US2820426A - Articulated presser foot - Google Patents

Description

Jan. 21, 1958 J. DOERR ETAL 2,820,426

ARTICULATED PRESSER FOOT Filed Aug. 15, 1955 JOHANNES DOERR HANS OTTO MEUTH MMEZYMM ATTORNEY' United States Patent "ice ARTICULATEID PRESSER FOOT Johannes Doerr and Hans Otto Meuth, 'Kaiserslautern', Germany, assignors to G; M. Pfafi. A.- G., Konigstrasse, West'Germany, a corporation of West Germany Application August 15, 1955;Serial No. 528,449 Claims priority, application Germany'August 16, 1954 4 Claims. (Cl. 112-212) This invention relates to sewing machines of'the type having compound feed and alternating pressers and'in particular provides a feed device for such asewing machine having particular applicability to sewing smooth fabrics.

In sewing smooth elastic materials, such as fabrics woven from synthetic fibers with sewing threads of the same :material, when employing standard sewing machines it will be commonly observed that the sewn material tends to pucker along the stitching. This puckering effect occurs with two variations. In one case the puckering iscaused by shifting ofthe separate layers of materials being sewn. This variety of puckering can be conveniently designated long-wave puckering. A sec and. variety of puckering is the result of the inherent elasticity of the threads and of displacement of the point at which the threads lock. This variety of puckering can conveniently be designated short-wave puckering.

A sewingmachine utilizing compound feed and alter= nating pressers counteracts long-wave puckering since itdoes. not permit the separate layers of material being sewn to shift relative to each other. Such a machine iscapahle, moreover, of a differentiation between the movement of the feed above the table andthe feed beneath the table. minimized by transferring the point at which the threads" lock to the underside of the material being sewn and by employing small diameter thread. The elasticity of the threads, howeven'continues to cause-puckering of the short-wave variety and thus is maximized by the use of smaller diameter threads since elastic stretch is inversely proportional to the diameter of the thread. Such puckering caused by the elastic stretch of the sewing threads occurs particularly when the stitch is being tightened...

The sewing-threads after locking return'to approximately unstretched position and in'doing so pucker the material being sewn. Some residual tension of the sewing threads moreover remains and cannot be equalized by pressing.

It has heretofore been proposed to employ a feed devicewhich stretches the material being sewn at the point at which the stitch is taken. Such a device includes an auxiliary foot which is capable of movement relative to needle bar and feed and which is positioned forward of the needle audismoved against the direction of feed in order to effect a stretch of the material being sewn. The use ofsuch an auxiliary foot, however, tends to produce displacement between the upper and lower layers of Short-wave puckering has heretofore been 232M226 Patented, Jan. 21, 1958 This invention contemplates the use-or an articulated inside presser, foot having a fixed toe cooperating with the feed dog extending forward of the'needle and through which the needle passes in a manner similarnto the conventional inside presser foot but also having a heel capable of movement .relativeto the toe and positioned behind the needle cooperating" with-the throat plate. Divergent movementofheel'and'toe' is produced at the time ea'c'hstitch is takenfinjorder tostreteh the material at the point of the needle strokewithout'producing a dis-- placement between the "upper andPlower layers of material being sewn which remains after the "stitch istaken.

In particular, thisinvention contemplatesthat the toe and heel of the inside presser" foot are articulated with an arm atiixed to the rear ofthehel'exteriding in sliding engagement with the outside-fpresserbar, in sucha -mannerj that the lifting movement of the outside-pres'ser with'a feed'deviee in accordance with this invention;

Fig. 2 is an enlarged perspective 'view of theartic'u l'ated inside presser toot constructed-in accordance with this invention 'and employed inthe sewing machine shown in Fig. 1;

Fig.3 is an enlarged fragmentaryvie'w' of'the sewing machine shownin Fig. 1 illustrating in particular one position of the feed device of this invention;

Fig. 4'is a vie'w similar tothatshownin Fig. 3 showing a secondp'osition-of the feed device;

Fig. 5 is a-view similarto thatshown'inFig's'. 3 and 4 showing a thirdposition or the feed device; and

Fig.-'6'is an enlarg'e'djprspective view 'of the outside presser foot shown in Figs. 1-, 3, 4- and 5.

In the drawings the reference numeral 10 designatesa sewingmachine including. a work table orbase plate 11,

a vertical-upright 1'2 mountedon base'platefl, an'arrn material being sewn with the result that long-wave puckering is increased.

It is a primary object of this invention to provide a feed device for use in sewing machines having com- 13 supported at one end by upright 12 over the surface of work table '11 and asewing head 14 positioned on the end of arrn '13 remote'from upright 12'.

Arranged in sewing head-14 is 'a needle barlS which is vertically 'r'eciprocable in and depends at its lower endfromarocking doubleguide sleeve lo-pivotally con-- nected atits upper end tosewinghead 14 to permit move-- ment of sleeve 16 through an arc in-a plane extending transversely across base plate-1'1 and aligned with the direction of feed. Needle bar 15- is connected to acrank shaft- (not shown) of conventional construction which causes needle bar 15 to'reciprocate vertically and'to drive a needle 17, secured in the lower end of needle bar 15 into andout of an opening in throat plate 18. Throat ates with a rotary hook 19 in orderto produce a conven-- tional lock stitch.- A power take-off (not'shown) from" the crank shaft having an eccentric movement is con nected to sleeve 16 to" cause itto oscillate about it's top An'insidepresser bar 20 is'also'mountedinand de' pends at its lower end from sleeve 16 torverticalrecipro eating movement. The lower endof inside-'presser bar 20' carries *aninsidepresse'r foot 21 whicl'1-- cooperates,

as will be described hereinafter with reference specifically to Figs. 3, 4 and 5, with the feed dog 22 to pull material across work table 11 and at the same time cooperates with throat plate 18 to stretch the material as it is stitched.

To the rear of needle bar 15 and inside presser bar 20 is the outside presser bar 23 which is mounted for vertical sliding movement in head 14. The lower end of outside presser bar 23 projects below head 13 and carries an outside presser foot 24 which cooperates with throat plate 18 to hold the material being sewn in fixed position. A heavy helical spring 25 is positioned about the end of outside presser bar 23 and bears at its lower end against a presser bar block 26 which is alhxed to outside presser bar 23.

Presser bar block26 carries a bearing bolt (not shown) which extends horizontally and lengthwise of sewing arm 13 toward the outer end of head 14. This bearing bolt rotatably carries the center of bell crank lever 27, one arm 28 of which is connected by link 29 to crank arm 30 of shaft 31 supported on sewing arm 13 in journals 32. The remote end (not shown) of shaft 31 is provided with a similar crank arm and link (not shown) which engage an eccentric on the main crank shaft and thus an oscillating movement is imparted to shaft 31 during operation of sewing machine 10. The other arm 33 of hell crank lever 27 is pivotally connected to the upper end of inside presser bar 20. The bearing bolt on presser bar block 26 which supports bell crank lever 27 bears at its outer end in a vertical guide slot on the inside face of guide plate 36 afiixed on the end of head 14.

The oscillating movement of shaft 31 produced during operation of sewing machine causes a similar oscillating movement of bell crank lever 27. As this movement of bell crank lever 27 approaches its clockwise limit, as seen in Fig. 1, arm 33 bears down against the upper end of inside presser bar 20, the foot 21 of which is resting firmly on feed dog 22. Thus, further movement of hell crank lever 27 in a clockwise direction lifts outside presser bar 23 and its foot 24 above throat plate 18. As the same oscillating movement of bell crank lever 27 is reversed and approaches its counterclockwise limit, as seen in Fig. l, the central pivoted part of lever 27 forces down against outside presser bar 23 to cause outside presser foot 23 to bear against throat plate 18, and further counterclockwise movement thereby lifts the forward end of arm 33 carrying with it inside presser bar 20 to remove inside presser foot 21 from feed dog 22 clear of work table 11. It is apparent therefore that the vertical movement of the inside and outside presser bars is alternating.

The timing of the vertical reciprocation of needle bar and of the transverse movement of feed dog 22 cooperates with this alternating movement such that as needle 17 is plunged through the opening in throat plate 18, to cooperate with hook 19, sleeve 16 carrying both needle bar 15 and inside presser bar is oscillated toward the rear as seen from the operators side of the machine. Simultaneously, feed dog 22 is in its upper position and moves toward the rear of the machine. At the same time outside presser bar 23 is raised and holds foot 24 above throat plate 18. As sleeve 16 reaches its rearward limit of movement, outside presser bar 23 and presser foot 24 drop. At the same time feed dog 22 is lowered and removed to the forward position and inside presser bar 20 and presser foot 21, and needle bar 15 and needle 17 are raised and move forward. In this action the material is alternately pulled and held firm and the stitch is taken during the pulling movement.

Insofar as sewing machine 10 has been described above, its construction is conventional and the description has necessarily been limited to such details as are necessary for a complete understanding of the operation of the feed device of this invention.

The feed device of this invention is shown most learly in Fig. 2 and includes articulated inside presser foot 21. Inside presser foot 21 is formed of a shank 40 which receives the lower end of inside presser bar 20 and which carries at its lower end an integral, forwardly projecting toe 41. The lower end of shank 40 to the rear of toe 41 is provided with a vertically elongated transverse opening 42. The rearward end of toe 41 is provided with a vertical opening 43 positioned to register with the usual elongated opening in throat plate through which needle 17 passes in cooperating with hook 19. The underside of toe 41 is provided with a knurled surface to increase its frictional grip on the material in feeding and stretching operations. Beneath shank 40 and to the rear of toe 41,

foot 21 is provided with an articulated heel 45 having a knurled undersurface similar to the undersurface 44 of toe 41.

The articulating connection between the body of foot 21 and heel 45 includes a bell crank lever 47 which is pivotally connected at its center by means of pin 48 with its central portion located in vertically elongated opening 42. One end of lever 47 depends from shank 40 and is received in a slotted opening 49 in the upper surface of heel 45 and secured in pivotal connection to heel 45 by means of pin 50. The other end of bell crank lever 47 projects to the rear of presser foot 21 and terminates in an enlarged portion 51 having a large vertical opening 52 which receives the shank 53 of outside presser foot 24. The sides of enlarged portion 51 are each provided with diagonal transverse slots 54 which are aligned and which receive a pin 55 extending through shank 53 of foot 24.

In operation, just prior to taking a stitch, outside presser foot 24 rests on throat plate 18 and inside presser foot 21 and needle 17 are withdrawn upwardly above the surface of work table 11 and are positioned with sleeve 16 extending rearwardly. This position is shown in Fig. 3. In it, because presser foot 21 is elevated relative to presser foot 24, heel 45 is also raised slightly above throat plate 18.

Thereafter sleeve 16 moves towards its forward position, and at the same time bell crank lever 27 rotates clockwise, lowering toe 41 of inside presser foot 21 onto the upper surface of feed dog 22, which has also traveled to a forward position with its knurled upper surface raised through the usual elongated openings in throat plate 18. Needle bar 15 is also lowered and needle 17 moves downwardly to take the stitch. This initial stitch position is shown in Fig. 4. In it, it will be apparent that heel 45 at this point rests securely on the upper surface of throat plate 18 and toe 41 rests on feed dog 22. Outside presser foot 24 is at the point of being raised.

Thereafter as outside presser foot is raised clear of throat plate 18, needle 17 continues downward piercing the material being sewn and cooperating with hook 19 to lock the stitch. At the same time needle bar 15, needle 17, inside presser bar 20 and inside presser foot 21 are drawn rearwardly by sleeve 16 and cooperate with feed dog 22 to pull the material through the machine and the stitch is taken. The relative upward movement of outside presser bar 23 to inside presser bar 20 by engagement of pin 55 in slots 54 causes heel 45 to move rearwardly relative to toe 41. Consequently, as the material being sewn by needle 17 is stitched through the feeding movement which terminates in the position shown in Fig. 5, maximum tension is placed upon the material being sewn so that, after the stitch is taken and the pressers alternate, the subsequent release of the stitched material synchronizes with the release in tension on the sewing thread, and material and thread return to unstretched position simultaneously without puckering of the material and without unduly loosening the thread. At the same time, because the needle remains in the material being sewn as the feeding movement takes place, an additional safeguard is provided against relative displacement of the upper and lower layers of material being sewn.

From the preceding description it will be apparent that the articulated inside presser foot of this invention can also readily be designed in such a manner as will permit its use with differently constructed needle bars and presser bars, provided that care is taken that the toe always is in front of the needle and the heel behind it.

We claim:

1. In a sewing machine including means defining a work surface, a sewing head supported above said work surface, a presser bar slideably mounted in said head with one end projecting from said head toward said work surface, a needle bar slideably mounted in said head to the front of said presser bar with one end projecting toward said work surface, a needle attached to said end of said needle bar for passing thread through material being sewn, means for reciprocating said needle bar, means for reciprocating said presser bar, and means for oscillating said needle bar and presser bar from front to rear when said needle bar and presser bar are reciprocated toward said work surface, the improvement which comprises a presser foot attached to said end of said presser bar having a toe extending to the front of said needle for cooperating with said work surface to feed material being sewn beneath said head over said work surface, said presser foot further including an articulated heel cooperating with said work surface to move material being sewn and movably attached to said presser foot to the rear of said needle, and means for moving said heel to the rear relative to said toe as said toe moves from front to rear whereby said material is stretched at the point said needle penetrates the material as a stitch is taken.

2. In a sewing machine including means defining a Work surface, a sewing head supported above said work surface, an inside presser bar slideably mounted in said head with one end projecting from said head toward said work surface, an outside presser bar slideably mounted in said head to the rear of said inside presser bar with one end projecting toward said work surface, a needle bar slideably mounted in said head to the front of said inside presser bar with one end projecting toward said work surface, an outside presser foot attached to said end of said outside presser bar for cooperating with said work surface to hold material being sewn, a needle attached to said end of said needle bar for passing thread through material being sewn, means for reciprocating said needle bar, means for reciprocating said outside and inside presser bars alternately, and means for oscillating said needle bar and inside presser bar from front to rear when said needle bar and inside presser bar are reciprocated toward said work surface and said outside presser bar is reciprocated away from said work surface, the improvement which comprises an inside presser foot attached to said end of said inside presser bar having a toe extending to the front of said needle for cooperating with said work surface to feed material being sewn beneath said head over said work surface, said inside presser foot further including an articulated heel cooperating with said work surface to move material being sewn and movably attached to said inside presser foot to the rear of said needle, and means operatively connected to said outside presser bar for moving said heel to the rear relative to said toe as said toe moves from front to rear whereby said material is stretched at the point said needle penetrates the material as a stitch is taken.

3. The improvement according to claim 2 in which the operative connection between the heel of the inside presser foot and outside presser bar includes a bell crank lever pivotally connected at its center to the inside presser foot having said heel pivotally connected at one end of said lever and having an extension at the other end of said lever which slideably engages the outside presser bar.

4. The improvement according to claim 2 in which said sewing machine further comprises a feed dog moving in the work surface cooperating with the toe of the inside presser foot to draw material being sewn across the work surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,128,519 Rontke Feb. 16, 1915 1,474,966 Hayes Nov. 20, 1923 2,426,636 Monroe Sept. 2, 1947 2,474,282 Sailer June 28, 1949 FOREIGN PATENTS 400 Great Britain of 1888

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