# US 11,905,938 B2 · Piston hydraulic device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,905,938 B2 - Document ID: US11905938B2 - Status: Granted - Kind: B2 - Application number: 17/047,951 - Filed: 2019-04-09 - Published: 2021-05-27 - Granted: 2024-02-20 - Earliest claimed: 2018-04-19 - Assignees: Dana Motion Systems Italia S.R.L. - Applicants: Dana Motion Systems Italia S.R.L. - Inventors: Alessandro Sassi; Fabio Natali; Federica Franzoni - Web page: https://patentgrep.com/patent/US11905938B2 ## CPC - F04B 1/22: having two or more sets of cylinders or pistons - F04B 1/328: by changing the inclination of the axis of the cylinder barrel relative to the swash plate - F04B 49/22: by means of valves (F04B49/03 takes precedence) - F04B: POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS (machines for liquids, or pumps, of rotary-piston or oscillating-piston type F04C; non-positive-displacement pumps F04D; pumping of fluid by direct contact of another fluid or by using inertia of fluid to be pumped F04F) ## Abstract A piston hydraulic device comprises a cylinder block having a plurality of cylinder assemblies and is rotatable about a first rotation axis. Each cylinder assembly comprises a cylinder and a piston. A port plate has a first port and a second port that are angularly spaced relative to the first rotation axis. A plurality of first conduits connect respective cylinders alternately to the first port or the second port. At least one second conduit is connected to a fluid reservoir. At least one directional control valve is positioned in the first conduit and fluidly connects to the second conduit. The at least one directional control valve connects the cylinder to the port plate in a first position and to the fluid reservoir in a second position. A controller is operatively associated with the directional control valve for switching between the first and the second positions. ## Claims ### Claim 1 A piston hydraulic device, comprising: a cylinder block having a plurality of cylinder assemblies, the cylinder block being rotatable about a first rotation axis wherein each cylinder assembly comprises a cylinder and a piston; a port plate having a first port and a second port, the first and second ports being angularly spaced relative to the first rotation axis; and a plurality of first conduits for connecting respective cylinder alternately to the first port or the second port relative to an angular position of the cylinder assembly about the first rotation axis, wherein, the axial piston hydraulic device further comprises: at least one second conduit connected to a fluid reservoir; at least one directional control valve positioned in at least one of the first conduits and fluidly connected to the second conduit wherein the at least one directional control valve connects the cylinder to the port plate in a first position and to the fluid reservoir in a second position; wherein a portion of a total number of cylinders in the cylinder block is connected directly to a respective first conduit and wherein the cylinders that are connected directly to the respective first conduit are not connected to a directional control valve of a plurality of directional control valves including the at least one directional control valve; and a controller operatively associated with the directional control valve for switching between the first and the second positions. ### Claim 2 (depends on 1) The piston hydraulic device of claim 1, wherein the at least one directional control valve connects the cylinder to the first port or the second port in the first position. ### Claim 3 (depends on 1) The piston hydraulic device of claim 1, wherein the fluid reservoir is a tank. ### Claim 4 (depends on 1) The piston hydraulic device of claim 1, wherein the fluid reservoir is an accumulator. ### Claim 5 (depends on 4) The piston hydraulic device of claim 4, wherein the at least one directional control valve connects the cylinder to the port plate and the accumulator in the second position. ### Claim 6 (depends on 5) The piston hydraulic device of claim 5, wherein a first check valve is integrated in the directional control valve, the first check valve being interposed between the cylinder and the accumulator wherein the first check valve is configured to obstruct fluid flow from the accumulator to the cylinder. ### Claim 7 (depends on 5) The piston hydraulic device of claim 5, wherein a second check valve is integrated in the directional control valve, the second check valve being interposed between the cylinder and the port plate wherein the second check valve is configured to obstruct fluid flow from the cylinder to the port plate. ### Claim 8 (depends on 1) The piston hydraulic device of claim 1, wherein the device is a bent axis hydraulic device. ### Claim 9 (depends on 1) The piston hydraulic device of claim 1, wherein the device is a swash plate type hydraulic device. ### Claim 10 (depends on 1) The piston hydraulic device of claim 1, further comprising a housing wherein the at least one directional control valve is coupled to the housing. ### Claim 11 (depends on 1) The piston hydraulic device of claim 1, wherein the at least one of the first conduits extends from the cylinder block through the housing. ### Claim 12 (depends on 1) The piston hydraulic device of claim 1, wherein the second conduit extends through the housing. ### Claim 13 (depends on 1) The piston hydraulic device of claim 1, wherein the device is an axial piston hydraulic device. ### Claim 14 (depends on 1) The piston hydraulic device of claim 1, wherein the at least one directional control valve is interposed between the cylinder and the port plate relative to the at least one of the first conduits. ### Claim 15 (depends on 1) The piston hydraulic device of claim 1, wherein a portion of a total number of cylinders in the cylinder block are connected to a respective directional control valve.