A reciprocating fluid transfer pump in which a pilot valve assembly block
can be mounted to a main body block in a simple, easy and reliable
manner. In the reciprocating fluid transfer pump, a fluid, which has been
suctioned into a fluid delivering chamber (19), is discharged therefrom
by causing an expanding and contracting action of a barrier membrane (6)
which is attached to either end of a center rod (5). The center rod is
capable of reciprocating with respect to the main body block (2). A
peripheral portion of the barrier membrane (6) is clamped fixedly to the
main body block (2) via a main ring (30), and a pilot valve assembly
block (17) having an integrated pilot valve (16) for detecting the
reciprocating motion of the center rod (5) is pressed against and thus
fixedly secured to the main ring (30) via a sub ring (34).