Title:
Heating system
United States Patent 2386115


Abstract:
This invention relates generally to air heating systems and in particular to a portable self-contained heating system of unit type adapted to be operated when supported on a horizontal surface or suspended from a single point thereon. It is an object of this invention to provide an improved...



Inventors:
Holthouse, Harry B.
Application Number:
US42735542A
Publication Date:
10/02/1945
Filing Date:
01/19/1942
Assignee:
GALVIN MFG CORP
Primary Class:
Other Classes:
126/114, 206/509, 237/1R, 431/208
International Classes:
F02N19/10
View Patent Images:



Description:

This invention relates generally to air heating systems and in particular to a portable self-contained heating system of unit type adapted to be operated when supported on a horizontal surface or suspended from a single point thereon. It is an object of this invention to provide an improved air heating system.

Another object of this invention is to provide an air heating system of unit type which can be readily transferred from place to place and operated when suspended.

Yet another object of this invention is to provide a heating system of unit type for individually heating airplane engines for starting purposes which can be suspended in close proximity to the engine, or supported on any suitable horizontal surface adjacent the engine or cooling air passage leading thereto.

A still further object of this invention is to provide a heating system of unit type which is simple in design, rugged in construction, and comprised of a minimum number of parts, and adapted for efficient operation over a prolonged service life with minimum servicing attention.

A particular feature of this invention is found in the provision of a self-contained heating system of internal combustion type which is fully enclosed and transportable as a complete package, and capable of operation when supported on the ground or suspended from a single point thereon. When operated on the ground or other horizontal supporting surface the unit is of such a construction that a plurality of the units may be arranged in a superposed relation with each thereof operating independently of the other. Further objects, features and advantages of this invention will become apparent from the following description when taken in connection with the accompanying drawings in which: Fig. 1 is a front perspective view showing the complete heating unit of this invention: Fig. 2 is a diagrammatic illustration of a control circuit for the heating unit of Fig. 1; Fig. 3 is a transverse sectional view of the heater unit; 4 Pig. 4 shows a plurality of the heating units arranged in a superposed relation; Fig. 5 is a perspective view of an adjustable strap by which the heating unit of Fig. 1 may be suspended; 65 Fig. 6 is a sectional detail view of a fuel conditioning unit utilized in the heater of this invention; Fig. 7 is a longitudinal sectional view taken approximately along the lne 1-7 in Fig. 3, the 65 showing of the combustion chamber for the heating unit being somewhat of a developed view; Fig. 8 shows the application of the heating unit in a horizontally suspended position for heating an airplane engine; and Fig. 9 shows the application of the heating unit in a horizontally supported position for heating an airplane engine.

In practicing this invention, there is provided a package air heating unit of internal combustion type which includes a gravity feed fuel system and an electrical motor for operating fans for supplying air for combustion, and for circulating the air to be heated in thermal relation with the combustion chamber. The unit is fully enclosed, and is provided with electrical sockets thereon which are readily accessible for connecting the motor with a suitable source of electrical supply, such as a power line or an engine-generator set.

For suspending the unit in an operating position, a single suspension is provided at the top thereof which also serves as a handle for carrying the unit about. The outlet for the heated air passage has an angularly adjustable nozzle thereon so that the heated air may be directed in any one of a plurality of directions. A manually actuated control switch for the fan motor is operatively associated with a fuel valve in the fuel system in a manner such that fuel is admitted to the heater combustion chamber only after the motor is in operation. By virtue of the unit being self-contained and capable of being operated when supported on a horizontal surface or when suspended, it may be readily positioned in close proximity to the space to be heated regardless of the location of such space. This flexibility in positioning the heater of this invention for operation has been found particularly useful in the heating of airplane engines for starting purposes.

SReferring to the drawings, the heating unit II is shown in Figs. 1, 3 and 7 as having frame means designated generally as 18 and including horizontally extending supporting members I1 and II of substantially rectangular shape. The memSbers 17 and 18 are vertically spaced apart in a parallel relation by a substantially U-shaped connecting member 19 having leg portions 21 and 22 rigidly secured to the supporting members IT and II, respectively, with the connecting portion 21 Sbetween the leg portions 21 and 22 being'vertical and extended longitudinally of the supporting members IT and 18 and hence of the heating unit. An open frame or housing member 23 of a rectangular shape corresponding to the shape s of the supporting members IT and 18 is positioned about the frame means 16 so as to enclose the space between the supporting members 17 and 18 and forms closed compartments or chambers 24 and 26 to each side of the vertical portion 20 of the connecting member 19. The frame 23 is secured as by screws 29 to laterally bent flange *portions 27 and 28 integrally formed with the supporting members 17 and 18, respectively. Because of the flange portions 27 it is seen that the supporting member 17 is spaced upwardly from the lower end of the heating unit 15 for a purpose to be noted later.

Arranged within the compartment 24 are a motor 31, a fuel sump 32 and a fuel metering device 33 arranged in a fuel line 34 connecting the sump with a fuel nozzle 36. Also located in the compartment 24 is a valve unit 37 connected in the fuel line 34 between the sump 32 and metering device 33, and having a valve stem 38 projecting outwardly from the housing member 23. A control knob 39 is carried on the projecting end of the stem 38. The valve stem 38 has a cam 41 mounted thereon within the compartment 24 for operating a control switch 42 for the motor 31 concurrently with the operation of the fuel valve 31. The chamber 24 is in open communication with a fan chamber 43 having a fan 44 therein mounted on the shaft 46 of the motor 31. The fan chamber 43 (Fig. 7) is fluid connected with an annular air passage 47 formed about a combustion chamber 48 located in the compartment 26 and which will be later explained. The fan 44 functions to circulate air to be heated through the passage 47 in thermal relation with the combustion chamber and discharges the same through an outlet 49 in the side 51 of the frame member 23, the outlet 49 being open to the compartment 26. The air for the fan 44 is supplied through an inlet 52 also located in the housing side 51 but opening into the compartment 24. A screen 53 is extended over the inlet 52 to filter the air passing therethrough.

The motor 31 also operates a fan 54 for supplying combustion air to the combustion chamber 48. The air for combustion is drawn into the heater through an opening 57 in the side 58 of the frame member 23 and is discharged into an air supply chamber 59 located at the left end of the combustion chamber 48 as viewed in Pig. 7.

The annular passage 47 is separated from the air supply chamber 59, and chamber 60 for the fan 54 by a partition member 5B which is positioned transversely of the heating unit 15 and has an opening 61 therein for receiving a sleeve member 62. The sleeve member 82 is extended axially from -the combustion chamber 48 but is separated therefrom by a plate member 63. The sleeve member 62 and partition member 56 thus separate the chambers 59 and 60 from the annular passage 41 and chamber 43 for the fan 44.

The air from the supply chamber 59 is mixed with the fuel from the fuel nozzle 36 in a fuel conditioning unit 64 which is located in the chamber 59 at the inlet 66 of the combustion chamber 48 and will be later described.

The combustion chamber 48 extends longitudinally of the heater unit 15 and has an outer cylindrical casing 67 (Fig. 3) which is suitably secured to the connecting member 19. The combustion chamber 48 includes a tubular body member 68 of unit construction integrally formed with alternate peripheral sections 68 and radially extending fin elements 69. The fin elements 69 are bent double so that their inner ends are open to the bore or space within the tubular member 68. The member 68 is divided axially into a plurality of inter-connected passages 1 a--1 c, by a substantially X-shaped partition member 72. The side portions of the partition member 72 are fitted within the inner open ends of certain of the fin elements 69 and held therein as by welding or like means so as to be fixed relative to the body member 66. The casing 61, previously mentioned, is positioned about the fins and with the member 68 forms that portion of the passage 47 about the combustion chamber, the fins 69 extending into such passage portion. The heat transferred to the fins 69 is radiated to the air flowing through the passage 47 to heat the same. The mixture from the fuel conditioning unit 64 passes progressively through the combustion chamber passages 7 la-- Id and is exhausted from the heater through a tail-pipe assembly, indicated generally as 73, which is connected with the combustion chamber outlet 74 in the plate member 63. By virtue of this construction of the combustion chamber 48 the inlet 66 and outlet 74 thereof are both located in the plate 63, the exhaust gases being passed from the heater unit through the side 58 thereof.

The fuel conditioning unit 64, shown in detail in Fig. 6, includes a substantially tubular shaped housing 11 closed at one end 78 and open at its opposite or outlet end 79 for fluid connection with the combustion chamber passage 1 a. The closed end 78 of the conditioning unit 64 (Fig. 7) extends into the air supply chamber 59. The housing member 77 is provided in a high heat conducting-material and includes an air and fuel mixing chamber 81 at the closed end thereof and an equalizing chamber 82 adjacent thereto, the mixing chamber 81 and equalizing chamber 82 being separated by a heat conducting partition plate 83 having perforations 84 over the upper portion thereof. The equalizing chamber 82 in turn is separated from the combustion chamber passage 7 a by a heat insulating plate 86 having perforations 87 arranged peripherally therein.

Positioned axially through the housing member 77 and supported in the housing end 78 and partition plates 83 and 86 is an electrical heating unit 88. The heating unit 88 comprises a tubular shell 89 having a resistance wire 91 therein extending over that portion of the tube 89 within the mixing and equalizing chambers.

The fuel injection nozzle 36 is mounted at the closed end 18 of the conditioning unit 64 and is positioned within the air supply chamber 59. The nozzle 36 is formed with air ports or apertures 92 for admitting air from the air chamber 59 into the fuel stream within the injector. Additional air is supplied to the mixing chamber 8 1 directly from the air chamber 59 through openings 93 formed in the closed end of the housing 18 and about the fuel injection nozzle 36. During the normal operation of the heater the fuel admitted into the mixing chamber 81 from the nozzle 36 is directed against that portion of the copper tube 89 within the mixing chamber 81 and against the walls of the mixing chamber. Because of the high heat conductivity of the housing 11 and its thermal connection with the partition plate 84 and copper tube 89 these parts are readily heated on energization of the resistance 91 to at least a fuel vaporizing temperature.

The vaporization of the fuel in the mixing chamber 81 facilitates its being mixed together with the air supplied to the mixing chamber so that a substantially complete vaporous air and fuel mixture passes into the equalizing chamber - i ยท- - ==::Z 82 through the perforations 84 in the plate 83.

The equalizing chamber 82 functions to reduce the degree of turbulence in the mixture and with the plate 86 serves to disperse the same substantially uniformly over the cross-sectional area of 6 the conditioning unit outlet 19. A mixture of substantially uniform fuel density is thus admitted for burning into the combustion chamber 48, the combustion of the mixture being initiated by the passage of the mixture about the end 94 of the resistance 91, the degree of the ignition heat at the end 94 being determined essentially by the watt input to the resistance 91.

The fuel to be burned in the combustion chamber 48 is supplied from a fuel tank 96 (Figs. 1 and 3) which is of rectangular box shape and carried on the supporting member 18 in a superposed relation. Extended vertically through the tank 96 are symmetrically or rectangularly arranged tubes 97 which are aligned with corresponding nuts 98 secured to the underside of the supporting member 18. The tubes 97 terminate in the sides of the tank 96 and are suitably brazed or welded thereto so as to prevent any leakage of fuel from the tank at these points. Studs or bolts 99 having a headed portion at one end and a threaded portion at the opposite end are inserted within corresponding tubes 97, the threading of a stud 99 within a correspond'ng nut 98 rigidly securing the tank 96 to the frame means 16 in an obvious manner. 30( The fuel sump 32 is fluid connected with the tank 96 through connecting means 101. With the heating unit 15 in a horizontal position there is thus provided a gravity feed fuel system for the heating unit, with the fuel admitted to the condition- 3& ing unit 64 being controlled by the valve 37 previously mentioned.

In the operation of the heating unit the motor is connected with a suitable source of power through either one of the socket connections 102 4( and 103. The control switch 42 for the motor 31 is in a normally open position, which open position corresponds to a closed position of the valve 37 so that fuel is cut off from the mixing unit 84 concurrently with a stopping of the motor 31. On 4i manipulation of the knob 39 to rotate the cam 41 for closing the switch 42, sufficient lost motion is provided in the valve 37 so that the switch 42 is closed prior to any opening of the valve 37. A flow of air is thus initiated through the condition- 51 ing unit 64 prior to any admission of fuel thereto so as to provide for a scavenging action in the combustion chamber 48 before additional fuel is introduced therein.

Referring to the circuit diagram of Fig. 2 it is 5 seen that the closing of the switch 42 concurrently energizes the motor 31 and the resistance 91 which are connected in series. The sockets or receptacles 102 and 103 are connected to common lead wires 104 and 106, the use of a receptacle 6 102 and 103 being optional for a purpose to be later noted. To stop the operation of the heater the control knob 39 is reversely rotated to permit the switch 42 to return to an open position concurrently with a closing of the valve 37. Because 6 of the previously noted lost motion in the valve 37 the fuel admitted into the combustion chamber 48 is stopped prior to the stopping of the motor 31, to permit the sweeping of unburned fuel Sfrom the combustion chamber 48. There is thus 7 provided a self-contained heating unit which requires for its complete operation only an electrical connection with a suitable source of electrical supply.

Because of the box-like construction of the I heater unit 15 in those instances where a heat capacity is required in excess of the heat capacity capable of being produced by one unit, a plurality of the units may be used in a confined space by the arrangement of the units in a superposed relation. To accomplish this superposed assembly of the units for independent operation, the fuel tank 96 is made with a transverse length or width substantially equal to the distance transversely between the flange portions 27 of the lower supporting member 17. As previously mentioned the supporting member 17 is spaced upwardly from the lower end of the heating unit 15 so that on placing of one unit on top of another the flange portions 27 fit about the tank 96 to fix the relative positions of the units in a direction transversely thereof. The top of the frame member 23 (Fig. 3) is below the level of the top of the tank 96, with the bottom of the frame member extending downwardly to the bottom of the unit 15.

Thus when the units 15 are arranged in a superposed relation the frame members 23 are arranged adjacent to each other and fix the relative longitudinal positions of the units. The units, therefore, are locked together by the mating engagement of the bottom portion of one with the tank 96 of another.

The use of air heating units for some applications has been somewhat curtailed because of Ssuch units generally requiring a substantially rigid supporting surface upon which they can be operated. This disadvantage has been particularly objectionable where air heating systems of this type are used in the heating of airplane enSgines for starting purposes. In planes, particularly of large type, the engines are located a considerable distance away from the ground, so that when an air conduit is connected from a heating system on the ground to the engine much of the 0 heating efficiency of the heater is lost through such conduit connection. This loss of heat in the conduit connection necessitates a heating system having a capacity greater than would be required if the heat transmission losses were eliminated. i This disadvantage has been overcome in the present invention by providing a heater which is light in weight, has a relatively large heat output and yet which is sufficiently stable to permit of its being operated while suspended from a single ) point thereon. In one commercial embodiment of the invention the over-all length, width arid height of the unit 15 are about twelve inches, nine and one-quarter inches, and eight inches, respectively. This embodiment has a weight of approximately twenty-one pounds with the capacity of the fuel tank associated therewith being about one and a quarter gallons. This capacity of the fuel tank provides in the neighborhood of ten hours of normal heater operation. The motor 0 has a rating of about one-twentieth of a horse power with twelve volts and five amperes. The crpacity of the air circulating fan is about twenty-five cubic feet per minute, with the unit having an output capacity of from about twelve 5 to fifteen thousand B. t. u. per hour. It is to be understood, of course, that the parts of the heating unit can be relatively changed within the scope of this invention to provide for flexibility in its application to different operating conditions. 0 In suspending the unit 15 there is provided means indicated generally as 107 including an eye stud 108 inserted through a tube 109 extended vertically through the gasoline tank 96 substantially centrally thereof. The stud 108 is an'5 chored or threaded in a nut I II connected to the leg portion 22 of the connecting member 19.

The tank 96 has a recessed portion 96 therein about the stud 108 so that the stud is below the level of the top of the tank. The recess portion 95 is adapted to receive therein a chain link 96a connected in the eye of the stud 188. The link 95a is thus lifted from the recess when the unit is to be suspended or carried about, but is normally seated entirely within the recess 95 so as not to interfere with the vertical stacking of the units, as above described. The cap 100 for the fuel tank 96 is also inset for the same purpose. On suspending the unit 15 from the link 95A, therefore, the entire weight of the unit is supported on the stud 108 and distributed substantially uniformly 15. throughout the frame means 16. This manner of suspending the unit 15 is shown in Fig. 8 in connection with the heating of an airplane engine.

An adjustable suspension strap 112 (Fig. 5) having a snap hook 113 at each end thereof, is positioned about the propeller shaft 114 with the hooks 11 3 connected with the link 95A on the suspension member 108. As illustrated in Fig. 8 the airplane engine II is of the open face type, that is the engine cowl 1 I7 extends about the engine rearwardly from the propeller 114 and exposes the front of the engine 116 for direct cooling. With the unit 15 suspended directly from the propeller shaft and in front of the engine the heated air discharged from the outlet 49 is passed directly within the cowl 117 and about the engine 16.' In actual practice a canvas covering indicated at I18, is used to cover the exposed front portion of the engine, the heating unit being positioned on the outside of the covering with the outlet 49 positioned at an opening in the covering. To facilitate the discharge of the heated air in a plurality of directions the outlet 49 is provided with an adjustable L-joint 119 having a corrugated end 121 adapted to have a connecting hose stretched thereon when needed. Any directioning of the heated air is thus readily obtained by simply rotating the L-portion 119, and/or rotating the heating unit 15 about its suspension point. As illustrated in Fig. 8 an electrical extension 122 is connected at one end with the receptacle 103 which is located at the bottom of the heating unit IS. The opposite end of the extension 122 may be connected with an engine-generator set indicated generally as 123. The selection of the receptacle 103 when the heating unit is operated in a suspended position provides for greater stability in retaining the unit IB in a substantially horizontal position. 5 In.Pig. 9 the heating unit 15 Is shown as applied to the heating of an airplane engine 124 located in the fuselage of the plane and rearwardly of the pilot's cockpit 126. The inlet 121 of the cooling air passage leading to the engine 124 is positioned to the rear and above the cockpit 126 so that suitable means for supporting the heater in a substantially horizontal position can be readily provided. The supporting surface is positioned so that the heated air from the heating unit may be discharged directly into the inlet 127 to heat the engine 124. When the heating unit is operated in this position the plug or receptacle 102 is used for connection with the extension 122 leading to the engine-generator set 123, the receptacle 102 being located in the side of the unit 15. A receptacle 102 or 103, therefore, is readily accessible for operation of the heating unit in either a supported or suspended position, and in no way interferes with the vertical stacking of the units. It is to be understood of course that for multi-engine planes a plurality of the heating units of this invention may be concurrently used and operated from a single-engine generator set so that all of the airplane engines are heated together. In some instances it may be desirable to suspend a plurality of the units 15 in a stacked relation. The units in these cases are locked for movement together by locking means indicated generally as S, the sockets 102 being interconnected by an electrical harness H.

From a consideration of the above description and drawings, therefore, it is seen that the invention provides a self-contained heating unit of internal combustion type which is adapted to be operated simply by connecting it with a suitable source of electrical supply. This unit is small and compact, and of a construction such as to afford sufficient stability to retain it in a horizontal position when held suspended from a single point thereon. The arrangement of the fuel tank in a position above the combustion chamber provides for a gravity-feed system whereby the number of working parts requiring adjustment is appreciably reduced. The entire unit is completely assembled in package form, with the units so constructed that they may be stacked or superposed one on another in relative fixed positions for independent operation. All' of the working parts of the unit are arranged between two parallel vertically spaced horizontal plates, with the space therebetween being completely enclosed by a single housing member adapted to be slipped over the unit. Thus by simply removing the housing member all of the working parts are readily accessible. There are no parts having fine adjustments and since all of the working parts are completely enclosed the unit may be given considerable rough handling.

Although the invention has been described with specific reference to a preferred embodiment thereof it is to be understood that the parts thereof and their relative arrangement can be changed within the limits of this invention as defined by the appended claims.

I claim: 1. A heating unit of internal combustion type adapted to be suspended from one point in a substantially horizontal position, comprising frame means including a pair of horizontal supporting members, a vertical spacing member connecting said two supporting members and extending longitudinally of said unit, a combustion chamber on one side of said spacing member, means for supplying air to said combustion chamber, means for operating said air supply means, said air supply means and operating means being located on the opposite side of said spacing member, a fuel tank mounted on the upper one of said supporting members, suspension 'means extended vertically through said fuel tank, and means anchoring said suspension means with said frame means at said one point.

2. An air heating unit of internal combustion type adapted to be suspended from one point in a substantially horizontal position, Including a pair of flat substantially rectangular frame members, a substantially vertical member for spacing said two frame members apart and connecting the same together, a combustion chamber located to one side of said spacing member, means for supplying air to said combustion chamber, means for operating said air supply means, said operating means and air supply means being positioned to the other side of said spacing member and entirely within the confines of said two frame members, a flat rectangular fuel tank mounted on the upper one of said frame members in a substantially covering relation with said upper frame member, a suspension member located substantially centrally of the fuel tank and extending vertically therethrough, and means securing said suspension member with said vertical spacing member.

3. A heating unit of internal combustion type adapted for suspension in a substantially horizontal position from a single point thereon comprising, housing means of a substantially rectangular shape, a vertical frame member extending longitudinally of said housing means and dividing the same into two compartments, a combustion chamber, a passage for air to be heated thermally related with said combustion chamber, said combustion chamber and air passage being located in one of said compartments, blower means for supplying air to said combustion chamber and for circulating air through said air passage, a motor for driving said blower means, with said blower means and motor being arranged in the other one of said compartments, a fuel tank superposed on said housing means, means fluid connecting said fuel tank with said combustion chamber, means mechanically connecting together said fuel tank and housing means, and a suspension member located substantially centrally of said fuel tank and extending vertically therethrough for attachment with said frame means.

4. A heating unit of internal combustion type adapted to be suspended in a substantially horizontal position from a single point thereon comprising, frame means including a pair of flat horizontal members, a member for vertically spacing said flat members having the end portions thereof connected with said flat members, said spacing member extending longitudinally of said frame means, a combustion chamber positioned to one side of said spacing member having a passage for air to be heated in thermal relation therewith, fan means for supplying air to said combustion chamber and for circulating, air through said passage, a motor for driving said fan means, with said motor and fan means being located to the other side of said spacing member, a fuel tank mounted on the upper one of said horizontal members, a housing member for closing the space between said two flat members, and a suspension member extending vertically through said fuel tank and substantially centrally thereof for attachment to said frame means.

5. An air heating unit of internal combustion type comprising, frame means including a pair of substantially rectangularly shaped horizontal plate members, a vertical member extending longitudinally of said plate members retaining the same in a spaced parallel relation, an open rectangular housing member adapted to be positioned about said plate members to close the space therebetween, a combustion chamber within said housing member located to one side of said vertical member and having a passage for air to be heated thermally related therewith, means for supplying air to said combustion chamber and for circulating air through said passage, a motor for operating said air supply and circulating means, with said air supply and circulating means and motor being positioned within said housing member to the other side of said vertical member, a fuel tank superposed on said frame means and rigidly secured thereto, and means extending vertically through said fuel tank and substantially centrally thereof for attachment to said frame means providing for the lifting of said heating unit.

6. A portable air heating system comprised of an assembly of heating units of internal combustion type, each of said units including frame means having a pair of substantially rectangularly shaped horizontal frame members, a vertical member extending longitudinally of said frame members retaining the same in a spaced parallel relation, a combustion chamber positioned to one side of said vertical member having a passage for air to be heated in thermal relation therewith, means for supplying air to said combustion chamber and for circulating air through said passage, a motor for driving said air supply and air circulating means, with said motor and air supply and air circulating means being located to the other side of said vertical member, a fuel tank of rectangular shape superposed on the upper one of said frame members, a rectangularly shaped open housing member adapted to be positioned about said frame members and fuel tank for enclosing the space between said two frame members, said housing member having a rim portion projecting downwardly beyond said lower frame member, and the top of said housing member extending upwardly below the level of the top of said fuel tank, with the fuel tank on one of said heating units being adapted to be received within the housing member rim portion of another of said heating units to provide for the vertical stacking of said heating units, and means connecting together adjacent ones of said units to provide for the carrying of said heating system as a package unit.

7. A portable air heating unit of combustion type including housing means of substantially rectangular shape, a vertical frame member extending longitudinally of said housing means and dividing the same into two compartments, a combustion chamber, passage means about said combustion chamber for air to be heated, said combustion chamber and passage means being in one of said compartments, means for moving air to said combustion chamber and through said passage means, means for operating; said air moving means, fuel supply means, with said air moving means, operating means and fuel supply means being arranged in the other of said compartments laterally of said combustion chamber, a fuel tank carried on one of the walls of said housing means and in a substantially covering relation with said one wall, and means providing for the carrying of said heating unit connected with said housing means.

8. A self-contained heating unit adapted to form a part of multi-unit heating apparatus and comprising, in combination, a housing provided with side walls and including top and bottom walls set inwardly from the edges of said side walls to provide fuel tank receiving wells' at the top and bottom of said housing, liquid fuel burning heat generating means including a plurality of component parts mounted within said housing, a flat fuel tank snugly fitting within the well provided at one side of said housing and extending therefrom to fit snugly within the well at the opposite side of a second unit, thereby to interlock the two units against relative transverse movement, and fuel supply means connecting said tank with said heat generating means. HARRY B. HOLTHOUSE.

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