Low thermal mass, plate surface heating unit

Claim 2

A low thermal mass, plate surface heating unit comprising a light weight top plate of high termal conductivity material, a metal sheathed electrical resistance heating elEment held in contact with a wide area of the underside of the plate to obtain generally uniform heating whereby the top plate acts as a heat sink for the heating element, the top plate being formed of composite sheet material with a center core of high thermal conductivity selected from the group comprising copper, silver and aluminum, and an outer skin sealing the core and selected from the group of materials comprising stainless steel, nickel and chromium, said outer skin serving to reinforce the center core and prevent its oxidation and corrosion, and a light weight reinforcing member of large depth braced against the underside of the plate across the span thereof to prevent warpage of the plate due to uneven temperature distribution.

Claim 3

A low thermal mass, plate surface heating unit as recited in claim 1 wherein the said light weight reinforcing member is of open framework design having a series of vertically disposed radial struts extending outwardly from a center member, the top edges of the radial struts being attached to the underside of the top plate.

Claim 4

A low thermal mass, plate surface heating unit as recited in claim 1 wherein the heating element is of coiled configuration, and the light weight reinforcing member is a reflector pan-shaped member which underlies the coiled heating element and has embossed ribs interposed between the coils of the heating element, and these ribs are attached to the underside of the top plate. oxidation

Claim 5

A low thermal mass, plate surface heating unit as recited in claim 3 wherein the underside of the top plate and the heating element has a low emissivity coating, while the reflector pan is formed of thin metal stock of low conductivity, the periphery of the pan being hermetically sealed to the underside of the top plate, while the interior of the reflector pan also has a low emissivity reflective coating, and the pan interior is evacuated in order to prevent the oxidation of the reflective surface.

Claim 6

A low thermal mass, plate surface heating unit comprising a light weight top plate of composite sheet material with a center core of high thermal conductivity selected from the group of high thermal conductivity metals and alloys such as copper, silver and aluminum and an outer skin surrounding the center core and selected from the group of oxidation and corrosion resisting metals and alloys such as stainless steel, nickel and chromium, a metal sheathed electrical resistance heating element of coiled configuration fastened to a wide area of the underside of the plate to obtain generally uniform heating whereby the top plate acts as a heat sink for the heating element, and a light weight reinforcing member of open framework and large depth attached to the underside of the plate to prevent warpage of the plate, said framework having a central member and a series of radial struts extending outwardly therefrom.

Claim 7

A low thermal mass, plate surface heating unit comprising a light weight top plate of composite sheet material with a center core of high thermal conductivity selected from the group of high thermal conductivity metals and alloys such as copper, silver and aluminum and an outer skin surrounding the center core and selected from the group of oxidation and corrosion resisting metals and alloys such as stainless steel, nickel and chromium, a metal sheathed electrical resistance heating element of coiled configuration fastened to a wide area of the underside of the plate to obtain generally uniform heating whereby the top plate acts as a heat sink for the heating element, and a light weight reinforcing member of open framework and large depth attached to the underside of the plate to prevent warpage of the plate, said framework having a central member and a series of radial struts extending outwardly therefrom.

Claim 8

A low thermal mass, plate surface heating unit comprising a light weight plate of composite sheet material with a center core selected from the group of high thermal conductivity metals or alloys such as copper, silver and aluminum, and an outer skin selected from the group of strong and oxidation and corrosion resisting metals or alloys such as stainless steel, nickel and chromium, a metal sheathed electrical resistance heating element of coiled configuration fastened to the underside of the plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, and a light weight reinforcing member in the form of a reflector pan which underlies the heating element and is also attached to the underside of the plate to prevent warpage of the plate, the underside of the top plate and the heating element having a low emissivity coating, while at least the interior of the reflector pan has a reflective coating.

Claim 9

A low thermal mass, plate surface heating unit comprising a light weight plate of composite sheet material with a center core selected from the group of high thermal conductivity metals or alloys such as copper, silver and aluminum, and an outer skin selected from the group of strong and oxidation and corrosion resisting metals or alloys such as stainless steel, nickel and chromium, a metal sheathed electrical resistance heating element of coiled configuration fastened to the underside of the plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, and a light weight reinforcing member in the form of a reflector pan which underlies the heating element and is also attached to the underside of the plate to prevent warpage of the plate, the underside of the top plate and the heating element having a low emissivity coating, while at least the interior of the reflector pan has a reflective coating.

Claim 10

A low thermal mass, plate surface heating unit comprising a thin plate formed as an inverted pan with downturned peripheral flange, the plate beIng of composite sheet material having a center core selected from the group of high thermal conductivity metals and alloys such as copper, silver and aluminum and an outer skin sealed over the core and 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 coiled configuration attached to the underside of the top plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, and a light weight reinforcing member of large depth attached to the underside of the top plate to prevent warpage of the plate due to uneven temperature distribution.

Claim 11

A low thermal mass, plate surface heating unit comprising a thin plate formed as an inverted pan with downturned peripheral flange, the plate beIng of composite sheet material having a center core selected from the group of high thermal conductivity metals and alloys such as copper, silver and aluminum and an outer skin sealed over the core and 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 coiled configuration attached to the underside of the top plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, and a light weight reinforcing member of large depth attached to the underside of the top plate to prevent warpage of the plate due to uneven temperature distribution.

Claim 12

A low thermal mass, plate surface heating unit as recited in claim 7 wherein the coiled heating element is of generally multiple-leaf clover configuration so as to cover a substantial area of the thin plate, the said reinforcing member being in the form of a reflector pan which covers the heating element and has radial embossed ribs interposed between the coiled heating element and these ribs are attached to the underside of the thin plate.

Claim 13

A solid plate surface heating unit comprising a light weight top plate of composite sheet material with an inner core of high thermal conductivity selected from the group comprising copper, silver and aluminum, the core being sealed in an outer skin selected from the group comprising stainless steel, nickel and chromium, the said top plate being substantially flat with a downturned peripheral flange to reinforce the plate, a spiral coiled metal sheathed resistance heating element fastened along the length thereof to the underside of the top plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, additional reinforcing means of light weight open framework and large depth also fastened to the underside of the top plate to insure that the plate will remain in a flat condition when it is operating at high temperatures in the range up to about 1400* F.

Claim 14

A solid plate surface heating unit comprising a light weight top plate of composite sheet material with an inner core of high thermal conductivity selected from the group comprising copper, silver and aluminum, the core being sealed in an outer skin selected from the group comprising stainless steel, nickel and chromium, the said top plate being substantially flat with a downturned peripheral flange to reinforce the plate, a spiral coiled metal sheathed resistance heating element fastened along the length thereof to the underside of the top plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, additional reinforcing means of light weight open framework and large depth also fastened to the underside of the top plate to insure that the plate will remain in a flat condition when it is operating at high temperatures in the range up to about 1400* F.

Claim 15

A solid plate surface heating unit comprising a light weight top plate of composite sheet material with an inner sheet of high thermal conductivity on the order of copper and a top and a bottom sheet of lower conductivity but of higher strength and resistance to oxidation than the inner sheet on the order of stainless steel, the peripheral edges of the top and bottom sheets being sealed together over the edge of the inner sheet to protect the inner sheet against corrosion and oxidation, a spiral coiled metal sheathed resistance heating element fastened to the underside of the top plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, and a light weight reinforcing means of large depth also fastened to the underside of the top plate to insure that the plate will remain in a flat condition when it is operating at temperatures reaching as high as 1400* F.

Claim 16

A solid plate surface heating unit comprising a light weight top plate of composite sheet material with an inner sheet of high thermal conductivity on the order of copper and a top and a bottom sheet of lower conductivity but of higher strength and resistance to oxidation than the inner sheet on the order of stainless steel, the peripheral edges of the top and bottom sheets being sealed together over the edge of the inner sheet to protect the inner sheet against corrosion and oxidation, a spiral coiled metal sheathed resistance heating element fastened to the underside of the top plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, and a light weight reinforcing means of large depth also fastened to the underside of the top plate to insure that the plate will remain in a flat condition when it is operating at temperatures reaching as high as 1400* F.

Claim 17

A solid plate surface heating unit as recited in claim 10 wherein the said reinforcing member is of open framework construction having a central member with a series of outwardly directed vertically disposed arms that are attached at their upper edge to the underside of the top plate, and a thermal reflecting member positioned beneath the unit for redirecting the heat in an upward direction.

Claim 18

A solid plate surface heating unit as recited in claim 11 wherein the said thermal reflecting member is also a holddown member which is adapted to underlie the edge of an opening in a cooktop in which the unit is to be mounted, and an adjustable tension member joining the reinforcing member to the reflecting member for clamping the member in a stationary operating position.

Claim 19

A cooking appliance comprising a cooktop having at least one opening formed therein, a solid plate surface heating unit mounted in the said opening, the unit having a light weight solid plate of composite sheet material of relatively high thermal conductivity positioned over the opening, the peripheral edge of the plate being formed downwardly into a reinforcing flange, a spiral coiled metal sheathed resistance heating element fastened along the length thereof to the underside of the top plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, a light weight reinforcing member of large depth also fastened to the underside of the top plate to prevent warpage of the plate and projecting down through the cooktop opening, a thermal reflecting member underlying the unit for redirecting the heat in an outward direction, said reflecting member underlying the edge of the opening in the cooktop in which the unit is mounted, and an adjustable tension member joining the said reinforcing member and the said reflecting member so that the edge of the opening is clamped by the interaction of the top plate and the reflecting member.

Claim 20

A cooking appliance comprising a cooktop having at least one opening formed therein, a solid plate surface heating unit mounted in the said opening, the unit having a light weight solid plate of composite sheet material of relatively high thermal conductivity positioned over the opening, the peripheral edge of the plate being formed downwardly into a reinforcing flange, a spiral coiled metal sheathed resistance heating element fastened along the length thereof to the underside of the top plate over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, a light weight reinforcing member of large depth also fastened to the underside of the top plate to prevent warpage of the plate and projecting down through the cooktop opening, a thermal reflecting member underlying the unit for redirecting the heat in an outward direction, said reflecting member underlying the edge of the opening in the cooktop in which the unit is mounted, and an adjustable tension member joining the said reinforcing member and the said reflecting member so that the edge of the opening is clamped by the interaction of the top plate and the reflecting member.

Claim 21

A surface heating unit for a cooking utensil defining a container for the preparation of food, wherein the unit is a low thermal mass, solid plate surface heating unit that has a light weight top plate of composite thin sheet metal material with a high thermal conductivity and an exterior surface that is resistant to oxidation and corrosion, and a spiral coiled metal sheathed resistance heating means of about half standard weight for a given wattage fastened to the underside of the top plate along the length thereof over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, a light weight reinforcing means of large depth fastened to the underside of the top plate to resist warpage of the plate during operation at high temperatures due to thermal stresses, the heat flow of the top plate of the unit being automatically adjustable to the size of the bottom face of the utensil to deliver substantially more heat to the area of the plate in contact with the bottom of the utensil than to the outermost exposed area of the plate, the outer coils of the heating element being closer spaced than the center coils so as to compensate for the heat losses at the periphery of the plate and obtain generally uniform temperature distribution across the plate when it is substantially completely covered by a cooking utensil, the conductivity of the top plate being of such a high value that it operates at a temperature only slightly higher than the temperature of the sheath of the heating element which permits the use of a lower temperature heating element of about half the weight over standard open coiled units of substantially equal wattage, while the relatively low operating temperatures of the sheath of the heating element also results in greatly reducing the current leakage through the heating element to the top plate and thence to the supporting structure for the heating unit.

Claim 22

A surface heating unit for a cooking utensil defining a container for the preparation of food, wherein the unit is a low thermal mass, solid plate surface heating unit that has a light weight top plate of composite thin sheet metal material with a high thermal conductivity and an exterior surface that is resistant to oxidation and corrosion, and a spiral coiled metal sheathed resistance heating means of about half standard weight for a given wattage fastened to the underside of the top plate along the length thereof over a wide area to obtain generally uniform, heating whereby the top plate acts as a heat sink for the heating element, a light weight reinforcing means of large depth fastened to the underside of the top plate to resist warpage of the plate during operation at high temperatures due to thermal stresses, the heat flow of the top plate of the unit being automatically adjustable to the size of the bottom face of the utensil to deliver substantially more heat to the area of the plate in contact with the bottom of the utensil than to the outermost exposed area of the plate, the outer coils of the heating element being closer spaced than the center coils so as to compensate for the heat losses at the periphery of the plate and obtain generally uniform temperature distribution across the plate when it is substantially completely covered by a cooking utensil, the conductivity of the top plate being of such a high value that it operates at a temperature only slightly higher than the temperature of the sheath of the heating element which permits the use of a lower temperature heating element of about half the weight over standard open coiled units of substantially equal wattage, while the relatively low operating temperatures of the sheath of the heating element also results in greatly reducing the current leakage through the heating element to the top plate and thence to the supporting structure for the heating unit.