Patent ID: 7364571

Claim:
A medical apparatus flow restrictor, comprising: a housing having an inlet and an outlet, and a fluid path defined through said housing between said inlet and said outlet; at least one pair of opposed restriction devices seated within said housing between said inlet and said outlet, said restriction devices comprising opposing planar surfaces placed in contact against each other in an axial direction, a first one of said surfaces being carried on a first continuous rigid restriction device, the second one of said surfaces being carried on a second rigid restriction device that is continuous except for at least one opening therethrough, said opening being disposed in communication with said inlet and said outlet, said restriction devices defining outermost peripheral edges, said restriction surfaces disposed in said flow path such that fluid delivered to said inlet always passes between said opposing surfaces via said outermost peripheral edges of said restriction devices and said opening of said second continuous restriction device prior to flowing from said outlet; and wherein said opposing surfaces have a random surface roughness and opposed surface area defining a random flow field between said opposed surfaces, the degree of said random surface roughness and surface area of said random flow field defined as a function of a desired flow rate of fluid through said restrictor, and wherein said random flow field is defined by a random pattern of voids, spaces, valleys and protrusions between said opposing planar surfaces and defines the sole regulated restrictive flow path through said restrictor for delivering a desired flow rate.