US2720853A - Stitch control for sewing machines - Google Patents

Description

OCt. 18, 1955 W. w. ARTzT 2,720,853

STITCH CONTROL FOR SEWING MACHINES Filed DeC. 3l, 1952 2 Sheets-Sheet l INVENTOR. WML/AM h( RTZT Oct. 18, 1955 W. W. ARTzT 2,720,853

STITCH CONTROL F'OR SEWING MACHINES Filed Dec. 5l, 1952 2 Sheets-Sheet 2 IN VEN TOR.

A//LL mM M/qrzr (AZTORZEK j United States Patent tiice 2,720,853 Patented Oct. 18, 1955 2,720,853 STITCH CoNIRc-L FOR SEWING MACHXNES William W. Artzt, New York, N. Y., assigner, by mesne assignments, to Trimless, Inc., New York, N. Y., a corporation of New York Application December 31, 1952, Serial No. 328,995

Claims. (Cl. 112-210) The present invention relates generally to sewing machines, and is particularly directed to a stitch control for sewing machines, especially for overedging machines of the type shown in the patent granted to Normal V. Christensen and Frederick F. Zeier, March 25, 1930, No. 1,751,508.

In overedging machines of the kind referred to above, the fabric is fed across a work support by a feeding mechanism which is of the four motion type, and includes both a main and an auxiliary feed dog, which preferably have differential feeding movements imparted thereto. The material being stitched is held on the work support by a presser foot which is suitably mounted for engagement or disengagement of the material at the will of the operator. The mechanism for forming overedge stitches includes a needle which preferably reciprocates in a line inclined to the plane of the work support, a looper disposed below the work support and cooperating with the needle, and an overedge looper cooperating with the lower looper and the needle, both the lower and overedge loopers preferably being of the thread carrying type. The fabric is preferably trimmed prior to the stitching operation, and such trimming may be accomplished by a stationary trimming blade carried by the work support and a movable trimming blade which is carried by an oscillatable arm mounted above the work support. The feeding mechanism, needle, loopers and trimming arrangement are all operated by a single actuating crankshaft disposed above the plane of the Work support. This shaft is preferably mounted in bearings carried by a standard which is mounted on the bed of the machine at a location to one side of the line of feed and in back of the stitching point so that adequate clearance is provided for the material being stitched. The shaft extends normal to the line of reciprocation of the needle and lies in a Vertical plane which is inclined laterally relative to the vertical plane containing the line of feed, while the axis of rotation of the shaft is inclined relative to the plane of the work support.

Overedging machines of the kind described generally above provide stitching along an edge of the material which includes stitches formed by the needle thread adjacent and parallel to the edge and loops of the looper thread carried around the trimmed edge of the fabric and passed through the needle thread stitches above and below the fabric so that the overedge stitches envelope the trimmed edge of the fabric. ln order to prevent unravellin g of such overedge stitching, it has been the usual practice to reverse the direction of the feeding movement at the end of aline of stitching thereby forming stitches back over the end portion of the line of stitching, and then to tack the loose ends of the stitches formed in the reverse direction. However, this usual procedure requires the operator to stop the machine, reverse the direction of feed and then form several additional stitches back over the line of stitching. These operations are time consuming, and very often ineffective, unless the threads are tacked by hand.

Accordingly, it is an object of the present invention to provide an overedging machine of the described character which is adapted to secure or lock the overedge stitches at the end of a line of stitching in a simple and convenient manner.

Another object is to provide an overedging machine of the described character which is constructed so that the end of a line of stitching may be secured or locked without requiring any reversal in the direction of feed or halt in the operation of the machine.

Another object is to provide attachments for an overedging machine of the described character which adapt such machine so that it is able to lock the ends of lines of overedge stitching, and wherein such attachments may be installed with a minimum of alteration of the existing machine and without interfering with the normal operation of the overedging machine.

In accordance With the present invention, the foregoing objects are accomplished by providing attachments for an overedging machine which operate intermittently, and at the will of the operator, to greatly reduce the spacing between successive overedge stitches so that these stitches overlap each other and prevent unravelling of the line of stitching. Such attachments act to vary the throw of both the auxiliary and main feed dogs during the continuous operation of the feeding mechanism.

In order that the invention may be readily understood, a preferred embodiment thereof will be described in detail in connection with the accompanying drawings forming a part hereof, and wherein:

Fig. l is a side elevational view, partly broken away and in section, of an overedging machine having attachments thereon constructed in accordance with an embodiment of the present invention;

Fig. 2 is a fragmentary sectional view taken along line 2 2 of Fig. 1 and on an enlarged scale;

Fig. 3 is a perspective View of the feeding mechanism and attachments shown in the overedging machine of Fig. l;

Fig. 4 is a perspective view of control mechanism for operating the attachments illustrated in Figs. 1 and 3, but on a smaller scale;

Fig. 5 is a fragmentary sectional view taken along the line 5-5 of Fig. l and on an enlarged scale; and

Fig. 6 is a plan view of a piece of fabric having overedge stitching extending along an edge thereof and secured at the end in accordance with the present invention.

Referring to the drawings in detail, and initially to Fig. 1 thereof, an overedging machine is there illustrated and includes attachments embodying the present invention. The overedging machine is shown only to the extent that is necessary for a complete understanding of the invention, and some of the parts thereof which are not related to the invention have been omitted for the purpose of clarity. The illustrated overedging machine includes a substantially rectangular bed 10 which may be suitably secured to a work table and has a standard 12 etxending upwardly from the rear portion thereof. The standard 12, at its upper end, supports a housing 14 extending forwardly therefrom and providing bearings for the opposite ends of a crankshaft 16. The crankshaft 16 is mounted so that its axis of rotation is inclined from the horizontal and lies in a vertical plane which is inclined laterally with respect to the sides of the bed 10. A grooved wheel or pulley 18 is secured on the rear end of the crankshaft 16 projecting from the housing 14 and is adapted to receive a driving belt (not shown) for effecting rotation of the crankshaft. The bed 10 carries a horizontal work support 20 which is formed with a suitable opening 22 at the stitching location to permit a main feed dog 24 and an auxiliary feed dog 26 to extend therethrough for engagement with the under surface of material on the work support 20. The main feed dog 24 is securely mounted at the free end of a support arm 28, while the auxiliary feed dog 26 is carried by a hlockll which is supported on the arm 28 adjacent the free end of the latter and is reciprocatable longitudinally relative to the support arm 28. In order to supportV the block 30 on the arm 2 8, the latter is formed with laterally extending, bored bosses 32 and 34 at spaced locations and through which a support rod 36 is longitudinally slidaole.V The block 30 is secured on an end .of the rod 36, and the latter is provided, intermediate its ends, with a cross-head 38 to which one end of a connecting rod 40 is pivotally attached, as seen in Figs. l and 3. Y Y Y A feed rocker assembly, generally identified by the reference numeral 42, is disposed` adjacent the rear of the hed'lO-below the level of the work support 20 and includes a feed Vrocker 44 Vwhich is oscillatable on a horizontal sha-ft 46 suitably mounted on the bed. The feed rocker 44 is Vformed with axially spaced, radially extending arms or lugs 48 and 50 (Figf) between which a shaft 52 extends parallel to the shaft 46 and spaced from the latter. The arm 28, at its end remote from the feed dogs 24 and 26, is laterally widened, as at 54 (Fig. 3) and formed with a through-bore (not shown) to receive the shaft 52 and thereby rockably mount the support arm 28 on the feed rocker assembly 42. Further, a plate 56 is secured to the outside of the lug 48 and is formed with an arcuate slot 58.l The endy of connecting rod 40 remote from the cross-head 38 rotatably carries a threaded bolt 60 whichv extends through the slot 58 and has a nut 62 thereon for pivotally securing the-related end of rod 40 to plate 56 in an adjusted position along the slot 58. Thus, the radialY distance of the point of attachment of rod 40 tothe plate 56 from the rocking-axis of the feed rocker 44 may be adjusted within the limits defined by the ends of the slot 58'. Rocking of the feed Vrocker 44 will produce substantially linear movement of the Vmain dog 24 andtheauxili-ary dog 26.Y The relationship between the linear movements of the dogs 24 and 26 for each oscillation of the rocker 44 depends upon the relative distances of the shaft 52 and the bolt 60 from the rocking axis or shaft 46, and the differential movement of the dogs may be regulated by adjusting the fixed-position of the bolt 60 along the slot 58.

The mechanism for rocking the feed rocker 44 includes a radial arm 64 extending vforwardly from the latter` and formed with an arcuate slot 66. An eccentric 68 is provided on'theY crankshaft 16, anda split bearing member 70V engages around-the eccentric 68, and is 'secured to the upper end of a connecting rod-72. The lower end of the connecting rod 72 is attached to the yarm 64k by structure embodying the present invention and hereinafter described in detail so that, as the crankshaft 16 is rotated, the arm 64 and rocker 44 are angularly displaced, with the extent of such angular displacement depending uponthe location ofthe point of attachment of therod 72 to the arm 64.

The crankshaft 16 has other eccentrics thereon (not shown) for actuating a connecting rod 74 which .operates the lower looper mechanism (not shown)y and for actuat-V ing a connecting rod '7.6 which operates the upper `looper mechanism (not shovmf). The crankshaft has still another ecentric lthereon (not shown) for actuating a connecting rod 78 which is pivotally attached to a central portion of a lever 80. The lever 80, at its rear end, is pivotally mounted'on a suitable pivot 82, and at its front end carries a movable trimming blade 84 which cooperates with a suitable stationary blade (notf shown) for trimming the edge of the material at the stitching location. A link 3.6Y is pivotally connected at itsv opposite endstothe lever 8.0., `as at 8.8, and to the ann 28' as at SN),Y .so that the actuation of rod 78 by the related; eccentric causes operation, of the ,trimming blade 84 and up .and down meverneintV of the feed dogszd. and 2.6. Thevariousmoyements of the feed dogs are synchronized so that `.the dogs are raised during their feedingy stroke (tothe -left as viewed in Fig. l) and are lowered, .out of contact-with the ma- 4 terial on the Work support, during the return stroke (to. the right as viewed in Fig. l).

Further, the overedging machine includes a needle 92 supported for reciprocation along a line which is normal to the axis of rotation of crankshaft 16 and inclined relative to the plane of the work support 20. A crank arm 94 is secured to the front end of the crankshaft and is operatively connected to the needle supporting structure A96 by a suitable link 98, so that rotation of the Ycrankshaft also causes reciprocation of the needle. Finally, machines of the kind referred to herein include a presser foot 100 which is mounted ou the forward end of a support lever 102. The lever 102 is mounted for rocking movement in response to manipulation by the operator so that the foot 100 either holds the material down on the work support 26 or releases the material for removal from the machine.

Gveredging machines conforming to the above general edge of a piece of fabric. As seen in Fig. 6,y suchV overedge stitching includes a line of stitching 104 producedV by the needle thread and extending adjacent and parallel to the edge 106 of the fabric 108, and overedge loops 1101 provided by the looper thread which extend around the edge 106 of the fabric and pass through the needle thread stitches 104 above and below the fabric. The portion A of the line of stitching in Fig. formed during the normal operation of the machine, for example', fourteen stitches per inch. In accordance with the present invention, unravelling of' a line of overedge stitching is prevented by crowding the stitches at the terminal portion of the line, so that the successive stitches overlap, as in the portion B on Fig. 6. Such crowdingV of the stitches, for example, thirty-two stitches per inch, and the consequent overlapping. of the successive stitches effectively prevents unravelling of the overedge stitchingV and eliminates the necessity of reversingthe direction of the feed to sewback over the end portion as well as the hand tacking ofthe loose ends .of thethread, which meas: ures were heretofore resorted to for the purpose of pre: venting unravelling.

In order that the stitches may be conveniently crowded together and overlapped at the endportion of a. lineof lower end of rod 72. The pinV member 112 extends loose.-

ly through arcuate slot 66 formed in the. arm 6 4 and has a rim 118 to engage the rod 72. The pin member 112 has a reducedzdiarneter threaded portion 12,0 extending axiallytherefrom* in the. direction away from .ball 114V and the lengthV of thepin. member from the 118 to the radial shoulder at the. beginning of Portion 1.2.0 is only slightly greater than the thickness of the arm 64. A plate 122 having a central: aperture is disposed on the threaded portion 12.0 with the arm. 64 being arranged between the plate 122 andthe rim 118,V and a guide pin .124 is formed with threaded bore to receive the threaded portion 120 of the pin member and to hold the plate 122 against theshonlder` of theA latter. Thus, the pin member Y1.12 is slidable .along the slot 66 to vary the distance between the point of attach,-Y rnent of the rod 7 2 to the arm 6 4 and the axis'of rotation of the feed rocker ,assembly 42 as defined by the shaft 46;

Assuming that the longitudinal reciprocation of the. rod 72as determined by the eccentric 68, is always con: stant, it is apparent that the angular displacement of the' feed rocker assembly 42 and the-length of .the stroke of the feed dogs A24 and 26 increases asY the-pinmember 112 6 represents the stitching v,

side of arm 6 4 facing toward the is moved along slot 66 in the direction toward the shaft 46, and that the angular displacement of assembly 42 and the length of the stroke of dogs 24 and 26 decreases as the pin member 112 is moved along slot 66 away from the shaft 46. Since the number of stitches per inch formed in the material varies inversely with respect to the length of stroke of the dogs 24 and 26, it is also apparent that the pin member 112 has to be moved away from the axis of shaft 46, to increase the number of stitches formed per unit length along the line of stitching, and toward the axis of shaft 46 to decrease the number of stitches per unit length.

In order to effect the necessary movements of the pin member 112 along the arcuate slot 66 without interrupting the normal operation of the machine, the present invention provides a bell-crank member (Figs. l and 3) having two right-angularly related arms 126 and 128. This bell-crank member is rockably mounted at the junction of the arms 126 and 128 for pivoting about an axis above and parallel to the axis of shaft 46. Such rockable mounting of the bell-crank member is preferably achieved by an angle member 130 having one arm formed with a slot 132 to receive bolts threaded into the back of the standard 12. The other, or forwardly extending arm, of the angle member 130 is formed with a tapped hole (not shown), adjacent its front end, to receive the threaded end of a pivot bolt 134 on which the bell-crank member is pivoted. The arm 128 of the bell-crank extends downwardly from the pivot 134 and has a forked lower end to deiine a downwardly opening elongated slot 136 into which the pin 124 slidably extends. hus, as the bell-crank member is rocked on its pivot 134, the arm 128 acts to displace the pin member 112 within the slot 66. The other arm 126 of the bellcrank member extends rearwardly from the pivot 134 beyond the rear edge of the bed 10, and at its rear end is attached to an operating chain 138 which extends downwardly therefrom. Intermediate its ends, the arm 126 is connected to a tension spring 140 which is in turn secured to an anchoring screw 142 on the standard 12. The spring 140 continuously urges the bell-crank member to rock in the direction increasing the stroke of the feed dogs 24 and 26 or decreasing the number of stitches per unit length, while a downward pull exerted on the chain 138 to overcome the force of the spring 140 causes the bell-crank member to rock in the opposite direction for increasing the number of stitches per unit length.

In order to control the number of stitches per unit length formed during normal operation of the overedging machine and during the finishing-off or locking of a line of stitching, a stop assembly is associated with the arm 126 of the bell-crank member and includes an upstanding member 144 having an elongated slot 146 therein and provided with a mounting tlange 148 at its lower end for attachment to the back of the bed (Fig. l) in a position so that the member 144 is adjacent to the arm 126 (Figs. 3 and 5). Upper and lower stops 150 and 152, respectively, are adjustably mounted on the member 144 to limit the swinging of arm 126 in the opposite directions. Each of the stops 150 and 152 includes a bolt 154 (Fig. 5) extending slidably through the slot 146 and having a preferably semi-circular head 156 at one side of member 144 projecting into the path of travel of the arm 126. The other end of bolt 154 is threaded to receive a nut 158 which clamps the related stop in adjusted position on member 144. The upper stop 150 is disposed above arm 126 and limits the movement of the bell-crank member in the direction urged by the spring 140, while the lower stop 152 is disposed below arm 126 and limits the swinging of the bell-crank member in the direction caused by the exertion of a downward pull on the chain 138. Thus, the position of stop 150 determines the number of stitches per unit length during normal operation of the overedging machine, while the stop 152 determines the number of stitches per unit length during the completion of a line of stitching, when the stitches are being crowded together to eiect locking of the stitching.

It is apparent that the bell- crank member 126, 128 may be rocked during the operation of the machine to change the number of stitches per unit length at the will of the operator and that no reduction is necessary in the speed at which the machine operates for the purpose of effecting such change.

In order to permit the operator to change the machine from its normal operating condition to that in which the stitches are crowded together for locking the line of stitching and without requiring the use of the operators hands, which can continue to guide the material being stitched, a control assembly is provided, as illustrated in Fig. 4, for actuation by the operators knee. This control assembly includes a jack shaft 160 which is rotatably journalled in a suitable bracket 162 which may be mounted below the table or bench (not shown) supporting the overedging machine. One end of the `jack shaft 160 extends rearwardly of the supporting table and has a radial arm 164 secured thereto. The arm 164 is formed with spaced openings 166 so that the chain 138, extending downwardly from the arm 126 of the bellcrank member, can be attached to the arm 164 by opening the end link of the chain and passing it through one end of the openings 166. A bent rod 168 is secured to the front end of the jack shaft 160 and extends generally downward from the latter. Finally, a curved plate 170 is secured to the lower end portion of the rod 168 and is preferably adjustable along the latter for positioning adjacent the outside of one of the operators knees. When the operator presses with a knee against the plate 170 to cause the shaft 160 to rock in the clockwise direction, as viewed in Fig. 4, the arm 164 pulls downwardly on the chain 138 to effect rocking of the bell- crank member 126, 128, in opposition to the force exerted by the spring 140, until the ann 126 of the bell-crank member engages the lower stop 152. When the arm 126' engages the stop 152, the arm 128 of the bell-crank member has shifted the connection between the rod 72 and the arm 64 of the feed rocker assembly to a position remote from the axis of shaft 46 so that the strokes of the main feed dog 24 and of the auxiliary feed dog 26 are shortened to crowd the successive stitches one on top of the other. When the operator relaxes the knee pressure against the plate 170, the spring acts to return the arm 126 to its normal position against the upper stop and the integral arm 128 then moves the pin member 112, connecting the arm 64 of the feed rocker to the connecting rod, in the direction toward the axis of shaft 46 for increasing the strokes of the main and auxiliary feed dogs so that the overedging machine is again conditioned for forming stitches at the normal spacing, as determined by the position of the adjustable stop 150.

From the foregoing it is apparent that the present invention provides attachments for an overedging machine of the described character which adapt the machine to locking the terminal portion of a line of stitching, and that the required attachments may be added to the overedging machine without requiring excessive alteration of the machine and without interfering, in any way, with the normal operation of the machine. Further, the attachments embodying this invention are simple and relatively inexpensive to produce and install on the overedging machine, and are operative to change the condition of the machine for iinishing and locking a line of stitching without interrupting the operation of the machine.

While a particular embodiment of the invention has been shown and described, it is to be understood that the invention is not limited to this specic embodiment, and that various changes and modifications may be effected therein by one skilled in the art without departing 7 from-the scopeor spirit of the 'mvention as dened in the appended claims.

What Vis claimed is: Y Y l. In'dan overedging machine; the combination of a Y rotated actuating crankshaft, a connecting rod extending from said crankshaft and longitudinally reciprocated by rotation ofthe latter,` a feed rocker mounted for rocking about xed axis and having a radially extending army Vformed with an elongated slot therein, a pin member carried by said connecting rod and slidable in said slot for attaching said' connecting rod to'V said radially extending armwhile being movable alongfthe latter to vary the angular displacement of said feed rocker caused by a predetermined reciprocation of said connecting rod, atv least onelfeeding dog, means connecting said feeding dog to to said rockin-gi axisof the feed rocker, one of said arms ofV the bellfcrank member having a forked end receivingVV said pinrmember to cause displacement of said pin member along said elongated slot in response to rocking of the bell-crank` membe'rf so that, when said pin member is posi-l tioned relatively close tol the rocking axis of said feed rocker, anormal number of stitches are formed per unit length,I and, when said pin member is positioned relatively remote; fromy said rocking axis, the stitches are crowded together and overlapped for locking the line of stitches; meansv normally urging saidbell-crank member to locate said pin member relatively` close to said rocking axis, and means: adapted for actuation by the operator of the maehine and operative to cause said bell-crank member to-llcateithe pin member at a position remote from said y rocking axis. Y

Ixran overedging machine; the combination accord'- ingto claim' 1;v further comprising means cooperating with said bell-crank member to limit the rocking of the latter in opposite directions for' determining the maximum and minimum numbers of stitches formed per unit lengthV a-l'ong the` line of stitches.

3. In anoveredging machine; the combination Vaccord-4 ing to claim 1, wherein said means normally urging the bell-crank member tolocate the pin member relatively close to the rocking axis of the feed rocker includes a spring member connected at one end to the other arm of said bell-crank member, and'xed anchor means connected' to the other end of said spring member so Ythat the latter yielda-bly urges said bell-crank member to rock in one direction.

4. In an overedging machine; the-combination according to claim V3; wherein said means adapted for actuation' the machine includes aI rockable by the operator of member for actuation by the operator, and transmission means extending between' said rockable member and said other arm' of the bell-crankA member to exert a force on said other arm in opposition to Vsaid spring member whenAV K said rockable member is actuatedr by the/operator.V

5.l In an overedging` machine; the combination accord-1 ing to claim 4; and further comprising meansV for limiting the rocking of said bell-crank in opposite directions, said limiting meansV including a stop support disposed ad-r jaeent'said other arm of theVbell-crank member andy ex# tending substantially normal to said other arm, and twostop membersA adjustableV along said stop support and ex` Vtend-ing intothe path-V of Vtravel of said other arm VatV opposite sides ofthe latter. Y

References Cited in the le of thispatent UNITED STATES PATENTS y Weis July 34 1911.7

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