GB837896A - Improvements in or relating to sewing machines - Google Patents

Abstract

837,896. Change-speed gear. PFAFF A.G., G. M. Dec. 18, 1956 [April 24, 1956], No. 38504/56. Class 80 (2). [Also in Group VII] A two-speed drive from a pulley 3 of an electric motor 4 to the shaft 10 of a sewing machine, comprises a first belt 2 directly connecting the motor pulley with a groove 9 in the usual hand wheel 1, and a second belt 32 running in grooves 20 in a screwed clutch member 13 and 28 in a stepped pulley carried on an adjustable countershaft 24 and having a larger groove 26 engaging the first belt 2. Low ratio, for embroidering, is obtained when the hand wheel 1 is first released from the machine shaft 10 by unscrewing the screwed clutch member 13 from a thread 15 in a sleeve 11, pinned to the shaft 10, to release clutch pressure on a disc 17. The stepped countershaft pulley 26 is then adjusted by sliding a slotted support arm 22 over a clamp-screw 8 to tighten both belts, whereupon drive from the motor pulley 3 passes through the belt 2 to the now freely rotatable hand wheel 1 and countershaft pulley 26, and from the latter through the belt 32 to the screwed clutch member 13 and thence to the shaft 10 through positive connections 16, 18, 19 on the disc 17, clutch member 13 and sleeve 11. The connection 18, 19 permits sufficient lost-motion for screwing the clutch member 13, which in this disengaged position is locked by a central screw 21. For high-speed the countershaft pulley 26 is withdrawn from the belts and the clutch member 13 is screwed into the sleeve 11 to clutch the hand wheel 1 frictionally to the sleeve 11 through the disc 17, the machine then being driven direct through the belt 2 and hand wheel 1. A jockey pulley 7, bearing on the belt 2 only, is carried on a slotted adjustable arm 6 either integral with or separate from 22 and clamped by the same screw 8.