US1966432A

US1966432A - Stitch forming mechanism for buttonhole sewing machines

Info

Publication number: US1966432A
Application number: US609083A
Authority: US
Inventors: Edward B Allen; Maurice D Knox
Original assignee: Singer Co
Current assignee: Singer Co
Priority date: 1932-05-04
Filing date: 1932-05-04
Publication date: 1934-07-17
Anticipated expiration: 1951-07-17

Description

July 17, 1934. E. B. ALLEN El AL STITCH FORMING MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed May 4, 1,932 9 Sheets-Sheet 1 Edward 5. 411%!- and flfaunbefl Knox July'17, 1934. E; a. ALLEN ET AL ST ITCH FORMING MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed May 4, 1932 9 Sheets-Sheet 2 awwmtou Edward 6. Allan and Maurice D. [(nar WMeoo July 17, 1934. B, ALLEN AL 1,966,432

STITCH FORMING MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed May 4, 1932 9 Sheeis-Sheet 5 gwhto'vo Edward 6. Allan and Maurice fljfimr July 17, 1934; 1,966,432

STITCH FORMING MECHANISM FOR BUTTONHOLE SEWING MACHINES E. B. ALLEN El AL Filed May 4, 1932 9 Sheets-Sheet 4 Zdward 5, Allen and Maurice [1. 161m:

July 17, 1934. E. a. ALLEN ET AL 1,966,432

STITCH FORMING MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed May 4, 1932 9 Sheets-Sheet 5 Edward 151/1110 a Maurwc D Knox W July 17, 1934. E. B. ALLEN ET AL STITCH FORMING IECHANISM FOR BUTTONHOLE SEWING MACHINES Filed May 4, 1932 9 Sheets-Sheet 6 gwventoca Edward fiAllerz and Maurice fl. [(2:01

WWW/om W y 1934- E. B. ALLEN ET AL STITCH FORMING MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed May 4, 1932 9 Sheets-Sheet 7 Z A. 3 4% MM July 17, 1934. E. B. ALLEN ET AL I STITCH FORMING MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed May 4, 1952 I 9 Sheets-Sheet 8 i 7 .ElhliillLll! 65% I31 1Z2 Ill 95 111 Edward @AJZGIZ an Maurice 2 1610.2:

W i fi LGM $11 July 17, 1934. E. B. ALLEN Er AL 1,965,432

STITCH FORMING MECHANISM FOR BUTTONHOLE SEWING MACHINES Filed May 4, 1932 9 Sheets-Sheet 9 gwwn io cb Eda/aid 5.14110 and jl/wurz'ce D- Knox Patented July 17, 1934 UNITED STATES PATENT OFFICE STITCH FORMING MECHANISM FOR BUT- TONHOLE SEWING MACHINES New Jersey Application May 4, 1932-, Serial No. 609,083

11 Claims.

machines for sewing buttonhole seam at This invention relates to a pyramid-purl lock-stitch high speed.

To fully appreciate the novel features of the present improvement, a full knowledge of the characteristics of the pyramid-purl stitch is necessary and, with this object in view, the following explanation is given:

The formation of the pyramid-purl seam is accomplished by the cooperation of an upper eyepointed 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 bobbin. The needle-thread take-up is required not only to draw up the needle-thread loops after they have been interlocked with the bobbinthread, but also to draw such loops entirely through the work, pulling loops of bobbin-thread through to the upper side of the work, so that in the finished seam the needle-thread will lie in substantially a straight center line between the rows of zigzag needle-punctures, while loops of 2 bobbin-thread emerge from the needle-punctures at the upper side of the work 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 an inch 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 the bobbin-thread must necessarily be light while the tension on the needle-thread must be very strong.

These requirements make it very difiicult to properly and uniformly sew the pyramid-purl lock-stitch seam at high speeds, as the relation of the heavy needle-threadtension to the very light bobbin-thread tension is an unnatural one and the threads must be carefully handled in the formation of the stitch to avoid undue strain or interference with the free thread-delivery.

The invention has for an object to provide stitch-forming mechanism capable of sewing a commercially acceptable pyramid-purl buttonhole seam at high speeds of the order of 3000 stitches per minute.

With the above and other more specific 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 attained thereby will be readily understood by those skilled in the art.

In the accompanying drawings, Fig. 1 is a side elevation of a buttonhole sewing machine embodying the invention. Fig. 2 is a reverse side 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 bracketarm of the machine. Fig. 6 is a front end elevation. Fig. '7 is a view of the work-clamp opening mechanism shown in Fig. 6. Fig. 8 is a front face view of the rotary hook mechanism, the hook beginning its idle rotation. Fig. 9 is a section on the line 99, Fig. 8, with the rotary hook and bobbin-case in elevation.

Fig. 10 is a view similar to Fig. 8 showing the initial engagement of the bobbin-thread pulloff device with the bobbin-thread; the hook having executed approximately the first half'of its idle rotation. Fig. 11 is a view showing the pull-off device at the end of its pull-off stroke; the hook-beak being at the point of seizure of a needle-loop. Fig. 12 is a vertical central sec- 0 tion on the line 12--l2, Fig. 11. Fig. 13 is a view similar to Fig. 11 showing the needle-loop being drawn out by the hook and beginning its passage about the bobbin-case. Fig. 14 is a central vertical section similar to Fig. 12 showing the needle-loop fully expanded in its passage about the bobbin-case. Fig. 15 is a face view of the hook showing the needle-loop being drawn oil of the beak of the hook after having been cast about the bobbin-case. Fig. 16 is a 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. 17 is a view similar to Fig. 12 showing the efiect of the auxiliary bobbin-thread pull-off device. Fig. 18 is a top-plan view of the bobbin-thread pull-off devices in the positions shown in Fig. 17. Fig. 19 is a horizontal section through the hook and bobbin-case bodies.

Fig. 20 is a diametrical section through the bobbin-case. Fig.21 is a front view of the bobbin-thread pull-off device and the means for actuating it. Fig. 22 is a section on the line 22--22, Fig. 4. Fig. 23 is a section on the line 23-23, Fig. 4. Fig. 24 is a plan view of the gearing under the sewing machine bracket-arm which controls the amplitude of vibration of the needlebar vibrating mechanism and drives the feedwheel. Figs. 25 and 26 are sections on the lines 25-25 and 26--26, respectively, Fig. 24. Fig. 27

is a view showing the action of the check-spring blocking mechanism associated with the tension release mechanism. Fig. 28 is a top-plan view of .the tension device and check-spring blocking means. Fig. 29 is a top-plan view of a purl-stitch seam such as is commonly used in sewing buttonholes.

Fig. 30 is a bottom plan view of the seam. Fig. 31 is a cross-sectional view of the seam. Fig. 32 is a section on the line 3232, Fig. 1. Fig. 33 is a disassembled perspective view of the rotary hook. Fig. 34 is a disassembled perspective view of the bobbin-case. Fig. 35 is a top-plan view of the upper clamp-foot. Fig. 36 is a bottom plan view of the same. Fig. 37 is a section on the line 37-37, Fig. 35, and Fig. 38 is an enlarged section through the hook-body and bobbin-case.

Referring first to Figs. 29,30, and 31, the purl-stitch 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 b formed into loops 0 which are drawn through the material and to the center line between the 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 tothe needle-bar 9 journaled in the usual needle-bar gate 10 which is fulcrumed at 11 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 on the mainshaft 5 which drives a gear 15 of double the number of teeth carrying two diametrically opposed 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 30' engages a slot in the slide-block 25. The amplitudeof 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 24, to the forwardly extending arm 31 of a lever fulcrumed at 32 to the 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. The gear 34 has fixed to its upper face cam-blocks a rearward extension or tail 46 which 38, Figs. 24 and 26, 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 January 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 feed-cam-grooves 44 and 45, respectively, in the feed-wheel 36. The clamp-lever 40 has 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 rock-shaft 50 at the side of the gooseneck.

The upper clamp-foot 39 comprises an aperturcd rectangular frame including the outer parallel side bars 39, Figs. 35, 36 and 37, having roughened lower edges adapted to grip the work upon the .upper surface of the longitudinal slideframe 42, as shown in Fig. 10. The side bars 39 have outward extensions or ledges 39 upon which are screwed the spring-shanks 39 of the inner parallel side bars 39 which reduce the width of the aperture in the foot 39 and press the work upon the throat-plate 53 closely adjacent the rows of depth-stitch punctures of the needle 51; thus effectively holding the work and preventing distortion thereof during the sewing. The in ner parallel bars 39 are adjustable toward and away from the outer bars 39 to enable them to be set for buttonholes of different widths.

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 Patent No. 1,878,091 j dated September 20, 1932. It comprises the usual tight and loose belt-

pulleys

56 and 57, respectivetion is substantially thesame as that disclosed in the Allen Patent No. 1,659,937, of February 21, 1928. When the stop-motion lever 62 is tilted to disengage the plunger 61 from the stop-cam 60, the point 71, Fig l, 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 tilt ed 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 65 to carry the belt to the loose-pulley 57. The machine now coasts to final stopping position determined by engagement of th tripping point 74, Fig. 4, on the feed-wheel 36 with the latch-lever '15 which is disengaged from the notch 76 in the rod 7'1 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 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 rock-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. 14, for the flange 87 of the bobbin-case 88. The crossed runs of the belt 82 are held apart by the thin sheet-metal separator plate 82', Figs. 1 and 32, secured to the bed 1.

The bobbin-case flange 8'! is held in the bearing groove 86 of the hook-body by means of the removable gib screwed to the face of the hookbody. The bobbin-case 88 is formed in front of the bearing flange 87 with a guard-flange 89 which is somewhat larger in diameter than the bearing flange 87 and overlaps but is spaced slightly from the gib 90. The guard flange 89 prevents contact of the front limb of the needleloop with the oiled bearing rib 87 during the loopcasting operation. No part of the hook-body projects beyond the plane of the exposed face of the gib 90. Back of the beak 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 front and rear loop-spreading

walls

92, 93 of the bobbin-case 88. These

walls

92 and 93 spread the limbs of the needle-loop substantially equal distances forwardly and rearwardly of the plane of rotation of the hook-beak and thus minimize the strains on the thread and conduce to the free and easy casting of the needle-loop, without subjecting the latter to sudden or harsh bends while under the strain of being drawn out. The inner edge of the gib 90, Fig. 14, prevents contact of the bobbin-thread with the oiled surfaces of the bobbin-case bearing groove 86.

The bobbin-case 88 is formed with a circular cavity for the bobbin 94 which is journaled on the tubular arbor 95 in the center of the bobbincase and held in place by the latch-lever 96. The latch-lever 96 is fulcrumed on the pin 97, Fig. 20, carried by the arbor 95 and has a tail 98 which engages the inclined face 99 of a spring-pressed plunger 100 mounted in the arbor 95. Obviously, the lever 96 may be swung outwardly from the position shown in full linesin Fig. 20 to the dotted line position to permit removal and replacement of the bobbin. The latch-lever 96 has fixed to its under face at its outer end a leaf-spring 101 which extends toward the 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 sufficient friction close to the arbor 95 to prevent overrunning of the bobbin and the spilling of bobbin-thread thereby. The circular wall 103 of the bobbin-case is formed with 8. bob- I bin-thread slot 104, Fig. 34, the open mouth 10.5 of which is closed by the free end of the closed latch-lever 96 to prevent escape of the bobbin-thread from the slot 104.

The bobbin-case 88 is formed at its upper side with a needle-clearance channel affording an inner needle-guide-wall 106, Fig. 17, and an outer needle-guide-wall 107. The inner wall 106 prevents deflection of the needle 51 into the path of the hook-beak 85. The outer wall 107 guides the needle against deflection away from the path of the hook-beak and assists in preventing the needle-loop from bowing outwardly on the wrong side of the needle. There is applied to the bobbincase 88 a leaf-spring 108 having a notched tongue 109, Fig. 12, through which the bobbin-thread is delivered after it has passed between the free end of the spring 108 and the underlying wall 109', Fig. 34, of the bobbin-case. The spring 108 applies a light tension to the bobbin-thread the amount of which tension may be varied by loosening or tightening the tension-adjusting screw 110.

The front inclined or conical wall 92 of the bobbin-case is formed with notches or pockets 111 for reception of 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 throat plate 53. The

arms

112, 113 are carried by

rockshafts

114, 115 which are journaled in sleeves 116, carried by the V-bracket 117 fixed to the tubular stud 118 projecting rigidly forwardly from the bed-lug 119. The sleeves 116 rest in semicircular grooves 120, Fig. 22, in the opposite sidewalls of the bed-lug 119 which steadies the sleeves and their supporting bracket 11'? against turning on the supporting stud 118.

Secured to the rear end of the rock-shaft 114 is a cam-follower fork 121, Fig. 23, the upper arm 122 of which engages the opener-cam 123 on the cam-shaft 124 which is journaled in the bed-lug 119 and has fixed to it a gear 125 meshing with a driving pinion 126 on the hook-shaft 83. The gear ratio is such runs at the same speed as the main-shaft 5, or half as fast as the hook-shaft 83. The under arm 12''! of the fork 121 engages the cam 128 the function of which is to 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 rockng impulse to the shaft 114 to open a passage between the arm 112 and its pocket 111 at the time when the needle-loop is ready to pass between the arm 112 and the bobbin-case, as shown in Fig. 15.

The shaft 115, Fig. 22, carries a cam-follower fork 129 the upper arm 130 of which engages the pointed opener-cam 131 on the shaft 124 and is retained in engagement with such cam by the engagement of the adjacent retainer cam 132 with the under arm 133 of the fork 129. The cam 131 opens a gap between the arm 113 and its pocket 111 in the bobbin-case at the time shown in Fig. 13 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 in a mechanism intended to be operated at highspeed. The arm 112 is formed at its front side with a guard-flange 134 to guard the hooked end of 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. 15.

that the shaft 124 y Journaled to move freely upon and relative to the hook-shaft 83, between the hook-body and the gear 126, is the pull-off lever 135 one arm of which is bent to overhang the hook and bobbincase bodies and formed with a pull-oil blade 136 having a thread-cam edge 137 and a needle-loop engaging edge 138, Fig. 12. The pull-011 lever 135 is connected by a link 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 hook 85. The crank 140 is about in the position shown in full lines in Fig. 21 and as it moves to its dead-center position shown in dotted lines in Fig. 21, the pull-off blade is moved with a retarded motion to its extreme or dotted line position, Fig. 21, and hence pulls off the bobbin-thread with a retarded motion, thus avoiding a jerking of the bobbin-thread and minimizing any tendency toward over-running or spilling of thread by the bobbin. At the time of maximum pull-off as shown in Fig. 12, 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 011 (about 1 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 suificient to properly form the barring stitches at the ends of the buttonhole. Means are therefore provided to pull on an increased supply of bobbin-thread for the barring stitches. To this end there is fulcrumed on the screw 141, Figs. 4, 6, 17 and 18, 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 blade 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 of the lever 31 which controls the amplitude of vibration of the needle 51. The auxiliary pull-off blade 143 is formed with a thread-engaging shoulder 149, Fig. 18, 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. 18. When the sewing is proceeding along the sides of the buttonhole the auxiliary pull-off blade occupies its dotted line position, Figs. 17 and 18, and is inoperative.

The needle-thread t runs from the supply through the spaced thread-

guides

150, 151 in a 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 and down to the needle 51. 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 rockshaft 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 needle-thread 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 needlemovement of the arm 168, Fig. 7, 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-cutter-tripping mechanism in the Allen application Serial No. 551,114, filed July 16, 1931. The lever 169 is fulcrumed at 170, Fig. 7, on the clamp-opening lever 49 and has two

arms

171, 172 engaging under and over the lever 49 with a certain amount of lost motion permitting an initial down-movement of the lever 169 sufilcient to cause the inner end of the lever 169 to elevate the thread-cutter latchlever 168 and trip the needle-thread cutter into operation, before the lever 169 effects a downmovement of the lever 49 to open the work-clamp.

It will be evident that when the machine is sewing, every time the take-up moves to its highest point the strain on the needle-thread overcomes the weak tension of the check-spring 157 and pulls it over to the strained position shown in full lines in Fig. 27. At the end of a sewing operation the tension-

devices

153 and 155 are automatically opened and the check-spring has a tendency to recover its initial or dotted line position, Fig. 27, and steal needle-thread tension-devices. If this action were permitted the supply, when the machine is at rest, an

amount of needle-thread sufficient 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-oi! lever is rocked to its dotted line position, Fig. 1, and returned to its full line position, thereby pulling oil from the supply spool a length of needle-thread suflicient to sew the next buttonhole.

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

1. In a sewing machine, a rotary hook, a stationary bobbin-case, openable devices adapted to engage said bobbin-case at spaced points, a constant speed drive-shaft, and separate and independently timed actuating connections between each of said devices, respectively, and said driveshaft.

2. A rotary hook, a bobbin-case iournaled in said hook, a plurality of openable devices engaging the bobbin-case to restrain the latter against rotation with said hook, a drive-shaft, a plurality of separate and distinct actuating devices on said shaft, and a train of connections between each of said actuating devices and a respective one of said openable devices.

3. In a sewing machine, a rotary hook, a stationary bobbin-case, devices adapted to engage said bobbin-case at spaced points, a constant speed drive-shaft, and separate and independently timed actuating connections between each of said devices, respectively, and said drive-shaft, said actuating connections including cams timed to disengage said devices from the bobbin-case one at a time for passage of a needle-loop while the other remains in engagement with the bobbin-case.

4. In a sewing machine, a rotary hook, a stationary bobbin-case, bobbin-case rotation-restraining devices adapted to engage said bobbincase at spaced points, a constant speed driveshait, cams on said drive-shaft, and operative connections between each of said cams and a respective one or said devices to disengage it momentarily from the bobbin-case.

5. In a sewing machine, in combination, a reciprocating needle, a rotary hook, a hookshatt, a bobbin-case, and bobbin-case rotationrestraining means comprising a plurality of bobbin-case engaging arms, a plurality of rock-shafts each carrying a respective one of said arms, an opener-shaft, an actuating device on said openershait for each of said rock-shafts, respectively,

said actuating devices being each independently plurality of rotations to said hook-shaft for each rotation of said opener-shalt.

6. In a sewing machine, a needle, a needlereciprocating shaft, a rotary hook, a hook-shaft making a plurality of rotations for each rotation of the needle-reciprocating shaft, a bobbin-case, a plurality of openable devices engaging said bobbin-case to restrain the latter against rotation with said hook, an opener-shaft geared to said hook-shaft to run at the same speed as the needle-reciprocating shaft, and a plurality of actuating devices on said opener-shaft each connected to actuate and control the opening and closing motion of a respective one of said rotation-restraining devices.

7. In a sewing machine, a needle, a rotary hook, a bobbin-case, a pair of oscillatory arms having hook-shaped extremities engaging said bobbin-case, means for oscillating said arms to disengage them one at a time from the bobbincase to form a free passage for a needle-loop in a loop-casting rotation of said rotary hook, and a loop-guard for the end of one of said arms.

'8. In a sewing machine, a needle, a rotary hook, a bobbin-case, a pair oi. oscillatory arms having hook-shaped extremities engaging said bobbin case, means for oscillating said arms to disengage them one at a time from the bobbin-case to form a free passage for a needle-loop in a loop-casting rotation of said rotary hook, and a needle-loop guard-flange carried by the arm last passed by a cast needle-loop.

9. A sewing machine having a reciprocating needle, a rotary hook, a stationary bobbin-case having a bearing rib journaled in said rotary hook, a gib carried by said hook and engaging said bearing rib, and a guard-flange on said 110 bobbin-case spaced from said bearing rib and overlapping said gib.

10. In a sewing machine, in combination, a reciprocating needle, a circularly moving, hook, a stationary bobbin-case journaled in said hook, and rotation-restraining mealrk engaging said bobbin-case below the top thereof, said bobbincase being formed at its top with a needle-guiding channel having a wall blocking deflection of the needle into the path of the hook.

11. In a sewing machine, a reciprocating needle, a rotary hook, a stationary bobbin-case having a circular bobbin-cavity, a bobbin in said cavity, said bobbin-case having a central arbor on which said bobbin is journaled, and a bobbinthread delivery 'guide above said bobbin-cavity, the wall of said bobbin-cavity having a bobbinthread-receiving slot, and a bobbin-retaining latch pivoted on said arbor and adapted to close the outer end oi said bobbin-thread-receiving 130 slot.

EDWARD B. AIL-EN. MAURICE D. KNOX.

' its