Hydraulic pump assembly associated with accumulator

A hydraulic pump assembly for use in combination with an accumulator for supplying hydraulic fluid under pressure into the accumulator through an inlet check valve associated thereto, comprising:

• a pump housing provided with an inlet port connected to a fluid reservoir and an outlet port connected to said accumulator by means of a high pressure hose provided therein with said inlet check valve;
• a single cam shaft rotatably mounted within said pump housing to be driven by a power source;
• a first plunger pump assembly of large displacement capacity including a first cylinder provided within said pump housing perpendicularly to said cam shaft, a first plunger axially movable disposed within said first cylinder to be reciprocated by engagement with said cam shaft, and a first suction check valve arranged to cooperate with said first plunger for permitting therethrough flow of hydraulic fluid from said inlet port toward said first plunger;
• a second plunger pump assembly of small displacement capacity including a second cylinder provided within said pump housing perpendicularly to said cam shaft and opposed to said first cylinder, a second plunger axially slidably disposed within said second cylinder to be reciprocated by engagement with said cam shaft, a second suction check valve arranged to cooperate with said second plunger for permitting therethrough the flow of pressurized hydraulic fluid from said first plunger pump assembly toward said second plunger, and an exhaust check valve arranged to cooperate with said second plunger for discharging therethrough the hydraulic fluid pressurized by said second plunger toward said outlet port;
• and
• return passage means for permitting hydraulic fluid under high pressure flowing therethrough from a chamber between said exhaust check valve and said inlet check valve toward said inlet port;
• wherein said return passage means includes a passage formed in said second cylinder and communicated at one end thereof with said outlet port and at the other end thereof with a cylindrical slight clearance between the inner circumference of said second cylinder and the outer circumference of said second plunger, and a chamber formed in surrounding relationship with said cam shaft to provide fluid communication between said cylindrical slight clearance and said inlet port.

A hydraulic pump assembly for use in combination with an accumulator for supplying hydraulic fluid under pressure into the accumulator through an inlet check valve associated thereto, comprising:

• a pump housing provided with an inlet port for connection to a fluid reservoir and an inlet port for connection to a fluid reservoir and an outlet port for connection to said accumulator through said inlet check valve;
• a single cam shaft rotatably mounted within said pump housing to be driven by a power source;
• a first plunger pump assembly of large displacement capacity including a first cylinder provided within said pump housing perpendicularly to said cam shaft, a first plunger axially movably disposed within said first cylinder for reciprocation by engagement with said cam shaft, a first suction check valve arranged to cooperate with said first plunger for permitting therethrough flow of hydraulic fluid from said inlet port toward said first plunger, a relief valve associated with said first suction check valve to release excessive hydraulic pressure from a pump chamber between said first suction check valve and said first plunger into a chamber in communication with said inlet port, and a first exhaust check valve arranged to cooperate with said first plunger for discharging therethrough the hydraulic fluid pressurized by said first plunger;
• and
• a second plunger pump assembly of small displacement capacity including a second cylinder provided within said pump housing perpendicularly to said cam shaft and opposed to said first cylinder, a second plunger axially slidably disposed within said second cylinder for reciprocation by engagement with said cam shaft, a second suction check valve arranged in communication with said first exhaust check valve to cooperate with said second plunger for permitting therethrough the flow of pressurized hydraulic fluid from said first exhaust check valve toward said second plunger, and a second exhaust check valve arranged to cooperate with said second plunger for discharging therethrough the hydraulic fluid pressurized by said second plunger toward said outlet port;
• wherein said first suction check valve comprises a cylindrical retainer fixedly coupled with said first cylinder, an axially movable valve plate disposed within said cylindrical retainer movable in response to reciprocation of said plunger, an annular valve seat fixedly coupled with said cylindrical retainer, a cylindrical valve body axially slidably coupled with said annular valve seat, and resilient means for biasing said valve body toward said valve plate, said cylindrical valve body having an annular seat portion cooperable with a flat surface of said valve plate, wherein said relief valve comprises an annular flange of said valve body cooperable with said valve seat, and wherein the flat surface of said valve plat is adapted to be brought into engagement with the annular seat portion of said valve body only by the hydraulic fluid pressurized by said first plunger.