US3368507A

US3368507A - Feeding mechanism for sewing machines

Info

Publication number: US3368507A
Application number: US495039A
Authority: US
Inventors: Orth Hans
Original assignee: GM Pfaff AG
Current assignee: GM Pfaff AG
Priority date: 1964-10-31
Filing date: 1965-10-12
Publication date: 1968-02-13
Anticipated expiration: 1985-02-13
Also published as: GB1120192A

Description

Feb. 13, 1968 H. ORTH FEEDING MECHANISM FOR SEWING MACHINES Filed Oct. 12, 1965 5 Sheets-Sheet l INVENTOR.

HA NS ORT'l-l Feb. 13, 1968 H. ORTH 3,368,507

FEEDING MECHANISM FOR SEWING MACHINES Filed Oct. 12, 1965 3 Sheets-Sheet 2 Fig. 2

o 80 62 I 92 78 a7 a3 0 O as I N VENTOR.

[TARL RAT A TIORIVEY 3 Sheets-Sheet 75 Filed Oct. 12, 1965 INVENTOR.

l/A/VS 27! h'ARL R4 71! ATTO Q VEY United States Patent 3,368,597 FEEDING MECHANISM FUR SEWING MACHENES Hans Orth, Alsenborn, Pfalz, Germany, assignor to G. M. Pfaif AG., Kaiserslautern, Pfalz, Germany, a corporation of Germany Filed Oct. 12, 1965, Ser. No. 495,039 Claims priority, application Germany, Oct. 31, 1964, P 35,412 3 Claims. (Cl. 112209) ABSTRACT 0F THE DESCLGSURE In a sewing machine, the work fed is pre-stressed to a varying degree, to counteract distortion of the seam being sewn resulting from varying characteristics of the sewing material, such as different types of material, varying elasticity of the fabric, etc., by the provision, in addition to the conventional main feed dog located below the stitching plate and behind the needle, as viewed in the feeding direction, of a pair of auxiliary feed dogs located, respectively, above and below said plate and in front of said needle. All three feed dogs, being operated in synchronism to effect conventional composite rectangular Work feed movements, are fitted with individual feed stroke adjusting means of the type including a rotary adjusting shaft, to vary the respective feed strokes in proportion to the angular adjustments of said shafts. The latter are fitted with plural control means to allow adjustment of all said shafts in unison, for controlling the stitching length, on the one hand, and to allow individual adjustment of the differential feed strokes between said main feed dog and said auxiliary feed dogs, for adapting the device to the sewing of materials of different characteristics, on the other hand.

The invention relates to new anduseful improvements in feeding mechanism for sewing machines, and more particularly to a method of sewing two fabric layers or work pieces being tensioned and untensioned, respectively, before and after the stitch formations, as well as to feeding mechanism for the carrying into effect said' method.

An object of the invention is to prevent distortion of the seam being sewn in a pair of superposed fabric layers or workpieces, more particularly to prevent the seam from becoming crimped or ruffled, especially in the case of relatively elastic materials, or materials having a low friction coefficient, such as synthetic or the like fabrics.

Wavy or crimped seams may be obtained, especially with relatively elastic fabric materials, on account of unequal friction conditions obtaining between the work pressure foot and the lower fabric layer, on the one hand, and between the presser foot and the upper fabric layer, as well as on account of reduced friction between said layers, on the other hand. More particularly in the case of fabrics made from conventional synthetic fibers, the friction between thelayers may be of such a low value that the layers will be displaced relative to one another during the intermittent feed movements between one and the next stitching operation, whereby to result in the stitching of one layer in relative compressed condition to the other layer. This, in turn, results in different internal stresses within the layers, giving rise to the formation of a crimped or otherwise distorted seam.

Accordingly, a more specific object of the invention is the provision of an improved method of and apparatus for the carrying out of said method, to substantially prevent any residual relative stresses in the fabric layers at the end of a stitching operation, or to provide a seam being devoid of crimping or the like distortion as a result 3,3685%? Patented Feb. 13, 198

of the elasticity of the material or lack of sufiicient friction between the layers being sewn.

The invention, both as to the foregoing and ancillary objects, as well as novel aspects thereof, will be 'better understood from the following detailed description, taken in conjunction with the accompanying drawings forming part of this specification and in which:

FIG. 1 is a perspective view of work feeding mechanism embodied in a conventional sewing machine and constructed in accordance with the principles of the invention, only those parts of the machine being shown as are essential for the understanding of the invention;

FIG. 2, is a perspective view of the presser foot and upper feed dog of the machine shown by FIG. 1; and

FIG. 3 is a cross-sectional view of a pair of fabric pieces, taken along a seam being sewn therein and being explanatory of the operation of and novel effects obtained by the invention.

Like reference numerals denote like parts in the difpieces by means of a sewing machine of generally conventional design, including a reciprocatory needle and loop taker operative upon the intermittently fed workpieces, to produce a seam in the feeding direction, said workpieces being subject to relative displacement during and in the direction of the feed and resultant distortion of the seam being sewn by virtue of reduced friction or relatively high elasticity of the material. In order to counteract or cancel such undesirable displacement, the improvement essentially comprises the steps of differentially tensioning the successively fed elemental sections of the workpieces immediately preceding the stitching thereof by the needle, and subsequently relaxing the tension forces after completion of the stitching operations, the sense and degree of relative tensioning of the layers being such as to cause, upon relaxation or untensioning thereof, a relative displacement in a direction opposite to and substantially cancelling the first or inherent displacement obtaining during the feed movements or prior to the stitching operations.

In other words, the invention proposes to impart to the fabric layers, at the instants prior to the stitching operations, or while being intermittently fed between two stitching operations, a relative displacement substantially opposite to the inherent displacement caused during the feeding movements. The term displacement is understood not only to apply to the relative movement or shifting of the mating or contacting surfaces of the layers, but to include the total internal displacement or distortion of the layers as a result of the elasticity of the material.

The invention furthermore involves the provision of feeding mechanism for the carrying into effect of the afore-described method, said mechanism comprising essentially, in accordance with one aspect of the invention, main intermittent feeding means (main lower feed dog) operative upon one of the superposed fabrics and disposed behind the needle, as viewed in the feeding direction, first intermittent auxiliary work feeding means operative upon the same fabric layer as said main feeding means and disposed in front of said needle (first auxiliary and lower work feed dog), said first auxiliary feeding means having a feed stroke less than the feed stroke of said main feeding means, and second auxiliary intermittent work feeding means (second auxiliary and upper work feed dog) operative upon the other of the fabrics being sewn and also disposed in front of said needle, said second auxiliary feeding means also having a feed stroke less than the feed stroke of said main feeding means. As a consequence, a

proper design or adjustment of the foregoing relationships between the feed strokes of the main and both auxiliary feed means will result in the fabrics being tensioned differentially in such a manner as to cause the resultant relative displacement upon subsequent relaxation or untensioning of the layers to substantially cancel the displacement during the preceding feed movement, to thereby result in a distortion-free seam, as will become further apparent from the following.

By the provision of further means to adjust the differential feed strokes between the main feeding means, on the one hand, and each of the auxiliary feeding means, on the other hand, the feed device of the invention may be adapted for use with different types of materials or fabrics, to suit existing conditions or requirements. Finally, uni-control means may be provided, to simultaneously vary the absolute feed strokes of all the three feeding means, to extend the scope of application and usefulness of the invention, in a manner as will become further apparent from the following description in reference to the drawings.

Referring more particularly to the drawings, FIG. 1, the sewing machine according to the invention, being of generally standard construction, includes a lower main feed dog 1 disposed below the work support or stitching plate 95, FIG. 2, and behind the reciprocatory needle 92, as viewed in the feeding direction, and a first lower auxiliary feed dog 2 disposed in front of said needle, as viewed in the feeding direction, said feed dogs each being supported by a carrier or feed bar 3 and 4, respectively. The fork-shaped ends 5 and 6 of the feed bars 3 and 4 cooperate with a pair of eccentrics 8 and 9 being fast on a rotating drive shaft 7, to impart the required rise and fall feed movements to the feed bars 3 and 4, in a manner well known. Shaft 7 may be driven by any suitable means (not shown) in synchronism with the main drive or operating shaft 69 of the sewing machine.

Disposed in a position parallel to and in operative driving connection (not shown) with the shaft '7 is a further rotating drive shaft 10 upon which are mounted a pair of eccentrics 11 and 12 each embraced by the ringshaped end of an eccentric rod 13 and 14, respectively. Eccentrics 11 and 12 serve to provide the component movements of the feed dogs 1 and 2 in the translatory or feed direction, to result in the conventional composite rectangular intermittent feeding cycles in cooperation with the up and down components provided by the eccentrics 8 and 9, in a manner well known to those skilled and becoming further apparent as the description proceeds.

Disposed in a position parallel to the shaft 10 are a pair of coaxial oscillating or rockshafts 15 and 16, the inner shaft 16 projecting at both ends from the outer shaft 15. Mounted upon the left hand end of the latter is a fork-shaped lever 17 to which is jointed the feed bar 3 of the main feed dog 1, and mounted upon the lefthand projecting end of the shaft 16 is a further fork-shaped lever 18 to which is jointed the feed bar 4 of the lower auxiliary feed dog 2.

The free end of the eccentric rod 13 is jointed to a pin 19 which is rigidly connected to a first link 20 and which is relatively rotatively connected to a second link 21. The latter is, in turn, jointed by means of a pin 22, to a lever 23 having a hub secured to shaft 15. Similarly, the link 20 is jointed, by means of a pin 24, to a lever 25 having a hub which is secured to a first rotatable setting or adjusting shaft 26.

The free end of the eccentric 14 is jointed to a pin 27 which is rigidly connected to a link 28, on the one hand, and which is relatively rotatively connected to a link 29, on the other hand. The link 28 is jointed, by means of a pin 32, to a lever 33 having a hub secured to a second rotating setting or adjusting shaft 34. Link 29 is jointed, by means of a pin 30, to a lever 31 having a hub secured to shaft 16. As more clearly shown in FIG. 1, the levers 4 25 and 33, as well as the links 20, 21, 28 and 29 all are of the same effective length.

Secured, by clamping or the like, to the adjusting shaft 26 is a multiple fork member 35, and secured to the adjusting shaft 34 are three separate fork members 36, 37 and 38 arranged in parallel with the respective forks of the member 35. The two fork members 35 and 37 are coupled with one another through a central link 39, while the fork members 36 and 38 are connected with the member 35 each by a setting screw 40 and 41, respectively, said screws engaging tapped holes in pivot pins 42 and 43 disposed in the forked ends of the members 36 and 38 and having their opposite ends passing through bores in a pair of further pivot pins 44 and 45 mounted in the member 35, in the manner shown by and understood from the drawing. Limiting rings or nuts 46 secured to the ends of the screws 40 and 41 serve to restrict the displacement of the screws 40 and 41, while coil springs 41 encircling the screws serve to maintain the distance between the member 35, on the one hand, and the members 36 and 38, on the other hand, as set or adjusted by the screws 40 and 42, respectively. Applied to each of the fork members 36 and 33 are an indicating scale 48 and 49 arranged to cooperate, respectively, with index marks 50 and 51 upon the member 37.

Secured to the extreme end of the adjusting shaft 26 is a lever 52 which is operably connected, through a link 53, to one end of a double-arm lever 54. The remaining arm of lever 54, being secured to a shaft 55 rotatively mounted upon the frame of the sewing machine, engages a groove 56 in a stitch length controller or setting disk 57 also rotatively mounted upon the frame of the machine.

A torsion spring 58 encircling the setting shaft 26 and engaging, on the one hand, the frame of the machine and being connected, on the other hand, the shaft 26, acts to urge the latter to a rotational position, whereby to cause the lever 54 to engage one wall of the groove 56 of the stitch controller and, in turn, to feed the fabric or workpieces operated on in the forward sewing direction by the main feed dog 1. Reversal of the feed direction may be effected in a known manner by the operation of a key 59 fast on shaft 55, to shift the lever 54 from engagement with one wall into engagement with the opposite wall of the groove 56 of the stitch controller 57.

The fork member 38 mounted upon the adjusting shaft 34 is fitted with a rearward extension or lever arm 60 which is connected, through a link 61, to a further lever arm 62 being fast on a further adjusting or setting shaft 63 rotatively mounted upon the frame of the sewing machine.

Secured to the setting shaft 63 is a U-shaped member or bracket 64 between the arms of which is rotatively mounted, by a pair of pins 66, a further bracket 65. The arms of the latter are braced by a pin 67 to which is jointed an eccentric rod 68 which is operatively connected with an eccentric 70 being fast upon the main drive or arm shaft 69 of the sewing machine, to impart oscillating movements to the pin 67 about the pins 66 as a pivot axis.

A link 71 is connected, on the one hand, to the pin 67 and jointed, on the other hand, by means of a pin 72, to a lever arm 73 which is, in turn, secured to one end of an oscillating or rockshaft 74 mounted upon the frame of the machine in a position parallel to the main drive shaft 69. Connected to the opposite end of the rockshaft 74 is a lever arm 75 which is, in turn, connected, by way of a link 76, to the arm 77 of a double-arm lever 77 rotatively mounted upon the frame of the machine. The remaining arm of the lever 77 operably engages an arm 78. FIG. 2, of an upper auxiliary feed dog 79 constructed in the form of a double lever. The auxiliary feed dog 79 is supported by the link 80 being jointed to a support 82 secured to the work pressure foot bar 81 of well known construction. Further secured to the support 82 is a work pressure foot 83 having a base 84 cooperating with the feed dogs 1 and 2, said base having recesses 84 transversed by the teeth 86 of the feed dog 79 engaging the upper surface of the fabric or work piece during the feeding operations.

Mounted in the hollow pressure foot bar 81 is a rod 87 which carries at its lower end a pin 89 rotatively engaging a fork 88 of the feed dog 79, said rod being operated axially in an up and down movement for effecting the necessary rise and fall movements of the feed dog 79, in addition to the horizontal displacement effected by the lever 77. A crank 90, FIG. 1, secured to the arm shaft 69 is operably connected, through a link 91, to a needle bar 94 carrying the needle 92 and mounted for reciprocation in the needle guide or frame, in a manner well known in the construction of conventional sewing machines.

The reciprocatory needle 92, FIG. 2, cooperates in a known manner with a loop taker (not shown) disposed below the work support or stitching plate 95, to form lock stitches in the work being operated on. The support 95 is provided, in front and behind the needle 92, or stitching hole 96, with slots or recesses 97 and 98, to enable free passage of the feed dogs 1 and 2 while moving in the up and down direction, respectively. The feed dogs are arranged in such a manner that the main feed dog in cooperation with the base 84 of the presser foot 83 engages the fabric behind the needle or stitching hole, while both auxiliary feed dogs 2 and 79 engage the work in front of the needle, as viewed in the feeding direction.

The operation of the multiple work feeding mechanism as shown by the drawings will be described in greater detail in the following.

Simultaneous variation of the absolute feed strokes of all the three

feed dogs

1, 2 and 79, determining the stitching length, is effected by rotation of the stitch controller disk 57, this resulting, in turn, in the rotation of the adjusting shaft 26, through the action of the spring 58, until the lever 54 linked to said shaft engages the wall of the groove 56 of the disk 57 for effecting feeding of the work piece or fabrics in the forward sewing direction.

Rotation of the adjusting shaft 26, in turn, entails a corresponding rotation of the lever 25, resulting in a relative displacement or misalignment of the pin 24, acting as pivot axis of the link 20, relative to the pin 22, acting as pivot axis of the link 21, from an assumed initial aligned position of said pins, as shown in the drawing. As a consequence, the oscillations of the pin 19 by the eccentric 13, while causing the link 20 to perform a purely rotary movement about the pin 24, results in the link 21 to perform, aside from said rotary movement, an additional relative rotation about the shaft 15. This relative movement is, in turn, imparted, by way of lever 23, as oscillating or rocking movement to the lever 17, whereby to apply translatory feed movement to the main feed dog 1 by way of the feed bar 3. The extent of the feed movement or feed stroke depends upon the degree of relative displacement of the pins 22 and 24 from their aligned position, that is, upon the rotational adjustment of the stitch controller or disk 57. The latter may be fitted with a suitable indicator scale directly showing the feed stroke or stitching length, respectively.

Rotation of the adjusting shaft 26 by the stitch controller 57 simultaneously results in rotation of the adjusting shaft 34 by way of the fork member 35, setting screw 40 and fork member 36. As a consequence, lever 33 being fast on shaft 34 causes rotation of link 28, whereby to displace the pin 32 relative to the pin 30, in a manner analogous to the relative displacement of the pins 22 and 24 as previously described. As a consequence, the oscillations of the pin 27 by the eccentric rod 14 cause the link 29, for the same reasons as described in connection with the operation of the parts 19 and 25, to perform, aside from a rotating movement about the pin 32, a relative rotation about the shaft 16. This relative movement, in turn, results in an oscillating movement of the shaft 16, and, in turn, in translatory feed movements being applied, by way of lever 18, to the feed bar 4 of the auxiliary feed dog 2.

Rotation of the fork member 35 furthermore causes, by way of the setting screw 41, fork member 38, lever arm 60, link 61, and lever arm 62, a corresponding rotation of the setting shaft 63. A a consequence, the bracket 64 being fast on shaft 63 rotates bracket 65, whereby to relatively displace pins 66, acting as pivot axis for the bracket 65, relative to the pin 72, whereby, as a result of the oscillations of the pin 67 by the eccentric rod 69 and in analogy to the previously described adjusting arrangement of the shafts 26 and 43, bracket 65 performs a pure rotational movement about the pins 66, while the link 73, aside from said rotational movement performs an additional relative movement about the oscillating shaft 74, whereby to oscillate the latter by way of the lever arm 73. This oscillating movement of the shaft 74 is applied as horizontal feed movement to the upper feed dog 79 through lever arm 75, link 76 and lever 77. The up and down component of the upper feed dog 79 by the pin 82 may be effected by any suitable means (not shown) operably connecting the drive shaft 69 with said pin, in a manner readily understood.

Rotation of the setting screw 40 results in the fork member 36 being displaced relative to the fork member 35. This, in turn, results in a corresponding displacement between the scale 48 and index mark 50, whereby to indicate the degree of displacement of the setting shaft 34 connected to the member 36 and, in turn, of the feed differential between the auxiliary feed dog 2 and the main feed dog 1.

Similarly, rotation of the setting screw 41 results in the displacement of the fork member 38 relative to the fork member 35 and, in turn, in rotation of the setting shaft 63 by way of the link 61 and lever arm 62. The degree of displacement of the shaft 63 relative to the setting shaft 26, that is, the feed differential between the main feed dog 1 and the auxiliary feed dog 79, is indicated by the scale 49 and index 51.

Referring to FIG. 3, there is shown a seam being sewn in a pair of superposed fabric layers or workpieces 99 and 100, the seam configuration corresponding to the instant where the needle 92 penetrates the work during its downward operating stroke. At this position, the

feed dogs

1, 2 and 79 have arrived in their upper end position and start their withdrawal from the fabric, or downward movement in a manner well known. During the feeding of the fabrics 99 and 100 by the main feed dog 1, both fabric layers are advanced by a stitching length by said dog engaging the lower surface of the fabric layer 100. As a consequence, the mating or contact planes of the layers are slightly displaced relative to one another as a result of the friction between the base 84 of the presser foot 83 and the upper layer 99, the relatively small friction between the layers 99 and 100, and the elasticity of the material. As a consequence, the

sections

101 and 102 of the stitches sewn by the

threads

103 and 104 assume a rearwardly inclined position, as viewed in the feeding or sewing direction and shown in the drawing. In order to stretch both layers 99 and 100 prior to a stitch formation, the feed strokes of both auxiliary feed dogs 2 and 79 are adjusted to be less than the feed stroke of the main feed dog 1. Besides, in order, furthermore, to effect a greater degree of stretching of the lower layer 100, the feed stroke of the lower auxiliary feed dog 2 is adjusted to be less than the feed stroke of the upper auxiliary feed dog 79, whereby the two layers 99 and 100 will be additionally displaced by a slight amount at a point ahead of the needle and in a direction opposite to the normal displacement as a result of the feed movements, in the manner described. Provided a proper choice of the feed differential between the upper auxiliary feed dog 79 and the lower auxiliary feed dog 2, the fabric layers 99 and 100, while being stretched to diflferent degrees, will remain, immediately in the vicinity of the stitching point, in a condition of relative non-displacement so as to be penetrated by the needle in their original relative position.

Immediately upon the withdrawal of the

feed dogs

1, 2 and 79, the fabric layers return to their original (untensioned) condition as a result of the elasticity of the material, whereby, upon advance to a position for the next downward stroke of the needle or commencement of a new stitching operation, the aforedescribed operation willvbe repeated. In this manner, the sewing of a uniform seam may be ensured substantially without any residual differential stresses in the material, liable to result in the formation of crirnps or the like irregularities of the seam being sewn.

When using highly

elastic threads

103 and 104, it is furthermore desirable, if not necessary, to stretch the layers 99. and 100, by the action of the auxiliary feed dogs 2 and 79 and while maintaining a desired feed stroke differential between said dogs, to an extent as to cause the

threads

103 and 104 to return to their completely untensioned condition upon relaxation of the layers 99 and 100.

In the foregoing the invention has been described in reference to a specific illustrative device, or embodiment. It will be evident, however, that variations and modifications, as well as the substitution of equivalent parts or elements for those shown herein for illustration, may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.

I claim:

1. The combination with a sewing machine having a work support, a work pressure foot above said support, and stitch-forming tool means including a reciprocatory needle, to sew a pair of superposed fabric workpieces fed between said support and said pressure foot, of work feeding mechanism comprising in combination:

(1) a first feed dog disposed below said support and behind said needle, as viewed in the feeding direction, said feed dog having first operating means, to intermittently engage and feed said workpieces,

(2) a first rotary adjusting shaft operably associated with said first operating means, to adjust the feed stroke of said first feed dog in proportion to the angular position of said first adjusting shaft,

(3) a second feed dog also disposed below said support and in front of said needle, as viewed in the 8 feeding direction, said second feed dog having second operating means, to intermittently engage and feed said workpieces in synchronism with said first feed dog,

(4) a second rotary adjusting shaft operably associated with said second operating means, to adjust the feed stroke of said second feed dog in proportion to the angular position of said second adjusting shaft,

(5) a third feed dog disposed above said support in front of said needle, as viewed in the feeding direction, said third feed dog having operating means, to intermittently engage and feed said workpieces in synchronism with said first feed dog,

(6) a third adjusting shaft operably associated with said third operating means, to adjust the feed stroke of said third feed dog in proportion to the angular position of said third adjusting shaft,

(7) uni-control operating means for said first, second and third adjusting shafts, to simultaneously vary the absolute feed strokes of said first, second and third feed dogs, and

(8) further plural adjusting means interposed between said first adjusting shaft and each of said second and third adjusting shafts, to individually adjust the respective feed stroke differentials between said second and third feed dogs relative to said first feed dog.

2. In work feeding mechanism for sewing machines as claimed in claim 1, said plural adjusting means being comprised of a pair of adjustable couplings between said first adjusting shaft and each of the said second and said third adjusting shafts.

3. In work feeding mechanism for sewing machines as claimed in claim 1, said plural adjusting means being comprised of a pair of adjustable couplings between said first adjusting shaft and each of said second and third adjusting shafts, and individual cooperating scale and index means, to indicate the angular positions of said second and third adjusting shafts relative to said first adjusting shaft.

References Cited UNITED STATES PATENTS 3,202,121 8/1965 Orth et al. 112209 3,198,154 8/1965 Reeber 112206 X 1,118,321 11/1914 Weis 112-209 RICHARD J. SCANLAN, 1a., Primary Examiner.