Device for controlling a hydraulic motor

A device for controlling operation of a hydraulic motor, comprising:

• a pressure adjusting means which is selectively in fluid communication with a feed passage connected with a pressure fluid pump;
• a directional valve communicating with said pressure fluid pump via said feed passage, said directional valve including load sensing pressure communicating means connected to said pressure activated pressure adjusting means for varying fluid pressure within said feed passage in relation to a load sensing pressure sensed thereby;
• and
• a safety valve means located in said feed passage upstream of said directional valve and arranged to be activated separately from said directional valve to prevent hydraulic fluid under pressure from reaching the directional valve in an emergency, said safety valve means including:
• a pressure activated shut-off valve located in said feed passage and shiftable between a normally open position and a closed fluid flow blocking position, said shut-off valve having:
• a load sensing pressure passage which is connected to said load sensing pressure communicating means,
• a pressure discharge passage,
• said load sensing pressure passage being connected to said pressure discharge passage via said shut-off valve as the latter is shifted from said open position to said closed position so as to depressurize said pressure adjusting means, and
• a valve element with two oppositely facing actuating surfaces of different sizes, the smaller one of which is continuously exposed to the pressure within said feed passage for exerting a bias force in an opening direction of said valve element;
• and
• a pilot valve for selectively bringing the larger one of said actuating surfaces into communication with said feed passage for exerting a force in a closing direction of said valve element.