Hydraulic circuit for cylinder

A hydraulic circuit for a cylinder in a hydraulic power transmission for controlling pressurized oil flow to and from two oil chambers including a load holding oil chamber and a load lowering oil chamber in the cylinder, comprising:

• a directional control valve in communication with a pressurized oil source and connected between said pressurized oil source and said two oil chambers:
• a logic valve connected between directional control valve and said load-holding oil chamber in said cylinder, said logic valve having first and second ports connected to said directional control valve and to said load-holding oil chamber, respectively;
• a selector valve having means for communicating a spring chamber of said logic valve with a conduit between said first port and said directional control valve when said directional control valve is switched to a position by said pilot operating valve wherein pressurized oil is supplied to said load lowering chamber of said cylinder and having means for communicating said spring chamber with said second port in at least one other operational phase,
• including a pilot operating valve, wherein said directional control valve comprises a pilot change-over valve switchable by pilot pressure from said pilot operating valve,
• wherein said selector valve comprises a pilot change-over valve switchable by a primary pressure of said pilot operating valve, including an auxiliary change-over valve connected between said selector valve and said primary pressure of said pilot operating valve for controlling said primary pressure to said selector valve, said auxiliary change-over valve being switchable by said pilot pressure from said pilot operating valve.