Sash lock

A sash lock, comprising:

• a base member;
• a latch cam having a latch cam shaft for rotatably mounting the latch cam on the base member;
• a locking member for unlockably locking the latch cam against rotation thereof on the base member, the locking member having a cylindrical body portion which coaxially surrounds the cam shaft and is shiftable along the same in one direction for locking and in an opposite direction for unlocking the latch cam, the locking member also having a leg, which projects from one end of the cylindrical body portion, and having means defining a locking cam surface which projects from another end of the cylindrical body portion, the latch cam having a guide opening to guide the leg of the locking member in the locking and unlocking of the latch cam, and the base member having a recess which can be aligned with the guide opening by rotation of the latch cam on the base member to permit, when the guide opening is aligned with the recess, reversible insertion of the leg in the guide opening and recess to lock the latch cam to the base member;
• a knob having a knob shaft which coaxially, rotatably pivots the knob to the cam shaft and to the cylindrical body portion of the locking member, the knob also having a portion which defines a knob cam surface conformably matching the locking cam surface for the locking and unlocking of the latch cam, the knob cam surface and the locking cam surface each having a recessed flat cam portion, a projecting flat cam portion, and an inclined cam portion interconnecting the flat cam portions, and the flat cam portions being normal to the shaft;
• and
• a spring on the base member and latch cam, urging the locking member against the knob cam surface;
• whereby, when the recessed flat portion of the knob cam surface and the projecting flat portion of the locking cam surface are mutually engaged, the spring shifts the locking member in the direction for unlocking;
• and when the projecting flat portions of both surfaces are mutually engaged the spring is counteracted thereby, the locking member is shifted in the direction for locking, and the leg is inserted in the recess, locking the latch cam to the base member.