US3534696A - Work feeding mechanism for sewing machines - Google Patents

Description

United States Patent 72 lnventors Erich Martin willenbacher,

Karlsruhe, Hagsfeld; Ulrich Schmedtkord, Karlsruhe, Baden- Wu'erttemberg, Germany [21] Appl. No 794,197 [22] Filed- Jan. 27,1969 [45] Patented Oct.20, 1970 [73] Assignee The Singer Company New'York, New York a corporation of New Jersey [54] WORK FEEDING MECHANISM FOR SEWING MACHINES 7 Claims, 5 Drawing Figs.

{52] U.S.CI 112/215 [50] Field ol'Search 112/215 [56] References Cited UNITED STATES PATENTS 1,145,620 7/1915 Seymour 112/215 1,182,712 5/1916 Ruckstuhl 112/215 1,927,489 9/1933 Clayton 112/215 Primary Examiner-Alfred R. Guest Altomeys Marshall .1. Breen, Chester A. Williams, Jr. and

Harold Weinstein ABSTRACT: This disclosure relates to a sewing machine having a cam assembly for controlling sewing machine instrumentalities, such as work feeding, in which the cam assembly includes conjugate cams that actuate a pivotal lever of a follower linkage to effect advance and return of the feed-dog.

Patented Oct. 20, 1970 Sheet INVENTORS Erich M. Willenbucher 8| Ulrich Schmgdtkord RNEY BY W WITNESS K M h m-med? Patented Oct. 20, 1970 Sheet 2 of INVENTORS Erich M. Willenbuc'her 8 Ulrich Schmedtkord ATT RNEY Patented Oct. 20, 1970 Sheet 5 of 5 m w TM Ncd Y E06 E Vbm N N h R MC '0 w A E I" U .w B8

VI B WORK FEEDING MECHANISM FOR SEWING MACHINES BACKGROUND OF THE INVENTION Heretofore, sewing machines, especially those capable of producing ornamental stitching such as fagoting or hemstitching" could have the work feeding mechanism and other sewing machine instrumentalities actuated by means of eccentrics or pattern-cams. The use of eccentrics had certain shortcomings, such as structural complexity and cost.

The prior art pattern-cams might be either of two general types. The first type of pattern-cam uses a single assembly to control both the forward feed and the backward feed of the work. The second type of pattern-cam uses two separate assemblies. one to control the forward feed of the work and the other to control the backward feed thereof. In either instance the pattern-cams of the prior art have been noisy, worn excessivcly, and had a limiting effect on operational speed and cam configuration.

SUMMARY OF THE INVENTION In accordance with the present invention a novel work feed ing mechanism for a sewing machine is provided with a feeddog and a feed-dog lifting means adapted to raise and lower the feed-dog in a predetermined timed sequence. A feed-dog driving means is also connected to the feed-dog to advance said feed-dog forwardly and backwardly in a predetermined time relationship with the feed-dog lifting means. The feeddog driving means includes conjugate cams and a follower linkage having a lever pivotally connected to be actuated by said conjugate earns to effect the forward and backward advancement of the feed-dog.

It is therefore an object of the present invention to provide an improved work feeding mechanism for sewing machines, especially those capable of producing ornamental stitching, which overcomes the prior art deficiencies; which is simple, economical and reliable; which includes a cam assembly having conjugate cams and a pivotal right angle lever with offset cam followers which followers provide for positive return of the lever; which includes a pivotal right angle lever having offset cam followers, one of which produces the driving motion, and the other of which insures a positive return; which permits quiet running at high speed operation of the feed mechanism; which uses conjugate cams. one shaped to produce the desired motion, and the other shaped to compensate for the different radial distances from the center of said motion producing cam; which uses a work feeding mechanism that includes a lifting means and a driving means operated in timed relationship to each other; and which includes a lifting means and a driving means for the feed-dog operated in a timed sequence whereby the feed of the driving means is less than that of the lifting means.

Other objects and advantages will be apparent from the following description of one embodiment of the invention and the novel features will be particularly pointed out hereinafter in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS This invention is illustrated in the accompanying drawings in which:

FIG. 1 is a partial longitudinal vertical section of a sewing machine embodying the present invention,

FIG. 2 is a bottom plan view of the bed of the sewing machine embodying the present invention,

FIG. 3 is an enlarged perspective view of the novel work feeding mechanism of FIGS. 1 and 2,

FIG. 4 is a schematic representation of the improved work feeding mechanism as viewed in the bottom plan view of FIG.

FIG. 5 is a schematic perspective view representing the improved work feeding mechanism corresponding to the FIG. 3 representation thereof.

DESCRIPTION OF THE INVENTION The sewing machine 10 illustrated in FIGS. 1 and 2 has the usual bed I2 in which is journaled a rotary bcd shaft 14 driven by a belt 16 from the main arm shaft (not shown) located in the machine arm. Operatively connected to the rotary bed shaft 14 through the gear box 18 is a loop-taker 20 in the form of a rotary hook complemental to a thread-carrying needle 22 carried in the lower end of a needle bar 24 journaled for endwise reciprocation in the head 26 which extends from an over hanging bracket arm (not shown). The work to be stitched is depressed into contact with a throat plate 28 by a presser foot 30 carried on a lower end of a spring presser-bar 32 endwise slidable in the head 26:

Opposing the presser-foot 30 in feeding the work is a feeddog 34 of the drop-feed type illustrated in FIG. 3. In the machine chosen to illustrate the present invention. the feeddog 34 is actuated by a work feeding mechanism. designated generally as 36. and best illustrated in FIG. 3 in a manner such that the feed-dog 34 can advance the work twice forwardly and once backwardly in a predetermined sequence of feeding strokes used particularly in the production of l'agoting. Of course, the work feeding mechanism could also be adapted for straight stitching, or other ornamental stitching such as hemstitching.

The feed-dog 34 is secured, preferably by screws 38 (FIG. 3), to one end of a feed-bar 40 the other end of which is bifurcated and pivotally connected to a rock-arm shaft 42 carried at either end by a pair or rock-arms 44 preferably integral with a feed-advance rock shaft 46 extending longitudinally along one side of the bed 12. and journaled in transversely spaced ribs 48 therein.

The rock shaft 46 is included in a driven linkage 50 which actuates the same responsive to a positive return double cam or conjugate earns 52 driven in turn from the bed shaft 14 to complete the feed-dog driving means assembly, designated generally 54. A feed-dog lifting assembly 56 includes a feed raising link 58 rotatably connected to an eccentric 60 driven by the bed shaft 14. The feed raising link 58 is secured to a bent finger or projection 62 extending from the under side of the feed-bar 40. preferably by a shoulder screw 64. Rotation of the bed shaft 14 causes the eccentric 50 to actuate the feeddog lifting assembly 56 to periodically raise the serrated surface of the feed-dog 34 above the level of the top of the throat plate 28 to effect a gripping of the work in opposition to the presser foot 30. In other words, rotation of the bed shaft 14 and eccentric 60 causes the feed raising link 58 to pivot the feed-bar 40 about the rock-arm shaft 42 to alternately raise and lower the feed-dog 34. The feed-dog lifting assembly 56 is shown schematically in FIG. 5 to indicate the raising and lowering of the feed-dog 34 at the dotted double headed arrows 66, or any point therebetween.

A cam assembly 68, including the conjugate cams 52, is mounted on a vertical shaft 70 having an axis 71 and journaled in a support flange 72 connected across two adjacent transverse ribs 48 of the bed 12. A worm gear 74 is mounted upon the bed shaft 14, as illustrated in FIGS. 1 and 2, to drive a worm wheel 76 carried by the vertical shaft for rotation of the same. A preferred driving ratio is one rotation of the shaft 70 for every 6 rotations of the bed shaft 14. The worm wheel 76 is disposed above the support flange 72, and the conjugate earns 52 are carried below the flange with a pair of collars 78 fixed to the shaft at either end thereof to maintain the assembled position of the wheel 76 and the conjugate earns 72. The conjugate cams 52 include an upper cam 80 which is the controlling cam, and a lower can 82 which is the compensating cam. The purpose of the conjugate earns 52 will be more fully explained hereinafter.

In addition to the cam assembly 68, the feed-dog driving assembly 54 also includes the driven linkage 50 having a right angle lever 84 pivotally carried on a post 86 connected to the under side of support flange 72 to define a pivot point 88. The

lever 84, as best seen in FIG. 2, is substantially T-shaped with a main portion 90 extending substantially longitudinal of the bed 12 from which a projecting portion 92 transversely extends. The pivot point 88 is located substantially in the middle of the main portion 90 and it is approximately from this point that the projecting portion 92 extends. The edge 94 adjacent the conjugate cams 52 is formed semicircular and extends from the end of the projecting portion 92 to the right end 96 of the main portion 90. The lever 84 is bifurcated at either end of the edge 94 so as to carry rollers or cam followers 98 and 100, respectively. With the pivot point 88 serving as an apex, a right angle is defined by passing a line from the pivot point 88 through the center of the rollers 98 and 100. The elevation of the roller 98 corresponds to that of the lower can 82, while the right end 96 has been offset in height above that of the remainder of lever 84 so that the roller 100 corresponds in elevation to the upper cam 80.

in the preferred embodiment, the use of the conjugate earns 52 eliminates overthrow due to the inertia of the components of the driven linkage 50, resulting in a quite running high speed work feeding mechanism 36. To accomplish this the conjugate cams 52 are made of a cooperative configuration. The upper cam 80 is patterned to control the forward and backward feeding motion of the driven linkage 50 and serves to actuate the cam follower 100 to produce the same. The lower cam 82 is patterned to compensate for variations in the distance from the periphery of the upper cam 80 to the axial line 71. The effect of patterning the lower can 82 90 out of phase" with the upper cam 80 is to lock or trap the lever 84 via the cam follower 98 and insure against overthrow thereof. Thus, the right angle lever 84, provided with two rollers or cam followers 98 and 100 offset in height, allows the contour or pattern of the conjugate earns 82 and 80 to be closely followed.

The left end 102 of the main portion 90 of the lever 84 has an arcuate slot 104 in which one end of a connecting rod 106 is fixed, by a ball joint or universal connector 108. The other end of the connecting rod 106 is fixed to a balljoint or universal connector 110 of a rock shaft crank 112 fixedly carried by the rock shaft 46. The center line of the rock shaft crank 112 is used to determine the radius of the arc in slot 104. The length ofthe connecting rod 106 may be adjustable as at 114.

Actuation of the conjugate earns 52 causes the lever 84 to pivot about point 88 as illustrated in FIG. 4, to produce, through connecting rod 106, the rocking motion of the rock shaft 46 so as to derive the workadvancing and work-returning motion of the feed-dog 34. By adjusting the position of the universal connector 108 in the slot 104 the amount of the forward and backward feeding of the feed-dog 34 may be increased or decreased to change the length of the stitches.

FIG. is a perspective view of the work feeding mechanism 36, which is actuated in a timed sequence upon rotation of the bed shaft 14 to produce the desired motion, be it raising, lowering or advancing, in a forwardly or backwardly direction, of the feed-dog 34. The extent of this motion is represented by the dotted arrows 66 and the solid arrow 116, respectively, which arrows are double headed to show that the movement may be in either of the directions indicated. Aside from the representation of the feed-dog 34 motion, the solid lines in FIG. 5 represent the limits of travel of the work feeding mechanism 36 in one direction while the dotted lined represent the limits of travel in the other direction with reference to the feed-dog driving assembly 54. Accordingly, FIG. 5 shows schematically what motion the various components indicated by the reference characters partake of.

It will be understood that various changes in the details materials, arrangements of parts and operating conditions which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principles and scope of the invention as expressed in the claims.

We claim:

1. In a sewing machine a cam assembly for controlling sewing machine instrumentalities corn rising:

a. a shaft rotatably mounted int e sewing machine;

b. conjugate cams mounted for rotation by the shaft;

c. a lever pivotally mounted in the sewing machine adjacent the conjugate cams;

a pair of cam followers disposed on the lever in spaced relation to each other. for engagement with the conjugate cams whereby one cam follower acts to shift the lever and the other cam follower acts to positively return the lever;

e. the pair of cam followers forming a substantially right angle therebetween with the point of the pivotal mount of the lever defining the apex of said right angle; and

f. a linkage means connected to the lever to be moved responsive the cam actuated pivoting of said lever.

2. A work feeding mechanism for a sewing machine comprising:

,a. a feed-dog;

b. a feeddog lifting means adapted to raise and lower the feed-dog in a predetermined timed sequence;

c. a feed-dog driving means including conjugate cams and a follower linkage;

d. the conjugate cams rotate about an axis lying in a plane perpendicular to the plane in which lies the follower linkage of the feed-dog driving means;

e. the follower linkage including a lever pivotally connected to be actuated by said conjugate cams, and adapted to advance the feed-dog forwardly and backwardly in a predetermined timed relationship with the feed-d0g lifting means;

. the lever pivotal about an axis parallel to the axis of the conjugate cams; the lever has a pair of followers disposed at an angle of substantially with respect to the axis, about which the lever pivots whereby said axis defines the apex of said substantially 90 angle; and the pair of followers offset from one another a distance corresponding to the spacing between the conjugate cams so that said followers separately engage said conjugate cams; one follower producing the driving motion of the lever and one follower enabling the positive return of the lever.

3. The combination claimed in claim 2 wherein:

a. the feed-dog lifting means includes an eccentric;

b. a bed shaft driving the eccentric and the feed dog driving means; and

c. the follower linkage includes a rock shaft connected to the feed-dog, and a connecting rod interconnecting the rock shaft and the lever.

4. The combination claimed in claim 3 wherein:

a. the connecting rod has a universal connection at each end to permit the rocking motion of the rock shaft responsive to actuation of the follower lever by the conjugate carns.

5. The combination claimed in claim 3 wherein:

a. the lever has a slot formed in the end thereof remote from said offset followers; and

b. the connecting rod has one end thereof fixedly connected in the lever slot whereby the length of feed is adjustable upon repositioning the rod connection within said slot.

6. The combination claimed in claim 3 wherein:

a. the feed dog driving means includes a worm wheel driven from the bed shaft at a speed less than that of the eccentrio.

7. The combination claimed in claim 1 wherein:

a. the lever has a main portion and a projecting portion;

b. the main portion, along a substantially linear line, carries the said one cam follower at one end, has the linkage connected to the other end and the pivotal connection intermediate thereof; and

c. the projecting portion extends from the pivotal connection of the main portion to carry the other cam follower at its outer end at a point substantially perpendicular to the said linear line in the main portion.

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