CS277654B6 - Sewing machine device for moving the end of the upper thread after it has been cut - Google Patents

Abstract

The sewing machine apparatus used to move the end of the upper thread after it has been cut above the abutment surface of the presser foot (7) comprises an ejector hook (9) mounted directly on the feed shoe (7) which pivots in the movement direction of the presser foot (7). The ejector hook (9) is formed by a two-armed lever, the lower arm of which is ended by a rectangular bend (10) and the upper arm (11) is freely assigned to a control arm (22).

Description

Field of technology

The invention relates to a device for a sewing machine for moving the end of an upper thread after it has been cut above the abutment part of the sewing foot, comprising an ejection hook.

Prior art

The end of the upper thread, which is stretched to the underside of the sewn work immediately after the thread has been cut, is pulled upwards below its abutment part during the subsequent removal of the sewn work from under the raised presser foot. After inserting the new sewn work under the presser foot and after lowering it, it remains clamped between the upper side of the sewn work and the abutment portion of the presser foot, so that it cannot be extended to the underside of the sewn work by moving the sewing machine needle down. At the beginning of the next seam, therefore, an aesthetically detrimental undesirable piece of unstitched upper thread remains on the face side of the work, which must be additionally cut by hand.

Various devices are known for displacing the end of the upper thread of a sewing machine after it has been cut above the abutment part of the presser foot. One of them uses an electromagnet to derive the displacement movement, which serves to switch off the upper thread tensioner during cutting and which is provided in its extension with a screw device, the lifting movement of which turns off the upper thread tensioner, and the ejector hook for moving the upper thread end. Although this device is relatively simple, it places obvious demands on the accuracy of the production of the screw device and also the use of an electromagnet is a possible source of malfunctions.

Another known device is controlled automatically via lever gears, the impulse to actuate it being derived from the movement of the needle bar by a system of levers and return springs, which makes the whole device structurally complex, the construction of the device making it difficult for the seam to manually lift the presser foot.

In another known device, the whole mechanism of the ejection _t hook pivotally mounted on the control device, which is arranged on the thrust rod, whose reciprocating motion is controlled. This whole device is therefore forced to share all the movements of the pressure bar and thus increases its weight and inertial forces, which is undesirable, as this reduces the ability of the pressure bar to copy the vertical component of the feeder movement during sewing. This increases the amount of spontaneous stitch extension in a known manner, which varies with the sewing speed and therefore cannot be corrected by the corresponding stitch length setting.

In another known device, the ejector hook is connected to a pivot pin movably coupled to the pressure bar of the sewing machine and inserted into a sleeve which is attached to a fixed part of the arm of the sewing machine in a manner eliminating adjustability of the sleeve. This limits the usability of the device, since machines of different types, for example with needle feed or with zigzag stitch, also have different paths of movement of the needle, which the ejector hook must safely avoid.

The essence of the invention

The above-mentioned drawbacks are eliminated by a device for moving the end of the upper thread after cutting it to the abutment part of the sewing foot, comprising an ejector hook, the essence of which consists in the ejector hook being pivotable in the direction of movement of the sewing foot on the sewing foot. the arm engages the control lever of the control device.

Overview of pictures in the drawing

The invention is further elucidated by means of the drawing, which shows a view of a device for moving the end of an upper thread after it has been cut.

Example of an embodiment of the invention

The device is described on the example of a sewing machine with an upper foot feed, which comprises a feed bar 1, which is slidably mounted in a feed body 2, in which a needle bar 2 is also slidably mounted, terminated by a holder 4 for fixing a sewing needle. 5. A feed foot 7 is fastened to the feed bar 1 by a screw E. A ejection hook 9 in the form of a two-arm lever is rotatably fixed to the front feed foot 7 by a pin screw 8 oriented transverse to the sewing direction. The lower arm of this ejection hook 9 is terminated by a rectangular deflection 10, the upper arm 11 is then freely assigned to a two-arm control, in this case angled, control. lever 22. ..... .

A guide sleeve 14 is firmly mounted in the arm 15 of the sewing machine, in which a pressure rod 13 is slidably mounted, to which a presser foot 17 is attached by a screw 16. At the same time, an attachment 18 is fastened by this screw 16 provided with a hole 20. one end of the tension spring 19 is suspended, the other end of which is suspended in an opening 12 formed in the lower arm of the ejection hook 9.

The control lever 2e mounted on the sewing arm 15 by a pin screw 21 engages with its lower arm 23 with the upper arm 11 of the ejection hook 9. The second, upper arm 24 of the control lever 22 is provided with an opening 25 for holding a rod 24 of a control device (not shown). or a pneumatic cylinder.

The described device works as follows. When the sewing of the selected section is completed, the sewing needle 5 stops in the upper position and both threads are cut. In order to move the end of the upper thread above the abutment part of the feed foot 7, a rod 26 is actuated, which is moved upwards by the action of an impulse-controlled control device for cutting the thread. By moving the rod 26 upwards, the lower arm 23 of the control lever 22 compresses the associated upper arm 11 of the ejection hook 9, which swings in the direction of movement of the feed foot 7, i.e. counterclockwise. The rectangular deflection 10 of the lower arm of the ejection hook 9, when swinging, catches the upper cut thread and pulls it over the abutment part of the feed foot 7 independently of the length of the stitch created by the foot and needle feed of the sewn work. After the control device e.g.

electromagnetic interrupts the action on the rod 26, the ejector hook 9 returns and the associated control lever 22 by the action of the tension of the spring 19 returns to the initial position. The device is thus ready to perform the next work cycle.

The advantage of the device is that the initial position of the ejection hook 9 relative to the foot feeder 2 does not change even when sewing layers of sewn work of different thicknesses. The ejector hook thus formed can also be used on the sewing foot of a bottom feed sewing machine.

Claims (1)

PATENT CLAIMS A sewing machine device for moving the end of the upper thread after cutting it above the abutment part of the feed foot, comprising an ejection hook, characterized in that the ejection hook (9) is pivotably mounted in the direction of travel of the feed foot (7) on the feed foot (7) and is formed by a two-arm lever, one arm (11) of which engages with the control lever (22) of the control device.