Patent ID: 7497670

Claim:
A reciprocating fluid transfer pump comprising: a main body block including a fluid supply passage and a fluid discharge passage; a center rod inserted in said main body block and being capable of reciprocating movement relative to said main body block; a barrier membrane attached to an end portion of said center rod, said barrier membrane and said main body block defining a fluid delivering chamber and a driving chamber such that a fluid, once having suctioned into the fluid delivering chamber, is discharged by expanding and contracting said barrier membrane; a main ring engaged via threads with an annular wall of said main body block, said main ring being movable rotationally relative to said main body block to insert the annular wall of said main body block into an annular space defined between an axially extending outer annular portion of said main ring and an axially extending inner annular portion of said main ring such that a peripheral portion of said barrier membrane is clamped and thus fixedly secured to said main body block; and a pilot valve assembly block fixedly secured to said main body block by engaging said main ring with said main body block, said pilot valve assembly block having a pilot valve integrated therein as one body for detecting reciprocating motion of said center rod; and a sub ring engaged via a thread with a threaded section of said pilot valve assembly block, wherein said main ring includes an internal flange that projects radially inward from the axially extending inner annular portion of said main ring, and said internal flange is clamped between said sub ring and a radially outwardly projecting portion of said pilot valve assembly block such that, by threading said sub ring onto said pilot valve assembly block, an axial force is applied by said sub ring to said main ring to prevent rotational movement thereof.