Method of producing a probe for aspirating and dispensing probe having surface sensing capability

• US 5,843,378 A
• Filed: 01/29/1997
• Issued: 12/01/1998
• Est. Priority Date: 09/05/1995
• Status: Expired due to Fees

• Current Assignee: LJL Biosystems, Inc. (Danaher Corporation)
• Original Assignee: LJL Biosystems, Inc. (Danaher Corporation)
• Inventors: Stellmacher, Rick V., El-Hage, Amer
• Primary Examiner(s): Pyon, Harold Y.
• Application Number:
  US08/790,096
• Time in Patent Office: 671 Days
• Field of Search: 422/50, 422/63, 422/64, 422/65, 422/66, 422/67, 422/99, 422/100, 422/102, 422/103, 422/104, 73/863.32, 73/864.01, 73/864.14, 73/864.21, 436/180
• US Class Current: 222/1
• CPC Class Codes: G01F 23/24 by measuring variations of resistance of resistors due to contact with conductor fluid
• CPC Class Codes: G01F 23/245 with a probe moved by an auxiliary power, e.g. meter, to follow automatically the level
• CPC Class Codes: G01N 2035/1025 Fluid level sensing
• CPC Class Codes: G01N 35/1009 Characterised by arrangements for controlling the aspiration or dispense of liquids
• CPC Class Codes: Y10T 436/2575 Volumetric liquid transfer

Abstract

A method of producing a probe for aspirating and dispensing liquid. A fluid conduit and rod are positioned in the central bore of a tube so that an inlet end of the conduit and a contact end of the rod protrude from an upper end of the tube and a discharge end of the conduit and a sensing end of the rod protrude from a lower end of the tube. The tube has a heat-shrinkable outer layer and a meltable inner layer. The tube is heated so that its outer layer shrinks and its inner layer melts to encapsulate middle portions of the conduit and rod. A circuit board having first and second traces and first and second holes is placed on the upper end of the tube so that the inlet end of the conduit is inserted through the first hole and the contact end of the rod is inserted through the second hole. The conduit and rod are attached to the board so that the conduit is electrically connected to the first trace and the rod is electrically connected to the second trace. First and second conducting pins are also attached to the board. The conducting pins electrically connect the traces to a voltage sensing circuit when the probe is attached to a probe positioning device.

Claims

1. A method of producing a probe for aspirating and dispensing liquid, the method comprising the steps of:

a) providing an electrically insulative tube, an electrically conductive fluid conduit, and an electrically conductive rod, the tube having upper and lower ends, a heat-shrinkable outer layer, a meltable inner layer, and a central bore extending the length of the tube, the inner layer having a lower melting point than the outer layer, the conduit having an inlet end, a discharge end, and a middle section between the inlet and discharge ends, and the rod having a contact end, a sensing end, and a middle portion between the contact and sensing ends;

b) positioning the conduit and the rod in the central bore such that the inlet end of the conduit and the contact end of the rod protrude from the upper end of the tube and such that the discharge end of the conduit and the sensing end of the rod protrude from the lower end of the tube; and

c) heating the tube such that the outer layer shrinks and the inner layer melts to encapsulate the middle section of the conduit and the middle portion of the rod, wherein the outer layer shrinks and the inner layer melts to form in the tube a longitudinal waist between the conduit and the rod, and wherein the middle section of the conduit and the middle portion of the rod are encapsulated such that the conduit is electrically insulated from the rod.

7. The method of claim 1, wherein the inner and outer layers comprise chemically inert polymeric materials.

8. The method of claim 1, wherein the outer layer comprises tetrafluoroethylene.

9. The method of claim 1, wherein the inner layer comprises a material selected from the group consisting of fluorinated ethylene propylene and perfluoroalkoxy.

10. The method of claim 1, wherein the tube is heated at a temperature in the range of 170°

to 210°

C. for about 0.5 hours.

11. The method of claim 1, wherein the conduit and the rod are positioned in the tube such that the discharge end of the conduit protrudes a first offset distance from the lower end of the tube and such that the sensing end of the rod protrudes a second offset distance from the lower end of the tube, and wherein the difference between the first and second offset distances is non-zero.

12. The method of claim 11, wherein the difference between the first and second offset distances is in the range of 0.25 mm to 1.0 mm.

2. The method of claim 16, further comprising the steps of:

a) providing a board having a first hole for receiving the inlet end of the conduit, a second hole for receiving the contact end of the rod, and first and second electrically conductive traces, wherein the traces are electrically insulated from each other;

b) inserting the inlet end of the conduit through the first hole and the contact end of the rod through the second hole;

c) attaching the conduit and the rod to the board such that the conduit is electrically connected to the first trace and such that the rod is electrically connected to the second trace; and

d) attaching to the board first and second conducting pins for electrically connecting the traces to a voltage sensing circuit, wherein the pins are attached to the board such that the first and second pins are electrically connected to the first and second traces, respectively, and such that the first and second pins are electrically insulated from each other.

3. The method of claim 2, wherein the board comprises a printed circuit board.

4. The method of claim 2, wherein the board has a top surface and a bottom surface, the traces are located on the top surface, the pins are attached to the top surface, and the conduit and the rod are attached to the board such that the bottom surface of the board contacts the upper end of the tube.

5. The method of claim 2, wherein the board has a diameter larger than the diameter of the tube to facilitate attachment of the probe to a probe positioning device.

6. The method of claim 2, wherein the conduit, the rod, and the pins are soldered to the board.