thereto an extension slide I99 which can be shifted relative to the arm 98 lengthwise thereof and which carries at its free end an abutment I9I transversely adjustable relatively to the extension slide I99. The transverse arm 99 is formed with a longitudinal guide groove I92 accommodating slidably therein a cam follower slide I93 carrying at its free end a cam follower roller I94. A slide rod I95 is guided underneath the cover plate 54 and has one end projecting laterally from the arm I2 of the machine into engagement with the abutment member I9I. The other end of the slide rod I95 carries a roller I99 which contacts the link 31 near its rear end 3111.

The control mechanism described operates as follows: When the main drive shaft I4 turns stepwise rotary motion is transmitted through the transmission members I1 and I9 and the clutch I 8 to the rotary cam 22. This causes the work holder 21 to move stepwise in the described cycle. During this movement, the buttonhole is stitched due to the vertical and trans verse reciprocation of the needle bar, the transverse movements of the latter being relatively small, as indicated at 32a in Fig. 2 since the link 91 is retained by the spring 46 in its shortstitch position shown in Figs. 3 and 5. As the stepping cam 22 rotates, it causes simultaneous,

stepwise rotation of the shaft 55 and, hence, through

gear wheels

56, 89, shaft 19 and gear wheel 8|, of gear wheel 19 around pin 64. Gear wheel I9 rotates through 360 for each complete cycle of the work holder 21. When gear wheel 13 during its rotation in clockwise direction, as

seen in Fig. '1, has reached a position in which the.

rear end of its arcuate slot 15 abuts against the pin 12 of ratchet gear member 65, the latter is constrained to participate in the rotary movement of gear wheel 13. This causes the cam elements 19 to advance in clockwise direction, until, at a predetermined point of the rotation of gear wheel 13, which in the example shown coincides with the completion by the work holder 21 of one of its transverse movements, one of the cam elements 19 has reached the upper broken line position indicated in Fig. 6, in which it has engaged the cam follower roller I94 of cam follower slide I93 and has caused the bell crank lever 91 to swing from its normal inoperative position, indicated in dot and dash lines in Fig. 6, to its operative position. This movement shifts slide rod I substantially transversely against link 31 and causes the latter to move from its short-stitch position shown in Figs. 3 and 5 to its long-stitch position shown in Fig. 4. In this position of link 31, the continued movement of bell crank lever 44 causes the needle bar 32 to carry out long transverse movements for bar tacking stitches, as shown at 321) in Fig. 2. As link 31 is shifted, its bevelled portion 63 cooperates with pin 62 of the

tension disc assembly

51, 58, 59, 89, 9| to relieve the tension on the thread, thus permitting free passage of the latter for the execution of the long bar tacking stitches. Shifting of the link 31 from its short-stitch position to its long-stitch position also causes the rear end 31a of link 31 to engage the upper end of clutch lever 29 and to shift the latter for release of the clutch I8. Thus, the cam 2'2 is disconnected from the main drive shaft I4, and the work holder 21, shaft 55 and

gear train

56, 89, BI and 13 are stopped as long as bell crank lever 91 is retained in its operative position.

At the moment when bell crank lever 91 is shifted to its operative position 'by one of the cam elements 19, the ratchet gear member 65 has reached a position in which the first tooth of one of its

toothed sectors

96, 61 is within reach of the feed pawl 89 and the first tooth of the opposite toothed sector 61 is engaged by the holding pawl 94. As the feed pawl 89 continues its reciprocal movement derived from the rocking movements of the bell crank lever 44, it starts rotating the ratchet gear member 65 one step for each complete bar tacking stitch of the needle bar 32. Fig. 6 shows in full lines the positions assumed by the various elements after completion of the second bar tacking stitch. Durin this advancement of the ratchet gear member 55 relative to the now stationary gear wheel member 13, the pin 12 advances in the arcuate slot 15. After a predetermined number of bar tacking stitches, dependent upon the shape of the operating cam element 19 and the adjusted position of the cam follower slide I93 relative to the lever arm 99, the cam element 19 moves past the cam follower roller I94 and permits return of the bell crank lever 91 to its inoperative position. If the cam member is shaped as shown in Figs. 6, 7 and in the lower part of Fig. 8, release of the bell crank lever 91 takes place after three stitches, as shown by the lower broken-line position of cam element 19 in Fig. 6. If it is desired to make a different number of bar tacking stitches for the formation of a bar tack, one or both cam members 19 can be replaced. For instance, a cam member 19a as shown at the top of Fig. 8, will hold the bell crank lever 91 in its operative position for the duration of six stitches. It will be understood that the cam element may be given any desired form so as to provide for any desired number of stitches, as shown, for instance, by the dotted line in the upper part of Fig. 8 indicating how the cam element would be shaped if it were desired to carry out four bar tacking stitches in the formation of a bar tack.

When the bell crank lever 91 is released, the link -31 returns to its short stitch position shown in Fig. 3 under the action of spring 46 and this return movement is transmitted through the slide rod I95 and abutment I9I to bell crank 1ever 91 which is thus restored to its inoperative position in which cam follower roller I04 projects into the path of the cam elements in and is ready for the initiation of the next bar tacking operation.

As soon as link 31 returns to its short-stitchposition, lever 29 is freed and clutch [8 becomes reengaged under the action of its spring 28, whereupon stepping cam 22, work holder 21 and

gear train

56, 39, 8| and I3 resume their step-wise movements. Assuming that bell crank lever 91 has been freed for return to its inoperative position after three stitches, feed pawl '89 will still continue to act upon the remaining teeth of toothed sector 68, and since the feed pawl drive is faster than the gear drive from the cam shaft 55, ratchet gear member 65 will continue to advance relative to gear wheel member 13 until the last tooth of toothed sector 66 has passed out of reach of feed pawl 89. Thereafter, the ratchet gear member 6'5 will be retained in its position by the holding pawl 94 until the gear wheel member 73 has caught up with the ratchet gear member 65 and the rear end of slot 15 abuts against pin 12. When the toothed sector 66 has passed out of the reach of feed pawl 89 and during the further rotation of the ratchet gear member 65 by the gear wheel member E3, the feed pawl 89 will idle on the smooth peripheral surface 67a of the ratchet gear member 65 until on completion of the next transverse movement of the work holder 27 in the opposite direction the other cam element 10 engages the cam follower roller I04 and shifts the bell crank lever 91 to its operative position. Simultaneously, the first tooth of the other toothed sector 61 has come into position for engagement by the feed pawl 89, whereupon the described bar tacking operation will be repeated at the other end of the buttonhole.

I claim:

1. Bar tacking control mechanism for buttonhoie stitching machines of the type having a main drive shaft, a vertically and transversely reciprocable needle bar, means actuated by said main drive shaft for causing said needle bar to carry out its stitching motions, a workholder movable in a horizontal plane underneath said needle bar longitudinally and transversely relative to the machine, a workholder drive for stepwise and cyclically shifting said workholder, and means including a releasable clutch for coupling said workholder drive to the main drive shaft, said bar tacking control mechanism comprising a rotary member coupled to the workholder drive, a sector toothed ratchet gear member, a lost motion coupling between said two members operative to transmit rotary motion in one direction from said rotary member to the ratchet gear member when the two members assume a certain coupling position with respect to each other, and per mitting said ratchet gear member to advance relative to said rotary member from said coupling position for a fraction of a turn, a reciprocable member continuously actuated by the main drive shaft in synchronism with the transverse movement of the needle bar, a feed pawl supported on said reciprocable member and permanently biased toward said ratchet gear member to advance the latter stepwise in the same rotary direction a predetermined amount for each stitching movement of said needle bar whenever any of its ratchet teeth are within reach of said pawl, a cam element on said ratchet gear member, and a device including a cam follower controlled by said cam element to release said clutch at a predetermined stage of each advancement of said ratchet gear member by said rotary member and to keep it released during at least part of each advancement of said ratchet gear member by said pawl, the various elements being so proportioned and related that the clutch is released and the workholder drive and the rotatable member are stopped whenever the workholder reaches a predetermined point of its cycle at which the ratchet gear member is positioned for engagement of its ratchet teeth by said pawl, whereupon the ratchet gear member and its cam are advanced by said pawl relative to said rotatable member for a predetermined number or steps at the end of which the cam member has reached a position to permit reengagement of said clutch, thereby causing said rotatable member to resume its motion and to return to its coupling position relative to the ratchet gear member for the start of a new cycle.

2. Bar tacking control mechanism according to claim 1, in which said feed pawl is adapted, on cooperation with a toothed sector of said ratchet gear, to drive the latter at a rotary speed considerable in excess of that transmitted to said ratchet gear by said rotatable member.

3. Bar tacking control mechanism according to claim 1, in which said rotatable member and ratchet gear member are coaxial and said lost motion coupling includes an arcuate concentric slot in one of said members and an eccentric pin projecting from the other member parallel to the common axis of rotation into the arcuate slot of the first member.

4. Bar tacking control mechanism according to claim 1, including a holding pawl permanently biased toward said ratchet gear member to cooperate with teeth of said ratchet gear member in the interval between stepwise advancements of the latter by said feed pawl.

5. Bar tacking control mechanism according to claim 1, in which said cam follower includes a roller biased towards said ratchet gear member and displaceable by said cam element.

6. Bar tacking control mechanism according to claim 1, in which said device for releasing said clutch comprises a bell crank lever rockable about a fixed fulcrum between a normal operative position and an inoperative position, said bell crank lever carrying on one of its arms said cam follower, the latter projecting in inoperative position of said bell crank lever into the path of said cam element at a point so that said bell crank lever is shifted to its operative position at the moment when the first tooth of a toothed sector of the ratchet gear comes into reach of said feed pawl, said cam element and cam follower arm of said bell crank lever being shaped and arranged to hold the latter in its operative position until the ratchet gear member has been rotated by said feed pawl through a predetermined number of steps, the second arm of said bell crank lever being adapted and arranged to act upon and to release said clutch when said bell crank lever is shifted to its operative position.

7. Bar tacking control mechanism according to claim 6, including a slide having one end in engagement with the second arm of said bell crank lever and its other end adapted and arranged to act upon and release said clutch when said bell crank lever is shifted to its operative position.

- 8. Bar tacking control mechanism according to claim 1, in which said cam element, which is shaped to retain said clutch release device in its clutch release position until after the ratchet gear has been moved through a predetermined number of steps by the feed pawl, is exchangeably secured to the ratchet gear member to permit its replacement by a cam element of a shape to hold the clutch release device in clutch release position for a different number of steps.

9. Bar tacking control mechanism according to claim 1, in which said rotatable member is a gear wheel member, the coupling between said Workholder drive and said gear wheel member including a shaft connected to said workholder drive and carrying a gear wheel in mesh with said gear wheel member.

10. Bar tacking control mechanism according to claim 1, in which said rotatable member is geared to said workholder drive for stepwise rotation through 360 for each complete cycle of said workholder.

11. Bar tacking control mechanism according to claim 10, in which said ratchet gear member has two peripherally toothed sectors mutually displaced by 180 and two toothless peripheral portions between said toothed sectors and two radially projectin diametrically opposed cam elements,

12. Bar tacking control mechanism for buttonhole stitching machines of the type having a main drive shaft, a vertically and transversely reciprocable needle bar, an oscillating member continuously actuated by said main drive shaft, a link transmitting the motion of said oscillating member to said needle bar, said link being adjustably' connected to said oscillating member to be shiftable from a normal, short-stitch position to a long-stitch position, a workholder movable in a horizontal plane underneath said needle bar longitudinally and. transversely of the machine, a workholder drive for stepwise and cyclically shifting said workholder, and means including a releasable clutch for coupling said workhol'der drive to the main drive shaft, said bar tacking control mechanism comprising a rotary member coupled to the workholder drive, a sector toothed ratchet gear member, a lost motion coupling between said two members operative to transmit rotary motion in one direction from the rotary member to the ratchet gear member when the two members assume a certain coupling position with respect to each other and permitting said ratchet gear member to advance relative to said rotary member from said coupling position for a fraction of a turn, a feed pawl supported on said oscillating member and permanently biased towards said ratchet gear member to advance the latter stepwise in the same rotary direction a predetermined amount for each stitching movement of said needle bar Whenever any of its ratchet teeth are within reach of said pawl, a cam element on said ratchet gear member, and a device including a cam follower controlled by said cam element to shift said link from its short-stitch position to its long-stitch position at a predetermined stage of each advancement of said ratchet gear member by said rotary member and to release said clutch and keep it released for at least part of each advancement of said ratchet gear member by said pawl, the various elements being so proportioned and related that the clutch is released and the workholder drive and the rotatable member are stopped whenever the workholder reaches a predetermined point of its cycle at which the ratchet gear member is positioned for engagement of its ratchet teeth by said pawl, whereupon the ratchet gear member and its cam are advanced by said. pawl relative to said rotatable member for a number of steps, corresponding to a predetermined number of long transverse bar tacking stitches, at the end of which the cam member reaches a position to permit return of the link to its short-stitch position and reengagement of said clutch causing said rotatable member to resume its motion and to return, after passage of the toothed sector of the ratchet gear member out of reach of the pawl, to its coupling position relative to the ratchet gear member for the start of a new cycle.

13. Bar tacking control mechanism according to claim 12, in which said pawl is mounted on said oscillating member at a distance from the fulcrum of the oscillating member which is greater than the maximum distance between said fulcrum and the point where said link is connected to the oscillating member so that the stroke of the pawl is longer than the maximum stroke of the link.

14. Bar tacking control mechanism according to claim 12 in which said rotatable member and ratchet gear member are coaxially mounted on a pin parallel to and spaced from the rocking fulcrum of the oscillating member.

15. Bar tacking control mechanism according to claim 12, in which said device for releasin said clutch and shifting said link from its shortstitch to its long-stitch position comprises a bell crank lever rockable about a fixed fulcrum between a normal inoperative position and an operative position, said bell crank lever carrying on one of its arms said cam follower, the latter projecting in inoperative position of said bell crank lever into the path of said cam element whereby said bell crank lever is shifted to its operative position at the moment when a first tooth of a toothed sector of the ratchet gear comes into reach of said feed pawl, said cam element and cam follower arm of said bell crank lever bein shaped and arranged to hold the latter in its operative position until the ratchet gear member has been rotated by said feed pawl through a predetermined number of steps, the second arm of said bell crank lever being adapted and arranged to shift said link to its long-stitch position with simultaneous release of said clutch when said bell crank lever is shifted to its operative position.

16. Bar tacking control mechanism accordin to claim 15, including a slide having one end in engagement with the second arm of said bell crank lever and its other end disposed adjacent said link to shift the latter to its long-stitch position with simultaneous release of said clutch when said bell crank lever is shifted to its operative position.

17. Bar tacking control mechanism according to claim 15 for buttonhole stitching machines having a horizontal hollow arm provided with a central neck portion open at the top, said link for transmitting the motion of said oscillating member to said needle bar extending into said neck portion, said bar tacking control mechanism including a cover plate for said neck portion of said hollow :arm, a vertical pin mounted in and projecting upwardly from said cover plate, said gear wheel member and said sector toothed ratchet gear member being rotatably supported on said pin, a pawl carrier having a lower horizontal portion secured to said oscillating member underneath said cover plate, a vertical portion passing through an arcuate slot in said cover plate and an upper horizontal portion disposed adjacent said ratchet gear member on one side thereof,

1 I and supporting said feed pawl at. a, distance from the fulcrum of said oscillating member exceeding the maximum distance between said fulcrum and the point where said link is connected to; the oscillating member, said holding pawl being a holding pawl mounted on said cover plate on the opposite side of said ratchet, gear member, a bracket secured to said arm adjacent said cover, said clutch releasing bell crank lever being pivoted to, said bracket for rocking movements about a vertical axis above said cover plate in a plane: parallel to the lever, and a slide guided underneath said cover plate and having one end projecting laterally from said neck portion of said hollow arm into contact 12 with the second arm of said bell crank lever and its other end disposed inside that, hollow arm adjacent said link to shift the latter to its longstitch position with simultaneous release of said clutch.

GEORGE MINKOWITZ.

References Cited in the file of this patent.

UNITED STATES PATENTS Number Name Date 806,231 Allen Dec. 5, 1905 807,531 Allen Dec. 19, 1905