being connected to carrying arm 28 by means of a quick disconnect fitting 30 the composite element 21 forms the base for the clamp assembly 20 and is attached to the sewing machine for movement in the x and y coordinates shown in fig1 the support arm 22 is fixed to the carrying arm 28 the upper clamping element 24 consists of a pair of mated clamp feet 39 and 40 which are each separately mounted on slides 41 and 42 the slides 41 and 42 are in turn mounted for vertical sliding motion in grooves 43 and 44 and are held in place by plate 45 each of the clamping elements is constructed with a window to allow access to the workpiece the shape of this window must be varied depending upon the pattern to be sewn in order to facilitate removal of the feet 39 and 40 to change the size or shape of the window they are secured to the slides 41 and 42 by means of quick disconnect fittings 46 the fittings 46 may consist of screw 47 split collar 48 and wedge collars 49 and 50 in this manner the feet 39 and 40 may be removed quickly without complete removal of the screw 47 in order to force the clamp feet 39 and 40 into engagement with the feed plate 29 spring bars 27 are mounted on either side of arm 22 and are connected to slides 41 and 42 through slots 31 the biasing force of spring 27 is set downward and may be adjusted by tension bolts 51 the unclamping force is supplied by pneumatic piston and cylinder assemblies 52 which are.