US2539759A - Reverse stitch attachment for sewing machines - Google Patents

Description

Jan. W, 1951 P. J. STUSTER ETAL REVERSE STITCH ATTACHMENT FOR SEWING MACHINES 2 Sheets-Sheet 1 Filed Jan. 51, 1949 PHM IP 10 SW15 TEQ @EQQGE H: Ems BTEIN,

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Jan. 30, 1951 P. J. STUSTER ETAL REVERSE STITCH ATTACHMENT FOR SEWING MACHINES 2 Sheets-Sheet 2 Filed Jan. 31, 1949 PHILIP a? Srusr a @EO1Q@EZ H fiksram INVENTORS.

lPatented Jan. 30, 1951 REVERSE STITCH ATTACHMENT FOR SEWING MACHINES Philip J. Stuster, Huntington Park, and George Epstein, Los Angeles, Calif.

Application January 31, 1949, Serial No. 73,814

, 4 Claims. (01. 112-410) The present invention relates generally to sewing machines, and more particularly to means for reversing the direction of feed past the needle of the cloth or other material being sewn, in order to produce what is commonly known as a reverse stitch.

It is often desirable. when sewing, to be able to employ the reverse stitch. For example, in finishing off a seam at the edge of a piece of cloth, it is very convenient to be able to reverse momentarily the direction of feed of the cloth as the needle reaches the edge of the cloth, so that the needle moves inwardly a short distance from the and then forward again to and off 'the' edge of the cloth. This forms a convenient and quick method of finishing off the stitching and looking the threads tightly to prevent their ravelling. However, few, if any, of the many sewing machines sold for domestic use are initially made with mechanism permitting this operation. There are also many machines in commercial use which are similarly handicapped.

There are a large number of sewing machines in this country, both in domestic and commercial use, which can profitably be converted or modified by the addition of parts which enable the machine to produce a reverse stitch. Most of these machines are older styles because the average sewing machine has a relatively long life so that it is not replaced by new equipment except at long intervals. Consequently, it is practical to modernize these machines by adding parts or attachments which enable them to operate mor efiiciently and satisfactorily.

Hence, it becomes a general object of our inven tion to devise a mechanism for a sewing machine that makes it possible to reverse the direction of cloth feed in a quick and easy manner.

It is also a general object of our invention to provide an attachment for existing sewing machines which enables them to be converted or modified to perform the additional operation of sewing a reverse stitch.

It is also an object of our invention to devise been attained by making simple but essential changes in the conventional mechanism of a sewing machine for driving the feed dog that advances the cloth or fabric as it is being sewn. The feed dog is driven from themain drive shaft of the sewing machine by a rotating cam that engages the upper end of the fork. The fork is pivotally connected at its lower end to an arm on a rock shaft which is commonly termed the feeder shaft. In the conventional construction the fork is directly pivotally connected to this arm on the rock shaft but in our improved construction we introduce a link that becomes, in effect, a part of the fork and so keeps the pivotal connection to the arm at its original location. The link is held in adjusted position and is movable with respect to the fork in order to make an adjustment of the eifective length of the fork.

This link introduces into the linkage of members driving the feed dog an adjustable means to make" adjustments necessary to overcome oband vertical components of the feeder dog.

stacles inherent in conventional sewing machines as presently designed.

Intermediate its ends, the fork is engaged by a guide that directs the motion of the fork to produce a component longitudinally of the fork. It is the longitudinal component of the fork motion that drives the feeder dog. The rock shaft has a second arm on it to which is connected an arm carrying the feeder dog. The longitudinal component of fork motion oscillates the rock shaft which in turn-produces a longitudinal reciprocation of the feeder dog arm which motion produces the horizontal component of the feeder dog motion. The final motion of the dog is produced by adding a vertical component of motion.

This is derived from an oscillating cam which moves the free end of the feeder dog arm vertically, the oscillating cam being driven from the main shaft by other mechanism.

The guide engaging the fork remains stationary, but according to our invention it is rotatably mounted on the frame of the machine in such a manner that the guide may be moved from a position in which it is inclined in one direction with respect to the longitudinal extent of the fork to a position of opposite inclination. This rotation of the guide changes the timing of the longitudinal component of fork motion with respect to the transverse component; and this shift in phase relationship of the two components is carried on through the drive linkage to effect a simiiar shift in the phase relationship between the horizontal The result of this is to move the feeder dog in the reverse direction through thecycle of its motion.

cifically mentioned herein, are attained will be more readily apparent by reference to the following description and to the annexed drawings, in which:

Fig. 1 is a fragmentary front elevation of a sewing machine showing the manual control for the reverse stitch mechanism;

Fig. 2 is an end elevation of the sewing machine also showing the manual control;

Fig. 3 is a vertical longitudinal median section showing feed mechanism constructed according to our invention to produce a reverse stitch;

Fig. 4 is a vertical section on line l-Q of Fig. 3;

Fig. 5 is a fragmentary section on line 55 of Fig. i; and

Fig. 6 is an exploded view of the slide block and its mounting screw.

Since the sewing machine shown and described herein is a conventional and well-known make of machine, it is not considered necessary to describe in full all its parts. Hence the disclosure is limited as much as possible to those parts directly concerned with the feeding mechanism and operations. It will be understood that, in general, the parts and their movements as described below are conventional and known to persons skilled in the art, except wherein it is specifically pointed out that the parts have been modified or added to in order to eifect certain specific changes in their operation. It will also be understood that our invention is not necessarily limited to any particular type or make of sewing machine, but that its principles may be embodied in mechanism applicable to various makes of machines.

In the drawings, Ill denotes generally the cast frame of a sewing machine upon which is mounted the spool spindle H. The frame includes a bed plate l2 over which the cloth or other material moves as it is being sewn. The needle shaft. the presser foot, and other mechanisms not directly concerned with feeding this cloth or material have been omitted from the drawings for purposes of simplicity. As seen best in Fig. 3, main drive shaft M is journaled in frame l8; and the drive shaft has affixed to it at one end a circular cam I5 which is eccentrically mounted on the shaft, as shown in Fig. 4.

Cam l5 rotates between jaws N5 of fork H, the jaws being spaced apart by the diameter of cam [5 so that the rotation of drive shaft I4 imparts motion to the upper end of fork IT. The lower end of fork l'i has attached to it a link of novel design which connects the fork to arm 2i on rock shaft 22. Rock shaft 22, commonly designated as the feeder shaft, is journaled at its ends in lugs 23 and 2t which are formed as parts of bed plate l2. The shape and construction of link 26 can better be understood if it is known that in the conventional sewing machine the lower end of fork I? is connected directly to the outer end of rock shaft arm 2i by a shoulder bolt or other type of pin connection which allows pivotal movement between the fork and the arm. The object of link 28 is to retain this same pivotal movement without any change in the axis about which such motion occurs, and at the same time to permit a certain limited bodily shift of the fork with respect to arm 2| for adjustments later described.

This has been accomplished by the use of link 20, shown in Figs. 4 and 5. At one end, the link carries a fixed pin 21 which passes through an opening in the end of fork l1 and is clamped therein. The end of fork I? usually has a split collar that can be tightened by means of screw 28 so that link 20 is held firmly in anyselected Lil position with respect to fork [1. Any other suitable means for holding link 20 fixed relative to fork I! may be used. The other end of link 20 is connected to arm 2| by shoulder bolt 30 which carries nut 2! on its inner end. Since link 20 is adapted to fit on existing machines and it is desirable to use shoulder bolt 30 which is used conventionally to connect the fork and arm 2| directly together, the end of link 20 connected to arm 2| is made the same thickness as the lower end of fork H. In this way when nut 3| is tightened up on bolt 30, the outer or free end of link 20 pivots on the large end of the shoulder bolt. Motion between fork IT and rock shaft 22 takes place about the axis of bolt 30, which is the same axis of rotation as before the addition of link 20.

Intermediate its ends, rock shaft 22 carries a pair of spaced, upwardly extending arms 32. Between the upper or outer ends of the two arms 32 is pivotally mounted a sleeve 34 to which is fastened the feeder dog arm 35. Feeder dog 36 is attached to arm 35 at a location near the end of the arm remote from sleeve 34. Dog 36 has an upper toothed surface, shown in Fig. 4, that is adapted to be raised above the surface of plate 31, which is removably mounted in bed plate l2, in order to move the cloth or other material past the needle. For this purpose, any point on dog 36 moves in a closed circuit which somewhat resembles an oval with the top side flattened, although the exact shape of the path through which the feeder dog travels is not essential to this invention.

In a typical cycle of movement, dog 36 moves upwardly until its toothed upper surface projects slightly above the top surface of plate 31 so that the dog can engage the material being sewn. The dog then moves horizontally, parallel to plate 31, movement being toward the right if the material is to be advanced in the normal direction and toward the left if the material is to be moved in the reverse direction. At the end of the horizontal stroke, dog 36 drops downwardly out of engagement with the material and then returns in a generally horizontal direction to the point where it again moves upwardly, repeating the cycle just described. The horizontal components of their motion are imparted to dog 36 and arm 35 by the two arms 32 on rock shaft 22. As the feeder shaft oscillates, moving arms 32 through short arcs. arm 35 is moved longitudinally andthe motion imparted thereby to dog 36 is substantially all horizontal or paralled to plate 31.

The vertical components of motion are imparted to dog 36 by arm 40, which is shown fragmentarily in Fig. 4 and is pivoted on frame 2, at a location not shown in the drawings. The free end of arm 40 is provided with a slotted guide or fork which receives roller 4| rotatably mounted on the forward or right-hand end of feeder dog arm 35. Up and down movement is imparted to the end of arm 4E1 by means of cam G2 which is shown diagrammatically in Fig. 4. The cam 42 is mounted to oscillate about a vertical axis by means not shown in the drawings; and in so doing the inclined surface of the cam raises and lowers the forward end of arm 40 by engagement with roller 43 mounted on arm 40.

The movements of arms 40 and 35 are synchronized since all moving parts are ultimately driven by shaft l4, to produce a resultant movement of feeder dog 36 of the character previously described. However, advantage is taken, as will be pointed out in greater detail later, of the fact 5. that the horizontal and vertical' comp'on'ents of motion of the feeder dog are imparted to :thedog by separate driving mechanisms, to reverse the direction'of feed.

Near its upper end, but below jaws l6, fork if has mounted on it roller 45 that projects from one side. Roller 45 is positioned to engage the two parallel side walls of guide block 45 which is mounted on frame H] by 'means of shoulder bolt 41. Bolt 41 has two shoulders, the outer one of which engages the face of block 45 and the inner one of which engages the outside face of frame 10. By screwing bolt 4'! tightly into the block 45, they move together so that the angular position of the block can be regulated by turning bolt 41; and bolt 4'! is journaled in the sewing machine frame so that it turns freely. The shape of the bolt and guide block are shown in greater detail in Fig. 6.

-"-'Ihe angular position of bolt 41 is controlled manually by means of a bell crank and lever arrangement shown particularly in Figs, 1 and 2.

so that the members lock together when screw 55 I is tightened in place.

Bell crank 52 is pivotally mounted at 53 on bracket 54 which is fastened to thefront side of frame It by means of bolt 55. The short leg of bell crank 52 has a pin 51 positioned within slot 49a in lever 49 to effect a sliding connection between the bell crank and lever. The effect of moving bell crank 52 is to rotate lever 49 and'bolt 41, as shown in- Fig. 2. When the handle or longer end 5211 of hell crank 52 is at the top of the guide slot 50 in the face of bracket 54, as shown in Figs. 1 and 2, then lever 49 occupies the full-line position of Fig. 2. When the handle of bell crank 52 is depressed to the bottom of slot 65, as shown by the dot-dash lines of Fig. 2, then lever 49 is rotated clockwise to the dot-dash position of Fig. 2. Corresponding rotation of block 46 takes place. In order to automatically return lever 49 to the full-line position, which istermed lever 49 to the right, as viewed in Fig. 2.

As an aid to obtaining and holding fine adjustments in the position of the handle of bell crank 52, the outer end is preferably threaded to .receive thumb nut 63. The inner end of thumb nut 53 is rounded, preferably being semi-spherical in shape. As the thumb nut is screwed down on the shaft of bell crank 52, the space between pivot 53'and the thumb nut decreases, and the crank handle moves down, until it is horizontal, since in that position the distance between the vertical front face of bracket 54 and pivot 53 is a minimum. As the thumb nut is backed off,

the handle can be moved either way from the.

horizontal or mid-position, it being apparent that movement either above or below the mid-position will be equal.

' Having described the mechanism involved, the

operation of our invention will now be described. eccentric. cam I5 rotates" in engagement with 'rally; The for ces applied to the fork'jaws'are perpendicular to the faces of jaws It or transverse to thelongitudinal extent of the fork so. that these forces, as seen clearly from Fig. 4,-a-re applied in a generally horizontal direction. 'If there were no other restrictions upon the movement of the fork or no other forces applied to it, the fork would thenmerely oscillate about the axis of its pivotal connection to feeder shaft arm 2 5.

But a vertical component of motion is given to fork it by virtue of its connection to'slide block it." Roller 45 engages the two parallal sides of the guide in block 46, as shown in Fig. 3. If the block is normallypositioned as in Fig. 4 with the sides of block 46 inclined'upwardly and to the right, dog 35 advancesmaterialtoward the right past the needle, this direction'of advance being termed forward since it is the normal direction of movement of material during the sewing operation. It" will be clear from Fig. 4 that as fork ii is moved to the right by rotation of cam l5 from the position shown in that figure, the fork also moves upwardly because the inclination of guide blockee forces roller 45 to move upwardly at the same time that it moves to the right. Likewise the fork moves downwardly when it is moved to the left of the position shown in Fig. 4. As a consequence, as the upper end of the fork oscillates right and left in a horizontal direction, the fork also moves longitudinally up and down. 'The amplitude of this vertical movement depends upon the inclination of the sides of block 46, for a given eccentricity of cam 15.

It has been conventional construction in some types of sewing machines to provide means for adjusting the inclination of block 45 between the full-line position of Fig. 4 and a position in which the guide is substantially horizontal, 'or more nearly parallel to the direction of force applied to the fork by cam l5. Under this latter condition, the vertical component of motion produced by block 45 is reduced practically to zero and the only motion produced by cam I5 is an oscillation of for]; El about its connection with arm 2i. Under this circumstance, dog 35 has no forward component of motion since arm 2|, and consequently arms 24, remain motionless, or substantially so. The purpose of this conventional adjustment of the inclination of block 45 is to vary the length of stitch, it being possible by changing the position .of block 46 to vary the T length of stitch from zero to the full maximum of which the machine is capable.

In converting conventional types of sewing ma- =chines to our improved construction, it is necessary to change block 45.

that it is mounted on shoulder bolt 4! and is free to turn with the bolt. This operation may involve either modifying the existing block 46 by re-shaping it so that it it is free to turn, or

1 it may involve replacing the block with a new one of substantiallythe shape shown in the draw- The purpose of changing the mounting of block 45 is primarily to make it possible to reverse the inclination of the block relative to the fork from to the position 45a, there occurs a reversal in the relationship of the horizontaltd the vertical components of. motion of fork l1. By reference to Fig. 4, it will be seen that when the block is in reversed position 46a, fork moves to the right and down. instead of to the right and up as before. Likewise the fork moves up when it moves to the left of the position shown instead of to the. left and down as when the block is in the normal position.

Since all the parts of a sewing machine move in the same timed relation, the reversal of the relationship of the vertical components of motion in fork I! to the horizontal ones is carried down along through the drive linkage to effect a similar change in the movement of dog 36. This will be obvious when it is understood that no change in the timed relationship of cam 42 and drive shaft I4 is made so that the motion. of cam 42 which produces the vertical movement of arm- 4|! and dog 36 continues in the same timed relationship to the horizontal movement of fork arms IS. The change affects only the vertical components in fork that move arm 2| up and down, causing shaft 22 to rock and oscillating arms 32 to produce the longitudinal motion in dog arm 35 which in turn produces the horizontal movement of dog 36. By changing the phase relationship of the vertical to the horizontal components in fork H, the horizontal components of motion of dog 36 are similarly changed in their relation to the vertical components of dog 36. Hence the ultimate effect of reversing the inclination of block 46 is to shift the phase relationship of the horizontal components of feeder dog arm 35, produced by the oscillation of feeder shaft 22 and arms 24, with respect to the vertical components of motion in arm 35, produced by oscillation of arm 40. This is in contrast to the results of a mere change in inclination in a given direction, which merely varies the amplitude of horizontal movement of dog 36 while retaining the same phase relationship to the vertical motion.

Because most older types of conventional sewing machines as marketed were not intended or designed to produce a reverse stitch, it is necessary to introduce into their mechanism certain adjusting means, and this is the function of link 23. If block 46 is reversed in inclination and the mechanism operated with fork I! connected directly to rock shaft arm 2| in the conventional manner, the mechanism almost always fails to operate for either one or both of two reasons. In the first place, the clearances between the arms of shaft 22 and the nearby parts of frame and plate l2 are not suflicient to permit the arms to move with slightly greater amplitude in the reverse direction. In the second place, dog 36 engages plate 31 at one end or the other of the stroke and does not smoothly enter the slotted opening in the plate. Both of these conditions result from the fact that the clearances are adequate for a normal cycle of operation when the dog only moves to advance the material sewn; and clearances have not been calculated for these parts when dog 36 is moving to reverse the travel of the material sewn. With the conventional design, the parts do not all merely move through the same path but in the reverse direction; actually some parts have a greater amplitude of movement in the reverse direction and therefore bind because of inadequate clearance.

' This condition is corrected by adding link 20 to the train of elements between drive shaft l4 and dog 36. Link 25 is the only element in this train that enables any adjustment to be made in the 81 relative positions of the parts. This can be done with the use of link 20 since it is capable of angular adjustment with respect to the longitudinal axis of fork by rotating the link around pin 2'! and clamping it in any adjusted position, by means of clamp screw 28. Link 20 being immovable with respect to fork becomes, in effect, a part of the fork; and the same result can be obtained by other designs which would enable an adjustment to be made in the length of the fork between the axis of roller 45 and the axis of the connection to arm 2|. Adjustment of link 20 permits a very close adjustment to be made of the angular position of shaft 22 and arm 2| relative to any given position of fork 1.

It has been found by experience, that if these adjustments are made by link 20 so that arms 32 are enabled to move in the full stroke in the reverse direction without binding or striking the frame, and the same is true of dog 36 with respect to plate 31, there is no difficulty encountered at the forward end of the stroke. Thus link 28 when once set in the proper position can remain there without change.

It is desirable that the maximum length of stitch both forward and backward be equal; and this is accomplished by means of an adjustment provided between bolt 47 and arm 49. As shown in Fig. 6, the engaging surfaces on these two members are serrated so that they firmly interlock at any one of a number of positions removed but slightly from each other. After block 46 is screwed tightly on to bolt 41, arm 49 is then secured in place by a screw 50. Before finally tightening screw 50, arm 49 is so positioned relative to bolt 41 that block 46 is in the neutral or horizon tal position at which no vertical movement of fork T is produced when handle 52a of bell crank 52 is at the mid-point 0 of the scale 65 on the face of bracket 54. Screw 50 is then tightened to maintain this relationship between arm 49, bolt 3?, and block 46. As a consequence equal movements of handle 52 above or below the mid-point of the scale move block 46 equally from the neutral position and produce a stitch of equal length either forward or backward.

Advantage is taken of this fact to provide thumb nut 63 on handle 52, the purpose of which is to limit the travel of the handle to equal distances above or below the mid-point of the scale. Thus if the thumb nut is set to produce a stitch of given length in the forward direction, when the handle is depressed to the maximum extent possible without changing the adjustment of thumb nut 63, the machine produces a stitch of the same length but in the reverse direction. By providing a rounded inner end on thumb nut 63, turning down the thumb nut on the handle automatically moves the handle toward the mid-point or zero on the scale and sets the length of stitch in both directions.

From the foregoing description of a preferred embodiment of our invention, it will be obvious that changes may be made by and will occur to persons skilled in the art, without departing from the spirit and scope of our invention; and consequently it is to be understood that the foregoing description is considered to be illustrative of, rather than limitative upon, the appended claims.

We claim:

1. In a sewing machine having a feed dog driven by a linkage consitsing of a plurality of interconnected members, the combination of a fork having a collar at one end, a link secured to the fork having a fixed pin inserted in the collar,

screw means adapted to clamp the pin in the collar, the link being angularly disposed with respect to the fork and rigidly held in an adjusted position by tightening said screw means.

2. In a sewing machine, the combination comprising: a feed dog; a rotating drive member; a fork engaging at one end the drive member to be moved thereby; stationary guide means engaging the fork intermediate its ends to control one component of the motion of the fork; a rock shaft operatively connected to the feed dog to produce one component of motion of the feed dog and having an arm connected to the fork; and means for adjusting the distance between the arm and the stationary guide means.

3. In a sewing machine, the combination comprising: a feed dog; a rotating drive member; a fork engaging at one end the drive member to be moved thereby; stationary guide means engaging the fork intermediate its ends to control one component of the motion of the fork; a rock shaft operatively connected to the feed dog to produce one component of motion of the feed dog and having an arm;- a link connecting the arm to the fork, the link being angularly adjustable with respect to the fork; and means for holding the link and fork in adjusted positions to vary the distance between the stationary guide means and the arm.

4 4. In a sewing machine, the combination comprising: a frame; a feed dog, a rotating drive member; a fork engaging at one end the drive member to be moved thereby; stationary guide means engaging the fork intermediate its ends to produce a longitudinal component of the motion of the fork; means rotatably mounting the guide means on the frame for rotation of the guide means between positions shifting the phase relationship of longitudinal and lateral components of motion of the fork; a rock shaft operatively connected to the feed dog to produce one component of motion of the feed dog and having an arm connected to the fork; and means for adjusting the distance between the arm and the statior'iary guide means.

" PHILIP J. STUSTER.

GEORGE H. EPSTEIN.

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

UNITED STATES PATENTS Number Name Date 2,235,552 Gilbertson Mar; 18, 1941 2,426,506 Ingwer Aug. 26, 1947 2,430,207 Best Nov. 4, 1947

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