Single lever, double changeable safe deposit lock

A double changeable tumbler lever type key lock for safe deposit boxes and the like comprising a lock case defining a generally box-like enclosure having front and rear vertical walls, a bolt plate slidably movable along a slide axis adjacent one of said walls between projected locking and retracted unlocking positions having a stack of fence members carried thereon each having a elongated body portion movable along an adjustment path generally transverse to said slide axis, a stack of tumbler levers occupying position in the locked condition of the lock to bar retraction of said fence members and said bolt plate from a projected locking position when in the locking position, the fence members and tumbler levers forming two sets of intercept members having fence and gate companion interfitting means thereon including peripheral gating recesses on one of said sets and protruding foot formations on the other of said sets, said tumbler levers being movable responsive to a pair of keys to adjust the interfitting means thereof to accommodate the companaion interfitting means of said fence members to permit retraction of the bolt to unlocking position, a stationary tumbler lever post extending from a wall of the case extending through slots in the tumbler levers permitting relative displacement and arcuate movement of the tumbler levers relative thereto, the tumbler levers being of generally T-shaped configuration providing a short vertical foot portion and a generally horizontal elongated cross-arm portion having arms projecting oppositely from the foot portion with downwardly facing substantially linearly alined lower edges defining first and second straight lift edges spaced toward opposite ends of the case from said post, said slot being vertically elongated and extending into said foot portion, a first rotatable key plug for insertion of a guard key therein into engagement with said first lift edge of said tumblers for establishing pivot points for the tumbler levers when engaged by a guard key, a second rotatable key plug for insertion of a renter's key therein into engagement with said second lift edge of the tumble lever lift edges for adjusting the tumbler levers to align their interfitting means with the interfitting means of the fence members for unlocking retraction of the bolt, the bolt plate having a shaped opening therein, a driving cam associated with said second key plug to be rotated by the renter's key and having a projection for moving the bolt plate between said locking and unlocking positions, means extending from the bolt plate supporting the fence members of the stack for guided adjustment along said adjustment path to positions corresponding to a predetermined range of key shapes and clamping means associated therewith for selectively clamping the fence members in their adjusted position and releasing them for movement responsive to key adjustment of the tumbler levers.