will be understood from the following description a backward movement of piston 4a is merely a stroke or a movement for a reset action of cloth clamp 2 this movement serves to supply hydraulic oil back into circuit 7 as well as cylinder oil side 4c as a whole on the other hand a forward movement thereof the direction of the arrow ar is for moving cloth clamp 2 utilizing electro mechanical functions of the invention referring now to fig3 which shows a typical speed variation in time for cloth clamp 2 a time portion of i to ii is a preliminary time of movement up to a stitch job which stitch job is indicated by the next time portion of ii to iii and the last time portion of iii to iv is a movement after finishing of the stitching and wherein l1 is a low speed approach to a stitch start without stitch the operation of the present invention is hereafter explained with reference to the operations and behaviors of cloth clamp 2 and related elements in connection with the movement thereof as shown in fig3 at the start of the movement i piston 4a has been brought to the backward position in cylinder 4 by a reset action in the previous cycle and valve 6 is set to supply air to cylinder side 4b then piston 4a is allowed to start moving with a high speed h1 by the action of opening the two serial valves 9 10 at the end of high speed travel h1 contact element.