Abstract: An apparatus for adjusting a timing of a needle and a looptaker of a sewing machine provided at a zigzag sewing machine having an upper shaft for driving a needle bar, a lower shaft for driving a looptaker, a machine frame, and a timing belt for connecting and synchronizing the shafts includes a cam member including a first cam surface and a second cam surface, a first arm member and a second arm member supported by the machine frame and a first pulley and a second pulley mounted to the first arm member and the second arm member respectively and always contacting the timing belt, the first pulley following the first cam surface and the second pulley following the second cam surface.

Abstract: In a zig-zag sewing machine wherein a sewing needle is shifted laterally with respect to a hook rotated about a fixed axis, the hook is optimally timed with respect to the needle at each shifted stitch position of the needle by accelerating rotation of the hook to advance it into optimal disposition relative to the needle at one stitch position of the needle and decelerating rotation of the hook to retard it into equally optimal disposition relative to the needle at the other stitch position of the needle.

Abstract: A lockstitch sewing machine, particularly for use as an insole stitcher, having a stitching mechanism arranged for cyclically repeating operation and including a horizontally mounted rotary shuttle, has the shuttle arranged for rotation in a constant direction at a cyclically varying angular velocity such that a major part of each rotation, e.g., a complete rotation takes place in a minor part of each cycle, e.g., one quarter of the cycle. The rotation of the shuttle is provided, e.g., by a Geneva cam.