De-master key cylinder assembly

Claim 1

IN A PIN TUMBLER CYLINDER LOCK HAVING A ROTATABLE PLUG WITH A LONGITUDINALLY EXTENDING KEYWAY AND COLUMNS OF UPPER AND LOWER SPRING-ACTUATED FREELY MOVABLE PIN TUMBLERS, AN ELONGATED DEFORMABLE WAFER EXTENDING LONGITUDINALLY IN SAID KEYWAY HAVING A VERTICAL CROSS SECTION CORRESPONDING TO THE CONTOUR OF AND POSITIONED WITHIN THE KEYWAY BELOW AND SUPPORTING AT LEAST ONE LOWER PIN TUMBLER IN A POSITION PERMITTING ROTATION OF THE PLUG BY A FIRST KEY WHICH LIFTS THE OTHER TUMBLERS IN THEIR COLUMNS TO THE SHEAR-LINE, A PIN PROVIDING A RIGID ABUTMENT IN SAID PLUG AGAINST WHICH THE REAR EDGE OF SAID WAFER ABUTS TO AID IN POSITIONING THE WAFER IN THE KEYWAY, AND A SECOND KEY WHICH WHEN INSERTED IN THE KEYWAY ENGAGES AND IDSLODGES THE WAFER AND MOVES IT TO A SECOND EXTENDED POSITION WHERE THE WAFER IS DEFORMED AND LODGED UNDER SAID PIN TO ALLOW ALL THE TUMBLERS TO INTERSECT THE SHEARLINE UPON WITHDRAWAL OF THE SECOND KEY AND RENDER THE FIRST KEY INOPERATIVE.