Shut-off valve
OwnerHans-Peter Altmanninventor
Life of this patent
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Abstract
The invention relates to a shut-off valve equipped with two pilot-valves and a main control-piston, the said valve connecting in inlet with an outlet when an upper switching pressure is reached and breaking this connection again when the pressure drops to a lower switching pressure. In order to reduce leakage and to improve the switching process, the pilot-valve (12), which determines the lower switching pressure, is in the form of a seat-valve held open by spring-force, the said pilot-valve closing off a control-line when the lower switching pressure is exceeded, and a second flow-path (21) being provided which is interrupted both by the main control-piston (3), in the shut-off phase, and by the pilot-valve (13) which determines the upper switching pressure, at least when, and shortly after, the shut-off (see drawing).
Claims8
A shut-off valve for connecting an inlet feeding a hydraulic system to an outlet when an upper switching pressure is reached in the hydraulic system and for breaking this connection when a lower switching pressure is reached in the hydraulic system, comprising
- (a) a main control-piston (3) which, in a first switching position, breaks the connection between the inlet (P) and the outlet (T) and, in a second switching position, makes the said connection;
- (b) a restoring spring (5) urging the main control-piston (3) towards the first switching position;
- (c) a first effective area (7), on the main control-piston (3) in a first control-chamber (6), which is acted upon by a control-pressure, the value thereof being controlled by a first pilot valve (12) and a second pilot valve (13) and which loads the said first effective area (7) in the same direction as the restoring spring (5);
- (d) a second effective area (8) on the main control-piston (3) in a second control-chamber (9), which counteracts the said first effective area (8), is of the same size, and is subjected permanently to the pressure of the hydraulic system (A);
- (e) a first pilot-valve (12) which, when the pressure falls short of the lower switching pressure, opens a connection between the hydraulic system (A) and the first control-chamber (6);
- (f) a second pilot-valve (13) which, when the upper switching pressure is exceeded, opens a connection between the first control-chamber (6) and the outlet (T), characterized in that
- (g) the first pilot-valve (12) is a seat-valve loaded by a control-spring (55), said first pilot-valve (12) being held open by said control-spring (55) when pressure is below the lower switching pressure and whose seat-surface (29) is exposed permanently to the pressure of the hydraulic system (A) and which, when the lower switching pressure is exceeded, causes the said seat-valve to close tightly;
- (h) a second flow-path (21) exists between the hydraulic system (A) and the first control-chamber (6), said second flow path (21) being opened by the main control piston (3) in its first switching position and being closed thereby in the second switching position thereof, said second (21) flow-path also passing through the second pilot-valve (13) and being closed thereby when the upper switching pressure is reached;
- (j) the pressure in the second flow-path (21) between the main control-piston (3) and the second pilot-valve (13) serves as the control-pressure for the second pilot-valve (13).
Dependencies are inferred from the claim text.