Work feeder for sewing machine

United States Patent

[11] 3,530,809

[72] Inventor Robert E. Porter

Oak St., Hamilton, Massachusetts 01982

[21] Appl.No. 807,489

[22] Filed March 17,1969

[45] Patented Sept. 29,1970

2,549,057 4/1951 Chinnici....................... 112/207

2,967,498 1/1961 Russelletal.................. 112/207

Primary Examiner—Alfred R. Guest

Attorney—Kenway, Jenney and Hildreth

[54] WORK FEEDER FOR SEWING MACHINE 7 Claims, 2 Drawing Figs.

[52] U.S.CI........................................................ 112/207

[51] int. Cl.........................................................D05b 27/06

[50] Field of Search............................................ 112/207,

212,215

[56] References Cited

UNITED STATES PATENTS

1,243,160 10/1917 Grieb........................... 112/207

ABSTRACT: Apparatus for advancing the upper layer in synchronism with the underlying layer of an assembly being sewn. The apparatus is driven simultaneously by the lower feed mechanism and by the needle drive of the sewing machine. It includes a springbiased, arm pivoted from the lower feed system and cam-driven from the stitching mechanism. At the end of the arm a serrated work-engaging feed dog is formed. The arm may be lifted from contact with the work being sewn by means of a foot treadle.

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Patented Sept. 29, 1970

3,530,809

FIG. I

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' INVENTOR.

ROBERT E.PORTER

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ATTORNEYS

3,530,809

WORK FEEDER FOR SEWING MACHINE

It has long been conventional in sewing machines to provide a feed mechanism which is usually disposed in an opening in the throat-plate of the work surface of the machine and which operates to advance the underlayer of material being sewn. In some instances a combined main and differential feed is utilized, first to determine the number of stitches per unit length and, second, to compensate in some degree for stretch in the material being sewn. However, it frequently becomes necessary for an operator to simultaneously retard the advance of the lower layer and smooth the upper layer to prevent unwanted gathering or stretching of the material during the sewing operation. Various devices have been proposed to simplify the operator’s task and these generally are designed to exert a pull on the material which is timed with the lower feed mechanism as well as the stitching operation.

In another approach to the problem, as exemplified in U.S. Pat. No. 277,409, a rotary feed wheel driven by a flexible cable is utilized. The flexible cable, in turn, is driven by the basic power source of the sewing machine and provision is made to vary the rate of drive by means of an adjustable diameter pulley. The desired cyclic action is provided by placing the flexible cable in torsion periodically and permitting it to unload by similar periodic rotations of the rotary feed wheel.

All of the known feed mechanisms are subject to certain disadvantages, not the least of which is their relatively complexity and their tendency to clutter the work area and to interfere with ease of operation of the sewing machine.

Accordingly, the primary object of the present invention is to feed work assemblies efficiently and with a minimum of complex machinery into a sewing machine. Secondary objects of the invention are to decrease the cost and increase the reliability of apparatus for feeding work into a sewing machine.

Generally, the present invention is based upon the concept of applying to the upper layer of materials being sewn a pressure and motion which is comparable to that applied to the lower layer of the material by conventional feed dogs. These concepts are realized by the provision of a serrated surface forming an upper feed dog disposed above and in juxtaposition to the serrated surface of a conventional main feed dog. This surface is formed at the end of an arcuate arm which is mounted to slide and pivot in a manner which permits the upper feed dog to duplicate the action of the lower feed dog as it affects the material being advanced. A reciprocally rotating cam engages the lower surface of the arm, and cam following is assured by the same spring pressure which causes the serrated surface to engage the material. The cam derives its reciprocating rotation from the basic stitching needle drive and that limited rotation is effective to lift and lower the feed arm in accordance with the movement of the needle which is driven from the same source.

The lower main feed dog is driven by a main feed bar and an eccentric in a conventional manner and the upper feed arm of the present invention is pivoted upon that bar to derive basic motion from the same eccentric source. At the end of the feed arm remote from the material-contacting surface, the previously mentioned spring pressure is provided by means of a tension spring. At the same point, a link to a foot treadle is mounted to permit lifting of the feed surface from the material when it is desired to prevent or discontinue its feeding operation.

For a better understanding of the present invention, together with other and further objects, features and advantages, reference should be made to the accompanying drawing of a preferred embodiment of the invention in which:

FIG. 1 is an end elevation of the feeding mechanism showing fragmentarily portions of the sewing machine to which the feeding device is applied, the upper feed dog being at one limit of its excursion, and

FIG. 2 is a view similar to that of FIG. 1 but showing the feed arm in a retracted position at the opposite limit of its excursion.

Referring now to the drawing, there may be seen in outline a portion 11 of the main frame of the sewing machine. The machine may be of the type disclosed in catalog No. 103S, 2nd Edition, of the Union Special Machine Company entitled Streamlined High Speed Overseamers published by Union Special Machine Company of Chicago, Illinois in March of 1966. Reference is made to that catalog only for purposes of setting one background in which the present invention is operative. Of course, the invention may be applied to any one of a variety of sewing machines where feed for the upper layer of an assembly to be sewn is needed.

Other elements conventional in sewing machines are also illustrated. For example, there may be seen a main feed dog 12 mounted by means of a screw in a vertical slot formed in a main feed bar 14. The main feed bar extends rearwardly and terminates in a generally horizontal slot in which a pivotable feed bar guide block 15 is slidably disposed. A horizontal slot 16 is also formed in the lower right hand or forward portion of the main feed bar 14 beneath and to the left of the vertical slot in which the main feed dog is mounted.

A shaft 17, rotating on the indicated center line passes through a feed lift block 18 and is engaged in an eccentric bushing 19. The feed lift block 18 is slidably engaged in the forward slot 16. Behind the main feed bar 18 is a differential feed bar 20 having a forward slot similarly engaging the feed lift block 18. However, the differential feed bar 20, on which a differential feed dog 22 is mounted, is driven by a slightly different eccentric bushing.

A link 24 connects the eccentric 19 to the main feed bar 14 by means of a pin 28 and a similar link 26 connects the different eccentric to the differential feed bar 20 by means of a pin 30. As a result of the arrangements shown and described, and as is more explicitly shown in the catalog cited above, the vertical motions of the two feed dogs are the same but their horizontal motions are somewhat different.

The showing of the lower feed dogs, both the main feed dog, the differential feed dog and their drives, have been simplified to permit easier understanding of the present invention. It should be understood that in an actual installation, the feed system is considerably more complex. However, there has been shown and described only those portions of a practical sewing machine which are necessary to an understanding of the present invention.

Attached to the main feed bar 14, by welding or other suitable procedure is an upper feed pivot mount 32. The mount 32 may, of course, be made integral with the main feed bar 14. Pivoted upon the upper feed mount 32 is an upper feed arm 34 at the back end of which an opening is formed to accommodate a tension spring 36. Adjacent that back end is a vertical link 38 which may be attached to a foot treadle (not shown). The end of the link 38 is turned through 90° to provide a surface for contacting the upper surface of the upper feed arm 34 when the treadle to which the link 38 is attached is depressed.

The arm 34 includes an arcuate portion the under surface of which is in contact with a cam 40 carried by an arm 42 fixed for limited rotation with a drive shaft 44 which also drives a needle 46 mounted on an arm 48.

Material to be sewn is shown schematically at 50 as it enters the bite between a presser foot 52 and a throat-plate 54. As is plain from the drawing, the lower feed dogs, both the main feed dog and the differential feed dog are disposed in openings formed in the throat-plate 54.

The presser foot 52, as is conventional, is pivotally mounted and urged by a hair spring 56 in a clockwise direction toward the throat-plate 54. The presser foot 52 and the hair spring 56 are carried by a presser arm 58. The presser arm 58 is pivotally mounted on a fulcrum block 60 and is urged downwardly by a spring-biased presser plunger 62.

3,530,809

Although FIGS. 1 and 2 of the drawing are essentially similar, both being fragmentary end elevations, FIG. 1 shows the feed apparatus in the position which it assumes at the end of a feeding cycle. It will be noted that both the lower feed dogs 12 and 22 are in a raised position where their serrated upper surfaces extend above the level of the throat-plate 54 to engage cloth being fed into the machine. Of course, the needle 46 at this point is upraised and withdrawn from contact with the material being sewn.

At the same time, the arm 42, which is locked at an angle to the needle-supporting arm 48, is at a point counterclockwise of vertical and is about to exert a lifting force upon the upper feed arm 34 when clockwise motion occurs. Also at this time, the main feed bar 14 and the differential feed bar 20 are at the upper limit and leftward limit of their excursion, as seen in the drawing.

With clockwise rotation of the needle drive of the sewing machine, as seen in FIG. 2, the needle 46 has made a stitching stroke and the rotation of the cam 40 on its arm 42 has caused the upper feed arm 34 to be lifted, disengaging the upper feed dog from the upper surface of the material being sewn. At the same time also, the lower feed dogs have been carried downwardly and to the right by their respective feed bars through the action of the eccentric coupling and the links between those feed bars and the drive of the sewing machine. They are then ready for the next feeding motion which will take place as the shaft 17 continues its rotation. Simultaneously, as the shaft 44 reverses its direction to lift the needle 46 from the material, the arm 42 will be moved in a counterclockwise direction to lower the presser arm 34 and permit engagement of the work by the upper feed arm.

The eccentric drives applied to the main feed bar and the differential feed bar provide a feeding stroke during which the lower feed dogs are above the level of the throat-plate during the entire leftward excursion of the feed dogs. Further rotation of the main drive shaft by way of the eccentrics and the links to the feed bars causes the feed bars to drop and then move in a rightward direction while they are retracted. Further rotation still of the main shaft causes the feed dogs to rise and the cycle is then repeated. By reason of its connection to the mount 32 the upper feed arm 34 makes the same generally horizontal excursions with the upper feed dog in juxtaposition to the lower main feed dog. However, the action of the cam 40, which is synchronized with that of the needle 46, causes the cloth-engaging surface of the arm 34 to be lifted as the lower main feed dog 12 drops and to be dropped as the lower main feed dog 12 rises. In a sense, the upper feed dog has an action which is a mirror image of the action of the lower main feed dog and the two feed dogs thus cooperate to move the work assembly along a desired path during the stitching operations.

Clearly, the present invention is applicable to any sewing machine in which there is provided apparatus for actuating a lower feed dog in a manner similar to that described above. The upper feed mechanism of the invention may be incorporated in the machine as originally constructed or it may be added as an attachment with only simple modifications required. The invention should not be limited to the details of the foregoing description but only by the spirit and scope of the appended claims.