GB867805A - Improvements in or relating to stitch adjusting mechanisms in sewing machines - Google Patents

Abstract

867,805. Sewing machines. PFAFF A. G., G. M. Oct. 8, 1957 [Oct. 9, 1956], No. 31379/57. Addition to 812,298. Class 112 The arrangement for manual control of the work feed so described in the parent Specification is modified to provide for alternative automatic control of the work feed. In the original arrangement a feed-adjusting slide 17, pivoted on a fixed pin 18, is connected by a link 23 to one end of a lever 44 pivoted on a fixed pin 42. A stud 46 carried by lever 44 is disposed within an aperture 36 formed in a rotatable disc 35. Slide 17 is spring-biased to raise stud 46 into engagement with the outer edge of the aperture governing the length of forward stitch, adjustment of the latter being effected by rotating disc 36. A shaft 59, coaxial with disc 35, carries a three armed lever one arm 63 of which is connected by a spring 61 to pin 42 for biasing another arm 65 against pin 42. When shaft 59 is rotated clockwise against the bias of spring 61 the third arm 55 engages a stud 54 on lever 44 to shift stud 46 into engagement with the inner edge of aperture 36 governing the length of the reverse stitch. This arrangement is modified by extending aperture 36 to form a second portion 36<SP>1</SP> beyond the position of zero feed, and the arrangement is incorporated in a zig-zag sewing machine having nest of rotary cams comprising cams 89 governing the stitch width and a cam 88 governing the stitch length. Cam 88 co-operates with a follower 87 on an arm of a bell crank lever 86, the other arm of which is coupled by a link 82 to one arm of a bell crank lever 77. A bar 69, pivoted to the other arm of lever 77 and biased anti-clockwise by a spring 76, carries a stud 72 which normally engages the outer edge of a substantially vertical slot 75 in a lever 74 which is coupled to lever 44 and pivots with the latter about pin 42. When disc 35 is rotated anti-clockwise to position stud 46 within the aperture 36<SP>1</SP>, stud 68 on disc 35 enters a slot 70 formed in the end of bar 69 to pivot the latter clockwise. Stud 72 is thereby shifted into a slot 73 formed substantially horizontally in lever 74, whereby bar 69 is coupled to link 23 for effecting automatic control of the feed. The magnitude of the variation of the latter increases as disc 35 is progressively rotated to shaft stud 72 nearer to pin 42.