Control apparatus for hydraulic motor

Claim 1

A control apparatus for a hydraulic motor for use in a construction vehicle driven by hydraulic power, comprising: (a) a hydraulic motor connected to the running gear of the vehicle; (b) a hydraulic pump serving as a pressurized fluid supply source to supply hydraulic fluid into said hydraulic motor; (c) a manually operable directional control valve connected across supply and discharge conduits which extend between said hydraulic motor and said pressurized fluid supply source; (d) a brake valve means connected across said conduits which extend between said directional control valve and said hydraulic motor, said brake valve means including a counterbalancing valve and two relief valves, said counnterbalancing valve and said relief valves all being connected across said supply and discharge conduits which extend between said manually operable directional control valve and said hydraulic motor; and (e) a selector valve adapted to control the supply of control pressurized fluid, which is introduced through a shuttle valve connected across said conduits, into a displacement control cylinder contained in said hydraulic motor, said selector valve being a pilot operated type selector valve which can be remotely controlled by pilot pressurized fluid supplied from an external pressurized fluid supply source through a pilot fluid conduit in which a remote controlled solenoid operated control valve is provided for selectively connecting said selector valve and a bottom side pressure chamber of said displacement control cylinder with said external pressurized fluid supply source and with a drain conduit.