Thread trimming mechanism for sewing machines
Patent Number: US 2550611 A
Filing date: Oct 22, 1948
Publication date: Apr 24, 1951
AprilZf}, 1951 E. P. SPAINE 2,550,611
THREAD T RIMMING MECHANISM FOR SEWING MACHINES Filed Oct. 22, 1948' .4 Sheets-Sheet 1 IN V EN TOR.
Edward I? Spaine WITNESS- 4 by ATTORNEY April 24, 1951 -E. P. SPAINE 2,550,611
: THREAD TRIMMING MECHANISM FOR SEWING MACHINES Filed Oct. 22, 1948 4 Sheets-Sheet 2 INVENTOR.
Edward P Spa/ins BY- i [L y w April 24, 195]. E. P. SPAINE 2,
THREAD TRIMMING MECHANISM FOR SEWING MACHINES Filed Oct. 22, 1948 4 Sheets Sheet 5 INV EN TOR. Edward B zvm'ne/ WITNESS, BY A 7%; I ;M 21
Ap 1951 E. P. SPAINE 2,550,611
THREAD TRIMMING MECHANISM FOR SEWING MACHINES Filed Oct. 22, 1948 4 Sheets-Sheet 4 i INVENTOR.
70 r Edward PAS U /ine ATTORNEY Patented Apr. 24, 1951 UNITED STATES-i- O- F-FIGE THRE'AD' TRIMMING MECHANISM FOR- SEWING MAGHINE'S.
Edward P; spainaBridgeport', Conn, assignor. to
The. Singer Manufacturing; Company; Elizabeth, Ni 1., a corporation'of'NewJersey- Applicationoctober 22, 19.48,.SeriahNo. 55,894
12 Claims. 1;
This: invention: relates to sewing. machines and more particularly to an improved. thread-trim ming mechanismedapteddor an; adjustable automatic group-stitch sewingmachine of thebuttonhole type; which. thread-trimming: mechanism. willl cut: and; hold: the needle-thread between sewingqperiods;.releasing the needle-thread at the beginning; ofqfaisewing'operation and so controlling.- the: needle-threads that the. beginning end thereof: will, berdrawm down flush with. the work.
Adjustable machineshave been produced for sewing: huttonholes; ofivarious lengths. In theseat; the: end ofi thesewing operation the lead of. therneedle-thread fromthelast stitchzin the work to the eye of the needlerlies within the range. of movement:of'the'trimmer. If it is desired to'rcut the: needle thre'adra t the" end of the. rapid feed insteadtofijwhen the-stitching mechanism is first stopped;,. the leadiof the: needle-thread becomes important; as to whether the needle-thread is severed. Eorexample; wherr the machine is set tos'sew the longest buttonhole within the range of thezmach'ine, the lead of theneedle-thread at the endsof thestitching operation-is such that thecthrea'd ,is readily. straddled by the two-relatively movable cutting members oi'the threadtrimmer as'the trimmer'device moves. into thread severing-,ipesition"; When the machine is adjusted so that it' produces a very short .buttonhole, the lead. ofthe needle-thread is; not' as favorable to the trimmer as it is.when the. machine is set to sew-;a-.. 1ong huttonhole. It happens occasionally that when the, thread-trimmer moves into threadesevering, position'the thread is. missedand consequently notcut by the. trimmer. If the thread-trimmer. is. set tov unerringly cut the needlerthread when the machine is adjusted to sent the shortest. buttonhole within. the range of the machine, there. is. the possibility of missing the needle-thread. when the machine is adjusted tosew the longest huttonhole within the. range of the. machine with the same setting of the trimmer device.
Itis the primary objectof the present invention. to provide a threadetrimming" mechanism 2:- an adjustable automatic. group-stitch sewing machine regardless ofthe direction oflead'of the needle threadf. iromthe laststit'ch inthe work.
With the ahove and other objects in view, as willlhereinafter. appear, the invention comprises the devices combinations, and arrangements of parts hereinafter set". forth andillustratedinithe accompanying drawings. of a preferredembodiment of the invention, from which? the several features of the invention andthe' advantages'attaihedthereby will be readily understood by those skilled in the art;
of the accompanying"drawings;.Fig: 1"Iis' a'left side elevation of a buttonhole sewing machine embodyingithe invention.
Fig; 2' is a front end elevationof themachine with the bracket-arm and, the lower platesofthe work' holder" in transverse section:
Fig. 3 is a horizontal section through the bracket-arm standard of the machine;- showing the thread trimming-mechanism in-elevation:
Fig: 4' isa section takensubstantially along, the line4-4,' Fig: 3'.
Fig? 5' is an enlarged perspectiveview of the trimming" device" and its actuating" connections showing; in" full lines, the device *inits normally closed orinoperative positiorr and; indotted lines; the thread-cutting knife in its open position prearatory-- to itsadvance into needle-straddling position;
Fig. e is a view similar-tdFig. 5;- but showing; indotted lines; the thread -trimmer needlestraddling position and; in full lines,- theth-read' trimmer in closed position after having moved intoits lowermostpositionbelow 'the'needle;
Fig-1' 7' represents a= section" takensubstantially along the line 1--,-'! Fig. 5
Fig. 8-- is a: plan view of the thread-cutting members with the cover-plate removedtoshow the *pivotal support of the movable-knife elementi Fig. 9-is an enlargedtransverse section ofthe thread-cutting and thread nipping bladesg showing'the needle-thread-after it is cut with thebeginning 'end nipped;
Referring morein detail t'o the drawings,- the invention is shown asembodied in g a buttonhol'e sewingmachineehaving; in general; constructive features which are-substantially in-- accordance with the disclosure in the U2 S. patent of. ELB: Allen, No;- 155324; reissued- April-4; 1922; The machine is constructed with a frame having a bed" 20 from one-endof which rises a: standard 2| of an overhanging bracket arm'fl terminating inahead-23 which will'unfailingly'sever the needle-thread of The stitch-formingmechanism is-constructed about a vertical axis, as in placing the stitches a radially about the eyelet-end of a buttonhole and between sewing periods to restore the stitching devices to their initial position. The means to so turn the stitch-formingdevices comprise the usual upper and under sector-gears 29 and 30 each having arms 3| and 32 connected by links 33 and 34 to rock-arm 35 and 36 carried on the opposite ends of a vertical shaft 31. The vertical shaft is oscillated by a cam-follower roll (not shown) entering a suitable stitch-rotating camgroove formed in the bottom face of a feed-wheel 38 (Fig. 1). The stitch-forming devices are driven by the main sewing shaft 39, the period of operation of which is controlled by a stopinotion device which includes 'the usual tilting stop-motion lever 45 (Fig. 1) fixed on the rockshaft 41 to which is fixed an arm 42. The arm $2 is connected by a limb 43 to a'lever 4d fulcrumed on the bed 20 at 45 and carrying a follower-nose 46 in position to be engaged by the start-sewing cam 41 adjustably secured on a pattern wheel d8 fixed to a cross rotary shaft 49 which is geared to and runs one-to-one with the feed-wheel 38. The pattern wheel is also formed with a stop-sewing drop-01f cam 50 which, when it travels past the follower-nose 4B, permits a coil-spring to snap the stop-motion lever 40 into stop position, shown for example in Fig. 1.
control trips 41 and 50 for the stop-motion lever being adjustably secured on the pattern wheel &8 carried on the cross rotary shaft 49.
As previously mentioned, buttonhole sewing machines of the type herein disclosed have been produced for sewing buttonholes of various lengths and in these machines the work-holder travels over a fixed maximum distance. Adjustable means are provided to control the position in said work-holder travels where the stitchforming mechanism is started and stopped. In
" the present case, these means are the cam-ele- The work-clamp is of the traveling type. It is first rapidly moved over the bed 20 to carry the work forwardly from initial or buttonhole-cutting position to stitching position, then more slowly moved in step-by-step fashion to place the stitches about the buttonhole, and then rapidly returned to initial position. The work to be sewn is held through the entire cycle in the workclamp which includes the lower clamp-plates 52 and upper. clamping feet 53. The lower clampplates are carried by the usual cross-slide 54 (Fig. 2) which is adapted to slide laterally of the machine-bed 25 on a longitudinal slideframe' 55 shiftable in ways longitudinal of the machine-bed. The work-clamp is given its 1ongitudinal travel and lateral components of its feeding movement by suitable lever-connections with the feed-cam 38 mounted in the bed 20 of the machine and driven at a rapid rate prior and subsequent to the sewing period by the cross rotary shaft 49 which receives power from a rapid-feed shaft 56 (Fig. 1)- through an automatically controlled clutch (not shown). The lever-connection, together with the automatically controlled clutch, are constructed substantially in accordance with the disclosure of said U. S. Reissue Patent No. 15,324. The feed-cam 38 is more slowly driven'during the sewing operation by a suitable gear-train, indicated generally as 51 in Fig. l; actuated from the main sewing shaft 39, the period of operation of which is controlled by the stop-motion device 45, all in the manner fully disclosed in the above mentioned Reissue Patent No. 15,324. As previously mentioned, means is provided for automatically throwing the stopmotion lever into and out of operation to start and stop the stitch-forming mechanism, the
ments 4? and 50, both of which are adjustably securedon the pattern Wheel 48. The pattern wheel is detachably fastened on the cross rotary shaft 49 and can be readily removed and replaced by a universal pattern wheel such as disclosed in my U. S. Patent No, 2,301,797, issued November 10, 1942, when it is desired to fit the machine for a wide range of buttonhole sizes. It will be appreciated that the direction of lead of the needle-thread from the needle to the last stitch of a completed buttonhole may vary with the length of a completed buttonhole and to provide a needle-thread trimmer which will unerringly sever the thread regardless of its direction of lead, I have invented a thread-trimmer which advances into an intermediate needlestraddling position in its travel from inoperative or retracted position to thread-cutting position. The advantage of this action is that'the needlethread is positively disposed between the cutting elements of the trimmer by virtue of the fact that the two cutting elements of the trimmer Q approach the needle and straddle it with one of the elements on either side of the needle blade, after which the cutting elements drop below the point of the needle and close on the thread to sever it. Obviously, in straddling the needle the thread carried thereby is introduced between the cutting elements and when the cutting elements drop into cutting position below the needle the thread is properly located between the cutting elements and is severed.
The details of my improved thread-trimmer are best illustrated in Figs. 5 and 6. The device is preferably constructed as a detachable unit and comprises a bracket or base 58 secured by screws 59 and 6!) (Fig. 3) to the lower end of the usual stationary pivot-stud El of the needleturning sector-gear 29. Secured, as by screws 62, to the front end of the base 58 is an anglebracket, indicated generally as 63, having a depending vertical limb 64 to which is fulcrumed at 65 a carrier-lever 66 formed at one end with a bearing support 61 (Fig. 7) in which is journaled a tubular fulcrum-shaft 68. Integral with one end of the tubular fulcrum-shaft 68 is a head 69 to which is fastened by screws '10 a trimmer body-member H having an offset lower end 72 providing a supporting ledge for a thin knife-blade 13 of the thread-cutting and -nipping scissors device. The stationary knife-blade 13 has a sharpened knife-edge 74 (Fig. 8). Cooperating with the stationary knife-blade i3 is a movable knife-blade 75 sharpened at 16 and supported for oscillation about a pivot-screw TI threaded into the supporting ledge 12 of the trimmer body-member 1|. Positioned above the movable knife-blade 75 is a thread-nipping plate 18 secured by screws 11 and 19 and held in proper thread-nipping relation with the upper surface of the movable knife-blade 15 by spacing washers 86 and 81. An adjusting screw 82 extending through the thread-nipping plate 18 position beneath the needle.
and threaded into the stationary knife-bladeprovides for maintainingtheproper spaced relation between the blades '14, I5 andthe plate'I8.
The movable knife-blade "I5 is formed with a shank 83 (Fig. 8) bifurcated to straddle a roller 84' carried at one end of a slide-bar 85 located in a slideway 96 formed in the bodymember II. The other end of the slide-bar 85 is enlarged and notched, as at 81, to receive the spherical end 89 ofa rock-arm 89 preferably formed integral with a knife-actuating rockshaft 90 journaled' in the tubular fulcrum-shaft 68. From the'foregoing it'will be apparent that a rocking of the shaft 90 in one direction will close the cutting blades and at the same time nip the needle end of the thread between the movable blade I5 and the nipping-plate 18, while a rocking of the shaft 99- in the opposite direction will open the'bladesand release the nipped end of the needle-thread. In addition to the opening and closing of the cutting blades, the entire scissors device must be bodily moved into its. intermediate needle-straddling position following which it is lowered into thread-cutting The meansby which this bodily movement of the scissors device and the opening and closing of the cutting blades areobtained will now be described. The carrier-lever tit-is forked at one end to receive a slide-block 9| having a. ball-and-socket connection with one end of a rock-lever 92' pinned at its other end on a rock-shaft 93. journaled in the. spacedidepending ears 94 (Fig. 4.) formed cnthe base 58. Clamped on one end. of the rockshaft. 93;.is. a lever-arm in. the form of a block 95. in; which isslidably mounted a spring-pressed plunger 96v having an. inclined upper end 91. Cooperating with the plunger 96 is an overhanging trip-finger 93 fastened on a mounting block 99 adjustably secured by screws I90 on the sectoregear actuating link 33. A spring IOI coiled abouththe rock-shaft 93 and having one of its ends hooked over the rock-lever 92 functions. to maintain the trimming device in its retracted. or inoperative position shown in Figs. 1. and 2'. From-the foregoing it. will be understood. that when the sector-gear actuating. link .33 is moved edireetion. of the. arrow in Fig.3 to disperse he itches abou th ey of the buttonhole, the triprfinger. en a es and epresses the plun r 9.6. passing idly by it, without actuating the trim.- mer, Durin the return movement of the sectorgear actuating link 33 when restoring the stitching devices to their initialposition at theend of the rapid feedof the work-holder,thetrip-finger 98 engages the. plunger 96 and causes it to turn the rock-shaft 93 in a direction to raise the free end of, therock-lever 92. The raising of the rocklever swings the carrier-arm 66 about its pivot 65, causing the trimmer device to move downward toward its thread-cutting position. Means are provided for controlling the position of the bodymember I l' of the trimmer device and this means includes an arm I102 secured on the tubular fulcrum-shaft 68 (Fig. 7) and carrying at its lower end a roller I 03 adapted to track an arcuate slot IM- formed in the" vertical limb 64 of the anglebracket 63. The compound motion obtained from theswingingofthe carrier-lever 66 and the turning of the tubular fulcrum-shaft68, resulting from the tracking of the roller I93 in the arcuate slot I94, imparts movement to the trimmer device such that the opened knife-blades move downwardly and forwardly into needlestraddlingpositionand then drop downwardly parallel to theblade-of the needle toa point below the point of theneedle, where theblades are then closedto sever the needle-thread. The actual closing of the knife-blades is effected by means of a cam-surface I 05 formed on the edge of the vertical limb 64 of the bracket 65, which cam-surface is adapted to be contacted by a roller IilIi carried by a rock-arm I U'I- fast onthe knife-actuating rock-shaft 99. Swinging of the carrierel'ever 66, in addition to positioning. the knife-blades on either side of they needle and subsequently dropping them below the needle, moves the roller I06 into engagement with the cam-surface 195-, which turns the shaft 90 and swings the movable blade 15. into. thread-shearing engagement with the stationary blade I3. When the movable knife-blade I5 swings toward the stationary blade 13, the thread is first nipped betweenthe bottom of the thread-nipping plate I8 and the top of the movable blade I5, following which the thread is severed. The beginning end of the thread is held until thestart of the stitching devices in the next buttonholing cycle.
The means employed for opening the knifeblades to release the thread-end and toposition the blades for their next thread-cutting operation, are operated bythe swinging of the stopmotion lever ii] out ofits stop-position, which occurs when the stitchingdevices are started at theend of the initial rapid feed. The means preferably includes a trimmer opening push-rod I08 (Figs. 1 and 2) secured at its inner end at I09 to the tilting; stop-motion lever 40 and freely slidableadjacent its outer-end in a guide III] attached to the block 9-9. The outer end of the push-rod I98 is adapted to contact one limb of a bell-crank lever I I I pivoted at M2 on the base 58, The other limb of the bell-crank lever is'forked to straddle a pin H3 carried at one end of a slide II 4 endwiseshiftable in a guideway IIES in the base 58, a retainer-plate I16 serving to maintain the slide in said guideway. At its other end, the slide H4 is formed with an- L-shaped finger II'I defining an opening II8 adapted to be entered by a pin H9 projecting from a collar I20 fast on the knife-actuating rock-shaft 99. The pin II9- enters the opening I I8 when the trimmer device swings upwardly from thread-cutting position, shown in full lines in Fig; 6; to retracted position, shown in full linesin Fig. 5. When the pin H9 is in the opening 8- it is in position to be engaged by the finger I-I'I when the slide II 4 is shifted from full line position to dotted line position, Fig. 5, under the'action of the push-rod I08 moving into contact with and turning the bellcrank lever I I I about its pivot I I2; As shown in Fig. 5, when the pin H9 is engaged and moved by the finger I I1 the knife-actuating rock-shaft 90 is turned in a direction to shift the slide-bar in the body-member II and open the knifeblade 15;
Operation starte-sewing cam 41 into contact with the follower nose 46, whereby the stop-motion lever 46 is tilted from stop position to stitching position, shown in dotted lines in Fig. 1. Tilting of the stop-motion lever 40 moves the push-rod I08 in the direction indicated by the arrow in Fig. 5. The push-rod I08 when moved endwise engages one limb of the bell-crank lever lll causingthe lever to turn about its pivot H2 and move the slide I Hi from the full line position to the dotted line position, Fig. 5. In so moving, the finger Ill engages the pin H9, thereby turning the knifeactuating rock-shaft 90 in a direction to shift the slide-bar upwardly and move the knife-blade 75 into its open position. When the knife-blade "i5 is moved to open position, the beginning end of the needle-thread is released and the trimming device is set for the subsequent thread-cutting operation. Preferably the trimmer is so located with respect to the needle that the released thread-end will be of a length such that it will be drawn down flush with the work in the formation of the first stitch.
When the stop-motion lever 40 is tilted, the stitching mechanism is thrown into operation to produce the first side, the eye and the return side of the buttonhole. In sewing the eye of the buttonhole the stitching mechanism is turned about a vertical axis as previously explained. In turning the stitching mechanism about the vertical axis, the sector-gear actuating link 33 moves to the right (Fig. 1) and carries with it the mounting block 99 supporting the overhanging tripfinger 98. The trip-finger 98 engages and depresses the plunger 96, passing idly by the block 95 without affecting the trimmer.
After the buttonhole is completed and the rapid feed has returned the work-holder to its loading position, the stitching mechanism is reversely turned about the vertical axis to restore it to initial stitching position. During the return movement of the sector-gear actuating link 33, the trip-finger 98 engages the side of the plunger 96 and thereby rocks the block 95 in a direction to turn the rock-shaft 93 and raise the free end of the rock-lever 92. The raising of the rock-lever 92 swings the carrier-arm 66 about its pivot E5, causing the trimmer device to move downward in the general direction of the needle 24. During the swinging of the carrier-arm 6B, the roller H33 travels downward in the arcuate slot I04. The swinging of the carrier-lever 6B and the action of the roller I63 tracking the slot :84 impart a compound motion to the trimmer body-member H such that the opened knifeblades move into needle-straddling position, shown in dotted lines in Fig. 6, following which the trimmer device drops below the needle-point, the path of travel of the trimmer device being indicated by the dot-and-dash line in Figs. 5 and 6. During the dropping of the trimmer device from needle-straddling position to thread-cutting position, the roller I06 engages the cam-surface I85 and thereby effects a turning of the knifeactuating rock-shaft 90 in a direction to swing the movable knife-blade 15 into thread-nipping relation with the plate 18 and thread-severing relation with the stationary knife-blade 13. It will be appreciated that the needle-thread is positively admitted between the knife-blades by virtue of the fact that the knife-blades first straddle the needle with one blade on either side of the body of the needle between the eye and shank thereof and then drop to a point below the needle. It will be understood also that once the thread is between the knife blades 13 and 15- it cannot escape because the direction of movement of the trimmer device toward and from cutting position is transversely of the path of travel of the workholder. In other words, there is no tendency for the thread to escape through the opening between the free ends of the knife-blades. It will be seen in the drawings that the thread-engaging edge of the nipping plate 18 is curved in a direction to minimize the possibility of the thread escaping by the free end of the nipping plate.
In order to insure that the opening H8 in the slide I I4 is positioned vertically above the pin I I9 so thatthe latter will surely enter the opening when the spring 10! snaps the trimmer device into elevation or retracted position immediately following the thread-cutting operation, the block is designed so that as it is rocked backwardly under the action of the trip-finger 98 its rear edge engages the limb of the bell-crank lever Hi and reversely swings the lever into the position shown in full lines in Fig. 5. In this position the opening H8 is disposed to' be entered by the pin H9 when the trimmer device swings upwardly.
Having thus set forth the nature of the invention, what I claim herein is:
1. A sewing machine having stitch-forming mechanism including a thread-carrying needle having an eye and a shank, work-feeding mechanism, a needle-thread trimmer device including a pair of relatively movable thread-severing blades, said trimmer device having a retracted position, an intermediate needle-straddling position in which said thread-severing blades are separated and arranged on opposite sides of said needle at a level between its eye and shank, and a thread-cutting position spaced from said needle. means for shifting said trimmer device from retracted position to needle-straddling position and then to thread-cutting position, and connections for effecting a relative movement of said threadsevering blades into thread-severing relation.
2. A buttonhole sewing machine having stitchforming mechanism including an upper threadcarrying needle having an eye and a shank and complemental under thread mechanism, a workholder, means for relatively moving the stitchforming mechanism and work-holder to sew about a buttonhole, connections for turning the stitching mechanism about a vertical axis to sew around the end of the buttonhole, a needle-thread trimmer device including a pair of relatively movable thread-severing blades, said trimmer device having a retracted position, an intermediate needle-straddling position in which said threadsevering blades are separated and arranged on opposite sides of said needle at a level between its eye and shank, and a thread-cutting position spaced from said needle, mechanism operatively associated with said stitching mechanism turning-connections for successively advancing said trimmer device from retracted position to needlestraddling and thread-severing position, and means for effecting relative movement of said thread-severing blades into thread-severing relation.
3. A buttonhole sewing machine having stitchforming mechanism including an upper threadcarrying needle and complemental under thread mechanism, a work-holder, mechanism forrelatively moving the stitch-forming mechanism and work-holder to sew about a buttonhole, connections for turning the stitching mechanism about a vertical axis to sew around the end of rass eri the buttonhole, a, stop-motion device for starting and stopping the stitch-forming mechanism, a shiftable needle-thread trimmer device including @a pair of relatively movable thread-severing blades, mechanism operatively associated with 'said stitching mechanism turning-connections for shifting said trimmer into thread-severing position and foriclosing said blades into threadsevering relation, and mechanism operatively connected with said stop-motion device for opening said trimmer-blades.
4. A buttonhole sewing machine having stitchforming mechanism including an upper thread- ,carrying needle having an eye and a shank and complemental under thread mechanism, a workholder, means for relatively moving the stitchforming mechanism and work-holder to sew about a buttonhole, connections for turning the stitching mechanism about a vertical axis to sew around the end of the buttonhole, a needlethread trimmer including a pair of relatively -movable thread-severing blades, said trimmer desaid trimmer in the advancing movement of the trimmer, and spring means to return the trimmer to its retracted position following the threadsevering action.
5. A group-stitch sewing machine having stitch-forming mechanism including an upper endwise reciprocatory thread-carrying needle, a work-holder, mechanism for relatively moving the stitch-forming mechanism and the workholder to sew about a predetermined pattern, a stop-motion device for starting and stopping the stitch-forming mechanism, a needle-thread trimmer including a pair of relatively movable blades, meansto close said trimmer-blades to sever the needle-thread, and means operatively connected with said stop-motion device for opening said trimmer-blades.
6. A group-stitch sewing machine having stitchforming mechanism including an upper endwise reciprocatory thread-carrying needle, a workholder, mechanism for relatively moving the stitch-forming mechanism and the work-holder to sew about a predetermined pattern, a stopmotion device for starting and stopping the stitch-forming mechanism, a needle-thread trimmer including a pair of relatively movable blades, means to close said trimmer-blades to sever the needle-thread, a push-rod operatively connected to said stop-motion device, and blade-opening mechanism operatively associated with said pushrod.
7. A thread-trimming device for a sewing machine having a frame including an overhanging bracket-arm, comprising, a lever fulcrumed on said bracket-arm, a threadcutting scissors device mounted on said lever and movable therewith from retracted to thread-severing position, means to close said scissors device in its advance from retracted to thread-severing position, and connections to open said scissors device when it is returned to its retracted position, said connections including a slide operatively connected to said scissors device, a lever for shifting said slide, and an automatically actuated push-rod adapted to engage said lever.
8. A thread-trimming device adapted for a buttonhole sewing machine having stitch-turning mechanism and a stop-motion device, com prising, a base, a scissors device movably supported on said base for movement from retracted to thread-severing positions, means adapted to be actuated by said stitch-turning mechanism for advancing said scissors device to thread-seven ing position and closing said scissors device into thread-severing position during the advancing movement thereof, and means operatively associated with said scissors device when the latter is in retracted position for opening the same in preparation for its next thread-cutting operation, said last named means adapted to be actuated by said stop-motion device.
9. A needle-thread trimmin device for sewing machines having a thread-carrying needle provided with an eye and a shank, comprising, a supporting member, a carrier lever fulcrumed on said supporting member, a shaft journaled in said carrier-lever, a trimmer device supported by said shaft and including a pair of relatively movable thread-severing blades, connections provided for swinging said carrier-lever about its fulcrum to move said trimmer device into a needle-straddling position in which the thread-severing blades are separated and disposed at opposite sides of said needle at a level between its eye and shank, means provided for turning said shaft in said carrierlever to lower said trimmer device to a position in which the thread-severing blades are below the needle, and connections provided for eifecting relative movement of said thread-severing blades into thread-severing relation.
10. A needle-thread trimming device for sewing machines having a thread-carrying needle provided with an eye and a shank, comprising, a supporting member, a carrier-lever fulcrumed on said supporting member, a shaft journaled in said carrier-lever, a trimmer device supported by said shaft and including a pair of relatively movable thread-severing blades, connections provided for swinging said carrier-lever about its fulcrum to move said trimmer device into a needle-straddling position in which the threadsevering blades are separated and disposed at opposite sides of said needle at a level between its eye and shank, means rendered effective by the swinging of said carrier-lever for turning said shaft in said carrier-lever to lower said trimmer device to a position in which the thread-severing blades are below the needle, and connections also rendered effective by the swinging of said carrierlever for closing said thread-severing blades into thread-severing relation.
11. A needle-thread trimming device for sewing machines having a thread-carrying needle provided with an eye and a shank, comprising, a supporting member having a cam-slot and a camsurface, a carrier-lever fulcrumed on said supporting member, a shaft journaled in said carrierlever, a trimmer device supported by said shaft and including a pair of relatively movable threadsevering blades, connections provided for swinging said carrier-lever about its fulcrum to move said trimmer device into a needle-straddling position in which the thread-severing blades are separated and arranged at opposite sides of said needle at a level between its eye and shank, an arm secured to said shaft and having one end operatively connected to said cam-slot for turning said shaft in said carrier-lever to lower said trimmer device to a position in which the threadporting member, a tubular shaft journaled in said carrier-lever, a trimmer device carried by said tubular shaft and including a pair of relatively movable thread-severing blades, connections provided for swinging said carrier-lever about its fulcrum to move said trimmer device into a needle-straddling position in which the threadsevering blades are separated and arranged at opposite sides of said needle at a level between its eye and shank, an arm secured to said tubular shaft and having one end operatively connected to said cam-slot for turning said tubular shaft in said carrier-lever when the carrier-lever is swung about its fulcrum to lower said trimmer device to a position in which the thread-severing blades are below the needle, a knife-actuating shaft journaled in said tubular shaft and operatively connected to at least one of said thread-severing blades, and an arm connected to said knife-actuating shaft and disposed to engage said camsurface during the' latter part of the swinging stroke of said carrier-lever to close said threadsevering blades into thread-severing relation.
EDWARD P. SPAINE.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS