Lockable valve for hydraulic system

A lockable valve in a fluid line comprising an elongated unitary housing containing a lengthwise cylindrical bore open at one end and closed at the other end and only three spaced bores adjacent said closed other end communicating between said lengthwise bore and the outside of said housing, said three bores being spaced apart from each other along the axis of said lengthwise bore to form an outlet bore, an inlet bore and an outlet bore, said inlet bore permitting the ingress of fluid therethrough into said lengthwise bore, said outlet bores permitting the selective withdrawal of fluid from said lengthwise bore;

• one said outlet bore being connectable to a bypass line connected to a fluid sump and the other said outlet bore being connectable to a control valve of a operational fluid cylinder;
• a piston unmovable by the pressure of the fluid in said cylinder and manually movably mounted in said lengthwise bore having a first head and a second head whose outer surface sealingly fit within the interior surface of said lengthwise bore, a rigid portion spaced inwardly from said outer surface for joining said first and second heads;
• said first and second heads having a width sufficient to close respective said outlet bores, said heads being spaced such that when said first head is positioned to fully close said one outlet bore the remaining other outlet bore is open, and when said second head is positioned to fully close said other outlet bore the remaining said one outlet bore is open;
• said second piston head including a forward portion rigidly attached and extending therefrom to said outside of said housing along said lengthwise bore;
• a spring mounted in said housing and biased to urge said forward portion of said second piston head toward said outside of said housing;
• selective locking means located within said unitary housing and mounted on said forward portion of said second head to lock same to said housing with said forward portion and said locking means in a fully retracted position within said housing whereby said second head closes said other outlet bore and to unlock said piston and cause said spring means to force said piston forward portion to a fully extended position whereby said first head closes said one outlet bore, said inlet bore being in communication only with a respective one of each of said outlet bores in said locked position and said unlocked position.

In a hydraulic fluid system including a hydraulic fluid reservoir, a hydraulic fluid pump, a selective control valve, a hydraulic line between the control valve and the pump, hydraulic means selectively powered via the selective control valve by the hydraulic fluid pressurized by the hydraulic fluid pump from the hydraulic fluid reservoir, the improvement comprising a selectively lockable valve having only three ports including a first inlet port connected to said hydraulic line on the pump side thereof and second and third selective outlet ports, said second outlet port being connected to said hydraulic line on the control valve side thereof, a bypass hydraulic line connected between said outlet port and said reservoir, said lockable valve including a unitary housing and valve means located therewithin, said valve means in the locked condition thereof blocking said second outlet port such that all of the hydraulic fluid from said pump through said first inlet port passes via said third outlet port through said bypass line into said reservoir, said valve means being manually movable to its unlocked condition thereof blocking said third outlet port such that all of the hydraulic fluid from said pump through said first inlet port passes via said second port through said control valve for selectively powering said hydraulic means and thence into said reservoir, said valve means being unmovable by the pressure of the hydraulic fluid in said valve and manually movable between its locked and unlocked conditions, and lock means located within said unitary housing to lock said lockable valve in the locked condition to bypass the hydraulic fluid therethrough, said inlet port being in communication only with a respective one of each of said outlet ports in said locked condition and said unlocked condition.