US2870316A - Heaters - Google Patents

Description

Jan, 20, 1959 H. D. FERGUSON, JR 2,370,316

HEATERS Filed May 18, 1956 INVENTOR.

NN .NM (m. (N NN Unite HEATERS Application May 18, 1956, Serial No. 585,902

14 Claims. (Cl. 219-37) So-called surface heaters, including for instance plate type heaters for kitchen ranges and the like, are generally known. The present invention provides a heater of this kind with integral, direct-acting means for indicating whether the heater is on or oif This indication is desirable mainly under simmering conditions in which a heater plate or coil is energized although the energzation cannot be noted from a distance. While beinghighly desirable, the direct or integral indication of such a condition, by the heater itself, was heretofore, economically and practically, impossible, thereby leading to frequent inconvenience and even occasional danger. It is true that the user was generally carefulfor reasons of economy as well as safety-to turn all heater switches or valves to the off position when heaters were unused; however, a certain eifort was required for checking whether this had been done, and it was all too common that some such elements, at some times, were inadvertently left on or erroneously turned on.

Many of the heater constructions used in the past would have provided the required space for a pilot lamp, in the heater itself; but the operating conditions were such as to cause overheating or" such a lamp, unless special and expensive lamp protectors of heavy glass or the like were installed, which tended to make a heater unit entirely too expensive and also too bulky. Therefore, instead of using direct-acting indicator means, some ranges had pilot lights mounted on a panel, forming part of the rear splashguard of a range; and attempts were made, by means of name plates or the like, to identify the surface heater represented by each light. However, too much attention was needed to determine which heater belonged to each pilot; and too much extra cost of installation and extra care in maintenance were required for such a system. The typical attitude of householders with respect to their kitchen equipment is too casual to justify such extra efforts.

I have discovered that it is possible to provide an integral, instantly recognizable, inexpensive and practical combination of surface heater and pilot light, which is believed to overcome the shortcomings of the prior attempts made in this field; and it is a primary object of this invention to improve surface heaters by the use of such a combination. This improvement is realized by suitable modication of the heater disclosed in application Serial No. 503,667, tiled on April 25, 1955, by Donald W. Scofield and assigned to the assignee of the preseutV invention, now Patent No. 2,833,908, wherein a ilat coil of wire or the like is held with distributed pressure, by a heat insulating plate, against a heat conductive and preferably transparent surface heater plate. The modiicationpertains to the heater-parts below the transparent plate; those parts, according to the present invention, are used as a combined heat protector and frame for a central lamp, eliminating the problem of overheating the central lamp, thereby dispensing with separate lamp protectors and remote lamp indicators.

This construction provides a practical solution for the tates Patent O "ice old problem of integral heater and pilot light installation; and it even leads to an improved construction of support means for the insulator, the heater and the glass plate. This latter improvement, as well as other features, advantages and objects of the present invention, will become clear from the detailed description which follows.

In the drawing,

Figure 1 is a vertical transverse section through a surface heater unit incorporating the present invention.

Figure 2 is a plan view of the unit of Figure l.

Figure 3 is a bottom view of the unit of Figure 1, and

Figure 4 is a circuit diagram for the unit of Figure l.

Referring first to Figure 1, the pilot light sub-assembly is shown as comprising a small incandescent lamp 11, installed in an upwardly facing socket 12 and provided with electrical conductors 13, 14. The socket 12 is installed between the legs 15, 16 of an upwardly facing, yoke-shaped, metallic pilot light support member 17; said legs having toe portions resiliently inserted under flat sleeve members 18, 19 which are secured to the underside of an annular heater pan 20 at diametrically opposite locations adjacent a central aperture 21 of said pan.

The annular pan has an outer wall 22, bottom 23 and inner wall 24, all reinforced by radially oriented ribs of channel-shaped transverse section, which ribs may be pressed into the metal of the pan during the same operation when the said walls and other portions of the pan are formed. A particularly rigid structure is formed, from light and inexpensive metal and by easy forming procedures, in the manner shown in Figures 1 and 3, that is, by making each rib 25 continuous across out-er walls 22, bottom 23 and inner walls 24. By this expedient it is also possible to impress and maintain a predetermined curvature in the bottom 23, such as the upwardly con- Vex form shown in Figure 1, and to secure the same against a so-called oil can etiect or reverse bending on application of downward force. While the strengthening of a relatively thin metal oor can be achieved by various forms of ribs or beams, such strengthening is improved by making the oor 23 annular and installing a practically rigid system of inner wall 24 and of ribs 25 radiating from the wall; the moment arm of any distributed force acting on the tloor is reduced and the moment of inertia of the reinforcing system can be substantially increased. As a result, the required application of supporting action to the overlying parts, by bottom 23 and wall 24, is greatly facilitated.

Referring to the peripheral part of the heater shown in Figure l, an annular flange 26, integral with the outer wall 22, is secured to a companion flange 27, by suitable fastening means 28.

By the interaction of the anges 26, 27, pressure is developed between a solid, circular, substantially flat plate 29 of heat transmissive, shock resistant glass or the like, having a lip 3i) below the companion flange 27, and an annular, compressing, desirably resilient, insulating mat or pad 31 which contacts the glass plate in a substantially at plane. A suitably convoluted electrical heating wire 32, which may be made for instance of nickel chromium alloy or the like, is shown as being interposed between the plate 29 and insulator 31, the insulator holding the wire under distributedtpressure against the plate. Conductors 33, 34 supply electric current to the heater wire.

The heat transmissive glass plate 29 has a central portion 35, overlying the central aperture 21 in the pan 20 and insulator 31. Either the entire glass plate 29 or at least the central portion 35 is light transmissive, that is, transparent or at least translucent, in orderto disclose whether the lamp ll is on or of`t`, lighted or dark. The central portion 35 may be distinctively colored and, as shown in Figure 2, it may be provided with a surrounding, for instance, circular marking and with inner lettering indicia or other markings 36, in order to provide either an illuminated trade mark effect or some optical elect such as that of faceted glass; but, as shown in Figure l, the central and outer parts of the top surface may be uniform and substantially flat, so as to insure proper support for cooking vessels and to facilitate cleaning of the range.

A substantial part of the light of lamp 1i is transmitted from the aperture 21 into and through the central portion 35 of the glass plate 29, whereas little of the heat of the element 32 is transmitted through the insulator 3l into the aperture 2. l have measured actuall temperatures prevailing in the upper part of the socket l2 of a standard 7 watt incandescent lamp 1l, installed as shown in a lStO watt heater 2, 31, 32, which in turn was installed in a rane as generally used. Said upper part of the socket was found 'to be the most critical area; a somewhat sensitive binder material is here provided, between the glass of the lamp envelope and the metal of the socket, and this material tends to soften and melt at temperatures slightly above 4G() degrees Fahrenheit. (The next critical element consists in the solder used in adjacent regions, which tends to soften and melt at approximately 600 degrees Fahrenheit.) Temperatures well below said 400 degrees Fahrenheit prevailed at the point indicated, even when heater 32. and lamp il had been on for as long as one week without interruption and with downward rellection of heat by an aluminum vessel standing on the heater plate Higher temperatures prevail on the wall 24 and lower ones in the range below the heater. The resulting convection seems to carry heat to, and dissipate it through the large metal surfaces of the range, rather than the pilot lamp unit.

In actual service the conditions prevailing in and around the lamp il are even less exacting, since a surface heater of the present kind is rarely if ever in use for a period longer than a few hours, so that the lamp socket l2 hardly reaches a temperature as high at 300 degrees Fahrenheit.

ln operation, the lamp l1 is lighted, through a switch 37 as shown in Figure A., whenever the heating element 32. is placed in operative condition through the same switch und a conventional auxiliary heater wire 33 connected therewith, which activates a heat responsive element 3S* forming part of a switch all tor the principal heater circuit. rihe thermostatic switch 39, 40 may have means d for adjusting it so that the heating element 32 is kept in a predetermined temperature range. For instance, "simmering1 ot the contents of a cooking vessel can be achieved by keeping element 32 in the condition of a heat radiating black body, or at a very low, reddish glow. This condition will` usually be invisible, or scarcely noticeable through the heater plate 29; but the pilot lamp ll of the present heater unit automatically and directly shows the on condition of the heater wire unit 32, 37, 38, 39, even when the wire 32 itself discloses no visible sign or" such condition. For the sake of simplicity the pilot lamp 11, as shown, may also be left on while the heater wire 32 is at a bright red or orange glow, visible by itself.

The on or energized condition of the lamp 11 is plainly visible in the central portion 35 of the plate Z9. To a substantial extent it is also visible, due to the linherent light guiding effect of glass, at a suitably formed edge f the glass plate Z9, above flange 27, so that the on or ofi condition of the heater can be noted even when a cooking vessel stands on the plate.

While only a single embodiment of the invention has been described, it should be understood that the details thereof are not to be construed as limitative of the invention, except insofar as set forth in the following claims.

I claim:

l. In a plate-type heater: a heater plate; a heating element adjacent the plate; an electrical lamp; and heat insulator means for holding the heating element against the plate, said insulator means having the general form of a frame around the lamp.

2. A structure as defined in claim l, wherein the heat insulator means comprises a structure which supports the lamp.

3. A structure as detined in claim l, wherein the plate is a heat and light transmissive, imperforate, shock resistant member of glass or the like covering the frameforming insulator means and the lamp surrounded by said means.

4. ln a heater: a plate of glass or the like; a convoluted heating element; a structure holding the heating element against the surface of a plate of glass or the like, said structure framing an inner region and thermally insulating the element from the inner region while allowing light from the inner region to illuminate the center of said plate of glass or the like; and electrical lamp means in said inner region.

5. ln a heater as described in claim 4: the feature that said structure comprises an annular pan and an annular resilient body of insulator material, pressed against the plate by the pan for pressing the convoluted heating element against the plate.

6. in a heater: imperforate, shoe t-resistant, heat and light transmissive plate means; heat insulator means underlying an annular part of the plate means and surrounding, thermally protecting and mechanically framing a region coaxial with said annular part, While holding a heating element against said annular part; and electrical lamp means in said region.

7. in a heater: plate means adapted to transmit heat and having at least a central portion adapted to transmit light; heater means underlying an annular portion of the plate means and adapted to heat the same; insulator means comprising an annular portion underlying the heater means and adapted substantially to insulate the same from surrounding space except from said annular portion of the plate means; and a lamp mounted below and illuminating said central portion of the plate means and insulated from said heater means by said insulator means.

8. ln a heater: a plate of glass or the like, said plate having substantial transmissivity for heat and light; an element underlying an annular surface of the plate and adapted to heat said surface; an annular insulating body underlying the elenent and adapted substantially to insulate the same from all regions below said surface; and a pilot lamp mounted below and centrally of said surface to illuminate said surface and to be protected by said body from the heat of said element.

9. A heater comprising an annular pan; an annular pad or heat insulator thereon; a heating wire arranged in an annular pattern on the insulator; a heat and light transmissive plate overlying the annular parts mentioned; and electrical. means for use in the supervision of functions of the heater, said means extending into the space surrounded by the annular parts mentioned.

l0. A heater as described in claim 9, wherein the pan comprises inner and outer walls, an annular bottom between said walls and a plurality of reinforcement members, each extending without interruption across portions of the bottom and of both walls.

ll. A heater as described in claim l0 wherein the bottom has a curved, upwardly convex cross section.

l2. in a heater: a pan having a bottom of curved and upwardly conve); cross section, said pan also having an inner wall surrounding an opening in the bottom, an outer wall, and reinforcing means extending across the bottom onto the inner wall; a heat insulating pad, supported by the pan, surrounding the inner wall and surrounded by the outer wall; a convoluted wire supported by the pad; a surface heating plato overlying the wire;

2,870,316 l s and means comprising the pan and the pad for keeping the wire in close thermal coupling with the plate.

13. In a heater as described in claim 12, the feature that the pad is resilient. 2164652? 14. In a heater as described in claim 12: pilot lamp 5 240924' means mounted to illuminate the opening. 2659069 References Cited in the lle of this patent UNITED STATES PATENTS Goldthwaite July 4, 1939 Bilan Oct. 15, 1946 Kinsella Nov. 10, 1953

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