US2220108A - Heating apparatus for aircraft or the like - Google Patents

Description

Nov. 5, 1940.

w. E.-HUFFMAN El AL HEATING APPARATUS FOR AIRCRAFT OR THE LIKE Filed June 6, I933 I N V EN TORS MLLmM E. HurFmA/v.

4 Sheets-Sheet 1 Nov. 5, 1940. A A w. E. HUFFMAN ET AL 2,2 1

HEATING APPARATUS FOR AIRCRAFT OR THE LIKE Filed June 6, 193a 4 Shee't s-Sheet 2 INVENTORS IA/ILL/AM E. HUFFMAN. 3 ORGE 14K 1? 4 roRNt-V:

Nov. 5, 1940. w. a. HUFFMAN Em 2,220,108-

HEATING APPARATUS FOR AIRCRAFT OR THE LIKE Filed June 6, 193; 4 Sheets-Sheet 3 firq'ji 1:14

7 INVENTOR5 WILLIAM E. HUFFMA/V. & BY Geo/ s; W PVLOGLE.

Nov. 5, 1940. w. E. HUFFMAN ET AL HEATING APPARATUS FOR AIRCRAFT OR THE LI KE Filed June 6,,1933

4 Sheet-Sheet 4 60 L i f \i 63 4% /Z; IE 55 554 INkENTORS w/LL/HM E. HuFFMn/v. Y

Patented Nov. 5, 1940 UNITED. STATES PATENT OFFICE William E. Hufiman and George W. Replogle,

lDayt on, Ohio Application June 6, 1933, Serial No. 674,556

13 Claims.

f (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufacturecl and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon. I The present invention relates generally to apparatus for heating the'interior of a closed body vehicle, such, for instance, as cabin-type aircraft, automobiles or the like, and more particularly, to a vapor heating system in which the waste heat from the exhaust gases of the internal combustion engine in combination with a Vapor generator is utilized to generate vapor, and under certain conditions super-heated vapor which is passed through a suitable radiator and thereby obtain a. radiation of heat into the interior of said vehicle.

The primary object of the present invention is to provide a vapor heating system of a non-pressure type in which pressure or heat controlling devices are not required and in which the rate of vapor generation is controlled by automatically varying the quantity of liquid in the boiler instead of varying the quantity of heat to the boiler so that dangers incident to explosions are eliminated. The present invention contemplates a system in which the quantity of liquid in the boiler is continuously and automatically reduced or totally displacedby vapor and/or air when vapor in a greater quantity than the condensing capacity of the radiator is generated.

A further object of the present invention is to provide in a heating system of this character, a steam generator associated with the exhaust manifold of the internal combustion engine of a vehicle, a radiator unit connected to the outlet passage of the steam generator. for effecting a forced radiation of the heat received therefrom and an air cooledcondensingunit directly connected to the outlet passage of the radiator and the inlet passage of the steam generator, the purpose of which is to readily condense steam received from the radiator and permit a return flow of the condensed liquid into the generator.

A still further object of the present invention is to provide in a heating system of this character, a radiator having metering means so located with respect thereto such that as the liquid in the boiler is heated to the boiling point and the steam thus generated fills the radiator, it is permitted to pass into the condensing unit in a predetermined controllable amount. This tends not only to control and maintain the amount of steam passing into the condenser unit within the limits of its condensing capacity but at the same time to build up a back pressure within the radiator,

with the reservoir of the condenser unit which iswhich is effective in reducing the quantity of liquid in the boiler; that is, the back pressure is utilized to force the liquid from the boiler into the pipe leading into the condenser, or into the condenser, depending upon the difference existing between the back pressure and the static head of liquid in the pipe and condenser unit. Consequently, as the quantity of liquid is reduced, likewise is the quantity of steam generated reduced and by so regulating the metering device sufficient back pressure may be built up in the boiler to force all of the liquid out and into the reservoir of the condensing unit. Under no circumstances, therefore, will the back pressure exceed that necessary to lift the liquid from the boiler to the reservoir. Therefore, the invention contemplates a system which automatically permits only sufficient liquid to remain in the boiler to generate the amount of steam required. The size of the boiler and the radiator and the quantity of heat applied to the boiler are such (in order to obtain full heating capacity of the radiator) that more steam to a considerable degree is generated than can be condensed in the radiator. This results in the radiator being filled with steam under all conditions and as later explained provides the means of super-heating the steam. Since steam is entering the radiator in a quantity greater than its condensing capacity, and its escape is restrained through the variable orifice in the metering device, it is apparent that pressures will be built up in the radiator and boiler.

But since the bottom of the boiler communicates vented to the atmosphere, any pressure however slight, will lower the liquidin the boiler by forcing the liquid upward through the liquid return and transfer tube toward or into the reservoir. Reduction of the liquid in the boiler naturally results in reduction in the quantity of steam generated and the system therefore automatically permits only the quantity of liquid necessary to keep the radiator filled with steam to remain in the boiler.--

In operation there is very little liquid in the boiler, most of it, due to pressure, being in the return and transfer tube and in the reservoir. If all of the liquid is displaced in the boiler so that the boiler is completely filled with steam, a superheating of the steam will be obtained.

Other objects of the invention will appear in the following description and accompanying drawings and will be pointed out in the appended claims.

In the ensuing description, we will refer to steam generators and to the generation of steam, but'it should be understood that the present invention is equally applicable to the generation of vapors from any liquid such as, for example,

I ethyl-glycol, or any other mixture of liquid and that, therefore, the features which are described in connection with the generation of steam are, in

the main, equally applicable to the generation of other vapors.

The invention will be described in greater detail in connection with the drawings which illustrate a few typical installations embodying the principles of the present invention. It should be clearly understood, of course, that the invention is in no sense limited tothe type of boilers or radiators or method of installation illustrated in the drawings but is of general application, the drawings merely being typical illustrations of the application of the invention and do not consti-' of boilers which may be desirable in particular installations may be utilized in connection with the features of the present invention, as will appear fully to those skilled in the art, in any particular installation.

In the drawings: 1

Fig. 1 illustrates a type of installation of one embodiment of the invention adapted for use in connection with a cabin type aircraft.

Fig. 2 illustrates a modified form of the invention as applied to an amphibian type aircraft.

Fig. 3 illustrates a still further modification of the system as applied to an aircraft in which the engines are mounted in the wings.

Fig. 4 is a cross sectional view of a preferred embodiment ofthe heating system per se.

Fig. 5 is a front elevation of the radiator shown in Fig. 4.

Fig. 6 is an enlarged detail sectional view of the liquid trap illustrated in connection with Fig. 4.

Figs. 7 and 8 illustrate modifications of heating systems adapted for installation in different types of aircraft.

Fig. 9 is a slightly modified form of the invention illustrated in Fig. 4.

Fig. 10 illustrates diagrammatically a modification of the invention essentially adapted for 0 installation in either an automobile or an aerial vehicle.

Fig. 11 illustrates a further modification of the invention particularly adapted for use in connection with an automobile of the closed body type.

Fig. 12 is a modification of the steam generator,

75 Fig. 16 illustrates .diagrammatically a condenser unit of the type used in the system shown in Fig.7.

Fig. 17 is a modified form of condenser capable of being used with the system shown in Fig. 4.

Fig. 18 illustrates diagrammatically the condenser unit used in the system shown in Fig. 9.

Figs. 19, 20, 21 and 22 illustrate various modified forms of the radiators used in connection with the installations shown in Figs. '7, 8, 9 and 10.

Fig. 23 is an enlarged schematic view of the flapper valve unit illustrated in Fig. 7.

The adaptation of the system to different types of vehicles will be hereinafter described in detail and for the sake of clearness the correlated elements and slight modifications necessary in adapting the system to each type of vehicle illustrated, will be grouped in the following order:

A. The preferred embodiment of the invention illustrated in Figs. 4, 5 and 6; Fig. 9 is a modified form of the system shown in Fig. 4; Figs. 12 and 13, modifications of the generator which can be used in the system shown in Fig. 4; Fig. 17- a modified form of condenser capable of being used in the system of Fig. 4; and Fig. 18, a diagrammatic illustration of the condenser of the system shown in Fig. 9. Y

B. A modified form of the invention installed in an aircraft in which the engines are mounted in the wings, generally illustrated in Figs. 3, 7, 16, 20 and 23.

C. A further modification of the invention as installed in an amphibian type airplane included under which are Figs. 2, 8, 12, 13, 16 and 21.

D. A still further modification of the invention applicable to automotive or aerial vehicles, which included Figs. 10, 12, 13 and 22.

E. A form of the invention especially adapted for use in connection with automotive vehicles included under which are Figs. 4, 11, 14, 15, 17 and 19.

F. The adaptation of the preferred embodiment of the invention to a cabin type aircraft of conventional design including Fig. 1 and those figures enumerated above under group A.

Referring more particularly to the drawings included in group A, wherein corresponding parts are designated by like numerals throughoutthe several views, the system in the preferred embodiment of our invention herein illustrated comprises generally a vapor generator I0 as shown in Fig. 4, radiator II, and condenser unit I2. As shown in this figure, the radiator II includes an inletorifice I3 and an outlet orifice M,

the former being connected to the boiler I0 through the medium of a steam and liquid return tube I5, the outlet orifice having communication with the condenser I2 through the medium of the pipe l6. In a similar fashion, the condenser unit I2 is connected to the boiler I0 through the medium of a liquid return and transfer tube II. By connecting the several units of the system together in this manner, it will be apparent that a complete circulation of the steam will be obtained.

The vapor generator I0 comprises generally a cylindrical casing I8, the ends of which are adapted to be connected to the exhaust pipe I9 of an engine (not shown).

Centrally disposed within the casing I! there is a boiler indicated by the numeral 2I and heated gas passing through the exhaust pipe I9 and the casing I8 are directed around the boiler 2| to heat the liquid in the boiler. The boiler 2| shown in Fig. 4 and particularly illustrated diagramupper end of the boiler to permit the boiler to bereadily filled with water. An upstanding liquid level tube 24 is fixedly secured in the boiler, the

i been exhausted in the boiler.

lower end of which projects outwardly from the boiler where a drain cock 25 is attached, so that any excess water above the desired level can readily be drained therefrom. The steam and liquid return tube l5heretofore mentioned connects to the outlet passage 26 of the boiler 2i This passage illustrated in enlarged detail in Fig. 6 includes a liquid trap 21 provided with a depending drain tube which communicates with the lower end of the boiler in the manner illustrated, the purpose of which will be explained hereinafter.

The boiler 2| is also provided with an inlet passage 28 which connects with the liquid return and transfer tube ll heretofore mentioned. The inlet passage 28 is also provided with a tubular extension 29 terminating at the lower end or sump portion of the boiler 2|. By providing such an extension for the passage 28, no steam is capable of entering the pipe l6 and consequently entering the condenser unit l2 until all the water has As will be noted, the sump portion of the boiler projects beyond the wall of the casing [8 at its lower end so as to be outside the zone of heat. In this manner the liquid in the sump portion is maintained at a lower temperature to thereby prevent surging of the liquid upon entering the boiler. Consequently, the level of the liquid in the boiler is maintained in a stabilized condition.

The radiator Il, may have a coreof any suitable and preferred construction but herein is illustrated as having what is known as a turbotube core, indicated by the numeral 30 in Fig. 4 and consisting of banks ofvertioally extending flat tubes 3| provided with transverse radiating fins 32, which are connected at; their opposite ends with the upper and lower header tanks 33 and 34 respectively through the header plates 35 and 36. The core is entirely enclosed in a sheet metal shell or casing comprising side walls 31 and the-top and bottom walls 33 and 39. Suitable brackets 40 may be provided for conveniently mounting the radiator in any position desired.

The condenser unit I2 comprises a casing 4| the upper portion of which contains a condenser 42 and the lower portion of which consists of a reservoir 43 having an outlet 44 which connects with the transfer tube l1 heretofore mentioned.

The condenser is vented to the atmosphere by means of a breather tube 45. Theoutlet orifice M of the radiator is also provided with a metering valve 46 which operates to control the amount of steam entering the pipe [6. In the embodiment of the invention illustrated in Fig. 4, the transfer tube leading from the boiler 2| to the reservoir 43 is provided with a shut-off valve 49. Under these circumstances, it is necessary that the tube ll be provided with a by-pass line 50 leading into the reservoir 43 through the tube I6.

The operation of the system thus far may be described as follows:

Liquid in the boiler is heated to the boiling point by the exhaust pipe I9, and the steam thus generated rises through the pipe [5 to the radiator, fills the radiator and is permitted to pass into the pipe IS in a controllable amount through the metering valve .46 heretofore mentioned.

Steam flowing through the metering valve and pipe l6 enters and fills the reservoir 43 and flows upward into the condenser. The metering valve is so adjusted that no more steam than can be condensed in the condenser is permitted to pass into it, thereby preventing its escape through the vent 45 located in the top of the condenser. Liquid resulting from the condensation of steam in the radiator returns to the boiler through the pipe 15 that conveys the steam. Through the medium of the liquid trap heretofore mentioned, the condensedliquid is returned to the sump of the boiler in the manner illustrated in Fig. 4 instead of permitting the liquid to strike the heated side of the boiler as would otherwise be the case. At the same time the steam in condensing in the condenser unit I2 returns to the boiler fromthe condenser through the pipe I! by gravity flow by reason of the fact that in all installations the condenser is positioned above the level of the boiler. The size ofthe boiler and radiator and the heat applied, in order to obtain full heating capacity of the radiator, are such that more steam to a considerable degree is generated than can be condensed in the radiator. The metering valve 46 heretofore mentioned serves as a means to permit the escape of steam or air each time the system is placed into operation, and to provide a means of conveying steam in a controllable amount to the condenser unit and simultaneously establish a back pressure of the steam in the radiator. The orifice in the metering valve is such that in the full open position, no more steam than can be condensed in the condensing unit will pass through it, under any circumstances or atmospheric conditions.

Since steam is entering the radiator in a quantity greater than the condensing capacity of the radiator, it is obvious that if its escape is restrained through the metering valve, pressure will be built up within the radiator and boiler; but since the condenser is vented to the atmosphere and the condenser communicates with the reservoir to which the boiler is connected, it will be obvious that any back pressure, however slight, will lower the liquid level in the boiler by forcing the liquid in the boiler upwardly through the tube l1 and into the reservoir 43 until an equilibrium is established between the back pressure and the static head of liquid in the tube I1 and reservoir of the condenser unit. As the quantity of liquid is reduced, likewise is the rate of steam generated reduced and if the pressure becomes suflicient all of the liquid will be forced out of the boiler and steam generation will cease. When this occurs, it will be readily apparent that the boiler is completely filled with steam which will be superheated in a material degree. It should further be noted that the pressure will never exceed that necessary to lift the liquid from the boiler into the reservoir.

When no heat is desired, the metering valve is turned. to the off position and in a like manner the valve 49 in the line I1 is closed. When this valve is closed, communication between the bottom of the reservoir and the boiler is cut off and the .by-pass line' leading into the reservoir is open. With the metering valve closed the pressure built up in the radiator tends to force the water in the boiler through the return tube I! and by-pass line 50 into the reservoir of the condenser. Consequently, since the liquid cannot return to the boiler with the valve 49 closed,

steam generation ceases. The system shown in Fig. 4 may, if desired, be provided with a con- I pressure is built up in the radiator and boiler, this back pressure is suflicient to force all of the water out of the boiler and into the reservoir of the condenser unit. As long as the pressure in the boiler and radiator is suflicient to retain the water in the reservoir of the condenser unit, it is evident that the generation of steam will cease. When, however, there is a drop in this back pressure the liquid in the reservoir will automatically return to the boiler under the action of gravity.

A modification of the invention embodying those figures enumerated above under group B is generally shown in Figs. 3 and 7 which illustrate in diagrammatic form the system as applied to a low wing type airplane or one in which the engines are mounted in the wing. As illustrated more particularly in Figs. '7 and 20, the lower header tank 34' of the radiator I I' is provided with a ball check valve generally indicated by the numeral In this particular instance a condenser unit of the type illustrated in Fig. 16 is used. The by-pass line 50 is provided with a spring controlled check valve 52 shown more in detail in Fig. 16 which is normally adapted to open when the back pressure in the boiler is slightly greater than the head of liquid between the radiator and the condenser. By observing Fig. 16 it will be noted that the reservoir of the condenser unit is also provided with a flapper valve 53 instead of a manually controlled valve of the type used in connection with Fig. 4. In this installation the line I6 leading from the radiator into the condenser unit I2 is provided with a flapper valve, indicated by numeral 54' shown in enlarged-detail in Fig. 23. This flapper valve also connects with the line H leading from the reservoir of the condenser unit into the boiler. An installation of this type operates as follows:

When the liquid in the boiler is heated to the boiling point by the exhaust and the steam thus generated rises, it passes through the tube I5 into the radiator II. The float check valve 5I heretofore mentioned comprises an upper seat 54 and a lower seat 55 against which the ball 56 of the check valve normally seats. Under these circumstances steam in entering the inlet orifice I3 is permitted to pass into the radiator through the valve seat 54. When the steam in the radiator condenses, this liquid is collected in the bottom of the lower header tank 34', and as the level of the liquidrises the fioat ball 56 will rise, opening the lower outlet or valve seat 55 heretofore mentioned and the opening formed by the upper seat 54 will'be closed by reason of the ball seating there-against. When this occurs, the pressure of the steam is utilized to force the liquid in the ;lower header tank 34 from the radiator II through the pipe line 51 and conheretofore mentioned depending of course upon the back pressure established. The pressure of the water in the line I1 tends to normally maintain the flapper valve 53 shown in Fig. 16 closed until the head of liquid in the reservoir is greater than the back pressure of the water at which time the flapper valve will be opened to permit the water in the reservoir to fiow into the boiler.

The flapper valve 54 heretofore mentioned, and as illustrated in enlarged detail in Fig. 23,

which is connected between the line I6 and the transfer tube I'I' permits water which may-collect in the line I6 to readily drain back into the line I1 and thereafter into the boiler. Consequently, the line I8 which connects the radiator with the condenser unit is maintained clear of liquid and freezing-of the same in this line is efiectively prevented.

A third modification of the invention embody- "ing those figures enumerated above in connection with group C is generally shown in Fig. 2, which illustrates an installation especially adapted for use in an amphibian type aircraft. Such an installation requires that the boiler and condenser unit be positioned above the radiator. In this installation a radiator of the type illustrated in Fig. 21 is used. In this instance, it will be noted that the lower header tank 34a of the radiator I Ia is provided with a check valve 58-which is connected to the line I60. communicating with the condenser unit I2.. In this installation it will be noted that the tube I5a leading from the boiler I0 is connected to the upper header tank 33a, thereby permitting the steam to enter the radiator at the top of the radiator. After condensing in the radiator, the liquid passes from the radiator through the flapper valve 58 heretofore mentioned and enters the pipe IBa. When the head of liquid in the pipe I60. is sufiicient to overcome the pressure of steam in the radiator, the check valve 58 will be closed, and the liquid in the upstanding portion of the pipe IGa. will be trapped therein. When, however, the back pressure in the radiator becomes greater than the head of condensed liquid in the pipe IGa, the check valve will be again opened and the additional condensed liquid which has collected in the lower header tank 34a of the radiator will be forced out and into the tube I6a. This operation continues until the liquid in the pipe I Ea is lifted in successive stages and subsequently fiows into the reservoir of the condenser unit I2.

It should be noted in the several installations herein illustrated, that the size of the orifice in the tube I5 is considerably larger than the size of the orifice in the tube I6. Consequently, as the steam is entering the radiator faster than the steam can leave the radiator, it will be apparent that a back pressure is automatically provided which will force the liquid upwardly from the boiler into the reservoir in a manner heretofore described. It may, however, be convenient to provide a metering device in the position illustrated in Fig. 8 in order to better control the amount of steam passing through the pipe I 6a from the radiator into the reservoir.

Fig. 10 generally illustrates a further modification of a system embodying those figures enumerated above as included under group D, in this instance the radiator and condensing unit being designed as a unitary assembly of the type illustrated in Fig. 22. 'As shown in Fig. 22 the condensing portion 42b of the unit I2!) is interposed between an electric fan 59 and the radiator IIb. In this case, the reservoir 43b of the'condensing .neath-the floor of the pilots compartment. While unit is disposed beneath the radiator, and includes an opening through which the pipe [51) leading from the boiler to the radiator is adapted to be inserted. It should also be noted that the pipe l5b is insulated from the reservoir by means of a sleeve 6| of insulation material. An installation of this character may be found useful in vehicles where space is at a minimum. In this installation the transfer tube l'lb leading from the reservoir of the condenser unit into the boiler is provided with a by-pass line 62 and shut-off valve 63 of a type described in connection with- Fig. 4. This installation also includes a metering valve 64 used to control the amount of steam passing from the radiator into the condensing unit.

Fig. 11 illustratesa modified installation of the system embodying those figures enumerated above as, included under group E, in which case the system is particularly adapted for use with automobiles of the closed body type. In this installation the radiator II, which may be of the type shown diagrammatically in Fig. 19 and fan may be conveniently mounted upon the firewall be neath the cowling in the manner illustrated. In a similar manner, the condensing unit l2 may be conveniently positioned to the rear of the fan of the motor in order to effect a rapid condensation of the steam received in the condensing unit. The boiler 65 which is shown connected to the exhaust manifold of the engine is better illustrated in Figs. 14 and 15. As shown in these figures, this boiler is provided with a circular portion 66 forming an inner casing which is adapted to be connected to the exhaust manifold of the engine. An outer casing 61 of cylindrical cross section and forming a main boiler is adapted to be suitably welded or otherwise secured to the inner portion 66 of the boiler. By observing Figs. 14 and 15 it-will be noted that an auxiliary boiler unit 68 is provided which is mounted within the inner circular casing 66 of the boiler heretofore mentioned. This auxiliary boiler is connected at its upper and lower end to the main boiler 61 through the medium of connecting lines 69 and 10. As shown in Fig. 15 this auxiliary boiler is comparatively small in cross sectional area; consequently, the amount of water retained therein is substantially small. By providing an auxiliary boiler in the'manner set forth, it will be apparent that when the motor is started the exhaust gases in passing around the auxiliary boiler will immediately heat the water in the boiler to boiling point and a generation of steam will be effected in. a very short period of time. By placing the radiator beneath the cowling as illustrated, the metering device may be easily and quickly adjusted by the driver. The condenser unit in this installation is of a type illustrated in Fig. 17,

which includes the by-pass line 1| and the shutoff valve I2. 'If necessary, this valve may be conveniently operated by the driver from the dash through the medium of a flexible cable 13 and a hand lever".

Fig. 1 embodying those figures enumerated above as group A illustrates a typical installation of the system included under group F particularly adapted for use in connection with a cabin type aircraft. In this installation, it will be observed that the condenser I2 is mounted beneath the cowling 41 of the airplane, the cowling having an opening 48 formed therein to permit the air stream from the propeller to effect a rapid condensation of the steam in the condenser. For convenience, the radiator II is positioned bein most instances the radiator is illustrated as including an electric fan, the purpose of which is to circulate air into the interior of the vehicle, it will be apparent that in the case of an aircraft, the use of the fan may be dispensed with and the same efiect accomplished by utilizing the blast of the propeller to effect such circulation of air. To accomplish this end a main air duct 15 having its forward intake opening 16 positioned rearward of the propeller, is attached to and substantially encloses the radiator II. A complemental rear portion 11 conveys the heat from the radiator into the interior of the cabin throughsuitable registers 18.

The main air duct 15 has joined thereto forwardly of the radiator II a by-pass portion 19. This connects rearward of theradiator II with the portion 17. Valves 8!] and 8| having a common pivot 82 are pivotally mounted in the complemental portion 11 and the by-pass portion I9. Through suitable levers, generally indicated by numeral 83, the valves and 8| are connected to a thermostatic control device indicated by the numeral 84, mounted inside the cabin of the aircraft where it is subjected to the temperature in the cabin. The valves, as indicated, are arranged in a manner such that as the one is closing the other will open. In this manner the temperature of the air in the cabin of the aircraft may be controlled in a predetermined manner. If desirable, an auxiliary duct 85 may be connected to the rear portion ll of the air duct 15, to lead warm air into the pilots compartment.

It is believed that the foregoing description conveys a clear understanding of all the objects and advantages of our invention, and while reference has been made to various specific details of construction, it should be understood that the invention is not to be regarded as limited thereby inasmuch as many changes may be made without seriously affecting the advantages enumerated.

The attendant claims have been drawn with a view to covering not only specific embodiments illustrated, but all legitimate modifications and adaptations and they should be accordingly con strued. I

We claim:

' 1. In a cabin type aircraft having a radial engine, a heating system comprising, a steam generator including a sump, said steam generator being mounted in the exhaust line of said engine, a radiator having an inlet orifice, a steam supply conduit between said steam generator and the inlet orifice of said radiator for supplying steam thereto in quantities in excess of the condensing capacity thereof, said radiator including an outlet orifice, a condenser unit including a reservoir connected to the outlet orifice of said radiator and the sump of said steam generator for condensing the excess of steam received from said radiator, said condenser unit being positioned above said steam generator, a liquid tube interconnecting the reservoir of said condenser unit and the sump of said steam generator to permit gravitational flow of the steam, when condensed, into the sump of said steam generator, means cooperating with said radiator for transmitting said aircraft for operating said valve.

2. In a cabin type aircraft having a radial engine, a heating system comprising a steam generator including a sump, said steam generator being mounted in the exhaust line of saidengine, a radiator having an inlet orifice, a steam supply conduit between said steam generator and the inlet orifice of said radiator for supplying steam thereto-in quantities in excess'of the condensing capacity thereof, said radiator including an outlet orifice, a condenser unit including a reservoir connected to the outlet orifice of said radiator and the sump of said steam generator for condensing the excess steam received from said radiator, said condenser unit being positioned above said steam generator, a liquid tube interconnecting the reservoir of said condenser unit and the sump of said steam generator to permit gravitational flow of the steam, when condensed, into the sump of said steam generator, means cooperating with said radiator for transmitting the heat from said radiator into the interior of the cabin of said aircraft, said means comprising an air duct positioned rearward of the propeller of said aircraft and within its slip stream having a pair of branch leads intermediate its front and rear portions within one of which said radiator is mounted, a valve in each branch lead for controlling passage of air into the rear portion of said air duct, the air valve having an actuating member common to the other and arranged to open and close in alternate relation with respect to the other, and means responsive to temperature changes in the cabin of said aircraft for operating said valve and thereby direct hot and cold air into said cabin.

3. In a cabin type aircraft having a radial engine, a heating system comprising, a steam generator including a sump, said steamgenerator being mounted in the exhaust line of the radial engine, a radiator having an inlet orifice,a steam supply conduit between said steam generator and the inlet orifice of said radiator for supplying steam thereto in quantities in excess of the condensing capacity thereof, said radiator including an outlet orifice, a' condenser unit including a reservoir connected to the outlet orifice of said radiator and the sump of said steam generator for condensing the excess of steam received from said radiator, said condenser unit being positioned above said steam generator, a liquid tube interconnecting the reservoir of said condenser unit andthe sump of said steam generator to permit gravitational flow of the steam when condensed into the sump of said steam generator, means cooperating with said radiator for transmitting the heat from said steam radiator into the interior of the cabin of said aircraft, said means comprising an air duct positioned rearward of the propeller in said aircraft and within its slip stream having a pair of branch leads intermediate its front and rear portions, within one of which said radiator is mounted, a valve in each branch lead for controlling the passage of air into the rear portion of said air duct, the one valve having an actuating member common to the other and arranged to open and close in alternating relation with respect to the other and thermally controlled means in said cabin for operating said valve to thereby predeterminately regulate the temperature within said cabin.

4. In a cabin type aircraft having a radial en-' gine, a heating system comprising, a steam generator including a sump, said steam generator 2,220,108 sponsive to temperature changes in the cabin of being mounted in the exhaust line of said engine, a radiator having an inlet orifice in which the steam is received in quantities in excess of the condensing capacity thereof, said radiator including an outlet orifice, a condenser unit including a reservoir connected to the outlet orifice of said radiator and the sump of said steam generator for condensing the excess of the steam received from said radiator, said condenser unit being positioned above said steam generator, a liquid tube interconnecting the reservoir and the sump of a said steam generator to permit gravitational flow of the steam when condensed into the sump of said steam generator, means for selectively transmitting warm or cold air into the interior of the cabin of said aircraft comprising a main air duct having its forward end disposed in the air stream, the rear end of said air duct including a portion enclosing said radiator and a by-pass portion connected to said main air duct forwardly and rearwardly of said radiator, a shutter pivotally mounted in said first mentioned portion forwardly of said radiator, a second shutter pivotally mounted in said by-pass portion and connected to said first mentioned shutter, and thermostatic means including a lever arrangement directly connected to said shutters whereby movement of said thermostat opens one of said shutters simultaneously as the other is closin I 5. In a heating system of the class described, a steam generator, a radiator positioned below the level of said steam generator and including an upper inlet orifice for receiving the steam and a lower outlet orifice, a condenser unit including a reservoir positioned above the level of said steam generator, a pipe in the lower end of said reservoir communicating with said steam generator to permit gravitational flow of condensed steam into said steam generator, a return pipe between the outlet orifice of said radiator and the reservoir of said condenser unit, and restriction means associated with said radiator for restricting the fiow of steam through said outlet orifice and thereby establish a back pressure of the steam received therein which is utilized to effect an automatic discharge of the liquid from said steam generator into the condenser unit and to simultaneously force the condensate in the bottom of said radiator through said outlet orifice and into said return tube.

6. In a heating system of the class described, a steam generator, a radiator positioned below the level of said steam generator and including an upper inlet orifice for receiving the steam and a lower outlet orifice, a condenser unit including a reservoir positioned above the level of said steam generator, a pipe in the lower end of said reservoir communicating with said steam generator to permit gravitational flow of the condensed steam into said steam generator, a return pipe between the outlet orifice of said radiator and the reservoir of said condenser unit, a check valve in said return tube, and restriction means associated with said radiator for restricting the fiow of steam through said outlet orifice and thereby establish a back pressure of the steam received therein which is utilized to effect an automatic discharge of the liquid from said steam generator into said condenser unit and to simultaneously force the condensed steam into said condenser unit through said return pipe, said check valve being arranged to trap the head of liquid in the return tube as long as the static head of liquid in said return pipe is greater than the established 'I. A heating system as set forth in claim 5, said condenser unit being characterized by including means for trapping in said reservoir the liquid conveyed thereto from said steam generator.

-8. In a heating system of the class described, a steam generator, a radiator positioned below the level of said steam generator and including an upper inlet orifice for receiving the steam and a lower outlet orifice, a condenser unit including a reservoir positioned above the level of said steam generator, a pipe in the lower end of said reservoir communicating with said steam generator to permit gravitational flow of condensed steam into the steam generator, a return tube between the outlet orifice of said radiator and the reservoir of said condenser unit, and metering means in the outlet orifice of said radiator to restrict the passage of steam into said condenser unit and to simultaneously establish a back pressure of the steam received therein which is utilized to automatically discharge the liquid from said steam generator into the reservoir of said condenser unit and to force the condensed liquid in said radiator through said return tube.

9. In a heating system of the class described, a steam generator, a radiator positioned below the level of said steam generator and including an upper inlet orifice for receiving thesteam and a lower outlet orifice, a condenser unit including a reservoir positioned above the level of said steam generator, a pipe in the lower end of said reservoir communicating with said steam generator to permit gravitational flow of condensed steam into said steam generator, a return tube between the outlet orifice of said radiator and the reservoir of said condenser unit, and a metering device in said return tube adjacent the outlet orifice of said radiator to restrict the passage of steam into said condenser unit in a quantity within the condensing capacity thereof and to simultaneously establish a back pressure of the steam in said'radiato-r which is utilized to automatically discharge the liquid from said steam generator into the reservoir of said condenser unit and control the rate of steam generation.

10. In a heating system of the class described, a steam generator, a radiator positioned below the level of said steam generator and including an upper inlet orifice for receiving the steam and a lower outlet orifice, a condenser unit including a reservoir positioned above the level of said steam generator, a pipe in the lower end of said reservoir communicating with said steam generator to permit gravitational flow of condensed steam into said steam generator, a return tube between the outlet orifice of said radiator and the reservoir of said condenser unit, and a manually adjustable metering device in said return tube adjacent the outlet orifice of said radiator for restricting, in a predetermined amount, the passage of steam into said condenser unit and to simultaneously establish a back pressure of the steam in said radiator which is utilized to automatically discharge the liquid from said steam generator into the reservoir of said condenser unit and thereby control the rate of steam generation. I

11. In a heating system, a radiator including an inlet and an outlet orifice, a vapor generator operatively connected to the inlet orifice of said radiator for supplying vapor thereto, the inlet orifice of said radiator having an effective cross-sectional area sufliciently large to permit the steam to enter said radiator in quantities in excess of the condensing capacity thereof, a sump in said vapor generator, a condenser unit including a reservoir connected to the outlet orifice of said radiator and positioned above said steam generator for receiving and condensing the excess of steam from said radiator, an operative connection between the sump of said generator and said condenser reservoir to permit gravitational flow of the condensate into said sump, metering means in the outlet of said radiator for restricting in predetermined amounts the passage of excess steam from said radiator into said condenser unit and for simultaneously establishing a back pressure of the steam which is utilized to automatically effect a discharge of the liquid in said steam generator as long as the established back pressure is greater than the static head of the back-up liquid, and means associated with said condenser unit for trapping all or a part of the back-up liquid received from said vapor generator.

12. In a heating system, a steam generator including a sump, a radiator having an inlet orifice and an outlet orifice, said first-mentioned orifice having an effective cross sectional area sufiiciently large to permit the steam to enter said radiator in quantities in excess of the condensing capacity thereof, a condenser unit including a reservoir positioned above said steam generator for receiving and condensing the excess of steam from said radiator and to permit gravitational flow of the condensate from said reservoir into the sump of said steam generator,

metering means for predeterminately restricting the passageof excess steam from said radiator into said condenser unit and for simultaneously establishing a back pressure of the steam in said radiator which is utilized to automatically effect a lowering-of the level of the liquid in said steam generator as long as the back pressure therein is greaterthan the pressure head of liquid between the reservoir of the condenser unit and said steam generator, and means associated with said -condenser unitfor trapping a part or all of said liquid in said reservoir depending upon the back pressure established, said last-mentioned means including a liquid tube between the reservoir of the condenser unit and the sump of said steam generator, a by-pass line connected to said tube and the upper portion of said condenser reservoir and a manually operable shut-off valve' disposed between said reservoir and the junction of said by-pass line and liquid tube.

13. In a heating system, a steam generator including a sump, a radiator having an inlet orifice and an outlet orifice, said first-mentioned orifice having an effective cross sectional area sufiiciently large to permit the steam to enter said radiator in quantities in excess of the condensing capacity thereof, a condenser unit including a reservoir positioned above said steam generator for receiving and condensing the excess of steam from said radiator and to permit gravitational flow of the condensate from said reservoir into the sump of said steam generator, metering means for predeterminately restricting the passage of excess steam from said radiator into said condenser unit and for simultaneously establishing a back pressure of the steam in said radiator which is utilized to automatically effect a lowering of the level of the liquid in said steam"generator as long as the back pressure therein is greater than the pressure head of liquid between the reservoir of the condenser unit and said and in communication with the upper portion of said condenser reservoir and a manually operable shut-ofl valve disposed between said reservoir and the junction of said by-pass lineand liquid tube;

* GEORGE W. REPLOGLE.

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