Air-driven hydraulic pump

Claim 2

In a fluid-actuated hydraulic pump including a hydraulic pump having a reciprocally operable pumping member; a fluid motor including a housing having a bore containing a reciprocal piston movable between a retracted position and an extended position and connected to said pumping member, a fluid inlet through which fluid under pressure may be admitted into the bore to drive the piston towards said extended position, spring means for driving the piston towards said retracted position, and a fluid outlet for exhausting fluid within the bore to permit the spring means to drive the piston towards said retracted position, a control valve alternately movable between a closed position wherein fluid under pressure from said inlet drives said piston toward the extended position and an open position wherein said bore is connected to said fluid outlet to permit movement of the piston to said retracted position by said spring to thereby reciprocate the pump member; and control means responsive to the piston in the retRacted position for shifting the control valve to the closed position and responsive to the piston in the extended position for shifting the control valve to the open position; the improvement which comprises: means for positively holding said control valve in said open position when said piston is moving from said open position thereof to said closed position thereof.

Claim 3

A fluid-actuated hydraulic pump according to claim 1 wherein said control valve is fluid operated in moving from said closed position to said open position and includes a surface subjectable to fluid under pressure to move said control valve from the closed position to the open position, and said positive holding means comprises means for trapping a column of fluid behind said surface while said piston is moving from the extended position to the retracted position.

Claim 4

A fluid-actuated hydraulic pump according to claim 2 wherein said trapping means comprises port means in fluid communication with said surface and closeable by said piston when said piston is between said retracted and extended positions and openable by said piston when said piston is in the retracted position.

Claim 5

A fluid-actuated hydraulic pump according to claim 3 wherein said control valve is carried by said piston in a chamber therein and said port means includes a first channel extending from said chamber to a side of the piston and a second channel in said housing opening into said bore at two spaced points therein.

Claim 6

A fluid-actuated pump comprising: a. a hydraulic pump having a reciprocally operated pumping member, b. a housing c. a bore within said housing, d. a piston mounted for reciprocal movement within said bore and connected to said pumping member, e. a fluid inlet in said housing and communicating with one end of said bore, f. a valve associated with said inlet and operable to admit fluid under pressure to said bore, g. a fluid outlet in said housing and communicating with the other end of said bore to exhaust fluid therefrom, h. a spring bearing on said piston to urge the same toward said one end of said bore, i. a valve chamber in said piston and having one end thereof ported to the side of said piston, the other end thereof ported to said bore one end, and a portion ported to said bore other end, j. a control valve member movable within said chamber for alternatively allowing fluid communication between said portion and said chamber other end in one position thereof to establish fluid communication between the two ends of the bore and to preclude fluid communication between said portion and said chamber other end in another position thereof, said valve further including a fluid-operated surface facing said chamber one end, and k. channel means associated with said bore for establishing fluid communication between said bore one end and said chamber one end when said piston approaches said bore other end.

Claim 7

A fluid-actuated pump comprising: a. a hydraulic pump having a reciprocally operated pumping member, b. a housing c. a bore within said housing, d. a piston mounted for reciprocal movement within said bore and connected to said pumping member, e. a fluid inlet in said housing and communicating with one end of said bore, f. a valve associated with said inlet and operable to admit fluid under pressure to said bore, g. a fluid outlet in said housing and communicating with the other end of said bore to exhaust fluid therefrom, h. a spring bearing on said piston to urge the same toward said one end of said bore, i. a valve chamber in said piston and having one end thereof ported to the side of said piston, the other end thereof ported to said bore one end, and a portion ported to said bore other end, j. a control valve member movable within said chamber for alternatively allowing fluid communication between said portion and said chamber other end in one position thereof to establish fluid communication between the two ends of the bore and to preclude fluid communication between said portion and said chamber other end in another position thereof, said valve further including a fluid-operated surface facing said chamber one end, and k. channel means associated with said bore for establishing fluid communication between said bore one end and said chamber one end when said piston approaches said bore other end.

Claim 8

A fluid-actuated hydraulic pump according to claim 5 wherein said channel means is arranged with respect to said bore so fluid communication is established between said chamber one end and said bore other end as said piston approaches said bore one end, and fluid communication with said chamber one end is precluded whenever said piston is not approaching either end of said bore to thereby trap a column of fluid behind said surface when said piston moves from said bore other end to positively hold said valve in a position establishing fluid communication between the ends of said bore when the piston is travelling from said bore other end toward said bore one end.

Claim 9

A fluid-actuated hydraulic pump according to claim 6 wherein said control valve is a spool valve having a reduced diameter central portion, with the spool end within said chamber one end having a larger surface area than the other spool end, said portion of said chamber having a reduced diameter larger than the reduced diameter of said spool portion, said chamber one end being ported to onE side of said piston at about the midpoint thereof, and further including sealing means on said piston sealingly engaging said piston and said bore and flanking the port of said chamber one end, said channel means opening into said bore at spaced locations therein.

Claim 10

A fluid-actuated hydraulic pump comprising: a hydraulic pump having a reciprocally operable pump member; a fluid motor including a housing having a bore containing a reciprocal piston movable between a retracted position and an extended position and connected to said pumping member; a fluid inlet through which fluid under pressure may be admitted into the bore to drive the piston towards its extended position; spring means for driving the piston towards its retracted position; a fluid outlet for exhausting fluid within the bore to permit the spring means to drive the piston towards said retracted position; a valve chamber in said piston; a fluid-actuated control valve within said chamber alternately movable between a closed position wherein fluid under pressure from said inlet drives said piston toward the extended position and an open position wherein said bore is connected to said fluid outlet to permit movement of the piston to the retracted position by said spring means to thereby reciprocate the pump member; and control means responsive to the piston in the retracted position for shifting the control valve to the closed position thereof and responsive to the piston in the extended position to shift, by fluid under pressure, the control valve to the open position thereof, said control means including a port within said piston communicating with the side thereof and with said valve chamber, and port means in said housing and opening into said bore whereby the side of said piston acts as a valve to control the application of fluid under pressure to said control valve through said port to control the position thereof.

Claim 11

A fluid-actuated hydraulic pump comprising: a hydraulic pump having a reciprocally operable pump member; a fluid motor including a housing having a bore containing a reciprocal piston movable between a retracted position and an extended position and connected to said pumping member; a fluid inlet through which fluid under pressure may be admitted into the bore to drive the piston towards its extended position; spring means for driving the piston towards its retracted position; a fluid outlet for exhausting fluid within the bore to permit the spring means to drive the piston towards said retracted position; a valve chamber in said piston; a fluid-actuated control valve within said chamber alternately movable between a closed position wherein fluid under pressure from said inlet drives said piston toward the extended position and an open position wherein said bore is connected to said fluid outlet to permit movement of the piston to the retracted position by said spring means to thereby reciprocate the pump member; and control means responsive to the piston in the retracted position for shifting the control valve to the closed position thereof and responsive to the piston in the extended position to shift, by fluid under pressure, the control valve to the open position thereof, said control means including a port within said piston communicating with the side thereof and with said valve chamber, and port means in said housing and opening into said bore whereby the side of said piston acts as a valve to control the application of fluid under pressure to said control valve through said port to control the position thereof.

Claim 12

A fluid-actuated hydraulic pump according to claim 8 further including sealing means carried by the piston and engaging the bore, said sealing means being located on said piston so as to flank both sides of the opening of said port to the side of said piston.

Claim 13

A fluid-actuated hydraulic pump according to claim 9 wherein said port means is arranged to establish fluid communication between said inlet and said valve chamber when said piston is in said extended position and between said outlet and said valve chamber when said piston is in said retracted position.