Patent ID: 8141792

Claim:
A pressure controller for controlling a set pressure of a valve, the valve comprising a valve shaft and a movable part comprising a diaphragm to be driven by a differential pressure, wherein the pressure controller is attachable to and detachable from the valve, and the valve is functional when the pressure controller is detached, wherein, when the pressure controller is attached to the valve, the pressure controller provides the movable part of the valve with a predetermined displacement to control the set pressure, wherein the diaphragm has a first surface and a second surface, which is opposite to the first surface, wherein the first surface of the diaphragm faces a downstream side of the valve shaft, wherein the diaphragm is not in contact with a space of an upstream side of the valve shaft, and wherein the diaphragm drives the valve shaft by being displaced by the differential pressure between a space of the downstream side of the valve shaft and a space facing the second surface of the diaphragm.