36 and of switch arm 40 against the action of torsion spring 43 44 about pin 37 into contact with stop screw 46 by which the end position of stop 39 and thus the sewing position of strip st is determined in the end phase of the pivotal motion proximity switch 41 is actuated whereby first solenoid valve 42 is switched off so that air cylinder 30 is vented through line 61 and connections p and r of the solenoid valve and the air cylinder 30 is supplied with compressed air through connection p and a of solenoid valve 42 and line 60 thereby through piston rod 34 connected to the working piston of air cylinder 30 holder 35 with lever 36 are returned to their rest positions and stop 39 is retracted from the feed path of strip st during this retraction lever 36 is pivoted by spring 43 44 to apply stop 39 to the curved surface of control cam 55 and moves switch arm 40 away from proximity switch 41 a sequence control of the sewing machine is thereby started by which presser foot is lowered as soon as stop 39 has left the contact area of the presser foot and after a short delay the sewing machine is started again to perform the sewing operation beginning with some back stitches for locking the seam during the further reverse motion stop 39 follows the curved surface of control cam 55 and lever 36 is pivoted again into the shown position in which switch arm 30 opposes proximity switch 41 as mentioned above in connection with the operation of the device the switching processes for stopping the sewing operation are released by contact arm 18 as.