Patent GB-617036-A (GB)
Title: Thread-controller for sewing machines
IPC: D05B63/00
Filed: 1946-09-26
Abstract: 617,036. Sewing-machines. SINGER MANUFACTURING CO. Sept. 26, 1946, No. 28767, Convention date, May 18. [Class 112] Stitch-forming devices.-The invention relates primarily to improved means for controlling the looper thread in. a two-thread buttonhole sewing machine, to enable more accurate placing of the purl and the use of less thread tension than usual, thus giving a better finish and allowing of the use of lower quality needle thread and heavier looper thread. Improved means for' controlling the needle thread are also des- .cribed. In the arrangement described, in a buttonhole sewing-machine with a vibrating needle, the lower thread-handling devices comprise a thread-carrying looper 68, Fig. 10, and an opposed threadless looper 69 (not shown), moving in the plane of the needle vibration, two forked loop-detainers 90, 95 moving perpendicularly to that plane, and a thread-controller 149, all these members, together with the needle-throat member 112, being carried by a turret 61 which is rotatable by a sector gear 116, Fig. 1, in unison with a sector 117 which rotates the needle-bar ; no check-springs are used in controlling the thread. The complete stitch-forming cycle comprises : penetration by the needle 50, passing through the buttonhole slit, of the previous needle loop held by the detainer 90 ; release of the latter loop by the detainer and penetration of the new needle-loop by the threaded looper 68 ; withdrawal of the needle and engagement of the looper-thread by the detainer 95 ; release of the needle-loop by the looper 68 and penetration by the needle, passing through the material, of the looper-thread loop ; release of the latter loop by the detainer and engagement of the new needle-loop by the threadless looper ; and transfer of the latter loop to the loop detainer 90. The operations and thread-control are described in detail. Actuating loopers and loop-detainers.-The two loopers are carried by a single member 67 mounted on a pivot-pin 66, on a post on the turret 61, and connected by a link to a lug at the top of a tubular member 77, Fig. 1, sliding in the hub of the turret. The lower end of this member is connected to a pitman 81 which is reciprocated, to actuate the loopers, by a crank on a shaft driven intermittently through gearing by a wheel 89 on the main shaft 37 of the machine, the mechanism being such that each looper advances from and returns to a midposition, dwells there, retires further and returns while the other looper advances and returns, and then dwells again. The loop-detainers 90, 95 are carried on members 91, 96 respectively pivoted at 92, on posts 93 on the turret, and connected by links 98, 99 to a crosshead 100 on the upper end of a tubular member 101 sliding within the looper-operating member. The member 101 is engaged at its lower end by an arm 106, Fig. 1, on a verticallysliding member 107 provided with a stud which engages a cam-slot in the rear face of the wheel 89. Controlling looper thread.-The looper thread is led from a supply through a tubular guide 134, Fig. 1, an eye 135 in a pull-off arm 136, a fixed eye behind the pull-off arm, and another eye above a tension device 146, round the tension device and up the bore of the tubular member 101 ; the pull-off arm 136, pivoted at 137, has two arms engaged by pins on a wheel 142 on a shaft geared to the feed-wheel shaft. The thread passes from the top of the tube 101, of which the reciprocation produces some thread - control effects, to the looper 68 by way of an eye 152 in a thread-control member 149 fixed on an extension 147 of the pin which connects the link 99 to the crosshead 100, this pin being rigid with the crosshead. Controlling needle thread.-The needle thread is led, from a supply, round a tension device 126, Fig. 1, through a pair of eyes in a plate 129, through an eye in a take-up arm 122 and a thread-nipper 132 and then down the bore of the hollow needle-bar 46 ; the take-up arm is pivoted at one end and actuated by a stud engaging a cam-groove in a disc 119 on a vertical shaft geared to the needle-bar shaft to run at half the speed of the latter, the cam-groove being formed so as to fulfil, in conjunction with the action of the needle-bar, all the necessary thread control requirements, which are indicated in detail. Needles, vibrating laterally.-The needle 50 is carried by a block 49 slidable on a cross-pin in a yoke on the lower end of the needle-bar, the yoke being guided by members 51 depending from the needle-bar turret which is rotatable by a sector gear 117. A ring 54 is reciprocated vertically by a rod 55 actuated from a vertical shaft 40 by a pitman 59 and adjustable crank 57, the movement of the ring being translated by suitable mechanism into reciprocation of the block 49 along the cross-pin carrying-it.