# US 2015/0148751 A1 · Piston member for syringe > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2015/0148751 A1 - Document ID: US20150148751A1 - Status: Published application - Kind: A1 - Application number: 14/406,436 - Filed: 2013-03-04 - Published: 2015-05-28 - Earliest claimed: 2013-03-04 - Assignees: Coki Engineering Inc. - Applicants: Coki Engineering Inc. - Inventors: Akira Yotsutsuji - Web page: https://patentgrep.com/patent/US20150148751A1 ## CPC - A61M 5/31513: {Piston constructions to improve sealing or sliding} - A61M 5/284: {comprising means for injection of two or more media, e.g. by mixing} - A61M 2005/3104: {Caps for syringes without needle} - A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)} ## Abstract [Objective]: To provide a low-cost piston member for syringes, with sufficiently satisfying slidability and sealing performance such as non-leakage and vapor impermeability, without size limitation, from small to large diameters. [Solution]: A piston member 10, such as a gasket 10a or a middle piston 10b, is formed by cut-processing a PTFE block and is press-fitted in a syringe barrel 1 to be slidably used. Protruded rims 13 are formed at least in a circumferential direction of perimeter of a slide-contact surface 11a adjacent to a liquid contact surface 14 of a drug solution 30, in a slide-contact surface 11 of the piston member 10, slidingly making contact with an inner circumferential surface 2 of the syringe barrel 1. After cut-processing, pitch P of the protruded rims 13 is 50 μm or smaller, and press-fit margin T to the syringe barrel 1 is 10 to 150 μm. ## Claims ### Claim 1 A piston member formed by cut-processing a PTFE block and pressed and fitted in a syringe barrel to be used in a slidable manner, the piston member comprising protruded rims formed at least in a circumferential direction of a whole circumference of a slide-contact surface that is adjacent to a liquid contact surface in contact with a drug solution, and that is a part of a slide-contact surface of the piston member, slidingly making contact with an inner circumferential surface of the syringe barrel, wherein after the cut-processing, a pitch of the protruded rims is not larger than 50 J..lm, and a press-fit margin of the piston member with respect to the syringe barrel is 10 to 150 J.llll. ### Claim 2 (depends on 1) The piston member according to claim 1, a maximum height roughness after the cut-processing is set to be not larger than 6 J..Lm. ### Claim 3 (depends on 1) The piston member according to claim 1, wherein the protruded rims are helically formed. ### Claim 4 (depends on 1) The piston member according to claim 1, wherein the protruded rims are formed in a ring shape. ### Claim 5 (depends on 1) The piston member according to claim 1, wherein a width of the slide-contact surface adjacent to the liquid contact surface of the piston member is 0.5 mm to 3 mm. ### Claim 6 (depends on 1) The piston member according to claim 1, wherein the slide-contact surface adjacent to the liquid contact surface of the piston member is formed to be gradually smaller from a side of the liquid contact surface to a side of a liquid non-contact surface opposite thereto. ### Claim 7 (depends on 1) The piston member according to claim 1, wherein the slide-contact surface adjacent to the liquid contact surface of the piston member is formed to be small, in a concaved arc shape, between a side of the liquid contact surface and a side of a liquid non-contact surface opposite thereto. ### Claim 8 (depends on 1) The piston member according to claim 1, wherein the slide-contact surface adjacent to the liquid contact surface of the piston member is formed to be small, in concaved arc shapes, between a central portion of the liquid contact surface and a liquid non-contact surface opposite thereto, and both of the surfaces. ### Claim 9 (depends on 1) The piston member according to claim 1, wherein a diameter of the piston member at the slide-contact surface adjacent to the liquid contact surface is set to be larger on a side of the liquid contact surface than a side of a liquid non-contact surface opposite thereto. ### Claim 10 (depends on 1) The piston member according to claim 1, wherein at least three of the protruded rims counted from the liquid contact surface have the pitch, the maximum height roughness, and the press-fit margin set forth in claim 1, and the protruded rims subsequent to a fourth rim have at least one of the pitch, the maximum height roughness, and the press-fit margin larger than that of the three protruded rims on the side of the liquid contact surface. ### Claim 11 (depends on 1) The piston member according to claim 1, wherein at least three of the protruded rims counted from the liquid contact surface have a ring shape, and the protruded rims subsequent to a fourth rim are helical. ### Claim 12 (depends on 1) The piston member according to claim 1, wherein the whole piston member is formed from PTFE. ### Claim 13 (depends on 1) The piston member according to claim 1, wherein the piston member is formed by cut-processing at least a PTFE portion of a composite block in which only an outer circumferential surface of a drug solution-resistant resin material is covered with a PTFE cylindrical material. ### Claim 14 (depends on 1) The piston member according to claim 1, wherein a cavity is formed inside the slide-contact surface of the piston member.