US2715174A

US2715174A - Electrical resistance space heaters

Info

Publication number: US2715174A
Application number: US346999A
Authority: US
Inventors: Nathanson Max
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-04-06
Filing date: 1953-04-06
Publication date: 1955-08-09
Anticipated expiration: 1972-08-09

Description

Aug. 9, 1955 M. NATHANSON 2,715,174

ELECTRICAL RESISTANCE SPACE HEATERS Filed April 6, 1955 4 Sheets-Sheet l j'NvE/vTon Mnx NHTHHNSON Aug.9, 1955 M. NATHANSON ELECTRICAL RESISTANCE SPACE HEATERS 4 Sheets-Sheet 2 Filed April 6, 1955 ,n 4 @MWJDDDDDDDD mwr DDRVQVPHPDDDDDDOIAPPIWFM n M m 1% W r W N m I M I,

g- 9, 1955 M. NATHANSON 2,715,174

ELECTRICAL RESISTANCE SPACE HEATERS Filed April 6, 1953 4 Sheets-Sheet 3 [Nye/wok Mnx Nnmmvso/v finale/way Aug. 9, 1955 M. NATHANSON ELECTRICAL RESISTANCE SPACE HEATERS 4 Sheets-Sheet 4 Filed April e, 1955 United States Patent 0 ELECTRICAL RESISTANCE SPACE HEATERS Max Nathanson, Montreal, Quebec, Canada Application April 6, 1953, Serial No. 346,999

19 Claims. (Cl. 219-49) This invention relates to electrical resistance space heaters and particularly to radiant heater embodying a heat radiating panel comprising a tempered glass plate which is heated by passage of electrical current through a thin electrical resistance element bonded thereto and which converts the heat thus received into heating rays which are radiated into space.

One object of the present invention is to provide an improved heater of the type referred to in which the heat radiating glass is mounted so that the heating element may be connected to and disconnected from the power supply in a convenient manner without removing the glass plate from its mounting means.

Another object of the invention is to provide improved means for mounting the heat radiating glass in the heater structure so that relative movement between the glass and surrounding fixed portions of the heater necessary to take care of expansion and contraction of the glass are provided for in a simple manner which eliminates expansion and contraction clicking noises of the glass and also enables the glass to be mounted in the heater and removed therefrom in a more rapid and convenient manner.

A further object of the invention is to provide improved means for preventing accidental breakage of the circuit connections at the terminal of the heating element due to pulling strains on the electrical conductors connected to said terminals.

A further object of the invention is to provide improved designs of heater in which the overall depth of the complete heating unit is drastically reduced as compared with conventional designs and without impairing the heating efliciency.

A further object is to provide improved designs of heater which are not only drastically reduced in overall depth as compared with conventional designs but also embody improvements in the mounting of the heating panel which enable them to be produced at a substantial reduced cost.

Other objects, advantages, and characteristic features of the invention will appear from the following detailed description of various preferred embodiments shown in the accompanying drawings, in which Fig. 1 is a front elevation view of one form of wall heater assembly embodying the invention.

Fig. 2 is an enlarged detail view of a corner portion of the assembly appearing in Fig. l and shows the manner in which supporting insulators are employed to mount the heat radiating panel in such manner as to provide for necessary movement of the panel due to expansion and contraction.

Fig. 3 is a perspective view of the supporting insulator appearing in Fig. 2.

Fig. 4 is a vertical sectional view taken substantially along the section lines 4-4 of Fig. 1.

Fig. 5 is an exploded view of the assembly shown in Fig. 4.

Fig. 6 is a rear elevational view of a frame member in which the heat radiating panel is mounted by means of the supporting insulators shown in Figs. 2 and 3.

Fig. 7 is an end view of the construction shown in Fig. 6 as viewed in the direction indicated by the direction lines 7-7 of Fig. 6.

Fig. 8 is a fragmentary sectional view taken substantially along the section lines 88 of Fig. 6.

Fig. 9 is a fragmentary sectional view taken along the section line 99 of Fig. 6.

Fig. 10 is a view similar to Fig. 2 but showing the panel supporting frame and one of the upper panel supporting insulators in section.

Fig. 11 is a view similar to Fig. 4 but showing a modified assembly,

Fig' 12 is a View similar to Figs. 4 to 11 but showing a further modification.

Fig. 13 is a view showing a modification of the assembly appearing in Fig. 12 and Fig. 14 is an enlarged detail view illustrating an upper corner portion of the modification appearing in Figs. 12 and 13.

The assembly shown in Figs. 1 to 10 inclusive, embodies a rectangular back member 5 including a back wall or plate member 6 provided with forwardly projecting marginal walls 7 defining a rectangular recess 8. A centrally apertured wall plate 9 is positioned immediately adjacent the front edges of the marginal walls of back member 5 and projects laterally beyond the outer surfaces of said walls. The central aperture 10 of wall plate 9 is bounded by wall plate flanges 11 which extend into recess 8 in contact with the marginal walls 7 of said recess.

The marginal walls '7 of back member 5 and the contacting flanges 11 of wall plate 9 are riveted together by means of rivets 13 which are passed through registering rivet-receiving openings 12 provided in said walls and flanges. The rivets 13 also serve to secure a plurality of angle brackets 14 in place against the inner surface of each Wall plate flange 11. Each angle bracket is thus riveted in place with one limb 15 bearing flatly against the adjacent wall plate flange 11 and the other limb 16 extending inwardly from said flange.

A rectangular heating-panel supporting frame generally indicated at 17 is positioned within the forward portion of the recess 8 of back member 5 so that the outer marginal surfaces of said frame are sparated from the opposing wall plate flanges 11 by air spaces 17a.

The heating-panel supporting frame 17 comprises a rear wall or plate member 18, forwardly projecting marginal walls 19 and front flanges 20, the latter extending inwardly from the front edges of the marginal walls 19 in parallel relation to the rear wall 1%. The marginal walls 19 of frame 17 are provided with air circulating openings 1% placing the interior of said frame in communication with the previously mentioned air spaces 17a.

Anchoring plates 2?. are fastened to the rear wall 18 of frame 1'7 at each marginal portion of said frame so that outer end portions 21a of said plates project outwardly beyond the marginal frame walls 19. The projecting portion 211: of each anchoring plate 21 is fitted against and secured to the limb 16 of one of the previously mentioned brackets 14 by means of a screw 22 which passed through an elongated slot 23 provided in said anchoring plate. Plates 21 are preferably riveted to frame 17 as indicated at 24 in Fig. 6 but may also be secured in place by welding or any other suitable fastening means,

A- rectangular heat radiating panel 27 of the electrical resistance type is supported in frame 17 in spaced relation to the rear and marginal walls of said frame by means of substantially Lv-shaped supporting insulators 28. These supporting insulators, four in number, are located at the four corners of frame 17 and are provided with inner L-shaped grooves 29 in which the corner portions of the heat radiating panel 2'7 are fitted, as clearly shown in Figs. 4, 8, 9 and 10 so that the panel is firmly held against movement relative to the insulators. The insulators 28 are also provided with outer L-shaped grooves 30 in which cushioning members 31, made of rubber or other resiliently compressible material, are fitted so that said cushioning members 31 are confined between the insulators 28 and the portions of the marginal walls 19 of frame 17 to which the insulators are opposed. These cushioning members 31 permit sufiicient relative movement between the insulators 2t and the marginal walls 19 of frame 17 to take care of expansion and contraction of the heat radiating panel 27.

As indicated in the drawings the insulators 28 are preferably made of rigid ceramic material, such as porcelain.

As shown to advantage in Figs. 2, 5 and 6 the front flanges or" frame 17 are terminated a substantial distance from the corners of the frame so as to leave gaps 32 to facilitate the insertion and removal of the insulators 28 and the heat radiating panel 27. After the insulators 28 and the heat radiating panel 27 have been inserted in frame 17 the gaps 32 are closed by the application of corner covers generally indicated at 33. Each of these covers 33 includes a front plate portion 34 and rearwardly directed securing flanges 35. The front plate portion 34 overlies the adjacent insulator 28 and the adjacent corner portion of the heat radiating panel 27 while the securing flanges 35 overlie and are secured to marginal walls 19 of frame 1'7 by screws 36 or other suitable fastening means.

The heat radiating panel 27 shown in the present drawings is of the well known type comprising a tempered glass plate 38 having an electrical heat radiating resistance 39 fused thereto and extending across the plate in the more or less zig-zag fashion shown in Fig. 1. As shown to advantage in Fig. 6, the terminals of the electrical resistance 39 are located adjacent one of the lower corner portions of the heat radiating panel 27 directly opposite a slot or opening 40 provided in the rear wall 18 of frame 17. These terminals of the electrical resistance 39 are firmly secured by

suitable terminal connections

41 and 42 to corresponding ends of a pair of

conductors

43 and 44. At points adjacent the slot 40 intermediate portions of the

conductors

43 and 44 are firmly clamped against the back wall 18 of frame 17 by means of clamping tongues 45 which are struck from said wall and are bent over and around the conductors in clamping engagement therewith as clearly shown in both Figs. 6 and 9. The portions of the

conductors

43 and 44 which are clamped in place beneath the clamping tongues 45 are preferably provided with protecting or shielding tubes 47 made of suitable insulating material.

As shown in Fig. 6, the rear wall 18 of frame 17 may be provided with a slot 40 and clamping tongues 45 at each lower corner thereof to take care of heating panels having the resistance terminal located at either lower corner of the panel.

As shown in Fig. 4- the lower flange 11 of wall plate 9 and the lower marginal wall 7 of back member 5 are provided centrally thereof with registering openings 49 located directly above an opening 5% formed in the top wall of a junction box 51. The box 51 is formed with an open front side secured to the rear side of the lower portion of wall plate 9 over a wall plate opening 52 normally closed by a removable cover 52a. The

heating panel conductors

43 and 44 are passed through said openings 45 and 5t? into junction box 51 and are there connected to circuit wires (not shown) which are passed into the junction box through another opening 53.

The heating-panel assembly described in the foregoing is designed to be mounted in a wall recess with the back member 5 and junction boX 51 occupying said recess and the outwardly projecting portion of wall plate 9 covering the wall surface bordering said recess. The provision of the junction box 51 and the insertion therein of the heating-

panel conductors

43 and 44 and the leads coming from the energizing circuit enables the electrical connection and disconnection of the heating-panel to be conveniently accomplished without any disturbance of the position or mounting of the panel.

The clamping tongues 45 prevent the transmission of pulling strain to the

electrical terminal connections

41 and 42 and thereby minimize danger of the electrical circuit being accidently broken at these connections.

The hereinbefore described method of mounting heating panel 27 in frame 17 also simplifies and facilitates the placement and removal of said panel and is of considerable advantage from both the production and main tenance standpoints.

In order to prevent over-heating and burning out of the electrical resistance 39 it is usually desirable to interpose a thermostat switch in the electrical connections between the heating panel and the source of electrical energy to which the panel is connected. To this end a thermostat switch 54 is mounted on the rear wall 18 of frame 17 opposite a rearwardly offset portion 55 provided in the rear wall 6 of back member 5 to accommodate said switch. This switch is connected in series with the source of electrical energy and one of the

terminal connections

41 or 42 of the heating panel resistance 39 by means of either conductor 43 or conductor 44.

A wire guard or grill 57 is preferably mounted in front of the heating panel 27 as indicated by dotted lines in Fig. 4. This grill is formed with outwardly directed frame member terminals 58 which are fitted in opening 59 of back member 5 to anchor the grill in place.

In the operation of the heater shown in Figs. 1 to 10 inclusive convection air currents flow between the heating panel 27 and the frame 17 and between the frame 17 and the back member 5. The heat reflecting surfaces of frame 17 and back member 5 are preferably highly polished to give high heat reflecting etficiency.

Fig. 11 illustrates a modified assembly which may be secured flatly against a wall surface or may be used as a portable heater. In this modification the mounting of heating panel 27 in frame 17 and the mounting of the latter in back member 5 remains unchanged but the previously described wall plate 9 is replaced by outwardly p directed flanges 61 formed integral with the marginal walls 7 of back member 5. In this case the back member 5 is housed in a sectional panel construction comprising front and

rear panel members

63 and 64. The front panel 63 presents an apertured front plate 65 and rearwardly directed top, bottom and side marginal walls 66. The rear panel 64 presents a rear wall plate 68 and forwardly projecting the flanges 69. The two panel mem bers are assembled in telescoping relation with the side marginal walls 66 of front panel 63 overlying and detachably secured by screws or other fastening means, to the side flanges 69 of rear panel 64. The back member 5 is carried by the front panel 63, being secured to the front plate 65 of said front panel by means of the flanges 61 and fastening screws 70.

The assembly shown in Fig. 11 is conveniently installed as a wall heater by anchoring the rear plate 68 of panel 64 to the surface of the wall and then assembling therewith the front panel 63 carrying the back member 5, the frame 17, and the heating panel 27. During installation of panel 64 the power line lead conductors (not shown) are passed into a junction box 72a having an open front secured to panel 64 over a panel opening 72b. This opening 72b is positioned behind an opening 73a in front panel member 65, said opening 73a being closed by a removable cover 74. A room temperature thermostat, represented by a gas bulb 75a and contact box 75b, is mounted in the lower portion of the panel structure afforded by the

panel members

63 and 64. The electrical resistance element of the heat radiating panel 27 embodied in the installation, shown in Fig. 3, is connected across the power supply in series with the switch 54 and the room thermostat, these connections being conveniently made without disturbing the heat radiating panel by bringing the power line leads to the junction box 7211 which is accessible through openings 72 and 73a. The room thermostat is exposed to the temperature of the atmosphere in which the unit is installed by providing suitable air slots (not shown) in the panel 64.

Fig. 12 illustrates a further modification which is substantially the same as that shown in Fig. 11 except as regards the mounting of the heating panel 37 in back member 5. In the arrangement shown in Fig. 12, the frame 17 is omitted and the heating-panel supporting insulators 23 are arranged directly in the corner portions of back member 5 in contact with the rear wall 6 of said back member and are retained in place by removable corner cover plates 71, the latter being secured to the marginal walls 7 of the back member by screws '72 and angles 73. A heat reflector 75 in the form of a very thin piece of highly polished material, such as steel or aluminum, is interposed between the heating panel 27 and the rear wall 6 of back member 5. Reflector 75 is mounted in place in spaced relation to heating panel 27 and the rear wall of back member 5 by loosely fitting corner portions of the reflector in grooves 76 of insulators 28 so that the reflector is free to have a limited floating movement relative to said insulators. Reflector 75 is separated from heating element 27 by a relatively large air space '77 through which convection air currents flow but is separated from the rear wall of back member 5 by only a relatively small air space 78, of the order of through which there is little or no flow of con vection air current. By making reflector 75 of very thin material and mounting it in the floating described the danger of the reflector buckling into short-circuiting contact with the electrical resistance element of heating panel 27 is eliminated. The thinness of the reflector reduces to a minimum the temperature differential between the two sides of the reflector and this, plus the floating mounting of the reflector to allow it to expand and move freely, substantially eliminates buckling of the reflector.

Reflector '75 is equipped with ceramic insulating spacers 79 which maintain it in spaced relation to the rear wall 6 of back member 5.

The arrangement shown in Fig. 12 enables the overall I,

depth of the unit to be drastically reduced. The replacement of the frame 17 by the reflector 75 also provides a cheaper unit in which the reflector reflects back over 80% of the heat rays received from the heating panel 27 The unit shown in Fig. 12 is installed and connected to the power supply in the manner described in connection with the unit shown in Fig. 11.

The unit shown in Fig. 13 is similar to that shown in Fig. 12 but is designed for installation in a wall recess in a manner similar to the described installation of the unit shown in Figs. 1 to inclusive. In the arrangement shown in Fig. 13 the

panel members

63 and 64 and the back member flanges 61 are dispensed with and the back member 5 is directly installed in the wall recess by fastening the rear wall 6 of the back member to the bottom wall of said recess by suitable fastening means. The insulators 25, carrying the heating panel 27 and the reflector 75, are retained in back member 5 by corner cover plates 31 carried by a wall plate 82 which covers the Wall surface bordering the wall recess in which the unit is installed. Wall plate 82 is provided with flanges 83 which extend into back member 5 and are secured to marginal walls 7 of said back member in the same manner as described in connection with Figs. 1 to 10 inclusive. Wall plate flanges 83 carry angle members 84 to which the cover plates 81 are removably fastened by screws 85.

The reflector 75 of the unit shown in Fig. 13 carries insulating spacers 87 which prevent it buckling into contact with either the heating panel 27 or the rear wall 6 of back member 5. The unit illustrated in Fig.

13 is also shown equipped with a temperature limiting thermostat 87 mounted directly on the rear side of reflector 75. This thermostat is connected to the power supply in series with the electrical resistance of heating panel 27 and is set to open circuit the heating panel when the temperature of the glass plate of the heating panel attains a predetermined maximum value. The rear wall 6 of the back member 5 shown in Fig. 13 is provided with a rearwardly offset portion 6a in defining a thermostat recess 6b in which the thermostat 86 is accommodated,

The reflector of the unit shown in Fig. 12 is also usually equipped with a temperature limiting thermostat corresponding to that shown at 86 in Fig. 13. When such a thermostat is used in the unit shown in Fig. 12 the rear wall 6 of the back member 5 of said unit will be shaped to provide a thermostat receiving offset similar to the offset 6a shown in Fig. 12. If there is not sufficient space between back member 5 and rear panel 64 of the unit of Fig. 12 to accommodate the said thermostat receiving offset of back member 5 this may be taken care of by providing the rear wall of panel 64 with an opening through which said offset may protrude.

What I claim is:

1. In a heater of the character described, a plate member provided with marginal walls defining a recess, panelsupporting insulators arranged in said recess in spaced relation to each other and adjacent said walls, resiliently yieldable cushioning spacers arranged between and in contact with opposing surfaces of said walls and in sulators, the cushioning spacers associated with each insulator being separated by intervening air spaces from the cushioning spacers associated with the next adjacent insulators and a heat radiating panel arranged in said recess in spaced relation to said plate member and said walls, said panel member having marginal portions thereof fitted in grooves formed in edge portions of the insulators facing inwardly from said walls.

2. A heater as set forth in claim 1 including a thin sheet of heat-reflecting material interposed between said panel and said plate member in spaced relation thereto, and with marginal portions of said sheet fitted in additional grooves formed in the last mentioned edges of said insulators.

3. A heater as set forth in claim 1 including a second plate member provided with marginal walls defining a second recess in which the first mentioned plate member is positioned in spaced relation to said second plate member and its marginal walls, and means for supporting and securing said first mentioned plate member in place within said second recess.

4. A heater as set forth in claim 1 including a second plate member provided with marginal walls defining a second recess in which the first mentioned plate member is positioned in spaced relation to said second plate member and its marginal Walls, and means for supporting and securing said first mentioned plate member in place within said second recess, at least one of the defining walls of the recess provided by said first mentioned plate member and its marginal walls being provided with opening placing the space between said first mentioned plate member and said heating panel in communication with said second recess.

5. A heater as set forth in claim 1 including a second 1 plate member provided with marginal walls defining a second recess in which the first mentioned plate member is positioned in spaced relation to said second plate member and its marginal walls, and means for supporting and securing said first mentioned plate member in place within said second recess and a panel presenting a main plate portion and marginal walls defining a third recess in which said second plate member is positioned in spaced relation to the defining walls of said third recess, and means for supporting and securing said second plate member in place within said third recess.

6. A heater as set forth in claim 1, in which the heat radiating panel comprises a glass plate to which is bonded an electrical resistance having its terminals positioned opposite an opening in said plate member and in which electrical conductors are passed inwardly through said opening and secured to said terminals, said conductors being firmly clamped against said plate member by means of clamping tongues struck from said plate member and disposed over said conductors in clamping engagement therewith.

7. A heater as set forth in claim 1, in which said spacers have portions thereof secured in grooves provided in said insulators.

8. A heater as set forth in claim 1, in which said recess is of rectangular configuration and in which the insulators are positioned at the corners of the recess and are each shaped to present right-angularly related limbs opposing right angularly related marginal walls of the recess, there being one of said spacers interposed between each limb of the insulators and the opposing marginal wall of the recess.

9. A heater as set forth in claim 1 in which the recess is of rectangular configuration and in which the insulators are positioned at the corners of the recess, said heater including corner covers secured to the marginal walls of the recess and overlying the insulators and adjacent portions of the heat radiating panel.

10. In a heater of the character described, a first plate member provided with marginal walls defining a recess, panel-supporting insulators arranged in said recess in spaced relation to each other and adjacent said marginal walls, resiliently yieldable cushioning spacers arranged between and in contact with opposing surfaces of said walls and insulators, a heat radiating panel supported in said recess in spaced relation to said plate member and said walls, by means of said insulators, a second plate member provided with marginal walls defining a second recess in which the first member is positioned in spaced relation to the defining walls of said second recess, means supporting and securing said first plate member in place within said second receess, said second plate member being adapted to be fitted in a wall recess formed in a wall of a building, and a wall plate positioned adjacent the free edges of the marginal walls of said second plate member and projecting laterally beyond said last mentioned walls to cover surface portions of the building wall bordering the wall recess in which said second plate member is fitted, said wall plate being provided with flanges overlapping and secured to the marginal walls of said second plate member.

ll. In a heater of the character described, a first plate member provided with marginal Walls defining a recess, panel supporting insulators arranged in said recess adjacent said marginal walls, a heat radiating panel supported in said recess by said insulators and disposed in spaced relation to said plate member and said walls, said heat radiating panel comprising a glass plate having bonded thereto an electrical resistance having its terminal por' tions positioned opposite an opening in said plate member, electrical conductors extending inwardly through said opening and secured to said terminals, a second plate member provided with marginal Walls defining a second recess in which the first mentioned plate member is positioned in spaced relation to said second plate member and its marginal walls, means for supporting and securing said first mentioned plate member in place within said second recess, a wall plate positioned adjacent the free edges of the marginal Walls of said second plate member and projecting laterally beyond said marginal walls of said second plate member, means securing said wall plate to the marginal walls of said second plate member, a junction box having an open front secured to said wall plate over an opening formed in the latter, said junction box and one of the marginal walls of said second plate memher being provided with aligned openings through which the conductors connected to the terminals of said electrical resistance are passed into said junction box for connection to power supply conductors insertable in the junction box through another opening formed therein.

12. A heater as set forth in claim ll, including a thermostat switch positioned between said first and second plate members and secured to the first plate member, said switch being adapted to be connected in series with said electrical resistance across the power supply by means of the conductors connected to the terminals of said resistance and to open circuit the resistance when the temperature of said first plate member exceeds a predetermined maximum value.

13. A heater as set forth in claim 1, including a second plate member provided with marginal walls defining a second recess in which the first plate member is positioned in spaced relation to said second plate member and its marginal walls, and means for supporting and securing said first mentioned plate member in place within said recess comprising angle brackets secured to the inner sides of the marginal walls of the second plate member with limbs of the brackets projecting inwardly from said walls and anchoring plates secured to said first plate member and projecting beyond marginal portions of the latter, the projecting portion of said anchoring plates being secured to the inwardly projecting limbs of said brackets.

14. In a heater of the character described, a plate member provided with marginal walls defining a recess, panel supporting insulators arranged in said recess adjacent said Walls, a heat radiating panel arranged in said recess in spaced relation to said plate member and said walls, said heat radiating panel comprising a glass plate having marginal portions thereof fitted in grooves formed in said insulators and an electrical resistance bonded to one side of said glass plate, a thin sheet of heat reflecting material positioned in spaced opposing relation to the side of the glass plate to which the electrical resistance is bonded and having marginal portions thereto fitted in additional grooves formed in said insulators.

15. A heater as set forth in claim 14, including a ther mostat switch secured to the side of the heat reflecting sheet remote from said electrical resistance and adapted to be connected in series with said resistance across a source of electrical energy.

16. In a heater of the character described, a first plate member provided with marginal walls defining a recess, panel supporting insulators arranged in said recess adjacent said walls, a heat radiating panel supported in said recess by said insulators in spaced relation to said plate member and said walls, said panel comprising a glass sheet having an electrical resistance bonded to the side thereof facing said plate member, a second plate member provided with marginal walls defining a second recess in which the first mentioned plate member is secured in spaced relation to said second plate member and its marginal walls, a thermostat switch secured to the side of the first plate member remote from said resistance and adapted to be connected in series with said resistance across a source of electrical energy, said second plate member being formed with an outwardly offset portion affording an inwardly facing pocket positioned directly opposite said switch.

17. In a heater of the character described, a plate mem ber provided with marginal walls defining a recess, panel supporting insulators arranged in said recess in spaced relation to each other and adjacent said Walls, resiliently yieldable cushioning spacers arranged between and in contact with opposing surfaces of said walls and said insulators, the cushioning spacers associated with each insulator i being separated by intervening air spaces from the cushioning spacers associated with the next adjacent insulators and a heat radiating panel supported in said recess in spaced relation to said plate member and said walls by supporting engagement of the marginal portions of said panel with said insulators.

18. A heater as set forth in claim 17, in which said spacers are composed of resiliently compressible material such as rubber.

19. In a heater of the character described a plate member provided with marginal walls defining a recess, ceramic panel-supporting insulators arranged in said recess in spaced relation to each other and adjacent said walls, resiliently yieldable cushioning spacers arranged between and in contact with opposing surfaces of said walls and insulators, the cushioning spacers associated with each insulator being separated by intervening air spaces from the cushioning spacers associated with the next adjacent insulators and a heat radiating panel supported in said recess by said insulators and disposed in spaced relation to said plate member and said walls.

References Cited in the file of this patent UNITED STATES PATENTS Thorp et a1 May 31, 1938 Burton July 4, 1950 Lamb -a Jan. 2, 1951 Elsenheimer Aug. 21, 1951 Goodman et al Mar. 11, 1952 Frere Oct. 7, 1952 Boecher, Jr. et al Dec. 23, 1952 Gaiser et al Jan. 13, 1953 Reynolds Apr. 7, 1953