| 摘要 |
PURPOSE:To stop a sewing-machine needle accurately and rapidly at the predetermined position by mounting a low-speed detecting circuit at an output terminal of a position detector and precisely detecting the revolution of a variable- speed motor at low speed as one of prior conditions for stopping the needle at the predetermined position. CONSTITUTION:When the direction of sewing is changed during the revolution of the variable-speed motor 11 at predetermined speed, the stoppage speed signals 200, 202 of 0 are outputted to the FFs 44, 68 of a control circuit 42 from a speed instruction section 12 when an operation pedal 34 is set at a neutral position, the starting signals 212 of 1 and intermediate speed signals 224 are outputted to a drive circuit 48 from the FF44 during a period when stoppage is prepared, and the motor is maintained at prescribed intermediate speed. When low-speed detecting signals 216 are outputted from a low-speed detecting circuit 50 using positional detecting signals 208, 210 from a position detector 40 as input during the period and left-and-right positional detecting signals 206 are outputted from a needle left-and-right position detector 38, reset signals are outputted to the FF44 from an AND gate 64, brake signals 224 are outputted to the drive circuit 48 through a brake one-shot circuit 66, and the motor 11 is stopped. |
