Importance

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Abstract

A modulating relief valve comprising a main relief valve and a dome pressure control system. The main relief valve has an inlet subject to system pressure, an outlet, a valve member normally sealing the inlet, a piston that rises and falls wit the valve member, and a dome adjacent to the piston, the dome having a dome pressure. The dome pressure control system is attached to the main relief valve. In one embodiment, the dome pressure control system has a body, a beam inside the body attached to the body at a pivot point, an input pressure module creating a first force on the beam, the first force being related to the system pressure and tending to rotate the beam in a first direction, a mechanism for setting a set-point pressure, the set-point pressure creating a second force on the beam, tending to rotate the beam in a second direction opposite the first direction, a control valve that exerts an additional force on the beam tending to rotate the beam in the first direction, the additional force having one component that is related to the dome pressure, the control valve allowing dome pressure to be exhausted when the beam is rotated in the first direction thereby allowing the main valve member to open, and the control valve allowing system pressure to pressurize the dome when the beam is rotated in the second direction. In another embodiment, the dome pressure control system further includes a negative feedback system. In another embodiment, the dome pressure control system does not include a beam and is instead configured in a stacked arrangement.

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First Claim