US2065885A - Sewing machine - Google Patents

Description

Dec. 29, 1936.

H. F. BRIGGS ET AL SEWING MACHINE Filed Sept. 14, 17933 3' Sheets-Sheet l ATTORNEY 193 H. F. BRIGG ET AL ,0 3

SEWING MACHINE .Filed Sept. 14,1955 .3 Sheets$heet 2 ATTORNEY Dec. 29, 1936. H. F. BRIGGS. ET AL 2,

SEWING MACHINE Filed $ept. 14, 1933 s Sheets-Sheet s 2J0" w w" M,

@TORNEY 2 Patented Dec. 29, 1936 2 335 UNITED PATENT OFFICE SEWING MACHINE Howland F. Briggs, Buffalo, and Robert N. Cundall, Lackawanna, N. Y., assignors to Consolidated Packaging Machinery Corporation, Buffalo, N. Y., a corporation of New York Application September 14, 1933, Serial No. 689,400

3 Claims. (01. 112--215) Our invention relates to sewing machines, paremployed in connection with driving mechanism ticularly sewing machines such as are adapted for comprising a main drive shaft extending parallel heavy duty. The primary purpose for which to the principal axis of the needle and having these heavy duty sewing machines are designed eccentric means mounted thereon for the pur- 5 is the sewing of heavy multi-ply paper bags such pose of driving the feeding mechanism as well as 5 as are used for packaging cement and similar maother moving parts of the machine, and the sewterials. These bags frequently consist of four or ing machine of our invention is also especially five plies of heavy kraft paper and are often adapted to be employed in conjunction with gusseted so that the needle must traverse as mechanisms for filling and closing open-mouth many as twenty plies of paper. The weight of bags as those described and claimed in the 00- 10 such a package is frequently very great so that pending application of Robert N. Cundall, Serial a sturdy machine is necessary to close their open No. 640,758, filed Nov. 2, 1932, and the copending mouths. applications of Robert N. Cundall and Lincoln A.

We have found that previous sewing machines Cundall, Serial Nos. 666,114 and 686,816, filed operated satisfactorily on cloth bags even with April 19, 1933 and September 9, 1933, respectively. 15

slight inaccuracies of feeding movement, because With respect to this and other apparatus, it is of the relatively flexible character of cloth, wheredesired to point out that, while the feeding mechas if such inaccuracies were allowed in the closing anism is referred to herein as being for the purof filled paper bags the defective and irregular pose of advancing the material through the sewstitching produced would not efficiently close the ing machine, it is not absolutely essential that bag and would often result in breaking or jamthe actual forward motion of the material be ming the mechanism. An object of our invention caused by the feeding mechanism, as this motion is to devise a machine sumciently strong and may be effected by other means and the feeding rugged to operate on heavy filled paper bags. mechanism may actually cause the sewing ma- A specific feature of our invention comprises a chine to travel along the paper, whether the latter 25 feed dog so mounted and operated as to have is stationary or in motion. In any event, howconstant' positive backing rather than the old ever, the function of the feeding mechanism is to style of mounting of the feed dog at the. end of assist in producing a relative movement of the relatively long members. These long members material being sewn with respect to the sewing 3 could not stand the severe stresses without bendmachine, and it is immaterial in so far as our ing, and no operating mechanisms were found present invention is concerned whether the one which could operate through short members due or the other is actually caused to move by the to the relative lack of space in the normal sewing feeding mechanism.

head. Our invention is designed to overcome this Thus, in sewing the mouths of previously filled problem. bags, especially bags adapted to contain large A further object of our invention is to provide amounts of materials, it is not ordinarily feasible -a feed dog which operates in a straight path durto move the bags along in an intermittent jerking the feeding movement so that the stitches will ing movement, and the relatively stiff and rigid have exactly the same length, an end which could paper allows for no movement of the paper rel-a- 40 ot be atta in & Sewing mechanism v n a tive to the head while the needle is engaged with 40 feed dog designed to operate in a rounded path the paper during stitching.

during its feeding stroke since the smooth, hard As shown in the aforesaid co-pending applicasurface of the paper would not allow such a feed tions of Robert N. Cundall and Lincoln A. Cundall,

dog to positively feed during the time when it was a sewing head for such use may be pivotally approaching and receding from the presser foo-t. mounted on an axis normal to the plane of the A further object of our invention is to provide material being sewn, the head being rocked about a feed dog, having the foregoing characteristics this axis as the paper advances, or as the head and advantages, which approaches and recedes is moved along the paper, as the case may be. from the plane of the material in substantially a Our invention is therefore especially adapted.

normal path thereto, and without lateral devito be employed in a sewing head of this character, 50 ation from the line of stitching, thereby avoiding in which the various moving parts are driven the gouging and marking of the material which from a main drive shaft having its axis parallel unavoidably occurs in the use of feed dogs pivoted to that of the needle and having eccentric means on relatively long structural members. for actuating the needle, the feeding mechanism Such mechanism is especially adapted to be and the looper mechanism. Such a head, when 55 tially or entirely in the line of thrust.

employed for stitching the mouths of previously filled bags, and, it may be, for other purposes as well, is preferably pivotally mounted on an axis passing through the center of gravity of the head or coaxial with the drive shaft, but in any event normal to the plane of the material being sewn.

More specifically, our invention contemplates, in addition to a feed dog mechanism mounted upon a shaft in the manner aforesaid extending parallel to the direction of advancement of the material being sewn through the machine, .the provision of means, actuated by an eccentric l'ocatecl upon or driven by the main drive shaft, for reciprocating the feed dog mechanism to and fro along this shaft, that is to say, in the direction of motion of material being sewn and opposite thereto; and of means, also driven by an eccentric device mounted upon the main drive shaft or connected thereto, for contributing a reciprocal movement to the feed dog mechanism about the principal axis of the aforesaid shaft extending parallel to the direction of the movement of the material being sewn, and whereby the feed dog proper is caused to advance through the feed plate to grip the material and to be withdrawn therefrom. The latter means is furthermore so designed and constructed in accordance with our invention that the thrust exerted by the presser foot or the feasible biasing means therefor, through the presser foot and the material being sewn upon the feed dog and tending to force the latter back through the feed plate, is resisted by structural members lying substan- In other words, the feed dogis provided with a rigid metal backing located directly in the line of thrust exerted by the presser foot, as distinguished from prior devices in which this thrust was resisted by flexible means or by structural members extending more or less laterally with respect to the line of thrust and supported at a point removed from the direct line of thrust.

Thus, insome prior devices of the general character recited hereinabove, the feed dog mechanism has been mounted at the end of a relatively long structural member extending laterally with respect to the line of thrust of the presser foot and supported at some distance therefrom, andv when such prior devices were adjusted to give a sufficiently strong gripping of the material being sewn to take care of such stresses as are involved in sewing the mouths of large open-mouth filled paper bagsor the like, such vlateral members tended to yield or bend, thereby reducing the grip of the feed dog or presser foot on the material being sewn or causing a misalignment of the material being sewn during the operation.

According to our invention, however, this disadvantage of prior devices is'overcome by means of the device herein set forth and the machine may be adjusted to grip the material being'sewn very tightly withoutfear of bending or'overstressing any structural parts thereof, or of injury to the mechanism, or of a tendency toward misalignment of material being sewn as it is advanced through the machine.

In a more specific aspect, our invention contemplates the provision of a cam device, preferably a sliding cam, adapted to travel between the feed dog mechanism; and a fixed member, for example, the frame of the sewing machine itself, in such manneras to'produce an oscillation or reciprocal motion of the feed-dog device about the shaft on which it is mounted, the insertion or operation of the cam mechanism with respect to the feed dog mechanism taking place substantially in the line of thrust exerted by the presser foot and providing structural means in which the thrust of the presser foot produces a compressive stress in the feed-dog backing means as distinguished from bending moment or shear.

In another more specific aspect ,ourinvention contemplates the provision in a sewing machine, of a single main driving shaft, a needle bar reciprocating in a line parallel to the main shaft, a looper cooperating therewith to form stitches, a feed dog for advancing the material relatively to. the needle, and eccentrics on the mainshaft for operating the needle, the looper and the feed dog. The latter provision is a tremendous ad- Vance in that it makes practical the extreme simplification and efiicient operation of sewing mabe adjusted and once its correct contour is lost must be replaced, These cams were very expen:

sive due to the accuracy necessary, and required. the maintenance of expensive routing or special milling machines at the manufacturer's ,plant,

With our invention each rotating driving element comprises a simple eccentric, easily turned out on a lathe and easily adjustable to compensate.

for wear as is well known. Further, our invention comprises other simple parts in all respects, any of which may be economically and easily replaced.

In order that our invention may be more clear- 1y set forth and understood, we now describe,.

with reference to the drawings accompanying and forming a part of this specification, an illus trative instance of the manner and form in which our invention may be embodied and utilized. In.

these drawings:

Such cams, subject- Fig. 1 is an elevational view of a sewing machine constructed. in accordance with our present invention, in which the sewing machine appears with the usual cover plate, as 'well as other parts having no bearing upon the present invention, removed for the sake of clarity to give a better view of the operating andstructural parts of the machine;

Fig. 2 is a bottom view of the apparatus illustrated in Fig. 1;

Fig. 3 is an enlarged vertical sectional view of a portion of the apparatus illustrated in Fig. .1 taken on the line 33 of Fig. 1;

Fig. 4 is an enlarged vertical sectional view of the apparatus illustrated in Fig. 3 along the line 44 of Fig. 1;

Fig. 5 is an enlarged vertical sectional view similar to Fig. 1, but having parts of the casing broken away to allow a clear view of the feed dog, and the looper mechanism removed in part to allow a clear view of the feed dog operating means;

Fig. 6 is a schematic view of the path of travel of the feed dog, the line AB representing the face plate of the machine, and the shaded portion representing the feeding stroke and illustrating the straight line characteristics thereof;

Fig. '7 isa similar schematic view representing the movement of the needle point normalto the material and illustrating its timed relation to th feed dog travel;

Fig. 8 is a similar schematic view representing the orbital pathof movement of a point on the looper in relation to the needle which reciprocates normal to the plane of Fig. 8;

Fig. 9 is a View similar to Fig. 6 but represent ing a feed dog path resulting from a simple variation which allows a shorter feeding stroke;

Fig. 10 is a view similar to Fig. 6 but representing a feeddog path resulting from a simple adjustment which also allows a shorter feeding stroke and hence allowing a relatively greater time for the needle and looper to operate; and

Fig. 11 is a cross section taken on line i l--l l of Figure 2 of the means to cause the feed dog to move vertically,

Similar reference numerals designate similar parts in each of the several views of the drawings.

Referring now to the drawings, there is illustrated a sewing machine or sewing head having a frame I of more or less conventional shape with a throat portion 2 through which the material to be sewn is advanced. The direction of advancement of material through the sewing head, as viewed in Fig. l is perpendicular to the plane of illustration and away from the observer. At one side of the throat portion 2 there is provided a feed plate 3 of conventional type having the usual openings (not shown) through which a feed dog member A is adapted to move.

Located in the entering portion of the throat portion 2, We provide a presser foot 5 of more or less conventional shape opposing and adjacent to the feed plate 3, and mounted upon a support indicated generally at 6 in such manner as to be adjustably spaced from the feed plate 3. The supporting means for the presser foot 5 indicated generally at 6 is constructed according to any well known manner to exert a flexible biasing force normal to the face of the feed plate 3. Thus the presser foot 5 may be adjusted to clear the feed plate 3 by a distance commensurate with the thickness of the material being sewn, while yieldably resisting further displacement from the feed plate 3.by a force commensurate with the extent to which the material being sewn must be gripped by the feed dog 4 and the presser foot 5 at each period of advancement. It will be understood that the requiredgripping force may vary considerably but that, in sewing the mouths of previously filled heavy paper bags of large capacity, this force will be far more severe than is required in machines to be employed for lighter duty as, for example, for the sewing of relatively small cloth bags. The specific mechanism for applying this yielding bias force to the presser foot 5 is similar in principle to that employed in previous machines and here need not be described in de tail.

In the instance illustrated, the sewing machinel is provided with a main drive shaft Hi journalled in bearings l l and I2 attached to or forming a part of the frame 9, which drive shaft if! has a principal axis perpendicular to the plane of the material being sewn and is provided with driving pulleys l3 and it and a hand wheel 55,

r all of which are conventional in character and have no bearing upon the present invention except insofar as they typify means whereby the shaft it} may be connected to a suitable driving motor (not shown). At one end of the shaft ill, there is provided an eccentric or crank member it which is operatively connected by means of a connecting rod ill to a bell crank it pivotally mounted upon a pin l9 attached to the frame I. The end of the bell crank 18 opposite to that pivotally connected to the rod H is operatively connected by means of a link or links 2! to a lug 22 mounted upon a needle holder bar 23 having a needle 2% and iournalled in bearings 25 mounted upon and forming a part of the frame 1.

The principal axis of the needle bar 23 is normal to the face of the feed plate 3, that is to say, normal to the plane of the material being sewn, and parallel to the principal axis of shaft l8 and in each revolution of the shaft it, the needle bar 23 is caused to move forward, thrusting the needle through the material being sewn and the openings in the presser foot 5 and the feed plate 3 into the position in which it is illustrated in Figs, 1 and 2 and then to be withdrawn from the material being sewn in order to permit the material to be moved ahead with respect to the needle by the feed dog 4% in a position for the next stitch.

The needle 2 is provided with the usual eye (not shown) through which passes the needle thread 35. The latter is supplied to the needle 2% from a suitable thread stand (not shown) through a thread tension device H, a guide tube 32, an eye 33 mounted upon the rear end of the needle bar 23 and fixed eyes 3 5 conventionally located adjacent the bearings 25.

In the present instance, the reciprocation of the needle 2% carrying the thread 33 cooperates with a looper 35 carrying a second thread 35 to form a double-thread interlocked chain stitch. The looper 35 is fully illustrated except for its extreme tip in Fig. 1. For a better understanding of the lcoper and of the type of stitch for ned by the machine reference may be made to the United States Patent of George Hoepner #1270948, i..- sued July 2, 1918, wherein is illustrated and claimed a single form of the same general type of looper. The looper 35 is mounted in a holder arm 3'5 attached to one end of a rod the other end of which is pivotally attached to an eccentric portion 39 of the main drive shaft it. The rod is slidably mounted in a sleeve member it pivotal- 1y mounted at H to the frame l. A part of sleeve member dii is removed in Fig. 5 for the sake of clarity.

It will be understood by those skilled in the art and familiar with devices of this character that, as the shaft it rotates, the looper 5. 5 is caused to travel in a closed and more or less narrow elliptical path lying in a plane parallel to the plane of the material being sewn, during the course of which path it passes downward on one side of the then retreating needle and enters a loop being formed in the needle thread 363, and subsequently rises on the other side of the path of the needle, producing atriangle of thread, one side of which is formed by the aforesaid locper, another side by the looper thread 36, and the thir by the aforementioned loop, which triangle is entered by the nee die on its next forward motion. Shortly thereafter, the loop is stripped from the rising looper, thereby producing an interlocking of the needle thread 3!) and the looper thread 3% on one side of the material being sewn.

Our improved mechanism for feeding the rial to be sewn through the machine, or for advancing the sewing machine relative to ".13 material being sewn, as the case may be, between the stitching intervals, is best illustrated in Figs. 3, i and 5 to which reference will now be had. The feed dog t, as mentioned hereinabov-e, is required to periodically advance through the throat plate 3 to grip the material against the biased presser foot 5, then to move forward in the direction of movement of the material being sewn relative to the sewing machine while gripping the material,

then to be retracted out of engagement of the material being sewn through the throat plate 3 and finally to move back in a direction opposite to the direction of the material being sewn with respect to the sewing machine in order to complete its cycle and to be ready to be again advanced to grip and move the material being sewn.

In order to provide for this motion of the feed dog 4 and to insure that the forward motion of the feed dog, while in engagement with the material being sewn, will be in a substantially straight line rather than in v curved or arcuate line, the feed dog 4 is mounted upon an arm or feed dog holder 50, the opposite end of which terminates in a sleeve 51 mounted upon a pin 52 secured to the frame I at a suitable distance from the throat plate 3 and extending parallel to the stitching line, that is to say, parallel to the direction of movement of material being sewn with respect to the sewing machine. The sleeve 5! is so mounted upon the pin 52 as to be capable of a sliding movement along the pin 52 or a rocking movement about the latter. The pin 52 may be provided with an enlarged head 53 to limit the movement of the sleeve 5! along the same. In order to provide for the forward and backward sliding movement of the sleeve 55 along the pin 52, the arm 56 is provided with a stud 54 which is adapted to be received into and freely held by the bifurcated end, or, preferably, within an oval hole through a member 55 mounted in the end, of a rocking lever 56 pivotally mounted at 5'! on a supporting member 58 attached to the frame I and having at its opposite end a yoke 6| adapted to receive an eccentric 62. The eccentric 62 is mounted upon the main drive shaft l6, and as the shaft it! rotates the eccentric 62 swings the rocking lever 56 to and fro about the pivot 51 and through the stud 54 causes the arm 50 to slide to and fro along the pin 52.

The manner in which the stud 54 connects arm 50 to lever 56 is such that the arm 50 is free to rock slightly about the pin 52 withoutinterfering with the motion imparted by the rocking lever 56 and the eccentric 62.

We further provide a spring or springs 63 lying between the arm 56 and the rocking arm 56, which springs 63 exert a biasing force tending to rock the arm 59 about the pin 52 in a counter-clockwise direction as viewed in Fig. 5 and thus keeps the feed dog 4 retracted out of engagement with the material being sewn and member 64 against cam member 65 as will appear hereafter.

In order to provide for advancing and retracting the feed dog 4 through the openings in the throat plate 3, the arm 56 is provided with a rearwardly extending member 64 preferably connected to the arm 56 immediately behind and adjacent to that point at which the material receives the thrust of presser foot 5. It will be obvious, however, that the member 64 may readily be attached to the feed dog 4 if so desired but, in any event, the member 64 is preferably so situated as to be directly aligned with the force exerted by the flexibly biased presser foot 5 when the feed dog 4 is in its advanced position in engagement with the presser foot 5 or the material being sewn.

Lying immediately behind the member 64 and limiting rearward motion of the member 64 and the feed dog 4 under the influence of the spring 63 we provide a sliding cam member 65, the rear face of which opposite the member 64 is provided with an inclined salient cam portion 66. which 'lies adjacent to and, upon vertical reciprocation of the member 65 is adapted periodically to engage and ride over an'inclined salient cam portion 61' of a fixed canr member 68 which may convenient 1y be attached to the frame I. Preferably, the

inclined cam portion 61 is provided on a separable and adjustably mounted part 69 which is simple to make and negligible in cost. It will be obvious that, upon vertical downward movement of cam I member 65, cam surfaces 66 and 61 will slide past each other and cause a resultant horizontal movement of the cam member, thereby causing the feed dog to move outwardly. This motion of the feed dog is accomplished through transmission of the outward thrust by member 64 to cause theswinging of arm 50 about pin 52. Upon upward movement of cam member 65, the cam surfaces will disengage and the feed dog will be retracted due to the thrust of the presser foot, this motion being furthered by springs 63 to insure complete retraction of the feed dog below the surface of throat plate 3. Cam member 65 is guided in its reciprocatory movements between the frame I and a flange 10 on member 68.

In order to providefor vertically reciprocating the member 65 in such timed relation with respect,

to the oscillation of the rocking member 56 as to alternate the periods of maximum rates of advancement and retraction, respectively, of the feed dog 4 through the throat plate 3 with the forward and backward motions, respectively, of the feed dog 4 in and against the direction of movement of the material being sewn, the member 65 is preferably actuated by some form of eccentric mounted upon the shaft I0 and having a predetermined angular position with respect to the eccentric 62 and the rotation of the shaft l0. While a separate eccentric may be employed for this purpose or the vertical reciprocation of the cam member 65 may be derived from the eccentric 62 itself, in the present instance we have illustrated a convenient and space-saving mechanism for effecting the vertical reciprocation of the member 65.

In this instance, the upper portion of the member. 65 is pivotally connected by means of a connecting rod H to a knuckle member 12 mounted upon the connecting rod 38 which actuates the looper 35 and, as the shaft l0 rotates, the knuckle 12 through the connecting rod H causes the member 65 to slide up and down thus alternately advancing and retracting the feed dog 4 through the openings in the throat plate 3 in the manner set forth hereinabove.

Knuckle 12 has an orbital movement in the plane of Fig. 4 and member 65 has a. straight line movement in this plane, while knuckle 12 has straight line movement in the plane of Fig. 5 and joint 13 has an orbital component of movement in this plane due to the coaction of cam surfaces 66 and 61. Therefore. the joints at 12 and 13 each comprises a universal joint to an extent sufiicient to allow for such movements.

It will be obvious from inspection of the draw ings and more particularly Fig. 5, that the force exerted by the presser foot against the feed dog 4 when the latter is advanced through the throat plate 3is resisted by the compressive strength of the members 64, 65 and 68 and that the stress thus set up is substantially directly in alignment with the direction of the force exerted by the presser foot 5. Due to the fact that the stress thus set up is resisted substantially entirely in compression and bending or shear stress is substantially and entirely avoided, it is possible to construct the various parts receiving the stress much more lightly with respect to a given force :5

exerted by the presser-foot mechanism than would otherwise be true, and, consequently, it is possible according to our invention to greatly reduce the inertia and weight of the feed-dog actuating mechanism as compared with prior devices. This is especially important with respect to such relatively heavy presser foot action as is required to grip materials such as paper and more particularly the mouths of heavy paper bags.

Figs. 6, '7 and 8 are motion studies of the various. operating parts of our sewing machine, which taken in connection with Figs. 3, 4 and 5 will eX-- plain the operation thereof. Figs. 4 and 5 are views taken at what may be termed the beginning of a working cycle, or of rotation of shaft i0. Accordingly, Fig. 3 is taken at 90 of rotation. It is apparent that as shaft Ill rotates 90 from the position of Fig. 5 to the position of Fig. 3, member 50 will move to the right approximately one half of its travel, while cam member 55 moves downward in a straight line as cam surfaces 65 and 6'! approach each other. As a result the feed dog will have a straight line movement to the right (Fig. 6). During this time looper 555 (Fig. 8) descends approximately one half of its travel while swinging to the left of the needle 2 which is then moving outward (Fig. 7). During the next 30 of rotation cam surface 00 rides upon cam surface 6'! while member 50 starts toward the left, causing the feed dog to be thrust forward along a curved path to engage the material. Simultaneously needle 24 clears the material. During the next 60 of rotation cam plate 65 is traveling downward in a straight line while member 50 continues to move toward the left in a straight line, the feed dog gripping the material and feeding it through the machine. Simultaneously therewith, looper 35 travels to its lowest point while swinging back toward. the right, but being still to the left of a vertical plane through the needle line and below the needle. The next 60 of rotation causes the feed dog to complete its working stroke, and during the next 30 of rotation to retract as cam surface 6% slides off of cam surface 61. During this latter 90 of rotation the looper 35 travels upward while swinging to the right of the needle, and during the last 30 thereof the needle penetrates the material. The final 90 of rotation causes the feed dog to return in a straight line to its initial position, while the looper completes its orbital movement and the needle fully penetrates.

It is obvious from the foregoing that slight variations in the angularity of eccentrics will cause variations in the path relationship of the various parts. Also, a vertical adjustment of member 69 may be utilized to create a longer or shorter working stroke of the feed dog. It is equally apparent that by changing the slope of the cam surfaces 60 and 61 a quicker or slower outward movement of the feed dog may be realized. For example, in Fig. 9, the angle of slope of the cam surfaces has been materially lessened so that 60 of rotation is required to cause them to pass each other, resulting in a short feeding stroke lasting only 60 of rotation and allowing a greater proportionate period for the needle to remain retracted in the material. In Fig. 10, the member 69 has not been altered but has been lowered so that the feed dog remains for 10 more than in Fig. 6 before starting outward. This results in a working stroke lasting only 100, as compared to 120 in Fig. 6. Many other possible relationships may be evolved to meet immediate demands. However, the characteristics of the machine outlined in Figs. 6, 7 and 8, have been found satisfactory and permissive of the following desirable features of operation, i. e., due to the fact that the feed. dog is operative only during 120 of rotation, the needle and looper are allowed 240 in which to form the interlocked chain stitch.

Obviously this allows a substantially greater number of stitches per minute and a correspondingly higher output of bags.

In the foregoing, it is made clear that the feed dog is imparted a straight working stroke shorter than the full reciprocation of member. 50 along pin and during less than 180 of rotation of the shaft, or less than Pi radians. This allows a greater proportionate period for the needle and looper to cooperatively interlock the threads and hence a greater number of stitches per minute. It also clear that by adjustment of member 69,

operative angle of rotation is lessened commensurately with lessening of the straight line working stroke, so that adjustments in the length of stitch is made possible.

Another feature of our invention is that the feed dog is mounted on 'member 50 swinging about and slidable on pin 52. Thus the feed dog is rockably mounted on an axis'of rotation parallel to the plane of the material. The same effect would be obtained if the member 50 were formed with pintles rotatably and slidably guided in holes in the walls of the frame 1, the important thing being that at the axis of the member 52, or its equivalent, thefeed dog holder may be considered as being displaceable only in the line of the axis, while the opposite end of the holder and the feed dog are displaceable in two directions resolved into a closed path of definite form and dimensions. The feed dog has only a negligible outward swing from the moment it contacts the material until it reaches its full outward position, and the lift of the feed dog due to its swinging movement is infinitesimal. The feed dog therefore may be considered as having a practically straight outward thrust and does not draw across and chew the material as was the case in the old machines having feed dogs mounted on long members swinging about a distant pivot. In other words, the feed dog while in contact with the material does not have any motion or lateral displacement up or down from the line of stitching.

As previously pointed out it is immaterial to the operation of our device whether the material is drawn through the machine or the machine drawn past the material as set forth in the aforementioned applications of Lincoln A. Cundall and Robert N. Cundall. The foregoing description sets forth a stationary machine in which the feed dog i actually forces the material forward during the time the needle is withdrawn. However, our invention makes practical the use of continuous feeding of filled bags by causing the feed dog to positively grip the material and swing the sewing head back after having been rocked forward by the engagement of the needle therewith, or the use of a sewing head which travels past a. stationary bag by causing the feed dog to positively grip the material and pull the sewing head relatively thereto while the needle is disengaged.

It will be obvious to those skilled in the art that while we have shown a preferred form of mechanism whereby this result may be achieved, our invention is not limited in its broadest aspect to such specific embodiment but may variously be embodied within the scope of our invention, and

, other specific feed mechanisms of the general relatively stiif materials such as paper, cardboard, or the like, these advantages in part consisting of improvements in the motion characteristics of the mechanism as well as the structure of the mechanism itself.

As pointed out hereinabove, our invention is not limited to the particular exemplification given hereinabove but may variously be embodied and utilized within the scope of the claims hereinafter made.

We claim:

1. In a sewing machine, a feed dog for advancing the material to be sewn in a series of intermittent movements relative to said machine, a holder, upon which said feed dog is mounted,

adapted to be reciprocated along a fixed axis extending parallel to the direction of movement of the material relative to the sewing machine, and a fixed pin pivotally supporting said holder and constituting said axis, said holder having a length from said axis to said feed dog at least several times the length of the arc of movement of said feed dog about said axis.

2. In a sewing machine, a feed dog for advancing the material to be sewn in a series of intermittent movements relative to said machine, a

said feed dog about said axis toward and away j from the material, said holder having a length from said axis to said feed dog at least several times the length of the arc of movement of said feed dog when rocked by said means.

3. 'In a'sewing machine, a throat plate having openings therein, a presser foot located adjacent to said throat plate and flexibly biased toward said throat plate, a feed dog adapted to be advanced through the openings in said throat plate to grip the material being sewn against said presser foot and to be withdrawn through said openings and out of engagement with said material, a holder upon which said feed dog is-v mounted, a pin having its principal axis located in a plane parallel to the face of said throat plate and pivotally supporting said holder, said holder having a length from said axis to said feed dog at least several times the length of the arc of movement of said feed dog to engage the material, means for rocking said holderabout said pin to advance and retract said feed dog through said throat plate, said means comprising members located substantially in line with said feed dog and said presser foot and constituting a rigid backing for said feed dog, and means to move said holder along said pin to cause said feed dog to advance the material engaged thereby with respect to said throat plate.

HOWLAND F. BRIGGS. ROBERT N. CUNDALL.

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