GB512235A - Intermittent tension devices - Google Patents

Abstract

512,235. Sewing-machines. FAIRWEATHER, W. C. (Singer Manufacturing Co.). April 13, 1939, No. 11169. [Class 112] A tension device having an operative and a retracted position is provided with a guard to prevent threading of the device when in the retracted position; a spring latch is provided to lock the device in one of its positions. The invention is intended to be applied to machines having a number of different devices for various types of sewing, and is described as applied to an intermittent tension device for use when thread-marking on a machine which has other tension devices for other operations. The tension device comprises the usual shouldered and slotted stem 11, tension discs 12, tensioning spring 18 and adjusting nut 19, and in the device shown the spring 18 bears on a pressure disc 17 having a central bar, working in the slot of the stem 11, on which the axial tension-release pin 20 acts. The stem 11 is slidable in a housing secured in the wall of the machine arm 1, its movement being limited by a pin 28 engaging a slot in the housing 8, and is normally pressed outwards by a spring 23 to a position in which the pin 20 is clear of the cam 21 on the needle-shaft; in this inoperative position the discs 12 are covered by an annular guard 36 secured to the housing 8, so that the thread cannot be inserted. A spring latch 25, Fig. 7, is secured to the housing 8 by the same screws as the guard 36, and has a fingerpiece 34 and an L-shaped slot 27 which engages the pin 28; the latch tends to spring into a position in which the stem 11 is held in its inward position, in which the pin 20 is engaged by the cam 21 to release the tension during the long feed stroke used in threadmarking.