Patent ID: 6860727

Claim:
An air motor of a hydraulic pump, comprising front and rear castings disposed in a front portion and a rear portion of a housing and oil reservoir respectively; a tube joined to the front and rear castings at opposing ends thereof, the tube having a central hole; a piston assembly having a piston movably disposed in the central hole of the tube, the piston assembly having a pump piston connected to the piston and passed into a bore of a pump member fixedly joined to the front casting, the piston being spring biased toward the rear casting thereof; the rear casting being connected to an air source so that pressured air of the air source can travel into the tube via the rear casting to effect reciprocating movement of the pump piston within the bore of the pump member, and being characterized by a ball valve member, and a spring loaded check valve connected to respective holes of the front casting, the ball valve member being joined to the front casting to be in one-way communication with oil containing portion of the housing and oil reservoir such that a return stroke of the pump piston effects flow of oil of the housing and oil reservoir into the bore via the ball valve member; the spring loaded check valve being disposed in one-way communication with the bore of the pump member such that a forward stroke of the pump piston effects flow of oil contained in the bore of the pump member into an external oil supplying connector, which is joined to the spring loaded check valve and a jack at two ends, via the spring loaded check valve; the piston assembly including a pilot operated guided poppet valve, the pilot operated guided poppet valve being movable relative to the piston to equalize pressure on opposing sides of the piston to effect a return stroke of the piston near an end of a forward stroke of the piston so that the pressured air can effect reciprocating movement of the pump piston within the bore of the pump member, the rear casting having one end of a spring extending therefrom for closing the pilot operated guided poppet valve to initiate another forward stroke.