Patent GB-730436-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B19/00
Filed: 1953-05-21
Abstract: 730,436. Sewing-machines. HARRIS, C. May 21, 1953 [June 6, 1952; Dec. 23, 1952]. No. 14367/53. Class 112. A sewing-machine of the zig-zag type is provided with a rotary cam for controlling the transverse movement of the needle, and with a double worm reduction gear, interposed between the cam and needle-reciprocating shaft, for driving the cam. In the embodiments described, the reduction gear, with the exception of the first worm of the train, is mounted upon an auxiliary frame attached to the main frame of the machine; and the cam is arranged either to vary indirectly the transverse movement of the needle, or to effect said transverse movement. In Figs 2 and 3 a needle bar 6, carrying the needle 7, is reciprocated by means of a rotary shaft 5, and is slidably mounted in a frame 8 which is pivoted at 9 to the machine head and is oscillated by means of a variable pitch eccentric 13. The latter is carried on a transverse shaft 15 driven from shaft 5 by a worm 21 and worm gear 20. The pitch of the eccentric is varied by means of a spindle 23 slidably mounted in the shaft 15 and biased outwardly by a spring 25, the inner end of the spindle bearing against an eccentric-adjusting pin 18 and the outer end bearing against a cam 29 rotatable with a shaft 30. The latter is driven from shaft 5 by double worm reduction gearing comprising a worm 35 carried on shaft 5 and meshing with a gear 36 on a vertical shaft 37, and a worm 42 on the latter which meshes with a worm gear 43 on shaft 30. Several alternative cams may be slidably mounted on shaft 30, spindle 23 being retained in position when the cams are changed, by means of a spring-biased arm 45 which bears upon a flange 46 on spindle 23. In a modification, Fig. 8, an extension 51 of shaft 30 is journalled in a sleeve 52 which in turn is journalled in a bearing 53 carried by the machine frame. Worm gear 43 and a collar 58 secured to the sleeve on opposite sides of bearing 53 serve, by engagement with the latter, to limit longitudinal movement of the sleeve. A knurled nut 61, mounted on the screwed end 60 of the extension 52, when tightened serves to press a collar 63 on the sleeve against the shouldered end of shaft 30 for coupling the latter to the worm drive. In a further modification, Figs. 13, 14, a pitman 104 connects the pivoted frame 8 to a curved arm 107 of a lever 108, the connection to the arm being an adjustable one. The lever is pivoted at 109 to the machine frame, and comprises a second arm 112 carrying a roller 113 which bears against a cam 114, rotation of the latter thereby serving to rock the frame 8. The cam is carried by a spindle 115 journalled in a transverse, tubular shaft 100 (not shown). Spindle 115 is geared by bevel pinions 115a, 124c to a shaft 124a, and the latter is driven from shaft 5 via a train of double worm gearing 117, 118, 123, 124. A pointer 140 is fixed to spindle 115. Alternative cams 126 are mounted on a fixed spindle 127. Pitman 104 may be disconnected from frame 8, and the latter may then be connected by a two-part pitman 93, 94 to a yoke 98 adapted to be rocked on a link 98a by means of a cam 99 mounted on the shaft 100, the latter being driven from shaft 5 by gears 101, 102. Cam 29 is normally arranged to rotate once for every 450 reciprocations of the needle, but the ratio may vary between 250 to 750 reciprocations. The speed ratio of shafts 5 and 115 may range from 1:175 to 1:750. Governing threads. The machine may comprise a thread guide, Fig. 11, having a pair of smoothfaced, thread-clamping members, 79, 80 pressed together by a spring 85. The needle bar on approaching its topmost position displaces a striker pin 76 adapted to release the spring pressure on the top member 79.