US2088560A - Sewing machine - Google Patents

Description

F. PARRY SEWING MACHINE July 27, 1937.

Filed July 5, 1936 Fran/i Parry Patented July 27, 1937 UNITED STATES PATENT OFFICE SEWING MACHINE Frank Parry, Bridgeport, Conn., assignor to The Singer Manufacturing Company, Elizabeth, N. L, a corporation of New Jersey Application July 3, 1936, Serial No. 88,725

6 Claims.

This invention relates to rotary hook and thread-case devices for sewing machines and more particularly to cup-shaped rotary hooks of the horizontalaxis type makinga plurality of rota tions for each complete reciprocation of the usual sewing machine needle, which hooks have a loop-seizing beak arranged to cast the take-up limb of theseized needle-thread loop in front of the rim of the hook-body and the work-limb of said thread-loop in rear of the thread-case within the hook-body; a hook of this type being disclosed in the patents to E. B. Allen, No. 1,155,120, Sept. 28, 1915, and to J. S. Finch, No. 1,196,940, Sept. 5, 1916.

Rotary hooks of the type referred to are commonly termed cast-off hooks and have a circular raceway in which is journaled the peripheral bearing rib of a thread-case carrier restrained against rotation with the hook proper. The thread-case contains a mass of thread about which the needle-thread loops are cast by the hook, after which the usual needle-thread takeup comes into action to draw the loop up to the work and to set the stitch.

At high speeds of operation of a sewing machine having a cast-01f type of rotary hook, the velocity of the hook and therefore of the threadloop expanded thereby is so great that, combined with the action of the take-up to draw up the thread-loop, the take-up limb of said threadloop flies violently against the under sides of the throat-plate and the feed-dog, said limb being often caught in the usual feed-dog slot in the throat-plate. When thus thrown clear of the rotary hook, the take-up limb of the thread-loop is free to twist and kink, resulting in threadbreakage and the formation of undesirable loops and knots at the under side of the work.

The present invention has for its object to provide means for controlling the take-up limb of the thread-loop cast off by the hook and attains this object by interposing a barrier in the path of the cast-off loop, said barrier being disposed so as to limit the flying-off movement of the threadloop and to act upon said thread-loop to minimize twisting and kinking thereof.

With the above and other objects in view, as will hereinafter appear, the invention consists in the thread-loop controlling device hereinafter described in connection with the accompanying drawing which illustrates a preferred embodiment of the invention and in which:

Fig. 1 is a front end elevation of a portion of a sewing machine containing the thread-loop controller. Fig. 2 represents in perspective and partly in section, the rotary hook and the threadcase rotation restraining means arranged to provide a thread-loop controller. Fig. 3 represents a sectional view substantially on the line 3-3 of Fig. 1 and illustrates the rotary hook and the thread-case rotation restraining means in rear side elevation. Fig. 4 represents a perspective view of the thread-case carrier. Fig. 5 represents a perspective view of the thread-case. Fig. 6 is a bottom plan view of the throat-plate.

Referring to the drawing, the sewing machine has the usual work-supporting bed-plate I upon which is secured a throat-plate 2 provided with feed-slots 3 and a needle-aperture 4 which is preferably chamfered at the under side of the throat-plate. The work is advanced by a dropfeed mechanism including a feed-dog 5 operating through the throat-plate feed-slots 3, the rising movements of said feed-dog being opposed by the usual spring-depressed presser-foot 6.

Cooperating with the usual vertically reciprocatory needle 1 is a horizontal-axis rotary hook 8 of the cast-off type. The hook 8 is carried by a horizontally disposed actuating shaft 9 rotatably journaled in a bearing-bushing 10 secured in a 25 lug l I depending from the bed-plate I, said shaft 9 being driven in any usual or suitable mamier to perform two rotations for each complete reciprocation of the needle 1.

The rotary hook 8 has a cup-shaped body pro- 30 vided with a beak I2 of which the outer edge is inclined toward the base of the hook-body, i. e., the inclination of the beak I2 is such that its point extends into proximity to a needle-guard flange l3 suitably secured to the hook-body at the shaft side thereof. In its reciprocating movement, the needle 1 passes between the hook-beak l2 and the guard-flange l3, and it will therefore be understood that the hook-beak l2 has a path of movement to seize the needle-thread loop at the 40 side of the needle 1 remote from the hook-shaft side of the'needle.

\ Adjacent to the throat I2 of the hook-beak l2, the hook-body has a thread-loop cast-off face [4 which is concavely inclined in a manner well known toward the outer rim l5 of the hook-body and functions to cast the limb t of the threadloop leading to the needle onto said rim. The limb t of the thread-loop leading through the needle-eye to the usual take-up is commonly termed the take-up limb of said loop and will hereinafter be so termed, it being of course understood that the rotary hook seizes the thread-loop at the work-limb to side of the needle.

The rotary hook 8 is provided with the usual 55 raceway in which is journaled the peripheral bearing-rib 16 of a supporting base or carrier i? for a thread-case l8, said thread-case being detachably secured to the supporting pin of its carrier by the usual latch 19. The bearing-rib it is partly cut away to provide the usual loopdetaining spur 28 defining one end of a threadclearance gap 21 in said bearing rib. The threadcase it contains a mass of thread of which a length 7: passes upwardly through the throatplate aperture 6 and to the work.

When the hook-beak l2 seizes the needlethread loop by passing between the needle 1 and the work-limb w of the thread-loop carried by 1.3 said needle, the lower end of said thread-loop is caught by the spur 20 of the thread-case carrier bearing-rib l6. Considered as extending from the work, the thread-loop now passes under the hook-body rim across the bearing-rib gap 21, about the spur 20 and along the inner face of the bearing-rib under the hook-body rim, about the hook-beak throat l2 and over the outer face of the hook-body to the needle. It will therefore be understood that the work-limb w is immediately carried onto the inner face of the threadcase carrier and that it is passed along said inner face in the subsequent expansion of the loop by the continued rotation of the hook.

As above indicated, the take-up limb t of the thread-loop is'cast onto the outer rim of the hook-body by the cast-off face ll of said body and is therefore cast across the outer face of the thread-case 18, the thread required being drawn through the needle-eye by the hook. After the hook has been rotated approximately 180 beyond loop-seizing position, the usual sewing machine take-up mechanism begins its action to draw up the loop and to set the stitch, by pulling upwardly the take-up limb t of the thread-loop. 40 The take-up action is so timed that the threadloop hugs the thread-case I 8 during the major portion of the loop drawing-up movement, at the slower speeds of operation of the machine.

However, at higher speeds of operation of the 45 machine, the control of the cast-off thread-loop is lost, because of the velocity attained by the thread-loop in the cast-off position of the hook, combined with the thread-pulling action by the take-up upon the free outer or take-up limb of 50 the loop. At high speeds of operation, the free take-up limb t flies so violently from the hook that, it frequently engages the under side of the throat-plate or becomes jammed in the feed-dog slots in the throat-plate. This action is likely 55 to result in thread-breakage, as will be apparent. In another type of rotary hook, commercially well known, the take-up limb of the thread-loop is cast about the inner face of the thread-case, so that it is confined and remains under control. 60 However, in the present cast-01f type of hook it is the work-limb of the thread-loop which is confined, while the take-up limb is free.

It is well known that certain threads have a tendency to twist or kink in the formation of 65 lock-stitches. When the thread-loop or a limb thereof is thrown clear of the hook and its threadcas'e, it is free to respond to this twisting and kinking tendency, resulting in the formation of loops and knots, or thread-breakage. In order 70 to obviate these difliculties, a barrier is provided for controlling the cast-off thread-loop.

The present thread-case carrier IT has the usual segmental wall 22, overhanging the threadcase l8 and provided with an upwardly and in- 75 wardly extending stop-finger 23. The front edge 23' of this stop-finger preferably lies substantially in the vertical plane containing the needle path of reciprocation and transverse to the line of feed. Secured by screws 26 to the under side of the throat-plate 2 is a dog-plate 25 provided with arms 23 and 21 extending downwardly from the throat-plate. The arm 2% is curved upwardly toward its free end which is disposed for engagement by the front edge 23' of the stop-finger 23. The hook 8 rotates in a direction such that the stop-finger 23 is induced normally to engage the dog-arm 26.

The dog-arm 21 is preferably substantially straight and is inclined downwardly from the throat-plate at an angle of approximately 30 to extend toward the outer rim of the hook-body from beyond the thread-case IS. The free end of the dog-arm 21 is disposed for engagement by the rearward edge 23" of the stop-finger 23, thereby restraining the thread-case carrier l1 against rotation in a direction opposite to the direction of rotation of the rotary hook 8.

When the rotary hook beak 12 has advanced approximately 180 beyond loop-seizing position, i. e., to cast-oil position, the take-up limb t passes between the stop-finger 23 and the dog-arm 26, so that at the time when the take-up begins its action to draw up the loop, the length of the free limb is substantially equal to the distance from the throat-plate needle-aperture to the throat of the hook-beak. While the work-limb w follows the take-up limb t in its flying off movement, at high speed operation of the machine, said worklimb is confined between the inner face of the bobbin-carrier l1 and the base of the hook-body.

In addition to functioning as a stop for the thread-case carrier, the arm 21 is so arranged as to act as a barrier to the thread-loop in its flying-off movement. To that end, the arm 21 preferably extends downwardly sufliciently to intersect a horizontal tangent to the segmental wall 22 of the thread-case carrier I 1. In view of the above noted angle of inclination of the arm 21 and the described spacing of its free end from the throat-plate, said arm is disposed so as to baifle the thread-loop from engaging the throat-plate. Furthermore, as illustrated in Fig. 1, the arm 21 is preferably so arranged as to extend in a direction toward a point substantially midway of the last quadrant of rotation of the rotary hook 8. By means of this disposition of the arm 21, the flying-off limb t of the thread-loop engages said arm 21 substantially medianly of the length 01' said limb t, thereby doubling said limb about said arm. This occurs more particularly at a time when the rotary-hook beak I2 is entering the last quadrant of its rotation, it being approximately at this time that the cast-ofl loop-limb t particularly requires control. The doubling of the loop-limb t about the arm 21 retards the twisting and kinking tendency long enough to enable the take-up to sufliciently shorten the loop before the twisting and kinking can actually occur. It will therefore be understood that the specially arranged arm 21 has a two-fold loopcontrolling function, in addition to serving as a stop for the bobbin-carrier.

Having thus set forth the nature of the invention, what I claim herein is:-

1. In a sewing machine, a vertically reciprocatory thread-carrying needle, 9, work-support, a horizontal-axis rotary hook disposed below said work-support, a thread-case journaled in said rotary hook and restrained against rotation therewith, said rotary hook being constructed and arranged to'cast the take-up limb of the needlethread loop across the outer face of said threadcase, and a barrier spaced from and disposed at the loop-cast-off side of said rotary hook in position to limit flying-off movement of said takeup limb of the thread-loop from said hook.

2. In a sewing machine, a vertically reciprocatory thread-carrying needle, a work-support, a rotary hook-shaft disposed horizontally below said work-support, a rotary hook carried by said shaft and having a loop-seizing beak adapted to enter the needle-thread loop at the side of said needle opposite to the hook-shaft side thereof, a thread-case Journaled in said rotary hook and restrained against rotation therewith, and a stationary needie-thread-loop barrier spaced from and disposed at the loop-cast-ofl side of said rotary hook in position to baflie the threadloop from flying against said work-support.

3. In a sewing machine, a vertically reciprocatory thread-carrying needle, 9. work-support, a cast-oil. rotary hook disposed below said worksupport, a thread-case journaled in said rotary hook and restrained against rotation therewith, said rotary hook being constructed and arranged to cast the take-up limb of the needle-thread loop across the outer face of said thread-case, and a stationary barrier disposed at the loop-cast-ofi side of said rotary hook substantially medianly of the fourth quadrant of-rotation of the rotary hook after seizure of the needle-thread loop, thereby to limit flying-01f movement of said takeup limb of the thread-loop from said hook and thread-case.

4. In a sewing machine, a vertically recipro- 'catory thread-carrying needle, a work-support, a cast-oi! rotary hook disposed below said worksupport, a thread-case journaled in said rotary 40 hook and restrained against rotation therewith,

said rotary hook being constructed and arranged to cast the take-up limb of the needle-thread loop across the outer face of said thread-case, and a stationary thread-loop-controlling arm extending downwardly from said work-support toward the outer rim of the hook at an inclination of approximately to said work-support, said am terminating substantially medianly of the fourth quadrant of rotation of the rotary hook from loop-seizing position.

5. In a sewing machine, a vertically reciprocatory thread-carrying needle, a work-support, a 'rotary hook-shaft disposed horizontally below said work-support, a rotary hook carried by said shaft and having a loop-seizing beak adapted to enter the needle-thread loop at the side of said needle opposite to the hook-shaft side thereof, a thread-case journaled in said rotary hook and provided with a stop-finger, and an arm extending downwardly from said work-support in position for engagement by said stop-finger substantially medianly of the fourth quadrant of rotation of said rotary hook from loop-seizing position.

6. In a sewing machine, a vertically reciprocatory thread-carrying needle, a work-support, a horizontal-axis rotary hook disposed below said work-support, a thread-case journaled in said rotary hook and restrained against rotation therewith, said rotary hook being constructed and arranged to cast the take-up limb of the needle-thread loop across the outer face of said thread-case, and a thread-loop controlling arm depending from said work-support at the loopcast-ofl side of said rotary hook, said arm terminating at a point substantially in a horizontal line tangential to the upper face of said threadcase.

FRANK PARRY.

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