US3793969A

US3793969A - Presser bar pressure control modules

Info

Publication number: US3793969A
Application number: US00294725A
Authority: US
Inventors: K Adams
Original assignee: Singer Co
Current assignee: SSMC Inc
Priority date: 1972-10-03
Filing date: 1972-10-03
Publication date: 1974-02-26
Anticipated expiration: 1991-02-26
Also published as: AU6058773A; CA982877A; GB1429385A; CH565883A5; IT993442B; BR7307580D0; SE405485B; FR2201687A5; DE2349290A1

Abstract

A presser bar pressure control module which is mounted on a plate separable from the head of the sewing machine containing the presser bar. A mounting plate supports a cam and cam follower operatively connected with a pivotable lever attached to a stud also journaled on the mounting plate. The end of the stud protruding through the other side of the mounting plate is attached to one end of a resilient member the other end of which presses against the presser bar to urge the presser foot attached thereto into contact with the work material. Turning the cam alters the torque impressed on the resilient member thereby to alter the force which the presser foot exerts on the work material.

Description

United States Patent Adams PRESSER BAR PRESSURE CONTROL MODULES [75] Inventor: Kenneth D. Adams, Madison, NJ.

[73] Assignee: The Singer Company, New York,

[22] Filed: Oct. 3, 1972 [21] Appl. No.: 294,725

[52] US. Cl. 112/235 [51] Int. Cl D05b 29/02 [58] Field of Search 112/235-251, 254; 74/89, 99 R [56] v References Cited UNITED STATES PATENTS 3,303,804 2/1967 Lesort 112/235 3,534,698 10/1970 Graham 112/235 Primary Examiner.lames R. Boler Assistant Examiner-Peter Nerbun Attorney, Agent, or Firm-Marshal] J. Breen; Chester A. Williams, Jr.; Robert E. Smith 5 7 1 ABSTRACT A presser bar pressure control module which is mounted on a plate separable from the head of the sewing machine containing the presser bar. A mounting plate supports a cam and cam follower operatively connected with a pivotable lever attached to a stud also journaled on the mounting plate. The end of the stud protruding through the other side of the mounting plate is attached to one end of a resilient member the other end of which presses against the presser bar to urge the presser foot attached thereto into contact with the work material. Turning the cam alters the torque impressed on the resilient member thereby to alter the force which the presser foot exerts on the work material.

4 Claims, 4 Drawing Figures PATENIED FEB26 I974 Fig. 3

PRESSER BAR PRESSURE CONTROL MODULES BACKGROUND OF THE INVENTION The invention relates to a pressure regulating module used to regulate the force exerted by the presser foot of a sewing machine on the work material.

Certain prior art devices have used coil springs mounted on a presser bar extending from the presser foot to the top of the machine in order to provide proper support for the coil spring. The amount of pressure exerted by the presser foot was regulated by a separately mounted regulating means which altered the amount of compression of the coil spring. These devices take up a considerable amount of space and re quire a substantial amount of disassembly to replace, for example, a coil spring.

Also in the prior art are devices wherein the coil spring is mounted in an internal bore in the presser bar, the pressure regulation being obtained again by separately mounted means altering the compression of the coil spring. A shorter presser bar is used in which an upper support is not required. In these devices difficulties have been encountered in that the bore in the presser bar receiving the coil spring must be smooth and well formed to eliminate sticking, sliding friction during machine operation, or cocking of the spring. In mass production these required properties of an internal bore of the presser bar are very difficult and expensive to achieve.

SUMMARY OF THE INVENTION In order to avoid the above undesirable aspects of the prior art devices, this invention was conceived to allow the use of a short presser bar without using an internal bore to contain a coil spring with which to exert force on the presser foot. Instead, a resilient member for exerting this force is supported on a mounting plate attachable to a sewing head adjacent the presser bar. Further, the mounting plate is used to support the other parts of the pressure regulating system which act on the resilient member to vary the force exerted on the presser foot as desired. Thus the entire presser bar pressure regulating system is contained on a mounting plate which may be removed from the sewing machine without requiring removal of the various other parts of the presser system.

The invention is set out in the specification and claims which follow, taken in connection with the appended drawings of a preferred embodiment wherein:

FIG. 1 is an elevational end view of a sewing machine equipped with the preferred embodiment of the present invention and in which the end face plate of the machine has been removed and the lower portion of the presser bar bushing is shown in section;

FIG. 2 'is an enlarged perspective view of the mounting plate having some parts shown in exploded perspective and the cam partially in section to indicate detail and manner of assembly;

FIG. 3 is an enlarged fragmentary cross-sectional view taken substantially along line 3-3 of FIG. 1;

FIG. 4 is an enlarged perspective view of the cam showing the cam surface and a representative indicium on the cam periphery.

DESCRIPTION OF THE INVENTION Referring to FIG. 1 of the drawings, there is shown a head portion 10 overhanging a throat plate 11 in the bed 12 of a sewing machine. A needle bar 13 is supported in the head portion 10 of the sewing machine to be driven in the usual manner. Affixed to the lower end of the needle bar is a sewing needle 14. Also supported in the sewing head 10 is a presser bar bushing 16 which guides a presser bar 17 having affixed to the lower end thereof by means of a screw 18 a presser foot 19. Attached to the other end of the presser bar 17 by screw 22 is a collar 20. A wheel 23 is supported on the screw for purposes to be described later.

A presser bar lifting lever 24 is formed with a presser lifting cam 25 which impinges on a tang 21 projecting from the collar 20 affixed to the presser bar 17.

Also visible in FIG. 1 and in FIG. 2 is a mounting plate 28 attached to the sewing head 10 by mounting screws 29. Clearly visible in FIGS. 2 and 3 is a stud 30 having a shoulder 31 thereon projecting through a hole 32 in the mounting plate 28 such that a slabbed portion 33 on the stud extends through the mounting plate. A lever 37 having a rectangular hole 38 at one end thereof and an offset abutting surface 39 at the other end thereof is received on the slabbed portion 33 of the stud 30 and held by suitably riveting or spinning the stud end (see FIG. 3). On the opposite end of the stud 30 from the lever 37 and spaced from the shoulder 31 is a peripheral groove 34. Also on this end of the stud 30 projecting into the stud up to the shoulder 31 is a spring receiving slot 35.

A cam 41 is supported for turning movement on the mounting plate 28 by means of pivot stud 42. The cam 41 has a shoulder 43 on that side facing the mounting plate 28 to provide clearance between the cam and the mounting plate. The cam is formed with an internal spiral cam track 44 providing detent positions 45 the function of which is to be explained later. The peripheral surface of the cam 41 has a friction surface 46 suitable for finger gripping, and also has indicia one of which is shown at 47 indicative of the presser bar pressure achieved.

A cam follower bell crank 48 is pivoted to the mounting plate 28 adjacent the cam 41 by a second pivot stud 49, and operates in the clearance provided by the shoulder 43 of the cam. A first portion of the bell crank 48 has a turned over lip 50 forming a cam follower which protrudes into the internal cam track 44 of the cam 41. A second portion 51 of the bell crank 48 projects adjacent the abutting surface 39 of the lever 37. At the extremity of the second portion 51 is a lanced out area 52 which receives a screw 53. The tip of the screw 53 impinges on the abutting surface 39 of the lever 37.

The spring receiving slot 35 in the end of the stud 30 receives an inner leg 55 of a spirally coiled spring 56 (see FIGS. 2 and 3). The spirally coiled spring 56 is held in place on the stud 30 by a snap ring 57 received in the peripheral groove 34 of the stud. The outer leg 58 of the spirally coiled spring 56 when assembled in the sewing head 10 rides in the groove of the wheel 23 which is mounted on the screw 22 affixing the collar 20 to the presser bar 17.

In operation, when the mounting plate 28 is affixed in position in the sewing machine head 10, the outer leg 58 of the spirally coiled spring 56 impinges on the wheel 23 supported by the screw 22 attaching the collar 20 to presser bar 17. Referring to FIG. 1, when the cam follower 50, which abuts against the spiral internal cam track 44, is caused to move away from the center of the cam 41 by rotation of the cam, the cam follower bell crank, 48 rotates counterclockwise and causes the lever 37 to rotate clockwise carrying with it the inner leg 55 of the spirally coiled spring 56, thereby increasing the amount of torque stored in the coiled spring. An increase in torque is manifested by a corresponding increase in the force with which the presser bar 17 and presser foot 19 attached thereto presses against the work material. Conversely, rotation of the cam in the opposite direction will decrease the amount of torque stored in the spring 56 and thereby decrease the force with which the presser foot 19 presses against the work material. Discrete steps are provided by the detent positions 45 in the cam track 44 and the proper one may be readily selected by the sewing machine operator viewing the indicia 47 in the periphery of the cam 41. The indicium indicated in FIG. 4 is indicative of daming position. Adjustments to the pressure regulating module to accommodate for manufacturing tolerance in achieving the correct pressure in the darning position can be made by repositioning the screw 53 in the second portion 51 of the cam follower bell crank 48.

The pressure regulating module can be removed by removal of screws 29. The entire pressure regulating system is removed by removal of the mounting plate 28, leaving behind the short presser bar 17, collar 20, screw 22 and wheel 23 supported thereon. Reinstallation of the mounting plate requires the positioning of the outer leg 58 of the spirally coiled spring 56 on to the wheel 23 prior to reinsertion of the screws 29 through the mounting plate 28 and refastening to the sewing machine head 10. It is apparent that the spirally coiled spring 56 could be replaced by a suitably designed leaf spring or beam to accomplish the same objective.

Having set forth the nature of this invention, what I claim is:

l. A pressure regulating module for a sewing machine having a presser bar adapted to have a presser foot secured thereto, and means endwise shiftably supporting the presser bar in the sewing machine, the pressure regulating module comprising:

a. a mounting plate,

b. means for detachably securing said mounting plate to the sewing machine in a predetermined position with respect to said presser bar,

c. resilient means for biasing said presser bar endwise, a support for said resilient means carried on said mounting plate and arranged when said mounting plate is secured in said predetermined position with respect to said sewing machine by said securing means to locate said resilient means in a position impinging on said presser bar,

(1. means for varying the tension in said resilient means comprising a lever and cam follower means shiftably supported on said mounting plate and arranged in cooperative engagement with said resilient means,

e. a cam means supported on said mounting plate and arranged in cooperative engagement with said cam follower means to vary the force with which said resilient means impinges on said presser bar.

2. A pressure regulating module as set forth in claim 1 wherein said resilient means includes a spring spirally wound in one plane, a stud journaled in said mounting plate, means attaching the inner extremity of said spirally wound spring to said stud, and means responsive to the position of said lever for influencing the angular position of said stud.

3. A pressure regulating module as set forth in claim 2 wherein a selectively extensible coupling is provided between said cam means and said lever to increase or decrease the torsional windup of said spirally wound spring for the purpose of calibrating the presser systern.

4. A pressure regulating module as set forth in claim 3 in which said selectively extensible coupling comprises said a cam follower element shiftably supported on said mounting plate, an adjusting screw carried in said cam follower element, and an abutment surface formed on said lever engaging said adjusting screw.

Claims

1. A pressure regulating module for a sewing machine having a presser bar adapted to have a presser foot secured thereto, and means endwise shiftably supporting the presser bar in the sewing machine, the pressure regulating module comprising: a. a mounting plate, b. means for detachably securing said mounting plate to the sewing machine in a predetermined position with respect to said presser bar, c. resilient means for biasing said presser bar endwise, a support for said resilient means carried on said mounting plate and arranged when said mounting plate is secured in said predetermined position with respect to said sewing machine by said securing means to locate said resilient means in a position impinging on said presser bar, d. means for varying the tension in said resilient means comprising a lever and cam follower means shiftably supported on said mounting plate and arranged in cooperative engagement with said resilient means, e. a cam means supported on said mounting plate and arranged in cooperative engagement with said cam follower means to vary the force with which said resilient means impinges on said presser bar.

3. A pressure regulating module as set forth in claim 2 wherein a selectively extensible coupling is provided between said cam means and said lever to increase or decrease the torsional windup of said spirally wound spring for the purpose of calibrating the presser system.