Abstract: When arch clamp feet are replaced with other, set screws fastening a retaining plate are all removed, and the same set screws are fastened again to the retaining plates after the replacement of the arch clamp feet, which takes time and labor. Accordingly, the replacement of the arch clamp feet involved in the change of working process in a sewing mill, causes the deterioration of the rate of operation. A arch clamp foot pressing device is provided with a carrying unit which moves arch clamp foot lifting levers substantially horizontally along axes connecting between tip end portions and base end portions of the arch clamp foot lifting levers while it is guided by a pin, wherein the arch clamp foot lifting levers are moved in the direction of the base end portions by the carrying unit so that the tip end portions of the arch clamp foot lifting levers are disengaged from slots of arch clamp feet.

Abstract: A sewing machine is provided with a workpiece clamping unit which clamps and carries a workpiece along the surface of the bed during stitching operation, and a workpiece clamping unit driving mechanism comprising a driving means and a motion converting means. The driving means comprises first and second drive shafts, first and second driving sources for driving the first and the second drive shaft, and first and second compound plate cams fixedly mounted respectively on the first and the second drive shafts. The motion converting means converts the angular motions of the first and the second drive shaft into motions parallel to the upper surface of the bed (6) of the sewing machine.