Plunger for syringe

• US 6,129,712 A
• Filed: 06/10/1999
• Issued: 10/10/2000
• Est. Priority Date: 11/05/1998
• Status: Expired due to Term

• Current Assignee: Daikyo Seiko, Ltd.
• Original Assignee: Daikyo Seiko, Ltd.
• Inventors: Sudo, Morihiro, Asai, Kouichi
• Primary Examiner(s): YASKO JR, JOHN D
• Application Number:
  US09/329,624
• Time in Patent Office: 488 Days
• Field of Search: 604/218, 604/187, 604/219, 604/224, 604/228
• US Class Current: 604/218
• CPC Class Codes: A61M 2205/0222 Materials for reducing friction
• CPC Class Codes: A61M 2205/0238 the material being a coating or protective layer
• CPC Class Codes: A61M 5/31513 Piston constructions to improve sealing or sliding
• CPC Class Codes: A61M 5/31515 Connection of piston with piston rod

Abstract

In a plunger for a syringe including a laminated piston which is provided with a shaft with a female thread and which is slidably inserted into a barrel and a rod having a male thread which can be screw-engaged in the threaded hole of the laminated piston, the axial length T of the crest of the female thread and the root of the male thread which engages with the female thread is greater than the axial length t of the root of the female thread and the crest of the male thread.

Claims

1. A plunger for a syringe including a piston which is slidably inserted into a barrel and a rod connected to said piston, comprising:

a female thread formed at the center of said piston; and

a male thread which is screw-engaged into the female thread of the piston;

wherein the axial length T of the crest of the female thread and the root of the male thread which engages with the female thread is greater than the axial length t of the root of the female thread and the crest of the male thread.

2. The plunger for a syringe according to claim 1, wherein said piston comprises a laminated piston, said laminated piston comprising a rubber piston and a laminated layer of synthetic resin which coats the outer surface of the rubber piston.

3. The plunger for a syringe according to claim 1, wherein the axial length T of the crest of the female thread and the root of the male thread which engages with the internal and the axial length t of the root of the female thread and the crest of the male thread satisfies the following condition:

T>

1.2t.

4. The plunger for a syringe according to claim 3, wherein the axial length T of the crest of the female thread and the root of the male thread which engages with the internal and the axial length t of the root of the female thread and the crest of the male thread satisfies the following condition:

T>

1.5t.

5. The plunger for a syringe according to claim 2, wherein said rubber piston of the laminated piston is made from one of the following:

IIR, NBR, BR, or EPDM.

6. The plunger for a syringe according to claim 2, wherein said laminated film layer of the laminated piston is made of a resin material selected from the following:

tetrafluoroethylene, ethylene-tetrafluoroethylene, and ultra high molecular weight polyethylene.