Infrared radiant open coil heating unit with reflective fibrous-ceramic heater block

Claim 2

The combination recited in claim 1, wherEin said heater block is formed having a density within the approximate range of 10 to 15 pounds per cubic foot.

Claim 3

The combination recited in claim 1, wherein a minimum of 70 percent of the infrared energy emitted from the resistance element toward said heater block and having a wavelength within the range of approximately 2 to 5 microns is reflected by said heater block.

Claim 4

The combination recited in claim 1, wherein said resistance element is an iron-chromium-aluminum alloy and said block contains a minimum of 40 percent by weight of alumina to prevent loss of aluminum from the resistance element to said block.

Claim 5

A radiant cooking unit comprising, an upper utensil supporting cover plate of infrared transmissive material, a fibrous-ceramic insulating block disposed below said plate and having a raised peripheral face defining a central recessed area in spaced relation with the undersurface of said plate, means for supporting said block with said peripheral face on said plate, a ribbon-type infrared emissive resistance element continuously supported within spiral groove means formed in said recessed area, said groove means being channel-shaped in cross section having a flat bottom wall continuously supporting said resistance element thereon, said element formed in a deeply undulating curve pattern from an iron-chromium-aluminum alloy material whose operating temperature is in the range of 1,500 to 2,000* F., said block having dispersed therein sufficient finely divided opacifier substance to reflect a minimum of 70 percent of the infrared energy emitted from said element having a wavelength within the range of approximately 2 to 5 microns, said finely divided opacifier substance being selected from a group consisting of titanium oxide, zirconium oxide, tin oxide and potassium titanate, and said opacifier substance being present in an amount between 5 to 10 percent by weight of the fibrous-ceramic block.

Claim 6

In the cooking unit of claim 6, said resistance element ribbon being formed into a deeply undulating curve pattern having an amplitude-to-pitch ratio of the order of one.

Claim 7

In the cooking unit of claim 7, said resistance element ribbon having a height of approximately 125 mils and a thickness of the order of 7 to 9 mils, said resistance element ribbon having an amplitude of approximately 0.20 inch and a pitch of approximately 0.20 inch.

Claim 8

In the cooking unit of claim 6, said cover plate being formed from a recrystallized glass-ceramic material transmissive to infrared energy having a wavelength within the range of 1 to 5 microns.

Claim 9

A radiant cooking assembly comprising an upper utensil supporting cover plate of infrared transmissive material, a rigid fibrous-ceramic heater block disposed below said plate and having a raised peripheral face defining a central recessed area spaced from said plate, means for supporting said block with said peripheral face on said upper plate, an infrared emissive uninsulated iron-aluminum-chromium alloy resistance element ribbon located on said central recessed area in vertically spaced relation below the undersurface of said cover plate, said resistance element being supported in continuous spiral groove means formed in said central recessed area, said groove means being channel-shaped in cross section having a planar bottom wall providing substantially continuous support for said resistance element, said resistance element ribbon being formed in a continuous sinelike curve pattern having generally planar tangent sections throughout the length thereof, said resistance element having an overall width substantially equal to the width of said groove bottom wall whereby said element being constrained against radial movement within said groove means upon heating of said element, means for attaching said resistance element to said heater block including a plurality of U-shaped tie members, eAch of said tie members being in the form of an iron-chromium-aluminum alloy wire staple having a bridge portion engaging the upper edge of selected tangent sections of said resistance element, and said staples including a pair of spaced legs extending through said heater block with the free ends thereof projecting outwardly from the bottom surface of said heater block, said staple free ends being cemented to the underside of said heater block for fixedly retaining said staples in said heater block, said staples grouped on substantially uniformly spaced radial lines whereby each resulting arcuate section of said element is secured at its end points to said heater block permitting limited accordionlike movement within said groove means as said resistance element expands and contracts due to thermal changes.