Patent GB-739733-A (GB)
Title: Sewing machine
IPC: D05B85/06
Filed: 1953-06-12
Abstract: 739,733. Sewing-machines. LEWIS INVISIBLE STITCH MACHINE CO. June 12, 1953 [July 25, 1952], No. 16312/53. Class 112. Buttonhole and like machines; blind-stitching machines; needles, vibrating laterally. A blind-stitching machine with a pivotally-mounted oscillating needle-bar has a rotary chain-stitch looper and an oscillating take-up. The machine described is arranged for the automatic production of groups of stitches at the same place, e.g. for tacking labels to clothing, and the needle is vibrated laterally between stitches; provision is made for varying the number of stitches in a group. In the embodiment shown, the frame comprises a standard 4 with an upper arm 5, containing the main shaft 11 and carrying the stitch-forming devices and a fixed presser-foot 7,. and a lower part 2 with a free work-arm 3 carrying a fixed work-plate 44 and a movable work-support 45 and work-bender 47. The needle-bar 9, Figs. 2A and 3, carrying the curved needle 8 is freely mounted on a fixed spindle 14, and is oscillated by a link 16 from a crank 18 on a transverse shaft 19 geared to the shaft 11. The rotary looper 10 fixed in the end of a nearly vertical shaft 38, is driven through idle gears from a shaft 30 geared to the wheel 21 driving the shaft 19; the looper has a central aperture to receive the needle. The shaft 30 also has a worm gear 29 driving a horizontal shaft with a cam 26 actuating a bell-crank 22 whereby the needle-bar is reciprocated along the spindle 14 to vibrate the needle laterally. The thread passes through guides 107, 108 to a thread nipper 117, which is closed during take-up and is opened just before the stitch is set by a spring-biased lever 118 actuated by a roller 122 on the needle-driving crank 18, and a tension device 123, and thence through a pull-off 124, 125, a take-up arm actuated by a cam 114 on the shaft 19, a guide on the end cover, and a guide 129 on the needle-bar to the needle. The worksupport 45 passes through an aperture in the work-plate 44 and is supported by a spring 55, Fig. 6A, surrounding the stem 46 of the workbender 47, bearing on a sleeve 52 frictionally slidable in the end of the arm 3; the work-bender is shown retracted. The stem 46 rests on a spring 53 in the sleeve 52 and has an extension passing through an arm 50 of a bracket 51 and carrying nuts 51a: the members 45, 47 can thus both be lowered by downward movement of the bracket 41 and can be depressed independently against the respective springs. The bracket 51 is connected by a link 56 to the upper end of a member 65 which is adjustable vertically on a shaft 58 by a screw 66 and spring 67 to vary the upper positions of the work-engaging members 45, 47: the link 56 and member 65 form a toggle in their normal position to take pressure on the members 45, 47. The shaft 58 is moved angularly to lower these members for insertion or removal of the work, by connection to a shaft 70, Fig. 12, having a pedal-operated arm; movement of this shaft also locks the shaft 11, as described below. Starting and stopping. The shaft 11 is driven by a motor through a belt and stop-gear which provides a positive stop, controlled by another pedal-operated arm actuating a shaft 80. This shaft carries freely an arm 93, Fig. 12, carrying a roller 92 arranged to enter recesses 91 in any of a set of cams 84 driven through gearing from the shaft 11 at one twenty-fourth of the speed of that shaft: one of the cams has two recesses, one three, and one four, providing for cycles of 12, 8 and 6 stitches respectively, the cycle required being selected by rocking and sliding the arm on the shaft 80 by means of a finger-knob 101, which actuates a spring detent engaging recesses in the shaft, to bring the follower 92 opposite the appropriate cam. The follower is withdrawn from the cam when the stop-gear is released to start the machine, and the stop-gear is actuated by a spring to stop the machine when the follower enters the next recess 91. The shaft 80 is extended to the head of the machine to actuate a thread pull-off. The machine is prevented from running when the work-engaging members 45, 47 are retracted, by a pin 170 on a member 165 engaging a notch in a cam on the shaft 11; the member 165 is drawn downwards by an arm on the shaft 70 whereby the members 45, 47 are lowered. One edge of the cam notch is chamfered to permit starting when the members 45, 47 are nearly in position, this edge then acting as a cam to complete their movement. Threads, controlling otherwise than in stitch-forming; thread-cutters and thread-end holders. Thread is pulled off when the machine stops by a finger 123, Fig. 3, on a lever 126, engaging it between two fixed guides 124; the pull-off stroke is varied by a stop adjusted by a screw 138. The lever 126 is free on a spindle 130 and is urged downwards by a spring 133; it is lifted when the machine is started by an arm 131 fixed on the spindle 130, which is connected through a motion-amplifying linkage with the shaft 80 controlling the stop-gear, the lever being held raised by a spring detent. As the follower 92 enters a cam recess 91 to bring the stop-gear into action the arm 131 is moved to free the detent to allow the lever 126 to be actuated by the spring 133; the thread-nipper 117 is open at that time, but is closed when the machine actually stops. When the shaft 70 is actuated to lower the workengaging members 45, 47, the thread is cut and its end is moved clear of a new work-piece. The cutter comprises a flexible blade 50, Fig. 5, adjustably fixed to the presser-foot 7 so as to extend partly across the work-receiving opening 151, and against which the thread is drawn by a finger 152 on a member 153; this member is guided by pins and slots 156 so that the finger moves in an angular path, and is actuated by a lever 161 pivoted to the foot 7 at 162. A campiece 172, Fig. 12, on the member 165 actuated by the shaft 70 engages a follower 174 on a tubular shaft 144 to actuate the lever 161 by means of a depending arm at the head end of the latter shaft ball-jointed to the lever at 164: the shaft 144 is returned by a spring 176, Fig. 2A. The thread end is moved aside by a wiper arm 183, Fig. 3, moving in an opening 185, Fig. 5, in the presser-foot 7 and secured to a shaft 145 (not shown), arranged within the shaft 144; the member 165, Fig. 12, actuates the shaft 145 by a link 179 having a lost-motion connection with an arm on the shaft, which is restored by a spring 186, Fig. 3.