Tumbler wheel, changeable combination key lock construction

A tumbler wheel type lock mechanism comprising a plurality of peripherally gated tumbler wheels supported for rotation about a common axis, a peripherally gated control cam rotatable about said axis, a bolt movable between projected and retracted positions, a fence lever having a fence and a depending nose and an abutment shoulder, means pivotally connecting the fence lever to the bolt for arcuate movement between a raised inactive position spacing the fence and nose out of contact with the tumbler wheel and control cam peripheries and a lowered active position locating the fence and nose in said gates, the control cam being operatively coupled to said nose at said active position for retracting the bolt upon predetermined rotation of the control cam, manually operable means for adjusting the angular positions of the tumbler wheels, coactive latching members for releasably latching said fence lever in said raised inactive position including a first latching member on the fence lever and a second latching member in the form of a stationary resilient latching element located at a fixed position above the fence lever to receive and releasably capture said first latching member and thereby hold the fence lever at said raised inactive position, a releasing spring adjacent said abutment shoulder having a movable leg capable of movement between a stressed spring energy storage position spaced from said shoulder and an impact position engaging the latter, the movable spring leg having a portion extending into the path of movement of a projection on the control cam for shifting said movable leg to the stressed position upon selective rotation of the control cam and said projection being shaped to release said movable leg from such stressed position for rapid spring driven movement to impact against said shoulder and impel the fonce lever toward the control cam to a position momentarily engaging the fence with the tumbler wheel peripheries without fully withdrawing said first latching member from the second latching member, the second latching member being operative to return the fence lever to said raised inactive position when the tumbler wheel gates are not aligned with the fence following the momentary engagement with a misaligned tumbler wheel periphery and the latching members being decoupled from each other to release the fence lever to said lowered active position responsive to such impelling of the fence lever toward the control cam when the tumbler wheel gates are properly aligned with the fence.