US3727568A

US3727568A - Skip stitch mechanism for sewing machines

Info

Publication number: US3727568A
Application number: US00228026A
Authority: US
Inventors: T Graham
Original assignee: Singer Co
Current assignee: Singer Co
Priority date: 1972-02-22
Filing date: 1972-02-22
Publication date: 1973-04-17
Anticipated expiration: 1990-04-17

Abstract

A sewing machine needle reciprocating mechanism is disclosed including clutch mechanism for releasing the endwise reciprocatory drive for the needle bar intentionally to provide for skipped stitches as for basting or the like, and also to provide for an automatic release of the needle bar drive to prevent needle breakage in case the needle should strike an impenetrable object such as a button or the like.

Description

United States Patent 91 Graham SKIP STITCH MECHANISM FOR SEWING MACHINES [75] Inventor: Thomas G. Graham, Point Pleasant Beach, NJ.

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

[22] Filed: Feb. 22, 1972 [21] App1.No.: 228,026

52 user ..112/221 [51] 1m.c|......, ..D05b69/36 [58] Field of Search ..l12/221,220,219 R,

[56] References Cited UNITED STATES PATENTS 3,471,325 10/1969 Berube 1 12/221 51 Apr. 17, 1973 Scheibel .11 12/221 Basso ..1 12/221 Primary Examiner-H. Hampton-Hunter Attorney-Marshall J. Breen et a1.

57 ABSTRACT A sewing machine needle reciprocating mechanism is disclosed including clutch mechanism for releasing the endwise reciprocatory drive for the needle bar intentionally to provide for skipped stitches as for basting or the like, and also to provide for an automatic release of the needle bar drive to prevent needle breakage in case the needle should strike an impenetrable object such as a button or the like.

' 1 Claim, 2 Drawing Figures PAIENIEU APR 1 71973 gm w SKIP STITCH MECHANISM FOR SEWING MACHINES BACKGROUND OF THE INVENTION Needle bar mechanisms are known in the prior art including releasable clutch means which may be influenced selectively to provide for skipped stitches. These known skip stitch mechanisms require mechanism for actuating the clutch means and do not serve as safety releases to protect the sewing machine operator in case the needle should strike an impenetrable object.

Safety clutches are known in the sewing machine art for interrupting the needle bar drive in the event that the needle strikes an impenetrable-object. These safety release needle bar clutches had not heretofore been organized so as to be selectively operable and, therefore, they have not been heretofore usable to provide basting stitches or other operations requiring predetermined interruption of needle bar reciprocation.

BRIEF SUMMARY OF THE INVENTION It is an object of this invention to provide a sewing machine needle bar mechanism including a single separable driving connection between the needle bar and the needlebar reciprocating mechanism, which separable driving connection serves as a safety device automatically opening when the needle bar meets excessive resistance to endwise movement, together with a means for separating said driving connection at will so that predetermined interruption of needle bar reciprocation may be attained.

DESCRIPTION OF THE DRAWING With the above and additional objects and advantages in view as will hereinafter appear, this invention is illustrated in the accompanying drawing of a preferred embodiment in which:

FIG. 1 represents a side elevational view of the head portion of a sewing machine with the sewing machine frame partly broken away to expose this invention applied thereto, and

FIG. 2 is an enlarged cross sectional view of the separable driving connection between the needle bar and the actuating mechanism therefor, taken substantially along line 2-2 of FIG. I, but shown with the driving connection interrupted.

Referring to the drawing, 11 indicates the bracket arm head portion of a sewing machine frame formed with a web 12 in which a main drive shaft 13 is jour naled. A counterbalance 14 fast on the main drive shaft 13 carries a crank pin 15 which constitutes the operating mechanism for imparting endwise reciprocatory movement to a needle bar 16 journalcd for endwise reciprocatory movement in

bearings

17 and 18 in the bracket arm head 11. At the lower extremity the needle bar carries a needle clamp 19 by which a conventional sewing machine needle 20 may be secured thereto.

The driving connection between the crank pin 15 and the needle bar 16 comprises a drive link 21 formed at one extremity with a boss 22 embracing the crank pin 15 and formed at the opposite extremity with a boss 23 which embraces a drive stud 24 which projects laterally from a block 25 slidable lengthwise along the needle bar 16. The block 25 is formed with a transverse 0 and the clutch pin may also be formed with a pilot pin 36 at the free extremity. The clutch pin is urged toward the right as viewed in FIG. 2 in a position maintaining the pilot pin 36 in an elongate slot 40 in the needle bar accommodate the pilot pin 36, and at the upper extremity the elongate slot 40 joins a transverse notch 41 shaped to accommodate the free extremity of the clutch pin 31.

When the clutch pin 31 is seated in the transverse notch 41 of the needle bar, the driving connection for imparting endwise reciprocatory movement to the needle bar will be effective. If an abnormal resistance to endwise reciprocation of the needle bar is encountered, the clutch pin 31 will be forced out of the transverse notch 41 and the pilot pin 36 will be shifted relatively to the needle bar and along the elongate slot 40. The needle bar 16 will thus be arrested in its endwise reciprocation and needle breakage and the consequent risk of injury to the work or to the sewing machine operator will be averted. The slot 40 and the pilot pin 36 will prevent the needle bar from turning whether or not the driving connection is effective.

A cushion spring 50 is provided on the bracket arm head portion 11 above the needle bar 16 for engagement of the needle bar when the driving connection is interrupted. Because of the cushion spring the needle bar 16 will be constrained substantially in its uppermost position of reciprocation and the separable driving connection will be re-established on the next upstroke of the driving mechanism.

For intentionally interrupting the drive connection for endwise reciprocation of the needle bar, a pawl 60 is pivoted to a support lug 61 on the needle bar 16 and a spring 62 carried by the pawl abuts the needle bar to urge the pawl outwardly from the needle bar. Carried as by a fastening screw 63 on the bracket arm head portion 11 of the sewing machine frame is a leaf spring 64 to which an abutment block 65 is attached as by a screw 66. The leaf spring 64 may be oriented adjacent to or projecting through an aperture 67 in the bracket arm head portion 11 and carries in the vicinity of this aperture a push button 68.

If it is desired to interrupt the needle bar reciprocation purposely as to perform basting stitches or for any other reason, the operator needs simply depress the push button 68 to shift the abutment block 65 into the path of the pawl 60 on the needle bar. On the ensuing rise of the needle bar the latch pawl 60 will deflect past the abutment block 65 and the spring 62 will force the pawl outwardly in a position overlying the abutment block. When the needle bar begins a downwardwork penetrating stroke of reciprocation, the pawl 60 in engagement with the abutment block 65 will provide abnormal restraint to endwise reciprocatory movement and the clutch pin 31 will be forced out of the transverse notch 41 in the needle bar thus to interrupt the driving connection of the needle bar with the needle reciprocating mechanism. Because of the pawl arrangement such needle bar interruption cannot occur during the withdrawal stroke of the needle bar from the work but only upon the needle penetrating stroke. When the push button 68 is released, the needle bar on the next upstroke of the drive mechanism will re-establish driving connection therewith.

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

l. A skip stitch mechanism in a sewing machine having a frame, a needle carrying bar supported in said frame for endwise reciprocation to impart work penetrating and withdrawal strokes to a needle carried thereby, actuating mechanism carried in said frame for imparting endwise reciprocatory movement to said needle bar, said skip stitch mechanism comprising in combination a driving connection between said actuating mechanism and said needle bar which is automatically separable in response to application of a preselected level of resistance to endwise reciprocation of said needle bar, and blocking means between said frame and said needle bar selectively effective to prevent penetrating strokes of said needle bar.

Claims

1. A skip stitch mechanism in a sewing machine having a frame, a needle carrying bar supported in said frame for endwise reciprocation to impart work penetrating and withdrawal strokes to a needle carried thereby, actuating mechanism carried in said frame for imparting endwise rEciprocatory movement to said needle bar, said skip stitch mechanism comprising in combination a driving connection between said actuating mechanism and said needle bar which is automatically separable in response to application of a preselected level of resistance to endwise reciprocation of said needle bar, and blocking means between said frame and said needle bar selectively effective to prevent penetrating strokes of said needle bar.