Patent ID: RE42401

Claim:
A free draining throttling valve comprising: (a) a valve body defining an inlet and an outlet; (b) a first throttling surface positioned between said inlet and outlet, said first throttling surface comprising an island having a generally annular outer peripheral surface; (c) a diaphragm having structure including a primary surface diaphragm and a secondary surface diaphragm , said surfaces primary and secondary diaphragms being spaced-apart and being joined at peripheral edges to form an internal diaphragm volume chamber in said diaphragm structure ; (d) said primary diaphragm having a lower surface defining a mating second throttling surface, said second throttling surface, including an annulus with an inner peripheral surface opposing the outer peripheral surface of said island, at least a portion of said second throttling surface sealingly engageable with at least a portion of said island first throttling surface ; (e) drive means on operably coupled with said diaphragm structure ; (f) operator means cooperable operably coupled with said drive means for selectively positioning said diaphragm between an structure in a flow blocking position in which the second throttling surface is sealingly engaged with the first throttling surface, thereby closing off a fluid flow through said valve, and further for selectively positioning said diaphragm structure in a plurality of open flow control position s in which a throttling gap is established in which a between said first and second throttling surfaces, said throttling gap causing a substantially linear pressure drop occurs in the fluid flow with increasing flow velocity and a flow blocking position in which the primary diaphragm closes off flow at said island .