Starting valve

In a fluid pressure installation having a starting valve interposed between and in communication with each of first and second pressure components for controlling the build-up of pressure in said installation, one of said components at the commencement of the build-up of pressure in said installation having a higher pressure than the other of said components and wherein the starting valve is operable at the commencement of pressure build-up in said installation to enable a gradually increasing flow of pressure fluid from said one of said components to the other of said components, the improvement wherein said starting valve comprises:

• a) a housing having a first pressure medium opening in communication with said one of said components and a second pressure medium opening spaced from said first opening in communication with said other of said components;
• b) a pressure medium flow channel in said housing communicating with both of said first and second openings and through which said pressure medium may flow from either one of said openings to the other;
• c) a piston mounted in said channel for movement from a closed position in which the flow of pressure fluid through said channel is relatively restricted to an open position in which the flow of pressure fluid through said channel is relatively unrestricted, said piston having a first pressure surface in communication with said first opening and a second pressure surface equal in area to that of said first pressure surface and in communication with said second opening, the pressure prevailing at said first opening being operable at all times to generate a first force on the piston via said first pressure surface, and the pressure prevailing at said second opening being operable at all times to generate a second force on said piston via said second pressure surface, both of said first and second pressure surfaces having a direction of action which urges the piston toward said open position;
• d) spring means biasing said piston toward said closed position, said spring means having a biasing force greater than the sum of said first and second forces at the commencement of pressure build-up in said installation and while said piston is in said closed position;
• and
• e) throttle means for enabling a flow of pressure medium through said channel while said piston is in said closed position and in a direction from the opening having the higher prevailing pressure to the opening having the lower prevailing pressure regardless of which of said openings has the higher prevailing pressure, thereby causing the lower prevailing pressure gradually to increase and gradually increase the sum of the first and second force until the sum of said first and second forces exceeds the biasing force of said spring means and effects movement of the piston to said open position,
• f) the equality of the areas of said pressure surfaces enabling movement of said piston from said closed position toward said open position in response to the same pressure build-up regardless of whether the pressure medium flows from said first opening toward said second opening or vice versa.