Gas sensor

• US 20070181423A1
• Filed: 08/12/2004
• Published: 08/09/2007
• Est. Priority Date: 08/13/2003
• Status: Active Grant

• Current Assignee: City Technology Ltd. (Honeywell International Inc.)
• Original Assignee: Anglo European Design Engineers Limited
• Inventors: Collins, Graham
• Granted Patent: US 8,691,066 B2
• Time in Patent Office: Days
• US Class Current: 204/400
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors
• CPC Class Codes: G01N 33/0011 Sample conditioning in general G01N1/28

Abstract

A current collector wire (1) is over-moulded with a seal (2) made from a thermoplastic elastomer (Santoprene 64) having a (64) Shore A hardness rating. In a three electrode carbon monoxide sensor three current collector wire (1a, 1b, 1c) and seal (2a, 2b, 2c) combinations are inserted into the body (3) through receiving apertures (12a, 12b, 12c) in a side wall of the body, so that the current collectors protrude through connection apertures (12a, 12b and 12c). The outside diameters of the seals and the bores of the apertures are dimensioned to provide an interference fit of the one in the other. The seals are pressed home into receiving apertures in the body (3) to provide compression of the seals against both current collectors and the aperture bores resultant from the interference. Gold-plated phosphor bronze clips (8) are attached which locate on and are retained by barbs on the housing, thereby trapping the current collector wires and providing electrical contact to external circuitry.

Claims

1. A current collector and seal combination for an electrochemical sensor having a housing, in which are located sensing and counter electrodes in contact with a liquid electrolyte, and connection apertures in a wall of the housing, the current collector and seal combination including:

a flexible current collector adapted for direct contact with one of the sensor'"'"'s electrodes and

a compliant seal adapted to fit in the one of the connection apertures, the current collector extending through the compliant seal,

the seal being in contact with the collector substantially throughout its length along the current collector and

the seal being of an elastomeric material,

the arrangement being such that compressive stress induced in the seal by reaction from the connection aperture urges the seal into distributed sealing contact with the current collector substantially throughout the length of the seal.

2. The current collector and seal combination of claim 1, wherein the seal is longer than its outer diameter or other major cross-sectional dimension.

3. The current collector and seal combination of claim 2, wherein the ratio of the seal length to outer diameter is of the order of 3:

1 at least.

4. The current collector and seal combination of claim 1, claim 2 or claim 3, wherein the ratio of the length and/or the diameter of the seal to the diameter of the current collector is at least of the order of 10:

1.

5. The current collector and seal combination of claim 1, claim 2, or claim 3, wherein the ratio of the length of the seal to the diameter of the current collector is at least of the order of 30:

1.

6. The current collector and seal combination of claim 1, wherein the compliant seal is injection moulded as an over-moulding onto the current collector.

7. The current collector and seal combination of claim 1, wherein the compliant seal is moulded with a central through-bore for threading of the current collector through it.

8. The current collector and seal combination of claim 1, wherein the compliant seal is moulded with a slot, nick or notch, for introduction of the current collector into it.

9. The current collector and seal combination of claim 1, wherein the compliant seal is moulded as two complementary halves having a central groove for receiving the current collector.

10. The current collector and seal combination of claim 1, wherein the seal has one or more ridges extending around its outer circumference.

11. The current collector and seal combination of claim 1, wherein the seal has a cylindrical body and a larger diameter outer end boss.

12. The current collector and seal combination of claim 1, wherein the seal has a tapered nose.

13. An electrochemical gas sensor having:

a housing having at least one wall and a plurality of connection apertures through the wall, the apertures having bores,

sensing and counter electrodes in the housing,

a liquid electrolyte contained in the housing in chemical contact with the electrodes, and

a plurality of current collectors in electrical contact with respective ones of the respective electrodes;

the plurality of current collectors and respective electrodes characterized in that;

the plurality of current collectors in combination with a corresponding plurality of compliant seals are arranged in accordance with the current collector and seal combination of claim 1;

wherein the current collectors extend within their seals through respective ones of the apertures from their electrodes to outside the housing; and

the compliant seals are in compression against both their current collectors and at least part of the bores of their apertures,

whereby the current collectors provide means for electrical contact outside the housing and the apertures are sealed.

14. The electrochemical sensor of claim 12, wherein the seal is an interference fit in the aperture.

15. The electrochemical sensor of claim 12 or claim 13, wherein the seals have cylindrical bodies and the larger diameter outer end bosses and the connection apertures have a complementary shape.

16. The electrochemical sensor of claim 12, claim 13 or claim 14, including metallic end caps clipped to the housing and captivating the current collectors, thereby providing electrical connections for the sensor.

17. An electrochemical gas sensor having:

a housing having at least one wall and a plurality of connection apertures through the wall, the apertures having bores,

sensing and counter electrodes in the housing,

a liquid electrolyte contained in the housing in chemical contact with the electrodes, and

a plurality of current collectors in electrical contact with respective ones of the respective electrodes;

the plurality of current collector and respective electrodes characterized in that;

the plurality of current collectors in combination with a corresponding plurality of compliant seals are arranged in accordance with the current collector and seal combination of claim 1, wherein

the current collectors extend through respective ones of the apertures from their electrodes to outside the housing;

the compliant seals are in compression against both their current collectors and at least part of the bores of their apertures, whereby the current collectors provide means for electrical contact outside the housing and the apertures are sealed;

the current collects are preliminarily located in the connection apertures;

the compliant seals are back-fillings of sealing material into the connection apertures; and

the back-fillings are compressed by end caps.

18. The electrochemical sensor of claim 17, wherein the end caps are metallic, clipped to the housing, and captivate the current collectors, thereby providing electrical connections for the sensor.

19. The electrochemical sensor of claim 13, or claim 17, wherein the elastic modulii of the housing and of the seal differ by at least two orders of magnitude, the housing being stiffer and the seal being more compliant.

20. A method of manufacturing a current collector and seal combination for an electrochemical sensor, the method comprising the steps of:

moulding a seal about the current collector using an injection moulding tool;

indexing the current collector and moulded seal with respect to the tool; and

repeating the moulding process.

21. A method of manufacturing a current collector and seal combination for an electrochemical sensor, the method comprising the steps of:

moulding a sensor housing wall with a connection aperture about the current collector using an injection moulding tool, the current collector being free in the connection aperture; and

moulding a compliant seal in the connection aperture.