A piston pump has a crankshaft chamber and a plurality of passages extending from the crankshaft chamber. A crankshaft rotatably mounted in the crankshaft chamber has a rotation axis and a plurality of cams distributed along the axis. Each cam has a plurality of noses, all having a nose radius, circumferentially alternating around the axis with a plurality of heels, all having a heel radius that is less than the nose radius, and a cam material abrasion resistance. A plurality of pistons corresponding to the cams and slidably mounted in the passages each have a shaft end. A sacrificial crown removably connected to the shaft end has a cam engagement side and a crown material abrasion resistance that is less than the cam material abrasion resistance. A plurality of resiliently compressible biases bias the pistons to maintain contact between the cam engagement sides and the cams as the crankshaft rotates.

The object of the present invention is to provide a fluid rotary machine in which dead spaces can be reduced as much as possible even if the machine is enlarged by arranging rotary valves directly behind cylinder chambers. The fluid rotary machine in which first and second double-headed pistons (7, 8) intersecting within a case body (1, 2) move linearly back and forth within cylinders (16) due to the hypocycloid principle along with rotation of shafts (4a, 4b) and in which intake and exhaust cycles are repeated in chambers (22), wherein cylinder heads (17) for closing the cylinder chambers (22) are each provided with rotary valves (19) which are rotated by drive transmission from the shafts (4a, 4b) and which are provided with intake holes and discharge holes (19b) alternately communicated with the cylinder chambers (22) via communication channels (20a, 20b), and the rotary valves (19) intersect longitudinal axis of the opposing pistons (7, 8) and are capable of rotating parallel with output axil lines.

A system and method for machinery performing work with hydraulic actuators. Radial hydraulic pumps are aligned end-to-end along a common driveshaft axis to form a multi-pump assembly having a plurality of piston/cylinder units extending in a radial direction. Two or more piston/cylinder units are associated with one another to form multiple piston/cylinder groups. A plurality of control valves combines individual output flows from the two or more associated piston/cylinder units into respective common output flows for each respective piston/cylinder group. A plurality of flow control devices varies the common output flow from each respective piston/cylinder group by throttling inlet flow to the two or more associated piston/cylinder units in each respective piston/cylinder group. Each respective common output flow is directed from each respective piston/cylinder group to a hydraulic actuator on the heavy machinery to control its direction of movement.

A partial stroke pump or motor includes a piston coupled to a rotating shaft to evacuate a fluid within a cylinder during an upstroke. A latching check valve includes an actuator piston that is displaceable within a center cavity to bypass a blocking member in a bypass state. The actuator piston is driven by a latch supply line. A spool of a rotary valve selectively couples one of the low and pilot pressure supplies to the latch supply line over different timing angle ranges of the rotating shaft. Coupling of the pilot pressure to the latch supply line causes the bypass state. When operating as a pump, the bypass state causes the pressure in the cylinder to fall below the high pressure during part of the upstroke. When operating as a motor, the bypass state allows the fluid to be evacuated from the cylinder during the upstroke.

A partial stroke pump or motor includes a piston coupled to a rotating shaft to evacuate a fluid within a cylinder during an upstroke. A latching check valve includes an actuator piston that is displaceable within a center cavity to bypass a blocking member in a bypass state. The actuator piston is driven by a latch supply line. A spool of a rotary valve selectively couples one of the low and pilot pressure supplies to the latch supply line over different timing angle ranges of the rotating shaft. Coupling of the pilot pressure to the latch supply line causes the bypass state. When operating as a pump, the bypass state causes the pressure in the cylinder to fall below the high pressure during part of the upstroke. When operating as a motor, the bypass state allows the fluid to be evacuated from the cylinder during the upstroke.

A piston pump has a near-circular cam design for improved longevity and efficiency. The piston pump includes a rotatably mounted crankshaft, one or more near-circular cams, and one or more pistons. The near-circular cams include one or more cam noses and one or more cam heels. The cam noses are circumferentially alternating with the cam heels around the crankshaft axis. Each cam nose has a nose radius, each cam heel has a heel radius, and the nose radius is greater than the heel radius. Each near-circular cam has a cam stroke length that is a difference between the nose radius and the heel radius, and a cam convexity characteristic of greater than 1 and less than 1.35. Each piston is slidably mounted relative to the crankshaft between a nose position when in contact with a cam nose, and a heel position when in contact with a cam heel.

A piston pump has a near-circular cam design for improved longevity and efficiency. The piston pump includes a rotatably mounted crankshaft, one or more near-circular cams, and one or more pistons. The near-circular cams include one or more cam noses and one or more cam heels. The cam noses are circumferentially alternating with the cam heels around the crankshaft axis. Each cam nose has a nose radius, each cam heel has a heel radius, and the nose radius is greater than the heel radius. Each near-circular cam has a cam stroke length that is a difference between the nose radius and the heel radius, and a cam convexity characteristic of greater than 1 and less than 1.35. Each piston is slidably mounted relative to the crankshaft between a nose position when in contact with a cam nose, and a heel position when in contact with a cam heel.

A piston pump has a near-circular cam design for improved longevity and efficiency. The piston pump includes a rotatably mounted crankshaft, one or more near-circular cams, and one or more pistons. The near-circular cams include one or more cam noses and one or more cam heels. The cam noses are circumferentially alternating with the cam heels around the crankshaft axis. Each cam nose has a nose radius, each cam heel has a heel radius, and the nose radius is greater than the heel radius. Each near-circular cam has a cam stroke length that is a difference between the nose radius and the heel radius, and a cam convexity characteristic of greater than 1 and less than 1.35. Each piston is slidably mounted relative to the crankshaft between a nose position when in contact with a cam nose, and a heel position when in contact with a cam heel.

A piston pump has a near-circular cam design for improved longevity and efficiency. The piston pump includes a rotatably mounted crankshaft, one or more near-circular cams, and one or more pistons. The near-circular cams include one or more cam noses and one or more cam heels. The cam noses are circumferentially alternating with the cam heels around the crankshaft axis. Each cam nose has a nose radius, each cam heel has a heel radius, and the nose radius is greater than the heel radius. Each near-circular cam has a cam stroke length that is a difference between the nose radius and the heel radius, and a cam convexity characteristic of greater than 1 and less than 1.35. Each piston is slidably mounted relative to the crankshaft between a nose position when in contact with a cam nose, and a heel position when in contact with a cam heel.

A piston pump includes a pump housing with an extrusion-formed crankshaft chamber having a top chamber wall integrally extrusion-formed with at least one side chamber wall and a bottom chamber wall. Each wall has an extrusion-formed interior and exterior surface. The pump housing also includes a pumping chamber and one or more piston passages. A crankshaft is rotatably mounted within the crankshaft chamber and extends along a longitudinal crankshaft rotation axis. One or more cams are distributed along the crankshaft axis. One or more pistons are provided, each corresponding to a cam and slidably mounted in a piston passage between a nose position and a heel position. Each piston includes a piston shaft, with a first shaft end positioned in the crankshaft chamber and having a cam engagement side in contact with the corresponding cam. The crankshaft chamber extrusion direction is parallel to the crankshaft axis.