Chemistry: analytical and immunological testing – Including sample preparation – Volumetric liquid transfer
Reexamination Certificate
1999-10-12
2001-12-04
Warden, Jill (Department: 1743)
Chemistry: analytical and immunological testing
Including sample preparation
Volumetric liquid transfer
C422S105000, C073S863320, C073S864010, C073S864110, C222S001000
Reexamination Certificate
active
06326212
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to fluid dispensing apparatus and method for dispensing liquids; and, more particularly, to a membrane actuated fluid dispenser for delivering the fluid through a plurality of pipettes.
2. Related Art
Dispensing apparatuses capable of simultaneously delivering fluid through a plurality of pipettes are well known in the art. One such example is shown in U.S. Pat. No. 3,572,552, to Guinn and No. 3,807,235 to Lefkovits. Both patents use vacuum or pressure only which does not address the diaphragm (membrane) sag problem. When an elastic membrane is clamped down, it attempts to squeeze into available voids. The cavities are available voids and the excess membrane material bunches up in the cavity and sometimes wrinkles and sags into the cavity. This adversely affects the accuracy of the dispensed volume.
In addition, diaphragm blockage of holes is a problem with certain cavity shapes and hole locations. These patents that use a flat surface immediately above or below the cavity are subject to this. When the diaphragm wrinkles or sags, then vacuum or pressure is applied, if the diaphragm has a sag or wrinkle near the hole then the wrinkle or sag gets forced over the hole, thus blocking its operation.
There is an uneven sealing towards the center of the array of cavities that results when a membrane is peripherally clamped between two large flat plates. It is difficult to seal such an arrangement because the large forces required will bend the plates and they will actually lift up in the center, thus unsealing the center cavities.
Membranes that conform to the shape of the chamber as in these prior art patents forego the possibility of variable volume dispensing.
The use of fixed dispensing needles makes cleaning and contamination control much more difficult.
such prior art devices allows the dispensed fluid to enter the cavity. This makes it difficult to clean and control contamination.
There is thus a need for a fluid dispenser which dispenses a liquid through one or more pipettes in a controlled manner.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved apparatus and method for dispensing liquid out of at least one pipette.
It is a further object of this invention to utilize fluid under pressure to flex a membrane against apertured cavities in a plate deforming the membrane into the cavities and out apertures in the cavities into hollow pipettes aligned with the cavities.
It is an object of this invention to carry out the foregoing object by reversing the pumping of fluid thereby drawing liquid into which the pipettes may be disposed up into the pipettes wherein reversing the air pressure ejects the drawn-up liquid out of the pipettes.
These and other objects are preferably accomplished by providing a membrane actuated fluid dispensing head having a dispenser housing with a top plate, a bottom plate, and a fluid distribution plate disposed between the top and bottom plates. The top plate has fluid inlet means therethrough for admitting pressurized fluid over the distribution plate, the bottom plate having a plurality of elongated hollow pipettes mounted thereon extending away from the top plate and in fluid communication with the fluid distribution plate.
A first resilient membrane is disposed between the fluid distribution plate and the bottom plate, the bottom plate having a plurality of spaced cavities thereon having outer peripheries and in fluid communication with the pipettes. A second resilient membrane is disposed between the top plate and the distribution plate having an opening therethrough. The distribution plate has a plurality of spaced apertured members having outer peripheries, some of the outer peripheries of the members substantially coinciding with some of the outer peripheries of the cavities whereby, when a pressurized source of fluid is injected into the dispenser housing via the inlet means, the fluid flows under pressure over through the opening in the second membrane over the distribution plate, out of the apertures in the members and against the membrane forcing portions of the membrane down into the cavities and out the pipettes.
The injection of pressurized fluid can be used to pump fluid out the pipettes, then reversed to draw liquid up into the pipettes (when dipped into a liquid), then reversed again to eject the liquid out the pipettes.
REFERENCES:
patent: 3568735 (1971-03-01), Lancaster
patent: 3650306 (1972-03-01), Lancaster
patent: 4444062 (1984-04-01), Bennett et al.
patent: 4461328 (1984-07-01), Kenny
patent: 4927604 (1990-05-01), Mathus et al.
patent: 5100626 (1992-03-01), Levin
patent: 6039211 (2000-03-01), Slater et al.
patent: 6258324 (2001-07-01), Yiu
Arden Systems, Inc.
Gordon Brian R.
Oppenheimer Wolff & Donnelly LLP
Warden Jill
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