US2470931A - Sewing machine - Google Patents

Description

A. A. JENNINGS SEWING MACHINE May 24, 1949.

2 Sheets-Sheet 1 Filed May 10, 1946 I I I I I I IL I I .I I n I I I INVENTOR;

HIS ATTORNEYS.

A. A. JENNINGS May 24, 1949.

SEWING MACHINE 2 Sheets-Sheet 2 Filed May 10, 1946 INVENTQRIV I HIS ATTORNE S.

Patented May 24, 1949 UNITED SEWING MACHINE Alvin A. Jennings, Lebanon, Mo., assignor to Rice- Stix Dry Goods Company, St. Louis, Mo., a corporation of Missouri Application May 10, 194.6, Serial No. 668,849

(Cl. l12-253) 6 Claims.

This invention relates to sewing machines, particularly lock-stitch sewing machines of the kind comprising a throat plate, a feed dog, a presser foot, a needle working through a hole in the throat plate and a revolving sewing hook for passing the looking or bobbin thread through the loop of needle thread to form therewith a lock stitch. The principal object of the present invention is to prevent unthreading of the needle, breakage of the thread and/or wrapping of the thread around the rotary sewing hook when the machine is operatedwithout any work under the presser foot or before the work is fed far enough beneath the presser foot to be engaged by the needle. Other objects are to provide for cutting the thread on the presser foot after the sewing operation is completed and to provide for simplicity and economy of construction and compactness of design.

The present invention consists in clamping between the throat plate and the heel of the presser :ioot the entwined portions of the needle and bobbin threads that are drawn rearwardly over said throat plate when the work passes from beneath said presser foot; it also consists in releasing the clamped portions of said threads after the work is fed beneath the presser foot far enough to be engaged by the needle; it also consists'in providing the heel of the presser foot with a knife edge for severing the threads after the sewing operation is completed; and it also consists in the parts and in the arrangements and combination of parts hereinafter described and claimed.

In the accompanying drawings, which form part of this specification and wherein like symbols refer to like parts wherever they occur,

Fig. 1 is a fragmentary front elevational view of a sewing machine embodying my invention,

Fig. 2 is a side elevational view of the parts shown in Fig. 1,

Fig. 3 is a horizontal cross sectional view on the line 33 in Fig. 2.

Fig. 4 is a view similar to Fig. 2 showing the ,bed, throat plate, presser foot and feed dog in motion feed dog 6 for feeding said work rearwardly beneath said presser foot, said machine also includes a vertically reciprocating needle I, which operates through the forked front end portion 8 of the presser foot 4 and a hole 9 in said throat plate and has a transverse hole [0 through which the needle thread ll extends, and a rotary shuttle l2 having a hook l3 for passing the bobbin thread I4 through the loop of needle thread so as to form a lock stitch. The feed dog 5 has three spaced parallel rows of feed teeth, two side rows 15 and a middle row [6, along the upper top thereof that extend rearwardly beneath the presser foot 4 and are disposed in similarly spaced elongated side and middle slots I] and I8, respectively, in the throat plate 3, the feed dog being actuated by a feed bar I 9 to move said roWS of feed teeth upwardly and rearwardly in said slots into engagement with the underside of the work 5 to feed the latter rearwardly beneath said presser foot. The type of lock-stitch sewing machine thus far described is well known and it is considered unnecessary to illustrate it in detail.

As shown in the drawings, the two side rows E5 of feed teeth and the side slots l1 therefor are relatively long and extend substantially from end to end of the presser foot 4 on opposite sides of the needle hole 9 in the throat plate 3, while the middle row l6 of feed teeth and the middle slot [8 are relatively short and are located rearwardly of said needle hole and terminate short of the rear end of said presser foot, whereby the rear end portion of said presser foot overhangs the portion of the throat plate rearwardly of the short middle slot and is adapted to clamp the entwined loose ends of the needle thread II and the bobbin thread l4 down on the throat plate rearwardly of said short middle slot after the sewing operation is completed and the work moves rearwardly clear of said presser foot. As shown in the drawings, the presser foot 4 is preferably supported for rocking movement on a horizontal pivot 20 disposed crosswise of the line of work feed and has an upwardly curved front end portion 2| and an upwardly curved heel portion 22, thereby permitting the work to be easily inserted beneath the front end of said presser foot and causing the heel portion thereof to increase its pressure or clamping action on the threads when the work is entered beneath the curved front end portion of said presser foot. As shown in the drawings, the rearwardly and upwardly inclined heel or rear end portion 22 of the presser foot 4 terminates at its u per end in a knife edge 23.

By the arrangement described, when the sewing operation has been completed and the work ,5 has been moved rearwardly by the feed dog 6 clear of the rear end of the presser foot 4, the needle and bobbin threads extend rearwardly across the top of the throat plate 3 and beyond the rear end of the presser foot and may be severed from the work by pressing them against the knife edge portion 23 of said presser foot. In this position of the parts, the end portions of the needle and bobbin threads lie beneath the presser foot 4 and are clamped by the rear end or heel portion 22 thereof down on the portion of the throat plate 3 located rearwardly of the short middle row of the feed teeth receiving slot l8 thereof. Thus, if the machine is operated without any work beneath the presser foot or before work is entered beneath the forward end thereof far enough to be engaged by the needle, the ends of the needle and bobbin thread are firmly held by the heel portion of the presser foot, thereby preventing the needle from becomin unthreaded and the bobbin thread from wrapping around the hook or one or both threads from breaking when the machine is operated. When the work is entered beneath the upwardly curved front end portion 2| of the pivoted presser foot d, the pressure of the heel portion 22 thereof on the needle and the bobbin threads is increased, thus firmly holding said threads until the work is in position to be engaged by the needle I. In this position of the work, the heel portion 22 of the presser foot 4 lifts off the needle and bobbin threads and releases them, thereby permitting the stitch forming operation to proceed. After the sewing operation is completed, and the work has moved rearwardly clear of the presser foot, the presser foot moves downwardly and the heel portion thereof again clamps the two needle and bobbin threads lying therebeneath tightly against the portion of the throat plate located rearwardly of the short middle feed teeth receiving slot I8 therein. The two threads are then severed by pressing them against the knife edge 23 on the heel portion 22 of the presser foot 4.

The hereinbefore described arrangement has several important advantages. It is simple and inexpensive and can be quickly and easily incorporated in existing sewing machines without material alteration thereof. It eliminates thread breakage and unthreading of the needle between completion of sewing of one work piece and starting of the next piece; and it dispenses with the need for separate cutting devices for severingthe thread from the finished work.

What I claim is:

1. In a sewing machine of the kind described having a needle, a single longitudinally tiltable presser foot extending forwardly and rearwardly of said needle, a feed dog with a row of feed teeth disposed beneath said presser foot, and a throat plate having a slot therein for said feed teeth, the

improvement which consists in aranging said slot with its rear end disposed forwardly of the rear end portion of said presser foot, whereby the rear end portion of said presser foot is adapted when the work passes from beneath said presser foot and draws the needle and bobbin threads rearwardly over the throat plate to clamp said threads to the portion of the throat plate located rearwardly of said slot and thus prevent unthreading of the needle, retraction of the bobbin thread or breakage of said threads when the needle is operated without the work in position to be engaged thereby.

2. The combination set forth in claim 1 wherein a further improvement consists in providing said presser foot with an upturned rear end portion that terminates at its free upper edge in an upstanding knife edge against which said threads may be pressed to sever them from the i work after it passes from beneath the presser foot.

3. The combination set forth in claim 1 wherein further improvements consist in mounting said presser foot for longitudinal rocking movement and in curving the front and rear end portions of said presser foot upwardly, whereby the downward pressure of the rear end portion of said presser foot on said threads is increased when the work is forced against the upwardly curved front end of said presser foot, and in forming along the free transverse upper edge of the upwardly curved rear end portion of said presser foot an upstanding knife edge against which said threads may be pressed to sever them from the work after it passes from beneath the presser foot.

4. In a sewing machine of the kind described having a needle, a single longitudinally tiltable presser foot extending forwardly and rearwardly of said needle, a feed dog with side rows of feed teeth disposed beneath said presser foot and extending substantially from front to back thereof and with a middle row of feed teeth located rearwardly of said needle, and a throat plate having side and middle slots therein for said rows of feed teeth, the improvement which consists in arranging said middle slot with its rear end disposed forwardly of the rear end of said presser foot, whereby the rear end portion of said presser foot overhangs said throat plate rearwardly of said middle slot and is adapted when the work passes from beneath said presser foot and draws the needle and bobbin threads rearwardly over the throat plate to clamp said threads to the portion of the throat plate located rearwardly of said middle slot and thus prevent unthreading of the needle, retraction of the bobbin thread or breakage of said threads when the needle is operated without the work in position to be engaged thereby.

5. The combination set forth in claim 4 wherein a further improvement consists in providing said presser foot with an upturned rear end portion that terminates at its free upper edge in an upstanding knife edge against which said threads may be pressed to sever them from the work after it passes from beneath the presser foot.

6. The combination set forth in claim 4 wherein further improvements consist in mounting said presser foot for longitudinal rocking movement and in curving the front and rear end portions of said presser foot upwardly, whereby the downward pressure of the rear end portion of said presser foot on said threads is increased when the work is forced against the upwardly curved front end of said presser foot, and in forming along the free transverse upper edge of the upwardly curved rear end portion of said presser foot an upstanding knife edge against which said threads may be pressed to sever them from the work after it passes from beneath the presser foot.

ALVIN A. JENNINGS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,251,352 De Voe Dec. 25, 1917 1,765,342 Lutz June 17, 1930 2,318,843 Enos May 11, 1943 2,372,318 Enos Mar. 27, 1945

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