Fenestration cam lock assemblies and methods

A fenestration lock assembly for securing a first frame member of a fenestration unit to a keeper attached to a second frame member of the fenestration unit and thereby preventing a relative adjustment of the first and second frame members in a first direction of motion, the lock assembly comprising:

• a housing comprising a base and a cover, the housing configured to be secured to the first window frame member and defining an internal space;
• a lock bolt slidably mounted in the internal space of the housing and configured to move in alternate rearward and forward directions along a locking axis between a retracted position and an extended position, the lock bolt in the extended position configured to extend in the forward direction from the housing to engage the keeper, and the lock bolt in the retracted position configured to retract in the rearward direction at least partially into the housing to disengage the keeper;
• a rotatable handle operably connected to the cover of the housing, the handle comprising a shaft and a lever portion, the handle configured to rotate the shaft about a shaft axis as the handle portion rotates about the shaft axis, wherein the shaft axis is generally transverse to the locking axis;
• a rotatable cam connected to the shaft of the handle, wherein the cam is configured to rotate about the shaft axis with the shaft as the lever portion of the handle is rotated about the shaft axis, wherein the rotatable cam comprises an external cam surface that transitions from an extended radius at a first location to a retracted radius at a second location, wherein the extended radius is measured between the shaft axis and the external cam surface at the first location and the retracted radius is measured from the shaft axis and the external cam surface at the second location, wherein the retracted radius is greater than the extended radius;
• a follower in the internal space of the housing, wherein rotation of the cam about the shaft axis slides the follower along the locking axis, and wherein the follower moves the lock bolt between the retracted position and the extended position along the locking axis as the cam rotates about the shaft axis, wherein the follower bears against the external cam surface at the first location when the lock bolt is in the retracted position and the follower bears against the external cam surface at the second location when the lock bolt is in the extended position, such that a leading edge of the lock bolt is located closer to the shaft axis when the follower bears against the first location of the external cam surface and the lock bolt is in the retracted position than when the follower bears against the second location on the external cam surface and the lock bolt is in the extended position;
• a detent washer connected to the shaft of the handle such that rotation of the shaft about the shaft axis rotates the detent washer about the shaft axis;
• a detent washer cavity in the housing, wherein the detent washer is located in the detent washer cavity, and wherein the detent washer is retained in a locked configuration in the detent washer cavity when the lock bolt is in the extended position until the handle is manually rotated about the shaft axis;
• and wherein the detent washer is retained in an unlocked configuration in the detent washer cavity when the lock bolt is in the retracted position until the handle is manually rotated about the shaft axis;
• and
• a biasing element located in the base of the housing, the biasing element acting on the lock bolt and configured to apply a biasing force on the lock bolt in a direction that moves the lock bolt to the extended him position, and wherein the biasing force alone cannot move the detent washer and the detent washer cavity out of the unlocked configuration.