GB753820A - Improvements in sewing machine mechanisms - Google Patents

Abstract

753,820. Sewing-machines. PFAFF, AKT.- GES., G. M. Oct. 11, 1954 [Nov. 6, 1953], No. 29276/54. Class 112. Needles, shifting laterally.-In a zig-zag sewing-machine with a manual control member for the width of the stitching, means acting on this member for automatically varying the stitch width are provided, comprising a cam actuated by a pawl-and-ratchet wheel; the automatic control means may be built into the machine or added as an attachment, and may be put out of action when desired. The cam may be driven at different speeds and may be readily replaced by a cam giving a different stitching pattern. In the arrangement shown, the automatic mechanism is mounted on a plate 12 closing an inspection aperture in the rear wall of the machine arm, the plate 12 carrying brackets 14, 24 and 57 for the various parts. Slidable in a guide-block 15 passing through the plate 12 is a bar 16 which has at its inner end a roller for engagement with an oscillating member of the needle-shifting mechanism, whereby the bar 16 is reciprocated in time with the needle shifts; the bar is urged inwardly by a spring 19, and can be held in its outermost position to render the mechanism ineffective, by a spring- pressed pin 71 in the block 15 (normally held retracted) engaging a notch in the bar 16. The outer end of the bar 16 extends laterally to engage a forked end of a lever 20 pivoted on the bracket 14, and the other end of this lever carries a pivoted spring-pressed pawl 40 for engagement with a ratchet-wheel 31 on a stud 25 rotatably mounted in the bracket 24. A meshing member 45 formed by a flange on a member 30 free on the stud 25 is adjustable to allow the pawl to engage the ratchet-wheel for one, two, or three tooth pitches in each stroke, and is held in the required position by a hook 47 engaging holes 50 in the bracket 24 ; a pawl 42 pivoted on the bracket 24 prevents reverse motion of the ratchet-wheel 31. Rotating with the ratchet-wheel is a removable cam 34 engaged by a pin carried by one arm of a lever 52, 55 which passes under the arm of the machine and is pivoted on the bracket 57; the front end of the lever is disconnectibly engaged with the manual control member for the stitch width, so that movement of the lever by the cam causes corresponding adjustment of the control member. The parts 52, 55 of the lever have vertical limbs which are slidably connected together and are normally held in operative position by a spring catch; when this catch is released the part 52 can be moved upwards to carry its follower clear of the cam 34 to allow removal of the latter.