Measuring and testing – Liquid level or depth gauge – Immersible electrode type
Reexamination Certificate
1998-09-01
2001-04-10
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Immersible electrode type
C073S864110, C073S291000, C422S105000, C422S106000, C422S063000
Reexamination Certificate
active
06212949
ABSTRACT:
The present invention relates to an automated immunoassay processing system.
When biological, chemical or biochemical products are tested or analysed, these products may be dispensed into cells in reaction trays to enable analysis of the various products to be performed. After a reagent or a plurality of reagents have been dispensed into the cells in the reaction tray, the reagents are then left for a period of time to allow incubation of a biological process or for a chemical reaction or the like to occur.
After this period of time it is necessary to remove the reagent from the cells and wash the cells so that further analysis may be performed. The washing of the cells in the reaction tray is conventionally performed by separate means to the means which dispenses reagent.
After the incubation period, it is desirable to ascertain whether the correct amount of reagent has actually been dispensed into the cells of the reaction tray; otherwise the desired process or reaction may not have occurred. Once the reagent level has been checked, the reagent is aspirated from the cell. It may also be desirable to check that all of the reagent has been removed from the cells before commencing a washing cycle. During the washing cycle it is also desirable to be able to detect whether the correct amount of washing or cleaning fluid has been dispensed into the cells of the reaction trays and to determine whether all the washing fluid has been removed at the end of the washing cycle.
Conventionally apparatus used to clean the cells of a reaction tray, for example after an incubation period, consists of a washer head with a dispensing tip and an aspirate tip corresponding to each cell.
GB-2216260 discloses a device for injecting a fixed quantity of liquid into a reaction tray wherein conductive electrodes are positioned on an injection nozzle and a detecting unit cooperates with the electrodes to detect the surface level of a sample liquid.
U.S. Pat. No. 4,451,433 discloses an automatic chemical reaction analyzer wherein samples are sequentially dispensed into a reaction tray via a first pipetting tube. Reagent solutions are supplied to the reaction trays via a second, conductive, pipetting tube. The liquid levels of the solutions in the reaction trays are detected by a liquid level sensor formed by the second pipetting tube and a conductive electrode.
The object of the present invention is to provide a new and improved automated immunoassay processing system.
According to the present invention there is provided An automated immunoassay processing system including a level sensor, comprising:
a head mounted for vertical movement, said head comprising an aspirate tip having an internal flow passage within and along which first and second electrode means are provided, the electrode means being connected to a detector circuit arranged to give an output signal when the electrode means are bridged by fluid;
aspirating means connected to the aspirate tip;
a motor for moving the head;
a positioning circuit for controlling the motor to position the head at specified vertical positions; and
control means connected to receive the output signal of the detector circuit;
characterised in that:
the aspirating means is arranged to aspirate whilst the head is being lowered towards the surface of the fluid;
the first and second electrode means are sequentially positioned so that in use fluid passes through said first electrode means before passing through said second electrode means; and
the control means is arranged to produce an indication of the level or volume of fluid in a reaction cell by reference to a vertical position signal when the detector circuit gives an output signal on the aspirate tip coming into contact with fluid in the reaction cell and to generate an output indicating the presence of fluid passing between said first and second electrode means whilst the fluid is being aspirated from the reaction cell.
REFERENCES:
patent: 4803050 (1989-02-01), Mack
patent: 5178834 (1993-01-01), Kagayama et al.
patent: 5736413 (1998-04-01), Uzan et al.
patent: 5897837 (1999-04-01), Mizuno
patent: 5948359 (1999-09-01), Kalra et al.
Higgs Paul Anthony
Inder David John
Le Feuvre Peter John
Casey, Esq. Donald C.
Cygan Michael
Dynex Technologies (Guernsey) Ltd.
Williams Hezron
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