Automatic precision non-contact open-loop fluid dispensing

• US 7,396,512 B2
• Filed: 11/04/2003
• Issued: 07/08/2008
• Est. Priority Date: 11/04/2003
• Status: Expired due to Fees

• Current Assignee: DRUMMOND SCIENTIFIC COMPANY
• Original Assignee: DRUMMOND SCIENTIFIC COMPANY
• Inventors: DiTrolio, Nicholas M., Canfield, Eric L.
• Primary Examiner(s): Gordon; Brian R.
• Application Number:
  US10/700,374
• Publication Number:
  US 20050095723A1
• Time in Patent Office: 1,708 Days
• Field of Search: 422/100, 738/633.2, 738/638.3, 738/637.2, 738/638.6, 738/64, 738/640.1, 738/641.1, 738/641.5
• US Class Current: 422/522
• CPC Class Codes: B01L 2200/146 Employing pressure sensors
• CPC Class Codes: B01L 2200/148 Specific details about calibrations
• CPC Class Codes: B01L 2300/027 Digital display, e.g. LCD, LED
• CPC Class Codes: B01L 2400/0487 fluid pressure, pneumatics
• CPC Class Codes: B01L 3/021 Pipettes, i.e. with only one conduit for withdrawing and redistributing liquids
• CPC Class Codes: B01L 3/0213 Accessories for glass pipettes; Gun-type pipettes, e.g. safety devices, pumps
• CPC Class Codes: B01L 3/0227 Details of motor drive means B01L3/0231, B01L3/0234 take precedence
• CPC Class Codes: B01L 3/0234 Repeating pipettes, i.e. for dispensing multiple doses from a single charge
• CPC Class Codes: G01F 13/006 measuring volume in function of time
• CPC Class Codes: G01F 15/005 Valves valves in general F16K
• CPC Class Codes: G01F 15/022 using electrical means
• CPC Class Codes: G01F 15/068 with electrical means G01F15/063 takes precedence
• CPC Class Codes: G01F 23/02 by gauge glasses or other apparatus involving a window or transparent tube for directly observing the level to be measured or the level of a liquid column in free communication with the main body of the liquid
• CPC Class Codes: G01F 25/0092 for metering by volume
• CPC Class Codes: G01F 3/00 Measuring the volume flow of fluids or fluent solid material wherein the fluid passes through the meter in successive and more or less isolated quantities, the meter being driven by the flow measuring a proportion of the volume flow G01F5/00
• CPC Class Codes: Y10T 436/2575 Volumetric liquid transfer

Abstract

A rugged, all-electronic fluid dispensing system for use with pipettes or in other contexts indirectly measures fluid flow by using a non-linear system model to correlate vacuum existing at the top of a column of suspended fluid. Non-contact operation is provided to eliminate the need for contact-type closed-loop fluid flow sensing and associated potential cross-contamination risks. In one particular exemplary non-limiting illustrative implementation, an electronic controller within a gun-shaped, cordless self-contained pipetter housing dynamically calculates valve opening time based on a non-linear equation. Calibration is used to derive equation constants, and column vacuum pressure before the valve is opened is used as the independent variable to derive a valve opening time that will result in accurate dispensing of a desired programmed fluid quantity. Repetitive automatic dispensing with accuracies greater than 1% are possible within the context of a relatively inexpensive portable pipette or device without the need for mechanically-complex positive displacement arrangements.

Claims

1. An electronic, hand held fluid dispensing system for use with a laboratory pipette, comprising:

a housing capable of being held in one hand;

a coupler disposed at least partially within said housing, said coupler being adapted to be removably connected to said pipette;

a source of pressure and/or vacuum;

a valve pneumatically coupled between said source and said coupler;

at least one pressure transducer pneumatically coupled to said coupler, said pressure transducer generating at least one output; and

an electronic controller electrically coupled to control at least said valve and also electrically coupled to said pressure transducer, said electronic controller operating in an open-loop mode to control said valve in accordance with a valve control timing parameter derived from said pressure transducer output and a stored quantity parameter relating to a desired quantity of fluid to be dispensed, said valve control timing parameter controlling said valve so that said system automatically, repetitively dispenses substantially a predetermined quantity of fluid from said pipette.

2. The system of claim 1 wherein said source comprises an electric air pump.

3. The system of claim 1 wherein said source comprises a source of atmospheric pressure.

4. The system of claim 1 wherein said source comprises a source of a pressurized gas.

5. The system of claim 1 wherein said source comprises a reversible electric pump that selectively generates suction and positive pressure, and wherein said electronic controller is coupled to selectively control said pump to generate suction to draw fluid into said pipette.

6. The system as in 1 wherein said hand-held housing is gun-shaped.

7. The system as in 1 wherein said electronic controller dynamically calculates said valve control parameter based on a non-linear mathematical model.

8. The system as in 1 wherein said electronic controller uses a look-up table to ascertain said valve control parameter based in part on measured pressure.

9. The system as in 1 where further including a further pressure transducer that measures pressure between said source and said valve, and wherein said electronic controller is responsive to said second pressure transducer for controlling said source to compensate for variations in the output pressure of said source.

10. The system as in 1 wherein said coupler is adapted to accept pipettes of different sizes.

11. The system as in 1 further including a graphical display disposed on said housing and coupled to said electronic controller.

12. The system as in 1 further including means for allowing an end user to program said desired quantity.

13. The system as in 12 wherein said means comprises first and second push buttons mounted on said housing, said first and second push buttons in one mode of operation being used to program said desired quantity, and in a further mode of operation being used to control aspiration and dispensing rate.

14. The system as in 12 wherein said means comprises software executed by said electronic controller that allows said electronic controller to learn said desired quantity based on user operation of said system.

15. The system as in 1 wherein said system achieves repeatable dispensing accuracies of better than 1%.

16. The system as in 1 wherein said fluid control element comprises an electronic valve with a on/off orifice, and wherein said control parameter controls the duration of opening of said valve orifice.

17. The system as in 1 wherein said fluid control element comprises a valve with a variable orifice, and wherein said control parameter controls the amount said valve orifice is opened.

18. The system as in 1 wherein said electronic controller controls said source to reduce undesired dripping of fluid from said pipette.

19. The system as in 1 wherein said electronic controller derives an indication of the angle of said pipette from vertical.

20. The system as in 1 wherein said electronic controller compensates for different fluid viscosities.