Heretofore seat valves of this type have been designed in such a way that in the open position of the valve the frictional forces of the flow as well as the forces of reaction of the flow pressure act in an opening sense, i.e., contrary to the closing force of a spring, for instance.

A disadvantage of these designs is that the so-called pressure point effect arises which means that the pressure medium flow cannot be changed continuously in conformity with the force exerted externally. Reducing ValvesInstead the process is disturbed by flow forces after opening of the seat valve to such an extent that the proportionality between control force and pressure medium flow no longer exists. Hysteresis phenomena will arise within the range of pressure drop as well as within the range of pressure increase.

German Pat. No. 842,574 discloses a pressure relief valve in which the control pressure acts upon an annular surface on the closure member, the latter opening in opposition to the direction of flow,FILTER SERIES thereby causing the pressure of the pressure medium which flows away through a throttling member, to be applied to the proper valve surface at the shutoff cross section. In this way the pressure adapts itself to the operating conditions in the hydraulic circuit.

MORE NEWS

2011-12-02

Back