A piston pump configured to suction and discharge a working fluid includes a plurality of pistons, a cylinder block accommodating the pistons, a shaft combined with the cylinder block, swash plate configured to reciprocate the pistons in accordance with rotation of the cylinder block, a casing accommodating the cylinder block, and a valve plate placed between the cylinder block and the casing. The valve plate has a suction port providing communication between capacity chambers and a suction passage, and the suction port is a cutout part formed by cutting out an outer edge of the valve plate.

A piston retainer plate includes a first end, a second end opposite the first end, a piston pocket extending from the first end to the second end, a straight annular surface extending from the first end, an angled annular surface extending at an angle from the second end, a curved annular surface connected to the straight annular surface and the angled annular surface, the curved annular surface being between the straight annular surface and the angled annular surface, and a curved vent within the curved annular surface. The straight annular surface, the angled annular surface, and the curved annular surface define the piston pocket.

A piston retainer plate includes a first end, a second end opposite the first end, a piston pocket extending from the first end to the second end, a straight annular surface extending from the first end, an angled annular surface extending at an angle from the second end, a curved annular surface connected to the straight annular surface and the angled annular surface, the curved annular surface being between the straight annular surface and the angled annular surface, and a curved vent within the curved annular surface. The straight annular surface, the angled annular surface, and the curved annular surface define the piston pocket.

An axial variable displacement piston pump includes a drive shaft disposed on an axis, a piston barrel having a plurality of pistons disposed about and rotationally coupled to the drive shaft, a swash plate disposed about and rotationally coupled to the drive shaft, and a retention cage connected to the swash plate between the piston barrel and the swash plate. The swash plate and the piston barrel are configured to be simultaneously driven by the drive shaft and the swash plate is configured to tilt relative to the axis. The retention cage is configured to retain the plurality of pistons relative to the swash plate with rotation.

An axial variable displacement piston pump includes a drive shaft disposed on an axis, a piston barrel having a plurality of pistons disposed about and rotationally coupled to the drive shaft, a swash plate disposed about and rotationally coupled to the drive shaft, and a retention cage connected to the swash plate between the piston barrel and the swash plate. The swash plate and the piston barrel are configured to be simultaneously driven by the drive shaft and the swash plate is configured to tilt relative to the axis. The retention cage is configured to retain the plurality of pistons relative to the swash plate with rotation.

A method of assembling a piston and shoe of a hydraulic pump. The method includes: inserting a shaft of the piston through an aperture of the shoe such that it extends through to the other side until a piston head of the piston is seated in the shoe. A piston and shoe assembly for a hydraulic pump. The assembly includes: a piston comprising a piston shaft and a piston head; and a shoe comprising an aperture, wherein the piston shaft is sized such that it can pass through the shoe aperture and the piston head is sized such that it cannot pass through the shoe aperture.

A hydraulic piston motor/pump includes a first rotor including a first cylinder, a second rotor opposing the first rotor and including a second cylinder that opposes the first cylinder, a first swashplate including a first angled face adjacent the first rotor, a second swashplate adjacent the second rotor and opposing the first swashplate. The hydraulic piston motor/pump further includes a first shoe cage including a first piston opening, a second shoe cage including a second piston opening, a piston configured to travel into and out of the first cylinder and the second cylinder, a piston shoe configured to engage the piston, the first shoe cage, and the second shoe cage, and a shaft engaging the first shoe cage and the second shoe cage. The shaft configured to rotate in response to a rotation of the first shoe cage and the second shoe cage.