Heating unit and control system for cooktops having capability to detect presence of a pan and methods of operating same

• US 6,492,627 B1
• Filed: 07/26/2001
• Issued: 12/10/2002
• Est. Priority Date: 07/26/2001
• Status: Expired due to Fees

• Current Assignee: Emerson Electric Company
• Original Assignee: Emerson Electric Company
• Inventors: Ensinger, James W., Peterson, Gregory A.
• Primary Examiner(s): PAIK, SANG YEOP
• Application Number:
  US09/915,897
• Time in Patent Office: 502 Days
• Field of Search: 219/446.1, 219/447.1, 219/448.11, 219/448.12, 219/448.13, 219/460.1, 219/490, 219/497, 219/507, 219/509, 219/518, 219/620, 219/621, 219/626
• US Class Current: 219/518
• CPC Class Codes: H05B 2213/05 Heating plates with pan detection means
• CPC Class Codes: H05B 3/746 Protection, e.g. overheat cutoff, hot plate indicator

Abstract

The present invention provides a control system for a heating unit in a cooktop that is capable of detecting the presence (or absence) of a cooking pan or utensil. The heating unit has a spirally wound ribbon heater element and may be mounted below a glass-ceramic cooking surface. The control system includes a pan detection unit electrically connected to the heater element. The pan detection unit generates a high frequency signal through the heater element to determine whether a pan is present on the cooktop. The pan detection unit may have an oscillation circuit to generate the high frequency signal through the heater element. In one embodiment, the control system further includes at least one switch device that is connected between the heater element and a power source. The switch device is opened to remove the heater element from the power source when the pan detection unit generates the high frequency signal through the heater element. The present invention also includes a heating unit having dual heater units to determine the size of the pan placed on the cooktop. The present invention further includes methods of operating a heater unit and control system having the capability of detecting the presence of a pan.

Claims

1. A control system for a heating unit in a cooktop, the heating unit having a spirally wound ribbon heater element, the control system comprising a pan detection unit electrically connected to the heater element, wherein the pan detection unit is capable of generating a high frequency signal through the heater element to determine whether a pan is present on the cooktop.

2. The control system of claim 1, wherein the cooktop has a glass-ceramic cooking surface, the heating unit and heater element mounted below the glass-ceramic cooking surface.

3. The control system of claim 1, wherein the pan detection unit has an oscillation circuit to generate the high frequency signal through the heater element.

4. The control system of claim 1, wherein the control system further includes an electronic control unit that is electrically connected to the pan detection unit, the electronic control unit capable of generating a signal to the pan detection unit to enable the pan detection unit to generate the high frequency signal through the heater element.

5. The control system of claim 4, wherein the pan detection unit is capable of sending a response signal to the electronic control unit after the electronic control unit sends the signal to the pan detection unit to enable the pan detection unit to generate the high frequency signal through the heater element.

6. The control system of claim 5, wherein the response signal from the pan detection unit to the electronic control unit reflects at least a portion of a reactance of the heater element.

7. The control system of claim 4, wherein the control system further includes a user interface that is electrically connected to the electronic control unit, the user interface capable of receiving a setting from a user of the cooktop.

8. The control system of claim 4, wherein the control system further includes a first switch device and a second switch device connected between the heater element and a power source, the first and second switch devices being electronically controlled by the electronic control unit.

9. The control system of claim 8, wherein the first switch device is a triac.

10. The control system of claim 9, wherein the first switch device is opened to remove the power source from the heater element when the pan detection unit generates the high frequency signal through the heater element.

11. A control system for a heating unit in a cooktop, the heating unit having a heater element, the heater element having a first terminal end and a second terminal end, the control system comprising:

a pan detection unit electrically connected to the first and second terminal ends of the heater element, the pan detection unit capable of generating a high frequency signal through the heater element to determine whether a pan is present on the cooktop; and

a switch device electrically connected between the heater element and a power source;

wherein the switch device is opened to remove the power source from the heater element when the pan detection unit generates the high frequency signal through the heater element.

12. The control system of claim 11, wherein the cooktop has a glass-ceramic cooking surface, the heating unit and heater element mounted below the glass-ceramic cooking surface.

13. The control system of claim 11, wherein the pan detection unit has an oscillation circuit to generate the high frequency signal through the heater element.

14. The control system of claim 11, wherein the control system further includes an electronic control unit that is electrically connected to the pan detection unit, the electronic control unit capable of generating a signal to the pan detection unit to enable the pan detection unit to generate the high frequency signal through the heater element.

15. The control system of claim 14, wherein the pan detection unit is capable of sending a response signal to the electronic control unit after the electronic control unit sends the signal to the pan detection unit to enable the pan detection unit to generate the high frequency signal through the heater element.

16. The control system of claim 15, wherein the response signal from the pan detection unit to the electronic control unit reflects at least a portion of a reactance of the heater element.

17. The control system of claim 14, wherein the control system further includes a user interface that is electrically connected to the electronic control unit, the user interface capable of receiving a setting from a user of the cooktop.

18. The control system of claim 11, wherein the switch device is a triac.

19. A control system for a heating unit in a cooktop, the heating unit having an inner heater element and an outer heater element, the inner and outer heater elements being spirally wound wherein the inner heater element is spirally wound within the outer heater element, the control system comprising:

a pan detection unit electrically connected to the inner and outer heater elements, the pan detection unit capable of generating a high frequency signal through the inner heater element to determine whether a pan is present on the cooktop, the pan detection unit further capable of generating a high frequency signal through the outer heater element to determine a size of the pan on the cooktop;

a first switch device electrically connected between the inner heater element and a power source; and

a second switch device electrically connected between the outer heater element and the power source;

wherein the first switch device is opened to remove the power source from the inner heater element when the pan detection unit generates the high frequency signal through the inner heater element to determine whether the pan is present on the cooktop, and the second switch device is opened to remove the power source from the outer heater element when the pan detection unit generates the high frequency signal through the outer heater element to determine the size of the pan on the cooktop.

20. The control system of claim 19, wherein the cooktop has a glass-ceramic cooking surface, the heating unit and heater element mounted below the glass-ceramic cooking surface.

21. The control system of claim 19, wherein the pan detection unit has at least one oscillation circuit to generate the high frequency signals through the inner and outer heater elements.

22. The control system of claim 19, wherein the control system further includes an electronic control unit that is electrically connected to the pan detection unit, the electronic control unit capable of generating a signal to the pan detection u nit to enable the pan detection unit to generate the high frequency signals through the inner and outer heater elements.

23. The control system of claim 22, wherein the pan detection unit is capable of sending a response signal to the electronic control unit after the electronic control unit sends the signal to the pan detection unit to enable the pan detection unit to generate the high frequency signals through the inner and outer heater elements.

24. The control system of claim 23, wherein the response signal from the pan detection unit to the electronic control unit reflects at least a portion of a reactance of either the first or second heater element.

25. The control system of claim 22, wherein the control system further includes a user interface that is electrically connected to the electronic control unit, the user interface capable of receiving a setting from a user of the cooktop.

26. The control system of claim 19, wherein the first switch device and second switch device are triacs.

27. A method of operating a heating unit for a cooktop with a control system that is capable of detecting whether a pan is present on the cooktop, the heating unit having a heater element, the method comprising:

receiving a setting from a user of the cooktop;

generating a high frequency signal through the heater element;

determining whether the pan is present on the cooktop from the generation of the high frequency signal through the heater element;

isolating power to the heater element if it is determined that the pan is not present on the cooktop;

providing power to the heater element if it is determined that the pan is present on the cooktop;

determining whether the pan has been removed from the cooktop after power has been provided to the heater element;

isolating power to the heater element if it is determined that the pan has been removed from the cooktop; and

providing power to the heater element if it is determined that the pan has not been removed from the cooktop.

28. The method of claim 27, wherein the step of generating the high frequency signal through the heater element is performed by a pan detection unit having an oscillation circuit.

29. The method of claim 28, wherein the step of determining whether the pan is present on the cooktop is performed by an electronic control unit that is electrically connected to the pan detection unit.

30. The method of claim 28, wherein the step of determining whether the pan has been removed from the cooktop is performed by an electronic control unit that is electrically connected to the pan detection unit.

31. A control system for a heating unit in a cooktop, the heating unit having a heater element, the heater element having a first terminal end and a second terminal end, the control system comprising:

a means for receiving a setting from a user of the cooktop;

a means for generating a high frequency signal through the heater element;

a means for determining whether a pan is present on the cooktop; and

a means for isolating power to the heater element if it is determined that the pan is not present on the cooktop.

32. The control system of claim 31, wherein the cooktop has a glass-ceramic cooking surface, the heating unit and heater element mounted below the glass-ceramic cooking surface.

33. The control system of claim 31, wherein the means for generating the high frequency signal through the heater element includes at least an oscillation circuit.

34. The control system of claim 31, wherein the control system further includes an electronic control unit that is electrically connected to the means for generating the high frequency signal through the heater element.