GB421452A - Sewing machine - Google Patents

Abstract

421,452. Sewing-machines. SINGER MANUFACTURING CO., Elizabeth, New Jersey, U.S.A. July 20, 1934, No. 21252. Convention date, Oct. 5, 1933. [Class 112] A chain-stitch sewing-machine has an improved looper mechanism with rapid loopseizing and loop-shedding movements with a dwell at the end of the loop-seizing stroke. The invention is illustrated as applied to a feed-off-the-arm machine. The rocking and sliding looper shaft 30 is journalled in lugs 28, 29 in the work supporting arm 15. The threaded loopers 31 co-operate with needles 5 to form the usual two-thread or double chain stitches. The shaft 30 is given its rocking movement to move the loopers endwise into and out of their respective needle loops by an eccentric 32 on the lower rotary shaft 16. The eccentric is embraced by a pitman 34 having a slot 35 embracing the guide block 36 pivoted on the stud 37 projecting into the arm 15. The pitman 34 is connected by the link 38 to a lever 39 pivoted on the pin 40 carried by the arm 15. The lever 39 is connected by a ball and socket and a link 41 to a crank arm 42 fixed to the looper shaft 30, to rock it. Sliding movements are imparted to the looper shaft 30 to give the loopers their needle-avoiding movements by an eccentric 43 on the lower shaft 16. This eccentric is embraced by a block 44 in a fork 45 fixed to slide shaft 46 journalled in a bearing block 47 in the arm 15. The slide shaft 46 has a forked lateral arm 48 embracing the shaft 30. The compounding of the rocking and sliding movements of the shaft 30 causes the loopers to describe an elliptical path, Fig. 14. The free end o of the pitman 34 is caused by the guide 36 to move in the eggshaped path 50, Fig. 15. In the upper extreme position of the lever 39 the egg shaped path 50 of the free end o of the pitman 34 is curved reversely to the arcuate path 51 of the lower end of the link 38 about its pivotal connection with the lever 39. This causes a relatively rapid reversal of motion of the lever 39 and connected looper at the end of the loop-shedding stroke. In the lower extreme position of the lever 39, the egg-shaped path 50 is curved in the same direction and coincides over a considerable portion of its length with the arcuate path 51 of the lower end of the link 38. This condition causes the looper 31 to move slowly or dwell in its reversal of motion at the end of its loop-seizing stroke. The looper-thread controller comprises the rotary thread cam mounted on the shaft 16. The usual cast-off blade co-operates with the cam. The looper-thread tension device consists of two discs 69, Fig. 5, loose on a stem 70<1> and acted on by the head 70 and spring 74, the tension of which is adjusted by the nut 76.