US2917617A - Heating devices - Google Patents

Description

Dec. 15, 1959 H. GREUBEL HEATING DEVICES 2 Sheets-Sheet 1 Filed April 28, 1958 ATTX Dec. 15, 1959 A. H. GREUBEL HEATING nsvrcss Filed April 28, 1958 2 Sheets-Sheet 2 awe/V702 A LFRE 0 H. 6250351.

United States Patent HEATING DEVICES Alfred. Henry Greubel, Aifton, Mo.

Application April 28, 1958, Serial No. 731,245

1 5 Claims. (Cl. 219-39) This invention relates to improvements in heating devices. More particularly, this invention relates to improvements in electrically-operated heating devices.

It is therefore an object of the present invention to provide an improved electrically-operated heating device. Electrically-generated heat is the cleanest and most readily-controlled kind of heat; but nevertheless, electricallygenerated' heat has not yet attained the acceptance that it should properly attain in the heating of houses and other buildings. The present invention provides an electrically-operated heating device that should foster the acceptance of electrically-generated heat in houses and other buildings. That heating device includes a liquidtighttank which holds a liquid dielectric and which has electrically operated heating elements immersed in that dielectric. Air is passed over the exterior of that tank to absorb the heat which is generated by the electricallyoperated heating elements and which is transferred to the walls of the tank by the liquiddielectric; and that air is then used to heat the house or other building.

The'tankprovided by the present invention is equipped with external fins that provide recurrent changes of surface. Thosefins coact with partitions, which are disposed adjacent the outer edges of those fins, to guide the air and force that air to recurrently change direction. As a result, the air isnot permitted to stratify but is forced to presentall portions thereof to the surfaces of the fins. Inthis way, optimum transference of the heat from the fins to theair is attained. V

Theliquid-tight tank provided by the present invention is elongated, and it is longer than the outlet of the blower for'the air; andconsequently only a part of the air from the blower can be directed squarely against the tank. The rest of the air is, however, enabled to engage thetank and absorb heat therefrom because the fins on that tank are formed'to provide areas through which the rest ofthe air can pass-longitudinally of the tank before it passes between and isguided by the fins. In this way, full utilization of the air is assured.

As the rest of the air moves longitudinally of the tank, that air will tend to rise. The present invention compensates for the rising of that air by disposing the electrically-operated heating elements within the tank so they are inclined to the horizontal. The lowermost portions of the heating elements are located in register with the outlet of the blower and the uppermost portions of those heating elements are located at points remote from that outlet. In this way the air will begin to engage the tank intimately at those points on the tank which are closely adjacent the heating elements.

Other and further objects and advantages of. the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description apreferred embodiment of the present invention is shown and described but it is to be understood that the drawing and accompanying description are for the purpose of illustra- "ice tion only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing,

Fig. 1 is a side elevational view of one embodiment of electrically-operated heating device that is made in accordance with the principles and teachings of the present invention,

Fig. 2 is a partially broken-away, front elevational view of the heating device shown in Fig. 1,

Fig. 3 is a partially sectioned, plan view of the heating device shown in Figs. 1 and 2,

Fig. 4 is a partially sectioned side view of the tank of the heating device shown in Figs. 1-3,

Fig. 5- is a partially sectioned front view of the tank of the heating device of Figs. 1-3, and

Fig. 6 is a circuit diagram for the electrically-operated heating device of Figs. 1-3.

Referring to the drawing in detail, the numeral 10 generally denotes an embodiment of electrically-operated heating device that is made in accordance with the principles and teachings of the present invention. That heating device includes a housing which has two trapezodialsides 12, and one of those sides is well shown in Fig. 1. Extending between the two trapezoidal sides 12 of the heating device 10 are a rectangular front wall 14 and a rectangular rear wall 16. The sides 12 and the front and rear. walls 14 and 16 will be suitably secured together in a manner known to those skilled in the art. Preferably, however, one of the sides 12 will be secured to the front and rear walls 14 and 16 by screws or bolts so that side can be removed for the insertion of the components of the heating device and for any subsequent checking and maintenance of those components.

The numeral 18 denotes a generally rectangular frame that is supported by the rear wall 16 of the heating device 10; and'that frame is in register withand bounds an opening in that rear walii That frame is dimensioned to accommodate the cold air return duct 20 of the house or other building in which the electrically-operated heating device 19 is installed. The numeral 22 denotes a frame at? the top of the heating device 10, and that frame is in register with a horizontal opening defined by the upper edges of sides 12 and of front and rear walls 14 and 16. The frame 22 is dimensioned to accommodate the hot air duct 24 of the house or other building in which the heating device 10 is installed.

Depending downwardly from the horizontal opening defined by the upper edges of sides 12 and of front and rear walls 14 and 16 are two elongated partitions 26 and 28. Each of those partitions has a flange at the top edge thereof, and those flanges are directed outwardly and away from each other. Those flanges on the partitions 26 and 28 narrow, andbound the front and rear portions of, the horizontal opening defined by the upper edges of sides 12 and of front and rear walls 14 and 16. Those flanges are, as indicated particularly by Fig. 1, adjacent the bottom of the frame 22 of the heating device It).

The numeral30 denotes amulti-vane blower of standard design and construction; and the outlet of that blower is secured to the lower edges of the partitions 26 and 28. The outlet of the blower 30 is wider than the space between the upper edges of the partitions 26 and 28; and

the partitions 26 and 28 are bent, as shown particularly in Fig. 1, to enable the lower edges of those partitions to be secured to the outlet of blower 30.

Asindicated particularly in Fig. 2, the outlet of the blower 30 is shorter than the partitions 26 and 28. Consequently, sheet metal baffies 31 are provided; and those bafiles extend between the outlet of the blower 30 and thetrapezoidal sides 12 of the heating device 10. Those 3 baffles prevent short-circuiting of the air from the outlet to the inlet of the blower 30.

The shaft of the blower is denoted by the numeral 32, and that shaft has a sheave 34 fixedly secured to it. An electric motor 36 is mounted on a platform, and that platform is hingedly secured to the housing of the blower 30 by a pivot 38. As shown in Fig. 1, that hinge is adjacent the right-hand edge of the platform; and consequently the motor 36 and its platform tend to rotate in the counterclockwise direction about the pivot 38, as that motor, platform and pivot are viewed in Fig. 1. A flexible belt extends around the sheave 34 of the blower 30 and also extends around the sheave on the shaft of the motor 36. The tendency of the motor 36 and its platform to rotate in the counterclockwise direction about the pivot 38 supplies the tension needed to keep the belt 40 taut and thereby avoids slipping of that belt relative to either of the two sheaves.

The numeral 42 denotes two elongated rods which extend between and project outwardly beyond the partitions 26 and 28. Suitable fastening elements are provided for the ends of the rods 42, and those fastening elements keep those rods from moving out of engagement with the partitions 26 and 28. Before the rods 42 are assembled with the partitions 26 and 28, and before the fastening elements are mounted on the projecting ends of those rods, tubular sleeves 44 are telescoped over those rods and are disposed between the confronting faces of the partitions 26 and 28. Those tubular sleeves coact with the rods 42 to serve as roller bearings; and those sleeves and those rods support the liquid-tight tank 46 of the heating device 10.

The tank 46 is rectangular in plan, as shown particularly in Fig. 3, it is generally rectangular in side elevation, as shown particularly in Fig. l, and it is rectangular in front elevation, as shown particularly in Fig. 2. That tank is provided with deep fins 48, and those fins are generally vertically directed. Those fins are non-linear and are formed to define zigzag air passages between them, as shown particularly by Fig. 2. The tank 46 is slightly shorter than the horizontal dimensions of the front and rear walls 14 and 16 of the heating device 10, and this is desirable because it provides narrow air passages between the sides 12 of the heating device 10 and the endmost fins of tank 46. Blocks 47 of thermally insulating material are disposed between the ends of the tank 46 and the sides 12 of the heating device 10, and those blocks overlie the ends of tank 46 but do not overlie the endmost fins of that tank, as shown particularly in Fig. 3. Those blocks keep air from passing upwardly between the sides 12 of the heating device 10 and the ends of tank 46, and also keep those sides from getting too hot. "The bottom of the tank 46 is flat, and it rests upon and is supported by the tubular sleeves 44 which are telescoped over the rods 42. The lower ends of the fins 48 are tapered; those lower ends tapering from the full depth of those fins to zero. This means that the lower ends of the fins lie in the planes of the front and rear faces of the tank 46. The tapering provides generally triangular, prismatic air spaces, as indicated particularly in Fig. 1, at the front and rear portions of the bottom of the tank 46.

The numeral denotes the cover for the open upper end of the tank 46. That cover is generally fiat, but it has two bosses 49 depending downwardly from the under face thereof adjacent the opposite ends thereof. In addition, that cover has a boss 53 depending downwardly from the under face thereof adjacent the longitudinal center thereof, and it has a boss 57 extending downwardly from the under face thereof adjacent the midpoint of the portion thereof between the boss 53 and the right-hand boss 49 in Fig. 5. The bosses 49 have large, vertically directed openings through them, and those openings accominoldatej sleeves, not showrno-f insulating material such'as fibref' The bosses 53 and 57 also have vertically directed openings through them, but those openings are not provided with insulating sleeves. Further openings are provided in the cover 50, and those openings accommodate machine screws 51 which releasably secure the cover to the top of the tank 46.

Threaded rods 52 telescope through the insulating sleeves in the bosses 49 and through the opening in the boss 53. A series of insulating washers 54, such as mica washers, are telescoped over the lower ends of the threaded rods 52 which extend through the insulating sleeves in the bushings 49, and those washers are pressed upwardly against the bottoms of the bushings 49. Thereafter, metal washers 56 are telescoped over the lower ends of the rods 52 that extend through the insulating sleeves in the bushings 49, and nuts 58 are threaded onto those rods and rotated until they abut the metal washers 56. Washers of insulating material such as mica are telescoped downwardly over the tops of the threaded rods 52 which extend through the insulating sleeves in the bosses 49,.and metal washers 56 are also telescoped over the tops of those threaded rods. Nuts 58 are then threaded onto the upper ends of the rods 52 which extend through the insulating slaves in the bosses 49, and those nuts are tightened down onto the washers 56. The nuts 58 above and below the level of the cover 50 mechanically lock the two end rods 52 to that cover 50 while the insulating sleeves, not shown, and the insulating washers 54 and 55 electrically isolate those end rods from that cover.

The center rod 52 telescopes through the opening in the bushing 53 on cover 50; and metal washers 56 are telescoped over the opposite ends of that rod and moved into position adjacent the upper surface of cover 50 and adjacent the bottom surface of boss 53. Nuts 58 are threaded onto the opposite ends of the center rod 52, and those nuts bear against the washers 56. The nuts 56 mechanically and electrically connect the center rod 52 to the cover 50. Nuts 59 are telescoped downwardly over the tops of each of the rods 52, and those nuts can be used to secure the electrical leads to those rods.

The numerals 60 and 62 denote washers and nuts which are telescoped over the lower ends of each of the rods 52. Those washers and nuts are grouped in pairs and are arranged so each pair of nuts 62 has two washers 60 between them. Those washers and nuts fixedly clamp the ends of electrically-operated heating elements 64 and 66 to the rods 52. The heating elements 64 and 66 are helically wound resistance wires of corrosion-resistance metal, such as Nichrome. As indicated particularly in Fig. 5, three heating elements 64 extend between the left-hand and the center rods 52, and three heating elements 66 extend between the center and the right-hand rods 52. Those heating elements are located in the lower part of the tank 46, and this is desirable because it fully utilizes the thermosiphon capabilities of the liquid dielectric.

The center rod 52 is longer than either of the end rods 52. That center rod extends downwardly to a point closely adjacent the bottom of the tank 46 whereas each of those end rods has its lower end disposed an appreciable distance above the bottom of that tank. This dimensioning of the rods 52 assures the desired inclination of the electrical heating elements 64 and 66 upwardly and away from the longitudinal center of the tank 46.

That inclination is desirable because the air which must pass longitudinally of the tank before it enters the spaces between the fins adjacent the ends of the tank, will rise upwardly as it moves longitudinally of the tank; and that air would by-pass part of the lowermost heating elements 64 and 66 if those heating elements were not inclined. The inclinations of the heating elements 64' and 66 closely approximate the upwardly and outwardly inclined paths that the air, moving toward the endmost fins 48 on tank 46, will follow. The inclining of the heating elements 64 and 66 also helps minimize sagging other end rod 52. The lead ofth'os'e heating elements when they get hot. The tapering of the bottom ends of the fins 48 facilitates this outward and upward movement of the air, and thus makes sure a proportionate amount of air will pass to the fins adjacent the ends of the tank 46 even though the outlet opening of the blower 30 is shorter than the tank 46.

A thin walled tube 68 has its lower end fixedly secured, in a manner well known to those skilled in the art, within the opening through the boss 57 of cover 50. That tube can be readily flexed and bent, and it will extend outwardly through an opening in the hot air duct 24 and also extend outwardly through an opening in the wall of the house or other building in which the heating device is installed. The outermost end of the tube 68 can be bent downwardly to keep out rain, snow and the like. This tube serves as a vent, and it will permit any vaporized dielectric 79 to move outwardly out of the tank 46. T hat vaporized dielectric will pass outwardly through the vent 68 until it cools and condenses, and thereafter that dielectric will drain back into the tank 46. To facilitate that draining, the tube 68 should incline downwardly toward the cover 50.

The dielectric 79 should be liquid, should be stable when heated and should be a good heat exchanging medium; One such dielectric is a fluid manufactured and sold by the Monsanto Chemical Company as Aroclor 1248. The dielectric 79 should substantially fill the tank 46, but one or more inches of air space should be left at the top of that tank. That air space permits the dielectric 79 to expand without entering the tube 68.

As indicated particularly in Fig. 6, a lead 70 is connected to one of the end rods 52, a lead 72 is connected to 'the center rod 52, and a lead 74 is connected to the 72 is directly connected to the neutral lead of a 220 volt supply of 60 cycle alternating current; and the leads 70 and 72 are connected to the hot leads of that 220 volt supply of 60 cycle alternating current through the contacts 88 and 90 of an electromagnetic relay. That relay has a coil 86 which causes the contacts 88 and 90 to close whenever it is energized. In the particular'modification shown, the relay is designed to carry 30 amperes. The leads 70, 72 and are made long, and they are made flexible; and this makes it possible to move the tank 46 endwise a distance equal to the length of that tank without disconnecting those leads. S'uch endwise movement is facilitated by the rotatability of the sleeves 44 relative to the rods 42; and that endwise movement makes it possible to shift the tank 46 far enough to remove the nuts 59 and the leads 70, 72 and 74 from the rods 52. Thi's ineans that if a suitable support is set at the level of the sleeves 44, the tank 46 can be shifted onto that support, the nuts59' and the leads 70, 7 2 and 74 can be freed, the screws 51 can be removed, and then the cover 50 with its rods-'52 and its heating elements 64 and 66 can be removed without emptying the tank 46.

A housing 82 is provided at the front of the heating device 10 of Figs. l3, and that housing issecured to the front wall 14 of that heatingdevice. That housing contains two thermostats 78 and 30; and while a number of different thermostats could be provided, the dual control device of the White-Rodgers Company is quite use ful. That dual control device has two liquid-filled probes, and the probe for the thermostat 78 will be mounted in the air stream that issues from the upper ends of the fins 48 on tank '46, and the probe for the thermostat 89 will rest upon the upper ends of those fins. As a result, the probe for the thermostat 78 will be responsive to the heat in the air passing upwardly from the fins 48 of tank 46 while the probe for the thermostat 80 will be responsive to the heat in those fins.

As indicated particularly in Fig. 6, the thermostat. 78 is: connected in series with a manually operated switch 92 and with the blower motor 36; and that thermostat switch and motor are connected to a 110 volt supply of 60 cycle alternating current. The thermostat 78 is designed so it is normally open and so it will close only when the temperature of the air rising from the tank 46 is above a predetermined value. This means, that the blower motor 36 will not start until the air rising upwardly from the fins 48, due to thermosiphon effect, is hot enough to cause the thermostat 78 to close the circuit of the fan motor 36. This is desirable because it keeps the blower motor 36 from blowing cool air through the hot air system and thus chilling the occupants of the house or other building.

The thermostat is connected in series with the coil 86 of the electromagnetic relay, with the room thermostat 84, and with manual switch 92; and those thermostats, that coil and that switch are connected to the said 110 volt supply of 60 cycle alternating current. The thermostat 80 is normally closed, and it will open only in the event some abnormal condition arises and causes the temperature of the tank 46 to rise above a predetermined value. For example, if the belt 40 were to break or to free itself from the sheaves of motor 36 or blower 30, the heat generated by the heating elements 64 and 66 would not be dissipated by a rapidly moving volume of air, and the temperature of the dielectric 79 would rise unduly. At such time, the thermostat 80 would open and prevent further operation of the heating elements 64 and 66 until the temperature of the dielectric 79 fell below the said predetermined value.

The manually operated switch 92 will be connected in the hot side of the 110 volt supply of 60 cycle alternating current. That switch is shown as being mounted on the front wall 14 of the heating device 10, and it is shown as being mounted below the housing 82.

In operation, the householder or the maintenance man for the building closes the switch 92. Thereupon, if the room thermostat 84 calls for heat, current will flow past switch 92, through thermostat 80, through thermostat 84, and through the electromagnetic coil 86 to the other side of line. The resulting flow of current through the coil 86 will cause the contacts 88 and 98 to close; and thereupon current will flow from each of the hot leads to the end rods 52 and thence through the electrically-operated heating elements 64 and 66 to the neutral lead 72. The heat generated by the heating elements 64 and 66 will be transferred to the walls and fins 48 of the tank 46, and that heat will be transferred to the air confined by that tank, those fins and partitions 26 and 28. That air will rise, and as it does so it will heat the probe of thermostat 78; and very quickly that thermostat will close and energize the motor 36. The resulting flow of air will provide an adequate volume of heated air for the hot air heating system of the house or other building.

The heated air will eventually raise the temperature of thermostat 84 to the desired level; and thereupon, the coil 86 of the electromagnet relay will be de-energized.

he contacts 88 and 90 will then re-open and the heating elements 64- and 66 will be disconnected from the 220 volt supply of 60 cycle alternating current. The fins 48 will be quickly cooled by the air moved over them, and the temperature of the air adjacent the probe of the thermostat 78 will quickly fall to a level where that thermostat will re-open and de-energize the blower motor 36. The electrically-operated heating device 10 provided by the present invention is compact and highly efficient, and it provides close control of the temperature in the house or other building being heated.

in one preferred embodiment of the present invention, each of the six heating elements had a rating of one thousand watts, and the thermostat 80 was set to remain closed until the tank temperature reached four hundred and fifty degrees Fahrenheit. The blower 30 caused air to pass through the heating device 10 at the rate of about eight hundred cubic feet per minute under those conditions, the temperature of the air entering the hot air duct 24 was about three hundred and forty five degrees Fahrenheit.

Whereas the drawing and accompanying description have shown and described a preferred embodiment of the present invention it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof.

What I claim is:

1. An electrically-operated heating device that comprises a tank with generally vertically-directed fins at the exterior thereof, said fins being non-linear to define zigzag paths therebetween, partitions that are adjacent said fins and that coact with said fins and with said tank to define confined passages of zigzag configuration for air, a blower to move air through said passages, a plurality of electrically-operated heating elements that are disposed within said tank, a liquid dielectric that is within said tank and that immerses said electrically-operated heating elements, the outlet of said blower being shorter than said tank, and baflies extending from the outlet of the blower to points adjacent the ends of said tank, said fins having those ends thereof which are adjacent said blower outlet tapered, said ends of said fins tapering from substantially no width at a point adjacent the outlet of said blower to full width at a point spaced further from said outlet of said blower, the tapering of said fins permitting part of the air from said outlet of said blower to work its way toward the ends of said tank and to enter the zigzag passages defined by the fins adjacent said ends of said tank.

2. An eleetricallyoperated heating device that comprises a tank with generally vertically-directed fins at the exterior thereof, partitions that are adjacent said fins and that coact with said fins and with said tank to define confined passages for air, a blower to move air through said passages, a plurality of electrically-operated heating elements that are disposed within said tank, the outlet of said blower being shorter than said tank, and bafiies extending from the outlet of the blower to points adjacent the ends of said tank, said fins having those ends thereof which are adjacent said blower outlet tapered, said ends of said fins tapering from substantially no width at a point adjacent the outlet of said blower to full width at a point spaced further from said outlet of said blower, the tapering of said fins permitting part of the air from said outlet of said blower to work its way toward the ends of said tank and to enter the passages defined by the fins adjacent said ends of said tank.

3. An electrically-operated heating device that comprises a tank with generally vertically-directed fins at the exterior thereof, partitions that are adjacent said fins and that coact with said fins and with said tank to define confined passages for air, a blower to move air through said passages, a plurality of electrically-operated heating elements that are disposed within said tank, the outlet of said blower being shorter than said tank, and baffles extending from the outlet of'the blower to points adjacent the ends of said tank, said fins having those ends thereof which are adjacent said blower outlet formed to define elongated passages for air so part of the air from said outlet for said blower can move longitudinally of said tank before entering said passages.

4. An electrically-operated heating device that comprises a liquid-tight tank with generally vertically-directed fins at the exterior thereof, said fins being non-linear to define zigzag paths therebetween, partitions that are adjacent said fins and that coact with said fins and with said tank to define confined passages of zigzag configuration for air, a blower to move air through said zigzag passages, a plurality of electrically-operated heating elements that are disposed within said tank, a liquid dielectric that is within said tank and that immerses said electrically-operated heating elements, and a vent that extends upwardly from the upper area of said tank to a cooler area, said vent conducting any vaporized dielectric from the upper areas of said tank to said cooler area, the portion of said vent intermediate said tank and said cooler area being directed downwardly toward said tank so condensed dielectric can return to said tank in response to gravitational force.

5. An electrically-operated heating device that comprises a liquid-tight tank, a plurality of electrically-operated heating elements that are disposed within said tank, a liquid dielectric that is within said tank that immerses said electrically-operated heating elements, and a vent that extends from the upper area of said tank to a cooler area spaced from said tank, said vent being open to the atmosphere and being directed downwardly from said cooler area to said tank so any dielectric that vaporizes in said tank and passes through said vent to said cooler area will condense in the vent and then drain back to said tank under gravitational action.

6. An electrically-operated heating device that comprises a liquid-tight tank with generally vertically-directed fins at the exterior thereof, said fins being non-linear to define zigzag paths therebetween, partitions that are adjacent said fins and that coact with said fins and with said tank to define confined passages of zigzag configuration for air, a blower to move air through said passages, a plurality of electrically-operated heating elements that are disposed within said tank, and a liquid dielectric that is within said tank and that immerses said electricallyoperated heating elements, said electrically-operated heating elements being inclined relative to the bottom of said tank whereby those portions of said heating elements which are closest to the outlet of said blower are closer to the bottom of said tank than are those portions of said heating elements which are remote from said outlet of said blower.

7. An electrically-operated heating device that comprises a liquid-tight tank with generally vertically-directed fins at the exterior thereof, partitions that are adjacent said fins and that coact with said fins and with said tank to define passages for air, a blower to move air through said passages, a plurality of electrically-operated heating elements that are disposed within said tank, and a liquid dielectric that is within said tank and that immerses said electrically-operated heating elements, said electrically-operated heating elements having those portions thereof which are adjacent the ends of said tank disposed at greater distances, both laterally and longitudinally, from said outlet of said blower than are those portions of said electrically-operated heating elements which are in register with said outlet of said blower.

8. An electrically-operated heating device that comprises a liquid-tight tank with generally vertically-directed fins at the exterior thereof, partitions that are adjacent said fins and that coact with said fins and with said tank to define passages for air, a blower to move air through said passages, a plurality of electrically-operated heating elements that are disposed within said tank, and a liquid dielectric that is within said tank and that immerses said electrically-operated heating elements, said electricallyoperated heating elements having those portions thereof which are adjacent the ends of said tank disposed at greater distances, both laterally and longitudinally, from said outlet of said blower than are those portions of said electrically-operated heating elements which are in register with said outlet of said blower, said electricallyoperated heating elements being stacked in vertical array, said outlet for said blower being adjacent the longitudinal center of said tank.

9. An electrically-operated heating device that comprises a liquid-tight tank, electrically-operated heating elements that are disposed within said tank, a liquid dielectric that is within said tank and that immersessaid electrically-operated heating elements, stationary supports below said tank, elements that are rotatably mounted on said supports and that engage and hold said tank, said 9 rotatable elements permitting said. tank to be translated into and out of position within said electrically-operated heating device, and elongated leads that permit said tank to be translated relative to said rotatable elements until said tank is. substantially out of said electricallypperated heating device.

10. An electrically-operated heating device that comprises a liquid-tight tank, electrically-operated heating elements that are disposed within said tank, a liquid dielectric that is within said tank and that immerses said heating elements, stationary supports below said tank, elements rotatably mounted on said supports to engage and hold said tank, said rotatable elements permitting said tank to be translated into and'out of position within said electrically-operated heating device, and elongated leads that permit said tank to be translated relative to said rotatable elements until said tank is substantially out of said electrically-operated heating device, said rotatable elements being sleeves that telescope over said stationary supports, said stationary supports being elongated rods.

11. An electrically-operated heating device that comprises a liquid-tight tank, said tank having a large, hollow central area, a cover for said tank, electrodes carried by and extending downwardly form said cover into said large, hollow central area of said tank, and electrically-operatecl heating elements extending between and carried by said electrodes, said cover being removable from said tank and providing the sole support for said electrodes and for said electrically-operated heating elements whereby removal of said cover effects simultaneous removal of said electrodes and of said electrically-operated heating elements.

12. An electrically-operated heating device that comprises a liquid-tight tank, a plurality of electrically-operated heating elements disposed within said tank, and a liquid dielectric that is within said tank and that immerses said electrically-operated heating elements, said electrically-operated heating elements being substantially unsupported intermediate their ends and being disposed one above the other in vertical array, said electrically-operated heating elements being inclined to the horizontal to minimize sagging as they become heated.

13. An electrically-operated heating device that comprises a liquid-tight tank with generally vertically-directed fins at the exterior thereof, said fins being nonlinear to define zigzag paths therebetween, partitions that are adjacent said fins and that coact with said fins and with said tank to define confined passages of zigzag configuration tor air, a blower to move air through said 10 passages, a plurality of electrically-operated heating elements that are disposed within said tank, and a liquid dielectric that is within said tank and that immerses said electrically-operated heating elements, said electricallyoperated heating elements being stacked in vertical array in the lower portion of said tank.

14. An electrically-operated heating device that comprises a liquid-tight tank with generally vertically-directed fins at the exterior thereof, said fins being nonlinear to define zigzag paths therebetween, partitions that are adjacent said fins and that coact with said fins and with said tank to define confined passages of zigzag configuration for air, a blower to move air through said zigzag passages, a plurality of electrically-operated heating elements that are disposed within said tank, and a liquid dielectric that is within said tank and that immerses said electrically-operated heating elements, the upper surface of said liquid dielectric being disposed below the level of the top of said tank to provide a space into which said liquid dielectric can expand during the operation of said electrically-operated heating device.

15. An electrically-operated heating device that comprises a tank with generally vertically-directed fins at the exterior thereof, partitions that are adjacent said fins and that coact with said fins and with said tank to define confined passages for air, a blower to move air through said passages, a plurality of electrically-operated heating elements that are disposed within said tank, the outlet of said blower being shorter than said tank, and bafiles extending from the outlet of the blower to points adjacent the ends of said tank, said fins having those ends thereof which are adjacent said blower outlet formed to define elongated passages for air so part of the air from said outlet for said blower can move longitudinally of said tank before entering said passages, said electricallyoperated heating elements being inclined so they approximate the upward and outward movement of the said part of the air that passes longitudinally of said tank before entering said passages.

References Cited in the file of this patent UNITED STATES PATENTS 1,555,268 Colby Sept. 29, 1925 1,706,879 Gullborg et al Mar. 26, 1929 2,104,848 Clark Jan. 11, 1938 2,203,425 Welch June 4, 1940 2,464,703 Marshall Mar. 15, 1949 2,481,963 Witte et al. Sept. 13, 1949 2,502,551 Appell Apr. 4, 1950

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