Fluid flow control device

Claim 1

A fluid flow-rate control device comprising: a housing having two interlocking parts; an elastic stretchable membrane clamped along its periphery, inside the housing, between the two interlocking parts, said membrane dividing the interior of said housing into a first chamber and a second chamber; an inlet port of said housing leading from a fluid source and communicating solely with said first chamber; and an outlet port of said housing communicating with said second chamber; wherein said first and second chambers are in fluid communication via at least one passageway extending in part beyond the periphery of the membrane and along an inner surface of at least one of the parts of the housing and leading from said first chamber to said second chamber, said passageway communicating solely with the first and second chambers and including at least one portion comprising a spirally extending channel in which flow is relatively restricted, the dimensions of the passageway remain unchanged during operation, and said membrane is fixedly held and positioned between said chambers so that when said membrane is exposed to a fluid pressure differential, it is stretched and a portion thereof is moved, solely by virtue of its elasticity, between positions closer to said outlet port to cause said portion of said membrane to restrict the rate of flow through said outlet port, and positions farther away from said outlet port to cause said portion of said membrane to increase the rate of fluid flow through said outlet port, whereby the flow of fluid through said outlet port is controlled at a constant rate by said membrane, despite variations in the fluid pressure at, at least, one of the ports.