Solid plate heating unit

Claim 2

A plate surface heating unit having a top plate defining a heating area, said top plate having a softening temperature, temperature setting means for determining the operating temperature of said top plate including a control system for maintaining said heating area substantially at the selected cooking temperature while maintaining the temperature of said heating area below the softening temperature of said top plate comprising: a metal sheathed electrical resistance heating element in intimate contact with the underside of said top plate, said element having a heating capacity capable of elevating the temperature of said top plate above its softening temperature; a temperature-sensing means arranged for sensing the temperature of said top plate at a plurality of selected locations in said heating area; cycling means in said temperature setting means operable to control energization of said heating element to maintain the temperature of said top plate at said operating temperature; a control means in circuit connection between said temperature sensing means and said temperature setting means for deenergizing said heating element independent of said cycling means when the temperature sensed by said temperature sensing means of said top plate and said heating element at said selected locations of said heating area reaches a selected temperature below the softening temperature of said top plate.

Claim 3

The plate surface heating unit recited in claim 1 wherein said temperature sensing means are positioned to sense the temperature of said heating element and the adjacent area of said top plate.

Claim 4

The plate surface heating unit recited in claim 2 wherein said control means further includes means for averaging the temperature sensed by said temperature sensing means at said plurality of selected locations for producing an average temperature signal.

Claim 5

The plate surface heating unit recited in claim 3 wherein said control means further includes power switch means connected to be responsive to said average temperature signal for controlling operation of said heating elements independent of said temperature setting means when the temperature of said top plate approaches said softening temperatures.

Claim 6

A plate surface heating unit having an aluminum top plate defining a heating area, temperature setting means for determining the operating temperature of said top plate including a control system for maintaining said heating area substantially at the selected cooking temperature while maintaining the temperature of said heating area below a selected maximum temperature comprising: a first metal sheathed electrical resistance heating element in intimate contact with the underside of said top plate in the central portion of said heating area; a second metal sheather electrical resistance heating element in intimate contact with the underside of said top plate being arranged externally of said first heating element in the outer portion of said heating area; a first temperature-sensing means arranged for sensing the temperature of said top plate and said first heating element at a plurality of selected locations in the central portion of said heating area; a second temperature sensing means arranged for sensing the temperature of said top plate and said first heating element at a plurality of selected locations in the outer portion of said heating area; a first control means in circuit connection between said first temperature sensing means and said temperature setting means for deenergizing said first heating element when the temperature sensed by said first temperature sensing means of said top plate and said first heating element at said selected locations in the central portion of said heating area reaches said maximum selected temperature; a second control means in circuit connection between said second temperature sensing means and said temperature setting means for deenergizing said second heating element when the temperature sensed by said second temperature sensing means of said top plate and said second heating element at said selected locations in the outer portion of said heating area reaches said maximum selected temperature; and cycling means in said temperature setting means operable to control energization of said first and second heating elements to maintain the temperature of said top plate at said operating temperature independent of said first and second control means.

Claim 7

A plate surface heating unit having an aluminum top plate defining a heating area, temperature setting means for determining the operating temperature of said top plate including a control system for maintaining said heating area substantially at the selected cooking temperature while maintaining the temperature of said heating area below a selected maximum temperature comprising: a first metal sheathed electrical resistance heating element in intimate contact with the underside of said top plate in the central portion of said heating area; a second metal sheather electrical resistance heating element in intimate contact with the underside of said top plate being arranged externally of said first heating element in the outer portion of said heating area; a first temperature-sensing means arranged for sensing the temperature of said top plate and said first heating element at a plurality of selected locations in the central portion of said heating area; a second temperature sensing means arranged for sensing the temperature of said top plate and said first heating element at a plurality of selected locations in the outer portion of said heating area; a first control means in circuit connection between said first temperature sensing means and said temperature setting means for deenergizing said first heating element when the temperature sensed by said first temperature sensing means of said top plate and said first heating element at said selected locations in the central portion of said heating area reaches said maximum selected temperature; a second control means in circuit connection between said second temperature sensing means and said temperature setting means for deenergizing said second heating element when the temperature sensed by said second temperature sensing means of said top plate and said second heating element at said selected locations in the outer portion of said heating area reaches said maximum selected temperature; and cycling means in said temperature setting means operable to control energization of said first and second heating elements to maintain the temperature of said top plate at said operating temperature independent of said first and second control means.

Claim 8

The plate surface heating unit recited in claim 5 wherein said temperature sensing means associated with said first and second heating elements are positioned to sense the temperature of said heating element and the adjacent area of said top plate.

Claim 9

The plate surface heating unit recited in claim 6 wherein said first and second control means further includes means for averaging the temperature sensed by said first and second temperature sensing means for producing an average temperature signal.

Claim 10

The plate surface heating unit recided in claim 7 wherein said first and second control means further includes power switch means responsive to said average temperature signal for controling energization of said first and second heating elements.