Top position lock for venetian blinds

Claim 1

A top position lock for a venetian blind including a head and a depending slat assembly, said top position lock comprising: a mounting structure in the head, a cord guide carried by the mounting structure, a jam member shiftably carried by the mounting structure for movement between a lower free position spaced below said guide and along a path obliquely upwardly toward said guide to an upper locking position proximate to said guide, a pull cord connected to said slat assembly for raising and lowering the latter upon respective downward and upward cord movement, said pull cord being trained over said guide and depending gravitationally between said guide and jam member in engagement with the latter, downward cord movement in engagement with said jam member urging the latter downwardly to its free position and upward cord movement in engagement with said jam member urging the jam member upward to jam said cord against said guide, detent means shiftably carried by said head extending across said jam member path in upward limiting engagement with said jam member to maintain the latter in its free position, and detent shifting means operative to shift said detent means out of said path to release said jam member for upward movement to jam said cord against said guide, said detent shifting means depending into the path of said slat assembly at its top position for release of said jam member to its upper position only when said slat assembly is fully raised.