Glass plate surface heating unit with even temperature distribution

Claim 2

A surface-heating unit comprising a plate of glass ceramic material supported on a plate of composite metal sheet material with a center core selected from a group of high thermal conductivity metals and alloys such as copper, silver and aluminum, and an outer skin selected from the group of oxidationand corrosion-resisting metals and alloys such as stainless steel, nickel and chromium, an insulated electrical resistance heating element attached to the underside of the composite plate, a reinforcing member of open framework attached to the underside of the composite plate to prevent warping thereof, a reflector pan supporting the assembly, a releasable trim ring surrounding the assembly and adapted to mount the heating unit in an apertured support panel, and a temPerature-limiting means sensing the temperature of the composite plate and in circuit connection with the heating element to deenergize the heating element at composite plate temperatures somewhere above about 1,000* F.

Claim 3

A surface-heating unit as recited in claim 1 wherein the temperature-limiting means includes a temperature sensor in close thermal contact with the underside of the composite plate and a temperature responder that is supported from the said reflector pan, and connecting means joining the temperature sensor to the temperature responder.

Claim 4

A solid plate, surface-heating unit comprising a top plate of glass ceramic material supported on a plate of composite metal sheet material with a center core selected from a group of high thermal conductivity metals and alloys such as copper, silver and aluminum, and an outer skin selected from the group of oxidation-and corrosion-resisting metals and alloys such as stainless steel, nickel and chromium, an insulated electrical resistance heating element of looped configuration attached to the underside of the composite plate, reinforcing means braced beneath the composite plate to prevent warping thereof, and fastening means for holding the top glass ceramic plate and the composite metal plate firmly together, and a temperature-limiting switch means carried by the unit and having a temperature-sensing probe held in thermal relation with the composite plate, said temperature-limiting switch means being adapted to be connected in a power circuit for the heating element to ensure that the glass ceramic plate does not become overheated, whereby the heating element may be of higher wattage than a heating unit without the temperature-limiting switch so as to reduce the preheat time it takes for the glass ceramic plate to reach a predetermined temperature.

Claim 5

A solid plate, surface-heating unit comprising a top plate of glass ceramic material supported on a plate of composite metal sheet material with a center core selected from a group of high thermal conductivity metals and alloys such as copper, silver and aluminum, and an outer skin selected from the group of oxidation-and corrosion-resisting metals and alloys such as stainless steel, nickel and chromium, an insulated electrical resistance heating element of looped configuration attached to the underside of the composite plate, reinforcing means braced beneath the composite plate to prevent warping thereof, and fastening means for holding the top glass ceramic plate and the composite metal plate firmly together, and a temperature-limiting switch means carried by the unit and having a temperature-sensing probe held in thermal relation with the composite plate, said temperature-limiting switch means being adapted to be connected in a power circuit for the heating element to ensure that the glass ceramic plate does not become overheated, whereby the heating element may be of higher wattage than a heating unit without the temperature-limiting switch so as to reduce the preheat time it takes for the glass ceramic plate to reach a predetermined temperature.

Claim 6

A solid plate, surface-heating unit as recited in claim 3 wherein the composite metal plate distributes the heat from the heating element evenly across the top glass ceramic plate, while in the event of the presence of a warped cooking utensil on the unit, the heat will flow from the hot spots on the top plate to the cold spots by means of the composite metal plate.

Claim 7

A plate-type, surface-heating unit comprising a thin plate of glass ceramic material, a thin flat heat spreader plate bearing against the underside of the glass ceramic plate, said heat spreader plate being of composite metal sheet material with a center core selected from a group of high thermal conductivity metals and alloys such as copper, silver and aluminum, and an outer skin selected from the group of oxidation- and corrosion-resisting metals and alloys such as stainless steel, nickel and chromium, a metal-sheathed resistance heating element of looped configuration attached to the underside of the heat spreader plate, reinforcing means attached to the underside of the heat spreader plate to prevent warpage at elevated temperatures, and temperature-limiting means for controlling the maximum temperature of the glass ceramic plate, said temperature-limiting means comprising a temperature sensor associated with the heating element, and a single-point temperature responder connected to the sensor, and circuit means adapted to join the responder to the heating element such that when the heat spreader plate rises to a predetermined temperature the responder will open the power circuit to the heating element.

Claim 8

A plate-type, surface-heating unit comprising a thin plate of glass ceramic material, a thin flat heat spreader plate bearing against the underside of the glass ceramic plate, said heat spreader plate being of composite metal sheet material with a center core selected from a group of high thermal conductivity metals and alloys such as copper, silver and aluminum, and an outer skin selected from the group of oxidation- and corrosion-resisting metals and alloys such as stainless steel, nickel and chromium, a metal-sheathed resistance heating element of looped configuration attached to the underside of the heat spreader plate, reinforcing means attached to the underside of the heat spreader plate to prevent warpage at elevated temperatures, and temperature-limiting means for controlling the maximum temperature of the glass ceramic plate, said temperature-limiting means comprising a temperature sensor associated with the heating element, and a single-point temperature responder connected to the sensor, and circuit means adapted to join the responder to the heating element such that when the heat spreader plate rises to a predetermined temperature the responder will open the power circuit to the heating element.

Claim 9

A glass ceramic surface unit as recited in claim 5 with electrical grounding means joined to the heat spreader plate.

Claim 10

A glass ceramic surface unit as recited in claim 5 with a high emissivity coating such as porcelain enamel on the top surface of the said heat spreader plate.

Claim 11

A plate-type, surface-heating unit as recited in claim 5 wherein the heating element is of a higher watts density for the diameter of the heating unit than prior heating units that are not protected with temperature-limiting means so as to obtain high heating rates.

Claim 12

A plate-type, surface-heatiNg unit as recited in claim 8 wherein the said heat spreader plate has a high coefficient of thermal conductivity and acts as a temperature equalizer for the glass ceramic plate when the heat in the spreader plate flows from the areas of high temperatures to the areas of lower temperatures thereby obtaining substantially uniform temperature distribution across the heated area of the glass ceramic plate.

Claim 13

A glass ceramic cook top having at least one heated area, each heated area having a heat spreader plate positioned therebeneath and in contact therewith, said heat spreader plate being of composite metal sheet material with a center core selected from a group of high thermal conductivity metals and alloys such as copper, silver and aluminum, and an outer skin selected from the group of oxidation- and corrosion-resisting metals and alloys such as stainless steel, nickel and chromium, a metal-sheathed resistance heating element attached to the underside of the heat spreader plate, reinforcing means braced beneath the heat spreader plate to prevent warping thereof, and temperature-limiting means for restricting the maximum temperature of the glass ceramic plate, said temperature-limiting means comprising a temperature sensor, the heat spreader plate and a temperature responder associated with the temperature sensor, said temperature responder being adapted to be connected in a power circuit for the said heating element and capable of deenergizing the heating element when the temperature of the spreader plate is above a predetermined temperature, said heating element being a high wattage unit for the size of the spreader plate to obtain high heating rates, said heat spreader plate also serving as a heat diffuser beneath the heating element such that when the heating element is deenergized the spreader plate serves to reduce the cooldown time.

Claim 14

A glass ceramic cook top having at least one heated area, each heated area having a heat spreader plate positioned therebeneath and in contact therewith, said heat spreader plate being of composite metal sheet material with a center core selected from a group of high thermal conductivity metals and alloys such as copper, silver and aluminum, and an outer skin selected from the group of oxidation- and corrosion-resisting metals and alloys such as stainless steel, nickel and chromium, a metal-sheathed resistance heating element attached to the underside of the heat spreader plate, reinforcing means braced beneath the heat spreader plate to prevent warping thereof, and temperature-limiting means for restricting the maximum temperature of the glass ceramic plate, said temperature-limiting means comprising a temperature sensor, the heat spreader plate and a temperature responder associated with the temperature sensor, said temperature responder being adapted to be connected in a power circuit for the said heating element and capable of deenergizing the heating element when the temperature of the spreader plate is above a predetermined temperature, said heating element being a high wattage unit for the size of the spreader plate to obtain high heating rates, said heat spreader plate also serving as a heat diffuser beneath the heating element such that when the heating element is deenergized the spreader plate serves to reduce the cooldown time.