| 摘要 |
<p>A thread tension control for an automatic sewing machine is capable of accurately and excellently tightening the upper and lower threads by virtue of the relative movement between a needle and a cloth retainer irrespective of the thickness of the cloth. The controller is provided with a setting means which makes it possible to generate a plurality of setting signals which are different from each other in the timing at which a driving pulse is to be supplied to a driving means for driving the cloth retainer. In relation to a selected setting signal, a shift means shifts the period of supplying a driving pulse to the driving means on the basis of the feed data in a memory means by an actuator means either forward or rearward of a predetermined angle of rotation of the main shaft during the period in which the needle is drawn out of the cloth. Thus, it is possible for the distance between the lower end of the needle and the surface of the cloth to be set at a predetermined minimum length at the time of completion of the feed of the cloth irrespective of the thickness of the cloth.</p> |
