Patent ID: 7588431

Claim:
A pump/motor apparatus comprising: a hollow housing having at least one inlet port formed therein for fluid into said housing and at least one outlet port formed therein for fluid out of said housing; a first mandrel disposed in said housing and having a first flange; a shaft rotatably mounted to said housing having an end extending into said housing; a second mandrel disposed in said housing and having a second flange; an external gear disposed on said first mandrel, said external gear having a center aperture with a plurality of teeth formed on a wall of said aperture; a internal gear received on said shaft end in said housing, said internal gear having a plurality of teeth formed on an exterior surface thereof, said internal gear being disposed in said aperture of said external gear with said teeth of said internal gear meshing with said teeth of said external gear, said internal gear being axially moveable along said shaft relative to said external gear, said flanges extending into said aperture and cooperating with said gears to form a variable displacement inlet chamber and a variable displacement discharge chamber; a rotatable first seal rotatably disposed in said first mandrel and engaging with a portion of said internal gear; and a rotatable second seal receiving said second mandrel and engaging with a portion of said wall of said aperture of said external gear whereby when pressured liquid is supplied to said at least one inlet port, the pressured fluid rotates said internal and external gears causing said shaft to rotate for operation as a motor, and when said shaft is rotated, said internal gear rotates said external gear for operation as a pump causing fluid to flow from said at least one inlet port to said at least one outlet port.