Fluid flow regulating valve and method

Volumetric flow regulating valve, comprising:

• a housing having a passage, first and second inlets arranged to receive pressurized fluid, a first outlet connectable to a reservoir, and a second outlet;
• a valving element reciprocable in said passage and having (a) a first surface having a first area and defining with said housing a first fluid-containing chamber communicating with said first inlet, (b) a second surface having a second area and defining with said housing a second fluid-containing chamber, and (c) a peripheral recess;
• means for supplying to said first chamber fluid at a first pressure;
• a source of pressurized fluid connected to said second inlet;
• means for maintaining the pressure of fluid in said second chamber at a regulating pressure, said valving element being movable in said passage between at least one first position in which said second inlet communicates with said second outlet and at least one second position in which said second inlet communicates with said first outlet, the ratio of said first area to said second area at least approximating the ratio of said first pressure to said regulating pressure;
• a first flow restrictor provided in said supplying means;
• and
• a second flow restrictor provided in a conduit forming part of said maintaining means and connecting said second outlet with said second inlet, said first and second flow restrictors respectively defining first and second orifices for the flow of fluid to the respective chambers and the ratio K of the areas of said first and second orifices corresponding to a factor of the ratio V of the area of said first surface to the area of said second surface and the ratio QVST/QST of the volumes of leak fluid flow, if any, through the first orifice and the second orifice, K>1 when V>1 and Q>1.

A method of compensating for temperature-induced changes of a regulating fluid pressure established by a valve which is operated by fluid at a pilot pressure supplied by a first conduit containing a first flow restrictor and wherein a valve housing defines a passage for a reciprocable valving element having a first surface defining with the housing a first chamber receiving fluid at pilot pressure from the first conduit by way of a first inlet of the housing, the housing further having a second inlet connectable with a source of regulating fluid, a first outlet and a second outlet, the valving element further having a second surface defining with the housing a second chamber receiving fluid at regulating pressure by way of a second flow restrictor in a second conduit and a recess arranged to establish communication between the first chamber and the first outlet in at least one first position of the valving element, and between the second inlet and the second outlet in at least one second position of the valving element, comprising the steps of:

• maintaining the ratio of pilot pressure to regulating pressure at least close to the ratio of the area of the first surface to the area of the second surface;
• and
• maintaining the ratio of the orifice size in the first flow restrictor to the orifice size in the second flow restrictor at a value at which the influences of pressure losses at the orifices due to leakage, if any, of hydraulic fluid between the housing and the valving element upon the regulating pressure at least substantially balance each other.