Expandable/retractable thermocouple

1. A thermocouple comprising:

a first housing defining a first interior with an open end;

a second housing having a first end and a second end, wherein the second housing is slidably coupled to the first housing with the first end residing within the first interior and the second end residing exteriorly of the first interior;

a sensor passage extending into the second housing and having an inlet near the first end;

a biasing element provided within the first interior and biasing the second housing out of the first housing;

a temperature sensing element having a non-sensing portion residing within the first interior and a sensing portion residing within the sensor passage; and

a seal fluidly sealing the sensor passage relative to the first interior and configured to prevent fluid from entering the sensor passage and contacting the sensing portion of the temperature sensing element in the sensor passage.

2. The thermocouple of claim 1 wherein the temperature sensing element is independent of the biasing element.

3. The thermocouple of claim 1 wherein the temperature sensing element is inextendible.

4. The thermocouple of claim 1 wherein the biasing element comprises a spring.

5. The thermocouple of claim 4 wherein the spring comprises a coil spring having a first end coupled to the first housing and a second end coupled to the second housing.

6. The thermocouple of claim 5 wherein the temperature sensing element extends through the coil spring.

7. The thermocouple of claim 1 wherein the temperature sensing element is of a fixed length.

8. The thermocouple of claim 7 wherein the non-sensing portion of the temperature sensing element is fixedly coupled to the first housing.

9. The thermocouple of claim 1 wherein the seal is located within the sensor passage.

10. The thermocouple of claim 9 wherein the seal forms a radial seal with the second housing and the temperature sensing element.

11. The thermocouple of claim 10 wherein the temperature sensing element further comprises a wear piece and the seal forms a radial seal with the wear piece.

12. The thermocouple of claim 10 wherein the seal is a C-Shaped ring seal that opens upwardly and has a top end in fluid communication with the first interior.

13. The thermocouple of claim 1 wherein the biasing element comprises a spring having a first end coupled to the first housing and a second end coupled to the second housing, the spring defines a center through which the temperature sensing element passes.

14. The thermocouple of claim 13 wherein the seal comprises a radial seal located within the sensor passage and forms a seal with the second housing and the temperature sensing element.

15. The thermocouple of claim 14 wherein the temperature sensing element comprises a wear piece and the radial seal forms a seal between the wear piece and the temperature sensing element.

16. The thermocouple of claim 15 , further comprising a retaining cap located within the sensor passage to retain the radial seal.

17. The thermocouple of claim 16 wherein the sensor passage has an outlet through which the sensing portion may extend as the second housing slides relative to the first housing.

18. The thermocouple of claim 17 , further comprising a first flange coupled to the first housing for mounting the thermocouple to a first structure.

19. The thermocouple of claim 18 , further comprising a second flange coupled to the second housing for coupling the second housing to a second structure, wherein relative movement between the first and second structures results in a relative sliding of the first and second housings.

20. The thermocouple of claim 19 , further comprising an electrical connector provided on the first housing and electrically connected to the temperature sensing element.