Closed loop heating control for food warmer

• US 6,414,283 B1
• Filed: 08/18/1999
• Issued: 07/02/2002
• Est. Priority Date: 08/18/1999
• Status: Expired due to Term

• Current Assignee: Cooking Solutions Group, Inc. (Middleby Corporation)
• Original Assignee: Ultrafryer Systems Inc.
• Inventors: McNamara, Albert C.
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US09/376,508
• Time in Patent Office: 1,049 Days
• Field of Search: 219/483-486, 219/411-415, 219/396, 219/395, 219/388, 392/416, 307/39-41
• US Class Current: 219/486
• CPC Class Codes: A47J 37/0635 with reflectors
• CPC Class Codes: F24C 7/087 of electric circuits regulating heat
• CPC Class Codes: G01K 13/10 for measuring temperature within piled or stacked materials by special arrangements for conducting heat from the object to the sensitive heat element G01K1/16
• CPC Class Codes: G01K 2207/06 for preparation purposes
• CPC Class Codes: G05D 23/1909 whose output amplitude can only take two discrete values
• CPC Class Codes: H05B 3/0076 for cooking, e.g. in ovens lamps specially adapted for non-metallic cooking plates H05B3/742, H05B3/744

Abstract

A food warmer having closed loop heating control has a temperature sensor in a warming zone of the food warmer. The temperature sensor has a rate of heat absorption and a rate of heat loss substantially the same as a food product contained in the warming zone. First and second heat sources provide heat to the warming zone. The heat required to maintain the warming zone at a desired temperature requires heat from both the first and second heat sources. The first heat source is operated continuously while the second heat source is activated and deactivated in closed loop fashion based on input from the temperature sensor to maintain a desired set point temperature of the warming zone.

Claims

1. A heating control for a food warmer comprising, in combination:

a housing having a warming zone;

a temperature sensor in the warming zone having a rate of heat absorption and a rate of heat loss substantially the same as a selected food product;

a first heat and light source to provide heat continuously to the warming zone; and

a second heat source to provide heat to the warming zone in intermittent fashion to maintain a desired set point temperature of the warming zone;

wherein the heat required to maintain the warming zone at a desired temperature requires heat from both the first heat source and the second heat source.

2. The heating control according to claim 1, wherein the first heat source is oriented to project heat over substantially the entire warming zone.

3. The heating control according to claim 1, wherein the second heat source is oriented to project heat over substantially the entire warming zone.

4. The heating control according to claim 1, further comprising a controller responsive to a signal from the temperature sensor to activate and deactivate the second heat source to maintain a desired set point temperature of the warming zone.

5. The heating control according to claim 1, wherein the temperature sensor has a shape substantially the same as a selected food product.

6. The heating control according to claim 1, wherein the temperature sensor has a surface texture substantially the same as a surface texture of a selected food product.

7. The heating control according to claim 1, wherein the first heat source comprises a plurality of quartz lamps.

8. The heating control according to claim 1, wherein the first heat source comprises two rows of lamps, the second heat source being positioned between the two rows of lamps.

9. The heating control according to claim 1, wherein the second heat source comprises a radiant heater.

10. The heating control according to claim 1, wherein the temperature sensor includes a thermocouple.

11. The heating control according to claim 1, wherein the temperature sensor is contained within a base member, the base member having a shape substantially the same as a shape of a selected food product.

12. The heating control according to claim 1, wherein the temperature sensor is secured to a surface of a base member, the base member having a shape substantially the same as a shape of a selected food product.

13. The heating control according to claim 1, further comprising a plurality of reflectors, each reflector adjacent one of a light source and a radiant heat source to reflect light and heat toward the warming zone.

14. A heating control for a food warmer comprising, in combination:

a housing having a warming zone;

a temperature sensor in the warming zone;

a light source to warm and illuminate food product contained in the warming zone;

the light source being operated continuously while food product is in the warming zone

a radiant heater to warm food product in the warming zone, the heat required to maintain the food product at a desired temperature requiring heat from both the light source and the radiant heater; and

a closed loop controller responsive to a signal from the temperature sensor to control operation of the radiant heater to maintain a desired set point temperature of the warming zone.

15. The heating control according to claim 14, wherein the temperature sensor absorbs heat and transmits heat in substantially the same manner as a selected food product.

16. A heating control for a food warmer comprising, in combination:

a housing having a hood and a base, the base having a warming zone;

a temperature sensor in the warming zone;

a plurality of lamps secured to the hood, to provide light and heat to food product contained in the warming zone, the lamps being operated continuously while food product is in the warming zone;

a plurality of lamp reflectors, each of the lamp reflectors being positioned adjacent a lamp to direct light and heat toward the warming zone;

a radiant heater secured to the hood, to provide heat to warm the food product in the warming zone, the heat required to maintain the food product at a desired temperature requiring heat from both the lamps and the radiant heater;

a radiant heater reflector adjacent the radiant heater to direct heat toward the warming zone; and

a closed loop controller responsive to a signal from the temperature sensor to control operation of the radiant heater to maintain a desired set point temperature of the warming zone.

17. A heating control for a food warmer comprising, in combination:

a housing having a warming zone;

a temperature sensor in the warming zone having a rate of heat absorption and a rate of heat loss substantially the same as a selected food product;

a light source to continuously warm and illuminate a food product in the warming zone;

a radiant heater to warm a food product in the warming zone; and

a closed loop controller responsive to a signal from the temperature sensor to control operation of the radiant heater to maintain a desired set point temperature of the warming zone.