Link 1 is connected by a screw pair to shank a of wedge 6. Shank a passes freely through a hole in wedge 2 . Wedges 2 and 6 are guided by pins b which slide along slots c in the fixed base. Wedges 2 and 6 slide along the bevelled ends of plungers 3 which are guided by setscrews sliding along slots d in the plungers. When link 1 is turned (screwed on), wedges 2 and 6 force plungers 3 upward, clamping workpiece 4. Spring 5 returns right-hand wedge 2 and left-hand wedge 6 with its shank a to their initial positions when link 1 is released.
$239$SL,GC$