Pin tumbler cylinder key system

Claim 1

IN A PIN TUMBLER CYLINDER LOCK HAVING A ROTATABLE PLUG, AND A SINGLE ROW OF ALIGNED TUMBLER COLUMNS WITH UPPER AND LOWER SPRING ACTUATED PIN TUMBLERS IN EACH COLUMN, AN INTERMEDIATE PIN TUMBLER DISPOSED BETWEEN AN UPPER AND A LOWER TUMBLER IN ONE OF THE COLUMNS, RESILIENT MEANS ON THE INTERMEDIATE TUMBLER FOR TEMPORARILY SECURING SAID INTERMEDIATE TUMBLER IN THE PLUG WITH UPPER SURFACE ALIGNED WITH THE SHEAR LINE OF THE PLUG, THE TUMBLERS IN THE OTHER COLUMNS EING LIFTABLE BY A TEMPORARY KEY TO THE SHEAR LINE, THEREBY PERMITTING ROTATION OF THE PLUG, AND A FINAL KEY FOR LIFTING THE INTERMEDIATE TUMBLER AND FREEING IT FROM ITS SECURED POSITION, SO THAT WHEN THE FINAL KEY IS REMOVED, THE INTERMEDIATE TUMBLER WILL ASSUME ITS NORMAL POSITION INTERSECTING THE SHEAR LINE, THEREBY PERMANENTLY PREVENTING ROTATION OF THE PLUG BY THE TEMPORARY KEY.