GB452963A - Improvements in sewing machines - Google Patents

Abstract

452,963. Sewing-machines. FAIRWEATHER, W. C., 65, Chancery Lane, London.- (Singer Manufacturing Co.; Elizabeth, New Jersey, U.S.A.) Jan. 27, 1936, No. 2449. [Class 112] A sewing-machine, particularly of the single thread straw-braidsewing type having a wide variation of stitch length has a series of cams on the main shaft which are selectively rendered operative by the feed regulator to hold open the thread tension device for a period appropriate to each stitch length. The main shaft 5 has an eccentric working in a block 18 engaged by the forked end of a pitman 16 connected to an arm 8 for effecting the longitudinal movement of a fourmotion feed dog 4. A link 21, pivoted at one end 20 to the pitman and at the other end 22 to a lever 23 pivoted to the machine frame at 24, controls the length of the stitch, the forward end of the lever 23 having a slidable handle 26 with a detent 28 engaging a fixed rack 30. The thread-tension device comprises a block 31, adjustably fixed in the frame by a set-screw 33, and having a flat face co-operating with a flange 38 on a collar sliding on a spindle 35 under control of an adjustable spring 39. The spindle 35 has a yoke 44, carrying a roller 43, and is urged to the right by a strong spring 46. The roller 43 bears against a series of cam followers 48 pivoted on a lever 51 which is connected to the lever 23 by a pin 55 and slot 54. The followers 48 have cam engaging surfaces 49 at progressively increasing heights which are selectively engaged by four different cams 47<1> on the shaft 5 as the lever 23 is moved. When the lever 23 is set for the shortest stitch length, the roller 43 is directly engaged by a larger central cam 47 which opens the thread tension device for the minimum time, the other four cams keeping the tension device open for progressively longer periods. An adjustable collar 37 is provided on the spindle 39 and by varying the position of this collar and the position of the block 38 it is possible to vary the thread tension at each stitch from light to zero or from strong tension, due to the spring 46 acting through the collar 37, to light tension due to the spring 39 which acts directly on the flange 38. A shoulder on the spindle 39 pushes the flange 38 away from the face of the block 31 when the device is set to release the tension completely at each stitch.