A hydraulic pump for injecting a predetermined amount of a fluid product into
a
line carrying fluid that is subject to cyclic pressure. A chamber has a rigid outer
wall adapted to be fluidly coupled to the line. A flexible bladder positioned within
the chamber forms a cavity between the bladder and the outer wall of the chamber.
The outer wall of the chamber has a first opening and a second opening, both the
first opening and the second opening being in fluid communication with the cavity,
the first opening adapted to be fluidly coupled to the fluid product, the second
opening adapted to be fluidly coupled to the line. The flexible bladder is responsive
to fluid pressure in the chamber by moving toward the outer wall of the chamber
under a relatively high pressure from the fluid from the line and rebounding to
a predetermined position away from the outer wall of the chamber when under a relatively
low pressure from the fluid from the line. A first one-way check valve is in fluid
communication between the fluid product and the first opening allowing the fluid
product to pass only into the cavity from outside of the chamber. A second one-way
check valve in fluid communication between the second opening and the line allowing
the fluid product to pass only from the cavity to the line.
