Patent ID: 7878479

Claim:
An adjustment valve, comprising: a main body provided with a valve chamber at an upper portion thereof, an inflow channel and outflow channel that respectively communicate with the valve chamber, and an opening at a bottom center of the valve chamber with which the outflow channel communicates; and a cylinder provided with a through-hole at the bottom center thereof and a ventilation hole in a lateral surface, the cylinder and main body sandwiching and fixing a first diaphragm therebetween and a bonnet provided with a working fluid communication hole on a top thereof, the bonnet and cylinder sandwiching and engaging the peripheral edge of a second diaphragm therebetween are integrally fixed and wherein: the first diaphragm comprises an integrally formed shoulder section, an attachment section being positioned above the shoulder section and engaging with and fixing with the bottom of a rod, a joining section positioned below the shoulder section that fixes a valve body, a thin film section radially extending from the shoulder section, a thick wall section continuous with the thin film section, and a seal section provided at the peripheral edge of the thick wall section; the valve body is fixed to the joining section so as to enter and recede from the opening of the valve chamber in response to the vertical movement of the rod; the second diaphragm has a central hole, and comprises an integrally formed thick wall section around said central hole, another thin film section radially extending from the integrally formed thick wall section, and another seal section provided at the peripheral edge of the thin film section; the central hole of the second diaphragm is penetrated by a diaphragm hold-down member at an upper shoulder section positioned at a top of the rod, said rod being fixed at a bottom thereof with the attachment section, causing the second diaphragm to be sandwiched and fixed between the diaphragm hold-down member and the upper shoulder section; and the rod is configured so that a bottom portion thereof is disposed with play in the through-hole at the bottom of the cylinder, and is supported by a spring engaged between a step section of the cylinder and the bottom surface of the upper shoulder section in a state such that radial movement is prevented.