US1983263A

US1983263A - Pull-off mechanism for sewing machines

Info

Publication number: US1983263A
Application number: US681248A
Authority: US
Inventors: Edward B Allen; Maurice D Knox
Original assignee: Singer Co
Current assignee: Singer Co
Priority date: 1932-05-04
Filing date: 1933-07-20
Publication date: 1934-12-04
Anticipated expiration: 1951-12-04

Description

Dec. 4, 1934. E. B. ALLEN ET AL PULL-OFF MECHANISM FOR SEWING MACHINES Original Filed May 4, 1952 8 Sheets-Sheet l 1f du ardBAZZen Dec. 4, 1934. E. B. ALLEN ET AL PULL-OFF MECHANISM FOR SEWING MACHINES Original Filed May 4, 1932 8 Sheets--Sheet 2 k No w L W n h .I. z n i L .55 m FT d m m E m m fiLL L n W n n u ,H u m kw M m l N L n u a u H L, w QNI \A. N w wk N. w 5: m u MM k m H $1M V Wm v 1 H ||1 :1 I |l| H I ||||1 l1l| II III N R xw xx MN Fm WM L m ,L J I F N w QN e w w Dec. 4, 1934. E, ALLEN ET AL 1,983,263

PULL-OFF MECHANISM FOR SEWING MACHINES Original Filed May 4, 1932 8 Sheets-Sheet 3 Wit'webb: Mauricelllinoz NCW.

Dec. 4, 1934. E. B. ALLEN ET AL PULL-OFF MECHANISM FOR SEWING MACHINES 8 Sheets-Sheet 4 Original Filed May 4, 1932 grwcxwbob Edward B/Illen and Mduricefl Knox Dec. 4, 1934. B ALLEN AL 1,983,263

PULL-OFF MECHANISM FOR SEWING MACHINES Original Filed May 4, 1932 8 Sheets-Sheet 5 EdwarZB.AlZen Hauriqefl Knox De.4, 1934. BALLEN HAL 1,983,263

PULL-OFF MECHANISM FOR SEWING MACHINES Original Filed May 4, 1932 8 Sheets-Sheet 6 I g vwe/rvbom Eda/cat0515- Allen WVwebd ar ad Maurace 17.1fm

wmw I v m Dec. 4, 1934.

E. B. ALLEN El AL PULL-OFF MECHANISM FOR SEWING MACH INES Original Filed May 4, 1932 8 Sheets-Sheet '7 awe/"430th Eduasdfifl lien flazl zlce D. Knox Dec. 4,' 1934. E. B. ALLEN ET AL PULL-OFF MECHANISM FOR SEWING MACHINES Original Fil ed May 4, 1932 8' Sheets-Sheet 8 Edi/r055 A lien Ma ii-:50. Knew Y K flvwww Patented Dec. 4, 1934 PATENT OFFICE PULL-OFF MECHANISM FOR SEWING MACHINES Edward-B. Allen and Maurice D. Knox, Newtown, Conn., assignors to The Singer Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Original application May 4, 1932, Serial No. 609,083. Dividedand this application July '20,

1933, SerialNo. 681,248

12 Claims. (01. 112-242) This invention relates to sewing machines of the pyramid-purl lock-stitch .buttonhole type.

To fully appreciate the 'novel features of the present improvement, afull knowledge of the characteristics of the pyramid-purl stitch is necessary and, with this object in view, the folembodying the invention. Fig. 2 is a reverse side lowing explanation is given:

1 The formation of the pyramid-purl seam is accomplished by the cooperation of an upper eye- 9 pointed zigzag or laterally vibrating needle with an under thread-mass or bobbin associated with a loop-taker which seizes thread-loops from the needle below the work and expands such loops for passage about the under" thread-mass or 5 at the "upper side of thework and embrace the straight needle-thread. In the formation of such a pyramid-purl seam along the sides of a buttonhole, about twenty-thousandths of aninch of needle-thread is used per stitch while about three-sixteenths of an inch of bobbin-thread must be supplied from the bobbin and pulled upwardly through the work by the take-up in drawing up the needle-thread loop. The tension on thebobbin-thread must necessarily be light Very strong. 1

These requirements make it very difficult to properly and uniformly sew the pyramid-purl lock-stitch'seam athigh speeds, as the relation light bobbin-thread-tension is an unnatural one and the threads must be carefully handled in the formationtof the stitch to avoid undue strain or interference with the free thread-delivery.

The invention has for an object to provi'deimproved pull-off mechanism adapted, more particularly, for a pyramid-purl buttonhole sewing machine.

With the above and other objects in view, as

will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages while the tension on the needle-thread must be of the heavy needle-thread tension to the very attained thereby will be readily understoodby those skilled in thear't.

This application is a division of application Serial No. 609,083, filed May4, 1932.

In the accompanying drawings, Fig. l is a side elevation of. a buttonhole sewing machine elevation of the machine. Fig. 3 is a rear end elevation of the machine. Fig. 4 is' a bottom plan view. Fig. 5 is a top-plan view of the bracket-arm of the machine. Fig. 6 is a front end elevation. Fig. 7 is a front face view of the rotary hook mechanism, the hook beginning its idle rotation. Fig. 8 is a section on the line 88, Fig. 17, with the rotary hook and bobbin-case in elevation. Fig. 9 is a view similar to Fig. 7 show ing the initial engagement of the bobbin-thread pull-off device with the bobbin-thread; the hook having executed approximately the first half of its idle rotation.

Fig. 10 is a'view showing the pull-off device at drawn off of the beak of the hook after having beencast about the bobbin-case. similar view at a slightly later stage showing the needle-loop drawn up safely beyond the point of the hook which is about to begin its idle rotation. Fig. 16 is a view similar to Fig. 11 showing the effect of the auxiliary'bobbin-thread pull-off device. Fig. 17 is a top-plan view of the bobbinthread pull-off devices in the positions shown in Fig. 16. Fig. 18 is'a horizontal section through the hook and bobbin-case bodies on the line 18-18, Fig. 10. Fig. 19 is a diametrical section through the bobbin-case.

Fig. 20 is a front viewof the bobbin-thread pulloff device and the means for actuating it. Fig. 21 is a section on theline 21-21, Fig. 4. Fig. 22 is a section on the line 2222, Fig. 4. Fig. 23 is a plan view of the gearing under the sewing machine bracket-arm which controls the amplitude of vibration of the needle-bar vibrating mechanism and drives the feed-wheel. Figs. 24 and 25 are sections on the lines 2424 and 25-25, respectively, Fig. 23. Fig. 26 is a top-plan view of a purl-stitch seam such as is commonly used in Fig. 15 is a sewing buttonholes. Fig. 27 is a bottom plan view of the seam. Fig. 28 is a cross-sectional View of the seam. Fig. 29 is a disassembled perspective View of the rotary hook. Fig. 30 is a disassembled perspective view of the bobbin-case, and Fig. 31 is an enlarged section through the hook-body and bobbin-case.

Referring first to Figs. 26, 27 and 28, the pyramid-purl seam which the present machine is designed to sew comprises the fabric a on the under face of which is disposed the zigzag bobbin-thread 19 formed into loops 0 which are drawn through the material and tothe center line between the zigzag needle-punctures d where they are interlocked with the straight needle-thread t at the upper side of the fabric.

The machine chosen for the purposes of the present disclosure has a frame including the bed 1, from which rises the hollow standard 2 of the gooseneck 3 terminating in the head 4. Journaled in the gooseneck 3 is the main-shaft .5 having at its front end the take-up operating crank 6 and the needle-bar reciprocating crank 7 which is connected by the link 8 to the needle-bar 9 journaled in the usual needle-bar gate 10 which is fulcrumed at 1.1 to perform vibrating movements. The take-up crank 6 actuates the usual bell-crank take-up lever 12, Fig. 6, which is an.- chored by the link 13 to the head 4.

The needle-bar vibrating mechanism is constructed substantially in accordance with the disclosures of the Allen Patent No. 1,629,139, of May 17, 1927, and the Allen patent application Serial No. 367,511, filed May 31, 1929. This mechanism comprises a gear 14, Fig. 1, on the main-shaft 5 which drives a gear 15 of double the number'of teeth carrying two diametrically opposedv pins 16,, Fig. 5, meshing with a star-wheel 17 fixed to the vertical shaft 18 which is given a step-by-step rotary motion. Through a suitable train of

upper gears

19, 20, 21 and 22,. the shaft 18 drives the shaft 23 and imparts a half-rotation to such shaft for each step of movement of the shaft 18. The shaft 23 has a head 24 at its upper end in which is mounted a slide-block 25 carrying a crank-pin 26 connected by a link 27 to a lever 28 which, in turn, is connected by a link 29 to the needle-bar gate 10. The shaft 23 is hollow and. contains a vertically movable pin 30 having an inclined head 30, Fig. 2, at its upper end. The: inclined head,

36 engages a slot in the slide-block 25. The amplitude of the vibrations imparted to the needle-bar gate 10 thus depends upon the position or elevation of the control rod 30 within the shaft 23.

The control rod 30 is connected at its lower end, Figs. 2 and 23, to the forwardly extending arm 31 of a lever fulcrumed at 32 tothe gooseneck. 3. The lever 31 has a nose 33 bearing upon the upper face of a gear 34' fixed to the shaft 35 which carries the usual feed-wheel 36. The gear. 34 is driven from the shaft 18 through the usual train of reduction gears 37 and makes one complete rotation per buttonhole producing cycle. Thegear 1 34 has fixed to its upper face cam-blocks 38, Figs.

23 and 25, which pass under and elevate the nose 33 to increase the amplitude of vibration of the needle during the sewing of the barring stitches at the opposite ends of the buttonhole.

The work-clamp is of the usual construction shown, for example, in the patent to Wood, No. 1,613,634, of Jan. 11, 1927. It comprises the upper clamp-foot 39 carried by the clamp-lever 40 fulcrumed at 41 on the longitudinal slide-frame 42 mounted in the cross-slide frame 43; the

frames

42 and 43 being actuated through the usual connections 42', 43', Fig. 4, with the longitudinal and lateral feedcamgrooves 44 and 45, respectively, in the feed-wheel 36. The clamplever 40 has'a rearward extension or tail 46 which passes under the roller 47 on the vertically movable bar 48 hung from the clamp-lifting arm 49 journaled to move upon and relative to the usual stop-motion controlled rockshaft 50 at the side of the gooseneck.

The specific construction of the upper clampfoot 39 is fully disclosed in said application Serial No. 609,083, and forms no part of the invention claimed in the present divisional application.

The needle-bar 9 carries the usual needle 51 which operates through the transverse slot 52 in the stationary throat-plate 53 secured to the cross-slide frame 43. The throat-plate 53 is also formed with the usual longitudinal slot 54 through which the buttonhole-cutting knife 55 operates.

The stop-motion device is preferably constructed substantially in accordance with the disclosure of the Allen and Myers application, Serial No. 272,416, filed April 24, 1928. It comprises the usual tight and loose belt-

pulleys

56 and 57, respectively, on the main-shaft 5 which latter carries a gear 58 meshing with a gear 59 in 2-to-1 speed-reducing ratio. The gear 59 carries the double-notched stop-cam 60 with which cooperates the usual upwardly spnngpressed stop-plunger 61 carried by the tilting stop-motion lever 62 mounted on trunnions 63 fixed to the standard 2 and including the beltshipper arm 64 which operates the belt-shipper fork 65 carried by the slide-rod 66, Fig. 1, mounted in the lever 6'7 fulcrumed at 68 on the standard 2 and having an extremity 69 adapted to be acted upon by a tripping cam 70, Fig. 2, on the feedwheel shaft 35. This construction is substantially the same as that disclosed in the Allen Patent No. 1,659,937, of Feb. 21, 1928. When the stopmotion lever 62 is tilted to disengage the plunger 61 from the stop-cam 60, the point '71, Fig. 1, engages the tooth 72 on the rod 66 and slides the rod to the left sufiiciently to shift the belt onto the tight pulley 56. Near the end of the sewing operation, the lever 67 is tilted by the cam 70 to disengage the tooth 72 from the point 71 and allow the spring 73 to shift the rod 66 and belt-shipper fork 75 to carry the belt to the loosepulley 57. The machine now coasts to final stop-- ping position determined by engagement of the tripping point 74, Fig. 4, on the feed-wheel 36 with the latch-lever 75 which is disengaged from the notch 76 in the rod 77 secured to the arm 78' of the stop-motion lever 62.

The plunger 61 carries the usual block 79 which engages under the spring-pressed plunger 80 in the arm 81 fixed to the stop-motion controlled 1 rock-shaft 50 and gives such rock-shaft an impulse as the plunger 61 rises to final position in one of the notches in the stop-cam 60. This impulse given to the rook-shaft 50 is utilized for various purposes certain of which will be hereinafter described.

The main-shaft 5 is connected by the crossed clip-belt 82 to the lower shaft 83 which is driven at double the speed of the main-shaft and carries the cup-shaped rotary hook-body 84 formed with the loop-seizing beak 85 and a bearing groove 86, Fig. 13, for the flange 87 of the bobbincase 88. The crossed runs of the belt 82 are held apart by the thin sheet-metal separator plate 82' secured to the bed 1.

The bobbin-caseflange 87 is held in the bearing groove 86 of the hook-bodyby'means' of the removable gib screwedto theface of the hookbody. The bobbin-case 88 is formed in front of the bearing flange 8'7 with a guard-flange 89 which is somewhat larger in diameter than the bearing flange 87 and overlaps but, is spaced" slightly from the gib90.- The guard flange 89 prevents contact'of the front limb of the needleloop with the oiled bearing rib 87 during the loop-casting operation. No part of the hookbody projects beyondthe .plane of the exposed face of the gib 90. Back of thebeak .85, the hook-body is formed with a smoothly. rounded throat 91, Figs. 9 and 12, which draws out the needle-loop and causes the. limbs thereof to engage the tapered frontv and rear loop-spreading

walls

92, 93 ofthe bobbin-case 88. These

walls

92 and 93 spread the limbs of the needle-loop substantially equal distancesforwardly and rearwardly of the planeofrotation of the hook-beak and thus minimize the strains .on the thread and conduceto the free and easy casting of the needle-loop, withoutsubjecting the latterito sudcavity for the bobbin 94.which is journaledon the tubular arbor 95 in the center of the bobbin-case and held in place by the-latch-lever 96; The latch-lever96 is fulcrumed on the pin 9'7, Fig. 19, carried by the arbor95: and has a tail 98 which engages the inclined face 990i aspring-pressed plunger 100 mounted in the arbor 95. 7 Obviously, thelever 96 may be swung outwardly from the position shown in full lines in Fig. 19 to the dotted line position topermit removal and replacement of the bobbin. The latch-lever 96 has fixed to its under face at its outer end a 1eaf-spring 101 which extends towardthe fulcrum-pin 97 and is free to yield in the rectangular clearance slot 102 in the latch-lever 96. This spring 101 bears lightly at its inner free end upon the bobbin 94 and applies suffi'cient friction close to the arbor 95 to prevent overrunning of the bobbin and the the needle against deflection awayfrom the path of the hook-beak and assists in preventing the needle-loop from bowing outwardly on the wrong side of theneedle. There is applied to the bobbincase 88 a leaf-spring 108 having a notched tongue 109, Fig. 11, through which thebobbin-thread is delivered after it haspassedbetween the free end of the spring 108 and the underlying wall 109', Fig. 30, of the bobbin-case. The spring 108 applies a light tension to the bobbin-thread the amount ofwhich tension may be varied by loosening or tightening the tension-adjusting screw The front inclined'or conical wall 92 of the bobbin-case is formed with notches or pockets 111 for receptionof the free hook-shaped ends of the

rotation restraining arms

112, 113. These pockets 111 are preferably diametrically opposed and are substantially equidistant from the throatplate 53. The

arms

112, 113 are carried by

rockshafts

114, 115 which arejournaled in sleeves 116,

carried by the V-bracket 117 fixed to the tubular I the bed-lug 119 which steadies the sleeves and their supporting bracket 117 against turning on the supporting'stud 118.

Secured to the rear end of the rock-shaft 114 is a cam-follower. fork 121, Fig. 22, the upper arm 122 of which engages the opener-cam 123 on the cam-shaft 124 which is journaled in the bed-lug 119 andhas fixed to it a gear 125 meshing with a driving pinion 126 on the hook-shaft 83. The gear ratio isisuch that the shaft 124 runs at the same speed as the main-shaft 5, or half as fast as the hook-shaft 83. The under arm 127 of the fork 121 engages the cam 128the function of which isto retain the fork-arm 122 continuously in engagement with the opener cam 123. The opener cam 123 has a pointed active portion which gives a quick to-and-fro rocking.

impulse to the shaft 114 to open a passage be' tween the arm 112 and its pocket 111 at thejtime when the needle-loop is ready to pass between the arm 112 and the bobbin-case, as shownin Fig. 14. The shaft 1115; Fig. 21,, carries a cam-follower fork 129 the upper arm 130 of which engages thepointed opener-cam 131 on the shaft 124 and is,

retained 'inengagement with such cam by the engagement of the adjacent retainercam 132 withthe underarm 133 offthe. fork 129. The cam 131. opens a gap between the arm 113and its pocket 111in the bobbin-case at the time shown in Fig. 12 when the needle-loop is being drawn out preparatory to its passage around the bobbin-case. The arms 112,113 are thus independently operated and independently timed. Thus, their amplitudes of motion may be kept at a minimum, a desideratum of great importance ina mechanism intended to be operated at highspeed. The arm 112 is formed at its front side with a guard-flange 134 toguard the hooked endof the arm against. catching the needle-loop in the passage of the latter through the gap between the arm 112 and the bobbin-case at the period of the cycle slightly earlier than that shown in Fig. 14.

.Iournaled to move freely upon and relative to the hook-shaft 83, between the hook-body 85 and the gear 126, is thepull-off' lever 135 one arm of Whichis bent to overhang the hook and bobbincase bodies and formedwith a pull-off blade 136 having a thread-cam edge 137 and a needle-loop engagingedge'138, Fig. 11. The pull-off lever 135 is connected by alink 139 to a crank-pin 140 fixed to the exposed face of the gear 125 on the shaft 124. At the time of initial engagement of the pull-off blade 136 with the bobbin-thread, such blade is moving at a'speed considerably less than that of the rotary book 85. Thecrank 140 is about in the position shown in full lines in Fig. 20 and as it moves to its dead-center position 1 thus avoiding a jerking of-the bobbin-thread and minimizing any tendency toward overrunning or spilling of thread bythe bobbin. At the time of II and down to the needle 51.

maximum pull-off as shown in Fig. 11, the needle is throwing out a loop of thread for seizure by the hook-beak 85 and the inner edge 138 of the pull-off prevents bowing of the needle-loop on the wrong side of the needle and-causes the loop to be thrown out entirely at the side of the needle passed by the hook-beak 85. It will be seen that the bobbin-thread is fully pulled off while the loop-taker is making its idle rotation.

The amount of bobbin-thread pulled off (about inch) by the action of the blade 136 is sufiicient to permit the needle-thread to draw a loop of bobbin-thread entirely through to the upper side of the work and to the center line of the seam to form the well known pyramid-purl stitch. This amount of bobbin-thread is however not sufficient to properly form the barring stitches at the ends of the buttonhole. Means are therefore provided to pull off an increased supply of bobbin-thread for the barring stitches. To thisend there is fulcrumed on the screw 141, Figs. 4, 6, 16 and 17, an auxiliary pull-off lever 142 carrying a blade 143 adapted to overlie the pull-off blade 136, during the barring operation. The auxiliary pull-off Jblade 143 puts a bend in the bobbin-thread between the blade 136 and the work and hence increases the amount of bobbin-thread pulled off by the blade 136. The lever 142 is connected by the link 144 to one'arm 145 of a bell-crank lever, Fig. 2, the other arm 146 of which is connected by the link 147 to the rearwardly extending arm 148 of the lever 31 which controls the amplitude of vibration of the needle 51. The'auxiliary pulloff blade 143 is formed with a thread-engaging shoulder 149, Fig. 17, to hold the bobbin-thread against slippage toward the free end of the blade 143 as the main pull-off blade 136 advances to the extreme position shown in Fig. 17. 'When the sewing is proceeding alongthe sides of the buttonhole the auxiliary pull-off blade occupies T curved post 152; thence through the top tensiondevice 153; thence around the thread-guide 154 and through the side tension-device 155; thence past the guide 156, and through the check-spring 157 and under the guide 158 to the take-up 12 At the end of a sewing operation the upper tension 153 is opened by the wedge-bar 159, Fig. 2, connected to the lever 160 which is connected by a link 161 to the tilting stop-motion lever 62.- The lower tension 155 is opened at this time by the wedge-ended curved arm 162 carried by the rock-shaft 163 journaled in the head 4 and having fixed to it a rearwardly extending arm 164 engaging the forked end of an arm 165 fixed to the stop-motion controlled rock-shaft 50 previously referred to. The lower tension-device 155 applies a uniform tension to the needle-thread at all times when the machine is sewing. The check-spring 157 performs its usual function of taking up the slack thread between the eye of the descending 'needle and the Work. The upper tension-device 153 is automatically controlled to apply various additional amounts of tension to the needlethread to meet the requirements of sewing the ,first side, the return side and the barring stitches at the ends of the buttonhole. The mechanism for operating the upper tension device during the sewing will not be described herein as it forms no part of the present invention.

At the end of a sewing operation the needlethread is cut and nipped by the usual needlethread cutter. and nipper 166, Fig. 8, carried by the clamp-foot 39 and actuated by the springretracted rod 167, Fig. 2, which is released by upward movement of the arm 168, Fig. 6, when the operator pulls down on the lever 169 to open the work-clamp. This mechanism is constructed substantially in accordance with the disclosure of the clamp-opening and needle-thread-cuttertripping mechanism in the Allen application Serial No. 551,114, filed July 16, 1931.

Means are preferably provided for pulling from the supply, when the machine is at rest, an amount of needle-thread sufiicient to sew the next buttonhole. To this end there is fulcrumed on the bracket 175, Fig. 1, a spring-biased bellcrank lever having a short horizontal arm 176 engaging under the tail-piece 46 of the workclamp-lever 40. The long upstanding arm 177 of the bell-crank lever engages the needle-thread t between the stationary thread-

guides

150, 151 in the post 152. When the operator opens and closes the work-clamp 40, the pull-off lever is rocked to its dotted line position, Fig. 1, and returned to its full line position, thereby pulling oif from'the supply spool a length of needle-thread sufficient to sew the next buttonhole.

Having thus set forth the nature of the invention, what we claim herein is:--

' 1. A sewing machine having, in combination, a needle, a throat-plate, a rotary hook, a bobbincase journaled in saidrotary hook and having a bobbin-thread delivery guide in the upper portion thereof nearest the throat-plate, and a pull-off device having an inclined thread-cam edge movable horizontally in timed relation with said needle in each stitch-forming cycle into engagement with the bobbin-thread at a speed less than the speed of said hook.

2. A sewing machine having, in combination, a reciprocatory needle, a throat-plate, a rotary hook, a bobbin-case journaled in said rotary hook and having a bobbin-thread delivery guide in the upper portion thereof nearest the throatplate, and a horizontally oscillatory pull-off device arranged to engage the bobbin-thread between said delivery-guide and throat-plate once for each reciprocation of the needle.

3. A sewing machine having a needle, means for reciprocating said needle, a rotary hook, means for imparting to said hook a plurality of rotations for each reciprocation of said needle, a throat-plate, abobbin, a bobbin-thread pullofl adapted to engage the bobbin-thread between said bobbin and throat-plate, and means for moving said pull-off horizontally into engagement with the bobbin-thread once only for each complete reciprocation of said needle.

4. In a sewing machine, a reciprocating needle, a rotary hook making a plurality of rotations for each reciprocation of said needle, a bobbin, 3. bobbin-thread pull-off arm journaled coaxially with said hook, and means for oscillating said arm to engage the bobbin-thread once only for each complete reciprocation of said needle.

5. In a sewing machine, a rotary hook, a rotary hook-shaft carrying said hook, a bobbin, and an oscillatory bobbin-thread pull-01f journaled on said hook-shaft.

6. In a sewing machine, a reciprocating needle, a rotary hook having a loop-casting rotation followed by an idle rotation, a bobbin, and a thread-cam having an inclined thread-engaging edge for pulling off bobbin-thread during an idle rotation of said loop-taker, said means being ineffective to pull off bobbin-thread during the loop-casting rotation of said loop-taker.

7. A buttonhole sewing machine having, in

combination, stitch-forming mechanism, a workholder, means for relatively moving the stitchforming mechanism and work-holder to sew about a buttonhole, said stitch-forming mechanism including a reciprocating and laterally vibrating needle, and barring mechanism for increasing the amplitude of vibration of the needle to sew barring stitches at an end of the buttonhole, said stitch-forming mechanism also including a loop-taker, a bobbin, a bobbin-thread pulloff movable dilferentially with respect to the loop-taker in pulling off bobbin-thread, and means for increasing the amount of bobbinthread supplied by said pull-off during the sewing of the. barring stitches.

8. In a buttonhole sewing machine, a reciprocating and laterally vibrating needle, control means for varying the amplitude of the needle vibrations, a throat-plate, a loop-taker, a bobbin,

a bobbin-thread pull-off operatively engaging 9. In a buttonhole sewing machine, a reciprocating and laterally vibrating needle, control means for varying the amplitude of the needle vibrations, a throat-plate, a rotary hook, a bobbin-case journaled in said hook, means below the top of the bobbin-case for restraining the latter against rotation, a bobbin-thread pull-oil.

operative between the top of the bobbin-case and said throat-plate, an auxiliary bobbinthread pull-off operative in the space between the throat-plate and said first-mentioned pulloff, said auxiliary pull-01f being connected to the needle-vibrating control means.

10. In a sewing machine, in combination, a reciprocating needle, a rotary loop-taker making a plurality of rotations to one reciprocation of said needle, a bobbin, a loop-taker shaft, a bobbin-threadpull-off lever, a rotary crank and link device connected to operate said pull-off lever, and means for driving said crank at a speed less than that of the loop-taker shaft.

11. In a sewing machine, in combination, a reciprocating needle, a rotary loop-taker making a plurality of rotations to one reciprocation of said needle, a bobbin, a loop-taker shaft, a bobbin-thread pull-off lever, a rotary crank and link device connected to operate said pull-off lever, and means for driving said crank at a speed less than the speed of the loop-taker shaft, said pullofi being constructed and arranged to engage and pull off the bobbin-thread with a retarded motion as said crank is approaching one of its dead-center positions.

12. In a sewing machine, in combination, a reciprocating needle, a loop-taker, a bobbin, and

a bobbin-thread pull-off having means to engage and prevent expansion of the needle-thread loop on the side of the needle opposite to the side passed by the loop-taker in seizing the needlethread loop.

EDWARD B. ALLEN. MAURICE D. KNOX.