GB998397A - Improvements in or relating to chain-stitch sewing machines - Google Patents

Abstract

998, 397. Sewing machines. G. M. PFAFF A.G. Oct. 18, 1963 [Oct. 24, 1962], No. 41160/63. Heading D1G. [Also in Division F2] In a chain stitch sewing-machine comprising an eccentric adjustably mounted on a drive shaft and connected by linkage means to the feeding means for varying the feed stroke in dependence upon the adjustment of the eccentric, the operating mechanism for a thread-carrying looper comprises an input member revolubly displaceably about the fined axis of a control shaft to displace the looper in the feed direction, output member supporting the looper and rotatably mounted upon the input member upon an axis parallel to the feed direction, first and second eccentric drive means connected between the output member and said drive draft to impart substantially constant oscillatory movements to the output member, and means operably connecting said control shaft with said linkage means. An under-shaft 6, directly coupled to the main arm shaft, carries an adjustable eccentric 17 coupled by a linkage 29 to shafts 9 and 31. Eccentric 17 is adjusted by depressing a spring-biased pin 25 to engage a notch 22 in a ring 21, and then turning the main arm shaft. Shaft 9 is coupled both to the feed dog and also to an arm shaft effecting feed oscillation of the needle. Shaft 31 carries a crank 30 formed with a pin 32 parallel to shaft 31. A member 33, journalled on pin 32, has an arm 34 coupled to the pitman 35 of an eccentric 18 on shaft 6. Member 33 also carries a pin 36 which is disposed at right angles to shaft 31 and journals a bell crank lever, one arm 37 of the latter carrying a looper 40, and the other arm 42 being connected by a universal link 44 to the pitman 43 of an eccentric 28 on a shaft 27 driven by gearing 16, 26 from shaft 6. The thread eye 41 of looper 40 thereby moves in a path 39 having a constant loop-taking component imparted thereto by eccentric 28 in a direction transverse to the line of feed, and a needle-avoiding component which is parallel to the live of feed and which has a constant component imparted thereto by eccentric 18, and a variable component imparted thereto by eccentric 17 and thereby proportional to the rate of work feed. It is stated that the arrangement can be used either in two-thread chain stitch machines, or in twoneedle machines producing covering stitches of the federal 402 type. Alternatively, arm 37 may carry a plurality of loopers each co-operating with a separate needle. Reference has been directed by the Comptroller to Specification 869,637.