| 摘要 |
A camless automated thread cutting system for an electronic lockstitch pattern tacking sewing machine having a sewing needle driven by a main shaft and having a knife mechanism in proximity with the needle for cutting thread at the end of a pattern sewing cycle. The cutting system comprises a pneumatic cylinder for mechanically engaging the knife mechanism through a mechanical linkage in the machine, a solenoid-actuated air valve in fluid communication with the pneumatic cylinder, a programmable logic controller (PLC), and a pair of independently adjustable discs mounted on the main shaft of the sewing machine and operatively coupled to a proximity sensor which supplies an electrical signal to the PLC. The PLC is responsive to a machine signal indicative of the end of a sewing cycle and to the proximity sensor signal for generating a control signal for actuation of the valve so as to initiate and subsequently terminate a knife movement sequence at the end of the sewing cycle. The discs are preferably parallel, overlapping discs and the proximity sensor signal is preferably based on detection of the leading edge of one disc and the trailing edge of the other disc during rotation thereof. |
