Patent GB-962506-A (GB)
Title: An electric drive for sewing machines
IPC: H02P29/00
Filed: 1962-08-02
Abstract: 962,506. Controlling clutch-brake combinations. E. BECKER, and K. NOTZ, [trading as QUICK-ROTAN, BECKER & CO.]. Aug. 2, 1962 [Aug. 16, 1961], No. 29667/62. Heading F2L. [Also in Division D1] An electric drive for a sewing- machine comprises a high-speed drive, a reduced-speed drive and a third drive which may be either a slow reversed drive or a slow forward drive, the drives being operated via switching means in a predetermined sequence so arranged that the reduced-speed drive operates before the highspeed drive when the machine is started, and the reduced-speed drive operates before the third drive when the machine is stopped. A sewing-machine 5, Fig. 1, is driven by a pulley 4 rigid with a clutch plate 3 normally spring- biased into engagement with a rotary disc 10. Energization of a solenoid 6 associated with clutch plate 3 shifts the latter into engagement with a flywheel 2, driven by a motor 1, to operate the sewing-machine. A worm-wheel 11 rigid with disc 10 meshes with a worm 12 on a shaft, the respective ends of which carry axiallyshiftable friction discs 17 and 18. A rotary electromagnetic clutch 19, aligned with an adjacent disc 17, is driven by a belt 21 from a pulley 24 on the shaft 26 of motor 1. A rotary electromagnetic clutch 20, aligned with and adjacent disc 18, is driven in the reverse direction by a belt 22 from a pulley 25 on shaft 26. Stationary electromagnetic brake discs 27 and 28 are adjacent and aligned with discs 17 and 18, respectively. Depression of a treadle 29 closes a contact 30 for energizing a solenoid 6 and a relay 31, the latter then closing contacts 33<SP>1</SP>, 34, whereby the sewing-machine is driven via flywheel 2 at a speed of 6000 r.p.m., and clutch 19 is energized, via a switch 38 and the contact 33, to drive disc 10, via friction disc 17, at a speed of 600 r.p.m. Relay 31 and clutch magnet 19 are arranged to respond faster than solenoid 6, whereby disc 10 is always driven before clutch plate 3 is disengaged therefrom. On release of treadle 29 solenoid 6 is de-energized, but relay 31 remains energized via contact 32 and slip-ring 40, whereby clutch disc 3 engages disc 10 to drive the sewing-machine at 600 r.p.m. When an insulating segment in ring 40 engages the associated brush, relay 31 is de-energized, whereby clutch 19 is de-energized and brake magnets 27, 28 are energized to co-operate with disos 17 and 18 for stopping the machine with the needle in the lowered position. If, when treadle 29 is depressed, a switch 36 is simultaneously operated to connect contact 32 to a slip-ring 41 and contact 34 to a slip-ring 41, the machine will be stopped, after release of treadle 29, with the needle in the raised position, when an insulating segment in slip-ring 41 engages the associated brush. Closure of contact 34, upon de-energization of relay 31, will then serve to energize a relay 37, via a slip-ring 42, to operate the switch 38 for de-energizing the brake magnets 27, 28 and energizing the clutch 20. The machine will then be driven slowly, via disc 18, for a short distance in the reverse direction to disengage the looper from the seized loop, and will stop when an insulating segment in ring 42 engages the associated brush. In a modification, Fig. 3a, partial depression of the treadle 29 is arranged to close a contact 30<SP>1</SP> to energize relay 31, whereby the machine will run continuously at low speed. Full depression of treadle 29 will also close a contact 35 to energize solenoid 6 for driving the machine at full speed. In a further modification, clutch 20 is driven, in the same direction as clutch 19, through reduction gearing so arranged that on energization of clutch 20 the machine will run at 60 r.p.m. in the forward direction, and brush 42 is permanently connected to contact 34. The arrangement is thereby such that, on release of treadle 29, the machine will rotate at 600 r.p.m. under the control of either ring 40 or ring 41, as selected by switch 36, to stop in the raised or lowered position, respectively, and will then rotate forwardly at 60 r.p.m. under the control of brush 42 for accurate final positioning of the needle. In yet a further modification, Fig. 6, not shown, the electrical circuit is transistorized.