US3641957A

US3641957A - Zigzag cam drive in combination with a sewing machine

Info

Publication number: US3641957A
Application number: US7294A
Authority: US
Inventors: Susumu Hanyu
Original assignee: Janome Sewing Machine Co Ltd
Current assignee: Janome Corp
Priority date: 1970-01-21
Filing date: 1970-01-21
Publication date: 1972-02-15
Anticipated expiration: 1989-02-15

Abstract

A worm driving the zigzag cam of a sewing machine through a gear is reciprocated in axial direction by a control cam so that the axial movement of the helical thread of the worm is accelerated and decelerated, resulting in cyclical acceleration and deceleration of the rotational speed of the zigzag cam which permits the construction of the zigzag cam with a smaller pitch than in conventional constructions so that the sewing machine makes a greater number of zigzag stitches during each cam revolution.

Description

United States Patent Hanyu Feb. 15, 1972 ZIGZAG CAM DRIVE IN COMBINATION WITH A SEWING MACHINE Inventor:

Susumu Hanyu, Tokyo, Japan Assignee: Janone Sewing Machine Co., Ltd., Tokyo,

Japan Filed: Jan. 21, 1970 Appl. No.: 7,294

Related US. Application Data Continuation-impart of Ser. No. 674,367, Aug. 24, i967, abandoned.

Foreign Application Priority Data Aug. 25, 1966 Japan Al/55539 U.S.Cl. ..lI2/I$8R Int. Cl. ..D05b 3/02 FieldofSearch ..ll2/l58 R,98',74l393,425.5

34 MM Ill kill!!! [56] References Cited UNITED STATES PATENTS 1,61 L372 l2/l926 Rader ..1 12/98 3,326,058 6/l967 Morrison ..74/393 Primary Examiner-Patrick D. Lawson AtlorneyMichael S. Striker [57] ABSTRACT A worm driving the zigzag cam of a sewing machine through a gear is reciprocated in axial direction by a control cam so that the axial movement of the helical thread of the worm is accelerated and decelerated, resulting in cyclical acceleration and deceleration of the rotational speed of the zigzag cam which permits the construction of the zigzag cam with a smaller pitch than in conventional constructions so that the sewing machine makes a greater number of zigzag stitches during each cam revolution.

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2 or 3 FT F Zane/0214 97 W J ""1 ZIGZAG CAM DRIVE IN COMBINATION WITH A SEWING MACHINE REFERENCE TO A RELATED APPLICATION The present application is a continuation-in-part application of the copending application Ser. No. 674,367, filed Aug.

It is known to drive a needle bar in a transverse zigzag movement by means of a zigzag cam which is driven by a worm gear meshing with a continuously rotating worm.

in such an arrangement, the number of zigzag stitches used during each revolution of the zigzag cam, depends on the number of crests and valleys of the peripheral cam track of the zigzag cam. It is desirable to increase the number of zigzag stitches for each revolution of the zigzag cam since in this manner particularly beautiful zigzag stitches can be obtained. However, when the number of depressions or valleys of the cam track is increased without increase of the diameter of the zigzag cam difficulties arise since the point of the cam follower does not fully follow the depressed cam track portions. If the point of the cam follower is sharpened to a needle point, the point would be soon worn off, and could not obtain the desired purpose. Consequently, the point of the cam follower has a given size and surface area, which cannot be changed substantially, and it is necessary to design the zigzag cam track for cooperation with a cam follower whose point has a certain given size. Consequently, a zigzag cam having a certain diameter is limited to a certain number of cam track depressions.

When a sewing machine makes zigzag stitches, it is necessary for the needle to penetrate the stitched cloth or fabric. A cam having a given diameter has a corresponding limited number of cam depressions. While the number of cam depressions could be increased if the diameter of the zigzag cam would be increased, this is not possible solution, since the zigzag cam has to be mounted within the housing of the sewing machine and assembled with many other parts so that the diameter of the zigzag cam is limited for use in standard sewing machines so that no oversize zigzag cam can be used. Even if special large diameter zigzag cam would be built into the sewing machine, such a cam would have the disadvantage of a noisy operation, and great wear due to the increase of the peripheral speed of the larger cam.

SUMMARY OF THE INVENTION It is one object of the invention to overcome the disadvantages of zigzag cam drives according to the prior art, and to provide a zigzag cam which, for a given diameter, produces a greater number of transverse zigzag oscillations of the needle bar and needle during each revolution of the zigzag cam.

Another object of the invention is to accelerate and decelerate a zigzag cam during each revolution.

Another object of the invention 'is to provide a zigzag cam having a greater number of cam lobes and cam recesses than a standard zigzag cam of the same diameter, without impairing the sensing operations of a standard cam follower.

With these objects in view, the present invention provides a worm rotated by a drive shaft and reciprocated in axial direction by control means. A gear connected with a zigzag cam meshes with the worm, and is accelerated and decelerated in accordance with the axial displacement of the worm during rotation of the same. Since the rotary speed of the cam varies cyclically during each revolution, the effect of each cam lobe and cam recess is the same as if it were extended in circumferential direction as compared with an arrangement in which the cam rotates at constant speed. Due to this variable speed of the zigzag earn, a zigzag cam of relatively small diameter obtains a number of zigzag stitches per revolution which is far greater than the number of zigzag stitches obtained by conventionally arranged zigzag cams having the same diameter.

III

Another object of the invention is to provide a zigzag cam drive of small dimensions which can be easily built into a sewing machine housing, and is subject to little wear. With this object in view, the zigzag cam according to the invention can have a smaller diameter than standard zigzag cams, but nevertheless obtain the same number of transverse zigzag stitches as the larger cam according to the prior art. The reduction of the diameter and size of the zigzag cam according to the invention, also reduces the quantity of material required for its manufacture, and also facilitates the assembly. A zigzag cam of reduced size in accordance with the invention, also facilitates the arrangement and design of other parts of the sewing machine located in the proximity of the zigzag cams.

Furthermore, as a result of the reduction of the diameter of the zigzag cam according to the invention, the peripheral speed of the zigzag cam is reduced, which reduces the wear of the point of the cam follower and also reduces the wear of the cam track so that the zigzag cam is of great durability.

Another object of the invention is to provide a zigzag cam drive of very simple construction. With this object in view, a cam track is formed in one end portion of a sleeve-shaped worm, and is engaged by a stationary cam follower which preferably carries a roller so that the worm is axially reciprocated on the drive shaft during rotation with the same. Preferably, a coil spring surrounds a portion of the drive shaft and abuts a flange on the same and also the end portion of the sleeve-shaped worm so that the cam track in the sleeve-shaped worm is pressed against the stationary cam follower.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings,

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a side elevation, mainly in vertical section, illustrating a zigzag sewing machine provided with a zigzag cam drive according to the invention;

FIG. 2a and 2b are two diagrammatic views illustrating operational conditions for the zigzag cam of the invention, and for a zigzag cam according to the prior art, respectively;

FIGS. 3a, and 3b are diagrams illustrating the lateral oscillations of the needle bar, and the angular rotation of the zigzag cam depending on the axial reciprocation of the worm during each revolution of the drive shaft; and

FIG. 4 is a fragmentary front elevation, partially in section and broken ofi, illustrating the zigzag cam driven on an enlarged scale.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring first to FIG. I which mainly illustrates a conventional sewing machine provided with the novel zigzag cam drive of the invention, a drive shaft 1 is mounted in the frame 50 of the zigzag sewing machine and is driven from a pulley 26 in the conventional manner by a motor, not shown. A crank 49 and takeup lever 48 are mounted at one end of drive shaft I for pulling the thread, and another crank 47 is connected with a needle bar 49 by a connecting member 46 so that the needle bar 45 is reciprocated with needle 44 in an up-and-down movement during which the fabric is penetrated by the needle and stitches are formed by the top thread, and by the bottom thread supplied by shuttle 40. A presser foot 42 at the lower end of a presser bar 43 can be manually operated for pressing the fabric against the feeding means, not shown, provided in the machine bed 4 I. Needle bar 45 is supported by pivot 38 on a bracket 39 of frame 50 and is mounted for up-and-down movement on the needle bar support 36 biassed by a spring 37. Needle bar support 36 is pivotally connected by a pivot 34 with the end of a connecting rod 35 whose other end is connected with a cam follower means II which cooperates with the zigzag cam 4 which is'mounted on a cam shaft 5 which extends at right angles to drive shaft l and above the same. Zigzag cam 4 is shown to have unifonnly spaced cam lobes and recesses between the same so that needle bar 45 with needle 44 is oscillated to perform zigzag stitches of equal amplitude under the control of cam 4 and cam follower 11.

As best seen in FIG. 4, drive shaft 1 has an axial groove in which a key 6 is located for connecting a sleeve-shaped worm 2 with drive shaft 1 for rotation, but also for axial movement relative to the same. The inner surface of worm 2 has a key groove [6 receiving a portion of key 6.

The outer surface of the sleeve-shaped worm 2 has a helical thread 20 extending to one end of worm 2, while an endless cam groove or track 21 is formed in the other end portion 2a of worm 2 and bounded by an annular wall having an axial end face 22 engaged by a coil spring whose end abuts a fixed flange 9 on drive shaft l for compensating wear. The endless cam track 21 rises and falls in axial direction at an angle less than the angle of the helical thread 20.

The endless cam track groove 21 is engaged by the roller 7 of a cam follower 8 which is fixedly secured to the frame portion.

A worm gear 3 meshes with the helical thread of worm 2 and is rotated when drive shaft 1 rotates worm 2. Since zigzag cam 4 and gear 3 are both secured to shaft 5, cam 4 rotates at the same speed as gear 3, which is slower than the rotary speed ofdrive shaft 1.

As shown in fig. 1, an amplitude adjusting rod 33 is connected at its upper end with connecting rod 35 and is adjusted by means of a dial 3] and an amplitude limiting lever 30 so thal the amplitude of the zigzag stitches can be adjusted and set. The field position of the zigzag stitches can be selected by operation of an adjusting lever 29 which controls a pivotally mounted adjusting arm 27. A feed adjusting member 28 controls the speed of the feeding dog, not shown, by which the fabric is transported under the presser foot 42.

During each revolution of drive shaft 1 with worm 2, gear 3 turns zigzag cam 4 through the pitch angle 7, as shown in FIG. 2A. However, due to the axial reciprocation of worm 2 by the control means 21, 7, 8, which includes the end portion 2a of the worm 2 as a control member, the speed of zigzag cam 4 is not constant, but slowed down during engagement of cam follower ll with the crest and valley portion E, E, and faster during engagement of cam follower ll with the falling and rising intermediate cam portions F. Since the angle of cam track Zl is less than the angle of the thread 20, gear 3 and cam 4 do not stop during rotation and angular reciprocation of worm 2.

Referring now to FIG. 3B, the graph [1 illustrates the axial reciprocatory displacement of worm 2 by the endless cam track 2l during one revolution of the drive shaft and turning ofzigzag cam 4 through the pitch angle 'y. if control means 21, 7. 8 were not provided, the angular rotation of cam 4 would take place in accordance with the straight graph C which in dicates the axial displacement of the helical thread 20 of worm 2. Since the accelerating and decelerating axial movements produced by control means 2], 7. 8 are superimposed on the axial movement of the helical thread 20 the same moves in axial direction at a speed represented by the graph d, which corresponds also to the angular speed of gear 3 and zigzag cam 4.

By reducing the rotational speed of cam 4 when the crest and valley portions E, E cooperated with cam follower ll, the cam follower remains for a longer period of time in contact with the crest and valley portions of zigzag cam 4, and consequently the needle bar and needle remain for a corresponding longer time in terminal positions in which the needle can penetrate and stitch the fabric, which is not possible during transverse oscillation of the needle. FIG. 3A illustrates at a, a lateral oscillation of the needle bar. Consequently, the points g and h on graph C are not effective, and the points g and h on graph d represent the actual conditions. and indicate the angle of rotation during which the needle bar is in its terminal positions. Irrespective of the fact that the zigzag cam 4 would dill produce stopping of the oscillating needle bar in terminal positions during rotation through the angle B without control means 2l, 7, 8, due to the action of the control means 21, 7, 8 the effective angle during which the needle bar is stopped becomes a. The relation between the mechanical stop angle 5 and the effective stop angle a is or B Consequently, a zigzag cam having a greater number ofcrests and valleys can be used in accordance with the invention, than a zigzag cam of the same diameter in accordance with the prior art, since the difference between the angles a and B is utilized without damage of the driving angle.

FlGS. 2A and 213 respectively illustrate the cam tracks according to the invention and according to the prior art, respectively, The pitch angle 7 is smaller in a cam 4 according to the invention than the pitch angle 7' in a cam 4' according to the prior art. The radial depth of the crest and valleys of the cams, and the diameters of the cams are the same. The stop angle 6, however, is smaller than the stop angle 8' in the prior art construction of FIG. 2B which is possible due to the additional acceleration and deceleration produced by the control cam means 2], 7, 8. The difference 8' 8 is utilized by increasing the number of crests and valleys of the cam. The cam 4 according to the invention obtains the number n, and the prior art cam 4 obtains the number n' of zigzag oscillations and stitches for one cycle, and the following relation is valid:

It will be seen that the zigzag cam drive of the invention permits an increase of the number of zigzag stitches for each cycle without increasing the diameter of the cam. Futhermore, the point of the cam follower ll can follow the track of cam 4 due to the varying speed while it could not follow a cam having the small pitch angle of the same would rotate at constant speed. Due to the speed reduction when the crest and valley portions control cam follower ll, sufiicient time is available for the stitching of the fabric by the needle.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of zigzag cam drives difl'ering from the types described above.

While the invention has been illustrated and described as embodied in a zigzag cam drive by which rotation of a zigzag cam is accelerated and decelerated, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I. Zigzag cam drive in combination with a sewing machine including a needle bar, said cam drive comprising, in combination, a drive shaft; a worm having a helical thread and being connected with said drive shaft for rotation therewith and also for axial movement relative to the same; a gear meshing with said helical thread; a zigzag cam connected with said gear for rotation and having crest portions, valley portions, and intermediate rising and falling portions; cam follower means cooperating with said cam and oscillating in accordance with said crest and valley portions between two end positions said needle bar being mounted for longitudinal stitching movement and for transverse zigzag movement; means connecting said drive shaft with said needle bar for causing said stitching movement; connecting means connecting said cam follower means with said needle bar so that the same is oscillated in said transverse zigzag movement during rotation ofsaid worm. gear, and zigzag cam, between two terminal positions for performing said stitching movement; and control means for reciprocating said worm in axial direction during each revolution of the same in the direction of rotation of said zigzag cam so that the rotary speed of said zigzag cam is increased during engagement of said rising and falling portions by said cam follower means, and opposite to the direction of rotation of said zigzag cam so that the rotary speed of said zigzag cam is reduced during engagement of said crest and valley portions by said cam follower means whereby said cam follower means remains longer in said end positions and said needle bar remains longer in said terminal positions for performing said stitching movement.

2. Zigzag cam drive in combination with a sewing machine including a needle bar, said cam drive comprising, in combination. a drive shaft; a worm having a helical thread and being connected with said drive shaft for rotation therewith and also for axial movement relative to the same; a gear having teeth meshing with said helical thread; a zigzag cam connected with said gear for rotation in one direction and having crest portions, valley portions, and intermediate rising and falling portions cam follower means cooperating with said cam and oscillating in accordance with said crest and valley portions between two end positions; said needle bar being mounted for longitudinal stitching movement and for transverse zigzag movement means connecting said drive shaft with said needle bar for causing said stitching movement; connecting means connecting said cam follower means with said needle bar so that the same is oscillated in said transverse zigzag movement during rotation of said worm, gear, and zigzag cam, and moves between two terminal positions for performing said stitching movement; and control means for reciprocating said worm during each revolution of said worm in a forward stroke in said one direction while said cam follower means engages said rising and falling portions of said cam so that the rotary speed of said cam is increased and the time periods during which said cam follower means is operated by said rising and falling portions are shortened, and in a rearward stroke opposite to said one direction while said cam follower means engages said crest and valley portions so that the rotary speed of said cam is reduced and the time periods during which said cam follower means is operated by said crest and valley portions are lengthened whereby said needle bar remains longer in said terminal positions for performing said stitching movements, said control means including a control member limiting the length of said strokes for moving said worrn during said rearward stroke a lesser distance than said helical thread of said worm travels forward in said one direction so that said cam is alternately accelerated and decelerated without being stopped.

3. Zigzag cam drive as claimed in claim 2 wherein said control member includes a cam member 2a having an endless cam track wherein said control means further include a cam follower member engaging said endless cam track, one of said members being stationary and the other one of said members being connected with said worm for rotation therewith; and wherein said endless cam track rises and falls in axial direction at an angle less than the angle of said helical thread of said worm so that said gear and said zigzag cam do not stop during rotation and axial reciprocation of said worm.

4. Zigzag cam as claimed in claim 3 wherein said cam member is secured to said worm for rotation therewith; and wherein said cam follower member is stationary.

5. Zigzag cam drive as claimed in claim 2 wherein said worm includes a sleeve mounted on said drive shaft; comprising key means connecting said sleeve with said drive shaft for rotation, and for relative axial movement; wherein said control member is connected with said sleeve for axially reciprocating the same during each revolution of said drive shaft with said key means and said sleeve.

6. Zigzag cam drive as claimed in claim 5 wherein said sleeve has at one end thereof a cam portion constituting said control member and formed with an endless cam track rising and falling in axial direction; and wherein said control means includes a stationary cam follower engaging said cam track so that said cam portion and sleeve reciprocate in axial direction during rotation of said sleeve with said drive shaft.

7. Zigzag cam drive as claimed in claim 2 wherein said drive shaft has a flange means; wherein said worm includes a sleeve mounted in said drive shaft and connected with said control member so as to be reciprocated by the same in axial direction; comprising means connecting said sleeve with said drive shaft for rotation and relative axial movement; wherein said sleeve has an end portionspaced from said flange means in axial direction; and comprising a spring between said flange means and said end portion of said sleeve and abutting the same and said flange means.

8. Zigzag cam drive as claimed in claim 7 wherein said end portion of said sleeve is said control member and formed with an endless cam track rising and falling in axial direction of said drive shaft and said sleeve; and wherein said control means include a stationary cam follower engaging said cam track so that said sleeve reciprocated in axial direction during rotation of said sleeve with said drive shaft.

9. Zigzag cam drive as claimed in claim 8 wherein said spring is a coil spring surrounding a portion of said drive shaft between said flange means and said end portion of said sleeve.

Claims

1. Zigzag cam drive in combination with a sewing machine including a needle bar, said cam drive comprising, in combination, a drive shaft; a worm having a helical thread and being connected with said drive shaft for rotation therewith and also for axial movement relative to the same; a gear meshing with said helical thread; a zigzag cam connected with said gear for rotation and having crest portions, valley portions, and intermediate rising and falling portions; cam follower means cooperating with said cam and oscillating in accordance with said crest and valley portions between two end positions said needle bar being mounted for longitudinal stitching movement and for transverse zigzag movement; means connecting said drive shaft with said needle bar for causing said stitching movement; connecting means connecting said cam follower means with said needle bar so that the same is oscillated in said transverse zigzag movement during rotation of said worm, gear, and zigzag cam, between two terminal positions for performing said stitching movement; and control means for reciprocating said worm in axial direction during each revolution of the same in the direction of rotation of said zigzag cam so that the rotary speed of said zigzag cam is increased during engagement of said rising and falling portions by said cam follower means, and opposite to the direction of rotation of said zigzag cam so that the rotary speed of said zigzag cam is reduced during engagement of said crest and valley portions by said cam follower means whereby said cam follower means remains longer in said end positions and said needle bar remains longer in said terminal positions for performing said stitching movement.

2. Zigzag cam drive in combination with a sewing machine including a needle bar, said cam drive comprising, in combination, a drive shaft; a worm having a helical thread and being connected with said drive shaft for rotation therewith and also for axial movement relative to the same; a gear having teeth meshing with said helical thread; a zigzag cam connected with said gear for rotation in one direction and having crest portions, valley portions, and intermediate rising and falling portions cam follower means cooperating with said cam and oscillating in accordance with said crest and valley portions between two end positions; said needle bar being mounted for longitudinal stitching movement and for transverse zigzag movement means connecting said drive shaft with said needle bar for causing said stitching movement; connecting means connecting said cam follower means with said needle bar so that the same is oscillated in said transverse zigzag movement during rotation of said worm, gear, and zigzag cam, and moves between two terminal positions for performing said stitching movement; and control means for reciprocating said worm during each revolution of said worm in a forward stroke in said one direction while said cam follower means engages said rising and falling portions of said cam so that the rotary speed of said cam is increased and the time periods during which said cam follower means is operated by said rising and falling portions are shortened, and in a rearward stroke opposite to said one direction while said cam follower means engages said crest and valley portions so that the rotary speed of said cam is reduced and the time periods during which said cam follower means is operated by said crest and valley portions are lengthened whereby said needle bar remains longer in said terminal positions for performing said stitching movements, said control means including a control member limiting the length of said strokes for moving said worm during said rearward stroke a lesser distance than said helical thread of said worm travels forward in said one direction so that saiD cam is alternately accelerated and decelerated without being stopped.

7. Zigzag cam drive as claimed in claim 2 wherein said drive shaft has a flange means; wherein said worm includes a sleeve mounted in said drive shaft and connected with said control member so as to be reciprocated by the same in axial direction; comprising means connecting said sleeve with said drive shaft for rotation and relative axial movement; wherein said sleeve has an end portion spaced from said flange means in axial direction; and comprising a spring between said flange means and said end portion of said sleeve and abutting the same and said flange means.