Abstract: A sewing machine having a power-driven needle has an endless feed belt for moving workpieces beneath the needle. The belt stops and advances, and there is provision for measuring the movement of the belt upon each advance of the belt. In response to this measurement, the belt is stopped, thereby to ensure that the belt moves only a predetermined distance beneath the needle each time the belt advances. To advance the belt, there is a friction roll in contact with the belt, a back-up roller on the opposite side of the belt from the friction roll, and structure selectively to apply the back-up roll forcibly against the belt and to move the back-up roll away from the belt, thereby respectively to drive the belt and to interrupt the drive to the belt.

Abstract: Yarn break in a short seam sewing machine is determined by detection of yarn swinging and wherein the sewing machine is stopped in response to the detection.