Patent ID: 7543896

Claim:
A pressure regulating reservoir comprising: a housing; a first reservoir port that is provided in the housing, wherein the first reservoir port is connected to a suction conduit provided in the housing; a second reservoir port that is provided in the housing, wherein the second reservoir port is connected to a discharge conduit provided in the housing and to the first reservoir port; a valve seat that is fixed to the housing forming the first reservoir port, wherein the valve seat has a hole portion forming a passage for fluid flowing in via the suction conduit; a ball valve that is positioned inside the first reservoir port farther upstream in the fluid flow passage than the valve seat, wherein the ball valve opens and closes the hole portion by disengaging and engaging the valve seat; a shaft that is inserted in the hole portion, wherein the shaft moves in an axial direction identical the inserted direction thereof to contact the ball valve, and the shaft has a seat surface on which the ball valve sits for controlling the opening and closing of the hole portion; a piston that is integral to the shaft and slides within the second reservoir port; and a reservoir chamber that is positioned in the second reservoir port, communicates with the hole portion of the valve seat, and is defined by the piston and a wall of the housing forming the second reservoir port, wherein the shaft includes a minor diameter portion, which is received within the hole portion, and a positioning portion, which includes a positioning contact point that directly contacts a bottom surface of the valve seat, wherein the seat surface is formed on an end of the minor diameter portion, the discharge conduit is connected to a portion that is formed from an upper end surface of a wall forming the reservoir chamber in the housing, and a space is formed between the top surface of the piston and the entire surface of the upper end surface of the wall forming the reservoir chamber in the housing when the positioning contact point of the positioning portion of the shaft contacts with the bottom surface of the valve seat.