US3894500A - Stop motion mechanism for sewing machines - Google Patents

Abstract

This disclosure relates to improvements in stop motion mechanisms of sewing machines. The improved stop motion mechanism permits the sewing machine drive shaft to coast for about 1 1/2 revolutions before being abruptly stopped. This arrangement permits a material reduction in the speed of the drive shaft at the time it is stopped. The stop motion mechanism includes a pair of cams which are adjustable with respect to one another wherein the distance which the main shaft of the machine rotates between the time in which it is disconnected from the drive pulley and wherein it is abruptly stopped may be readily adjusted.

Description

United States Patent Hsiao [75] Inventor: James C. Hsiao, Chicago, 111.

[73] Assignee: Union Special Corporation, Chicago.

[22] Filed: Sept. 27, 1974 [21] App]. No: 509,957

[52] US. Cl. 112/219 R; 112/67 [51] Int. Cl D05b 69/26 [58] Field of Search 112/219 R, 219 A, 220, 112/221, 67. 87

[56] References Cited UNITED STATES PATENTS 2.721526 10/1965 lvanko w. 112/67 2.82277l 2/1958 Hale et all 112/219 [451 July 15, 1975 Primary Examiner-H. Hampton Hunter Attorney, Agenl, or FirmDiller. Brown Ramik & Wight [57] ABSTRACT This disclosure relates to improvements in stop motion mechanisms of sewing machines The improved stop motion mechanism permits the sewing machine drive shaft to coast for about 1 /2 revolutions before being abruptly stopped. This arrangement permits a material reduction in the speed of the drive shaft at the time it is stopped. The stop motion mechanism includes a pair of cams which are adjustable with respect to one another wherein the distance which the main shaft of the machine rotates between the time in which it is disconnected from the drive pulley and wherein it is abruptly stopped may be readily adjusted.

11 Claims, 6 Drawing Figures 1 STOP MOTION MECHANISM FOR SEWING MACHINES This invention relates in general to new and useful improvements in sewing machines, and more particu larly to an improved stop motion mechanism for sewing machines.

It is well known to provide stop motions for sewing machines wherein the main drive shaft of the machine is first disengaged from the drive pulley, after which the machine is permitted to coast for a short period followed by the abrupt stopping of the machine. However,

these prior stop motion mechanisms normally permitted only about one half revolution after clutch disengagement before the machine was stopped. The net result was that the shaft speed had not materially reduced at the time it was abruptly stopped.

In accordance with this invention, it is proposed to provide an improved stop motion mechanism which includes two separate control cams which are adjustable relative to each other and which are so related to the remainder of the stop motion mechanism wherein the main drive shaft is permitted to coast between one and one and one-half revolutions before the main drive shaft is abruptly stopped. Further, by providing two cams for controlling the operation of the stop motion mechanism and by making the cams adjustable relative to one another, an adjustment can be made to increase or decrease the coasting time of the drive shaft. This adjustment permits one to compensate for the slight differences in the manufacture and assembling of each machine.

The greater speed reduction provided by the increased coasting time of the stop motion mechanism of this invention has the following advantages:

l. Less wear on the parts involved in stopping the machine.

2. The noise at the time the machine is stopped is reduced.

3. There is less overthrow in the machine.

4. Double cycling of the machine is prevented.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings:

IN THE DRAWINGS FIG. I is a side elevational view, with parts broken away and shown in section, of a sewing machine incorporating the stop motion mechanism of this invention.

FIG. 2 is a fragmentary plan view of the base portion of the machine with parts broken away and shown in section and shows the operating means of the stop motion mechanism.

FIG. 3 is a fragmetnary elevational view of the other side of the machine from FIG. 1 with parts broken away and shown in section and shows further details of the stop motion mechanism.

FIG. 4 is an enlarged exploded perspective view of the stop motion cam assembly.

FIG. 5 is an enlarged front elevational view of the assembled stop motion cam discs.

FIG. 6 is a fragmentary sectional view taken along the line 6-6 of FIG. I and shows further the details of the cam discs.

Before referring to the drawings, it is pointed out that the type of sewing machines for which the improved stop motion was developed are known as group stitch machines or cyclic machines. Typical of these machines are those disclosed in U.S. Pat. Nos. 2,5 l L367 and 2,609,773, granted to George W. Nelson and No. 3,509,838, granted to Richard E. Bowin. Besides button sewing machines, this group of machines also ineluded tacking machines of the type disclosed in U.S. Pat. No. 3,749,041 also granted to Richard E. Bowin.

Referring now to the drawings in detail, it will be seen that the machine is generally identified by the numeral 9 and includes a vertical standard 10 having a base portion I] and a sub-base l2. Extending horizontally from the base portion 11 is a work supporting arm 13 which is adapted to carry a conventional looper and thread cutter (not shown). Above the arm 13 and extending horizontally from the upper end of the vertical standard 10 is an overhanging arm 14 which has at its outer end a head portion 15. A needle bar 16, which carries a needle 17, is mounted for vertical reciprocatory movement in the head portion 15.

A main shaft 18 is rotatably mounted in the base II and it is to be understood that conventional driving means are provided from the main shaft for operating the needles and looper for performing the desired stitching operation, such as attaching a button to a workpiece. Inasmuch as these driving means are in no way part of this invention, no attempt has been made to illustrate the same or to further disclose the details thereof here.

As is clearly shown in FIG. 1, the main shaft 18 carries an eccentric 19 which is adapted to rock a member 20 back and forth through a suitable are upon each revolution of the main shaft 18. During a stitching cycle of the machine, the rocking of member of 20 is an idle rocking and performs no function. However, upon completion of a stitching cycle, the lower end of a link 21 is shifted towards the left into the position shown in FIG. I so that its shoulder 22 is in the path of a laterally extending portion 23 of the member 20. At this time the rocking of member 20 by the eccentric 19 will cause a downward movement of the link 21.

The upper end of link 21 is pivotally connected to one arm 24 of a button clamp lifting lever 25 which is pivotally mounted by a stud 26 in the overhanging arm 14. The forwardly extending arm 27 of the lever 25 carries a downwardly extending rod 28, the lower end of which extends laterally and carries a roller 29. The roller 29 is adapted to cooperate with the undersurface of a hookshaped rod 30 secured to a button clamping mechanism 31. The button clamping mechanism is of the same type as that disclosed in aforementioned U.S. Pat. Nos. 2,511,367; 2,609,773 and 3,509,838. It is pivotally mounted on the frame of the machine by a rod 32. The clamping member 31 is normally urged downward during a stitching cycle by a spring 33. When the rod 28 is lifted upwardly and in turn lifts the rod 30, the clamping mechanism 31 will pivot about the rod 32 and lift the button retaining portion thereof away from the work supporting arm 13.

During a stitching cycle, the lower end of link 21 is normally retained in a position to the right of that shown in FIG. I so that the shoulder 22 thereof will be out of the path of the laterally extending portion 23 of the member 20. However, when the machine is at rest, these parts are in the positions illustrated in FIG. 1.

Upon starting of the machine, the lower end of link 21 will be moved towards the right (FIG. 1). This is accomplished by the operators action on a foot treadle or knee press (neither shown) which will cause a counter-clockwise rocking movement of a stop motion rock shaft 34 to which is secured an arm 35. The lower end of the arm 35 is pivotally connected to a link 36, the other end of which is pivotally connected to the lower end of the link 21. Just prior to the completion of the selected number of stitches and the automatic stopping of the machine, the rock shaft 34 will be rocked in a clockwise direction (FIG. 1) to return the link 21 to the position shown in FIG. I and thus place the shoulder 22 in the path of the laterally extending portion 23 of the rock member 20. Accordingly, upon the next revolu' tion of the main shaft 18, the eccentric 19, in rocking the rock member 20, will cause the laterally offset portion 23 to contact the shoulder 22 of the link 21 and urge the link 21 downwardly. This, as mentioned above, will result in the counter-clockwise rocking of the lever 25 or cause the roller 29, carried by the rod 28, to engage the rod 30 and lift the rod 30 along with the button clamping mechanism 31. At this time the machine will be automatically stopped.

In accordance with this invention, the machine is provided with a stop motion mechanism which represents an improvement on that of the previously mentioned Nelson and Bowin patents. As is clearly shown in FIGS. 2 and 3, there is provided on one side of the machine a stop motion plunger lever 37 which is fixedly secured to the stop motion rock shaft 34. The plunger lever 37 carries a plunger rod 38 which, in turn, carries a stop motion plunger 39 at its left end (FIG. 3). A number of spring washers 40, which are carried by the plunger rod 38, bias the stop motion plunger 39 towards the left, as seen in FIG. 3. The plunger lever also carries a lever 41, the free end of which is provided with a camming surface 41a (FIG. 2) operable to operate a conventional friction clutch which serves to connect the main shaft 18 with a power driven pulley 42. The friction clutch includes a clutch disc which is fastened to a stop motion disc 43 which, in turn, is fastened to the main shaft 18. The disc 43 is provided with a pawl 44 and a latch 45 (FIG. 3) which cooperate with the stop plunger 39 in stopping the machine. The plunger 39 is biased towards the stop motion disc 43 by a spring 46 connected at one end to the plunger lever 37 and its other end to the frame of the machine.

On the other end of the rock shaft 34 from the stop motion plunger lever 37, there is secured a lever 47 which carries a cam follower 48, as is best seen in FIGS. I and 2. The cam follower 48 is positioned to engage edges of cam discs 49 and 50 mounted on a cam shaft 51. Disc 49 is fixedly mounted, by a pressed fit, on a hub 52 ofa gear 53. The disc 50 loosely tits on the hub 52 and is provided with a hub 54. The discs 49 and 50 are secured to the cam shaft 51 by screws 55 passing through threaded openings in the hub 54 and elongated openings 56 in the hub 52.

A hub 57, which is part of the disc 49, provides for the proper spacing between the discs 49 and 50. An adjustable shoe 58 is located between the discs 49, 50 an is pivotally mounted at one end to disc 50 by a sch: 59. An elongated circumferentially extending hole 591 in the cam disc 49 provides clearance and easy access to the shoulder screw 59. At its other end, the shoe 58 is secured in one of two positions by a shoulder screw 60 selectively passing through one of two holes 61,6la in the cam disc 50.

The cam disc 49 has two peripheral notches 62 and 63 with the notch 62 being defined by steps 64 and 65, and the notch 63 being defined by steps 66 and 67. As is readily apparent from FIGS. 4 and 5, the notches 62 and 63 are identical and are 180 degrees out of phase with the steps 64 and 66 being somewhat deeper than the steps and 67.

The disc 50 is also provided with two identical, diametrically opposed cutouts or notches 68 and 69 of a different shape than the notches 62 and 63. The notches 68 and 69 are generally in line with the notches 62 and 63 when the discs 49 and 50 are mounted in position on the cam shaft 51. The diameters of the discs 49 and 50 are equal and in such a relation to the position of the lever 47 that when the cam follower 48 rides on the edges of the discs, the rock shaft 34 is positioned to hold the plunger 39 out of contact with the stop motion disc 43.

With the shoe S8 in the position illustrated in FIGS. 3 and 5, the shoe 58 blocks or covers notch 63 so that the machine will go through a full cycle or stitch 16 stitches before stopping. This will allow a four hole button to be sewn. If it is desired to sew a two hole button, for example, the shoe will be raised and secured to the disc with the screw 60 passing through hole 61a. With the shoe in this position, the notch 63 will be opened and the machine will be stopped after every eight stitching cycles.

With the machine in its normal or stopped position, the stop motion plunger lever 37 and the cam discs 49 and 50 are in the positions shown in FIGS. 1 and 3. To start a stitching operation, the operator depresses a foot treadle (not shown) which is connected by a chain 70 to a lever 70a pivotally mounted in the sub-base 12 of the machine by means of a bracket 71. The lever 70a pivots in a counter-clockwise direction and stud 72 carried thereby contacts a downwardly extending arm 73 of the plunger lever 37 to pivot the plunger lever in a clockwise direction and remove the plunger 39 thereof from engagement with the stop motion disc 43. At the same time, the camming surface of the lever 41 acts on the pulley 42 to engage the clutch and thus connect the power driven pulley 42 to the main drive shaft 18 to effect rotation of the drive shaft 18.

With reference to FIG. 1, the lever 47 will be pivoted in a counterclockwise direction to remove the cam follower 48 from the lower step 64 of the notch 62 in the cam disc 49. The machine now begins the sewing cycle with the cam follower riding on the edges of the cam discs 49 and 50. The cam shaft 51 is driven in a clockwise direction by suitable gearing in the base of the ma chine so that the cam discs 49 and 50 rotate at a ratio of one revolution to every 16 revolutions of the main drive shaft 18.

The machine continues to be driven by the pulley 42 until the notch 62 of the cam disc 49 approaches the cam follower 48. At this time the cam follower 48 drops from the edge of the cam discs 49, 50 onto step 65 of cam disc 49. This slight drop rotates the rock shaft 34 in a clockwise direction. As is seen in FIG. 3, the stop motion plunger lever 37 is rocked slightly in a counterclockwise direction moving the plunger 39 towards the stop motion disc 43. The lever 41 is rocked enough to cause its camming surface to disengage the pulley 42 from the clutch and main drive shaft l8 of the machine. At this time the machine has about l to T A revolutions remaining in its sewing cycle. The machine, being disengaged from the pulley 42,will merely coast until it is stopped. The position of the plunger 39 at this time is still far enough away from the stopmotion disc 43 to allow the pawl 44 and latch 45 to pass the plunger 39 in a clockwise direction.

Referring once again to FIG. 1, it will be seen that the continued rotation of .the cam discs 49 and 50 will cause the cam follower 48 to drop from the step 65 to the bottom step 64 of the notch 62. This also causes the plunger lever 3'7,and,the plunger 39 to drop to their final stopping positions. At this time, the stop motion disc 43 has about one-half revolution remaining before the pawl 44 and the latch 45 cooperate with the plunger 39 to stop the machine. Also, at this time, as previously described, the button clamp mechanism 31 is lifted away from the work supporting arm 13, allowing the operator to remove the sewn button and insert a new button for the next sewing cycle.

An advantageous feature of the invention lies not only in the increased coasting time of the machine at the end of a sewing cycle, but also that this coasting time can be adjusted. This can be accomplished by adjusting cam disc 50 in relation to cam disc 49. The cam disc 50 is provided with an elongated circumferential slot 80, as is shown in FIGS. 4 and 5. A screw 81 passes through the slot 80, through a spacing collar 82 and into a threaded bore 83 in the cam disc 49. The screw 81 serves to clamp the cam disc 50 to the cam disc 49 in its adjusted position. The screws 55 also serve to clamp the cam discs 49 and 50 together in addition to securing the cam discs to the cam shaft 51.

In order to adjust the position of the cam discs 49 and 50 in relation to the cam shaft 51, only the screws 55 must be loosened. The screw 81 remains in a tightened condition to keep the relationship between the cam discs 49 and 50 from changing. To adjust the relationship between the cam discs 49 and 50, the screw 81, along with the screws 55, must be loosened. By adjusting the cam disc 50 with respect to the cam disc 49, the distance D (FIG. 5) can be selectively increased and decreased.

At this time it is pointed out that, as illustrated in FIG. 5, the cam disc 50 is shown in its extreme counterclockwise position. The distance D, in this view, is at its lowest or most decreased setting. In an actual machine, the cam 50 would be about in the center of the adjustment range. In the following discussion of the adjustment of the relative positions of the cam discs 49 and 50, it is to be assumed that the cam disc 50 is in the center position.

By rotating the cam disc 50 in a clockwise direction, the distance D will be increased, and by rotating the cam disc 50 in the opposite direction, the distance D will be decreased. Increasing the distance D will allow the cam follower to drop down to the step 65 sooner, thereby increasing the coasting time of the machine at the end of the machine at the end of the sewing cycle. This will cause the speed of the machine to be decreased further, from that of the previous setting, at the time the machine is stopped. In like manner, in rotating the cam disc 50 in the opposite direciton relative to the cam disc 49, the coasting time of the machine will be decreased and the speed of the machine, at the time it is stopped, will be increased from that of the previous setting.

In the illustrated arrangement, the coasting time of the machine at the end of a sewing cycle can be adjusted from I to 1% revolutions. In rotating the cam disc 50, the shoe 58 will also be rotated. If the shoe 58 must be replaced, the elongated hole 59a will provide access to the screw 59 in any position to which the cam disc has been rotated relative to the cam disc 49. It will, of course, be necessary to remove the cam discs 49 and 50 from the cam shaft 51 in order to replace the shoe 58.

Itwillbe readily apparent from the foregoing that by adjusting the relative positions of thecam discs 49 and 50, the coasting time of the machine can be readily adjusted to compensate for differences in manufactured parts and in assembling the machines. Thus, if after assembly one machine was found to have higher frictional forces than another machine, then this machine would be adjusted for a shorter coasting time than the machine having low frictional forces. Further, it will be apparent that when replacing worn parts, the coasting time may have to be readjusted.

Although only a preferred embodiment of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made in the stop motion mechanism without departing from the spirit and scope of the invention, as defined by the appended claims.

I claim:

1. A stop motion mechanism for a sewing machine of the type including a main drive shaft, a drive pulley, a clutch for selectively coupling the main drive shaft to the drive pulley for being driven thereby, a stop motion disc carried by the main drive shaft, first lever means for controlling actuation of the clutch, second lever means for interlocking with the stop motion disc for stopping and preventing rotation of the main drive shaft, the improvement residing in rock means for rocking said first and second lever means in unison, said rock means including a cam shaft driven from said main drive shaft at a reduced ratio, a cam carried by said cam shaft for rotation therewith, said cam having a primary surface and adjacent first and second radial steps, a rock lever connected to said first and second lever means for rocking the same and a cam follower carried by said rock lever for riding on said cam primary surface and for sequential engagement with said steps, and said steps being radially spaced from said primary surface distances wherein when said follower engages said first step said first and second levers are rocked a distance sufficient to disengage the clutch and insufficient to engage the stop motion disc and when said cam follower engages said second step said first and second levers are rocked a distance to stoppingly engage the stop motion disc.

2. The stop motion mechanism of claim I wherein said first step is circumferentially elongated, and control means for supporting said cam follower along a selected portion of said first step to vary the effective length of said first step to vary the interval between clutch release and main drive shaft stoppage.

3. The stop motion mechanism of claim 2 wherein said control means is in the form of a second cam having a control step positioned intermediate the ends of said first step.

4. The stop motion mechanism of claim 3 together with means mounting said second cam relative to the first mentioned cam for selective angular rotational positioning, and means for locking said cams together in selected angular rotated positions.

5. The stop motion mechanism of claim 4 wherein said cams have concentric telescoped hubs forming part of said mounting means.

6. The stop mechanism of claim 4 wherein said cams have concentric telescoped hubs forming part of said mounting means and screw means carried by an outer one of said hubs passing through an inner one of said hubs securing one of said cams to said cam shaft.

7. The stop motion mechanism of claim 3 wherein each cam has plural sets of said steps, and blocking means associated with at least certain of said sets of steps for selectively rendering the associated set of steps inoperative.

8. The stop motion mechanism of claim 7 wherein said blocking means is in the form of a shoe positioned between said cams.

9. The stop motion mechanism of claim 7 wherein said blocking means is in the form of a shoe positioned between said cams, means pivotally mounting one end of said shoe, and means for selectively positioning a second end of said shoe relative to said cams to selectively render said shoe operative and inoperative.

10. The stop motion mechanism of claim 1 wherein said cam has plural sets of said steps, and blocking means associated with at least certain of said sets of steps for selectively rendering the associated set of steps inoperative.

11. The stop motion mechanism of claim 1 wherein said main drive shah and said cam shaft are in parallel relation, and said first and second lever means and said rock lever are carried by a third shaft disposed parallel to said main drive shaft and said cam shaft.

i I 3 l

Claims (11)

1. A stop motion mechanism for a sewing machine of the type including a main drive shaft, a drive pulley, a clutch for selectively coupling the main drive shaft to the drive pulley for being driven thereby, a stop motion disc carried by the main drive shaft, first lever means for controlling actuAtion of the clutch, second lever means for interlocking with the stop motion disc for stopping and preventing rotation of the main drive shaft, the improvement residing in rock means for rocking said first and second lever means in unison, said rock means including a cam shaft driven from said main drive shaft at a reduced ratio, a cam carried by said cam shaft for rotation therewith, said cam having a primary surface and adjacent first and second radial steps, a rock lever connected to said first and second lever means for rocking the same and a cam follower carried by said rock lever for riding on said cam primary surface and for sequential engagement with said steps, and said steps being radially spaced from said primary surface distances wherein when said follower engages said first step said first and second levers are rocked a distance sufficient to disengage the clutch and insufficient to engage the stop motion disc and when said cam follower engages said second step said first and second levers are rocked a distance to stoppingly engage the stop motion disc.

2. The stop motion mechanism of claim 1 wherein said first step is circumferentially elongated, and control means for supporting said cam follower along a selected portion of said first step to vary the effective length of said first step to vary the interval between clutch release and main drive shaft stoppage.

3. The stop motion mechanism of claim 2 wherein said control means is in the form of a second cam having a control step positioned intermediate the ends of said first step.

4. The stop motion mechanism of claim 3 together with means mounting said second cam relative to the first mentioned cam for selective angular rotational positioning, and means for locking said cams together in selected angular rotated positions.

5. The stop motion mechanism of claim 4 wherein said cams have concentric telescoped hubs forming part of said mounting means.

6. The stop mechanism of claim 4 wherein said cams have concentric telescoped hubs forming part of said mounting means and screw means carried by an outer one of said hubs passing through an inner one of said hubs securing one of said cams to said cam shaft.

7. The stop motion mechanism of claim 3 wherein each cam has plural sets of said steps, and blocking means associated with at least certain of said sets of steps for selectively rendering the associated set of steps inoperative.

8. The stop motion mechanism of claim 7 wherein said blocking means is in the form of a shoe positioned between said cams.

9. The stop motion mechanism of claim 7 wherein said blocking means is in the form of a shoe positioned between said cams, means pivotally mounting one end of said shoe, and means for selectively positioning a second end of said shoe relative to said cams to selectively render said shoe operative and inoperative.

10. The stop motion mechanism of claim 1 wherein said cam has plural sets of said steps, and blocking means associated with at least certain of said sets of steps for selectively rendering the associated set of steps inoperative.

11. The stop motion mechanism of claim 1 wherein said main drive shaft and said cam shaft are in parallel relation, and said first and second lever means and said rock lever are carried by a third shaft disposed parallel to said main drive shaft and said cam shaft.

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