GB826488A - Improvements in or relating to sewing machines - Google Patents

Abstract

826,488. Sewing machines. PFAFF A. G., G. M. July 13, 1956 [Aug. 2,1955], No. 21642/56. Class 112 Stopping. The circuit through a relay adapted to stop the machine is periodically interrupted in synchronism with the periodic thread tension, the relays having a delayed action such that the machine is only stopped when the thread fails or breaks. The invention is described in connection with a button-hole machine which is automatically stopped, irrespective of the relay control, after a predetermined cycle, the speed of the machine being first reduced to half-speed just prior to stopping. The interrupter comprises a contact 43, insulatingly secured to the machine head and periodically contacted by the end of the take-up spring 41. The machine is started by closing the switch 46 and the current pulses in the circuit do not actuate the relay 69 due to delay action produced by resistance 66 and capacity 71. If, however, contacts 41, 43 remain closed the relay closes contacts 75, 76 to energize electromagnet 51 to reduce the speed of the machine to half-speed, and closes contacts 73, 74 to short-circuit the relay winding 68 by resistance 78. The relay opens it contacts and then closes them again and electromagnet 51 is again energized to stop the machine. The electromagnet may actuate a circuit breaker in the circuit of the machine motor to effect immediate stoppage. The invention may be applied to a multi-needle machine the thread take-up contacts for each needle being arranged in parallel.