US2815431A - Convection heating unit - Google Patents

Description

Dec. 3, 1957 A. A. PALEY CONVECTION HEATINQ UNIT 2 Sheets-Sheet 2 Filed Feb. 15, 1954 INVENToR.

,4x 55er A nur United States Patent CGNVECTIDN HEATING UNIT Albert A. Paley, Kew Gardens, N. Y.

Application February 15, 1954, Serial No. 410,080

1 Claim. (Cl. 219-34) This invention relates to an improved convection heating unit and has for an object the provision of a device in which the entire cabinet on all sides is fully enclosed, with the exception of louvre openings, whereby one cannot contact the electrical parts of the heating unit, which is very hot, with the ngers inadvertantly.

Another object is to provide a cabinet of such unique construction that the walls of it, such as the outer top, side and rear walls are maintained at a safe temperature, and at one relatively low compared to that to which the inner heated air achieves. This construction permits the outer walls to be safe to touch and, when the cabinet is placed in a wall niche, the loss of heat to the walls is negligible.

Another object is to provide a cabinet which is simple in construction, which can be made eiciently at relatively low cost, and lends itself to mass production methods in manufacture, can be readily accessible to permit adjustment and/or repairs.

A further object is to provide a cabinet in which the stack is a maximum possible; the device is formed of an outer and an inner chamber so that the inner chamber forms a complete heat chimney and in which the space between the two chambers forms a passage for relatively cool air from the room to enter at the bottom and exit at the top to keep the adjacent walls of the inner chamber from over-heating.

A still further object is to provide a thermostatic element within the device but shielded from the heat chimney which will be affected by the room temperature to more accurately gauge the same and control its desired variation.

Further and more specific objects, features, and advantages will more clearly appear from a consideration of the specification hereinafter set forth especially when taken in connection with the accompanying drawings which illustrate the preferred form of the invention and form part of the specification.

In the construction of convection heaters, their eciency is dependent upon the stack height within a given height and size of cabinet. The positioning of the heating element is limited because a too close proximity thereof to the bottom of the heater would overheat the bottom, making it unsafe and a definite lire hazard.

There has been developed therefore, a heat shield and baffle unit combined in one, which by its suspension within the outer walls of the device, deflect the heat rays since this internal heat and bafe shield forms a complete chimney by engaging with and extending from the lower part of the intake louvres, and then extending to the top of the outlet louvres, Air enters thro-ugh the lower louvres, contacts the fins on the heating element and then leaves in a heated state through the upper louvres. Since the heat shield also has taken on a higher temperature, this heat can not be cumulative since a secondary chimney or passage has been created between the inner chamber or chimney and the outer chamber. Room air enters at the lower opening below the lower fice louvres, and passes up through the chimney between the two chambers and then out at the top above the upper' louvres. The created space at the bottom of the device between the heat shield and the bottom will house a thermostat bulb to be affected by air at room temperature flowing in along the floor through the lower opening, to give a true reading unaffected by heat rays.

In electric heaters of the baseboard type where the intake and outlet circulation parts are relatively low and as a rolled-up rug or draperies could block these ports, these baseboard heaters can become a fire hazard even with an electric thermostat since, conceivably the thermostat may get out of order. Thus, with all circulation cut off or even partially so, the heater will become hotter and hotter unless the electric current is interrupted and stays so. We have therefore, provided within the heater chimney a thermostatic fusible link, which by its predetermined melting point interrupts the current flow should the temperature rise above a set limit. Thus the unit can be operated again only when the obstruction is removed7 and a new link inserted.

Another feature of the invention relates to the construction `and relation of the radiating fins and tabs mounted on the heater tube. They provide greatest possible area of contact plus stability in remaining in erect position. Tabs are concentrically formed thereby stiffening the same and have proved to have the best possible mechanical bondage during the expansion process under heat. Tabs expanded on the fins become an integral part of the tube without welding and render the unit capable of dissipating more heat effectively and evenly. This latter point is important since hot spots will lead to overloading and linal breakdown.

Another factor in securing the continued working of the element is the exclusion yof all air within the tube housing the resistor element. Both ends of the tube are hermetically sealed `and no oxidation of the resistor can take place. The coiled resistor wire is embedded in spe cial ceramic cores which in turn are embedded in a re fractory grain filling all voids and precluding the entrance of any air. A resistor held in this spaced relation can never short out to its metal sheathing and therefore it becomes a safe heating element whose metal sheathing carries no voltage and in fact is connected to the ground of the electrical circuit itself.

Heretofore heating unit casings of the convection type have been used with various heat ele-ments therein but it has been found dillicult simply and economically to so construct them as to avoid undue loss of heat to adjacent wall surfaces without the use of complicated and expensive constructions and insulating means. Since it is my purpose to provide a casing in which the outer walls adjacent the walls yof the room, in a niche in which the casing is disposed, are kept so relatively cool compared to the maximum temperature achieved by the inner air being heated, that they are safe to touch and there is only a negligible loss of heat to those adjacent walls, and therefore no danger therefrom.

In an ordinary cabinet where the temperature of the heating element is around 400 degrees F., even though you place the element a reasonable distance away from the walls, the temperature of the casing is too hot and even though you take the casing and insulate it beyond reason, the heat builds and eventually the insulation is inadequate. In order to do a real job you have to use about 4 inches of insulation which would make the cabinet impractical.

In brief and general terms the above objections are very satisfactorily solved by using a casing or cabinet formed of two chambers anjouter and an inner one with the heating element disposed within and near the bottom of the inner chambers. In the preferred form shown the casing is provided with upper and lower louvres which afford access to the inner chamber and is also provided with upper and lower openings which afford access for the air to the passage between the two chambers which passage forms a sort of chimney for cool air to enter into the bottom and pass out at the top thus dissipating heat from the walls of the inner chamber and making the absorption of the heat produced more eflicient.

It has become a custom in good design on modern buildings to recess the radiators, so that only about l of the face is shown or projects beyond the room wall. In this way, the sides, back, top and bottom are disposed within the walls of the room. In the conventional type of heating units that have no insulation of any kind, the efficiency is reduced by about 25%, because the outside walls are actually being heated. In the cabinets which have some form of insulation, whether it be asbestos, or asbestos with aluminum foil, eventually the heat in the elements builds up and then the insulation breaks down, and the efficiencies are very poor.

In the form shown herein with double walls insulated by a stream of cooling fluid passing between the spaced walls at all times, the efticiency is very high at all times because the outer wall temperature does not exceed 100 degrees F., and rear walls in particular do not become heated above 70 degrees F. In the ordinary types of cabinets the temperatures of the casing walls is practically the same as 'that of the heating elements. When electrical coils are used they achieve a temperature of about 350 degrees F. and with steam coils about 200 degrees F. and with hot water about 175 degrees F.

The underwriters laboratories have set limits to the heat of the outside of the metal casings of these cabinets, especially when they are recessed in the walls. Naturally they are not interested in efficiencies, but in combustibles, and the herein manner of keeping the outer shell cool definitely meets their limitations. Cabinets now on the market are in some cases not permitted to be placed in recesses, and others, when so placed, are required to have open spaces around the top, sides, and the back. This method is not practical, as these spaces are dirt pockets and are hard to keep clean.

This application is a continuation in part of my prior application Serial Number 272,728, filed in Division 32 on February 21, 1952, and entitled Convection Heating Unit.

The present preferred form of the invention is illustrated in the drawings, in which,

Fig. 1 is a front elevation of the device with portions broken away;

Fig. 2 is a vertical section taken on the line 2 2 of Fig. 1;

Fig. 3 is a longitudinal central section, broken away through the heating unit, showing the interior construction and the mounting of the radiating ns;

Fig. 4 is a partial similar view taken on the line 4 4 of Fig. 3;

Fig. 5 is a partial detail View of one of the n blanks before it is shaped to nal form;

Fig. 6 is a similar view with the parts in nal form; and

Fig. 7 is a section taken on the line 7-7 of Fig. 6.

Referring now merely to the particular form of the invention which has been chosen for illustration thereof, it will be noted that there are shown two chambers generally denoted A and B respectively inner and outer chambers or air chimneys, the one for heated air and the other for cooling or heat-dissipating air. The heating chimney A has connected walls such as rear wall 20, bottom wall 21, forwardly sloping top wall 22, and vertical side walls 12' and 13. The outer cooling-air chimney B has rear wall 10, top wall 11, bottom wall 12, and side walls 12 and 13. The upper edge of the sloping wall 22 of the chimney A has a horizontal ange 23. A front cover plate 24 closes the front face of the inner chamber A and has overlapping flanges 2S and 26 respectively tightly engaging the ange 23 and the lower forward portion of the bottom wall 21. This front plate has upper and lower louvres 27 and 23 therein.

The forward portion of the top wall 11 of the outer chamber B slopes forwardly and downwardly and has a reversed flange 143 disposed in spaced relation above the ange 26 of the front plate 2d thus providing an exit passage for cooling air from within the chamber B. The bottom wall 12 of the chamber E has an upturned front flange 15 which at its upper edge is spaced below the flange 25 of the front plate 24 of the chamber A to provide an entrance for room air to enter the chamber B at the bottom thereof.

The front of the chamber B at the sides is covered by vertical plates 16 and 17, to the rear of which are suitably connected strips 13 and 19 extending laterally to close relationship with the side walls 12' and 13 of the inner chamber A and of equal vertical height. The front plate 24 of the inner chamber A is connected to these strips 13 and 19 by screws 29. The front face of the chamber A is flush with the plane of the front face of the outer chamber B. The rear wall 20 of the chamber A is spaced from the rear wall 1@ of the chamber B. The bottom wall 21 of the chamber A is spaced above the bottom wall 12 of the chamber B. The top sloping wall 22 of the chamber A is spaced well below the top wall 11 of the chamber B. This spacing provides an air chimney between the two chambers since it is to be also observed that the sides 12 and 13 of the chamber A are well spaced inwardly from the sides 12 and 13 of the chamber B. Air from the room can enter at the bottom through the lower opening and extend upwardly along the sides and back of the chamber A to absorb heat therefrom and this heated air extracted from the walls of the chamber A will pass out at the top opening into `the room.

The air entering the chamber A through the bottom louvres 28 will be heated in a manner to be described and pass out at the top louvres 27 into the room. The two chambers are connected along their rear walls in spaced relation by bracket plates 3@ which may be welded to the rear wall 10 of the chamber B and connected to the chamber A by screws 31.

On the bottom wall 12 of the chamber B is disposed a bracket 38 supporting a thermostat element 39 connected by suitable wires to a control switch 41D disposed on the outside of strip 17 on the front of the device. With this switch is associated a pilot lamp 41. Suitably connected in circuit with the switch E0 and the lamp 41 is a fusible plug 37 disposed on the rear wall 2t) of the chamber A just above the heating tube 36 and suitably connected with the heating coils i6 therein. The switch 40 may be set to any temperature at which the circuit will be opened and the fusible plug 37 will break the circuit in case of dangerous overheating.

The heating tube 36 is an elongate cylinder both ends of which are hermetically sealed so that no oxidation of the within resistors can take place. The heater coils E6 are embedded in a special ceramic core i5 which in turn is embedded in a refractory grain d5 filling all voids and precluding the entrance of any air. A resistor held in this positive spaced relation can never short out to its met-al sheathing and therefore it becomes a safe heating element whose metal sheathing .3d carries no voltage and in fact this sheathing may be connected to the ground of the electrical circuit itself.

Disposed on the periphery of the tube or sheathing 36 are a plurality of heat dissipating tin plates L52 which may be circular or rectangular as desired. They are stamped out of metal and have cut-out central openings with inwardly projecting anges i3 which are then bent at right angles to the plane of the iin and are adapted to lie snugly against the outer periphery of the tube as shown in Fig. 3. The outer ends of tl ese anges are bent up slightly as at 44 to provide a spacing abutment for adjacent tins. The provision of these anges or tabs -on the tins afford the greatest possible area of contact to the tube 36, plus stability in remaining in an erect position. The ngers 43 are concentric-ally formed thereby stiftening the same and giving best possible mechanical bondage during expansion process without being welded thereto and render the unit capable of dissipating more heat more eiectively and evenly. The latter is important since hot spots will lead to overloading and nal breakdown.

The coils 46 are connected to terminal posts 48 mounted in a termianl block 47 at one end of the heating element and suitably mounted thereon and connected to the coils in any suitable manner. The heating element is suitably mounted in association with a bracket plate 32 at each end which is welded at one side to the rear Wall 20 of the chamber A. To the free side of each bracket plate 32 is connected a strap 33 having flanges 34 which are connected to the bracket 32 by means of screws 35. 'I'he heating unit is disposed longitudinal in a horizontal direction adjacent the bracket 32, nearer the rear and bottom walls of the chamber A than the top and front walls thereof. It is disposed so that cool air coming through the lower louvres 28 will pass directly across the heater and then up chamber A to be directed forwardly by the top wall thereof and out through the upper louvres 27. Since one portion of each bracket plate 32 is free and since the straps 33 are connected to these free portions any expansion of the unit due to the increasing heat developed thereon will be taken up by these free bracket portions and thus avoid any breakage of the parts.

As the air heated in chamber A passes out into the room through the upper louvres 27, the room gradually warms up. However the cooler air at the bottom of the room will by convection pass through the lower openings in the device, flow across the thermostat 39, and then pass up behind the chamber A in the chamber B and pass out through the upper opening above mentioned. Thus the relatively cooler air thus passing up through chamber or chimney B will absorb heat from the walls of chamber A to keep their temperature down and will pass as warmer air back into the room at the top of the device. Should the device become obstructed so that the flow of air through chamber B be impeded the rapidly increasing temperature will cause the fusible plug 37 to melt and cut off the power.

While the invention has been described in detail and with respect to a present preferred form thereof shown in the accompanying drawings, it is not to be limited to such detailed form, since many changes and modications may be made in the invention without departing from the spirit and scope of the invention in its broadest aspects. Hence, it is desired to cover any and all forms and modifications of the invention which may come within the language or scope of the appended claim.

What I claim as my invention is:

In a convection heating unit, comprising an outer chamber having closed top, bottom, side and rear walls, a front wall extending only part way down from the top wall and only part way up from the bottom wall, an inner chamber disposed within the outer chamber and having top, bottom, side and rear walls spaced from the respective walls of the outer chamber to form an air ue, the top wall of the inner chamber extending in a sloping direction upwardly and forwardly from the rear wall, a front wall for the inner chamber having two spaced sets of louvres at the bottom and the top thereof, the upper set of louvres being sloped downwardly and rearwardly and the lower set of louvres being sloped upwardly and rearwardly, the top and bottom edges of the front wall of the inner chamber being spaced from the adjacent edges of the front wall of the outer chamber to form elongate air passages at the top and bottom of the device for air to pass into the unit and up between the two chambers and out at the top without coming into contact with the heating element, and a horizontally disposed hermetically sealed heating element supported from the rear wall of the inner chamber and spaced therefrom to the rear of the lower set of the louvres in the front wall of the inner chamber.

References Cited in the le of this patent UNITED STATES PATENTS 1,047,418 Kercher Dec. 17, 1912 1,096,916 Hoffman May 19, 1914 1,518,067 Hicks Dec. 2, 1924 1,534,221 Kercher Apr. 2l, 1925 1,651,890 Hicks Dec. 6, 1927 1,704,479 Kercher Mar. 5, 1929 1,705,769 Kercher Mar. 19, 1929 1,828,625 Abbott Oct. 20, 1931 1,898,632 Kercher Feb. 21, 1933 1,923,083 Fisher Aug. 22, 1933 1,992,646 Young Feb. 26, 1935 2,051,930 Young Aug. 25, 1936 2,089,340 Cobb Aug. 10, 1937 2,201,024 Brown May 14, 1940 2,511,910 Foote June 20, 1950 2,538,977 Mucher Ian. 23, 1951 2,606,992 MacDonald Aug. l2, 1952 FOREIGN PATENTS 503,495 Great Britain Apr. 5, 1939 629,253 Great Britain Sept. 15, 1949

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