Electrical heating assembly

1. An electrical heating assembly ( 2 ) comprising: a glass-ceramic cooking plate ( 4 ) having an upper surface ( 6 ) for receiving a cooking vessel ( 8 ) and a lower surface ( 10 ); a radiant electric heater ( 12 ) incorporating at least one electric heating element ( 20 ), the heater ( 12 ) being supported in contact with the lower surface of the cooking plate ( 4 ); circuit means; and temperature sensing means ( 29 ) spaced above the at least one heating element ( 20 ), wherein the temperature sensing means ( 29 ) comprises: a support member ( 33 ) having provided on an upper surface thereof so as to contact the lower surface of the cooking plate ( 4 ) a temperature-sensitive electrical resistance element ( 30 ) of film form and provided with electrical connecting leads ( 34 ) arranged for electrical connection to said circuit means, said circuit means being constructed to monitor the electrical resistance of the film form temperature-sensitive electrical resistance element ( 30 ) as a function of temperature of the shielded region of the lower surface ( 10 ) of the cooking plate ( 4 ) with which it is in contact and hence as a function substantially of temperature of a cooking vessel ( 8 ) located on the upper surface ( 6 ) of the cooking plate ( 4 ) and overlying the shielded region; and thermal insulation means ( 40 ) adapted and arranged to shield the support member ( 33 ) and a corresponding region of the lower surface ( 10 ) of the cooking plate ( 4 ) from direct thermal radiation from the at least one electric heating element ( 20 ).

2. An assembly as claimed in claim 1 , wherein the support member ( 33 ) comprises a high-temperature resistant material.

3. An assembly as claimed in claim 2 , wherein the support member ( 33 ) comprises a ceramic material.

4. An assembly as claimed in claim 3 , wherein the support member ( 33 ) is selected from alumina and cordierite.

5. An assembly as claimed in claim 1 , wherein the support member ( 33 ) extends from a periphery of the heater ( 12 ) towards a central region thereof.

6. An assembly as claimed in claim 5 , wherein the electrical connecting leads ( 34 ) are arranged to extend from the film form temperature-sensitive electrical resistance element ( 30 ) at least to a peripheral region of the heater ( 12 ).

7. An assembly as claimed in claim 1 , wherein the support member ( 33 ) is provided in a central region of the heater ( 12 ).

8. An assembly as claimed in claim 1 , wherein the support member ( 33 ) is supported from below.

9. An assembly as claimed in claim 1 , wherein the electrical connecting leads ( 34 ) are of film form.

10. An assembly as claimed in claim 9 , wherein the electrical connecting leads ( 34 ) are provided on the upper surface of the support member ( 33 ).

11. An assembly as claimed in claim 1 , wherein the film form component ( 30 ) is of thick film form.

12. An assembly as claimed in claim 11 , wherein the film form component ( 30 ) is screen-printed and fired onto the upper surface of the support member ( 33 ).

13. An assembly as claimed in claim 11 , wherein the thick film component comprises an electrically conductive phase selected from platinum, gold, silver, palladium, nickel and alloys thereof.

14. An assembly as claimed in claim 1 , wherein the film form component ( 30 ) is of thin film form.

15. An assembly as claimed in claim 14 , wherein the film form component ( 30 ) is sputtered onto the upper surface of the support member ( 33 ).

16. An assembly as claimed in claim 14 , wherein the thin film component comprises platinum.

17. An assembly as claimed in claim 1 , wherein the thermal insulation means ( 40 ) is of a form selected from pad and block form in contact with the support member ( 33 ).

18. An assembly as claimed in claim 17 , wherein the thermal insulation means ( 40 ) is provided with a shallow recess for accommodating the support member ( 33 ).

19. An assembly as claimed claim 1 , wherein the thermal insulation means ( 40 ) is secured to the lower surface of the support member ( 33 ).

20. An assembly as claimed in claim 1 , wherein the thermal insulation means ( 40 ) is selected from vermiculite, microporous, ceramic fibre and calcium silicate materials.

21. An assembly as claimed in claim 1 , wherein the thermal insulation means ( 40 ) has an external surface ( 44 ) provided with a layer of thermal radiation-reflecting material.

22. An assembly as claimed in claim 1 , wherein the radiant electric heater ( 12 ) comprises a dish-like support ( 14 ) accommodating the at least one electric heating element ( 20 ) and having a peripheral wall ( 18 ) of thermal insulation material contacting the lower surface ( 10 ) of the glass-ceramic cooking plate ( 4 ).

23. An assembly as claimed in claim 22 , wherein the support member ( 33 ) passes through a recess formed in the upper surface of the peripheral wall ( 18 ).

24. An assembly as claimed in claim 22 , wherein the support member ( 33 ) is secured to the dish-like support ( 14 ).

25. An assembly as claimed in claim 24 , wherein the support member ( 33 ) is secured to the dish-like support ( 14 ) by way of a mounting bracket ( 31 ) secured to the side of the dish-like support ( 14 ).

26. An assembly as claimed in claim 1 , wherein an electrically insulating layer is provided on the upper surface of the support member ( 33 ).

27. An assembly as claimed in claim 26 , wherein the electrically insulating layer is of film form.

28. An assembly as claimed in claim 1 , wherein a temperature-responsive means ( 46 ) is additionally provided to sense temperature of a region of the glass-ceramic cooking plate ( 4 ) subjected to direct thermal radiation from the at least one electric heating element ( 20 ) and adapted to de-energise the at least one electric heating element ( 20 ) when a predetermined maximum operating temperature is reached by the cooking plate ( 4 ).

29. An assembly as claimed in claim 9 , wherein the film form leads ( 34 ) are of thick film form.

30. An assembly as claimed in claim 29 , wherein the film form leads ( 34 ) are screen-printed and fired onto the upper surface of the support member ( 33 ).

31. An assembly as claimed in claim 29 , wherein the thick film leads ( 34 ) comprise an electrically conductive phase selected from platinum, gold, silver, palladium, nickel and alloys thereof.

32. An assembly as claimed in claim 9 , wherein the film form leads ( 34 ) are of thin film form.

33. An assembly as claimed in claim 32 , wherein the film form leads ( 34 ) are sputtered onto the upper surface of the support member ( 33 ).

34. An assembly as claimed in claim 32 , wherein the thin film leads ( 34 ) comprise platinum.

35. An assembly as claimed in claim 1 , wherein the thermal insulation means ( 40 ) is held in contact with the lower surface of the support member ( 33 ).