| 摘要 |
A sewing machine with spooling equipment. For a spooling operation, an armshaft of the sewing machine can be disconnected from a motor drive of the machine. Through a pulse generator for delivering pulses, the armshaft is coupled to a circuit for controlling the speed of the sewing motor. The circuit comprises an operational amplifier designed with a feedback network. To permit an automatic switching of the operational amplifier to regulation or control sewing and spooling, the feedback network of the operational amplifier comprises two resistance members connected in parallel, of which one can be disconnected by a switch which is controlled by the pulse generator. To simplify the switching, the switch is designed as an analog switch whose control line is connected to the output of a control circuit having one end connected to a starter resistor to which the operational amplifier is responsive, and its other input connected to the pulse generator. |
