Patent GB-590104-A (GB)
Title: Improvements in buttonhole sewing machines
IPC: D05B3/06
Filed: 1945-04-12
Abstract: 590,104. Sewing-machines. SINGER MANUFACTURING CO. April 12, 1945, No. 9119. Convention date, July 15, 1944. [Class 112] [Also in Group XXIV] In a machine for sewing straight buttonholes means are provided for automatically and simultaneously stopping the feed, centring the work, and increasing the amplitude of needle vibration at the ends of the hole to produce barring stitches, and to resume normal side stitching after a predetermined number of barring stitches. The tension of the needle thread is reduced during barring. Feed. The movements of the work-clamp 15, Fig. 4 (underneath plan) are derived from a cam 17 which is rotated step-by-step by a ratchet clutch 33, 36, Figs. 4 and 10, (see Group XXIV) actuated from an oscillating vertical shaft 46 through a link 44 of adjustable length adjustably connected to an arm 42 secured to the inner clutch member 36; the adjustment of the link along the arm 42 is carried out by means of a screw 56 as described in Specification 562,717. The longitudinal movement of the work-clamp 15 is derived from a heart-shaped slot in the feed-cam 17 by means of a link 21 adjustably connected to a crank 20 which has a roller engaging the cam-slot, the link carrying a pointer moving over a scale to indicate the length of buttonhole corresponding to the position of adjustment; the lateral shifts of the work-clamp before and after barring are produced by another cam-slot engaged by a lever 25. The feed-cam 17 is secured to a vertical timing-shaft 18 by a hole engaged by a pin on a collar on the shaft, so that the cam and clutch may be withdrawn without affecting the shaft. The clutch 33, 36 is disengaged by a member 66, with a conical surface engaging the ratchet arms, sliding on the shaft 18 and fixed to a bar 64 sliding in a keyway in the shaft, the other end of the bar being fixed to a collar 73 engaged by levers 77 and 146 pivoted on a spindle 78. Needles vibrating laterally. The needle-bar is carried in a gate oscillated about a vertical axis by a link 97, Fig. 15, adjustable in length and adjustably connected to a lever 98 which is in turn oscillated by a link 100 from a lever 101 engaging a cam 105 on a shaft driven at half the speed of the main shaft. The link 100 is connected to the lever 101 for side-stitching by a notch 106 in the link engaging a pin 107 on the lever and for barring by a pin 109 on the link engaging the narrow part of a key-hole slot 110 in the lever, the link being biassed to the side-stitching position by a spring 108. Control. A rocker 80 mounted on the spindle 78 has a tail engaging a cam 83 on the shaft 18 under the influence of a spring 86; the cam has two similar halves, each giving a gradual rise and a sudden drop, and the high end of each half is adjustable (see Group XXIV) so that the drop can be accurately timed. As stitching proceeds along one side of the buttonhole the rocker 80 is gradually moved by the cam 83 until a shoulder 90 on a pawl-lever 89 pivoted on the rocker engages over the lever 77; after a little further movement, the cam 83 allows the rocker 80 to swing back sharply, so that the lever 89 strikes the lever 77 to raise the collar 73 and thus disengage the clutch driving the feed-cam The return of the rocker 80 simultaneously shifts the needle-vibrating link 100 to the barring position by means of a catch 111 pivoted-on the rocker and engaging a projection 117 on the link, the movement being limited by a stop 92 adjustably carried by the rocker to determine the length of the barring stitches. This movement of the link 100 allows a pawl 132 carried by a lateral extension of the lever 101 to spring into engagement with a ratchet sector 121 mounted on the same axis as the lever and thus to rotate the sector step-by-step until an adjustable stop 136 thereon engages a pin on a lever 138 to move the latter anti-clockwise, thus moving the catch 111 by means of a pin 140 to let the link 100 spring back to side-stitching position and moving the pawl-lever 89 to free the lever 77; the return movement of the link 100 simultaneously engages the clutch to recommence feed by an adjustable stop on its tail 144 engaging the lever 146. The initial position of the ratchet sector 121, which determines the number of barring stiches, is controlled by a stop-pin 125, adjustable along a scale, the sector being biassed against the stop by a spring; the part 129 engaging the pin 125 is adjustable relative to the toothed part 121 so that different teeth may be brought into play from time to time. Controlling needle thread. When the link 100 is moved to the barring position a cam 120 thereon raises a plunger to release the tension device 118.