Flowable material passage with interposable slide member

Means for controlling the flow of a flowable material comprising, in combination,

• a body defining upstream and downstream passages respectively communicating with a slide channel extending transversely to the passages through the body, the body having a closed annular flat first sealing surface defining a first opening communicating between the slide channel and the contiguous end of one of said passages,
• a slide member having a surface overlying said first sealing surface, being slidable in the slide channel and having an aperture portion adapted to permit the flow of said material within the opening defined by said first sealing surface between the upstream and downstream passages,
• means to move the slide member to advance said aperture portion from a first position to a second position relative to said first opening,
• a seal member at one end of the other of said passages, being sealingly movable relative to the body in a direction transverse to the slide channel and having a closed annular flat second sealing surface directly opposing said first sealing surface and defining a second opening opposing said first opening, said second opening communicating between said other of said passages and said aperture portion, and
• compression spring means external to the passages and adapted to exert a force between the body and the seal member, said force urging said second sealing surface against the slide member and producing a sealing force therebetween which is constant and uniformly distributed over the contacting surfaces thereof at all positions of the slide member in said movement.