US3102007A

US3102007A - Drying apparatus employing radiant panel heaters

Info

Publication number: US3102007A
Application number: US31602A
Authority: US
Inventors: Goldman David
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-05-25
Filing date: 1960-05-25
Publication date: 1963-08-27
Anticipated expiration: 1980-08-27

Description

Aug. 27, 1963 D. GOLDMAN DRYING APPARATUS EMPLOYING RADIANT PANEL HEATERS Filed May 25, 1960 2/ 1935,41/ 1;/ www 6; u

Z/ if az Z! l! 20.9 l

464 45d 20a. 46 44a 230 5 Sheets-Sheet 1 INVENTOR. DAVID GOLDMAN D. GOLDMAN Aug. 27, 1963 DRYING APPARATUS EMPLOYING RADIANT PANEL HEATERS FledMay'ZS, 1960 3 Sheets-Sheet 2 INVENTOR. DAV/D GOLDMAN Aug. 27, 1963 D. GOLDMAN 3,102,007

DRYING APPARATUS EMPLOYING RADIANT PANEL HEATERS Filed May 25, 1960 3 Sheets-Sheet 3 United States Patent O 3,162,097 DRYING APPARATUS EMPLYING RADIANT PANEL HEATER@ David Goldman, 73 E. 130th St., New York, NN.

Filed May 25, 1960, Ser. No. 31,602 7 Claims. (Cl. 361-48) Yend of the cabinet, which chamber is open at the front,

adjacent the door, and having radiant panel heaters at the inside of the side and top walls thereof, with track means on the door and on the bottom wall of the chamber yto facilitate loading articles into the chamber for drying by said heaters.

Another object of this invention is to providefin a drier of the character described, separate signal means to indicate which of the individual heaters are operating and also an on and off switch and signal means to indicate when said switch has been actuated.

Yet a further object of this invention is to provide in a drier of the character described, an adjustable thermostatic safety switch to de-energize the heaters, automatically When the temperature in the chamber reaches a predetermined point.

Still another object of this invention is to provide in a machine of the character described, a thermal switch for each of the panels, which is normally open and which closes when its associated panel heats up, and electric signals controlled by said switches whereby to indicate, individually, which of the panels are operating and in heated condition.

l A still further object of this invention is to provide a drier [of the character described in which said chamber has openings a-t the bottom for passage of thermocouplers from the panels Ito the thermal switches 4and the'safety 'thermostatic switch and also for passage of air, and said chamber having heat insulation material on its top wall, and also openings to permit circulation of air through v said chamber.

Still another object of this invention is to provide in end of said space being covered by a perforated cover plate, the side walls `of lthe cabinet being spaced from the side walls of the chamber, and said cabinet being open at the rear, and the insulated top of the chamber constituting the upper end of the drier.

Yet another object of this invention is to provide a drier of the character described in which the cabinet is mounted on vertically adjustable legs `and said cabinet has space below said chamber to house the electric controls for the drier, `and said cabinet having a door at its front side, below the downwardly swinging door to give access to the electric control, and said cabinet being furthermore open at its lower end to enhance the circulation of air to and through the drying apparatus.

The radiant heaters employed in the Vpresent drier Vare-preferably of the type in which a glass panel has an electro-conductive lm that serves as a resistance element and heats the glass panel. Such heaters are manufactured by Corning Glass Works of Corning, New York, and are called by them Pyrex Panel Heaters. fIn these heaters the radiant energy source is a tempered boro- JZJB? Patented Aug. 27, 1963 silicate glass panel. IOne surface of the glass has an electro-conductive lm that serves :as a resistance element and heats the glass. When an electric current is applied to the lm, the entire glass panel heats and emits long wave radiation. The glass is a highly elfective emitter. The conducting lm is a very poor emitter, so it serves as a reflector .to direct most of the energy down to the Work area. The radiation that leaves the film surfaces is directed back by an aluminized deflector forming part of the heater. The result is that a great part of the radiant energy is directed onto the work area.

Practically all the energy emitted by the panel is of the long wave variety that is absorbed by practically all materials.

A still further object of this invention is to provide a strong, rugged, durable and space saving drier of the character described which shall be relatively inexpensive to manufacture and maintain, which shall dry with a uniform heat, and which shall yet be practical and eicient to a high degree in use.

yOther objects of this invention will in part be obvious and in part hereinafter pointed out.

The invention -accordingly consists in the features of construction, combinations of elements, and arrangement of parts, which will be exempliied in the construction hereinafter described, and of which the scope of invention will be indicated in the following claims.

In the accompanying drawings in which is shown an illustrative embodiment of this invention,

FIG. 1 is a perspective view of a drier embodying the invention, with parts broken away and in cross section;

FIG. 2 is a cross-sectional view taken on line 2-2 of FG. l;

FIG. 3 is a partial cross-sectional View taken on line 3-3 of HG. 1;

FIG. 4 is a partial perspective view of the upper end of the drier with parts broken away and in cross section;

FIG. 5 is a cross-sectional view taken on line 5-5 of FIG. l;

FIG. 6 is an exploded View of one of the radiant panel heaters; and

FIG. 7 is a wiring diagram of the electric circuit for the driers.

Referring now in detail to the drawings, 1?` designates a drier embodying the invention. Said drier comprises a cabinet 11, with a heat chamber 12 therein.

Said cabinet 11 may be made of sheet metal and has a front Wall 13 and side walls 14. Extending from the rear ends of the side walls 14, Ito-ward each other lare anges 15. At the upper end of the front wall 13 is a rearwardly extending horizontal ange 16. The upper ends of the side walls 14 have at their forward portion, inwardly extending horizontal flanges 17 in Ithe plane of flange 16.

The front wall 13 of the cabinet has an upper rectangular opening 18 for an insulated door 19, and Ia lower rectangular opening 20 for a lower door 21. The door 19 is hinged at its lower end `19a to the lower edge of the door opening 18. 'Ilhe front wall of the cabinet is provided with an inwardly extending channel 13a at the sides and top tto receive flanges 19a in the door 19.

On the upper end of the outer side of the door 19 are brackets 25 to which are hinged rods 26 telescoped Within tubes 27 hinged to brackets 2S at the lower end of the front wall. When the door is swung down to open position, it will be maintained in horizontal position by the tubes 27.

A handle 30 pivoted to the door, as yat 31, has a latch 32 to engage la slot or keeper on the front wall to keep the door up and in closed position. On the inside of the door are a pair ofinner parallel ltracks 33 and outer tracks 34. When the door is down, Wheeled trays or baskets of articles to be dried, may be slidably moved f ktnansverse` bar 41. Flanges 42 extend inwardly from the lower ends of the side walls 14. Thus, the lower end .of the cabinet is open. Mounted

cn flanges

40, 41, '42 is a support lframe 43 comprising 4a front flange 44, a rear flange 46, side flanges 46 and top horizontal anges tta,

46a and 46a extending from said front side and rear flanges, respectively.

The front door 21 is hinged to wall 13, as at 21a and is provided with a handle 2lb and is removable. The front wall has inwardly extendin-g flanges Zta at the four sides of opening 211 rto receive said door.

The chamber 12 may be made of sheet metal and comprises a topwall Si?, side walls 51, a rear wall S2, a

bottom wall 53. At its front wall 54, said chamber'has llanges '54a contacting the door opening 18 at all four sides. The chamber t) is supponted on angle shaped brackets 5S tixed to the inner sides `of the side walls 14 of the cabinet. Side walls l51 of the cham-ber 12 are spaced inwardly from the side walls 14 yof the cabinet. Front wal-l 54 is spaced from front wall 13` of the cabinet. Rear wall 52 of the chamber is spaced from rear anges 15 of the cabinet.

Bottom wall 53 of the chamber has four sloping triangular. sections 56' inclined downwardly to a central apex which is formed with a drain opening `57. 'Ilhe sides of bottom wall 53 rest on the brackets 55'. At its vfront end, bottom wall S3I has two open sleeves 60 at eachr side, passing through openings in the wall,v vertically.

At its rear end, said bottom wall has a pair of vertical sleeves 61 passing vertically up therethrough one side of the chamber only.

In the chamber 12 and near the bottom wall 53 are A a pair of transverse horizontal channels or other supporting bars 62. These are welded or otherwise secured `to the side walls 51 in spaced relation. The ilanges of v the channels project downwardly as shown in `FIG. 4 lof the drawing.

Welded to the top of bars 62 are inner tracks 63 and outer 'tracks 64. These are horizontal and run from `front to rear and are in alignment with the .tracks 33,

66a registering with openings 65a, 50a. The top surfacel of steel plate 66 is just below the upper edges 14a of side Walls 1t. The asbestos layer 65 covers the upper end of front wall'54 of `chamber v12 as at 651;Y (above Y the door opening 18)v and extends, .as at 65C, 'betweeny flange `Srta of the `chamber and channel 13a of the front wall, at the upper end of the door opening. A perforated Vcover plate attached to the upper end 'of the cabinet covers the space between lthe top Iof the chamber 12 and ythe front wall 13 of the cabinet.

At the central opening 57 of bottom wall 53 of chamber 12 is a drain nipple 57a. Air may circulate through opening orsleeves 60, 61 upwardly through

openings

50a, 65a, 66a.

Attached 'to thefinside of side walls 51 of chamber 12 Vby spring clips are side industrial radiant heaters 81,

and attached to the underside of top wall 511 by such A clips lis an industrial radiant heater 31. preferably welded to the chamber.

r[he radiant heaters may be of the type kmanufactured by Corning Glass Works, Corning, NY., and are called by them Pyrex Panel Heaters.r

One of such panels is shown in FIG. 6 in exploded view. The same comprises a frame 82 supporting a tempered borosilicate glass panel 83. The rear surface of the glass has an electroconductive film that serves as a resistance element and heats the glass panel. The panel rests on cushions 84. disposed between it land the frame Contacting the rear of the panel are bus bar assemblies 85', reach contacted `by an insulator 86 held by ya contact The clips are `holder channel `37. Back of channels and panel 83 is an aluminized reflector 38 which is backed by insulation 39 held in place by a cover-9tl which tits over the frame 82. No claim is made to the heater per se. Asbestos covered wires 91 extend to an electric box 92 coveredby a box cover 93. 'llhe box 92 maybe attached to the -chamber 12 by an attachment plate 94.- 'Ilhe bus bars S5 contact the lilm on the glass panels. The wires 91 may pass kthrough the chamber walls, for the purpose hereinafter appearing.

Attached yto the lower trame 43 and below the chamlber 12 there are vertical brackets 111i) supporting a main `line switch box 1M with fuses therein, an electro-magnetic starting box 1112, an adjustable thermostatic switch 1th?)` and three thermal switches 11141, '1115,' 1116. Switch 103 :has terminals 11136:, 1635; switch 11M has terminals 104m 1Mb; switch 15has terminalslla, 1tl5b, and switch 1116 has terminals 11165:, 1Mb. l

p The thermostatic switch 1% is normally closed and is adjustable to lopen when heated to a predetermined temperature by a thermocouple 107, which extends therefrom and passes through a sleeve 61B at the left ott theicharmlber 12 lfor connection to the frame of panel heater 81 on the left side wall.l

Said switch box 1111, starting box 1112, land switch boxes ,v 1%, 16d, 10S, 1% are connected by conduits, to be described herebelow, for the required wiring which will be .explained hereinafter.

On the `front wall 13 bnf the cabinet 111, above'the door 19, is an On and Ofi switch 1111, an On and Oli signal light Vll11,.a signal light 112 to indicate ,that the left heater 81 is'operating, a signal light 113 to indicate that the top heater 31 is operating, and la signalV light 114 to indicate that the right heater 81 is operating. The switch and the signal lights (or other electric sigria-ls) 111, 112, 113, 114` are ranged in `a row, as shown in the drawing.

A thermocouple 115 extends from the thermal vswitch i 11M to the left heater 81, also passing through the sleeve J611 at the left side of the chamber 12, Athermocouple 116 extends from the thermal switch 105 to the top heater 81 `and a thermocoup-le 11'7 extends `from the thermal switch 1% to the right heater 81. These thermocouples pass through the sleeve 60 and a sleeve 61.

Referring now to the wiring diagraml of FIG. 7, there is shown an A.C. source 220` volts,k 3 phase, 4 wire powerr system comprising conductors kW1, W2, W3 :and neutral conductor N. Y

The conductors W1, W2, W3 are

connectedto input terminals

121a, 122a,.fand 123g, respectively, of the main yline switch box 101; corresponding

outlet terminals

121b, 122b, and 1235 are connected by

conductors

11S, 119 and 120, respectively, to input contacts L1, L2 and L3 of the ,starting box 1112., Fuses 12.1, 122 and 123 are inserted,

respectively, between the input' and

outlet terminals

12111 and 121k, 122a and 122b, and 123e and 123k. The

starting box 102 has output contacts T1, T2 and T3. `When the electro-magneticcoil 12S is energized, in a manner to be later described, a triple blade movable con- `tactor (not shown) completes the circuit connections V.from the input contacts L1, L2 and L3 to the output contacts T1, T2 yand T3; respectively. Switch L1T1, L2T2 ,and

`L3T3 controlled by the operating coil 125 constitute an ductor 127 to one side ot the thermostatic switch 101%.l

The other side of said switch 10'3 is connected 'by a conductor l123 to one terminal 129 of the On and Oli switch 110. Said terminal is connected by a conductor 130 to one terminal 131 of 'the signal light 111. The other terminal 132 of the signal light 111 is connected by a common return conductor 133 to the iirst terminal 125a of the electro-magnetic coil'll25.

Said terminal 129 of the On and Oli switch 1101s connected by a conductor 13d to terminal 10aa or thermal switch 104. The other terminal 104b of switch 104 is connected 4by a conductor 135 to terminal 136 of theA .signal light 112. The other terminal 137 of said 'signal iight 112 is connected by la conductor 138` to the cornmon return conductor 133. Terminals 10aa and 105a d the thermal switches 104 'and 105 are interconnected by a conductor 139 and terminals 1t15a and 10641 of thermal switches 105 and 106 are interconnected by a conductor 140. Terminal 101511 of thermal switch 105 Iis connected by a conductor 141 to terminal 142 of signal light 113i. The other terminal 113 of said signal light 113 is connected by conductor 144 to the common return conductor 13-3. The other terminal 106]: or thermal switch 106 is connected by a conductor 145 to terminal 146 of the signal light 114;. The other terminal 147 of signal light 114 is connected by a conductor 1118 to the common return conductor 133. The other terminal 150 oi? the On and O switch 110 is connected by a conductor l151 to conductor 120, which r-extends `from the fuse 123i.

The left panel theater 81 has terminals 160, 161 (in box r92 thereof); the top panel heater S1 has terminals 162,

163 and the right panel heater 811 has

terminals

164, 165.

Terminal 160 of the letft heater 81 is connected by conductor 166 to output contact T1 and a conductor 167 to output Contact T2 of the starting. box 102. Terminal A162 ot" the top heater 81 is connected by a conductor 169 to output contact T1 and terminal 163 thereof is con- Y nected by a conductor 16S to output contact T3 of they starting box. Terminal 164 of the right heater is connected by a conductor 170 to output contact T2 vand terrninal 165 of `said heater is connected by ia conductor -171 to output contact T3 of the Istarting box.

v On`and Off switch '110, may pass upwardly through conduit 205 which leads to the space between the chamber 12 and front -wall'13of the cabinet. The boxes of thermal switches 104 and 106 are connected by conduits 206 to the box of thermal switch 1015. The box of said switch 105 is connected toa junction box 208, which is connected by conduit 209 to fuse box 101.

The operation of the electrical equipment will now be described. When the On and Oft switch 110il is closed, a single phase circuit is. completed through the electromagnetic starting coil 125 and through the northe main line switch and Amally closed adjustable thermostatic switch 103. This circuit is from one output terminal 123b of the main line switch and -fuse box '1 over a conductor 151 to one terminal 150 of the On and Ott switch 110; thev other iside of this. circuit is `from the other terminal 129 of the On and Ofi switch over a conductor 128 to one terminal 10Go of the thermostatic switch 103, from the other terminal 103b over a conductor 127 to one terrninal b of the electro-magnetic coil 125 in the starting box 102, irom the other terminal 12ga of this coil over a conductor 126 to the neutral conductor N of the power supply. Energization of the electromagnetic coil 125 causes the movable contactor (not shown) in the starting box 102 to bridge the respective pairs of inlet yand outlet contacts L1 and T1,L2 and T2, and L3 and T3. This completes the circuits for the right, left and top panel heaters 81.

The circuit for the signal light 111 is also completed. This circuit is on one side from the terminal 129 of the On `and O11 switch 110 overa conductor 130 to one terminal of this signal light; the other side off this circuit is `fro-1n the other terminal 132 of the signal light over the common return conductor 133 to the terminal 125:2

of the electromagnetic starting coil 125 and over the conduct-or 126 to the neutral conductor N of the electrical power supply.

The circuit-for the left panel heater 81 is `from the power conductor W1, to input termi-nal 121a of the main line switch and fuse box 101, froml the outlet terminal 121b of the latter over the conductor 118 to the input contact L1 of the starting box 102, and from the outlet contact T1 of the latter over the conductor 166 to the terminal 160 of the heater; the other side of this circuit is from the terminal 161 of the heater over the conductor 167 to the outlet contact T2 of the starting box, Itfrorn the inlet contact L2 of the latter over the conductor 119 to the outlet terminal 122b of the main line yswitch and fuse box 101, and from the inlet terminal of the latter tothe power conductor W2.

Similarly, the circuit for the right panel heater 81 is -tlirom the power conductorWZ to the input terminal 122:1

of the main line switch and fuse box 101, from the outlet terminal 12217 of the latter over the conductor 119 to the input contact L2 of the starting box, and from the outlet contact T2 of the latter over the conductor 170* to the terminal 164 of the heater; and other side of this circuit is .ffrom the terminal 165 of the heater over the conductor 171 to the outlet contact T3 of the starting outlet contact T3 of the ylatter over the conductor 168 to the terminal 163 or the heater; the other side of this circuit is from the terminal 162 of the heater over the conductor 169 to the outlet contact T1 of the starting box, from the inletcont-act L1 of the latter over the conductor 118 to the outlet terminal 121b of the main line switch and fuse box 101 and yfrom the inlet terminal 12111 of the latter to the power conductor W1.

When any one of the panel heaters S1 reaches a lpredetermined temperature, the corresponding thermo-

couple

115, 116, will energize the respective normal-ly open

thermostatic switch

104, 105 or 106 to close the circuit for the

respective signal light

112, 113 or 114. Closure of the thermostatic switch 104 will complete the circuit for the signal light 112. This circuit is on one side from the terminal 129 of the On and Ott switch 110 over the conductor 134 to one terminal 10451 of the thermostatic switch 10ft and from the other terminal of the lswitch over a conductor 135 to one terminal 136 of the signal light; the other side of this circuit is from the other terminal 137 of the signal rlight over a conductor 133 to the cornrn'on return conductor 133.

Similarly, closure of the thermostatic switch 10S will Aheater circuits.

. in a limiting sense.

of the On 'and Off switch 11(1over the conductor 134 to one terminal lima of the thermostatic switch 104, :trom` the other terminal liltb of this switchover the conductor 139 toy one terminal 111501 of the thermal switch 105, [from responsive to the interna-l temperature of the chamber I theother terminal 1i5b of vthe latter switch over a conl iductor Mito one terminal 142 of the signal light 113; the other `side of ythis circuit 'is from the other terminal" 143 of the si-gnal light :over a conductor 14d to the com' mon return conductor 133, f n j Likewise, closure of the thermostatic switch 166 will complete the circuit for the signal light 114. 'I'his cir-. cuit is from the terminal of the On and Ott switchllti over the conductor 134 to one terminal lliila of the ther mostatic switch 101i, over the conductor 139i to one terminal 105:1 of the thermostatic switch 10S, over the conductor 140 to 'one terminal 1.06ct o'f the thermostatic switch 106, and ffrom the othcrterminal71tl6b of' the latter thermostatic switch over a conductor 145 to one terminal 146 of the signal light 114; the yc-ther'side of again, as the temperature goes down below a predetermined degree, and the

corresponding signal light

112, 113,` or 114 will be deencrgizei to indicate which heater, or heaters, are not operating.

It the temperature in the chamber 12" goes up beyond .la predetermined degree, the thermostatic switch 103- will open to defenergize the electro-magnetic starting coil 125 to disconnect the input contacts, L1, L2, L3 from the outlety contacts T1, T2, T3, respectively, and thus to open` the This is a safety rfeature of the apparatus. t will thus be seen that there is provided an apparatus in which the several objects of this invention are achieved, andY which is well adapted to rmeet the conditions 'of practical use. y f

As possible `embodiments might be made of the above invention, `and gas various changes might be made in the i mlbodiment above set forth, it is to be understood that n all matter herein setl forth ior shown inthe accompanying drawings, kis to be interpreted as illustrative and not I claim: l. In a drier, in combination, a cabinet having a front Vwall and side walls, and upper, l-ower and rear ends, a

the cabinet, radiant heating ele-ments in at least 'two walls of said heating chamber, said elements each including a frame and `a cushioned, tempered glass panel having an electro-conductive lm serving las a heating element on its rear surface in said frame, an electro-magnetic switch mounted within saidy cabinet, Ia ycircuit for each heating v element through theyelectro-magneticswitch to one phase power supply line through the operating coilfof .the electromagnetic switch and thefOn and .Oif switch.

, 2. The combination according toclaiml in which the` v energizingy circuit for the electro-magnetic switch includes a thermo-sensitive switch and means inthe chamber and to control said thermo-sensitive switch.

.j 3. ,The combination fa-ccordingto claim l Vin which al K. signal light is provided for indicating the open orclosed l condition of the"Oii and On switch and-one side ofY the circuit for the signal light is vcommon to one sideof the circuit :of the Ofi and On switch andthe other side of the circuit for the signal light is` comprised -by a return conductor'to `the electrical power supply line.

4. The combination according topclaim 1v in which a' signal light is provided-for each heating element to indicate the `on or 'off condition of the heating element and the circruit for eachsignal light is comprised-in part on one side 'by a conductor from one terminall ofthe .Off andfOn switch to the respective signallight 'andis corny prised on the 'otherv side by `a return conductor `from thel signal-light to the electrical power supply line. l

5. `The combination according to claim -1 in which a heating element and controlling `said switch,l is provided,

i and the circuit for each signal light isl comprised in part line.

on one side by a conductor from one terminal of the On and OE switch to the respective thermo-sensitive switch rand la lconductor from the 'latter to the vrespective signal 6. The combination according tol'clairn l vin which -a signal light is provided for each heating element to indiof.theelectricalzpower supply line, an On and Oli switch mounted within the cabinet, and an energizing circuit Ifor the electro-magneticswitch from the electrical cate the'on orl ot condition of the heating element, aV

thermo-sensitive switch is provided for each signal light, a thermocouple is positioned inl close proximity to each heating element yand' connected by an electrical circuit to the respective lthermo-sensitive switch, and thecircuit for each signal light is comprised in part .on one side by aI j conductor .from Kone `terminal of the On andpvOi l switch to the respective thermo-sensitive switch and aconductor from thelatter tothe respective signal light and is'` `comprised on the other side by a return conductor from Ithe signal light to the `electrical power supply line.

7. The combination of claim 5, in which the energizing circuit foi-the electromagnetic switch includes another* thermo-sensitive switch, and means in 4the chamber 'and responsive to the internal temperature ofthe chamber, yto

control said other thermo-sensitiveswitch.v

, References Cited in the tile of this patent UNITED- STATES PATENTS 1,432,176 Frohring et al. Oct. 17, 1922 ,1,620,602 Mayer Mar. 8, 1927 1,676,876v Stannard .Iuly 10, l9'28 2,415,768 y Shaw Feb. 1l, 1947 l 2,571,218A Butterof-; 'Oct. 16, 1951 2,885,526 'Paulding v May 5, 1959

Claims

1. IN A DRIER, IN COMBINATION, A CABINET HAVING A FRONT WALL AND SIDE WALLS, AND UPPER, LOWER AND REAR ENDS, A FRONT DOOR ON SAID FRONT WALL, A HEATING CHAMBER IN THE CABINET HAVING WALLS SPACED PARALLEL TO AND INWARDLY FROM SAID WALLS AND ENDS OF THE CABINET, AND INCLUDING A BOTTOM WALL FORMED WITH A DRAINAGE OPENING, AND A FRONT WALL HAVING A DOOR OPENING CLOSED BY THE FRONT DOOR OF THE CABINET, RADIANT HEATING ELEMENTS IN AT LEAST TWO WALLS OF SAID HEATING CHAMBER SaID ELEMENTS EACH INCLUDING A FRAME AND A CUSHIONED, TEMPERED GLASS PANEL HAVING AN ELECTRO-CONDUCTIVE FILM SERVING AS A HEATING ELEMENT ON ITS REAR SURFACE IN SaID FRAME, AN ELECTRO-MAGNETIC SWITCH MOUNTED WITHIN SAID CABINET, A CIRCUIT FOR EACH HEATING ELEMENTS THROUGH THE ELECTRO-MAGNETIC SWITCH TO ONE PHASE OF THE ELECTRICAL POWER SUPPLY LINE, AN "ON" AND "OFF" SWITCH MOUNTED WITHIN THE CABINET, AND AN ENERIGZING CIRCUIT FOR THE ELECTRO-MAGNETIC SWITCH THE ELECTRICAL POWER SUPPLY LINE THROUGH THE OPERATING COIL OF THE ELECTROMAGNETIC SWITCH AND THE "ON" AND "OFF" SWITCH.