US2984728A - Radiant heater - Google Patents

Description

M. K. MURPHY RADIANT HEATER May 16, 1961 4 Sheets-Sheet 1 Filed May 21, 1958 M. K. MURPHY RADIANT HEATER May 16, 1961 4 Sheets-Sheet 2 Filed May 21, 1958 M. K. MURPHY RADIANT' HEATER May 16, 196 1 4 Sheets-Sheet 3 Filed May 2]., 1958 Fm F |I. 4 w A Q .l.@

May 16, 1961 Filed May 21', 1958 M. K. MURPHY RADIANT HEATER 4 Sheets-Sheet 4 United States Patent RADIANT HEATER Maxwell K. Murphy, 535 W. Goldengate, Detroit 3, Mich.

Filed May 21, 1958, Ser. No. 736,871

1 Claim. (Cl. 219-20) This invention relates to radiant space heaters and particularly to heating panels intended primarily for wall or ceiling mounting. More particularly, the invention concerns electrically energized space heaters designed to emit a major portion of their output in the form of radiant heat and a lesser portion as convection heat.

My heating panel utilizes a flat, sheet-like heating element, preferably of glass or metal coated with ceramic material with an electric resistance element fused or embedded therein, but any other type of heating element of sheet form may be used.

In my improved panel assembly, the major frame elements are adapted to be made of extruded or rolled sections. Heretofore, most of the heating panels of this general type have been made up of metal parts formed by stamping or by bending on a press-brake. By utilizing extruded or rolled sections, I am able to manufacture various sizes of panels with minimum tooling expense and the necessity for stamping presses of large capacity is avoided. In addition, my improved panel is less costly to produce than those now in use, and it has a better appearance.

Radiant heaters of the type herein described are very efiicient in their transformation of electrical energy into heat rays and provide an extremely pleasant and comfortable source of heat. They are used primarily as zone heaters and to achieve economy are usually turned off (or the thermostat control adjusted to provide a temperature lower than comfort demands) when the heated space is not in use.

Because the heating element used will not emit the infra-red heat rays to any appreciable extent until it itself is hot, there is some delay in response after the heater has been turned on, or the thermostat turned up, which has led to complaints from users.

I propose to overcome this defect, if it is in fact a defect, by means about to be described.

The principal object of my invention is to provide a combined radiant and convection heating device with means for circulating convection heat currents for quick warm-up of the room or space tobe heated, even though the radiant heating effect is utilized most of the time.

A further object is to provide means in connection with an electrical radiant heating panel for obtaining fast warm-up of the panel by subjecting the panel to a greater than normal voltage and removing heat from the panel quickly during the warm-up period such that the panel is not damaged by the overload.

Another object is to provide an improved electrically energized heating panel wherein the sheet-heating element is firmly yet yieldably supported such that normal expansion and contraction is freely permitted without rattle of the element.

Still another object is to provide in such a panel, improved means for supporting the heating element subassembly such that it is easily and readily assembled during initial installation and easily removable for servicing or replacement purposes.

2,984,728 Patented May 16, 1 961 Other objects and advantages of my invention will become apparent from the following specification which, taken in conjunction with the accompanying drawings, discloses preferred forms thereof.

In the drawings:

Fig. 1 is a front elevation of my improved panel as it would appear when mounted on a wall;

Fig. 2 is a fragmentary sectional detail, in perspective and on an enlarged scale of the Fig. 1 panel;

Fig. 3 is an enlarged section taken along the line 3-3 of Fig. 1;

Fig. 4 is a front elevation of a modified form of panel;

Fig. 5 is an end view, on a reduced scale, 4 panel;

Fig. 6 is an enlarged section taken along line 6-6 of Fig. 4;

Fig. 7 is an enlarged section taken along line 7-7 of Fig. 5;

Figs. 8 and 9 are sections, lines 88 and 9-9 of Fig. larged scale;

Fig. 10 is a sectional view taken along the line 10-10 of Fig. 4;

Fig. 11 is a View similar to Fig. 10, but of a modified form of panel; and

Fig. 12. is a schematic wiring diagram of a control circuit for the panels which incorporate a fan for circulating forced convection heating currents.

Referring now to Figs. 1-3 inclusive, it may be seen that the panel assembly 10 comprises an outer or base frame 12 in which is disposed an inner or sub-frame 14, the latter forming part of a sub-assembly disposed in spaced relation with respect to the main frame as will subsequently appear.

The main frame 12 is rectangular as may be seen from Fig. 1. The proportions of the rectangle may be chosen as desired depending on the use to which the panel is to be put. So called baseboard units are generally relatively long in proportion to depth; wall units are usually about one and one-half times as long as the depth thereof, and small wattage units, for bathrooms and the like, may be square or nearly so. The frame 12 is fabricated from a section 16 (Fig. 2) of metal, preferably aluminum. The section may be of extruded stock or it may be formed by a rolling operation. In either case, it is desirable to provide a grooved or other design for decorative purposes, and an integral flange 18 is provided at the rear edge to which the back-Wall or back panel 20 is attached by welding, riveting or by set screws (not shown).

The back panel is provided with openings for screws 22 by means of which the entire panel assembly may be attached to a wall 24. The back panel 20 is of sheet metal and is preferably left unfinished or suitably treated to provide some heat-reflecting quality.

The frame 12 is made by mitering the corners of the section 16 and bending into a rectangle, the joint between the abutting ends being welded and ground to provide a good appearance. Attachment of the back panel to the flange 18 thus results in a pan-shaped base for the assembly.

The sub-frame 14 is made in a similar manner from extruded or rolled stock 26 (Fig. 2). This frame is also rectangular, but smaller than the main frame and has a rearwardly extending flange 28 to which is attached a reflector panel 3b; The panel 30 forms a back panel for the sub-frame and is attached by means of a plurality of channel shaped clamps 32, which clamps have one side wall welded to the reflector panel 30, and the web thereof is fastened by a screw 34 to the flange 28. As many clamps 32 may be used as deemed necessary to provide of the Fig.

taken respectively along the 4, Fig. 8 being on an enrigid support for the reflector panel and for the heating element 36.

The heating element 36 is supported along its periphery by the flange 28. The forward side walls of the clamps 32 engage the rear marginal edge of the element at several points in accordance with the locations of the clamps and thereby prevent displacement of the element. A yieldable pad 38 is provided at these points to cushion the element and assure firm support thereof. The pad 38 is preferably of yieldable silicone material which has heatresistant and electrical-insulating properties and is of sufficient thickness such that it is slightly compressed between the heating element 36, the frame element 26 and the side wall of clamp 32. This mounting for the heating element provides a tight, non-rattle support at all times when in use and during transportation prior to installation, yet permits normal expansion and contraction of the element during heating and cooling.

The element 36 may be of glass with an electrical resistor fused to the rear surface thereof, as shown in Lamb Patent No. 2,536,648, or it may be a metal sheet covered with vitreous material on both surfaces with a metallic resistor fused on the rear vitreous surface. For convenience, the element 36 has been shown of glass, and while either type of element may be used, my overload protection device about to be described is most useful with the glass elements which are more susceptible to failure due to overload.

Interposed between the sub-frame 14 which comprises the parts 26, 30, 32 and 36, and the main frame 12 which comprises the parts 16 and 20, is a pair of channel members 40. These channel members are disposed in spaced, vertical, rearwardly presenting relation and have their web portions welded or otherwise secured to the back of the reflector panel 30. The side-wall portions of the channels constitute spacing means for spacing the subframe assembly from the back panel and for securing the two frame assemblies together.

The flange 18 of the main frame member 16 is provided with threaded holes for receiving screws 42 which pass through suitable holes in the channels 40 near the tops and bottoms thereof. The holes for the screws 42 are located such that the screws can be inserted and withdrawn through the clearance between the frames 12 and 14 as may be seen in Figs. 1 and 2.

The electrical connections to the resistor in the heating plate 36 are preferably brought to a junction box 44 carried by the back panel 20 in a manner similar to that shown in Fig. 9 of the modification.

When installing the heating panel, the screws 42 are removed to permit removal of the sub-frame 14 and its associated parts from the main frame 12. The main frame assembly is then fastened to the building wall 24 by screws 22, and the electrical conduit is brought into the junction box 44. The connections between the junction box and the heating resistor are then completed and the sub-frame is inserted into the main frame and secured in place by the screws 42. The connections between the heater plate and the junction box are not shown but are preferably of flexible wires which permit the connections to be made with the frame 14 lying on a suitable support outside the frame 12. The heater is then ready for use.

Energization of the plate 36, preferably under thermostatic control, will cause emission of infra-red heat rays from the front surface of the plate thereby providing true radiant heat. Heat rays emitted from the rear surface of the plate 36 will be reflected back into the plate by the reflector panel 30 and as the latter becomes heated, the back panel 20 will reflect heat rays thereby providing a highly eflicient radiant heater.

It will be noted that the sub-frame assembly is spaced from the main frame at the back, sides, top and bottom thereby permitting free air circulation between the reflector panel 30 and the back panel 20. Similarly, the reflector panel 30 is spaced from the heating plate 36 by the clamp 32 and free air circulation is permitted at the top, bottom and sides of the reflector plate between it and the heating plate. Thus convection air currents are permitted to flow freely between the heating plate 36 and the reflector panel 30 and between the panel 30 and the back panel 26. These currents of warm air enter the slot between the frames 12 and 14 at the bottom and pass out through the slot at the top thereby circulating around the heated space and increasing the overall efficiency of the heating unit while keeping temperatures within the unit from reaching excessive values.

The outer edge of the frame member 16 of frame 12 deflects the rising air currents such that they do not contact the wall immediately above the heating panel and cause dust streaks. For this reason, it is desirable that the outer edge of frame 12 extend substantially outwardly of the outer edge of frame 14, particularly along the top portions thereof. In some instances, it may be desirable to make the top portion of frame 12 of a separate section of stock of greater width than the bottom and sides to provide increased projection of air currents in an outward direction.

In the modified form of heater shown in Figs. 4-10 in clusive, the main base frame 50 is made of extruded or rolled stock and may be hollow, as shown, or it may be of solid section. The sub-frame 52 is also of extruded or rolled stock, either hollow, as shown, or solid. The two frames are fabricated by notching and forming as explained above in connection with the other form of panel.

The main frame 50 is formed with a shoulder 54 to which a back-wall or back panel 56 is fastened by a plurality of rivets 56. Holes are provided in the panel 56 for wood screws 60 which may be used to secure the whole assembly to a wall.

The sub-frame assembly comprises the sub-frame 52, the heating plate 62 and the reflector panel 64. The latter has a plurality of clamps 66 welded thereto, which clamps have a front flange which bears against yieldable channel members 68 in which the heating element 62 is received. The clamps force the members 68 forwardly against the rear face of the frame 52 thus retaining the heating plate in assembled relation. A plurality of bolt and nut assemblies '70 are used to fasten the clamps 66 to the sub-frame 52.

The two frames 50 and 52 are detachably secured together by means of screws 72. It will be noted that the respective frames fit closely together at the sides, but at top and bottom a sizeable slot is provided for circulation of convection air currents which carry off the heat from the spaces between the plate 62 and reflector panel 64 and between the latter and the back panel 56. If desired, the back panel 56 may be provided with louvres for allowing escape of hot air that may be trapped between the wall and the back panel. The reflector panel 64 is preferably polished on its front surface to reflect heat and the back panel 56 may be similarly treated if desired.

A junction box 74 is carried on the back panel 56 for accommodating the power connections to the heating plate 62.

As will be seen from Fig. 10, the back panel 56 has a depressed box-like section 76 disposed centrally thereof, which provides a mounting and housing for a fan motor 78. The motor has a fan blade 80 mounted on its drive shaft. The reflector 64 is provided with an opening 82 for accommodating the blade 80 as shown.

As above stated, in the normal operation of the panel assembly as a radiant heater, most of the heat generated is radiated directly from the front surface of element 62, aided by the reflector 64, with a small amount of heat being circulated by convection air currents passing in through the slot at the bottom and out through the slot at the top of the sub-panel assembly.

The convection air circulation can be greatly increased by the provision of blower means such as the fan 80. If desired for better eficiency, a sirocco type of air impeller may be used instead of the blade type shown. Operation of the blade 80 by the motor 78 will cause relatively rapid air circulation in the space between the reflector 80 and element 62 and in the space between the reflector 64 and back panel 56 and will result in the heat emitted from the rear surface of the element 62 being carried off at a rate suflicient to lower the temperature of the element rapidly and decrease its radiant emission. Because the heater is primarily a radiant heater, such rapid removal of heat from the back-space is not particularly desirable under normal circumstances. However, by reference to Fig. 12, it may be seen that the forced circulation of air will provide an extremely useful function and increase the efliciency of the heater under proper conditions.

Heaters of the type described normally operate on conventional 115 volt or 230 volt power supply, although any voltage may be used with proper choice of the resistance of the metallic resistor. In this example, let it be assumed that the heating element 62 is designed for 115 volt normal operation and that 230 volts is available in the building.

In Fig. 12, conductors 84, 86, 88, represent the conventional 3-wire domestic supply providing 115 volts between the outside conductors and the neutral and 230 volts across the outside conductors. The heating element 62 is connected on one side to the conductor 84 and on the other side to terminals 90 and 92 respectively of switches 94 and 96. The other terminal of switch 94 is connected to conductor 88 and the other terminal of switch 96 is connected to conductor 86.

Relay coils 98 and 100 are operably associated with the respective switches and these coils are adapted to be energized by a voltage reducing transformer 102 through a thermostat 104 which is of the differential type having contacts operably responsive to two different temperatures. The motor 78 is connected to conductor 86 and to a conductor 106 which is connected to conductor 88 when switch 94 is closed.

Let it be assumed that the element of the Fig. panel has been off for a considerable period of time and that the temperature of the heated space has fallen to a point too low for comfort and the thermostat 104 is adjusted to call for a comfortable temperature, for example 72 F.

Because of its preselected diiferential action (the specific mechanism of the thermostat 104 is not shown because any commercially obtainable differential thermostat is satisfactory), the thermostat 104 will energize coil 98 only and close switch 94. Switch 96 will remain open. The element 62 will be thus connected across the 230 volt supply conductors 84 and 88, and the fan motor 78 will be connected to the conductors 86 and 88 for 115 volt operation.

Because the element 62 is constructed for maximum operating efficiency on 115 volts, imposition of 230 volts across it represents a 100% overload which will cause extremely rapid heating of the element thereby bringing it up to emission temperature quickly. However, this overload, if continued for any appreciable time and/or if the heat is not removed from the back of the sheet element rapidly, will damage the element. In the case of glass elements, the element will either burn out or the tempered glass will fail. However, because of operation of the fan 80, heat is removed from the rear surface of the sheet with suflicient rapidity to prevent the sheet from becoming hot enough to exceed its designed unit heat capacity.

The effect then is that the sheet element heats up to emission stage much quicker than normally the case and, in addition, a strong current of convection heat is circulated to provide warm-up of the heated space. The latter feature is important in that it provides a desirable physiological effect which seems to be required by some people who associate heat with a warm air current and do not feel satisfied unless this current is provided, at least during the initial stage of warming up.

The quick heating of the heated space referred to will cause the thermostat 104 to cycle off when the desired room temperature is reached. Because of the characteristic retention feature of the sheet element 62, the element will retain its heat for an appreciable period and will continue to emit heat rays and supply a slight amount of convection heat through natural air circulation.

Cooling of the element 62 will cause the room temperature to drop and when it drops to a lower value, say 69 F., the thermostat will energize coil only of switch 96. This will connect the element 62 across the conductors 84 and 86 for normal volt operation as a radiant heater, and the thermostat will cycle on and off to provide sufiicient radiant heat for comfort.

It is desirable that the thermostat be preset such that the coil 98 is not energized until the room temperature has dropped to a value 5 to 8 below that called for. In other words, ordinary operation of the panel as a radiant heater will maintain comfort with economy, but when it is desired to warm up a cold room quickly (or a severe and rapid temperature drop occurs), the quick warm-up, overload feature functions automatically to provide fast heating of the element 62 and forced circulation of convection heating air currents.

Reference is made now to Fig. 11, which shows another form of panel incorporating forced air circulation.

In this modification, a rectangular vertical metal frame 108, which is adapted to be mounted on a wall 110 has the front edge of its side wall 112 surrounded by an integral flange 114 that curves rearwardly to meet the wall. The frame also has an integral back-wall 116 which has an offset portion 118 and a box-like portion 120 for mounting and housing a fan motor 122 which drives a fan 124.

A glass heater plate 126 is disposed in the frame 108 with clearance along all edges thereof, suitable supporting means 130 being provided. The rear surface of the plate carries the usual resistor 128, and behind the plate a reflector 132 is mounted. The reflector is spaced from the plate 126 and the back wall 116 and has clearance around at least its top and bottom edges. The reflector promotes circulation of convection currents, prevents excessive heating of the back-wall and increases the radiant effect of the plate, as explained above.

A vitreous coated metal plate with attached resistor may be used in place of the glass plate if desired.

The reflector 132 is provided with a plurality of openings 134 uniformly distributed over substantially the entire area of the sheet to permit some of the heat emitted from the back of plate 126 to pass through instead of being reflected. This improves natural circulation of air and permits the plate 126 to be subjected to greater wattage input than would be the case ordinarily.

The fan 124 is disposed back of the reflector 132 instead of in the plane of the reflector, as in Fig. 10, and when in operation, further increases the passage of convection air currents. This form of panel is adapted to be controlled by the Fig. 12 control mechanism, and in a similar manner.

It is desired to point out that, in any of the forms of device disclosed, the blower means could be operated at all times that the heating element is energized. By so doing, it is possible to operate the element with much greater wattage input than is the case when only radiant heating is desired with natural convection. This permits greater wattage input to the element than would ordinarily be possible in accordance with underwriters specifications and results in much greater heat capacity for a selected size of element. It is not necessary under such conditions to have a dual voltage source, the element is simply made with a higher resistance per unit area and the device becomes a combined radiant and convection heater.

It will thus be seen that I have shown and described several forms of radiant heating panels which are easy and economical to manufacture, which have a more pleasing appearance than those now in use, and which provide advantages not present in conventional panels.

I claim:

In combination, a panel type electrical space heater adapted to function mainly as a radiant heater but capable of supplying heated air currents by convection as well, comprising, a sheet type heating element mounted to emit heat rays from its front surface to the heated space and in spaced relation to a supporting frame such that convection air currents may flow upwardly over both surfaces thereof, means for supplying to said element a normal operating voltage, temperature responsive means for cycling said element on and off in accordance with preselected adjustment, means operably associated with said temperature responsive means for applying to said element a voltage substantially in excess of normal voltage to provide quick warmup of said element, said excess voltage being sufficient to damage said element unless the generated heat is removed from said element by forced air circulation, blower means for providing increased convection air flow over said element, and means for causing operation of said blower means whenever said element is subjected to excess voltage.

References Cited in the file of this patent UNITED STATES PATENTS 997,465 Mies et al. July 11, 1911 2,065,895 Jandat Dec. 29, 1936 2,075,463 Parsons Mar. 30, 1937 2,260,840 Rowe Oct. 28, 1941 2,433,137 Man- Dec. 23, 1947 2,445,250 Steingruber July 13, 1948 2,536,648 Lamb Jan. 2, 1951 2,698,893 Ballard Jan. 4, 1955 2,707,745 Farr et al. May 3, 1955 2,770,704 Razlag Nov. 13, 1956 2,781,440 Petersen et a1 Feb. 12, 1957 2,822,456 Glynn Feb. 4, 1958 2,867,710 Glynn Jan. 6, 1959

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