Pharmaceutical syringe piston
Inventors
LAUBACH, Jeffrey M. • Brinkhues, Jurgen • GRUEN, Heike • WORMAN, Joel • Zhao, Xia • MATTIA, Jason
Assignees
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Publication Number
US-11951289-B2
Publication Date
2024-04-09
Expiration Date
Abstract
A piston having a longitudinal axis and opposing proximal and distal axial ends is manufactured by a method including molding a partially formed piston body and then molding the piston. The partially formed piston body is molded by placing a first rubber sheet and an inert film between die plates of a first forming tool, vulcanizing the first rubber sheet and the inert film between the die plates of the first forming tool, and blanking out the partially formed piston body from the first rubber sheet and the inert film. The piston is then molded by placing the partially formed piston body into a second forming tool, placing a second rubber sheet into the second forming tool, vulcanizing the second rubber sheet and the partially formed piston body together, and blanking out the piston from the second rubber sheet at a trim edge spaced apart from the inert film.
Core Innovation
The invention relates to a pharmaceutical syringe piston in which an inert film, including a fluorinated inert film, encloses a central face portion and at least part of an annular curved portion of the piston. The inert film is prevented from extending axially along a cylindrical sealing portion of the piston, while the cylindrical sealing portion remains sized to maintain a fluid-tight seal. The piston further includes a trim edge sized to avoid barrel contact and may include stabilizing ribs separated by annular recesses.
The disclosed piston structure is manufactured using a two-stage vulcanization/molding process. A first piston body is formed by vulcanizing a first rubber sheet with an inert film between die plates, after which the first piston body is blanked out from the first rubber sheet and the inert film. The partially formed piston body is then placed into a second forming tool, followed by placing a second rubber sheet into the second forming tool and vulcanizing the second rubber sheet with the first piston body together.
After the second piston body is formed and the first piston body is joined with the second piston body to form the piston, the piston is blanked out at a trim edge. The trim edge is formed such that it is spaced apart from the inert film between the inert film and the proximal axial end, and an outer diameter of the trim edge is less than a maximum outer diameter of a rib. The inert film’s outer boundary behavior is configured to minimize contact between the inert film and the inner wall of the barrel near the fluid-tight seal.
Claims Coverage
The independent claims cover three inventive features: two-stage vulcanization with inert film enclosure and blanking; trim edge spacing and diameter relation to a rib; and syringe embodiments in which the piston maintains a fluid-tight seal while the inert film’s outer boundary minimizes contact with the barrel inner wall.
Two-stage vulcanization with inert film enclosure and blanking
A piston manufactured by placing a first rubber sheet and an inert film between die plates of a first forming tool, vulcanizing the first rubber sheet and the inert film to form a first piston body with a central face portion and an annular curved portion enclosed by the inert film, blanking out the first piston body from the first rubber sheet and the inert film, placing the first piston body into a second forming tool, placing a second rubber sheet into the second forming tool, vulcanizing the second rubber sheet and the first piston body together to form a second piston body, joining the second piston body to the first piston body to form the piston, and blanking out the piston from the second rubber sheet at a trim edge.
Trim edge spaced from inert film with outer-diameter relation to rib
The piston where the trim edge is spaced apart from the inert film between the inert film and the proximal axial end, and an outer diameter of the trim edge is less than a maximum outer diameter of the rib.
Fluid-tight seal maintained while inert film contact is minimized near seal edge
A syringe with a barrel and a piston in the barrel in which the cylindrical portion and the part of the annular curved portion maintain a fluid-tight seal with an inner wall of the barrel, and an outer boundary of the inert film is configured to be proximate to a leading-distal edge of the fluid-tight seal to minimize contact between the inert film and the inner wall of the barrel.
Inert film outer boundary positioned relative to leading-distal vs trailing-proximal edges
The syringe in which the outer boundary of the inert film is configured so as to be nearer to a leading-distal edge than to a trailing-proximal edge of the fluid-tight seal.
Coaxial and diameter/axial-extent relationships between piston portions and barrel inner wall
A syringe in which the central face portion is oriented coaxially with respect to a longitudinal axis, the first piston diameter is a maximum diameter of the central face portion and is less than an inner diameter of the inner wall of the barrel, the cylindrical portion defines first and second axial ends and a wall extending along the longitudinal axis, the wall defining a second piston diameter larger than the inner diameter of the barrel, the annular curved portion extends between the first axial end of the cylindrical portion and the central face portion, and the inert film defines an outer boundary that does not extend axially beyond the first axial end of the cylindrical portion to minimize contact between the inert film and the inner wall of the barrel, with the axial extension of the cylindrical wall greater than the axial extension of a second portion of the annular curved portion.
Across the independent claims, the inventive coverage centers on forming a piston using two-stage vulcanization with an inert film that encloses a central face portion and at least part of an annular curved portion, then trimming at a trim edge that is spaced from the inert film and dimensionally related to a rib. In the syringe claims, the piston maintains a fluid-tight seal with the barrel inner wall while configuring the inert film’s outer boundary to minimize inert film contact near the seal’s leading-distal edge, and further includes detailed coaxial, dimensional, and axial-extent relationships between piston portions and the barrel inner wall.
Stated Advantages
Maintain a fluid-tight seal with an inner wall of the barrel.
Minimize contact between the inert film and the inner wall of the barrel near the leading-distal edge of the fluid-tight seal.
Minimize contact between the inert film and the inner wall of the barrel by preventing the inert film from extending axially beyond a first axial end of the cylindrical portion.
Avoid barrel contact by sizing the trim edge to avoid barrel contact.
Documented Applications
No documented applications found
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