US2971076A - Electric heating furnace - Google Patents

Description

1961 H. J. FERGUSON 2,971,076

ELECTRIC {HEATING FURNACE Filed July 20, 1959 2 Sheds-Sheet 1 ATTORNEY.

Feb- 7, 19 H. J. FERGUSON ECTRIC HEATING FURNACE 2 Sheets-Sheet 2 Filed July 20, 1959 FIGURE 4 FIGURE 5 FIGURE 8 FIGURE 7 FIGURE 6 ELECTRIC HEATING FURNACE Henry J. Ferguson, Kalispell, Mont. (800 N. 23rd St., Coeur dAlene, Idaho) Filed July 20, 1959, Ser. No. 828,314

4 Claims. (Cl. 219-39) This invention relates generally to an electric air heating and conditioning system, for a relatively small space, in which air is recirculated through said space by means of anappropriate duct work.

' More specifically the invention relates to an electric furnace and air circulating device for trailers or mobile homes designed especially for its small size, high efficiency, simple installation and ease in operation.

The principal object of the invention is to provide a new and novel electrical furnace of a small compact nature and of economical construction that may be readily used to heat a house trailer.

A further object of my invention is to provide a device as aforesaid that may also, during the summer months, be used to circulate filtered air through a house trailer.

A further object of my invention is to provide a device as aforesaid that is simple to install and does not require professional or specialized services of a furnace installer or an electrician in the installing process.

A further object of my invention is to provide such a device that has safety features to prevent the electric heatlug-element from becoming overheated and one that does not create too great an initial surge in commencing operation.

A still further object of my invention is to provide a new and novel combination of electrical heating element with a thermostat to give a greater temperature stability within a furnace and prevent the excessive switching on and off of the device.

While the foregoing objects are paramount, other and lesser objects of my invention will be set forth and become readily understandable from the preferred embodiment thereof set forth in this specification.

' The specification is to be construed and interpreted in relation with the accompanying drawings which illustrate the specific embodiment, and wherein like numbers of reference refer to similar parts throughout all figures, and in-which:

Figure 1 is a front vertical surface view of the entire furnace cabinet.

Figure 2 is a vertical cross-sectional view of the furnace cabinet with the door removed, thus showing the filter and furnace proper, taken on the line 2-2 of Figure 1 in the direction indicated by the arrows thereon.

Figure 3 is a vertical cross-sectional view of Figure 1, showing the internal structure of the furnace, taken on the line 33 of Figure 1 in the direction indicated by the arrows thereon.

Figure 4'is an electrical circuit diagram showing, diagrammatically, the electrical circuitry of my invention.

Figure 5 is an isometric view of the thermostat used in my furnace, showing its shape and the manner of limiting its motion.

Figure 6 is an isometric view of the preferred bar form of heating element of my furnace.

Figure7 is a vertical. cross-sectional view of Figure 6 taken on'the line 7--7 in the direction indicated by the arrows thereon.

Figure 8 is an isometric view of a coil-type heating element that may be used in place of the bar elements in the preferred form of heating unit of my invention.

Referring now to the drawings, and particularly Figure 1, it will be seen that my furnace is completely contained within a relatively small cabinet 11. This cabinet 11 is divided into an upper smaller chamber 12 and a lower or furnace chamber 13 by the filter 14. The filter 14 is of the ordinary variety of commerce slidably supported Within the furnace cabinet 11 by the channels 15, mounted thereon. Air is permitted free passage into the upper filter chamber 12 through the screen 16 in front of the upper chamber 12 of the furnace cabinet 11.

The lower furnace chamber 13 is of such appropriate size as to contain the blower assembly 17 and the furnace bonnet 18. The blower assembly 17 comprises a housing 50 shaped substantially as illustrated in Figure 2, communicating with the uppermost portion of the furnace bonnet 18 and containing a squirrel-cage type fan 19 actuated by the internally contained electric motor 20, preferably, but obviously not necessarily, of the shadedpole type. This fan assembly 19, well known in the art, takes air from the furnace chamber 13 through the central orifice 21 and propels it with downward velocity into the interior of the furnace bonnet 18. l

The furnace bonnet 18 is a rectangular structure shaped substantially as illustrated, preferably constructed from sheet metal, because of its ease in handling and fabrication.

The blower assembly 17 communicates with the in-" terior of the furnace bonnet 18 through the orifice 22 in the top of the said bonnet 18. The heating element 23 is supported within the furnace bonnet 18 in a central posi: tion spaced from the walls of the bonnet 18, by brackets 24 supported on the walls of the bonnet 18. I prefer to releasably fasten the flanges 51 of the heating element 23 to the brackets 24 with bolts or metal screws (not shown) so that the element may be readily removed should the occasion demand. The heating element 23 must be spaced away from the walls of the bonnet 18 to prevent the walls from becoming overheated, but yet must be such as to require a substantial portion of the air passing through said bonnet to pass over or near the heating bars 33, 34.

An air duct 25 communicates with the chamber of the furnace bonnet 18 and thence outwardly through the front of the furnace cabinet 11 to the grill 26, which is provided with the damper 27 to regulate the air flow therethrough. This duct 25 may be opened to provide a quick heating near its orifice.

The bottom portion of the bonnet 18 is provided with the outwardly flared flange 28 and the sheet 29, preferably of asbestos material, both of Which provide means of fastening the furnace bonnet to an appropriate support and connecting it to an appropriate duct system (not shown). I prefer to releasably fasten the flared flange 28 to its floor support with wood screws or the like so that it can be readily placed and removed at will. An orifice 30 may be easily provided in the asbestos sheet 29 with such appropriate size and positioning as will provide means of communication with an air duct 31 which communicates in turn to the various parts of the space to be heated.

A preferred form of heating element for my furnace is illustrated in Figure 6 of the accompanying drawings. This heating element comprises the outer flanged box 32, having bar-type resistance heating elements 33 spaced perpendicular to two of the sides of the box 32 in the upper portion thereof and having similar bar type resistance heating elements 34 in the lower portion thereof spaced perpendicular to the direction of the elements 33; A thermal cut-out switch 35 is provided on the box 32 to prevent an overheating thereof. I prefer to use a bar-type Patented Feb. 7, 1961 I aa'rrm'e resistance heating element 33, 34 as illustrated, because of the slower more even heat of lower temperature and the-greater heating surface offered byrthistype of element, but other types of elements mayserve well and may have other advantages. Another type of element that has been found to beeifective is that shown in Figure 8, comprising a' porcelain matrix 36 carrying the spiral wire-wound resistance element 37. This type element may be affixed in the upper and lower positions of the box 32 bybolting at the appropriate position. This type element 37 has the advantage of providing a faster heat but the disadvantage of a much more rapid heat loss and smaller heat transfer Surface.

The internal heat responsive switching. device or thermostat 38 is best illustrated in Figure 5. The switch proper is contained inthe box 39, but the heat sensitive portion of the thermostat comprises a relatively elongate, cylindrical member 40, and this shape is somewhat critical. The thermostat 33 must be positioned in and on the heating element 23 so that the heat sensitive member 43 is between the upper heating. element 33 and the lower heating element 34 and extends a substantial distance between the said heating elements 33, 34. Thermostats having such a construction are well known in the art. Many of such thermostats are continuously variable in their make-break point and for safety reasons it often becomes convenient or even necessary to limit this makebreak' point, particularly as to the highest temperature. Such devices normally have a diai-type indicator 41, as illustrated, and I have found in using this type indicator that a convenient maximum stop may be established in the device merely. by appropriately positioning a screw 42 in the casing to prevent the temperature selecting device 41 from passing beyond a certain predetermined safety point. a. continuously variable type, as one with only high and low make-break points will ordinarily serve equally well.

The. electrical circuitry of my device is illustrated, diagrammatically in Figure 4 of the accompanying drawings. I prefer to operate the system on ordinary commercially available alternating 220 volt split two-phase current. The current is manually controllable by the on-, off switch 52, and is transmitted, in'series, to the external line-voltage thermostat 45, appropriately located at some point in the area to be heated. The 220 volt current is thence supplied, in series, to the lower bank of resistance heating elements 34. Thus when the thermostat 45 is closed and calls for beat, this circuit is completed and the lower heater elements 34 begin supplying heat.

Because of the relatively great current required to operateall of the heating elements 33, 34, it is desirable and often necessary to divide the upper 33 and lower 34 heating elements into two separately controlled circuits, the upper to become operative after the lower, to prevent too great an initial surge of current across the supply lines when the device actuates. This second circuit for the upper bank of heaters 33 is in parallel with the first on the controlled side of the thermostat 33, and is closed or activated by the switching-relay 44.

This switching relay 44, preferably adapted to operate at 110 volts, is activated to a closed position by the thermostat 38 between the heating elements 33, 34 and when this thermostat 38 closes it also completes the 110 volt circuit through the variable rheostat 4-9 in series with the fan motor 20.

A manual-reset safety thermostat 35 is provided in series with both heater circuits to cut out the circuits should the heaters 33, 34 or bonnet 1% become overheated by reason of fan failure or other cause.

In operation, when the external thermostat 45 calls for heat, current is allowed to pass into the lower bank of resistance heating elements 34 which begin the heating Y h n h sslqwer nk 4 a ses he. m e a r of-the thermostat 38 to a predetermined point, both the It is not necessary that this thermostat 30 be offan and relay circuits are activated. The relay-44 closesand thus supplies current to the second or upper bank of heating elements 33. Current is also supplied to the fan motor which begins its operation to cause the fan 19 to force air over the heating elements 33, 34. The speed of the fan may be varied by regulation of the variable rheostat 49.

When suflicient heatis supplied to thethermostat 45 and it opens, the heater elements 33, 34 are immediately cut out, but-the fan circuit and-relay cireuitremain closed and the fan 19 continues to operate until the thermostat 38 between the heaters 33,34 cools sufiiciently to open its circuit.

The thermostat 38 between the heaters is adjustable, so that its upper cut-in and lower cut-out point may be varied; it may be continuously variable between limits or variable only between two limits. I-prefer to have the thermostats upper limit. at approximatelyv degrees Fahrenheit as hereinafter described to prevent-the bonnet 18 and its parts from overheating, Thelower, cut-in point should be at approximately SO'degrees Fahrenheit or below, for my invention to be adapted to summer-circulation. i

If it should be desired to usethe-fan for air conditioning or circulation without heat, as. well'it might in the summertime, the. cut-in point of the thermostat 38 i set at is lowest limit, which would be below the existing room temperature, and the fan circuit is then activated without activation of the heating elements 33,34. To stop the fan the thermostat 38is turned back t9 its highest cut-in point and the circuit'is broken as this temperature is well below the room temperature,

It should be noted that therheostat 4,9 has nooff-posi-v tion for safetyreasons. If the heaterelement becomes sufficiently hot the fan must be activated, and-thus prevent a possible overheating.

The air flow through the devicewhen it is operating-is readily apparent from the drawings. Air is taken in through the orifice 21 in the blower assembly 17, thus creating an air flow from the outside through the screen 16 into the filter chamber 12, thence through the filter-15 and into the furnace chamber 13 from whence theair circles through the heating elements, the blower assembly and over out into the duct system (not shown). and back into the room to eventually follow the same circuit again.

Although the foregoing description is necessarily of a detailed specific character in order that a specific embodiment of my invention may be completely set forth, it is to be understood that this specificterminology and:structure is not intended to be restrictive or confining, and that various rearrangements of'partsand modfficationof def tail may be resorted to without departing fromv essence, scope or spirit of the invnetion herein disclosed and'hereinafter claimed.

Having thusly described my invention, what I desireto protect by Letters Patent and what I claim is:

1. In an electric air heating and circulating device of he nature aforesaid, a cabinet having a smaller. filter chamber providing relatively free air passage thereinto, communicating through a filter with a relatively larger furnace chamber havinga furnace therein comprising in combination, an elongate bonnet; a variable means of causing air flow downward therethrough; a heating element positioned therein, in spaced relation with the walls of said bonnet, having a plurality of bar-like electrical resistance heating elements arranged in an upper bank and a lower bank with the elements of each bank mutually paralleled to each other and perpendicular to the elements of the other bank; an external thermostatpositioned in the areato be heated, adapted to allow current to besupplied to thelower bank of said resistance heating,

elongate temperature sensing member positioned between said upper bank and said lower bank of resistance heating elements, adapted to permit current to be supplied to the upper bank of said resistance heating elements and to actuate said means of causing air flow through said bonnet when said internal thermostat is heated to a predetermined temperature; a manually resettable safety thermostat adapted to interrupt the flow of current to said heating elements at a certain perdetermined safe operating temperature; means of supplying electric current to said circuits; and means of conducting heated air from said bonnet.

2. In an electric air heating and circulating device of the nature aforesaid, in combination, a rectangular bonnet; a blower mounted thereon and communicating therewith adapted to cause a variable air flow downward through said bonnet; a heating element positioned therein in spaced relation therewith, having an upper heating member and a lower heating member in spaced relation with each other, each of said heating members being adapted to permit the relatively free passage of air therethrough; a variable external thermostat positioned in an area to be heated and adapted to allow current to be supplied to one of said heating members when the temperature of said external thermostat falls below a certain predetermined point; a variable internal thermostat, having a relatively elongate temperature sensing member positioned between said upper heating member and said lower heating member, adapted to cause current to be supplied to said other unheated, heating member and to actuate said blower to cause air flow through said bonnet when said internal thermostat is heated to a predetermined temperature; a' manually resettable safety thermostat adapted to interrupt the current flow to said heating elements at a predetermined safe operating temperature; means of supplying electric current to said circuits; and means of conducting heated air from said bonnet.

3. In an electric air heating and circulating device of the nature aforesaid, the combination of a heating element having a plurality of bar-like electrical resistance heating elements arranged in an upper group of mutually parallel elements all perpendicular to a lower group of mutually parallel elements in spaced relation therewith;

an internal thermostat having a relatively elongate temperature sensing member positioned between said upper group and said lower group of heating elements, said thermostat being adapted to allow electric current to be supplied to one of said groups of the heating elements when heated to a predetermined temperature by the other of said groups of heating elements; and means of supplying electric current thereto.

4. In an electric air heating and circulating device of the nature aforesaid, the combination of a lower heating element controlled by a variable external thermostat in series therewith, adapted to allow current to be supplied thereto when the temperature of said external thermostat falls below a predetermined point; an upper heating element in spaced relation therewith, electrically connected in parallel with said lower heating element and in series with said external thermostat, controlled by a variable internal thermostat, in series therewith, said internal thermostat having a relatively elongate temperature sensing member positioned between said upper heating element and said lower heating element and being adapted to activate a relay causing current to flow in said upper heating member when said internal thermostat is heated to a predetermined temperature; a fan in series with said variable internal thermostat and with a variable rheostat adapted to regulate the speed of said fan, said fan being energized when said internal thermostat is heated to a predetermined temperature; a manually resettable safety thermostat in series with both of said heating elements adapted to interrupt the current thereto if heated to a predetermined unsafe operating temperature; and means of supplying electric current to said circuits.

References Cited in the file of this patent UNITED STATES PATENTS 2,061,258 Soverhill Nov. 17, 1936 2,471,784 Seifner et a1 May 31, 1949 2,544,544 Qualley et al. Mar. 6, 1951 2,697,164 Knapp et al Dec. 14, 1954 FOREIGN PATENTS 579,133 France July 24, 1924

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