WO1990014162A1 - Improved molded pipette tip - Google Patents

Improved molded pipette tip Download PDF

Info

Publication number
WO1990014162A1
WO1990014162A1 PCT/US1990/002936 US9002936W WO9014162A1 WO 1990014162 A1 WO1990014162 A1 WO 1990014162A1 US 9002936 W US9002936 W US 9002936W WO 9014162 A1 WO9014162 A1 WO 9014162A1
Authority
WO
WIPO (PCT)
Prior art keywords
pipette
tip
section
right cylinder
cylindrical
Prior art date
Application number
PCT/US1990/002936
Other languages
French (fr)
Inventor
Gregory Mathus
William J. Lacey
Original Assignee
Costar Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Costar Corporation filed Critical Costar Corporation
Publication of WO1990014162A1 publication Critical patent/WO1990014162A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
    • B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
    • B01L3/02—Burettes; Pipettes
    • B01L3/0275—Interchangeable or disposable dispensing tips
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
    • A61M2202/00—Special media to be introduced, removed or treated
    • A61M2202/04—Liquids
    • A61M2202/0413—Blood
    • A61M2202/0456—Lipoprotein
    • A61M2202/046—Low-density lipoprotein

Definitions

  • This invention relates to an improved construction for a molded pipette.
  • Pipettes are made from glass or plastic. Glass pipettes are formed of a unitary tubular extrusion, one end of which is drawn while the glass is hot to form a dispensing tip in the shape of a funnel. The long, generally right-cylindrical tip is cut to desired length.
  • Plastic pipettes have largley replaced glass pipettes for many particular uses. In spite of this, commercially available plastic pipettes have a serious drawback.
  • Plastic pipettes typically have a molded or drawn dispensing tip in the shape of a hollow cone with an open, narrow end. Such tips tend to drip or leak, especially in larger pipettes, in which the opening of the cone typically has a greater diameter to allow for speedy dispensing of larger volumes. Dripping and leaking can be reduced or even eliminated by reducing the size of the opening, but doing so undesirably restricts flow.
  • the invention provides a plastic, molded pipette that overcomes these problems and provides further advantages.
  • the molded plastic pipette of the invention has a funnel-shaped dispensing tip with a narrow end which then extends into a substantially right- cylindrical terminal portion. This right- cylindrical end section eliminates or substantially reduces dripping.
  • FIG. 1 is a side view of the molded, plastic pipette of the invention.
  • FIG. 2 is an exploded cross-sectional view of a portion of the pipette's main chamber and tip of the invention.
  • the pipette 10 of the invention has a conventional aperture 12 for connection to positive or negative air pressure, a central cylindrical section 14 for containing a volume of fluid and a terminal dispensing portion 15 which includes a penultimate frustoconical section 16 and a terminal, substantially right-cylindrical tip 18.
  • the frustoconical section 16 defines a chamber of which the inner diameter decreases
  • the pipette 10 may be made entirely of any suitable plastic as will be known to those skilled in the art, including, but not limited to, styrene or polypropylene based plastics.
  • the central cylindrical section 14 is extruded, and the terminal dispensing portion 15 is molded.
  • the right-cylindrical tip 18 has an inner diameter ofslightly decreasing diameter in the direction of the tip end 20 so that the molded terminal dispensing portion 15 may be easily removed from a mold.
  • a pitch of 1.5 degrees has been found to be suitable.
  • the terminal dispensing portion 15 may be fitted to the central cylindrical section 14 by a mating flange and recess arrangement.
  • the open end of the frustoconical section 16 is provided with a flange 22 which may be inserted into the end 24 of the central cylindrical section 14.
  • the inside surface of the flange is angled as at 25 such that when the central cylindrical section 14 and terminal dispensing portion 15 are joined, the inner surface of the assembled pipette has a substantially smooth transition at the junction.
  • the central cylindrical section 14 and the terminal dispensing portion 15 may be joined in any conventional manner such as, for example, by adhesive agents, although ultrasonic welding is preferred.
  • the embodiment shown in the drawings is intended for delivery of approximately 50 ml aliquots of fluid.
  • the axial length of the frustoconical section 16 is 3.2 cm and has a tapering inside diameter, decreasing from 1.3 cm at the juncture with the central cylindrical section 14 to .34 cm where it meets the substantially right-cylindrical tip 18.
  • the tip 18 is .5 cm in axial length, and has a slightly tapering diameter, decreasing from .34 cm at the juncture with the frustoconical section 16, to a terminal diameter of .31 cm at the tip end 20.
  • the terminal narrow tip 18 is of particular advantage in pipettes having a calibrated volume greater than 20 ml and/or having tip openings greater than 2.5 mm in diameter; the tip construction permits the terminal aperture to be large enough for rapid pipette content delivery, but yet to resist dripping.
  • a prior art pipette having a frustoconical tip is more vertically inclined than the upper surface of the right-cylindrical tip of the invention.
  • Air present in the tip of a pipette of the invention is therefore more restricted from retrograde motion by frictional forces than in the prior art pipette, resulting in less dripping and consequential increase in the accuracy of the volume dispensed.
  • dripping will be opposed more than in the same axial length of fluid in the prior art pipettes: the smaller cross-sectional area will promote fluid retention by increasing capillary forces.
  • the invention is of particular advantage when used with automated or manual pipette driver attachments. With these systems, when expelling the fluid from a pipette, sufficient pressure can develop to cause the fluid to be expelled rapidly. When the pressure is terminated before the pipette is emptied, inertia causes the fluid to continue draining momentarily, then to pull into the pipette to relieve the resultant internal vacuum.
  • the tip of the invention tends to restrict the air intake to a bubble which remains within the substantially right-cylindrical tip 18, unlike the prior art pipette, in which an air bubble pulled into the tip via a vacuum force as described above tends to rise into the pipette central chamber, with subsequent dripping.
  • the volume defined by a given axial length of the right-cylindrical tip 18 of the invention is less than the volume defined by the same axial length of a tip of the prior art pipette having the same cross sectional area at the tip end. Because of this, the fluid meniscus is drawn further away from the tip end 20 than in conventional pipettes, which may decrease subsequent dripping.
  • the construction may also result in a precisely reproducible volume of fluid remaining in the pipette terminus when the instrument is allowed to drain in a "to-delivery" or "T.D.” usage, facilitating accurate calibration.

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  • Health & Medical Sciences (AREA)
  • Clinical Laboratory Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Devices For Use In Laboratory Experiments (AREA)

Abstract

The molded plastic pipette (10) of the invention has a funnel-shaped (16) dispensing tip with a narrow end which then extends into a substantially right-cylindrical terminal portion (18). This right-cylindrical end section (18) eliminates or substantially reduces dripping.

Description

IMPROVED MOLDED PIPETTE TIP
This invention relates to an improved construction for a molded pipette.
Background of the Invention Pipettes are made from glass or plastic. Glass pipettes are formed of a unitary tubular extrusion, one end of which is drawn while the glass is hot to form a dispensing tip in the shape of a funnel. The long, generally right-cylindrical tip is cut to desired length.
Plastic pipettes have largley replaced glass pipettes for many particular uses. In spite of this, commercially available plastic pipettes have a serious drawback.
Plastic pipettes typically have a molded or drawn dispensing tip in the shape of a hollow cone with an open, narrow end. Such tips tend to drip or leak, especially in larger pipettes, in which the opening of the cone typically has a greater diameter to allow for speedy dispensing of larger volumes. Dripping and leaking can be reduced or even eliminated by reducing the size of the opening, but doing so undesirably restricts flow.
The invention provides a plastic, molded pipette that overcomes these problems and provides further advantages.
Summary of the Invention The molded plastic pipette of the invention has a funnel-shaped dispensing tip with a narrow end which then extends into a substantially right- cylindrical terminal portion. This right- cylindrical end section eliminates or substantially reduces dripping.
Brief Description of the Drawings FIG. 1 is a side view of the molded, plastic pipette of the invention; and
FIG. 2 is an exploded cross-sectional view of a portion of the pipette's main chamber and tip of the invention.
Detailed Description of the Drawings Referring to FIGS. 1 and 2, the pipette 10 of the invention has a conventional aperture 12 for connection to positive or negative air pressure, a central cylindrical section 14 for containing a volume of fluid and a terminal dispensing portion 15 which includes a penultimate frustoconical section 16 and a terminal, substantially right-cylindrical tip 18. The frustoconical section 16 defines a chamber of which the inner diameter decreases
from that of the central cylindrical section 14 to that of the end of the right-cylindrical tip 18 at the junction of tip 18 and frustoconical section 16.
The pipette 10 may be made entirely of any suitable plastic as will be known to those skilled in the art, including, but not limited to, styrene or polypropylene based plastics.
In one embodiment, the central cylindrical section 14 is extruded, and the terminal dispensing portion 15 is molded. Preferably, the right-cylindrical tip 18 has an inner diameter ofslightly decreasing diameter in the direction of the tip end 20 so that the molded terminal dispensing portion 15 may be easily removed from a mold. A pitch of 1.5 degrees has been found to be suitable. The terminal dispensing portion 15 may be fitted to the central cylindrical section 14 by a mating flange and recess arrangement. In the embodiment shown, the open end of the frustoconical section 16 is provided with a flange 22 which may be inserted into the end 24 of the central cylindrical section 14. The inside surface of the flange is angled as at 25 such that when the central cylindrical section 14 and terminal dispensing portion 15 are joined, the inner surface of the assembled pipette has a substantially smooth transition at the junction. The central cylindrical section 14 and the terminal dispensing portion 15 may be joined in any conventional manner such as, for example, by adhesive agents, although ultrasonic welding is preferred.
The embodiment shown in the drawings is intended for delivery of approximately 50 ml aliquots of fluid. The axial length of the frustoconical section 16 is 3.2 cm and has a tapering inside diameter, decreasing from 1.3 cm at the juncture with the central cylindrical section 14 to .34 cm where it meets the substantially right-cylindrical tip 18. The tip 18 is .5 cm in axial length, and has a slightly tapering diameter, decreasing from .34 cm at the juncture with the frustoconical section 16, to a terminal diameter of .31 cm at the tip end 20.
The terminal narrow tip 18 is of particular advantage in pipettes having a calibrated volume greater than 20 ml and/or having tip openings greater than 2.5 mm in diameter; the tip construction permits the terminal aperture to be large enough for rapid pipette content delivery, but yet to resist dripping.
Although the inventors do not intend to be bound by any particular theory of their invention, it is believed that a variety of factors may contribute to the success of the invention. When the central cylindrical sections are oriented at the same downward angle, the upper, terminal surface of
a prior art pipette having a frustoconical tip is more vertically inclined than the upper surface of the right-cylindrical tip of the invention. Air present in the tip of a pipette of the invention is therefore more restricted from retrograde motion by frictional forces than in the prior art pipette, resulting in less dripping and consequential increase in the accuracy of the volume dispensed. Further, for a small amount of fluid present in the cylindrical tip of the invention, dripping will be opposed more than in the same axial length of fluid in the prior art pipettes: the smaller cross-sectional area will promote fluid retention by increasing capillary forces.
The invention is of particular advantage when used with automated or manual pipette driver attachments. With these systems, when expelling the fluid from a pipette, sufficient pressure can develop to cause the fluid to be expelled rapidly. When the pressure is terminated before the pipette is emptied, inertia causes the fluid to continue draining momentarily, then to pull into the pipette to relieve the resultant internal vacuum. The tip of the invention tends to restrict the air intake to a bubble which remains within the substantially right-cylindrical tip 18, unlike the prior art pipette, in which an air bubble pulled into the tip via a vacuum force as described above tends to rise into the pipette central chamber, with subsequent dripping. Further, the volume defined by a given axial length of the right-cylindrical tip 18 of the invention is less than the volume defined by the same axial length of a tip of the prior art pipette having the same cross sectional area at the tip end. Because of this, the fluid meniscus is drawn further away from the tip end 20 than in conventional pipettes, which may decrease subsequent dripping.
The construction may also result in a precisely reproducible volume of fluid remaining in the pipette terminus when the instrument is allowed to drain in a "to-delivery" or "T.D." usage, facilitating accurate calibration.
It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted in an illustrative and not limiting sense.
What is claimed is:

Claims

1. In a molded plastic pipette having a funnel shaped dispensing tip with a narrow end, the improvement comprising, a substantially right cylinder extending from the narrow end of the funnel.
2. A plastic molded pipette having a tip formed of a frustoconical penultimate section of decreasing diameter terminating in a substantially right-cylindrical end section.
3. A molded plastic pipette comprising, a main chamber having the shape of a right cylinder, a penultimate dispensing section extending from the right cylinder and having a progressively decreasing diameter, and a terminal end section substantially in the shape of a right cylinder.
4. A pipette as claimed in claim 3 wherein the terminal end section has a pitch of about 1.5 degrees.
5. A pipette as claimed in claim 3 wherein the main chamber is a unitary piece, the penultimate section and end section are unitary pieces, and the two unitary pieces are bonded to one another.
PCT/US1990/002936 1989-05-25 1990-05-24 Improved molded pipette tip WO1990014162A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US35718089A 1989-05-25 1989-05-25
US357,180 1989-05-25

Publications (1)

Publication Number Publication Date
WO1990014162A1 true WO1990014162A1 (en) 1990-11-29

Family

ID=23404618

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1990/002936 WO1990014162A1 (en) 1989-05-25 1990-05-24 Improved molded pipette tip

Country Status (1)

Country Link
WO (1) WO1990014162A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0493857A2 (en) * 1991-01-04 1992-07-08 Johnson & Johnson Clinical Diagnostics, Inc. Improved method of detecting pre-spotting when dispensing sample
EP1093856A1 (en) * 1999-10-21 2001-04-25 Tecan Schweiz AG Replaceable pipette tip and method for producing the same, associated pipette-head and pipetting system
US6596240B2 (en) 2001-01-12 2003-07-22 Porex Corporation Pipette tip for easy mounting and ejecting from a pipette
EP1618060A2 (en) * 2003-04-30 2006-01-25 Aurora Discovery Inc. Method and system for precise dispensation of a liquid

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1698340A (en) * 1929-01-08 Liquid dropper
US3696971A (en) * 1970-09-24 1972-10-10 Electro Nucleonics Mechanism for simultaneously metering and dispensing liquids
FR2196851A1 (en) * 1972-08-21 1974-03-22 Oxford Lab
US4347875A (en) * 1980-07-14 1982-09-07 Eastman Kodak Company Self-cleaning nozzle construction for aspirators
US4349109A (en) * 1980-10-20 1982-09-14 Medical Laboratory Automation, Inc. Disposable pipette tips and trays therefor
USRE31555E (en) * 1973-04-30 1984-04-17 Beral Enterprises, Inc. Pipette

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1698340A (en) * 1929-01-08 Liquid dropper
US3696971A (en) * 1970-09-24 1972-10-10 Electro Nucleonics Mechanism for simultaneously metering and dispensing liquids
FR2196851A1 (en) * 1972-08-21 1974-03-22 Oxford Lab
USRE31555E (en) * 1973-04-30 1984-04-17 Beral Enterprises, Inc. Pipette
US4347875A (en) * 1980-07-14 1982-09-07 Eastman Kodak Company Self-cleaning nozzle construction for aspirators
US4349109A (en) * 1980-10-20 1982-09-14 Medical Laboratory Automation, Inc. Disposable pipette tips and trays therefor

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0493857A2 (en) * 1991-01-04 1992-07-08 Johnson & Johnson Clinical Diagnostics, Inc. Improved method of detecting pre-spotting when dispensing sample
EP0493857B1 (en) * 1991-01-04 1995-09-20 Johnson & Johnson Clinical Diagnostics, Inc. Improved method of detecting pre-spotting when dispensing sample
EP1093856A1 (en) * 1999-10-21 2001-04-25 Tecan Schweiz AG Replaceable pipette tip and method for producing the same, associated pipette-head and pipetting system
US6431015B1 (en) 1999-10-21 2002-08-13 Tecan Trading Ag Delivery apparatus with interchangeable pipette tip
US6596240B2 (en) 2001-01-12 2003-07-22 Porex Corporation Pipette tip for easy mounting and ejecting from a pipette
EP1618060A2 (en) * 2003-04-30 2006-01-25 Aurora Discovery Inc. Method and system for precise dispensation of a liquid
EP1618060A4 (en) * 2003-04-30 2007-03-21 Aurora Discovery Inc Method and system for precise dispensation of a liquid

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