GB736548A - Improvements in or relating to electrical drives for sewing machines - Google Patents

Abstract

736,548. Gearing for stopping machinery. SCHWAB, M. April 15, 1953 [April 17, 1952 April 22, 1952], No. 10294/53. Class 80 (2). [Also in Groups VII and XXXIV] In a drive for a sewing-machine a movable element of a friction clutch is adapted to be coupled in one end position directly to the driving motor, and in the other end position to a brake disc driven at slow speed via a magnetic clutch, whereby the machine may be stopped in any desired position, when said element and disc are coupled together, by interruption of the electric supply to the magnetic clutch, The shaft 2 of an electric motor carries at one end the driving element 4 of a friction clutch and at the other end the driving element 37 of a magnetic clutch. A shaft 9, which is slidably mounted, carries at one end a clutch element 8 provided with a friction lining 7 and at the other end a grooved pulley 18 in driving connection with the sewing-machine. A disc 17, provided with a friction lining 23, is also carried by shaft 9. Depression of a lever 55 by means of a treadle serves to shift shaft 9 against the bias of a spring 61 for engaging lining 7 with element 4 to drive the sewing-machine, and also for simultaneously disengaging lining 23 from a brake disc 22 rotatably mounted in a fixed frame 16. A shaft 43 is then driven from the main drive of the sewing-machine via a chain (not shown) and a sprocket 44, when slip-rings on shaft 43 serve to convey electrical current to the element 37, whereby an element 36 of the magnetic clutch is coupled, via sprockets 33, 35 and chain 34, shaft 29, sprocket 28, chain 27 and sprocket-ring 26, to disc 22 for driving the latter at slow speed. On release of lever 55, spring 61 'returns shaft 9 to disengage elements 4 and 8, and to engage discs 17 and 22, whereby pulley 18 is driven at slow speed. A throw-over switch is then selectively operated to include either one of a pair of said slip-rings in the electrical circuit of the magnetic clutch, the periphery of each of said pair being formed with a gap so positioned that the magnetic clutch circuit is interrupted, to stop the machine, when the needle bar is located at either top or bottom position. In a modification friction linings 8 and 23 are both carried by the same element of the friction clutch, and the brake disc is driven by a pinion engaging an internal gear ring provided on said disc. In a further modification the magnetic clutch, and the drive from the latter to the brake disc, are enclosed within the casing of the electric motor.