US2750905A - Attachment for sewing machines - Google Patents

Description

June 19, 1956 c. H. WURKER 2,750,905

ATTACHMENT FOR SEWING MACHINES Filed April 22, 1952 er m'yw ATTACHMENT FOR SEWING MACHINES Carl Heinz Wiirker, Aistaig (N eckar), Germany Application April 22, 1952, Serial No. 283,613

Claims priority, application Germany February 25, 1950 6 Claims. (Cl. 112-160) The present invention relates to an attachment intended to be mounted on sewing machines, especially of the domestic type, and enabling the production of zigzag seams, button hole stitches and the like on such simple machines.

The invention relates more specifically to such attachments which are equipped with an actuating lever driven by the vertically moving needle bar of the sewing machine in such a manner that the said lever oscillates in a vertical plane. At the same time the actuating lever turns about and, via a pawl and ratchet drive, transmits to a horizontal cam shaft a step-by-step rotational motion in response of which a rocking lever provided with a presser plate reciprocates transversely to the direction in which the material to be sewn travels, said reciprocating motion being transmitted to the material which is to receive a zigzag seam, and causing the said material to reciprocate transversely to the direction in which it travels.

It is the object of the present invention to make available new and useful improvements in attachments of the aforementioned kind, which are clearly set forth and illustrated in the accompanying drawing of which Fig. 1 is a side elevation from the right of the attachment which is the subject of the present invention, on a slightly enlarged scale;

Figs. 2 and 3 show different working positions of the driving pawls and control ratchets with the aid of which the actuating lever drives the horizontal cam shaft of the attachment;

Fig. 4 is an axial sectional view roughly on the line 1-4 of Fig. 1;

Fig. 5 is a section of the pawls and controlling ratchets roughly on the line 5-5 of Fig. l, on a more enlarged scale;

Figs. 6 and 7 are separate views of the pawl and controlling ratchet.

The head 10 of a domestic sewing machine is indicated by dot-dash lines, the needle bar 11 and the presser bar 12 moving vertically in the said head. The lower end 13 of the conventional lever serves to raise and lower the presser bar 12. Instead of the conventional presser foot, the support 14 of the attachment casing is fastened to the presser bar 12, so that the attachment can be lowered onto or raised from the material together with the presser bar 12.

The casing of the attachment is made of a U-shaped piece of sheet metal with the two side walls 15 and 16 and the bottom 17. A sheet metal strip 18 bent to adapt itself to the contour of side walls 15 and 16 forms the cover of the casing. In the side walls 15 and 16 a horizontal shaft 19 is supported on which a cylinder cam 20 is arranged in the interior of the casing. Along the periphery of the cylinder cam runs a groove 21, which is essentially of wave-lined contour. A vertical trunnion 22 engages in the groove 21 (Fig. 4), and a friction reducing cam roller 23 is pivotally mounted on said trunnion 22 which is fastened to the rear end (in Fig. l on States Patent 0 2,750,905 Patented June 19, 1956 Ice the right-hand side) of a rocking lever 24 being so mounted on a pivot 25 (Fig. 1) that the action of the cylinder cam 20 causes the rocking lever 24 to oscillate in an approximately horizontal plane. The pivot 25 is fixed to a slide 26 which can be adjusted lengthwise of the casing and which is held in place by a Screw 27 (Fig. 1). Thus, with the aid of slide 26, the pivot can be adjusted to a greater or smaller distance from the trunnion 22, which allows reduction or increase in the angular movement of the forward end 28 (in Fig. 1 lefthand end) of the lever. The forward end 28 of the lever is forked and carries a presser plate 29 which is so fixed to the fork 23 that it hinges around pin 30.

T he shaft 19 of the cylinder cam 20 is given a step-bystep rotational motion from the needle bar 11. To this end an actuating lever 31 is mounted on and pivots loosely around shaft 19 (Figs. 1 and 4), the free end 32 of the actuating lever being bifurcated and engaging with a sidewise projecting pin 33 of the needle clamp. With the aid of the needle clamp the needle 34 is clamped on the needle bar in the usual manner (Fig. 1). Thus, lowering the needle bar 11 causes the actuating lever 31 to swing downwards around the shaft 19, and raising the needle bar 11 causes the lever to swing upwards.

These oscillating rotational movements of the actuating lever 31 are transmitted to the shaft 19 by a driving pawl 35 whose projection 36 (Fig. 6), with the pawl (Fig. 1) being in working position, is forced by a spring 37 into the gaps between the teeth of a ratchet wheel 38. The ratchet wheel 38 is mounted on a square 39, or a similar arrangement, of shaft 19 (Fig. 4). Although only one driving pawl 35 is shown in the drawing, a plurality of such driving pawls can naturally be provided, if this should be of advantage.

With a view to obtaining timed harmony of the movements of the rocking lever 24 with those of the needle bar 11 of the sewing machine in a simple and easy manner, the trunnion 40 of the driving pawl 35 is mounted on a supporting plate 41 which is separate from and connected to the actuating lever in such a manner that the supporting plate can be rotated in relation to this lever around the shaft 19 as the centre of rotation. To this end the supporting plate 41 is provided with arcuate slots 42, through which screws 43 extend which permit rigidly connecting the supporting plate 41 with the actuating lever 31 (Figs. 1 and 4). For functional reasons the slots 42 are made so long that the supporting plate can be rotated in relation to the actuating lever 31 through one graduation of the ratchet Wheel 38, i. e., the angle subtended by each slot corresponds to the angle subtended by each graduation of the ratchet wheel. By turning the supporting plate 41 in relation to the actuating lever 31 engaging with the needle bar, it is possible to adjust the driving pawl 35 in relation to the ratchet wheel 38 in such a manner that the transverse movements of the rocking lever 24 occur exactly when the needle 34 has released the material to be sewn.

Certain attachments of the hereindescribed kind have in addition to the driving pawl 35 an auxiliary pawl 44 (Figs. 1, 2, 3, 5 and 7) coacting as a control lever with the driving pawl 35, Whilst its projection 45 coacts with a camming ratchet wheel 46 which is arranged alongside of and coaxially with the ratchet wheel 38 on the cylindrical portion of a retaining screw 47 fixed in the shaft 19, the camming ratchet wheel being capable of turning freely on the said cylindrical portion. The auxiliary pawl 44 is pivotally mounted on the trunnion 40 of the driving pawl 35. The camming ratchet wheel 46 is held in its position on the shaft 19 and protected against axial displacement by screw 47 and a spring plate 48. The teeth of the'camming ratchet wheel are of different height.

Some teeth are as high as those of the ratchet wheel 38 while others are essentially higher. The auxiliary pawl 44 can be rigidly coupled to the driving pawl 35. To this end the auxiliary pawl 44 is equipped with a coupling pin 49 protruding towards the driving pawl 35, while the driving pawl has a hole 50 in which the pin 49 can engage to effect positive shifting (Figs. 1, 2 and When the auxiliary pawl 44 is thus positively linked with the driving pawl 35, its projection 45 does not mesh with the teeth of the camming ratchet wheel (Fig. l). The projection 36 of the driving pawl 3'5, however, meshes permanently with the teeth of the ratchet wheel 38, thus giving the ratchet wheel a clockwise step-by-step rotation at each upward stroke of the actuating lever 31. As a result thereof, a uniformly reciprocating motion is transmitted to the rocking lever 24, so that a uniformly wide zigzag seam is produced. The auxiliary pawl 4-4 and the driving pawl'35 connected with it, can also be brought in the inoperative position shown in Fig. 2, the two pawls being in said position out of engagement with the camming ratchet wheel 46 or the ratchet wheel 38, respectively. If this is the case the movements of the actuating lever 31 do not act on the shaft 19 and the rocking lever 24, the latter therefore remaining immobile. In this case a plain straight stitch is produced since the material to be sewn is transported in a straight line. If, however, the coupling pin 49 is withdrawn from the hole 50 of the driving pawl 35 by axially displacing the auxiliary pawl 44 on its trunnion 40, as is indicated by dot-dash lines in Fig. 5, and if the auxiliary pawl 44 is rotated in relation to the driving pawl 35 in such a manner that the pin will be located underneath the lower edge of the driving pawl 35 (Fig. 3), then the projection 45 of the auxiliary pawl 44 can be brought in touch with the differently elevated teeth of the camming ratchet wheel 46 by shifting the auxiliary pawl from the disengaged position in the direction of the arrow 51. As long as the auxiliary pawl 44 remains in touch with the higher teeth of the camming ratchet wheel 46, the driving pawl 35 being shifted in the same direction of rotation relative to the ratchet wheel 38, cannot mesh with the teeth of the ratchet wheel 38 because it is prevented from doing so by the pin 49. Thus, every upward stroke of the actuating lever '31 causes only the camming ratchet wheel 46 to move on around the screw 47, whilst the ratchet wheel 38 and the rocking lever 24 remain immobile. In this manner plain straight stitches are produced. As soon as the auxiliary pawl 44, however, comes in touch with the low teeth of the camming ratchet wheel 46 as a result of the continued rotation of said wheel, the driving pawl 35 can engage with the teeth of the ratchet wheel 38 and,

as the actuating lever 31 moves upwards, the driving pawl 35 transmits to the ratchet wheel 38 a rotational motion, so that at this moment the rocking lever 24 starts to move and to produce zigzag stitches. With the pawls 35 and 44 in the described position an ornamental seam is produced consisting of alternating rows of plain stitches and zigzag stitches. Since in this case the two pawls 35 and 44 are non-positively linked together, owing to the pin 49 only loosely engaging the lower edge of the driving pawl 35, said pawl being held in disengaged position by the hooked end of the spring 37 (Figs. 2 and 3), the driving pawl 35 in the known attachments of the hereindescribed kind had to be shifted towards the ratchet wheel 38 by finger pressure on the upper edge of the said pawl 35, in order to engage the driving pawl 35 with the teeth of the ratchet wheel 38. This frequently caused damage to the spring 37 or displaced said spring from its correct position. According to the present invention the driving pawl 35 is therefore provided with a projecting portion 52 protruding towards the auxiliary pawl to the exterior. The projecting portion 52 thus extends into the path of a driving portion of the auxiliary pawl 44, and engages and moves along with the latter, as soon as the auxiliary pawl 44 is shifted in the direction of the arrow 51 (Fig. 3) towards the camming ratchet wheel 46. Preferably the projecting portion 52 of the driving pawl 35 is so arranged that it extends as a stop into the arcuate path of the handle 53. This handle can therefore be used as a driving means for the driving pawl 35, and the auxiliary pawl need not be equipped with a special driving portion.

Finally, a rim 54 (Fig. 5) is arranged at right angles to the plane of the supporting plate 41 on the said supporting plate above the driving pawl 35 in such a manner that the pawl and ratchet drive, particularly the driving pawl 35, and, as the case may be, the auxiliary pawl 44 as well, are protected against being touched from above by an arrangement similar to an extension roof, to protect these parts against damage caused by the carelessness of the operator or by the impact of the presser lever 13 when it snaps down.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

l. A zigzag attachment for sewing machines equipped with a presser bar and an oscillating needle bar; comprising cam means, plate means, shaft means, ratchet wheel means, actuating lever means, said shaft means being common to and supporting said cam means, said ratchet wheel means and said actuating lever means, rocker arm means for engagement with the material to be sewn and operatively connected to said cam means, whereby actuation of said cam means produces reciprocation of said rocker arm means in a substantially horizontal plane, pawl means pivotally mounted on said plate means, spring means secured on said plate means and normally urging said pawl means into operative engagement with said ratched wheel means, said plate means and said actuating lever means being loosely seated on said shaft means to permit relative rotational displacement of said shaft means, and adjustable means connecting said plate means to said actuating lever means, whereby the angular po* sition of said plate means relative to said actuating lever means may be varied, said actuating lever means being provided with an end for engagement with said needle bar, whereby reciprocation of said rocker arm means may be synchronized with the oscillation of said needle bar by varying the angular position of said actuating lever means relative to said plate means through actuation of said adjustable means, the disposition of said pawl means and of said spring means relative to said ratchet wheel means remaining unchanged during variation of said angular position.

2. In a zig-zag attachment according to claim 1, said plate means being provided with slots, and means passing through said slots for securing said plate means in predetermined position relative to said actuating lever means.

3. In a zig-zag attachment according to claim 1, said plate means being provided with a plurality of arcuate slots, and screw bolts passing through said slots and securing said plate means in predetermined position relative to said actuating lever means, the length of each slot corresponding to one graduation of said ratchet wheel means.

4. In an attachment for sewing machines adapted to produce zig-zag stitches; a pivoted actuating lever adapted to be attached at one end to the needle bar of the sewing machine, whereby reciprocating movements of said needle bar will produce oscillating movements of said actuating lever, a shaft on which a ratchet wheel is mounted, a pawl engageable with and securing step-bystep rotational movement of said ratchet wheel and of the shaft, a cam mounted on said shaft, a rocker arm for engagement with the material to be sewn, means on the rocker arm engaged by the cam for causing oscillating movements of the rocker arm in a substantially horizontal plane, a support for the pawl comprising a plate pivotally mounted on the ratchet shaft and rotationally adjustable with respect to the actuating lever, means for connecting said plate to said actuating lever in ditferent angular positions with respect to each other, spring means for holding the pawl in engagement with said ratchet wheel, said spring means being supported by the same plate supporting said pawl, and a casing pivotally supported about said shaft adapted to be attached to the presser bar of the sewing machine.

5. In an attachment for sewing machines according to claim 4, said plate including a rim extending substantially horizontally over said pawl and spring means.

6. In a zig-Zag attachment for a sewing machine having a presser bar and an oscillating needle bar; a casing connected to said presser bar, a shaft extending through said casing and capable of rotational displacement relative to said casing, a cam secured to said shaft within said casing and provided with a peripheral track, a trunnion guided in said track and extending from within said casing therewithout, a rocker arm secured to said trunnion exteriorly of said casing, whereby rotation of said shaft and said cam secured thereto causes said cam track to move past said trunnion guiding the latter and imparting a re ciprocating motion in a substantially horizontal plane to said trunnion and to said rocker arm secured thereto, a plate freely disposed about said shaft exteriorly of said casing and provided with a horizontally extending rim, an actuating lever freely disposed about said shaft exteriorly of said casing and remote from said rim of said plate and provided with an end adapted to be attached to said needle bar, arcuate slots and bolts being provided on said plate and on said actuating lever for adjustable connection therebetween, a pawl mounted on said plate, a ratchet wheel secured to said shaft exteriorly of said casing, each graduation of said ratchet wheel subtending an angle corresponding to that subtended by each of said arcuate slots, a spring mounted on said plate supporting said pawl and urging it into contact with said ratchet wheel, said pawl and said spring being protected by said rim of said plate, whereby oscillation of said needle bar produces pivoting of said actuating lever about said shaft, carrying said plate therewith and causing said pawl to turn said ratchet wheel and said shaft, thereby carrying said cam and reciprocating said rocker arm, said oscillation and reciprocation being capable of synchronization through adjustment of said bolts in said arcuate slots to thereby change the angular disposition of said actuating lever relative to said plate, without altering the relative disposition of said pawl relative to said ratchet wheel.

References Cited in the file of this patent FOREIGN PATENTS 632,399 Germany July 7, 1936

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