Patent GB-1052592-A (GB)
IPC: D05B81/00
Abstract: 1,052,592. Controlling electromagnetic clutches and brakes. WARNER ELECTRIC BRAKE & CLUTCH CO. Jan. 22, 1965 [Jan. 24, 1964], No. 2941/65. Headings F2E and F2L. [Also in Division D1] A sewing machine includes automatic control means for moving the needle to a predetermined stopping position if it does not stop therein by intermittent energization of a clutch. The needle is driven from a motor 35 through shaft 36, clutch 38 having axially engageable elements 49, 54 drawn together on energization of a coil 62, a shaft 31 and a belt drive 28-30 and shaft 19, a brake 64 comprising discs 65, 66 being actuated by energizing coil 72 to stop the needle when the clutch is disengaged. A rotary switch 76 comprises a conductive segment 85, rotatable with shaft 19, having two exposed areas ND, NU of insulating material corresponding to needle down and needle up, and cooperating with wipers W1 W3, a further wiper W2 engaging segment 85. The wipers may be positioned around the segment 85 with areas ND, NU in the same radial plane; more than two wipers and exposed areas may be provided to give other desired needle positions. To permit an operator to selectively stop the needle " up " or " down," a knee-operated lever 86, 88 is provided to close a switch PSS 1 , energize relay PSR and open normally closed contacts PSR 1 and close contacts PSR 2 to include wiper W3 and not wiper W1 in the control means to change from stopping in " needle up " to " needle down " position. Further movement of lever 86 lifts the presser foot through a linkage against a spring bias, Fig. 5 (not shown). Operation.-Main switch 106 is closed to drive motor 35, the clutch being disengaged, and energizes transformer T 1 of which the secondary winding W3 provides a source of voltage for the brake and clutch coils via voltage doubler 109, and winding W4 provides a source of voltage for the needle control circuit via rectifier 110. Depression of treadle 111 closes contacts TS1  to initiate an operation cycle, a relay FSR being energized to close contact FSR1 to energize relay CR to open contacts CR3 to break the energizing circuit 109 (t 2 ),72, CR3, 109 (t 1 )of the brake 64; also closure of contacts FSR2 energizes the clutch coil 62 via 109 (t 3 ), FSR2, rheostat 112, 62, CR1, 109 (t 1 ).The sewing machine now operates at a speed determined by rheostat 112 actuated by treadle 111. By " heeling " the treadle, switch contacts TS1  are opened to de-energize relays FSR, CR to open contacts CR1, FSR2 to de-energize the clutch and to close contacts CR3 to re-energize the brake and stop the needle. The brake is energized from terminals t 1 ,t 2 of doubler 109 initially at, for example, 300 volts, however as capacitor C3 charges, a resistor R1 drops the voltage to coil 72 to its standard rated capacity of, for example, 90 volts. The clutch coil is energized from terminals t1, t3 at, for example, 60 volts. If the needle stops in the desired position then the operating cycle is complete. Needle stopped out of desired position.-To inhibit the needle positioning controls until the machine is stopped, a relay PCR and a capacitor C4 are energized during running of the machine via contacts FSR3; when contacts FSR3 are opened subsequent to " heeling " the treadle, the relay PCR is held " in " until capacitor C4 dissipates its charge, during which time the contacts PCR1, P3R2 are held open and switch 76 deactivated until the needle is stopped. Assuming the machine is pre-set to stop the needle in the " down " position, and the needle is not in this position, then relay CR is energized via rectifier &c. 110, CR, W2, 85, W1,PSR1 and PCR1; thus the contacts CR3 open to de-energize the brake and CR1 close to energize the clutch coil 62 via FSR4. However, contacts PR1 are pulsated by a pulsating relay PR, controlled by contacts PR2 and capacitor C5, so that the driven clutch element and the needle are " stepped " toward the " down position " at which the insulated area ND engages wiper W1 to de-energize relay CR to release the clutch and apply the brake via contacts CR1, CR3 respectively. Single stitching.-Byreleasing the brake and " pulsing " the clutch coil 62 a single stitch may be made. A switch FS adjacent treadle 111 is operated to close contacts FS1 to complete an energizing circuit for relay CR via wiper &c. W3, 85, W2, CR to release the brake and energize the clutch the relay CR remaining energized through wiper W1until the wiper W1reengages area ND. By keeping switch FS depressed the single stitch operation, is repetitive. To remove material from the machinethe operator moves lever 88 to close switch PSS1  to energize relay PSR to open " needle-down" contacts PSR 1 and close " needle-up " contacts PSR2 and contacts PSR3 of a holding circuit so that relay PSR remains energized until relay FSR is energized when treadle 111 is next depressed. Relay CR is energized via relay &c. CR, W2, 85, W3, PSR1, PCR1 to step drive the clutch until the needle is up when wiper W3 engages area NU. Further movement of lever 86 lifts the presser foot. In Figs. 6, 7 and 9 (not shown) the rotary switch 76 is replaced by two light sources and photo-electric cells with a mask carried by the hand wheel of the machine giving the desired stop positions. The clutch and brake control relay becomes energized when a transistor connected to the photo-cells becomes conductive. Other transducers, e.g. magnetic transducers. may be used to signal the desired needle stop positions.