PHARMACEUTICAL SYRINGE PISTON

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.

Claims

1. A piston having a longitudinal axis and opposing proximal and distal axial ends manufactured by a method comprising: molding a partially formed piston body comprising: 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, thereby forming the partially formed piston body, the partially formed piston body having a face portion at the distal axial end, the face portion comprised of a central face portion and an annular curved portion, the central face portion and at least a part of the annular curved portion enclosed by the inert film, and blanking out the partially formed piston body from the first rubber sheet and the inert film; and molding the piston comprising: 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, thereby forming the remainder of the piston body to the proximal axial end and joining the remainder of the piston body to the partially formed piston body to form the piston, and blanking out the piston from the second rubber sheet at a trim edge, wherein the trim edge is spaced apart from the inert film.

2. The piston of claim 1, wherein the piston includes a sealing portion proximately connected to the annular curved portion, the sealing portion having an outer circumference configured to contact an inner wall of a syringe barrel.

3. The piston of claim 2, wherein the inert film does not extend along the sealing portion.

4. The piston of claim 2, wherein the piston has at least one stabilizing rib disposed between the sealing portion and the proximal axial end.

5. The piston of claim 4, wherein the sealing portion and the at least one stabilizing rib each have an outer diameter measured perpendicularly to the longitudinal axis of the piston, the outer diameter of the sealing portion being greater than the outer diameter of the at least one stabilizing rib.

6. The piston of claim 5, wherein the trim edge has an outer diameter measured perpendicularly to the longitudinal axis of the piston, the outer diameter of the at least one stabilizing rib being greater than the outer diameter of the trim edge.

7. The piston of claim 4, wherein the trim edge is proximally spaced apart from the at least one stabilizing rib.

8. The piston of claim 2, wherein the trim edge is proximally spaced apart from the sealing portion.

9. A method for manufacturing a syringe, the syringe including a barrel having an open proximal end, a piston shaft having proximal and distal ends, and a piston having a longitudinal axis and opposing proximal and distal axial ends, the method comprising: molding a partially formed piston body comprising: 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, thereby forming the partially formed piston body, the partially formed piston body having a face portion at the distal axial end, the face portion comprised of a central face portion and an annular curved portion, the central face portion and at least a part of the annular curved portion enclosed by the inert film, and blanking out the partially formed piston body from the first rubber sheet and the inert film; molding the piston comprising: 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, thereby forming the remainder of the piston body to the proximal axial end and joining the remainder of the piston body to the partially formed piston body to form the piston, and blanking out the piston from the second rubber sheet at a trim edge; engaging the distal end of the piston shaft to the proximal axial end of the piston; and receiving, in the open proximal end of the barrel, the piston engaged with the piston shaft, wherein the trim edge is spaced apart from the inert film.

10. The method of claim 9, wherein the piston includes a sealing portion proximately connected to the annular curved portion, the sealing portion having an outer circumference configured to contact an inner wall of the barrel.

11. The method of claim 10, wherein the inert film does not extend along the sealing portion.

12. The method of claim 10, wherein the piston has at least one stabilizing rib disposed between the sealing portion and the proximal axial end.

13. The method of claim 12, wherein the sealing portion and the at least one stabilizing rib each have an outer diameter measured perpendicularly to the longitudinal axis of the piston, the outer diameter of the sealing portion being greater than the outer diameter of the at least one stabilizing rib.

14. The method of claim 13, wherein the trim edge has an outer diameter measured perpendicularly to the longitudinal axis of the piston, the outer diameter of the at least one stabilizing rib being greater than the outer diameter of the trim edge.

15. The method of claim 12, wherein the trim edge is proximally spaced apart from the at least one stabilizing rib.

16. The method of claim 10, wherein the trim edge is proximally spaced apart from the sealing portion.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0009] The foregoing summary, as well as the following detailed description of a preferred embodiment of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings an embodiment which is presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

[0010] In the drawings:

[0011] FIG. 1 is a partially sectioned side view of a pharmaceutical syringe containing a piston body in accordance with a preferred embodiment of the present invention;

[0012] FIG. 2 is a side elevational view of the piston body of FIG. 1; and

[0013] FIG. 3 is a bottom side perspective view of the piston body of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Certain terminology is used in the following description for convenience only and is not limiting. The words “right,” “left,” “lower” and “upper” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the piston and designated parts thereof. Unless specifically set forth herein, the terms “a”, “an” and “the” are not limited to one element but instead should be read as meaning “at least one”. The terminology includes the words noted above, derivatives thereof and words of similar import.

[0015] Referring to the drawings, wherein the same reference numerals are used to designate the same components throughout the several figures, there is shown in FIG. 1 a pharmaceutical syringe 10 for dispensing medicament (not shown) to a patient. The syringe 10 includes a preferably cylindrically-shaped hollow barrel 12 configured to retain the medicament. The barrel 12 may be made from glass, plastic, or the like, as is conventionally known. The barrel 12 preferably has a longitudinal axis A, and an inner wall 14 that is coaxially disposed about the longitudinal axis A.

[0016] The barrel 12 also includes a first axial opening 16 and an opposing second axial opening 18. The first axial opening 16 may be fitted to a delivery device (not shown), such as a conventional needle, transfer device, or the like (not shown), for transporting the medicament from the barrel 12 to the patient. The second axial opening 18 is provided for the receipt and movement of a longitudinally extending plunger shaft 20. The plunger shaft 20 extends from a first axial end (not shown), through the second axial opening 18 of the barrel 12, to a second axial end 20a. The first axial end of the plunger shaft 20 engages a piston body 22 slidably disposed within the barrel 12. The piston body 22 is formed substantially of a resilient material, such as rubber or similar elastomer.

[0017] Referring to FIGS. 2 and 3, the piston body 22 includes opposing first and second axial ends 22a, 22b and is coaxially disposed with respect to the longitudinal axis A of the barrel 12. The piston body 22 includes a face portion 23 at the first axial end 22a thereof that is preferably formed of a central face portion 24 and an annular curved portion 28. The central face portion 24 is preferably oriented essentially perpendicularly with respect to the longitudinal axis A and faces the first axial opening 16 of the barrel 12. In this manner, the central face portion 24 is used to contact the medicament and force it through the first axial opening 16 of the barrel 12. The central face portion 24 also preferably has a maximum diameter D.sub.F measured perpendicularly to the longitudinal axis A that defines an outer circumference of the central face portion 24. The central face portion 24 preferably has a conical shape, such that a center thereof is spaced apart from the outer circumference thereof along the longitudinal axis A. However, the shape of the central face portion 24 is not so limited, and may also be frusto-conical, flat, rounded, or the like. The inner wall 14 of the barrel 12 proximate the first axial opening 16 may be shaped to complement the shape of the central face portion 24 of the piston body 22.

[0018] The piston body 22 further includes a sealing portion 26 proximate the face portion 23 which, when the piston body 22 is disposed within the barrel 12, is in contact with the inner wall 14 of the barrel 12. The sealing portion 26 preferably has a first axial end 26a, a second axial end 26b, and a wall 27 extending therebetween, which is preferably cylindrically shaped and lies along the longitudinal axis A of the syringe 10 when the piston body 22 is disposed in the barrel 14. The cylindrically shaped part of the sealing portion 26 preferably has a diameter D.sub.S, measured perpendicularly to the longitudinal axis A, that is essentially constant along the longitudinal axis A between the first and second axial ends 26a, 26b of the sealing portion 26, and which defines an outer circumference thereof to contact the inner wall 14 of the barrel 12. This contact provides a fluid-tight seal to prevent medicament from seeping past the piston body 22 and toward the second axial opening 18. It is preferred that the maximum diameter D.sub.F of the central face portion 24 is smaller than the diameter D.sub.S of the sealing portion 26.

[0019] The maximum outer circumference of the central face portions 24 of the piston body 22 may be connected to the first axial end 26a of the sealing portion 26 by the annular curved portion 28 of the face portion 23. Preferably, the curved portion 28 is outwardly convex in shape, as shown in FIG. 2, such that the radius of curvature extends into the piston body 22. However, other configurations may be used to connect the outer circumferences of the central face and sealing portions 24, 26, such as concave shapes (e.g., wherein the radius of curvature extends away from the piston body 22), multiple convex/concave curves, or the like. The annular curved portion 28 preferably has an outer diameter that is smaller than the diameter DS of the sealing portion 26.

[0020] In preferred embodiments of the present invention, the central face portion 24 and at least a portion of the annular curved portion 28 of the piston body 22 are enclosed by an inert film 30. The film 30 is preferably made from a fluorinated polymer material, as is generally known. To avoid the disadvantages described above, the film 30 preferably does not extend axially beyond the first axial end 26a of the sealing portion 26 or along any part of the sealing section 26. That is, the film 30 is disposed coaxially with the longitudinal axis and has an outer circumference that is smaller in size than the outer circumference of the sealing portion 26, which is sufficiently sized to maintain contact of the sealing portion 26 of the piston body 22 with the inner wall 14 of the barrel 12. Preferably, the outer boundary of the film 30 is disposed between the first axial end 26a of the cylindrical sealing portion 26 and the outer circumference of the central face portion 24. As a result of this configuration, the outer surface of the inert film 30 that lies exposed on the piston body 22 is transverse to the longitudinal axis A. In this way, contact with the inner wall 14 by the inert film 30 is minimized while the critical function of maintaining a contamination seal between the piston body 22 and the drug in contact therewith.

[0021] It is preferred that the piston body 22 also include at least one, and more preferably a plurality, of radially protruding stabilizing ribs 32 that are disposed between the sealing portion 26 and the second axial end 22b of the piston body 22. Each rib 32 includes a diameter DR measured perpendicularly to the longitudinal axis A and an outer circumference, each of which may be identical for each rib 32, as shown in FIGS. 1-3. However, the circumference and diameter DR may differ between ribs 32, as desired. It is preferred that the outer circumference and diameter DR of the ribs 32 are smaller than the respective outer circumference and diameter D.sub.S of the sealing portion 26 such that the ribs 32 have minimal contact with the inner wall 14 of the barrel 12. The ribs 32 are provided primarily for stabilizing the piston body 22 within the syringe 10, although the ribs 32 may perform some sealing functions within the barrel 12, and it is desired to avoid adding unnecessary forces between the piston body 22 and the barrel 12.

[0022] The ribs 32 are preferably spaced apart along the longitudinal axis A from each other, and from the sealing portion 26 of the piston body 22, by one or more annular recesses 34, which are disposed between adjacent ribs 32 and between the second axial end 26b of the sealing portion 26 and an adjacent rib 32. The diameter and circumference of the piston body 22 at each annular recess 34 may vary as necessary, as the material of the piston body 22 within each recess 34 generally will not have much interaction with the overall syringe 10.

[0023] Toward the second axial end 22b of the piston body 22 will be a trim edge 36, which is where the completed piston body 22 is separated from a sheet (not shown) containing a plurality of piston bodies 22 manufactured together as will be described in further detail below. The outer circumference and diameter of the trim edge are preferably smaller than the corresponding dimensions of the ribs 32 so as to have no interaction with the inner wall 14 of the barrel 12. In addition, the trim edge 36 does not need to be disposed as shown in FIGS. 1-3, but may instead be placed elsewhere on the piston body 22. Moreover, the trim edge 36 may form one of the other components of the piston body 22, such as a rib 32, annular recess 34, the sealing portion 26, or the like.

[0024] A receiving cavity 38 is formed from the second axial end 22b of the piston body 22 and extends longitudinally within the piston body 22. The receiving cavity 38 is configured to receive the first axial end of the plunger shaft 20. The receiving cavity 38 may be sized and dimensioned as appropriate to securely receive the plunger shaft 20, which is preferably attached to the piston body 22 via a screw thread (not shown), although other connection types, such as friction or interference fits, adhesives, welding, mechanical fasteners, and the like may be used.

[0025] It is also preferred that at least a portion of the piston body 22 is coated with a lubricant to further lower BLE forces between the piston body 22 and the inner wall 14 of the barrel 12. The lubricant further prevents the piston body 22 from sticking to the inner wall 14 during the injection process.

[0026] A process for manufacturing the piston body 22 will now be described. First, a non-vulcanized rubber sheet (not shown) together with a foil-like inert film (not shown) may be placed between die plates of a forming tool (not shown). The inert film, which is initially flat, can be firmly joined with the rubber sheet. However, the film and rubber sheet may be introduced between the die plates independently from one another and placed loosely on top of each other. The rubber sheet is vulcanized under the influence of heat and pressure and is non-detachably joined with the inert film. The forming tool forms the face portion 23, including the central face portion 24 and annular curved portion 28, as well as the sealing portion 26 of the piston body 22 in this first step.

[0027] The partially formed piston bodies 22 may thereafter be blanked out from the rubber sheet and placed into a second forming tool (not shown). A second non-vulcanized rubber sheet (not shown) is also placed into the second forming tool. Under the influence of heat and pressure, the second rubber sheet is vulcanized and molded to form the remainder of the piston body 22 to the second axial end 22b, all of which is joined to the sealing portion 26 at the second axial end 26b thereof. During this process, the receiving cavity 38 is also molded into the piston body 22 from the second axial end 22b. Subsequently, the piston body 22 is blanked out from the rubber sheet at the trim edge 36.

[0028] Although this is the preferred method for manufacturing the piston body 22 in accordance with the present invention, other methods for the formation of a piston body 22 and the attachment of an inert film to the piston body 22 may be used.

[0029] It will be appreciated by those skilled in the art that changes could be made to the embodiment described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.