Patent ID: 6213730
Filing Date: 2001-04-10
Classification: F04B,F04C

Abstract:
An apparatus for variably controlling a flow rate of fluid discharged from a positive-displacement pump, comprising:a discharge passage communicating with the pump;a variable flow control valve operative to vary a flow of fluid passing through the discharge passage, said variable flow control valve being disposed within the discharge passage; anda flow control circuit cooperative with the discharge passage to permit a predetermined flow of the fluid, said flow control circuit including a drain valve actuatable in response to a difference between pressures upstream and downstream of the variable flow control valve;said variable flow control valve including a spool bore communicating with the discharge side of the pump, a spool moveably disposed in the spool bore and having positions where different opening areas of the discharge passage are defined, and a spring biasing the spool in such one direction as to increase the opening area of the discharge passage, said spool being displaceable between the positions by a biasing force of the spring and a force variably acting on the spool in response to the flow rate of fluid discharged from the pump;wherein said spring includes a first spring and a second spring arranged in series, and wherein the variable flow control valve includes a displacement stop restricting displacement of the first spring in a compression direction opposite to the one direction, said displacement stop interconnecting the first and second springs.