Syringe plunger with one piece hollow gasket and plunger rod

• US 9,731,077 B2
• Filed: 07/31/2006
• Issued: 08/15/2017
• Est. Priority Date: 08/01/2005
• Status: Active Grant

• Current Assignee: Nipro Corporation
• Original Assignee: Nipro Corporation
• Inventors: Namba, Ryohei, Kato, Hidero, Hirobe, Teruhisa, Tanaka, Shigeki, Iwasa, Masanobu
• Primary Examiner(s): Mehta, Bhisma
• Assistant Examiner(s): Engel, Matthew A
• Application Number:
  US11/989,689
• Publication Number:
  US 20110178475A1
• Time in Patent Office: 4,033 Days
• Field of Search: 604222, 604223, 604228, 604233
• CPC Class Codes: A61M 5/31511 Piston or piston-rod constructions, e.g. connection of piston with piston-rod A61M5/5066 takes precedence
• CPC Class Codes: A61M 5/31515 Connection of piston with piston rod

Abstract

A plunger for a syringe, in which a plunger rod can be prevented by a simple structure from unavoidably falling out of place.

The plunger for a syringe includes the plunger rod and a gasket. The gasket is closed at its upper end and has an inner space, and an opening having a diameter smaller than the diameter of the inner space is provided in the lower end of the gasket. The plunger rod has a collar installed at the tip of the plunger rod. When the collar is positioned in the inner space of the gasket, the plunger rod and the gasket are freely movably fitted together without intimate contact between them.

Claims

1. A syringe plunger consisting essentially of a plunger rod and a gasket;

wherein the gasket is a one-piece cylindrical hollow member formed of a resin having rubber elasticity, said gasket having a closed upper end formed by an inner ceiling surface;

a lowermost end; and

having a cylindrical inner space;

said gasket at the lowermost end thereof being provided with an opening having a diameter smaller than a diameter of the cylindrical inner space, said opening being formed by an inwardly extending annular rib formed on an inner surface of the gasket at the lowermost end thereof, the annular rib having a top face and a bottom face and a thickness L; and

wherein

the plunger rod comprises a cylindrical collar attached to a distal end of the plunger rod, the collar being positioned entirely within the cylindrical inner space and having a collar top face, a collar bottom face and an annular side wall between the collar top face and collar bottom face, an outer diameter of the annular side wall being greater than the diameter of said opening and smaller than the diameter of the cylindrical inner space, the collar having a height N from the collar bottom face to the collar top face, with a top face of the plunger rod and the collar bottom face forming a gap K;

wherein

the outer diameter of the annular side wall of the collar is less than the inner diameter of the cylindrical inner space and greater than the diameter of the opening and, when the height of the cylindrical inner space from the top face of the annular rib to the inner ceiling surface of the gasket is M, the syringe plunger satisfies the following relationship;

(K−

L)>

(M−

N).

2. The syringe plunger according to claim 1, wherein smooth movement of the collar with respect to the inner ceiling surface of the gasket is impaired and slipping of the collar is controllable when the collar top face is brought into press contact with the inner ceiling surface of the cylindrical inner space of the gasket.

3. The syringe plunger according to claim 1, wherein a projection is provided on the collar top face and a recess to be engaged or fitted to the projection is provided on the inner ceiling surface of the gasket.

4. The syringe plunger according to claim 1, wherein a recess is provided on the collar top face and a projection to be engaged or fitted to the recess is provided on the inner ceiling surface of the gasket.

5. The syringe plunger according to claim 1, wherein the annular side wall of the collar is formed into a tapered shape reducing in diameter thereof toward a distal end thereof.

6. The syringe plunger according to claim 1, wherein the plunger rod and the collar are attached by a screw-engagement between a male thread provided at the distal end of the plunger rod and a female thread provided inside the collar.

7. The syringe plunger according to claim 6, wherein the screw-engagement and release of the screw-engagement between the plunger rod and the collar are freely achieved when the collar top face is brought into press contact with the inner ceiling surface of the inner space of the gasket.

8. A syringe including the syringe plunger according to claim 1, the syringe having a barrel and the syringe plunger being inserted into the barrel so as to be liquid-tight and slidable with the gasket being in direct contact with the barrel.