GB741776A - Improvements relating to sewing machine drives - Google Patents

Abstract

741,776. Sewing-machines. SCHWAB, M. July 17, 1953 [July 25, 1952], No. 19918/53. Class 112. [Also in Group XXIV] A sewing-machine drive shaft 10 is driven from the shaft 4 of a main motor through a disc clutch 2, 16 and braked by a disc-brake 16, 17 which latter is automatically released when the shaft 10 stops, to permit subsequent slow continuous or stepped rotation to a set position, e.g. with the needle up or down, by an auxiliary drive from either the main or a separate motor H, Fig. 7. To start, the main clutch 2, 16 is engaged and the brake 16, 17 released by turning a lever 15 acting on a flange 12 secured to a bearing-sleeve assembly 11 supporting the shaft 10, which thus moves rightwards. To stop, the lever 15 is released, permitting a spring 18 to declutch and apply the brake. When the machine stops, a centrifugal switch 46, Fig. 7, on a separate shaft 45, driven by the machine, closes a relay 50 energizing a magnet-winding 19, Figs. 1 and 7, which attracts an armature 24, connected by pins 20 to an auxiliary clutch-disc 21, which moves to the right, engaging and taking along a complementary clutch-disc 23, pinned on the shaft 10 which latter is also moved to the right but only to an intermediate position in which both the main clutch 2, 16 and brake 16, 17 are disengaged. Closure of the relay 50 also energizes the auxiliary motor H which, through spur, belt or worm-gear 25, 26 turns a sleeve 27 on which the auxiliary clutch disc 21 is splined, so that the shaft 10 is now driven at reduced speed, which persists until the circuit of the relay 50 is broken, to switch off the auxiliary motor H and re-apply the main brake 16, 17. This occurs when one or other of two insulating strips 48, 49 on a conducting disc 47, carried by the shaft 45, reaches a circuit-completing contact S, the operative strip 48 or 49, which determines respectively needle up or down positions, being selected by shifting the contact S radially, through a Bowden cable B, by a subsidiary pedal E on the main starting pedal F. In Figs. 3 and 4, not shown, the brake is released by a solenoid which turns the stationary brake plate, causing it to ride up a helix on the fixed housing, and thus withdrawing it axially from the shaft-disc. In Fig. 5, not shown, brake disengagement is by a solenoid-operated subsidiary lever, shaped like the main starting lever 15 and arranged adjacent to it on its pivot 14 to act on the projection 12 in the same manner, but to the extent of brakerelease only. In this case the worm-sleeve 27 is permanently driven at inching speed by the main motor and is permanently connected with the shaft 10 through a wedge-type one-way clutch, which is overrun during normal operation, but transmits inching drive when the main clutch and brake are disengaged. The auxiliary motor may be used for stepping or inching, in which case it drives synchronously with the machine and is unitary with the contactbreaker 47-49.