US 3346720 A
Description (OCR text may contain errors)
United States Patent 3,346,720 INFRARED SURFACE HEATING UNIT WITH COR- RUGATED RIBBON-SHAPED FILAMENT Donald C. Siegla, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed May 25, 1965, Ser. No. 458,718
- 5 Claims. (Cl. 219464) ABSTRACT OF THE DISCLOSURE In preferred form, an infrared type heating unit in cluding a solid cover of infrared transmissive material, an underlying reflector plate spaced below the cover, support means on the reflector plate including a plurality of vertically upwardly facing grooves, a spirally formed, ribbon-shaped resistance element received within the grooves of the support means to be located above the reflector plate within a space between the reflector plate and the cover and freelyradially movable within the space, the ribbon shaped resistance element being corrugated along its length for thermal expansion and to reduce surface contact between the element and the support means.
This invention relates to domestic ranges and more particularly to electric ranges having infrared type surface heating units.
One problem with present-day domestic ranges is that of cleaning the surface unit cooking areas thereon. Both in the case of electrical and gas ranges, the cooking top surface area has many cracks or crevices therein, especially around the surface heating units thereon that tend to accumulate spillage that can become baked on so as present an extremely difiicult and unpleasant cleaning task.
Accordingly, an object of the present invention is to improve domestic ranges by the provision of a single, continuous, non-metallic top of a relatively low thermal conductivity having an unbroken surface thereon that is easily cleaned.
A further object of the present invention is to improve domestic range units by the provision of a single top having a continuously, unbroken surface thereon in the surface unit cooking area wherein the top is constructed of an infrared transmissive material of relatively low thermal conductivity to minimize conduction of absorbed energy across the top.
A still further object of the present invention is to improve domestic ranges by the provision of a single member that forms the top of the range as a continuous, un broken surface and wherein the member has a plurality of spaced apart regions thereon associated with infrared heating elements supported beneath the member for heating utensils thereon by radiation through the member.
Still another object of the present invention is to improve domestic ranges by the provision of a single member forming a top therein having a continuously, unbroken upper surface including regions thereon for supporting utensils to be heated and wherein the memher is constructed of an infrared transmissive material having a low thermal conductivity and wherein infrared heating elements are located below the member for selectively heating the utensil supporting regions by direct infrared radiation.
Yet another object of the present invention is to improve electrical ranges by the provision of a solid glass or recrystallized glass top which entirely and continuously covers the surface unit cooking area of the range and includes an upper surface configuration that forms surface utensil supporting portions for trapping spillage from the untensils and further includes infrared heater units disposed beneath the utensil supporting portion thereon to be completely isolated from the top of the range.
A further object of the present invention is to improve domestic ranges by the provision of a non-metallic member forming a range top having an upper surface defining utensil heating regions thereon wherein the range top surface is formed continuously without cracks or crevices through the surface unit cooking area of the range and has a plurality of infrared heating elements located on the underside thereof and supported from the underside thereof to heat utensils supported on the upper surface by direct radiation.
Yet another object of the present invention is to improve domestic ranges by the provision of a single member of non-metallic material that forms the top of the range in the surface unit cooking area and has an unbroken upper surface that is easily cleaned and further includes a plurality of spaced apart regions with infrared heating elements located therebelo'w for directly heating utensils supported on the spaced apart regions through radiation.
Yet another object of the present invention is to improvide infrared surface heating units by the provision of a ribbon-shaped electrical resistance heating element surrounded by a low-profile envelope and located in spaced relationship thereto prevent direct thermal contact therebetween wherein the ribbon-shaped resistance element is continuously convoluted throughout its length to increase the radiating surface area of the heating element.
Still another object of the present invention is to improve infrared surface heating units by the provision of a low-profile outer envelope including an upper plate of infrared transmissive material and a lower plate of low thermal mass located in spaced relationship to the upper plate and an electrically energiza'ble resistance type heating element located therebetween having a ribbon shape supported by a spider-shaped member out of direct heat transfer relationship with both of the plates wherein the spider-shaped member has a plurality of grooves for disposing the 'ribbon-shaped element through a predetermined planar extent and wherein the ribbon-shaped member is continuously convoluted throughout its length to reduce the surface contact thereof with the spider-shaped element to reduce heat transfer between the element and its supporting spider member.
Still an other object of the present invention is to improve domestic ranges by the provision of a cooking surface top of infrared transmissive material having a continuously unbroken surface throughout the surface unit cooking area wherein the single top member includes a plurality of depending members thereon which receive a lower bearing plate of an infrared surface heating unit that is supportingly carried by the depending members through clip members that are carried by the depending members to supportingly engage the lower plate.
Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.
In the drawings:
FIGURE 1 is a perspective view of a domestic range including the present invention;
FIGURE 2 is an enlarged view in vertical section taken along the line 22 of FIGURE 1;
FIGURE 3 is an enlarged view in vertical section taken along the line 33 of FIGURE 1; and
FIGURE 4 is a fragmentary view in top elevation of a portion of the surface heating unit of FIGURE 2 with its upper surface removed.
Referring now to the drawings, in FIGURE 1, a domestic range is illustrated having an outer casing 12 which includes a collar 14 around the top edge thereof that forms a top opening 16 in the range unit 10. The peripheral collar 14 merges with a rearwardly located control panel 18 having a plurality of control knobs 20 thereon for selectively energizing infrared surface heating units to be described.
Within the top opening 16 is located a drop-in top member 22 that defines the complete surface unit cooking area of the range 10. The top member 22 has a continuous upper surface 24 that extends throughout the planar extent of the opening 16 and includes a raised peripheral edge 26 formed continuously therearound that serves to trap spillage on the top surface 24. At the raised outer peripheral edge 26 the top 22 is supported by a continuous annular resilient gasket 28 on an inwardly turned edge 30 of the collar 14, as best seen in FIGURE 3. The gasket 28 serves to take up unevenness in the supporting flange 30 and also serves to isolate the top 22 from the outer casing 12.
In accordance with certain of the principles of the present invention, the single top member 22 is formed of a solid glass or recrystallized glass material having a relatively low thermal conductivity in the order of 0.5 to 2.5 B.t.u. per hr. ft. F. Examples of such materials are quartz, a high silica glass such as Vycor made by Corning Glass or a recrystallized glass ceramic such as Cer-Vit manufactured by Owens-Illinois. These materials also are representative of suitable infrared transmissive materials that have desirable strength properties and are capable of transmitting substantially all of the infrared energy emitted from the heating element of an infrared type surface heating unit.
In the illustrated embodiment of the invention, the source of infrared energy is a plurality of surface heating units 32 located beneath the top member 22, one of which is illustrated in FIGURE 2.
Each of the infrared surface heating units 32 is located below a raised portion 34 on the upper surface 24 of the top 22 that serves to define a utensil supporting surface raised above the general level of the top surface 24 whereby spillage from a utensil is accumulated on the surface between the raised surface portions 34 making it easily removable during cleaning.
Since the top 22 is continuously formed across the top range opening 16, the infrared surface heating units 32 are completely isolated from any spillage or the like that might tend to adversely affect the operation thereof.
Another feature of the illustrated arrangement is that each of the heating units 32 are supported by the single top 22 so as to be removable therewith from the rest of the range unit 10 or a like supporting structure such as a built-in countertop. This enables components of the infrared surface heating unit 32 to be readily accessible for repair and further allows the completed unit including the top 22 and surface heating units 32 to be readily installed in place on the range or a like supporting unit.
Referring now more specifically to the heating units 32, as best seen in FIGURE 2, they each include a lower dish-shaped bearing plate 36 having a plurality of peripheral tabs 38 thereon that are received within grooves 40 formed in depending integrally formed members 42 on the lower surface of the top 22 around the outer periphery of the raised surface portions 34 thereon. The plate 36 is preferably formed of an electrically insulating ceramic material such as alumina, steatite or the like having a low thermal mass. The depending members 42 each also includes a groove 44 therethrough in which is received a spring clip 46 that has an upper surface 48 supportingly receiving one of the tabs 38 whereby the lower bearing plate 36 is effectively hung from the underside of the top 22. The bottom of the lower bearing plate 36 is spaced below the top 22 to form a cavity 50 therebetween in which is located a spider-shaped supporting member 52 including a hub portion 54 and a plurality of circumferentially located radially outwardly directed arms 56. The support member 52 is preferably constructed of a material having good electrical insulating properties and a low thermal conductivity, for example quartz or a high silica glass material. Each of the arms 56 has a plurality of grooves 58 therein in which is located a spirally wound continuous heating element 60 having one end thereof electrically connected to a terminal 62 and the opposite end thereof electrically connected to a terminal 64. The terminals 62, 64 are directed through the lower plate 36 to be electrically connected across a suitable power source to energize the resistance heating element 60 into the infrared range whereby radiation emitted therefrom is directed upwardly through the infrared transmissive top 22 at the surface portions 34 thereon to raise the temperature of utensils supported thereon.
The heating element 60 preferably is self-heated into the range of 1500 F. to 2000 F. and is constructed of a high-temperature resistance material from a nickelchromium family or an iron-chromium-alurninum family or the like having desirable strength and electrical characteristics.
By virtue of the illustrated arrangement the heating element 60 is located out of direct heat transfer relationship with both the top member 22 and the base plate 36 whereby the temperature thereof is maintained at an elevated temperature so as to maintain the effectiveness of the radiant effect therefrom.
In accordance with certain of the principles of the present invention the heating element 60 is continuously convoluted throughout its length by a plurality of sinusoidally-forrned corrugations 66 that substantially increase the radiant surface heating area of the heating element 60 and, furthermore, reduce the surface contact between the heating element 60 and the arms 56 at the grooves 58 therein so that heat transfer from the element 60 to the arms 56 is minimized.
If desired and as illustrated in FIGURE 2, an infrared reflective layer 68 can be provided on the upper surface of the plate 36 to reflect downwardly directed infrared radiation from the heating element 60 upwardly through the top 22 to supplement the direct radiant heating effect of the heating element 60.
Another feature of the illustrated arrangement is that by the provision of a glass top 22, any energy absorbed by the top 22 will pass into a utensil supported by the raised surface portion 34 of the top 22 and because of the low thermal conductivity of the top a relatively small amount of the absorbed energy tends to be conducted away from the heated raised surface portions 34 to the surrounding area of the top 22.
While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.
What is claimed is as follows:
1. A cooking assembly comprising, a sheet of infrared transmissive non-metallic material including an upper utensil supporting surface, said sheet of non-metallic material having a thermal conductivity of substantially .5 to 2.5 B.t.u. per hour foot degree F., a plurality of infrared heating units, means for supporting each of said heating units on the underside of said sheet in spaced relationship with one another, each of said heat ing units including an uninsulated electrical resistance element located in spaced relationship with said sheet, said each of said heating units having a predetermined planar extent and being energizable into the infrared range of 1500 F. to ZOO-0 F. for directly heating utensils supported on said upper surface thereabove through radiation energy absorbed by said cover sheet immediately above said heating units being restricted by the low thermal conductivity of said cover sheet primarily to passage by conduction directly to a utensil supported by said cover sheet rather than to areas of said cover sheet in radially surrounding relationship to the predetermined planar extent thereof overlying each of said heating units.
2. A cooking surface assembly comprising, an upper plate of infrared transmissive non-metallic material having an upper utensil supporting surface, a lower plate disposed below said upper plate having an upwardly facing infrared reflective surface, means for supporting said lower plate on said upper plate, an electrically energizable uninsulated resistance element located between said upper and lower plates, means for supporting said resistance element out of direct heat transfer relationship with said plates including means defining a plurality of vertically directed grooves located above said reflective surface and below said upper plate, said resistance element being spirally wound and supported within said grooves for free radial expansion above said reflective surface, said spirally wound heating element also being ribbon-shaped and having a plurality of transverse corrugations along the length thereof for increasing the radiation emissions therefrom and for reducing surface contact between said resistance element and said support means during free radial expansion of said resistance element within said grooves.
3. A cooking surface assembly comprising, an upper plate of infrared transmissive material, a lower plate located below said upper plate in spaced relationship thereto having a low thermal mass, coacting means on said upper and lower plates for interconnecting said plates one to the other and forming an open space therebetween, a heating element electrically energizable into the infrared range disposed between said plates, supporting means on said lower plate, said supporting means having a plurality of spaced apart radially and circumferentially located vertically formed grooves therein. said heating element being spirally wound through said grooves whereby said supporting means serves to locate said heating element out of direct heat transfer contact with said upper and lower plates and for free radial thermal expansion between said upper and lower plates, said heating element having a ribbon shape located edgewise within said groove and including a plurality of generally transverse convolutions along the length of said heating element for reducing the contact between the sides of said heating element and said supporting means at the grooves therein.
4. A surface unit cooking assembly comprising, an upper sheet of infrared transmissive non-metallic material having a raised peripheral edge for trapping spillage and an upper surface, said surface having a raised portion therein, a plurality of depending members on the undersurface of said sheet around the outer periphery of said raised portion, a lower plate disposed below said sheet beneath said raised portion, said depending members having grooves formed therein, tabs on the outer periphery of said plate received by said grooves, and spring clip means insertable through said grooved depending members supportingly engaging said lower plate tabs for supporting said plate on said sheet, an electrical resistance heating element disposed between said plates and energizable into the infrared range for directly heating utensils supported by said raised surface portion through radiation, and means for supporting said heating element out of direct heat contact relationship with said sheet and said lower plate.
5. A cooking surface assembly comprising an upper utensil supporting plate of glass infrared transmissive material having a thermal conductivity of substantially .5 to 2.5 B.t.u. per hour foot degree F., a reflector plate located below said upper utensil supporting plate, means for connecting said reflector plate to said upper plate to form an open space therebetween, support means on said reflector plate including a plurality of radially and circumferentially spaced vertically directed, upwardly facing grooves therein above said reflector plate and below said upper plate, an elongated, ribbon shaped electrically energizable uninsulated high temperature resistance element supportingly received by said supporting means within said grooves and having the lower edges thereon engaging the bottom of each of said grooves, said ribbon shaped resistance element having a width less than that of each of said grooves thereby being free upon electrical energization of said resistance element to move radially within said grooves between said plates, said resistance element being corrugated along its length to form sinuous side surfaces thereon to space said resistance element from said supporting means and to reduce direct thermal contact therebetween and said sinuous side surfaces along the length of said resistance element increasing the radiation surface on said resistance element for improving transfer of energy by radiation from said resistance element through said upper utensil supporting plate.
References Cited UNITED STATES PATENTS 2,179,934 11/1939 Jones 219-538 2,471,884 5/1949 Mannot 219-464 X 2,640,906 6/ 1953 Haynes 219445 2,727,133 12/1955 Scofield 2l9467 X 2,799,765 7/1957 Jenkins et al 219464 X 2,870,316 1/1959 Ferguson 219-464 X FOREIGN PATENTS 521,735 7/1953 Belgium. 621,927 6/1961 Canada.
RICHARD M. WOOD, Primary Examiner. L. H. BENDER, Assistant Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,346,720 October 10, 1967 Donald C. Siegla It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.
Column 1, line 60, for "therein" read thereon column 2, lines 26 and 27, for "improvide" read improve line 29, after "thereto" insert to column 4, line 60, after "cooking" insert surface line 74, after "radiation" insert a comma; column 5, line 38, after "therein" insert a comma Signed and sealed this 12th day of November 1968.
EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.