US3495560A

US3495560A - Presser device for sewing machines

Info

Publication number: US3495560A
Application number: US752665A
Authority: US
Inventors: Francis L Walling
Original assignee: Singer Co
Current assignee: SSMC Inc
Priority date: 1968-08-14
Filing date: 1968-08-14
Publication date: 1970-02-17
Anticipated expiration: 1987-02-17
Also published as: DE1940658A1; DE1940658C3; BR6911416D0; GB1259388A; DE6931576U; DE1940658B2; SE366073B; FR2015628A1

Description

Feb. 17, 1970 F. L. WALLING 3,495,560

' PRESSERDEVICE FOR SEWING MACHINES Filed Aug. 14, 1968 Fig. I

INVENTOIR. FICIHCIS L. Wallmg I BY wumsss: i v

Rim-J2 m amm AT NEY United States Patent 3,495,560 PRESSER DEVICE FOR SEWING MACHINES Francis L. Walling, Red Bank, N.J., assiguor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed Aug. 14, 1968, Ser. No. 752,665

Int. Cl. D05b 29/12 US. Cl. 112235 4 Claims ABSTRACT OF THE DISCLOSURE The sewing head portion of a sewing machine is dis closed including a presser device organized so that the presser bar and main presser spring will not be moved by the ordinary operation of the work feeding mechanism. The presser foot is carried on the presser bar by means of a curved leaf spring which, in addition to reducing the inertia of theparts of the presser device that move substantially perpendicularly of the direction of work feed in response to operation of the work feeding mechanism, gives rise to movement of the presser foot thereby in the line of work feed which minimizes the frictional resistance which the presser foot imparts to transport of the work.

Background of the invention This invention relates to sewing machine presser devices, and more particularly, to presser devices of the low inertia type adapted to be engaged periodically with a sewing machine work feeding mechanism.

In sewing machines employing a drop feed mechanism, i.e., a work feeding mechanism including a feed dog which is raised above the level of a work supporting throat plate and advanced, and then dropped beneath the level of the throat plate and returned, a presser device serves to press the plies of fabric being seamed against the throat plate and in opposition to the feed dog when it is raised. It has long been recognized in the art that inertia forces acting on the presser device can result in an upward overthrow of the presser foot after the rise of the feed dog resulting in failure of the presser device to oppose the feed dog consistently during the work-advance stroke of the feed dog. A number of low inertia presser devices are known in the art for minimizing such inertia forces acting on the presser foot.

Perfection in the transport of work fabrics past the stitching point of a sewing machine, however, involves considerations in addition to that of consistently urging the work fabrics against the feed dog. There is, for instance, a profound difference between the factors which influence feeding of a lower ply of fabric which directly engages the feed dog and those factors which influence feeding of a top ply of fabric which engages the presser foot. The production of fiat, wrinkle free seams requires, from the standpoint of work feeding, that the top and bottom plies of work fabric must be advanced in like amounts. The top ply of fabric can, however, be retarded relatively to the bottom ply by friction forces developed against the presser foot.

It is an object of this invention to provide a low inertia presser device for a sewing machine comprising an assembly of simple parts which do not require accurate tolerances therebetween.

Another object of this invention is to provide a presser device for a sewing machine which coacts in a novel manner with a drop feed mechanism of a sewing machine to minimize the friction forces developed by the top ply of work fabrics against the presser foot so that optimum uniformity of advance of top and bottom plies of work fabric can result.

3,495,566 Patented Feb. 17, 1970 Summary of the invention The objects of this invention are attained by means of a sewing machine presser device in which the presser bar and the force of the main presser bar spring which acts between the machine frame and the presser bar are limited as to movement toward the work support by a stop means. Interposed between the presser bar and the presser foot is a U-shaped leaf spring of which the spaced horizontal limbs are secured one to the presser bar and the other to the'presser foot at points in substantial alignment with the lengthwise axis of the presser bar. Deformation of the leaf spring during rise of the feed dog causes the presser foot to move in the direction of feed of the work fabrics, and therefore, transport of the work fabrics during advance of the feed dog is opposed by kinetic friction between the top ply and the presser device. The kinetic friction being of a lower value than the static friction which must be overcome when a conventional presser device is used, the retardation of the top ply by the presser foot is minimized with this invention and unformity of feed of the plies is enhanced.

Description of the drawings With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the device, combinations, and arrangements of parts hereinafter described and illustrated in the accompanying drawing of a preferred embodiment in which:

FIG. 1 represents a head end elevational view of a sewing machine partly in cross section illustrating the presser device of this invention in cooperation 'with a drop feed mechanism,

FIG. 2 is a disassembled perspective view of the presser foot and the auxiliary leaf spring support therefor, and

FIG. 3 is a fragmentary elevational view showing the presser foot with the feed dog and illustrating in phantom lines the position to which the presser foot moves in the direction of work feed during the rise of the feed dog. For the purposes of illustration, the phantom line position is somewhat exaggerated.

Referring to the drawings, FIG. 1 illustrates portions of a sewing machine as viewed from the head end and includes a sewing machine bed 11 formed with an opening 12 covered by a throat plate 13 which is formed with slots 14 upwardly through which operates a feed dog. The feed dog 15 forms a part of a conventional drop feed mechanism for sewing machines, which is also referred to in the art as a four-motion work feeding mechanism. The feed dog is carried by a feed bar 16 pivoted as at 17 to a rock arm 18 on an oscillating feed advance shaft 19 which imparts advance and return movements to the feed dog. At the opposite extremity the feed bar is pivoted as at 20 to link 21 pivotally connected as at 22 to a rock arm 23 of an oscillating feed lift rock shaft 24 which imparts rising and falling motion to the feed dog. The combination of such advance and return movements together with the rising and falling movements of the feed dog results in a path of motion of the feed dog in an oval shape as indicated at 25 in FIG. 3.

The throat plate 13 is also formed with an aperture (not shown) to accommodate endwise reciprocation of a needle which is carried by a needle bar 31 in bushings in a bracket arm 32 cantilevered over the bed 11 as is conventional in sewing machine frame construction. Also supported in a bushing 33 in the bracket arm 32 for lengthwise sliding movement therein is a presser bar 34. At the upper extremity,the presser bar is formed with an axial bore 35 which accommodates a locating pin 36 formed between its ends with a flange 37 which abuts the upper extremity of the presser bar 34. The locating pin 36 above the flange 37 extends within the coils of a main presser spring 38 which also embraces a locating pin 39 depending from an adjusting screw 40 threaded into the bracket arm 32. Secured to the presser bar 34 as by a set screw 41 is a collar which may be formed with a lateral extension 43 slideably constrained against the bracket arm to prevent rotation of the presser bar. The collar 42 in the present invention serves in an additional capacity to limit downward movement of the presser bar 34 under the action of the main presser spring 38. To this end a wire brackett 44 is formed with a loop 45 encircling the presser bar beneath the collar 42 and with a loop 46 encircling a pin 47 projecting from a presser lifting lever 48 which is provided on a fulcrum screw 49 exteriorly of the bracket arm. Also pivoted exteriorly of the bracket arm on a fulcrum screw 50 is a manual presser lifting bell crank 51 which abuts beneath the presser lifting lever 48. When the bell crank 51 is turned to the position as shown in FIG. 1 which the presser bar is lowered, the bell crank 51 determines a stop position by way of the wire bracket 44 dictating the lowest position in which the presser bar may move.

The lower extremity of the presser bar 34 is formed with a plain cylindrical portion above which the presser bar is formed with screw threads 61 which accommodate a locking and adjusting nut 62. The presser device of this invention is secured to the lower extremity of the presser bar by means of a split clamp 63 adapted to embrace the plain cylindrical portion 60 at the presser bar extremity and to be secured thereon by a clamp screw 64. The locking and adjusting nut 62 serves to provide an adjustable abutment for locating the position of the split clamp 63 accurately on the cylindrical portion of the split clamp 63 accurately on the cylindrical portion '60 of the presser bar. The split clamp 63 is formed with the threaded hole 65 which accommodates a headed fastening screw 66 which together with a washer 67 provide a fastening means by which a first limb 68 of U- shaped leaf spring 69 may be secured to the presser bar. The first limb 68 of the leaf spring is preferably formed with an open slot 70 to accommodate a fastening screw 66 with provision for a limited adjustment of the leaf spring relatively to the presser bar.

The leaf spring 69 is formed with a curved central portion 71 and with a second limb 72 extending substantially parallel to the first lim-b 68. Secured to the second limb 72 of the leaf spring as by fastening screws 73 and located between the

spring limbs

68 and 72 is a block 74 which is formed with an upwardly open slot 75. The screws 73 pass through clearance openings 76 in the second limb 72 of the leaf spring and threadedly engage tapped holes 77 in a bearing block 78 beneath the second leaf spring limb 72. The fastening screw preferably orients the slot in the block 74 so that the slot extends toward the curved central portion 71 of the leaf spring. The bearing block 78 is formed with a transverse bore 79 to accommodate a fulcrum pin 80 by whicha sewing machine presser foot 81 is pivoted with respect to the presser bar. The presser foot is preferably formed with a pair of spaced

projections

82, 83, the projection 83 being formed with a clearance aperture 84 for the fulcrum pin and the projection 83 being formed with a tapped hole 85 into which the threaded extremity of the fulcrum pin 80 engages.

The headed fastening screw 66 by which the leaf spring 69 is secured to the presser bar is formed with a depending cylindrical extension which is slideably accomodated within the slot 75 of the block 74 secured to the second limb of the leaf spring. The cylindrical extension 90 and the slot 75 of the block 74 cooperate to provide a lateral guide means which will not inhibit limited vertical movement of the presser foot relatively to the presser bar, nor will it inhibit movement of the presser foot in the direction of feed of the work relatively to the presser bar.

Since downward movement of the presser bar 34 is limited by the stop means acting beneath the collar 42 on the presser foot bar, the pressure of the main presser spring 38 is prevented from acting directly on the presser foot 81, and only the auxiliary leaf spring 69 acts to urge the presser foot downwardly during the normal operation of the sewing machine, that is, unless an extraordinarily thick cross seam or the like is encountered. As a consequence during normal operation of the sewing machine, only the presser foot, the

blocks

78 and 74, and a portion of the spring 6 9 will move upwardly during the rise of the feed dog 15. Since the entire presser bar and main presser spring arrangement will not move during normal sewing and since the parts which do move posses very low mass, a minimum of inertia forces will be developed and the presser foot will follow the movements of the feed dog with a minimum of overthrow.

In addition to following the movements of the feed dog closely which will produce optimum consistency of stitch length in the resulting feed of the work fabrics, the presser device of this invention also operates in a unique fashion to minimize the drag of the presser device on the top ply of Work fabrics being sewn so that optimum uniformity of feed between the upper and lower plies of work fabric being stitched will be provided. The minimizing of drag exerted by the presser foot of this invention on the top ply of work pieces is believed to result from the fact that during the rise of the feed dog at the outset of each work feeding stroke, the presser foot, in addition to being raised by the feed dog, will also partake of an increment of movement in the direction of feed of the work. This increment of presser foot movement relatively to the work will overcome the static friction which exists between the top ply of work fabrics and the presser foot, so that as work is advanced by the feed dog only the kinetic friction between the top ply and the presser foot will be effective. Since the kinetic coefficient of friction is of lower value than the static coeflicient of friction, such initial presser foot movement in the direction of feed at the outset of each feeding stroke is believed to account for the superior uniformity of feed of the plies of fabric which is the object of this invention.

Having set forth the nature of this invention, what is claimed herein is:

1. A presser device for a sewing machine including a work support and a presser bar having a lengthwise axis extending substantially perpendicular to the work support in said sewing machine, said pressure device comprising a U-shaped leaf spring including spaced substantially parallel first and second limbs joined by a curved central portion of said spring, fastening means for attaching the first limb of said leaf spring to said presser bar in a position extending substantially perpendicular to the lengthwise axis of said presser bar, a presser foot adapted for engagement with said work support, and securing means for attaching said presser foot to the second limb of said leaf spring.

2. A presser device as set forth in claim 1 in which said securing means for said presser foot engages said second limb of said leaf spring at a distance from said curved central portion thereof which is greater than the distance from said curved central portion to said fastening means on said first limb of said leaf spring.

3. A presser device as set forth in claim 1 in which said fastening means includes a guide pin extending substantially parallel to the lengthwise axis of said presser bar, and in which said securing means includes a block formed with a guide pin embracing slot, said slot extending along said second limb of said leaf spring toward said curved central portion thereof.

4. In combination with a sewing machine having a frame including an apertured work support, a drop feed mechanism inside said frame including a feed dog operating upwardly through said apertured work support, a

presser bar endwise slideably mounted in said frame above said work support, a main presser spring biasing said presser bar toward said work support, and stop means limiting movement of said presser bar toward said work support, a presser device carried by said pressed bar and including a leaf spring, fastening means securing a first extremity of said leaf spring to said presser bar, a curved central portion formed on said leaf spring positioning a second extremity thereof in spaced relation beneath and substantially perpendicular to said presser bar, a presser foot engageable with said work support and with said feed dog operating therethrough, and securing means for attaching said presser foot to said second extremity of said leaf spring.

References Cited UNITED STATES PATENTS 10 PATRICK D. LAWSON, Primary Examiner