# US 11,993,921 B2 · Cylinder, hydraulic system, construction machine and procedure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,993,921 B2 - Document ID: US11993921B2 - Status: Granted - Kind: B2 - Application number: 17/619,689 - Filed: 2020-06-17 - Published: 2022-09-29 - Granted: 2024-05-28 - Earliest claimed: 2019-06-17 - Assignees: Elmaco AS - Applicants: Elmaco AS - Inventors: Per Olav Haughom - Web page: https://patentgrep.com/patent/US11993921B2 ## CPC - E02F 9/2271: {Actuators and supports therefor and protection therefor} - E02F 9/0883: {Tanks, e.g. oil tank, urea tank, fuel tank (for vehicles in general B60K15/00)} - E02F 9/2091: {Control of energy storage means for electrical energy, e.g. battery or capacitors (energy recovery arrangements in hydraulic or pneumatic drives E02F9/2217)} - E02F 9/2203: {Arrangements for controlling the attitude of actuators, e.g. speed, floating function} - E02F 9/2217: {with energy recovery arrangements, e.g. using accumulators, flywheels} - E02F 9/2235: {including an electronic controller} - E02F 9/2246: {Control of prime movers, e.g. depending on the hydraulic load of work tools} - E02F 9/2289: {Closed circuit} - F15B 11/036: by means of servomotors having a plurality of working chambers - F15B 13/027: {Check valves} - F15B 15/1428: {Cylinders (F15B15/1438 takes precedence)} - F15B 15/1447: {Pistons; Piston to piston rod assemblies} - F15B 15/1466: {Hollow piston sliding over a stationary rod inside the cylinder} - F15B 2211/7055: having more than two chambers - E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00) - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR ## Abstract A cylinder has a piston part, a cylinder part, and a pipe section connected to the piston or cylinder parts. A portion of the pipe section encloses a pressure compartment which receives a fluid to apply a pressure on a pressure surface so the piston part is displaced in a first stroke direction. A first return pressure compartment receives a fluid to apply a pressure on a first return pressure surface so that the piston part is displaced in a second return stroke direction. The first return pressure compartment is positioned on the outside of the pipe section, and the area of the first return pressure surface is substantially equal to the area of the return pressure surface so that a volume-neutral operation of the cylinder is provided. Also described is a hydraulic system, an excavator comprising the cylinder and a procedure for operation of the cylinder. ## Claims ### Claim 1 A cylinder comprising: a piston part; a cylinder part arranged for axial movement relative to the piston part, the piston part and/or the cylinder part comprising a pipe section; one or more pressure compartments arranged to receive a fluid to apply a pressure on one or more pressure surfaces for displacement of the piston part axially in a first stroke direction, wherein a portion of the pipe section encloses the at least one of said pressure compartments and/or pressure surfaces in a radial inner region of the cylinder; and return pressure compartments arranged to receive a fluid to apply a pressure on return pressure surfaces for displacement of the piston part axially in a second, return stroke direction which is opposite to the stroke direction, the return pressure compartments comprising at least one first return pressure compartment and at least one second return pressure compartment, wherein the at least one first return pressure compartment and/or at least one first return pressure surface is defined in a radial outer region of the cylinder; wherein the pipe section further encloses said at least one second return pressure compartment and/or at least one second return pressure surface; wherein the pipe section permits fluid communication between the first return pressure compartment and the second return pressure compartment; wherein the one or more pressure compartments and the return pressure compartments are configured for volume neutral operation of the cylinder, the return pressure surfaces having in total an area, when projected onto a plane perpendicular to the axial direction, which is equal to the total area of the one or more pressure surfaces. ### Claim 2 (depends on 1) The cylinder according to claim 1, wherein the pipe section comprises at least one port arranged to provide fluid communication between the first return pressure compartment and the second return pressure compartment. ### Claim 3 (depends on 1) The cylinder according to claim 1, wherein the at least one first return pressure compartment and/or return pressure surfaces in the radial outer area of the cylinder is positioned on the outside of the pipe section. ### Claim 4 (depends on 1) The cylinder according to claim 1, wherein the cylinder part or the piston part has a first end which comprises a guide for the other of the cylinder part and the piston part and an opposite, second end which is closed for the other of the cylinder part and the piston part. ### Claim 5 (depends on 1) The cylinder according to claim 1, further comprising at least one third return pressure compartment and/or at least one third return pressure surface. ### Claim 6 A cylinder comprising: a piston part; a cylinder part arranged for axial movement relative to the piston part, the piston part and/or the cylinder part comprising a pipe section; one or more pressure compartments arranged to receive a fluid to apply a pressure on one or more pressure surfaces for displacement of the piston part in a first stroke direction, wherein a portion of the pipe section encloses the at least one of said pressure compartments and/or pressure surfaces in a radial inner region of the cylinder; and return pressure compartments arranged to receive a fluid to apply a pressure on return pressure surfaces for displacement of the piston part in a second stroke direction, the return pressure compartments comprising at least one first return pressure compartment, at least one second return pressure compartment, and at least one third return pressure compartment, wherein the at least one first return pressure compartment and/or at least one first return pressure surface is defined in a radial outer region of the cylinder, and further comprising at least one third return pressure surface; wherein the pipe section further encloses said at least one second return pressure compartment and/or at least one second return pressure surface; and wherein the pipe section permits fluid communication between the first return pressure compartment and the second return pressure compartment; and a cylinder pipe between the first return pressure compartment and the third return pressure compartment, and the cylinder pipe comprises at least one port arranged to provide fluid communication between the first return pressure compartment and the third return pressure compartment. ### Claim 7 (depends on 6) The cylinder according to claim 6, wherein the third return pressure compartment is defined in the radial outer region of the cylinder, and the second return fluid compartment is in fluid communication with the third return fluid compartment. ### Claim 8 A cylinder comprising: a piston part; a cylinder part which in a first end comprises a guide for the piston part and which in an opposite, second end is closed for the piston part; one or more pressure compartments arranged to receive a fluid to apply a pressure on one or more pressure surfaces for displacement of the piston part axially in a first, stroke direction; and return pressure compartments arranged to receive a fluid to apply a pressure on return pressure surfaces for displacement of the piston part axially in a second, return stroke direction which is opposite to the stroke direction, the return pressure compartments comprising at least one first return pressure compartment and at least one second return pressure compartment arranged in fluid communication through a pipe section of the cylinder part or the piston part; the one or more pressure compartments and the return pressure compartments being configured for volume-neutral operation of the cylinder, the return pressure surfaces having in total an area, when projected onto a plane perpendicular to the axial direction, which is equal to the total area of the one or more pressure surfaces. ### Claim 9 A cylinder comprising: a piston part; a cylinder part arranged for axial movement relative to the piston part; one or more pressure compartments arranged to receive a fluid to apply a pressure on one or more pressure surfaces for displacement of the piston part axially in a first, stroke direction; and return pressure compartments arranged to receive a fluid to apply a pressure on return pressure surfaces for displacement of the piston part axially in a second, return stroke direction; a pipe section which is connected to the piston part or the cylinder part, wherein a portion of the pipe section encloses the at least one of said pressure compartments which in an axial direction is delimited by the at least one of said pressure surfaces; the return pressure compartments comprising at least one first return pressure compartment and at least one second return pressure compartment arranged in fluid communication, at least said first return pressure compartments and/or the return pressure surfaces being positioned on the outside of the pipe section; wherein the one or more pressure compartments and the return pressure compartments are configured for volume neutral operation of the cylinder, the return pressure surfaces having in total an area, when projected onto a plane perpendicular to the axial direction, which is equal to the total area of the one or more pressure surfaces. ### Claim 10 (depends on 9) A hydraulic system comprising a hydraulic circuit which comprises at least one cylinder according to claim 9. ### Claim 11 (depends on 10) The hydraulic system according to claim 10, wherein the hydraulic circuit is closed. ### Claim 12 (depends on 11) The hydraulic system according to claim 11, wherein the closed circuit comprises a top-up pump and an oil tank arranged to supply top-up oil to the closed circuit. ### Claim 13 (depends on 12) The hydraulic system according to claim 12, wherein the oil tank is arranged to supply the top-up oil to the circuit through at least one check valve. ### Claim 14 A hydraulic system comprising: a hydraulic circuit which comprises at least one cylinder, the cylinder comprising: a piston part; a cylinder part arranged for axial movement relative to the piston part; one or more pressure compartments arranged to receive a fluid to apply a pressure on one or more pressure surfaces for displacement of the piston part in a first stroke direction; return pressure compartments arranged to receive a fluid to apply a pressure on return pressure surfaces for displacement of the piston part in a second stroke direction; and a pipe section which is connected to the piston part or the cylinder part, wherein a portion of the pipe section encloses the at least one of said pressure compartments which in an axial direction is delimited by the at least one of said pressure surfaces; the return pressure compartments comprising at least one first return pressure compartment and at least one second return pressure compartment arranged in fluid communication, at least said first return pressure compartments and/or the return pressure surfaces being positioned on the outside of the pipe section; and wherein the cylinder is connected to a fluid pump configured to being driven with a rotation direction which is switchable between a first rotation direction and a second rotation direction, wherein in the first rotation direction the pump operates to supply fluid to the cylinder's pressure compartment, and in the second rotation direction the pump operates to supply fluid to the cylinder's return pressure compartment. ### Claim 15 (depends on 14) The hydraulic system according to claim 14, wherein the fluid pump is connected to an electric motor, and the electric motor is connected to a frequency converter arranged to change the rotation direction and the RPM of the electric motor and/or the pump. ### Claim 16 (depends on 9) A construction machine comprising at least one cylinder according to claim 9. ### Claim 17 (depends on 10) A construction machine comprising a hydraulic system according to claim 10. ### Claim 18 (depends on 10) A method of operating a cylinder according to claim 10, wherein the procedure comprises the step of pumping a fluid to the cylinder. ### Claim 19 (depends on 18) The method according to claim 18, wherein the cylinder is connected to a fluid motor which is connected to an electric motor which is connected to a frequency converter; and the procedure further comprises the step of giving a control signal to the frequency converter so that the electric motor and the pump rotate in a desired direction and at a desired speed to thereby guide the fluid from the pump to the cylinder. ### Claim 20 (depends on 19) The method according to claim 19, wherein the procedure further comprises the step of generating electric energy by allowing the cylinder to, when loaded, guide fluid into the pump so that the electric motor which is connected to the pump is subjected to a rotation, and thereby generate energy.