Pipette piston seal assembly

• US 6,926,867 B1
• Filed: 10/30/2001
• Issued: 08/09/2005
• Est. Priority Date: 10/30/2001
• Status: Expired due to Fees

• Current Assignee: WPI-Tag Acquisition, LLC
• Original Assignee: World Precision Instruments Inc.
• Inventors: Liu, Guo Chen, Liu, Su Yi
• Primary Examiner(s): Ludlow, Jan M.
• Application Number:
  US10/003,537
• Time in Patent Office: 1,379 Days
• Field of Search: 422/100, 738/641.3, 738/641.6
• US Class Current: 422/501
• CPC Class Codes: B01L 2200/0689 Sealing
• CPC Class Codes: B01L 3/0217 of the plunger pump type medical syringes A61M

Abstract

A piston seal assembly for a pipette includes an O-ring having radially inner and outer surfaces and axially separated first and second surfaces. A seal includes a radially extending rim portion having axially separated first and second surfaces and an axially extending sleeve portion forming an opening. A seat includes an axially extending indexing portion and a radially extending engagement portion forming an opening and having axially separated first and second surfaces. The seal is positioned such that the pipette piston extends through the opening and the radially inner surface of the sleeve portion slidably engages the piston. The seat is positioned such that the piston extends through the opening, the first and second surfaces of the engagement portion engage the second surface of the rim portion and an end of the spring, respectively, and the radially outer surface of the indexing portion engages the inner surface of the pipette body. The O-ring is positioned such that the sleeve portion of the seal extends axially through the opening of the O-ring, the radially inner surface of the O-ring engages the radially outer surface of the sleeve portion, the radially outer surface of the O-ring engages the radially inner surface of the indexing portion, the first surface of the O-ring engages a shoulder of the pipette body, and the second surface of the O-ring engages the first surface of the rim portion.

Claims

1. A piston seal assembly for a pipette having a body, a piston, and a spring, the body including a shaft segment and a housing segment, the shaft segment defining a bore, the housing segment defining a cavity which is coaxial with the bore, the cavity having an inner surface and defining a shoulder, the piston including a rod segment disposed within the body, an operator segment disposed exterior to the body, and an engagement member disposed intermediate the rod and operator segments, the spring being disposed within the cavity and providing a biasing force between the shoulder of the body and the engagement member of the piston, the seal assembly comprising:

an O-ring having radially inner and outer surfaces and axially separated first and second surfaces, the radially inner surface defining an opening, the first surface being adapted for engaging the shoulder;

an integral, one-piece, substantially circular seal composed of UHMWPE having a radially extending rim portion and an axially extending sleeve portion, the sleeve portion extending axially through the opening of the O-ring and having radially inner and outer surfaces, the radially outer surface of the sleeve portion engaging the radially inner surface of the O-ring, the radially inner surface of the sleeve portion being adapted for slidably engaging the rod segment of the piston, the rim portion having axially separated first and second surfaces, the first surface of the rim portion engaging the second surface of the O-ring; and

an integral, one-piece, substantially circular seat having a radially extending engagement portion and an axially extending indexing portion, the indexing portion having radially inner and outer surfaces, the engagement portion having axially separated first and second surfaces and defining an opening adapted for receiving the rod segment of the piston, the first surface of the engagement portion engaging the second surface of the rim portion, the second surface of the engagement portion being adapted for engaging an end of the spring, the radially inner surface of the indexing portion engaging the radially outer surface of the O-ring, the radially outer surface of the indexing portion being adapted for engaging the inner surface of the cavity.

2. The piston seal assembly of claim 1 wherein the O-ring is deformable by the biasing force of the spring whereby the radially inner surface of the O-ring urges the sleeve portion of the seal into sealing engagement with the rod segment of the piston and the radially outer surface of the O-ring urges the indexing portion of the seat into sealing engagement with the surface of the cavity.

3. The piston seal assembly of claim 1 wherein the O-ring is composed of rubber.

4. A pipette comprising:

a body including a shaft segment and a housing segment, the shaft segment defining a bore, the housing segment defining a cavity which is coaxial with the bore, the cavity having an inner surface and defining a shoulder;

a piston including a rod segment disposed within the body, an operator segment disposed exterior to the body, and an engagement member disposed intermediate the rod and operator segments;

a spring having opposite first and second ends, the first end engaging the engagement member of the piston; and

a seal assembly including

an O-ring having radially inner and outer surfaces and axially separated first and second surfaces, the radially inner surface defining an opening, the first surface engaging the shoulder of the body;

an integral, one-piece, substantially circular seal composed of UHMWPE having a radially extending rim portion and an axially extending sleeve portion, the sleeve portion extending axially through the opening of the O-ring and having radially inner and outer surfaces, the radially outer surface of the sleeve portion engaging the radially inner surface of the O-ring, the radially inner surface of the sleeve portion defining an opening receiving the rod segment of the piston, the radially inner surface slidably engaging the rod segment of the piston, the rim portion having axially separated first and second surfaces, the first surface of the rim portion engaging the second surface of the O-ring, and

an integral, one-piece, substantially circular seat having a radially extending engagement portion and an axially extending indexing portion, the indexing portion having radially inner and outer surfaces, the engagement portion having axially separated first and second surfaces and defining an opening receiving the rod segment of the piston, the first surface of the engagement portion engaging the second surface of the rim portion, the second surface of the engagement portion engaging the second end of the spring, the radially inner surface of the indexing portion engaging the radially outer surface of the O-ring, the radially outer surface of the indexing portion engaging the a surface of the cavity;

wherein the O-ring is deformed by the biasing force of the spring whereby the radially inner surface of the O-ring urges the sleeve portion of the seal into sealing engagement with the rod segment of the piston and the radially outer surface of the O-ring urges the indexing portion of the seat into sealing engagement with the inner surface of the cavity.

5. A piston seal assembly for a pipette having a body, a piston, and a spring, the body including a shaft segment and a housing segment, the shaft segment defining a bore, the housing segment defining a cavity which is coaxial with the bore, the cavity having an inner surface and defining a shoulder, the piston including a rod segment disposed within the body, an operator segment disposed exterior to the body, and an engagement member disposed intermediate the rod and operator segments, the spring being disposed within the cavity and providing a biasing force between the shoulder of the body and the engagement member of the piston, the seal assembly comprising:

an O-ring composed of rubber having radially inner and outer surfaces and axially separated first and second surfaces, the radially inner surface defining an opening, the first surface being adapted for engaging the shoulder;

an integral, one-piece, substantially circular seal composed of UHMWPE having a radially extending rim portion and an axially extending sleeve portion, the sleeve portion extending axially through the opening of the O-ring and having radially inner and outer surfaces, the radially outer surface of the sleeve portion engaging the radially inner surface of the O-ring, the radially inner surface of the sleeve portion being adapted for slidably engaging the rod segment of the piston, the rim portion having axially separated first and second surfaces, the first surface of the rim portion engaging the second surface of the O-ring; and

an integral, one-piece, substantially circular seat having a radially extending engagement portion and an axially extending indexing portion, the indexing portion having radially inner and outer surfaces, the engagement portion having axially separated first and second surfaces and defining an opening adapted for receiving the rod segment of the piston, the first surface of the engagement portion engaging the second surface of the rim portion, the second surface of the engagement portion being adapted for engaging an end of the spring, the radially inner surface of the indexing portion engaging the radially outer surface of the O-ring, the radially outer surface of the indexing portion being adapted for engaging the inner surface of the cavity.