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Patent US 2499335 A: Thread-trimming and pull-off mechanism for sewing machines

   

Thread-trimming and pull-off mechanism for sewing machines

Patent Number: US 2499335 A
Filing date: Apr 25, 1946
Publication date: Feb 28, 1950

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Feb.28 1950 E. P. SPAINE 2,499,335 THREAD-TRIMMING AND PULL-OFF MECHANISM FOR SEWING MACHINES Filed April 25, 194.6 4 Sheets-Sheet 1 wmw m Feb. 28, 1950 E P. SPAIN E 2,499,335 -THREAD-TRIMMING AND PULL-OFF MECHANISM FOR SEWING MACHINES 4 Sheets-She et 2 Filed April 25, 1946 Feb. 28, 1950 E. P. SPAINE 2,499,335 THREAD-TRIMMING AND PULL-OFF MECHANISM FOR SEWING MACHINES 4 Sheets-Sheet 3 Filed April 25, 1946 Feb. 28, 1950 E. P. SPAINE 2,499,335 I THREAD-TRIMMING AND PULL-OFF MECHANISM FOR SEWING MACHINES Filed April 25, 1946 4 Sheets-Sheet 4 mumm Patented F eb. 28, 1950 u use STATES PATENT OFFICE This invention relates" to sewing machinesef the group-stitch type which are-constructed to sew'a short seam and then come to rest automati cally; and'it has'pa'rticular reference to devices for cutting the needle. thread and the looper thread.

The invention is herein illustrated as embodied in a buttonhole sewing machine of' the type in which the stitch-forming mechanism,v including the upper-thread-handling mechanism and the under-thread-handlingmechanism, is adapted to berotated at each end of the buttonhoie. The under-thread-handling mechanism is" carried by a turret beneath the work-holding means and compriseslooper devicesand loop-detainers arranged to concatenate the under thread with the needle thread and present the needleethrea'dloops properly to receive the needle during its penetrating stroke. When the .stitchaforming mechanism is brought'torest at the end of the stitching operation: the needle is raised and a loop of needle thread is held by one of the 'deta'iners of the under-thread mechanism, while the looper thread passes directly from. the work to the under-thread-handling mechanism;

It is the object oithe presentinvention to provide an improved thread-trimming and pull-oil mechanism which will operate first to cut the work-limb of the needle-thread-loop which .is held on the loop-detainer, then to engageandmull :o'fi a length of looper thread from its source of supply to insure the, proper initial stitchsforma-tion in the subsequent stitching operation, and finally to "cut the looper thread.

A further object oft the invention .is' to provide a thread-trimming and ,pull-yofidevice of. the above described character which issimple in construction and which is adaptedto be, secured on the turret of the under-thread-handling mechanism, whereby the rotation of the turret :causes the actuation of said thread-trimming :and .pulloff device.

Another object of the invention'is taprovide a unitary device of the class described designed so that a single oscillation of the knife-carrying arm will first sever the needle thread, thenpullofi ameasured length of .looper thread, and finallysever the looper thread. I

With the above and other objects in view, as

will hereinafter appear, theinvention comprises.

the devices, combinations and arrangements of parts hereinafter set forthand illustrated in the accompanying drawings of -a ,preferred embodiment or the invention, .from which the several features of the invention and theJadVantages-Eat- 55 v 2 tainedthereby will be readily understood by l'lhose skilled in the: art.

Inxthe accompanying drawings, v Fig. lis a-ri-ght side elevational view of abut ton-hole sewing machine embodying my, invention. .Fig.,2is a front'elevational view, partly in section, of the sewing; machine, showing the inoper- =ativeipositionof the thread-trimming andpulloff device during-the sewingoperation. Fig. .3 is-an-enlargedtopplan view of theun- -derthread-handling devices in their arrested po- :sition:at=the.=-end of the stitching operation, showmg the turret supporting said devices turned about its vertical axis to the point where the actuating :cr-ank for the thread-trimming and pull-off-device is j-ust engaging the abutmentlatch on the machine-frame.

Fig. is aview similar to Fig. 3 withthe tur- I ret advanced to the point where the knifeofthe thread-trimming and pull-off device has swung into engagement with the. needle thread preparatory to severing thesame, while the looper thread receivingnotch on the knife-carrying arm has engaged the lower thread and has begunits [pull-off: action.

Fig. 5 represents an enlarged verticalsectional view taken substantially along the line 5-i, Fig. 4. p

Fig. 6 is a view similar to Fig. 4, showin the needle thread severed and the knife-carrying arm Fig. 1.1 is a right side elevational.vie.w,.,partf.ly

insection, of the assembly .as illustratedin Eigjfi.

Fig. '12 represents a fragmentary disassembled perspective view of the stationaryfledger-blade and the movable knife-carrying arm, showing the needle thread severing knife and the 'looper thread knife-edge which cooperates with the ledger-blade in cuttingthelooper thread.

Fig. 13 is an enlarged perspective view of the supporting bracket, showing its details of design.

Referring more in detail to the drawings, the invention is shown as embodied in a well-known form of eyelet-end buttonhole sewing machine which has been converted into a tacking machine by being fitted so that the stitching mechanism thereof is operated only during the traverse of what normally would be one side of a conventional eyelet-end buttonhole. It will be understood that in a sewing machine of the type shown the stitch ing mechanism can be operated so that stitching is produced along the first side of. the buttonhole only or along the second or return side of the buttonhole only. In the machine illustrated the stitching is produced along the first side of the buttonhole. Generally speaking, the operating cycle of the machine shown includes the de-.

pressing of the usual starting lever causing the work clamping members to close on the work, after which the usual cutting levers advance to properly cut the work. Following the cutting of the work, the rapid feed is rendered effective to carry the work from cutting position into sewing position, after which the rapid feed is tripped and the step-by-step slow feed and the stitching mechanism are started to efiect the production of a straight zigzag seam along what would normally be the first side of a buttonhole. As the eye-end of the buttonhole is approached, the slow feed and the stitching mechanism are stopped,

latch on the machine-bed, whereby the device is actuated to sever the needle thread, pull-off a supply of looper thread, and sever the looper thread.

The sewing machine illustrated comprises a frame including a hollow box-like bed from one end of which rises a standard 2| of an overhanging bracket-arm 22 terminating in a. head '23. v The stitch-forming mechanism is of the wellknown type embodying an upper endwise reciprocatory and laterally vibratory needle 24 and complemental under thread mechanism constructed substantially in accordance with the disclosure of U. S. Patent No. 1,372,473, dated March 22,

1921. The under thread mechanism is mounted on a turret'2 5 which is turnable about a vertical axis and carrier threaded and nonthreaded implements or loopers 26 and 21 and a pair of loops As fully'explained in the loop detainer 28 is the one which takes the needlethread-loop N from the nonthreaded looper 21 and holds it spread for entry by the needle. same loop-detainer 28 is the one which retains the last needle-thread-loop at the termination of the stitching operation, as shown in Fig. 5. The turret also carries the usual work-supporting needle-throat-member 30 having an aperture 3| through which the needle 24 reciprocates.

The needle-actuating mechanism is also mounted to turn about a vertical axis coincident with the axis of the turret 25 and the usual turning movements are imparted to the'upper needle This and complemental under looper mechanisms by the connected upper and lower sector gears 32 and 33 (Fig. 1), respectively, which are actuated in unison by the regular connections with the feed-cam 34. This well-known mechanism is more completely shown, for example, in U. S. Patents No. 1 162,207, November 30, 1915; No. 15,324, reissued April 4, 1922; and No. 1,534,017, April 21, 1925. The mechanism operates to rotate the stitch-forming devices in one direction during the sewing around the eyelet-end of a buttonhole and to reversely rotate the stitch-forming devices between sewing periods to restore them to initial position. In the present machine the stitching mechanism is not operating during the travel around the eye or back the return side of the buttonhole, but despite this the stitch-forming devices traverse their usual turning movements.

The work W to be sewn is held through the entire cycle in a work-clamp, indicated as 35, which is of the traveling type. The work-clamp is first rapidly moved over the bed 23 to carry the work forwardly from initial or work-cutting position to stitching position, then more slowly moved in step-by-step fashion to place the stitches along the desired pattern, and then rapidly returned to initial position. The work-clamp 35 is carried by the usual cross-slide plate 36 (Fig. 2) which is adapted to slide laterally of the machine-bed 20 on a longitudinal slide-frame 31 shiftable in ways longitudinal of the machine-bed. The work-clamp 35 is given its longitudinal travel and lateral components of its feeding movement by suitable lever-connections with the main feedcam 34 mounted in the bed 20 of the machine and driven at a rapid rate prior and subsequent to the sewing period by a cross rotary shaft 38 which receives power from a rapid-feed shaft 39 (Fig. 1) through an automatically controlled clutch (not shown). The feed-cam 34 is more slowly driven during the sewing operation by a suitable gear-train 40 (Fig. 1) actuated from the main sewing shaft 4|, the period of operation of which is controlled by a stop-motion device 42, all in the manner more fully described in the above mentioned U. S. Patent No. Re. 15,324. Means is provided for automatically throwing the stop-motion device 42 into and out of operation to start and stop the stitch-forming mechanism, the control trips for the stop-motion device being fast on a removable and replaceable pattern wheel 43 carried on the cross rotary shaft 38.

As usual, in the machine shown, the stitchforming mechanism is so constructed that when the same comes to rest with the needle 24 raised as shown in Fig. 1 there will be a loop N of needle thread retained by the loop-detainer 28 (Figs.

3 and 5) of th under thread mechanism, the needle thread extending from the eye of the needle through the work W and forming the loop 44 of which one leg 45 is connected to the last stitch. The looper thread L passes directly from the work W down through the aperture 3| in the needle-throat member 3!] to the threadcarrying looper 26.

According to the present invention, I have provided means automatically actuated and operable between the needle-throat member 30 and the loop-detainer 28 for first severing the worklimb 45 of the retained needlethread-loop M, then engaging the looper thread and pulling off .a supply thereof for the subsequent stitching operation, and finally severing the looper thread at the termination of the pull-off action; To

, 5 that end I have provided a'u'n'itar'y thread-sever"- ing assembly comprising a supporting' bracket 45 (Fig. 13) apertured, as at 41, to receive the extended outboard end of the-regular loop-retainer supporting shaft 48 (Figs. 3 and 10) carried by the upstanding spaced posts 49 and 55 integral with the turret 25. The supporting bracket 46 is held upon the endof the loop-retainer shaft 48 by a cap-screw 5i and washer 52, andis prevented from turning on the shaft by two lugs 53 which engage the opposite sides of the turret-post d9. Extending laterally from the supporting bracket 45 are upper and lower limbs 54 and 55 bored, as at 55 and 5! (Fig.13), toprvide alined, vertically'spa'ced, bearingsin which is journaled an oscillatory knife-carrying shaft 58. Preferably integral with the'upper end :of the shaft 58 is a horizontal arm 59 having fastened on the'upper surface of its free end, as by two screws (it), a. hardened knife-blade 61. The knife-blade (ii is formed at its outer end with a sharpened needle-thread-cutting edge 52 disposed so that the initial turning of the oscillatory shaft swings said cutting edge into thread-severing contact with the tensioned Worklimb 45 of the needle-thread-loop 44 retained on the loop-detainer 28. To insure that only the work-limb of the-needle-thread-loop is cut, the front portion of the cutting edge 52 is relieved and dulled slightly, as indicated at 65, so that as the knife swings to cut the needle thread, the

dulled portion will first engage and deflect the fastened by two screws 64 a hardened looperthread-severing knife-blade 65 formed adjacent its free end with a looper-thread-receiving notch 66 disposed vertically beneatha similar notch 51 formed in theneedle thread knife-blade The two vertically alined notches 65 and B1 are disposed to engage the looper thread L (Figs. 4 and 5) as the knife-carrying arm'59 swings between the needle-throat member 30 and the loopdetainer 28.. The entire looper-thread pull-off action occurs during the swinging of the knifecarrying arm 59 from the position of initial engagement of the looper thread by the spaced knife-blades 5i and 65 to the position shown in Fig. 6; The pull-off action on the looper thread is terminated with the cutting of the looper thread. r

To effect the cutting of the looper thread, the

knife-blade 55 is provided in its under face with a knife-edge 55 (Fig. 12) adapted to swing into shearing relation with the sharpened edge 69 of a stationary ledger-blade 15. The ledger-blade is detachably mounted on the upper lateral extension 'll of a supporting member 72. The body of the member '72 is bored longitudinally (Fig. 11) to provide an extension of'the bearing 'for the oscillatory knife-carrying'shaft 5B and,

at its lower end, the member 172 is formed with a lower lateral extension l3 clamped upon the top of the'supporting bracket lt'by'a clampscrew 14 extending through a slot in the extgi aees 6 '15 and the clamp-screw 74 the ledger-blade sup"- porting member 12 can be adjusted circularly for a limited extent about the axis of the knifecarrying shaft 58. Since the adjustment of the member 72 is about the axis of the shaft 58, the thread-shearing relationship between the knife-edge 58 and the sharpened ledger-blade edge 69 is not disturbed during adjustment of the latter. It will be appreciated that the adjustment of the ledger-blade in about the shaft 58 provides means for regulating the length of the looper thread pulled from its source of supply by the swinging action of the knife-carrying arms 59 and 69. From the above description it will be understood that the knife-blades 5i and G5 and the ledger-blade 10 each can be readily removed for resharpening or replacement.

' Oscillation of the knife-carrying shaft 58 to cause cutting of the two sewing threads and pulling off of the looper thread iseifected in a single continuous motion, as hereinbefore mentioned, by theturning of the turret 25. In Fig. 9 it will be seen that the knife-carrying shaft 58 has a sector-gear i6 secured on its lower end. This sector-gear i6 meshes with a gear I! preferablypress-fitted and keyed, as by pin 78 (Fig. 9), upon the reduced hub E9 of a. crank 85 journaled on a pivot-stud 8| depending from the extended lower limb 55 of the supporting bracket 45 Carried by the free end of the crank 80 is a roller 82 which is normally disposed to engage an abutment-latch 83'carried on a stationary extension-plate Mfastened by'screws 85 (Fig. 3) passing through a guard-plate 20' secured to the machine-bed 20. During the normal sewing operation the turret 25 is positioned'as shown in Figs. 1 and 2. In this position of the turret the knife-carrying arm 59 is yieldingly biased by a coil-spring 85, acting between the supporting bracket 46 and a pin 8'! carried by the sectorgear'iB, into a retracted or set position determined by the engagement of the pin 81 with one of the lugs 53 on the supporting bracket 45 (Fig. 11). In the set position the knife-blade BI is disposed forwardly of and slightly to the right of the needle-throat-member 30 in the manner shown in Fig. 3, so that the initial swinging movement of the knife-carrying arm 59 will cause the knife-blades to pass between the needle-throat member 3i) and'the loop-detainer As the turret continues in its turning movement 'the crank-arm 85, through the gears Ti and 76,

eifects an oscillation of theknife-carrying shaft 53 causing theknife-carrying arm 59 to swing in'asingle continuousmotion from its retracted position (Fig. 3), through the needle thread severing position (Fig. 4) and the looper thread pull-off position (Fig. 6), to its looper thread severing position (Fig. '7). The actuating connections of the thread-cutting and pull-off device are so proportioned that the entire effective oscillation of the knife-carrying arm takes place during substantially 35 degrees rotation of the turret 25.. After. the parts have moved to the positionshown in Fig. 7, continued rotation of tension 13. Through the medium. of the slottqsthe turret carries the .roller 82 beyond the abut- 7 merit-latch 83. When this occurs the coil-spring 86 biases the knife-carrying arm 59 to its retracted or set position.

In the regular cycle of the machine illustrated, the turret isreversely rotated (counterclockwise) at the end of the operation to restore it to its initial position. In order to permit the crankarm 80 to swing past the abutment-latch 83 when the turret is reversely rotated, the abutmentlatch is pivotally mounted at 88, whereby the latch swings in a clockwise direction against the action of a spring 89 under pressure exerted by the roller 82 on the abutment-latch 83. When the roller 82 passes beyond the abutment-latch 83 the spring 89 snaps the same back into its normal operating position determined by a stoppin 90. 1

While the improved. device disclosed is adapted to be actuated during the forward turning of the turret 25, it is a simple matter to modify the device if it is desired that the device operate during the reverse turning of the turret, which action would be necessary if the machine were For the practical operation of a sewing machine equipped with thread-trimming devices adapted to sever the needle thread or looper thread, or both, it is essential that the threadend extending from the needle or looper be sufficiently long to prevent the unthreading of said needle or looper during the formation of the initial stitch of the subsequent stitching cycle. It will be understood from the above that a sufficient and proper length of looper thread is accounted for by the pull-01f action exerted on the looper thread by the knife-carrying arm 59 as it swings from needle-thread-severing position to looper-thread-severing position. To insure the formation of an adequate length of needle thread, the machine illustrated also is fitted with a common form of needle thread nipping and pull-01f mechanism disclosed, for instance, in the U. S. patent of E. P. Spaine et al., No. 2,210,638, August 6, 1940. This needle thread nipping and pull-oil mechanism, which is actuated by the regular work-clamp closing lever 94 (Fig. 1), comprises a vertically disposed rod 92 having at its upper end a lateral extension 93 overlying the needle thread L and underlying the usual nipper-release lever 94. When the clamp-closing lever 9! is depressed to close the work-clamp 35, the lateral extension 93 of the rod 92 is drawn downwardly to first lower the nipper-release lever 94, permitting a coil-spring 95 to nip the needle thread, and then engage and pull a measured length of needle thread from the supply. During the recovery motion of the clamp-closing lever 91, the pulled off needle thread is slackened and the lever 94 is operated to release the needle thread and permit it to run freely to the needle. The measured length of needle thread thus provided is adequate to supply the demands of the needle-bar during its initial reciprocation, without causing the unthreading of the needle 24.

In machines of the type disclosed, it is common practice to employ one needle thread and two looper threads; the resulting seam of this combination being a three-thread seam. When the machine is so fitted, the cooperation of the threaded needle and the two threaded loopers is such that no loop of needle thread is detained by the usual loop-retainers. Consequently, when the machine comes to rest the lead of the needle thread from the last stitch in the work does not extend within the range of movement of the knife-carrying arm 59. Therefore, when it is desired to apply the present thread pull-off and trimming device to a three-thread machine, the

needle thread knife-blade 6| can be removed, leaving only the looper thread knife-blade 65 for cutting the looper thread at the termination of the looper thread pull-off stroke. Since there are two loopers, each with its own thread, a second pull-off and trimming mechanism of the same design as my present one can be used at a position directly opposite on the turret 25 to the one illustrated, thereby to sever the second looper thread. The needle thread may be cut by hand or by any suitable mechanical means.

From the above description, it will be seen that I have invented an improved thread-trimming and pull-off mechanism which is simple in construction and effective in operation to sever the needle and looper threads and to pull oiT an accurate length of looper thread from its source of supply; all of the operations being carried out in proper sequence by a single continuous oscillation of the knife carrying arm. Also, it will be evident that the thread-trimming device can be utilized to operate on a single thread, whether it be the needle thread or the looper thread.

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

1. A two-thread sewing machine having, in combination, stitch-forming mechanism including a thread-carrying needle and a complemental thread-carrying under mechanism arranged so that when the machine comes to rest the needlethread and the under thread extend from the last stitch in the work to said under mechanism, and a thread-severing device including two elements movable relatively to each other into and out of thread-severing relationship, a movable arm carrying one of said elements, and operating connections constructed and arranged for imparting a single actuating stroke to said arm so that the element carried thereby severs one of said sewing threads, engages and pulls off a length of the second thread and finally severs said second thread. 1

2. A two-thread sewing machine having, in combination, stitch-forming mechanism including a thread-carrying needle and a complemental thread-carrying under mechanism arranged so that when the machine comes to rest the needlethread and the under thread extend from the vlast stitch in the work to said under mechanism,

and a thread-severing device including knife means, an oscillatory arm carrying said knifemeans, a stationary ledger-blade, and operating connections for imparting a single actuating stroke to said oscillatory arm so that said knife- 1 means first severs one of said sewing threads,

, pulls off a measured length of the second sewing 9. thread-carrying under mechanism arranged so that when the machinecomes to rest the needle thread and the under thread extend fromthe last stitch in the work to said under mechanism, and a thread-severing device including an oscillatory arm, a plurality of knife-blades on said arm constructed and arranged to moveinto contact with said threads, a ledger-blade disposed for thread-shearing cooperat on with one of said knife-blades, and means for imparting a single actuating stroke to said oscillatory arm for causing one of said knife-blades to sever one of said threads and the other of said knife-blades to move into shearing relation withv said ledgerblade to cut the other of said threads,

4. A two-thread sewing machine having, in combination, stitch-forming mechanism including an upper thread-carrying needle and cmplementary under thread-carrying mechan sm,

and a thread-severing device including an oscillatory arm, knife-means carried by said arm, a ledger-blade, means for actuating said arm to cause said knife-means to move into threadshearing cooperation with said ledger-blade, and means supporting said ledger-blade, said lastnamed means having capacity for adjusting said ledger-blade in a curved path about the axis of oscillation of said arm. I

5. A sewing machine having in combination, an apertured needle-throat member, stitch-forming mechanism including a reciprocatory threadcarrying needle and complemental thread-carrying loop-taking means arranged so that when the machine comes to rest a loop of needle thread is retained on the loop-taking means and the loop-taker thread extends from the latter up through the aperture in said needle-throat member to the work, and a thread-severing device including an oscillatory arm, a pair of knife-blades carried by said arm, a ledger-blade, and means for actuating said arm to cause one of said knifeblades to enga e and cut one limb of the retained needle-thread-loop and to cause said arm to engage and pull off a length of the loop-taker thread and finally to move the other of said knife-blades into shear ng relation with said ledger-blade to out said loop-taker thread.

6. A sewing mach ne having, in combination, stitch-forming mechanism comprising upper thread handling mechanism and comnlemental under mechanism arranged so that when the machine comes to rest a loop of upper thread is retained by the comolemental under mechanism, and an unner thread-sever ng device including an o cillatory knife formed w th a sharpened cutting ed e, and means for oscillatin said knife to cau e the latter to engage and deflect one limb of said retained thread-loop and subsequent v to sever the other limb of said retained thread-loop.

7. A sew ng machine having, in combination, st t h-forming mechanism comprising upper thread handling mechanism and complemental under mechanism arranged so that when the mechanism comes to rest a loop of upper thread is retained by the complemental under mechanism, and a needle-thread severing device including a movable cutter having a sharpened cutting portion and a dulled thread-engaging portion, and means for moving said cutter to cause the dulled portion thereof first to engage and deflect one limb of said retained needle thread-loop so that the sharpened portion thereof subsequently can engage and sever the other limb of said retained needle thread-loop.

8. A sewing. machine having, in combination, a

needle-throat member formed with an. aperture, stitch-formingmechanism comprising a reciproe. cator thread-carrying needle positioned to operthereof= first to-en-gage and deflect one limb of' said retained needle-thread-loop so that the. sharpened portion thereof subsequently canv en; gage and sever the other limb of said retainedneedle-thread-loop.

9. A two-thread sewing ing a thread-carrying needle and complemental thread-carrying mechanism, rotary supporting means for the stitch-forming mechanism including a turret, a thread-severing device supported onsaid turret and means rendered effective by the turning of said turret for imparting a single continuous actuating stroke' to said thread-severing. device for first severing one of saidsewing threads, pulling off a measured length or the second sewing thread and finally severing said second sewing thread,

10,:A sewing machine having, incombination stitch-forming mechanism including a reciprocatory needle and a complemental thread-carrying loop-taker, and a thread-severing device including an oscillatory arm, knife-means carried by said arm, a ledger-blade, means for actuating said arm to cause it to engage and pull off a length of the loop-taker thread and then to carry said knife-means into thread-shearing relation with said ledger-blade to sever the loop-taker thread and thereby terminate the thread pull-01f action of said oscillatory arm, and means supporting said ledger-blade and having capacity permitting adjustment of said ledger-blade in a curved path about the axis of oscillation of said arm.

11. A thread-severing device for sewing machines comprising a supporting bracket, a shaft journaled-in said supporting bracket. knife-means carried by said shaft, a ledger-blade complemental to said knife-means in severing thread, a ledger-blade supporting member mounted on said supporting bracket for turning movement about the axis of said shaft to permit adjustment of said ledger-blade, and shaft actuating means adapted for imparting movements to said shaft to swing said knife means into thread-shearing relation with said ledger-blade.

12. A thread-severing device for sewing machines comprising a supporting bracket, a shaft journaled in said supporting bracket, knifesaid shaft, and means for actuating said shaft to move said knife-means into thread-shearing relation with said ledger-blade.

13. A unitaryithread-severing device for sew-' m m in haft journaled'in said supporting bracket, knife mprising a supporting bracket, a

machine having, in.' combination, a stitch-forming mechanism includ- 11 means carried by said shaft, a l edg erbladesustained by said supporting bracket, and means in:-

cluding a crank for imparting a turning move- 15. A thread-severing device for sewing machines' comprising a supporting bracket, a shaft journaled in said supporting bracket, knife-means carried by said shaft, a ledger-blade, a member supporting said ledger-blade and fastened on said supporting bracket for turning adjustment about the axis of said shaft, spring-means for biasing said shaft in a direction to space said knife-means from said ledger-blade, and means including an element fast on said shaft for imparting 'a turning movement to said shaft in opposition to said spring-means for swinging said knife-means into M thread-shearing relation with said ledger-blade.

16. A thread-severing device adapted for attachment on a sewing machine having stitchforming devices carried 7 on rotary supporting means including a turret, comprising, a supporting bracket, a shaft journaled in said supporting bracket, knife-means carried on said shaft,

. 12 spring-means effective for biasing said knifemeans into a retracted position, and actuating means including an element fast on said shaft and rendered effective by the turning of said 5 turret for imparting a thread-severing stroke to said knife-means.

17. A sewing machine having, in combination,

stitch-forming mechanism including a reciprocatory thread-carrying needle and complemental 10' thread-carrying loop-taking means arranged so that when the machine comes to rest the needlethread and the loop-taker thread extend from the last stitch in the work to the loop-taking means, and a thread-severing device including a g first movable thread-severing member operable in a plane intersected by the two threads when the machine is at rest, a second member arranged in thread-shearing relation with said first member, and means for actuating said first movable ifthread-severing member to cause said member to effect pulling off a length of one of said threads from its supply and the severing of both of said threads.

EDWARD P. SPAINE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 30 Number Name Date 1,291,335 Wood Jan. 14, 1919 1,839,305 Fisher Jan. 5, 1932 Gunther Nov. 30, 1943

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