US2978568A

US2978568A - Electric heater

Info

Publication number: US2978568A
Application number: US771604A
Authority: US
Inventors: Maxwell K Murphy
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-11-03
Filing date: 1958-11-03
Publication date: 1961-04-04
Anticipated expiration: 1978-04-04

Description

April 4, 1961 M. K. MURPHY 2,978,568

' ELECTRIC HEATER Original Filed May 3, 1957 r/Z 55 E 2 /6 PM [32 M (if (Z4, My

@ j; llllllllllillflllllilllifll INVEN TOR.

United States Patent ELECTRIC HEATER Maxwell K. Murphy, 535 W. Goldengate, Detroit, Mich.

Continuation of application Ser. No. 656,900, May 3, 1957. This application Nov. 3, 1958, Ser. No. 771,604

12 Claims. (Cl. 219-39) This invention relates to electrical space heaters and space heating systems and particularly to an improved combination radiant and convection heater, and to improved controls for such a heater.

This application is a continuation of my co-pending application Serial No. 656,900, filed May 3, 1957, now abandoned.

The benefits and advantages of radiant space heating have been recognized for some time, and the added convenience of electrical radiant heating has led to widespread adoption of wall mounted heaters utilizing glass heater elements. These glass heater elements have an electrical resistance grid fused on one surface thereof and are extremely eificient radiators of infra-red heat rays. Recently vitreous coated metal plates with a resistance grid fused on one of the coated surfaces have been used instead of the glass plates.

One objection to radiant heaters of the type mentioned is that their heating effect is slow in manifesting itself when the heaters are started from the cold state, and because most of the heating effect is radiant with only a small amount of convection, portions of the heated space not directly in the path of the heat rays sometimes remain cold and uncomfortable.

The principal object of my invention is to provide an improved combination radiant and convection heater which provides all of the advantages of true radiant heating and, in addition, provides convection heat circulated by a fan when fast warm-up is desired and when areas not in the direct path of the radiant rays are to be heated.

The accompanying drawing shows a preferred form of my invention and reference numerals designate parts thereon referred to in the following description.

In the drawing:

Fig. l is a front elevation of a wall heater embodying my invention;

Fig. 2 is a vertical section on an enlarged scale taken on the line 2-2 of Fig. 1;

Fig. 3 is a horizontal section on an enlarged scale taken on the line 3-3 of Fig. 1; and' Fig. 4 is a schematic wiring diagram of the heater control.

Referring to the drawing, it may be seen that my improved heater comprises a casing of metal, Fiberglas or other suitable material. The casing has back, side, top and bottom walls as shown, and is provided with an air intake 12 and an air outlet 14. A front wall 16 is recessed as shown to accommodate a radiant heating element 18 which is mounted on the front wall by means of the brackets 20 and screws 22.

The element 18 may be of glass type such as that shown in Glynn Patent Number 2,622,178 (in which event mounting means suitable for supporting glass must be used) but preferably is of the metal type. Referring to Fig. 3, it may be seen that the element comprises a metal sheet 24 coated on both surfaces with vitreous enamel 26. A metallic resistance grid 28 is adhered to one vitreous surface preferably by spraying while the metal is in molten state, and a protective coating 30 of silicone varnish or the like is applied to the surface carrying the resistor.

Application of a voltage across the resistor grid 28 will heat the panel and heat rays, the majority of which are in the infra-red range, will be radiated from the front surface of the panel. The recessed wall 16 is preferably polished such that it acts as a reflector and thus increases the radiant effect of the element by reflecting heat radiated from the rear surface which carries the resistor.

The element 18 is spaced from the reflector wall 16 and clearance is provided around all four marginal edges of the element thereby permitting convection air currents to enter the slot at the bottom of the element and to circulate upwardly of the space between the wall 16 and element 18 and out through the slot at the top of the element.

In the chamber 32 behind the wall 16, a second heating element 34 is mounted by means of brackets 36 or other suitable means. The element 34 is preferably identical with element 18, but other types of heating elements may be used inasmuch as the element 34 supplies no radiant heat directly to the room, but only convection heat.

A fan assembly 38 which includes a motor 40 and a bladed rotor 42 is mounted in the top portion of the easing as shown. A baflle 44 is mounted in the bottom portion of the casing and serves to direct air propelled downwardly through the chamber 32 outwardly through the outlet register 14.

The heater is adapted for automatic control by means of a thermostat T as shown by the schematic diagram of Fig. 4. As indicated, line voltage is connected to the element 18 through a relay actuated switch 46. Line voltage is similarly connected to element 34 by a relay actuated switch 48 which also controls the motor of fan 38. A transformer 50

supplies relay coils

52 and 54 under control of the thermostat T. Any suitable, commercially obtainable type of thermostat and switches may be used. It is preferred, however, that the thermostat be of the differential type so that the switches 46, 48, may be opened and closed at the same or different temperatures.

The heater operates as follows:

Let it be assumed that both switches 46 and 48 are open, the temperature of the room or other space to be heated is below that desired for comfort, say 70 F., that the thermostat T is set to close the switch 46 whenever the room temperature drops below 74 F., and to close the switch 48 whenever the room temperature drops below 70 F.

Both switches 46 and 48 will close through action of the

relays

52 and 54, and the

elements

18 and 34 as well as the fan 38 will be energized. Element 18 will, as soon as it warms to radiating temperature, emit heat rays which will intersect objects in their path causing warmth. Convection currents of air will enter the slot below the element 18 and will emerge as warmed air through the slot at the top of the element and will circulate about the room.

At the same time, air drawn in through the inlet 12 from the upper portion of the room by the fan blades 42 will pass downwardly of the chamber 32 on both sides of the element 34 and after being thus heated will pass outwardly through the register 14 and circulate around the room with considerable velocity.

This dual effect of radiant and convection heat will quickly warm the room. When the temperature of the room rises to 70 F. (or some other temperature as set by the operator), switch 48 will open and cut off the power to the element 34 and the fan 38. Element 18 will continue to emit heat rays until the room temperature reaches 74' F., or some other desired value, and then switch 46 will open cutting off power to the element. Under normal conditions, switch 46 will cycle on and off thereby causing element 18 to be alternately energized and deenergized in accordance with the conditions prevailing.

It is characteristic of the type of heating element disclosed that heat is retained in the element for a comparatively long period when current is off and thus the element will continue to radiate during an oif period of considerable length. It is recommended that the thermostat T be located somewhere in the room remote from the heater and not in the direct path of the emitted rays from element 18. Correct adjustment of the heater and of the thermostat setting will cause the room to be heated entirely by the radiant element 18, after the room has been warmed up, which is the most satisfactory as well as the most economical method of heating.

A drop in temperature, sudden or otherwise, to a value below the setting of relay 54 will cause energization of element 54 and fan 38, and both radiant and forced air convection heat will be available.

The width and depth of the heater are preferably chosen such that the entire assembly will fit flush with a wall surface between joists, which are usually 16 inches apart. The height can be chosen to present a pleasing appearance and in large rooms two or more units controlled by one or more thermostats may be used. In some instances where heat is desired in adjoining rooms or closets from one heater, a second register may be provided in the back wall of the casing opposite the register 14 and the bafile 44 eliminated or modified to provide airflow in opposite directions.

It will thus be seen that I have provided an improved electric heater which is compact, easily constructed and economical in construction, and which provides the advantages of both radiant heating and forced air convection heating with economy of operation and flexibility of control.

While I have shown and described a specific form of my invention, it will be understood that I have done so for illustrative purposes only and I do not intend to limit the scope of the invention except as set forth in the appended claims.

I claim:

1. A combined radiant and convectionspace heater comprising in combination, an upright casing, an electrical radiant heating panel mounted on the front of said casing and spaced from said casing to provide for circulation of convection air currents between said casing and said panel, a chamber within the casing, an electrical convection heating element in said chamber, blower means disposed in the upper portion of said casing for forcing air downwardly thereof, an air outlet in the lower portion of said chamber, and means operable automatically in response to temperature conditions in the heated space to energize said heating elements selectively.

2. A combined radiant and convection space heater comprising in combination, a casing having an air inlet, an air outlet and means for forcing an airstream downwardly through said casing, a front wall on said casing, a sheet type radiant heating element mounted on said front wall in spaced relationship therewith, slots at the top and bottom edges of said element providing means for circulation of convection air currents in the space between said wall and said element, said wall being polished to provide reflection of heat rays radiated from the back of said element, and a second heating element disposed in said casing in the path of said airstream.

3. A combined radiant and convection space heater comprising in combination, a casing having an air inlet, an air outlet and means for forcing an airstream through said'casing, a front wall on said casing, a radiant heating element of sheet form mounted on said front wall in spaced relation thereto, slots adjacent the top and bottom of said element permitting air to enter and travel upwardly of said element and out over the top of said element, a second heating element disposed in said casing in the path of said airstream, said forced airstream entering at the top and leaving at the bottom of said casing.

4. A combined radiant and convection heating arrangement comprising in combination, an upright casing having a chamber therein and a front wall, an air inlet in the upper portion of said chamber, an air outlet in the bottom portion of said chamber, an electrical heating element mounted in said casing in spaced relation to the walls thereof, blower means for circulating air from said inlet over said element and out through said outlet, an electrical radiant heating element mounted on said front wall in'spaced relation thereto, slots adjacent the top and bottom of said radiant element permitting circulation of convection air currents upwardly thereof, the direction of said currents being opposite to the direction of the air currents in said chamber.

5. A combined radiant and convection heating arrangement comprising in combination, an upright casing having a-chamber therein and a front wall, an air inlet in the upper portion of said chamber, an air outlet in the bottom portion of said chamber, and electrical heating element mounted in said casing in spaced relation to the walls thereof, blower means for circulating air from said inlet over said element and out through said outlet, an electrical radiant heating element mounted on said front wall in spaced relation thereto, slots adjacent the top and bottom of said radiant element permitting circulation of convection air currents upwardly thereof, electrically actuated means for energizing and deenergizing said elements and means operably associated with said electrically actuated means for energizing said blower when said first heating element is energized.

6. A combined radiant and convection heating arrangement comprising in combination, an upright casing having a chamber therein and a front wall, an air inlet in the upper portion of said chamber, an outlet in the bottom portion of said chamber, an electrical heating element mounted in said casing in spaced relation to the walls thereof, blower means for circulating air from said inlet over said element and out through said outlet, an electrical radiant heating element mounted on said front wall in spaced relation thereto, slots adjacent the top and bottom of said radiant element permitting circulation of convection air currents upwardly thereof, differential thermostat means for causing energization of said heating elements in response to temperature conditions in the heated space, said means being constructed and arranged to energize said radiant heating element at a preselected temperature and to energize said other heating element at a lower preselected temperature.

7. A combined radiant and convection heating system comprising in combination, an upright casing having a chamber therein and a front Wall, an air inlet in the upper portion of said chamber, an air outlet in the bot tom portion of said chamber, an electrical heating ele ment mounted in said casing in spaced relation to the walls thereof, blower means for circulating air from said inlet over said element and out through said outlet. an electrical radiant heating element mounted on said front wall, differential thermostat means for causing energization of said heating elements in response to temperature conditions in the heated space, said means being constructed and arranged to energize said radiant heating element at a preselected temperature and to energize said other heating element at a lower preselected temperature.

8. In a space heating system in combination, an electrical convection heating element, means for circulating air over said convection heating element and to the heated space for heating said space by convection, an electrical radiant heating element, thermostat means for causing energization of said heating elements in response to temperature conditions in the heated space, said thermostat means being constructed and arranged to energize both of said heating elements at a preselected temperature and to deenergize said convection heating element only at a preselected higher temperature.

9. In a space heating system in combination, an electrical convection heating element, means for circulating air over said convection heating element and to the heated space for heating said space by convection, an electrical radiant heating element, thermostat means for causing energization of said heating elements in response to temperature conditions in the heated space, said thermostat means being constructed and arranged to energize both of said heating elements at a preselected temperature, to deenergize said convection heating element at a first preselected higher temperature and to deenergize said radiant heating element at a second preselected higher temperature higher than said first preselected higher temperature.

10. In a space heating system in combination, an electrical convection heating element, means for circulating air over said convection heating element and to the heated space for heating said space by convection, an electrical radiant heating element, theremostat means for causing energization of said heating elements in response to temperature conditions in the heated space, said thermostat means being constructed and arranged to energize both of said heating elements at a preselected temperature, to deenergize said convection heating element when the temperature of the heated space reaches a preselected higher temperature, and to deenergize said radiant heating element when the temperature of the heated space reaches a second preselected higher temperature.

11. In a space heating system in combination, an electrical convection heating element, means for circulating air over said convection heating element and to the heated space for heating said space by convection, an electrical radiant heating element, thermostat means for causing energization of said heating elements in response to temperature conditions in the heated space, said thermostat means being constructed and arranged to energize and deenergize both of said heating elements at preselected temperatures, said radiant heating element being energized and deenergized at preselected higher tempera tures respectively than said convection heating element.

12. In a space heating system in combination, an electrical convection heating element, means for circulating air over said convection heating element and to the heated space for heating said space by convection, an electrical radiant heating element, thermostat means for causing energization of said heating elements in response to temperature conditions in the heated space, said thermostat means being constructed and arranged to energize and deenergize both of said heating elements at preselected temperatures, said convection heating element being energized and deenergized at preselected lower temperatures respectively than said radiant heating element.

References Cited in the file of this patent UNITED STATES PATENTS 1,422,130 Reynolds July 11, 1922 1,652,686 Schoenfeld Dec. 13, 1927 1,705,769 Kercher et al Mar. 19, 1929 1,910,105 Herring May 23, 1933 1,922,220 Sprague Aug. 15, 1933 1,986,350 Logan Jan. 1, 1935 2,065,760 Smith Dec. 29, 1936 2,471,784 Seifner May 31, 1949 2,707,745 Farr et a1 May 3, 1955 2,781,440 Petersen et a1 Feb. 12, 1957 2,827,540 Underwood Mar. 18, 1958 FOREIGN PATENTS 207,954 Australia May 15, 1957 486,711 Italy Nov. 17, 1953