US2487389A - Thread-trimming mechanism for sewing machines - Google Patents

Description

D. G. SMITH ET AL THREAD-TRIMMING MECHANISM FOR SEWING MACHINES Y 4 Sheets-Sheet 1 Filed Nov. 14, 1947 INVENTORS @arwin G. Smith and .Harold C(Fvwlkner ATTORNEY 4 Sheets-Sheet 2 INVENTORS ATTORNEY Darwin GTSmitk and, Jlarold GfiauZkz zer Nov. 8, 1949 D. G. SMITH El AL THREAD-TRIMMING MECHANISM FOR SEWING MACHINES Filed Nov. 14, 1947 1:). 6. SMITH ET AL 2,487,389

THREAD-TRIMMING MECHANISM FOR SEWING MACHINES 4 Sheets-Shet 3 NOV. 8, 1949 Filed Nov. 14, 1947 1 N V EN TORS .fiarwin, G. Smith and By Harold C'- Faulkner WI TNESS: fl ATTORNEY Nov. 8, 1949 D. G. sM H r AL 4 2,487,389

THREAD-TRIMMING MECHANISM FOR SEWING MACHINES Filed Nov. l4, 1947 4 Sheets-Sheet 4 JIIIA'IIIIII. l

' 1N VEN TORS @arwz'n 6'. Smith and WITNESSI: By Jfaz old C(Fzwlner A TTORNE' Y Patented Nov. 8, 1949 H I I 2,487.389

UNITED STATES PTENT OFFICE THREAD-TRIMM'ING MECHANISM FOR SEWING MACHINES Darwin G. Smith and Harold C. Faulkner, Bridgeport, Conn., assignors to The Singer Manufacturing Company, Elizabeth, N. J a corporation of New Jersey 1 Application November 14, 1947, Serial No. 786,016

Claims. (112252) 1 2 This invention relates to sewing machines and Fig. '7 is an enlarged vertical sectional View more particularly to thread-trimming mecha taken substantially along the line 1--l, Fig. 2,

nisms for machines of the group-stitch type, showing the needle-thread just after it has been such as tacking machines, button-hole machines, severed with the beginning end of the needleeyelet machines, etc. thread nipped for the beginning of the subsequent The invention aims to improve the thread-trimstitching cycle. ming and -nipping mechanism disclosed in the In the preferred embodiment of the invention,

U. S. patent of A. R. Wood, No. 1,920,944, dated the eyelet machine illustrated in the drawings Aug. 1, 1933, so that after the thread has been ompri a fr m in n a bed it uppor n cut and the beginning end of the thread nipped a standard I! of an overha in e -arm the work-clamps may be opened to release the 12 terminating in a head l3. Mounted in the work without causing any inadvertent shift of e d 3 is t e usual reciprocatoly needle-bar the nipping blade which would prematurely re- M carrying a needle I5 which, together with the lease the nipped end of the thread, regular under-thread mechanism mounted with- Another object of the invention is to provide 15 in the bed i0, constitutes the stitch-forming mechactuating mechanism for the trimmer-blade conanism- This mechanism is adapted turnedstructed so that it will not encroach upon th abouta vertical axis to disperse the stitches about work-clearance space beneath the work-clamp the eyelet he Stitch-forming mechanism' is arms and will not interfere with the movement 0 driven from the main sewin S 56 Wh of the Work-clamp into and out of work-clamping iv s its power m a us y running position. belt-driven pulley H. The period of operation With these nd other Objects in view, as will of the stitch-forming mechanism is controlled by hereinafter appear, the invention consists in the the usual Start" and Stop-motion ce including thread-trimming and -nipping device described e t l Stop-motion v l8 Which, When 1 in connection with the accompanyin drawings erated effects the coupling of the main-shaft it to which illustrate a preferred embodiment of the the pulley invention and in which: As fully explained in the U. S. patent of E. B.- Fig. 1 is a right side elevational View of an eye- Allen. dated y 1920, there is let machine embodying the invention, portions incorporated in the machine the usual eyeletu of the machine being broken away. ter shaft It which makes one revolution prior to Fig. 2 is an enlarged top plan view of portions Sewing and en comes to rest, and a Second of the work-clamp and of the machine-frame, auxiliary shaft 20 which is stationary dur the showing the actuating mechanism for imparting Operation of e Shaft 59 and main-Shaft 95 and the required thread-trimming and -nipping makes one revolution after the sewing is commotions to the trimmer. pleted, to perform certain desired operations after Fig. 3 is a plan View of the feed-wheel, together Stitching, Such as t p ning of the work-clamp. with a portion of the mechanism for rapidly rotatand the rapid drive of the feed-wheel 2| to restore ing the feed-Wheel at the end of the sewing operit to initial position. These shafts l9 and 28 are ation, and that part of the thread-cutter mechadriven from a Continuously unning belt-pulley nism actuated by the feed-wheel reversing mech- 1? through u b y Co t o o u o anism. clutch-devices, as fully explained in the above Fig. 4 is a top plan view of a portion of the mentioned Allen Patent No. 1,346,102. right hand work-clamp section, showing the For a clear understanding of the present in thread-trimming blade in set position preparatory vention it will'be sufiicient to explain that, to to the retrimming of the beginning end of the rapidly drive the feed-cam 2|, the second auxilneedle-thread. iar shaft 20 is formed with a crank 23 which Fig. 5 represents a vertical section taken subis connected by a pitman 24 to an arm 25 mlstantially along the line 55, Fig. 2, showing, in crumed coaxially with the feed-wheel and piv dotted lines, the position of the parts when the i thread-trimming blade is open and, infull lines, spring 21 (Fig. 1) to ride on the-periphery of the otally carryin a pawl 26 whichisurged by a the position of the parts when the thread-trimfeed-cam and acts upon a tooth 28 onthe feed-- ming blade is closed. wheel during the single rotation of the crank 23;

Fig. 6 is an enlarged vertical sectional view rapidly turnin the feed-wheel at one sweep fromv taken substantially along the line B-6, Fig. 2. its position at the end of a sewing operation to initial position ready to begin a new cycle of operations.

The work is adapted to be held in a workclamp during the sewing operation. The workclamp which is shown in the drawings forms the subject of pending application Serial No. 786,014, filed Nov. 14, 194'? in the name of H. C. Faulkner, and includes lower clamp-plates 23, 36 and opposed upper clamp-feet 3|, 32. The clamp-feet are pivotally fastened by means of pivot-screws 33, 34 to the free ends of the arched clamp-arms 35 and 36, each of which is fulcrumed at its rear end on a hinge-pin 31 provided .in;a supporting bracket 38, only the bracket for the clamp-arm 35 being shown in the drawings. The clamp-foot 3| is yieldingly held against the work, when the work-clamp is closed, by a coil-spring 39 which is interposed between the arm 35 and a thumbnut 40 threaded on a pull-rod 4|. As fully shown and described in the pending application above referred to, thereis provided suitable toggle mechanism connected .Withthe pull-rod 4| for effecting the closing and opening of the work-clamp. The clamp-arms 35, 36 are appreciably arched and the fulcrum supports for said arms are disposed considerably back from the feet 3|, .32 in order to provide ample work-clearance space beneath the arms.

The needle-thread trimming and -nipping mechanism now to be described-comprises a trimmer-blade 42 and .an overlying nipper-blade 43 (Figs. 4, and '7), the shanks of which are secured to the lower end of the usual vertical rockshaft 44 journaled in the clamp-foot 3|. This construction is substantially the sameas that disclosed in the U. :S. patent of E. B. Allen, No. 885,310, dated April '21, 1908. The thread-trimming and nipping blades 42 and 43 are adapted tooperate ina horizontal slot defined between a section 45 of the clamp-foot 3| (Figs. 6 and 7) and the surface of a hardened detachable section 46 secured to the clamp-foot 3|. The nipperblade 43 cooperates with the section 45 as shown in Fig. 7 to hold the beginning end of the thread during the sewing of the first portion of the eyelet. The trimmer-blade 42 has a sharpened edge which cooperates with an edge on the detachable section 46 in severing the needle-thread.

The'trimmer-blade carrying rock-shaft 44 has fixed .on its upper end a rock-arm 41 connected by a link 48 to a rock-lever 49 freely pivoted on a'stud 50 threaded into the clamp-foot 3|. Depending from the rock-lever 49 is a ball-stud 5| embraced by .the socketed front end of an actuating link 52 arched in substantial conformity with the clamp-arm 35 (Fig. 1) and connected at its rear end to the upper end of a trimmer-opening lever 53 pivoted intermediate its ends on a stud 54 threaded into the supporting bracket 33. Rising from the upper end of the trimmeropening lever 53 is a projection 55 to which is attached one end of a coil-spring 56 connected at its other end to an ear 51 secured to the clamparm 35, the coil-spring acting to bias the trimmeropening lever 53 into trimmer-blade closed position determined by a buffer pad 58 secured to the trimmer-opening lever 53 contacting an upstanding stop 59 provided on the clamp-arm 35. As will be seen in Figs. 2, 6 and '7, when the trimmerand nipper-blades 42 and 43 are in closed position. the center of the ball on the ball-stud 5| is disposed in alinement with the longitudinal axis of the pivot-screw 33. It will be appreeiated that while this alined position of the balleand-socket joint of the link 52 with the pivot-screw 33 is maintained, any tilting of the clamp-foot 3| about the axis of the pivot-screw 33 while the work-clamp is opened will not cause the trimmerand nipper-blades 42 and 43 to shift in the slot in the clamp-foot 3|. Obviously, since no accidental shift in the blade 43 occurs the beginning end of the thread is held securely regardless of whether the clamp-foot 3| is tilted about the pivot-screw 33 during the insertion or removal of work ,from the opened work-clamp.

The thread-trimming and -nipping blades are adapted to be operated twice for each complete stitching cycle, once before the sewing is completed to retrimt-he beginning end of the needlethread, the operation being performed preferably after the sewing has progressed to the point where the beginning endcannot be sewed in or bound down by the stitching, and a second time after the sewing is completed to cut the needle-thread close to the work and hold the beginning end of the needle-thread for the beginning of the next sewing operation. A thread-trimming mechanism having substantially the same sequence of operations is disclosed, for example, in the U. S. patent of A. R. Wood, No. 1,839,823,.issued Jan. 5, 1,932. In-the present case, the first or retrim operation isperformed by meansactuated by the feed-cam 2|. This means preferably comprises a vertically disposed rock-shaft 66 journaled in the bed 56 and having attached to its lower end an arm 6| having its inner end underlying the feed-cam and disposed to be engaged by a retrim-cam 62 attached to the under side of the feed-cam 2|. Secured to the upper end of the rock-shaft 66 is a rock-lever 63 provided at its outer end with a slot 64 disposed to receive a screw 65 threaded into a push-lever 66 fulcrumed at one end on a pivot-stud 61. The free end of the push-lever 66 is arranged to swing into engagement with the lower end of the trimmeropening lever 53. A spring 68 bears against the push-lever 56 and urges itinto an inoperative position determined by a stop-pin 66. From the above description considered in connection with Figs. 2 and 4, it will be understood that as the feed-cam 2| turns in the direction of the arrow in Fig. 2, the retrim-cam 62 contacts the free end of the arm 6| which swings it in a counterclockwise direction, transmitting to the push-lever 66, through the rock-shaft 60 and rock-lever 63, movement in a counterclockwise direction also. This movement of the push-lever 66 turns the trimmer-opening lever 53 from the full line position in Fig. 5 to the dotted line position. This turning of the trimmer-opening lever 53 gradually moves the trimmerand nipper-blades 42 and 43 into an open position, shown in Fig. 4. In swinging from closed or thread-nipping position to open position, the beginning end of the needlethread is released .and the trimmer-blade is set for its retrim stroke. As the feed-cam 2| continues to turn. the retrim-cam 62 advances to a point where its drop-off passes the end of the arm SI and when this occurs the coil-spring 56 snaps the link 52 ina direction to close the trimmar-blade 42 upon and retrim the beginning end of the needle-thread close to the work. The spring 68 acts simultaneously with the coil-spring 56 in returning the push-lever 66 and its associated connections to their inoperative position.

To provide for reopening or resetting the trimmer-blade 42 preparatory to the trimming of the finishing end of the needle-thread (Fig. 7) and nipping the beginning end of the needle-thread for the beginning of the next sewing operation,

we have provided a second means actuated by the single rotation of the auxiliary shaft for operating the rock-shaft 60. This means preferably comprises a rock-arm Ill (Figs. 1 and 5) secured to the rock-shaft 60 and extending substantially horizontally immediately above the level of the feed-cam 2|. At its free end the rock-arm I0 is formed with a downturned lip II providing on its inner face a straight cam-wall I2 extending in a direction inclined to and extending across the path of travel of the feed-cam turning pawl 26. The pawl 26 is provided with an upstanding pin I3 which is disposed so that, as the pawl 26 is actuated by the pitman 24 to effect the rapid turning of the feed-cam 2| after the stitching operation is completed, the pin I3 will strike the camwall I2 and swing the rock-arm Ill in a counterclockwise direction and into the position shown in Fig. 3. With the parts in the position shown in Fig. 3, the trimmerand nipper-blades 42, 43 are open or reset. As the pawl 26 continues in its feed-cam turning stroke, the pin 13 travels beyond the end of the rock-arm I0, permitting the spring 56 to snap the trimmerand nipperblades 42, 43 into closed position, whereby the thread is cut and the beginning end nipped (Fig. '7). The spring 68 returns the rock-arm Ill and its associated connections to the position illustrated in Fig. 2. When the crank 23 on the auxiliary shaft 20 travels through the second half of its single revolution, the pawl 26 is returned to its initial position in readiness for its operation at the end of the next stitching cycle. During the return stroke of the pawl 23 to its initial position the pin I3 on said pawl strikes the outside face of the downturned lip II, causing the pawl 28 to turn in opposition to the spring 21 on its pivotal connection with the arm 25, the spring 21 biasing the pawl back so that its toe rests on the periphery of the feed-cam 2| after the pawl passes the back end of the downturned lip I I.

It will be appreciated from the foregoing that we have invented a needle-thread trimmer and nipping device constructed so that the nipperblade is not accidentally shifted and the beginning thread-end released by the tilting of the work-clamping foot on its pivotal support during the insertion or removal of Work or during the traversing of any unevenness in the material due to cross-seams or the like. Moreover, the actuating mechanism for the trimmer and nipping device is arranged so that ample clearance space is provided beneath the work-clamping feet to permit convenient manipulation of the work and to permit the placing of the stitched pattern back from the edge of the work. Also the actuating connections are designed so that they will not interfere with the movement of the work-clamp into and out of work-cutting position, and the position of the pivot 54 of the trimmer-opening lever 53 relative to the hinge pin 31 of the clamparm 35 is such that during the opening and closing of the work-clamp the bufier pad 58 slides up and down on the face of the stop-lug 59 in a direction substantially normal to the axis of the link '52. Thus, no endwise movement is imparted to the link 52 during the opening and closing of the work-clamp and consequently the trimmerand nipper-blade is not disturbed.

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

1. A group-stitch sewing machine having a work-clamp provided with an upper clamp-foot pivotally mounted for tilting movement about a fulcrum-axis, a thread-trimmer and -nipper device carried by said upper clamp-foot, and actuating' mechanism for operating said thread-trimmer and -nipper device; said mechanism including a pair of elements carried by said work-clamp and a ball-and-socket connection between'said elements with the-center of the balldisposedin alinement with the fulcrum-axis of said clampfoot when said thread-trimmer and -nipper device is closed.

2. A group-stitch sewing machine having a work-clamp provided with an upper clamp-arm, a bracket to which said clamp-arm is pivoted, a clamp-foot mounted on one end of said clamparm for tilting movement about a fulcrum-axis, a thread-trimmer and -nipper device carried by said clamp-foot, and actuating mechanism for operating said thread-trimmer and -nipper device, said actuating mechanism including a rocklever pivoted on said clamp-foot, a trimmeropening lever fulcrumed on said bracket, a link connected at one end to said rock-lever and at its other end to said trimmer-opening lever, the point of connection between said link and rocklever being in alinement with the fulcrum-axis of the clamp-foot when said thread-trimmer and -nipper device is closed, and means for operating said trimmer-opening lever.

3. A group-stitch sewing machine having a work-clamp, provided with an arched upper clamp-arm, a bracket to which one end of said clamp-arm is pivoted, a clamp-foot mounted on the other end of said clamp-arm; a threadtrimmer and -nipper device carried by said clamp-foot, and actuating mechanism for operating said thread-trimmer and -nipper device, said actuating mechanism including a rock-lever pivoted on said clamp-foot and operatively associated with said thread-trimmer and -nipper device, a trimmer-opening lever pivoted on said bracket adjacent the pivotal support of said clamp-arm, a link shaped to conform substantially with the arched clamp-arm and connecting said trimmer-opening lever to said rock-lever, and automatically controlled means for operating said trimmer-opening lever.

4. A group-stitch sewing machine having stitch-forming mechanism, a feed-cam for effecting the distribution of stitches in a given pattern, feed-cam rapid-turning means for returning the feed-cam to its initial position after the stitching is completed, a thread-trimmer and -nipper device, and means for actuating said device twice for each complete stitching cycle, said means including a rock-shaft, means operatively connecting said rock-shaft to said thread-trimmer and -nipper device, a reset cam on said feed-cam, a rock-arm secured on said rock-shaft and disposed for engagement by said reset cam to effect one of the operations of said thread-trimmer and .-nipper device, and a second rock-arm secured to said rock-shaft and arranged for engagement by said feed-cam rapid-turning means for efiectin the other operation of said thread-trimmer and -nipper device. 1

5. A group-stitch sewing machine having a work-clamp provided with an upper clamp-arm, a clamp-foot mounted on said clamp-arm for tilting movement about a fulcrum-axis, a threadtrimmer and -nipper device carried by said clamp-foot, and actuating mechanism for operating said thread-trimmer and -nipper device, said actuating mechanism including a trimmer-carrying rock-shaft, a rock-arm secured to said rock-shaft, a rock-lever pivoted on said clampfoot, a link connecting said rock-arm to said IQOKFIQYBI', a second link connected to said rock- REFERENCES CI'IIEI) 16V?! afipomt m ahnement wi fulcruim' The following references are of record in the axis of; said clampriootwhen, said thread-trimfile this patent,

merand -nipper device is. in closed position, and I operating mechanism connected to said second 5 UNITED STATES PATENTS link. Number Name Date DARWIN SMITH- 1,066,862 Sullivan July 8, 191 3 HAROLD C. FAULKNER.

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