Control system for amphibious hydraulic excavator

Claim 1

An amphibious hydraulic excavator comprising: an amphibious crawling truck; hydraulic motors for driving said crawling truck; a revolving platform mounted rotatably on said truck; a further hydraulic motor for rotating said revolving platform; a shovel assembly mounted on said revolving platform and composed of a boom, an arm and a bucket which are actuated by respective hydraulic cylinders; an engine room mounted on said revolving platform; a prime mover installed in said engine room; hydraulic pumps driven by said prime mover for delivering pressure fluid; pilot operated directional control valves for controlling the flows of pressure fluid to and from said hydraulic motors and said hydraulic cylinders, respectively; a snorkle means extending upwardly from the engine room for serving as an air suction and exhaust conduit for said prime movers; means for actuating said directional control valves, said actuating means being activated by radio signals and including a radio receiver for receiving triggering signals; a source of pilot pressure fluid; fluid lines connecting said source of pilot pressure fluid with the respective directional control valve; solenoid valves provided on the respective fluid line for actuation in response to the triggering signals received by said receiver so as to control the flows of pilot pressure fluid to said directional control valves, respectively; shuttle Valves positioned on the respective fluid lines downstream of said solenoid valves; by-pass fluid lines connecting between said source of pilot pressure fluid and the respective shuttle valves; and manual control valve means provided on the respective by-pass fluid lines for controlling the flows of pilot pressure fluid to said directional control valves, said manual control valve means being provided for adjusting the flow rate of pilot pressure fluid to said respective directional control valve; and wherein every part of said excavator is fabricated water-tight whereby said hydraulic excavator can be operated either in a remote radio-controlled manner or by normal manual operation.