# US 2019/0170167 A1 · Hydraulic fluid device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0170167 A1 - Document ID: US20190170167A1 - Status: Published application - Kind: A1 - Application number: 16/324,432 - Filed: 2017-06-27 - Published: 2019-06-06 - Earliest claimed: 2016-08-10 - Assignees: SMC Corporation - Applicants: Smc Corporation - Inventors: Tsukasa ODAKA - Web page: https://patentgrep.com/patent/US20190170167A1 ## CPC - F15B 15/14: of the straight-cylinder type - F15B 15/1452: {Piston sealings} - F15B 13/0402: {for linearly sliding valves, e.g. spool valves} - F15B 15/1447: {Pistons; Piston to piston rod assemblies} - F15B 15/28: Means for indicating the position, e.g. end of stroke - F15B 15/2807: {Position switches, i.e. means for sensing of discrete positions only, e.g. limit switches} - F15B 15/2861: {using magnetic means} - F16J 1/008: {with sealing lips} - F15B 15/2892: {characterised by the attachment means} - F15B 2013/0409: {Position sensing or feedback of the valve member} - F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR - F16J: PISTONS {(specially adapted for dampers F16F9/32)}; CYLINDERS; SEALINGS ## Abstract A hydraulic fluid cylinder is equipped with a cylinder tube, a piston unit, and a piston rod. The piston unit has a piston body provided with a gasket-mounting groove. A gasket member is mounted in the gasket mounting groove. The gasket member has a gasket body provided with a magnet-mounting groove exhibiting groove depth in the axial direction of the piston unit, and also has a magnet mounted in the magnet-mounting groove. ## Claims ### Claim 1 A fluid pressure device comprising: a body having a slide hole inside the body; a piston unit movable in an axial direction inside the slide hole; and a piston rod protruding from the piston unit in the axial direction; wherein the piston unit includes a packing member and a piston body including a packing mounting groove in which the packing member is mounted; and wherein the packing member includes: a packing body comprising an elastic member and circumferentially extending over an entire circumference of the piston body in a circumferential direction of the piston body, the packing body being provided with a magnet mounting groove having a depth in the axial direction of the piston unit; and a magnet mounted in the magnet mounting groove. ### Claim 2 (depends on 1) The fluid pressure device according to claim 1, wherein the magnet mounting groove is formed in an area of the packing body that is not subjected to elastic compressive deformation when the packing body receives compressive load at a position between the piston body and an inner surface of the slide hole. ### Claim 3 (depends on 1) The fluid pressure device according to claim 1, further comprising: a rotation restricting mechanism configured to restrict rotation of the piston unit relative to the body; wherein the magnet is disposed in the packing body over a range less than an entire circumference of the packing body in a circumferential direction of the packing body. ### Claim 4 (depends on 3) The fluid pressure device according to claim 3, wherein the rotation restricting mechanism is a rotation prevention rod extending in the axial direction of the piston unit inside the body and inserted into the piston body. ### Claim 5 (depends on 3) The fluid pressure device according to claim 3, wherein one of the piston body and the packing member is provided with an anti-rotation protrusion protruding in the axial direction, another of the piston body and the packing member is provided with an anti-rotation recess recessed in the axial direction, and the anti-rotation protrusion is inserted into the anti-rotation recess. ### Claim 6 (depends on 3) The fluid pressure device according to claim 3, wherein the piston rod is rotatable relative to the piston body. ### Claim 7 (depends on 1) The fluid pressure device according to claim 1, wherein the magnet mounting groove and the magnet each have a ring shape circumferentially extending over an entire circumference of the packing body in a circumferential direction of the packing body. ### Claim 8 (depends on 1) The fluid pressure device according to claim 1, wherein: the piston body includes a plurality of members including a first piston member and a second piston member; and a combination of at least two members of the plurality of members defines the packing mounting groove. ### Claim 9 (depends on 8) The fluid pressure device according to claim 8, wherein one or both of the first piston member and the second piston member are provided with a lightening portion having a depth in the axial direction. ### Claim 10 (depends on 9) The fluid pressure device according to claim 9, wherein the lightening portion has a through-hole passing through only one of the first piston member and the second piston member in the axial direction. ### Claim 11 (depends on 9) The fluid pressure device according to claim 9, wherein the lightening portion comprises a plurality of lightening portions disposed at intervals in a circumferential direction. ### Claim 12 (depends on 8) The fluid pressure device according to claim 8, wherein the first piston member and the second piston member are castings. ### Claim 13 (depends on 1) The fluid pressure device according to claim 1, wherein the fluid pressure device is configured as a fluid pressure cylinder, a valve device, a length-measurement cylinder, a sliding table, or a chuck device.