US3749041A

US3749041A - Thread cutting and wiping mechanism for group stitch sewing machine

Info

Publication number: US3749041A
Application number: US00203632A
Authority: US
Inventors: R Bowin
Original assignee: Union Special Machine Co
Current assignee: Union Special Machine Co
Priority date: 1971-12-01
Filing date: 1971-12-01
Publication date: 1973-07-31
Anticipated expiration: 1990-07-31
Also published as: GB1412266A; DE2259059A1; GB1412267A

Abstract

Group stitch sewing machine equipped to form tacks made of single thread chain (type 101) stitches. A thread severing blade is fixed in the needle receiving aperture of the tacking clamp and is provided with a gravity actuated sheath to expose cutting edge of knife only when tacking clamp starts to rise to open position at end of each group stitching operation. Thread extending over blade is severed to leave upwardly protruding thread tail extending from tack by which tack may be readily stripped from work after tack has served intended purpose. Thread wiper is provided to cooperate with conventional thread take up mechanism to remove other severed end of thread from the work piece and to position severed end for initiation of next group stitching operation. Thread wiper is freely pivoted and is actuated by contact of cam surfaces thereon with rigid rod fixed to and movable with clamp opening means. Action of wiper is initiated by opening movement of clamp and major portion of remaining movement of wiper is result of kinetic forces and gravity, as limited by contours of said cam surfaces.

Description

United States Patent [1 1 Bowin THREAD CUTTING AND WIPING MECHANISM FOR GROUP STITCH SEWING MACHINE [75] Inventor: Richard E. Bowin, Berkeley, Calif.

[73] Assignee: Union Special Machine Company,

I Chicago, Ill.

[22] Filed. Dec. 1, 1971 [21] Appl. No.: 203,632

[52] US. Cl. 112/252 [51] Int. Cl D05b 65/06 [58] Field of Search 112/252 [56] References Cited UNITED STATES PATENTS 3,498,243 3/1970 Aoyama 112/252 1,983,555 12/1934 McCann 112/252 X 2,354,559 7/1944 Thornton 112/252 X 2,889,793 6/1959 Mueller et a1. 112/252 X 3,584,589 6/1971 Pirello 112/252 2,849,974 9/1958 Tischler et al. 112/252 X Primary ExaminerWerner H. Schroeder Attorney-James D. Bock [57] ABSTRACT Group stitch sewing machine equipped to form tacks made of single thread chain (type 101) stitches. A thread severing blade is fixed in the needle receiving aperture of the tacking clamp and is provided with a gravity actuated sheath to expose cutting edge of knife only when tacking clamp starts to rise to open position at end of each groupstitching operation. Thread extending over blade is severed to leave upwardly protruding thread tail extending from tack by which tack may be readily stripped from work after tack has served intended purpose. Thread wiper is provided to cooperate with conventional thread take up mechanism to remove other severed end of thread from the work piece and to position severed end for initiation of next group stitching operation. Thread wiper is freely pivoted and is actuated by contact of cam surfaces thereon with rigid rod fixed to and movable with clamp opening means. Action of wiper is initiated by opening movement of clamp and major portion of remaining movement of wiper is result of kinetic forces and gravity, as limited by contours of said cam surfaces.

10 Claims, 14 Drawing Figures l 52 82 5O 68 I6 PATENIEL JUL 3 1 ms SHEET 1 BF 6 N GI IVE

PATENIEDJULBI m SHEET 3 OF 6 FIG.7

FIG.8

PATENIEDJULIH I915 3.749.041

saw u or 6 FIG.9

FIG. IO

THREAD CUTTING AND WIPING MECHANISM FOR GROUP STITCH SEWING MACHINE BACKGROUND or INVENTION Sewing machines of group stitch type such as button sewing maciines, button holers and trackers are well known and normally share common features such as program cams for vibrating the clamped work piece in one or more generally horizontal coordinate directions relative to the vertical axis of needle vibration to automatically form a specific number of overlapping stitches in the desired direction or directions each time the machine is started, the machine stopping automatically at, the end of each group. stitching operation. The particular machine chosen for illustration herein is a tacker with thread severing and thread wiping mechanism appropriate therefor but otherwise similar to the button sewing machines disclosed in ULS. Pat. No. 3,509,838 to Bowin and. US. Pat. No. 2,609,773: to Nelson. Additional US. Patents which are pertinent to the. general type of machine herein involved are U.S. Pat. Nos, 2,645,192 to. Ketterer and 2,645,192 to McCann.

BRIEF DESCRIPTION OF INVENTION The. thread severing and, thread. wiping mechanisms. shownincertainofthe U.S. Patentslisted aboveare typical of the mechanisms heretofore provided and each. requires specially. provided movable parts. or trains of movable parts for their operation. The present invention substantially avoidsthe provision-ofspecific movable parts for. such devices inasmuch as boththe severing means and th ead wiper are arrangedfto be. moved substantially directly bypartswhich are necessarily movedinthe closingand opening of the work holding means. The severing'device is afixed blade. secured inthe needle receivingapertureof the tacking: clamp and it is providedwith a sheath-movable to shield the blade by contact with the clamped work and movable to unshield the blade by gravity when the tacking clamp first moves away from the work at the I end of .a. tack forming, group stitchingoperation. The

thread wiper is freely pivoted about a center fixed on the machine, is weighted so as to tend to swing by gravity to a predeterminedposition relative to the needle, and is provided with cam. means activated by a simple rigid actuating rod fixed to the-clamp opening mechanism to swing the, wiper to various desired positions. The movements of the wiper at the end of a group stitching operation are initiated as a sharply accelerated cam-imparted motion and the subsequent thread wiping and returning motions are due to kinetic forces, including momentum and rebound, and gravity, the various positions of reboundor rest being established by contact between the actuating rod and cam-surfaces provided on the wiper. The severing device and the wiper of the present invention cooperate in a specifically novel combination in the tack forming version of a group stitch machine as disclosed herein, although each is capableof use in other specific combinations in sewing machines.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view with parts broken away, showing an embodiment of the present invention. in a sewing machine of the group stitch type, more specifically, a tacker;

FIG. 2 is a front elevational view of the machine shown in FIG. 1;

FIG. 3 is a plan view, with parts broken away and parts in section of the machine shown in FIG. 1;

FIG. 4 is a fragmentary vertical sectional view taken along the line 4-4 in FIG. 3;

FIG. 5 is a fragmentary sectional view taken along the line 5-5 in FIG. 3;

FIG. 6 is a view similar to FIG. 5 but showing parts in positions different from FIG. 5;

FIGS. 7, 9, 11 and 13 are fragmentary front elevational views illustrating sequential operation of the thread severing device and thread wiper embodying the present invention; and

FIGS. 8, 10, 12 and 14 are fragmentary side elevational views otherwise similar to and corresponding respectively with FIGS. 7, 9, l1 and 113.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The machine illustrated in the drawings which em- I bodies the present invention is a group stitching machine of the general type disclosed in US. Patent to Nelson No. 2,609,773 granted Sept. 9, 1962 and in US. Pat. No. to Bowin 3,509,838 granted May 5, 1970. The type of machine shown in each of Nelson and- Bowin is a button sewing machine which includes button positioning and work clamping means which is moved into clamping position and lifted away from suchposition at the beginning and end respectively of a groupstitching operation in which a predetermined number of stitches is formed to secure a button to a work piece. The machine illustrated herein differs from such button sewing machines primarily in the fact that the clamping device is arranged to be moved into clamping position wherein it holds two or more layers of work in a superimposed relationship in which they are to be tacked together by a predetermined number of stitches. Thus, the clamping device in the machine disclosed herein does not include the special equipment required for the positioning and holding of a button against a work piece. Otherwise the apparatus for lowering and raising the clamping device and for vibrating the clamped work relative to the vertical axis in which the needle travels, in two horizontal coordinate directions may be the same as that disclosed in said Nelson and Bowin patents. Similarly, the mechanism for predetermining the number of stitches which may be formed in one or the other or both of these coordinate directions is the same as that disclosed in said patents. Accordingly, the showing of the machine herein is greatly simplified and only certain key parts will be specifically referred to inasmuch as reference is herein made to said Nelson and Bowin patents for disclosure of details of this type of sewing machine.

It also should be pointed out that the thread cutting and thread wiping mechanisms shown in said Nelson and Bowin patents are not shown in the present disclosure inasmuch as corresponding mechanisms of substantially different constructions are disclosed herein and form parts of the present invention.

Referring now to the drawings, the machine has an enclosing frame structure, best shown in FIGS. 1 and 2, which includes a vertical standard It having a base portion 11 arranged for mounting upon suitable support (not shown). Extending horizontally and, for the purposes of this description, forwardly from the base portion 11 is a work supporting arm 12. Above the latter and extending outwardly and forwardly from the vertical standard of the frame is a overhanging arm 13 which, at its forward end, has a head 14 in which is mounted a vertically reciprocable needle bar 15 adapted to carry a needle 16 for movement through the work supported upon the arm 12. As shown in FIG. 2 the machine is also provided with a looper 17 of one conventional type which cooperates with needle 16 in the formation of stitches. It will be understood that suitable connections are provided on the frame of machine for driving the needle bar 15 and rotating the looper 17 in properly timed relation for forming the desired stitches, and such mechanism not shown in full detail herein since it is all well known in the art. However, part of the driving mechanism just referred to which is shown in FIG. 1 is the main drive shaft 18 and a stop motion controlling rock shaft 19 both mounted in the base 11 of the machine and extending generally transversely to the axis of the

arms

12 and 13.

Referring next to FIG. 3, wherein the major portion of the vertical standard 10 and all of the upper arm 13 has been omitted, it will be observed that main drive shaft 18 is extended outwardly and carries a drive pulley 20 selectively connected with shaft 18 by a stop motion 21, the latter being provided to start and stop the machine for each group stitching operation. A looper shaft 22 is driven by shaft 18 and, in turn drives a cam shaft 24 to rotate ca'ms 26 and 28 for the purpose of vibrating the work supporting and clamping means, indicated generally at 29 in the two coordinate directions mentioned above. As disclosed in full detail in said Nelson patent the work supporting and clamping means 29 is pivoted about a pivot screw 30 movable to a selection of positions to select the length of stitches made while the work supporting and clamping means 29 is being vibrated in one of the coordinate directions mentioned above by one of the

cams

26 or 28. Also, as shown in full detail in said Nelson patent the work supporting means 29 is vibrated in the other coordinate direction which is parallel with the axis of the

arms

12 and 13, to form stitches of selected length in this other coordinate direction when so desired.

The work supporting and clamping means 29 includes a lever 32 which is pivoted upon the pivot screw 30 mentioned above, and the lever 32 has secured at the forward end thereof a feedplate 34 which, as shown in FIG. 1, extends forwardly beyond the vertical axis of the needle 16. As shown in FIG. 3 the feedplate 34 is provided with an aperture 36 through which the needle reciprocates vertically incident to the formation of stitches. The work supporting and clamping device 29 also includes a bracket 38 which, as shown in FIG. 1, has secured to the forward end thereof a tacking clamp 40 which also extends forwardly beyond the vertical axis in which the needle 16 travels. Referring now to FIG. 3 the tacking clamp 40 is provided with an aperture 42 of generally square configuration and corresponding with the aperture 36 in 'feedplate 34. The bracket 38 is provided at its rearward end with depending lugs 44 which, as shown in FIG. 3, are spaced laterally and are pivoted upon a pivot pin 46 supported upon the lever 32. As will be apparent, the bracket 38 and tacking clamp 40 will move with the lever 32 and feedplate 34 in the vibrations in both coordinate directions of the work supporting and clamping assembly 29. However, the bracket 38 with the tacking clamp 40 may be swung about the axis of pivot pin 46 to move the tacking clamp 40 downwardly into engagement with work resting upon the feedplate 34 and upwardly out of clamping engagement with such work. The tacking clamp is urged down against the work by an adjustable spring 47.

The bracket 38 which carries clamp 40 is provided with a rod 48 having a horizontal and downwardly bent arm as shown in FIG. 1, the rod 48 being adjustably fixed to bracket 38 in a set-screw socket 50 formed on the latter. The arm of rod 48 is adapted to be engaged by a laterally extending arm 52 formed on a rod 54 which depends from a clamp lifting lever 56 pivoted at 58 to the arm 13 of the sewing machine. As is the case in said Bowin patent the clamp lifting lever 56 is connected with suitable mechanism for automatically raising the tacking clamp 40 from the work at the end of a group stitching operation and lowering the same into clamping position when the operator initiates the next group stitching operation. Such mechanism includes an eccentric 60, shown in FIG. 1, fixed upon the main drive shaft 18. The eccentric 60 is effective to rock a rocking member 62 on each revolution of the shaft 18. The rocking motion of rocking member 62 is transmitted by a link 64 to the rearward end of clamp lifting lever 56 only at the end of each group stitching operation. The rocking member 62 has a lateral extension 63 and link 64 has a notch 65. Since in FIG. 1 the parts are shown in the positions assumed during a group stitching operation with tacking clamp 40 in clamping position the lateral extension 63 on rocking member 62 will not engage the notch 65 in link 64 whereby the rocking member 62 rocks idly during the stitching operation. At the end of the group stitching operation the stop motion controlling rock shaft 19 rocks in a clockwise direction (under control of a single or fractional revolution cam not shown herein but clearly shown in said Bowin patent). This rocking of shaft 19 initiates functioning of the stop motion 21 (FIG. 3) to stop main drive shaft 18 ina specific position at the end of the group stitching operation. This rocking of shaft 19 also pulls a freely pivoted link 66 towards the left as viewed in FIG. 1. The link 66 is freely pivoted to the lower end of link 64 which thus is swung in a clockwise direction to engage the notch 65 therein with extension 63 of rocking member 62 whereby, as the main drive shaft moves toward its sotpped position the link 64 is pulled downwardly to open the tacking clamp 40. In the stopped position the notch 65 and extension 63 remain engaged to hold the tacking clamp in raised or open position. When the operator presses the foot treadle or other device for starting a new group stitching operation the rock shaft 19 is rocked counterclockwise as viewed in FIG. 1 to engage the stop motion 21 and also to push on link 66 to disengage notch 65 in link 64 from the lateral extension 63 of rocking member 62. Such disengagement frees the link 64 to rise and tacking clamp 40 thereupon will be moved into yielding clamping engagement with the work by operation of spring From the foregoing description of the means for raising and lowering the tacking clamp 40 it will be apparent that the raising of the clamp 40 to open position occurs during one-half revolution of the main drive shaft 18 just before the latter is abruptly stopped. Therefore the upward movement of tacking clamp 40 towards open position is very rapid and, as will be explained below the rapidity of such movement is taken advantage of in the operation of the thread severing and thread wiping devices of the present invention.

The thread severing and thread wiping devices which the present invention provides for cooperation with group stitching apparatus of the general type represented by the machine just described are shown in their general disposition with respect to the machine in FIGS. 1 through 3. The detailed construction and operation thereof is illustrated in FIGS. 4 through 14. The thread wiper is generally identified at 68 in FIG. l, and it is freely pivoted upon and depends from a suitably shouldered pivot screw 70 secured in a lug 72 fixed on the head 14. The center of the pivot screw 70 is indicated at 74 in FIG. 2 and in those of the remaining figures wherein the pivot screw 70 lies directly behind the needle bar 15. The position of the thread wiper 68 illustrated in FIG. 2 is that assumed during the active stitch forming portion of a group stitching operation. In such position the thread engaging arm 76 of wiper 68 is disposed a substantial distance laterally from the axis of vibration of the needle 16.

As will be explained hereinbelow the position of the thread wiper 68 shown in FIG. 2 is positively established, that is the wiper is locked in that position by the mechanism which is provided for movement of the thread wiper 68 when such is desired. The mechanism for locking and moving the thread wiper 68 is shown generally in FIGS. 1 and 2. Thus, referring first to FIG. 2 it will be observed that the thread wiper 68 is provided with a generally triangular shaped opening 78 formed in the body of the wiper in an area lying below the center point 74. The forward end of an actuating rod 82 extends from the rear of wiper 68 into the opening 78. Referring now to FIG. 1 it will be noted that the actuating rod 82 is adjustably secured by screw-clamp block 84 upon the vertically movable rod 54 which, as described above, is a part of the mechanism which raises the tacking clamp 40 at the end of a group stitching operation. Thus as the actuating rod 82 moves up and down with the clamp operating mechanism the forward end portion thereof is caused to move inside the opening 78 to impart the desired motions to the wiper.

Also in FIGS. I, 2 and 3 the thread severing device generally indicated at 86 is shown positioned in the rectangular needle-receiving opening 42 formed in the tacking clamp 40. As will be more fully described hereinbelow the thread severing device 86 is so arranged as to sever the needle thread as an incident to the ending of the group stitching operation in a simple and efiective manner immediately as the tacking clamp 40 starts to rise from clamping position and the needle starts to rise. Thereafter, as the clamp 40 and needle 16 continue to rise the thread wiper 68 is actuated to swing arm 76 thereof beneath the needle point to perform its function in the removal of severed needle thread from the work and positioning of the needle thread for the next group stitching operation. The thread severing device consists essentially of a fixed knife blade secured to the tacking clamp and provided with a movable sheath.

Referring now to FIGS. 4, 5 and 6 a preferred embodiment of the thread severing device 86 of the present invention is shown in detail. Thus, a relatively narrow flat knife blade 88 is shown standing vertically on edge and fixed in the opening 42 of tacking clamp 40 so as to extend across the opening substantially centrally of the opening. For example, the blade 88 may be inserted into an appropriate narrow slot (not shown) cut vertically into opposed wall portions of the tacking of clamp 48 which define the needle aperture 42 thereof. The blade 88 may be cramped, wedged or welded in this slot as may be found convenient. The upper edge of blade 88 is formed as a sharp cutting edge 90 which extends transversely of the aperture 42. A blade sheath 92, made of metal or other stiff material and which consists essentially of a flattened tube, is telescoped upon the knife blade 88 and extends for substantially the full width of the aperture 42. The sheath 92 is so dimensioned as to be entirely free to move vertically on the blade 88 so that the sheath will fall from the position shown in FIG. 5 into the position shown in FIG. 6 under the influence of gravity alone. The sheath 92 is provided throughout its central upper portion with an opening 94 which is cut out to such a depth that when the sheath is in the position shown in FIG. 6 the cutting edge 98 of blade 88 will be exposed whereas in the position of sheath 92 shown in FIGS. 4 and 5 the upper edges of the cutout portion 94 will envelop and extend the edge 90.

In FIGS. 4, 5 and 6 the broken lines 96 represent the plane of the upper surface of the work against which the tacking clamp 48 is to be pressed during a stitching cycle. Thus, in FIGS. 4 and 5 wherein clamp 40 is in its clamped or operating position assumed during the group stitching operation, the lower knurled or serrated surface thereof is engaged with the surface of the work indicated by the broken lines 96. In that position the sheath 92 has been moved upwardly by engagement thereof with the work, into a position wherein the cutting edge 90 of the blade lies below the upper edges of the cut out opening 94 where it is shielded from contact with the needle thread during the group stitching operation. During such group stitching operation, as programmed by the

cams

26 and 28, a plurality of tacking stitches will be formed parallel with and on one side of the blade 88 and shield 92, the work supporting means 29 being vibrated in one coordinate direction, that is repeatedly between positions to the left and right as viewed in FIGS. 2 and 5, for this purpose. Toward the end of each group stitching operation the work holding means will start a vibratory movement in the other co ordinate direction, that is to the left or right as viewed in FIG. 4, whereby for the next stitch in the group the needle will enter the work on the opposite side of the blade 88. The thread thus extending from the completed group of tacking stitches on one side of the blade 88 will extend under tension upwardly and over the upper edges of opening 94 in sheath 92 and then extends downwardly through the work on the other side of the blade 88. At this moment the tacking clamp 48 will start to rise preliminary to stopping of the machine. As clamp 48 rises from the position shown in FIGS. 4 and 5 toward the position shown in FIG. 6 the shield 92 will be held down by gravity and the tensioned thread extending thereover and thus will expose the edge 88 of knife 88 which then will sever the portion of the me die thread which extends over it. The thread extending from the point of severance through the work and around the looper to the needle will then be withdrawn from the work, as will be explained below.

OPERATION In FIGS. 7 through I4 the operation of the thread severing and thread wiping mechanism of the present invention is illustrated in several sequential steps. Starting with FIG. 7 the parts are in the positions assumed before the commencement of a group stitching cycle. Thus, the needle 16 is in an upper position and the tacking clamp 40 is in an upper or open position. A work piece W consisting, for example, of two layers of material which are to be united by tacking, is shown in a position which it would assume when resting upon the feedplate 34 (the latter not being shown in these views). Since the tacking clamp 40 is in its upper or open position, the forward end of the wiper actuating rod 82 also is in its uppermost position, the vertical position of rod 82 relative to the pivot 70 being indicated by a dimension H3. The thread wiper 68 is weighted to tend to swing under the influence of gravity in a counterclockwise direction away from the position shown in FIG. 7. In FIG. 7 the arm 76 of wiper 68 is on the righthand side and fairly close to the vertical axis of needle vibration. This position is established by the fact that the upper portion of an angularly disposed wall 98 of opening 78 in wiper 68 is resting by gravity against the actuating rod 82. The needle thread T extends downwardly from the head 14 and the conventional thread tensioning and take up means thereof (not shown) and through the eye of needle 16. The portion T1 of the needle thread which has been left at the end of a preceding group stitching operation now extends toward the right and rests freely upon the arm 76 of wiper 68. This is the customary and desired position for the thread portion T1 to assume at the beginning of a group stitching operation.

The knife blade 88 in FIG. 7 is exposed in operative position inasmuch as the sheath 92 has dropped, under the influence of gravity, below the level of the lower surface of the tacking clamp 40. Thus, the position illustrated in FIG. 7 corresponding with that illustrated in FIG. 6.

FIG. 8 is a side view of the parts in the positions illustrated in FIG. 7.

In FIGS. 9 and 10 the parts have been moved into the positions assumed during the group stitching operation and the needle 16 is shown in a position wherein it has penetrated the work W and occupies substantially the lowermost position assumed by the needle. In FIG. 9 it will be observed that the wiper actuating rod 82 has moved downwardly incident to the lowering of the clamp 40 into operative position. This is the lowermost position assumed by rod 82 and its position relative to the pivot 70 is indicated by the dimension H1. This action has positioned the rod 82 in a pocket 100 of generally semi-circular contour formed in the opening 78 in the wiper 68. Because of the shape of the pocket 100 and the fact that the rod 82 fits therein in a fairly snug manner the wiper 68 is locked against rocking about pivot 70. By comparing FIGS. 7 and 9 it will be noted that the locked position assumed by the wiper 68 in FIG. 9 is displaced in a counterclockwise direction from the position shown in FIG. 7, thus avoiding any danger of collision between the wiper arm 76 and the needle 16 during the stitching operation.

In FIGS. 9 and 10 the desired predetermined number of tacking stitches have been formed as a tack generally indicated by the reference character S. The stitches forming tack S extend in one coordinate direction, that is in the direction parallel with the knife blade or transverse the axis of the machine as viewed in FIG. 9. Such stitches are therefore shown in elevation in FIG. 9 and in section in FIG. 10.

Also in FIGS. 9 and 10 the work supporting and clamping assembly 29 has been vibrated in another coordinate direction, that is, rearwardly of the machine or toward the left as viewed in FIG. 10. Such movement has carried the work W, clamp 40 and knife blade 88 backwardly beneath the point of the upraised needle 16 and the needle now has penetrated the work on the other side of the shielded knife blade 88. The stitching mechanism is approaching the point in the stitch cycle wherein the hook of looper 17 is about to engage the thread T carried by the needle.

For purposes of illustration of a particular combination in which the thread severing and thread wiping devices of the present invention are useful the group stitching machine shown is equipped to form a tack of several (for example eight) single thread chain stitches (type 10]) extending back and forth between two needle holes in the work W which are repeatedly penetrated by the needle 16 to form the desired number of stitches constituting a tack S which after severing of the thread in accordance with the present invention may be readily removed from the work when desired. Thus, in each stitch cycle, the looper 17, as shown in FIG. 9, holds a loop such as the loop L from the preceding needle penetration and picks up the portion T2 of the needle thread T to form a new loop which is inserted through the loop L, the latter thereafter being shed by the looper and tightened into the work by the conventional thread take-up mechanism. While this operation has been repeated a number of times in the tackforming part of the group stitching operation disclosed which produced the tack S shown herein the loop L shown in FIG. 9 is the last loop o form a part of the completed tack and the needle th ad has now been inserted through the work on the ot.'- "r side of knife blade 88. Therefore as the parts move "tom the position of FIGS. 9 and 10 towards the posi ion of FIGS. 11 and 12 the loop L will be tightened i.; .o the tack S and a new loop L2 will be engaged ugzzan the looper 17 as shown in FIGS. 11 and 12 and neeile 16 will have been withdrawn, upwardly from the work W. In the meantime because this is the final portion of the group stitching operation, the tacking clamp 40 will have started to rise toward open position, first raising the knife blade 88 upwardly relative to the sheath 92 to expose cutting edge at the point where the thread extends across the blade. The thread T is held under tension at this moment inasmuch as it extends from tack S upwardly over knife 88, downwardly through the work W, continues as loop L2 around the hook of looper l7 and from there extends upwardly through to work W to the rising needle 16 and associated thread tensioning and take up devices. Consequently the needle thread will be severed as the knife 88 moves upwardly against it and the position of the parts shown in FIGS. 11 and 12 is that assumed after severance and the knife 88 has continued to rise with the clamp 40. Severance of the thread leaves a tail 102 extending upwardly from the last stitch in the tack S. The other severed thread end 104 will now be withdrawn downwardly through the work W, and it will be drawn with the thread formerly in loop L2 around the looper l7 and upwardly through the work W as the thread wiper 68 and thread take up mechanism operate as will be described below. The tensioned thread T, usually will have been stretched in length so long as it was under tension whereby, upon being severed by blade 88, it usually will snap back to somewhat shortened length as it is being withdrawn from the work W.

In FIGS. 13 and 14 the withdrawl of the thread end 104 has been completed and the clamp 40 and needle 16 have been raised to their uppermost positions. Consequently the thread end 104 now hangs freely from the eye of needle 16 and the wiper actuating rod 82 has reached a, level indicated by dimension H3, that is, it has reached the same level as that shown in FIGS. 7 and 8. The operation of the thread wiper 68 will now be described by reference sequentially to FIGS. 7 through 14. As mentioned above the wiper 68 with its arm 76 is preferably so weighted that if the actuating rod 82 was to be removed from the opening 78 the wiper 68 would swing under gravity from theposition shown in FIG. 7 in a counterclockwise direction into a position wherein the arm 76 would come to rest in a location somewhat to the right of that shown in FIG. 7. Furthermore it is preferable that the position of wiper 68 under gravity alone would be at least that shown in FIG. 9 so that even when the wiper is locked in the FIG. 9 position the wall 98 of opening 78 in the wiper 68 will tend to remain in contact with the actuating rod 82 by the force of gravity. As already noted the locked position shown in FIG. 9 is the position assumed by wiper 68 when the actuating rod 82 moves downwardly with the tacking clamp 40 at the beginning of a group stitching operation. This position remains fixed during the repeated tack stitching cycles. In the final portion of a group stitching operation the clamp 40 and actuating rod 82 rise rapidly through the position shown in FIGS. II and 12 to the uppermost position shown in FIGS. 13 and 14.

Referring now to FIG. 1 l the rapidly rising vertically moving actuating rod 82 bears progressively against the inclined wall 98 of opening 78 in the wiper 68 the wall 98 thus comprising a cam surface against which the rod 82 acts to sharply accelerate the wiper 68 in a clockwise direction about the free pivot 70. During this time the needle 16 approaches uppermost position and clears the arcuate path of the arm 76 of wiper 68 whereby the arm 76 will pass clockwise beneath the needle 16 sweeping the needle thread with it towards the left as viewed in FIG. 11. The wiper 68 thus cooperates with the conventional thread takeup mechanism of the sewing machine to withdraw the thread including the severed thread end 104 from the work.

The momentum imparted to the thread wiper 68 by the rapidly rising actuating rod 82 is sufficient to carry the wiper 68 clockwise out of contact with the actuating rod 82 and into the position shown in FIGS. 13 and 14. To provide for this free swinging movement of the wiper 68 the opening 78 therein has a generally laterally disposed slot or pocket configuration 106 formed above the locking pocket 100. The slot or pocket 106 is sufficiently deep to permit the arm 76 of wiper 68 to overshoot the thread end 104, as shown in FIG. 13, permitting the thread end to swing downwardly to depend from the eye of needle 16. The momentum of wiper 68 now brings the wall of slot or pocket 106 into sharp collision with the actuating rod 82 which now is in the position shown in FIG. 13. The collision now causes the wiper 68 to rebound assisted by gravity in a counterclockwise directionabout the pivot 78 whereby the arm 76 sweeps the freely hanging thread end 104 from the position shown in FIG. I3 under the needle 316 and into the position formerly occupied by the thread end TI shown in FIG. 7. In that position the thread end 188 will lie upon the upper surface of arm 76 of wiper 68. Also, in that position the wiper 68 will have come to rest under gravity with the upper portion of wall 98 of opening 78 hearing against the actuating rod 82. This, of course, is the position in which the parts and thread end 184 will remain until the initiation of another group' stitching operation.

From a consideration of the foregoing detailed description of the construction and operation of the present invention it will be apparent that it provides a thread severing device and a thread wiper neither of which requires specific driving trains of movable parts. In a sewing machine such as the single thread chain stitch tack forming embodiment of a group'st'itch ma chine the severing device and thread wiper cooperate in a uniquely simple and reliable manner to rapidly produce readily removable tacks each with an upwardly projecting thread tail conveniently accessible for ultimate removal of the tack. The severing device sevcrs the thread at a point above the work while the thread is under tension and immediately thereafter the thread wiper cooperates with the conventional take up mechanism to remove the severed end and half formed stitch from the work. Beyond this combination the thread severing device is capable of use with machines for fonning other specific forms of tacks and having other specific forms of thread wipers. Also, the thread wiper disclosed herein is capable of use with substantially any form of sewing machine wherein a thread wiper is desired whether the thread is severed above or below the work.

It is a particular feature of the thread wiper disclosed herein that it does not depend upon a positive drive for completing its operation once it has been set into motion. It starts rapidly and positively by cam action to remove the thread from the work and its continued movement to complete such removal as well as its return motion utilizes kinetic forces and gravitywhereby movement thereof into final resting position ready for the next group stitching operation need not be completed before the main drive shaft of the machine has come to a stop.

In the embodiment of the invention described in detail hereinabove the thread severing device 86 is shown with the knife blade 88 thereof disposed across the needle aperture 42 of tacking clamp 88 in a direction which is transverse to the axis of the work supporting arm 12 of the sewing machine. It will be apparent that the cutting device might as well be disposed across the aperture 42 in a direction parallel with the axis of said arm 12. In such event the earns 26 and 28 would be so programmed as to form the group of tacking stitches on one side the knife blade 88 by fore and aft reciprocation of the work holding and clamping means 29 and the final incomplete stitch which is removed from the work after action of the severing device would be made by vibrating the work supporting and clamping means 29 transversely of the axis of said arm 12. Otherwise the disposition of the severing device 86 in this alternative position will require no further modification of the machine.

With respect to the wiper 68 it should be noted that the cam means provided thereon for actuation by actuatingrod 82 has been described as a preferred and extremely simple embodiment. The opening '78 formed in the wiper 68 which consists essentially of two angularly diverging rounded-end slots is not only a simple and effective way of providing the required cam surfaces but also serves to reduce the overall weight of the thread wiper. It will be apparent however that the means defining the essential cam surfaces corresponding with the inclined wall 98 and the pockets 100 and 106 (see FIG. 7 for example) could as well comprise suitable profile parts carried by the rear surface of the wiper 68 arranged for cooperation with an acuator rod 82 of appropriate length. Obviously also the means defining the cam surfaces and the actuating means could be interchanged in positions, that is, the cam surfaces could be defined on a movable part such as rod 82 for cooperation with a follower rod, pin or roller mounted on the freely swingable thread wiper 68.

Other obvious variations in the specific details of construction of the thread severing device and of the thread wiper may be adopted by those skilled in the art without departing from the spirit and scope of the present invention.

What is claimed is:

1. In a sewing machine of the group stitch type which comprises a main drive shaft, stitch forming means for forming a tack including a thread carrying needle and a looper, means driven by said main drive shaft for controlling the stopping of the machine in a predetermined position after a predetermined number of stitches has been produced, work supporting and clamping means for holding a work piece in stitch receiving relation with said stitch forming means, said work supporting and clamping means including a tacking clamp having a work engaging lower surface and having a needle receiving aperture through which said needle passes in the formation of stitches, and means for moving said tacking clamp upwardly out of work engaging position as an incident to stopping of said machine, the improvement comprising a thread severing means including a knife blade fixed to said tacking clamp and having an upwardly disposed cutting edge positioned to sever needle carried thread from thread in completed stitches as said tacking clamp moves upwardly incident to stopping of said machine, means for vibrating said work supporting and clamping means in one coordinate direction relative to said needle for the formation of said predetermined number of stitches in said work piece and in a second coordinate direction incident to stopping of said machine to position needle carried thread over the cutting edge of said knife prior to said moving of said tacking clamp upwardly, a thread wiper freely pivoted upon a fixed portion of the frame of said machine and having a thread engaging arm, and actuating means movable as said tacking clamp moves upwardly incident to stopping of said machine for initiating a freely swinging movement of said thread wiper to carry said thread engaging arm beneath said needle while said needle is in an upper position withdrawn from a work piece in such timed relation with the severing of thread by said thread severing means as to cause said thread engaging arm to sweep severed needle carried thread away from completed stitches in a work piece.

2. In a sewing machine of the group stitch type which comprises a main drive shaft, stitch forming means for forming a tack in a work piece including a thread carrying needle and a looper, means driven by said main drive shaft for controlling the stopping of the machine in a predetermined position after a predetermined number of stitches have been produced, work supporting and clamping means for holding a work piece in stitch receiving relation with said stitch forming means, said work supporting and clamping means including a tacking clamp having a work engaging lower surface and having a needle receiving aperture through which said needle passes in the formation of stitches, and means for moving said tacking clamp upwardly out of work engaging position as an incident to stopping of said machine, the improvement comprising a thread severing means including a knife fixed to said tacking clamp and having an upwardly disposed cutting edge positioned to sever needle carried thread from thread in completed stitches as said tacking clamp moves upwardly incident to stopping of said machine, and means for vibrating said work supporting and clamping means in one coordinate direction relative to said needle for the production of stitches forming said tack in said work piece and in a second coordinate direction to position needle carried thread over said cutting edge of said knife prior to said moving of said tacking clamp upwardly.

3. In a sewing machine which comprises a main drive shaft, stitch forming means including a thread carrying needle driven by said main drive shaft for reciprocation in a vertical axis and a looper, means driven by said main drive shaft for controlling the stopping of the machine in a predetermined position after a desired number of stitches has been produced, work supporting means, clamping means, means for moving said clamping means for holding a work piece on said work supporting means in stitch receiving relation with said stitch forming means and for moving said clamping means incident to stopping of the machine away from said position for holding said work piece, and means for severing needle carried thread from thread in completed stitches at the end of a stitching operation, the improvement comprising a thread wiper freely pivoted upon a fixed portion of the frame of said machine and having a thread engaging arm, said thread wiper being adapted to swing back and forth to carry said thread engaging arm beneath said needle when said needle is in an upper position withdrawn from a work piece, means defining a cam surface on said thread wiper, an actuating member engageable with said cam surface and secured to and movable with a part of said means for moving said clamping means, said cam surface being so shaped with respect to the path of movement of said actuating member when said clamping means is moved away from said position for holding a work piece that the movement of said actuating member while in engagement with said cam surface positively and rapidly accelerates said thread wiper to swing in one arcuate direction generally laterally of said actuating means, the kinetic energy thus imparted to said thread wiper causing said thread wiper to continue to swing freely carrying said cam surface out of contact with said actuating member, and means to stop said wiper abruptly after it has swung freely through an arcuate path of predetermined extent and before said kinetic energy has been expended whereby said thread wiper will rebound to swing freely in an opposite arcuate direction to come to rest with said thread engaging arm out of the path of reciprocation of said needle.

4. A sewing machine as set forth in claim 2 wherein said knife blade extends lengthwise in one coordinate direction across said needle receiving aperture and is so positioned with respect to said stitch forming means as to lie parallel with and closely adjacent to the stitches forming a tack produced in a work piece.

5. A sewing machine in accordance with claim 4 wherein said knife blade is provided with a sheath comprising a flattened tubular body telescoped upon the portion of said knife blade which extends across said needle receiving aperture, said sheath having internal dimensions such as to be freely movable into predetermined upward and downward positions upon said knife blade in which positions respectively said sheath encloses and exposes said upwardly disposed cutting edge of said knife blade.

6. A sewing machine in accordance with claim 5 in which said sheath includes portions which extend below the level of said work engaging lower surface of said tacking clamp when said sheath is in said downward position upon said knife blade whereby when said tacking clamp is in clamping engagement with a work piece said sheath is pushed upwardly by engagement with said work piece into said upward position of said sheath.

7. A sewing machine as set forth in claim 2 wherein said knife blade includes at least a portion which extends lengthwise in one coordinate direction into said needle receiving aperture and which is so positioned with respect to said stitch forming means as to lie parallel with and closely adjacent to the stitches forming a tack produced in a work piece.

d. A sewing machine as set forth in claim 2 wherein said knife is provided with shielding means including at least one wall having an upper edge which lies parallel with and adjacent to said upwardly disposed cutting edge of said knife blade, said wall being mounted for movement into predetermined upward and downward positions relative to said cutting edge in which positions respectively said upper edge of said wall lies above said cutting edge to shield said cutting edge against contact with needle carried thread and lies below said cutting edge to expose said cutting edge for contact with needle carried thread.

9. A sewing machine as set forth in claim 3 in which said means to stop said thread wiper abruptly is effective to stop said thread wiper in a position in which said thread engaging arm has passed beyond the severed end of said thread depending from said needle whereby as said thread wiper rebounds said thread engaging arm reengages said severed thread as said thread wiper swings in said opposite arcuate direction to position said severed thread for the start of a subsequent stitching operation of said sewing machine.

10. In a sewing machine as set forth in claim 3 the further improvement which comprises means on said thread wiper engagable with said actuating member when the latter is in the position assumed by it when said work clamping means is clamped in engagement with a work piece substantially to hold said thread wiper against swinging movement in either of said arcuate directions and in a position with said thread engaging arm out of the path of reciprocation of said needle. '1 W l I}! W

Claims

8. A sewing machine as set forth in claim 2 wherein said knife is provided with shielding means including at least one wall having an upper edge which lies parallel with and adjacent to said upwardly disposed cutting edge of said knife blade, said wall being mounted for movement into predetermined upward and downward positions relative to said cutting edge in which positions respectively said upper edge of said wall lies above said cutting edge to shield said cutting edge against contact with needle carried thread and lies below said cutting edge to expose said cutting edge for contact with needle carried thread.

10. In a sewing machine as set forth in claim 3 the further improvement which comprises means on said thread wiper engagable with said actuating member when the latter is in the position assumed by it when said work clamping means is clamped in engagement with a work piece substantially to hold said thread wiper against swinging movement in either of said arcuate directions and in a position with said thread engaging arm out of the path of reciprocation of said needle.