US2482987A - Internal-combustion heater with air-cooled muffler - Google Patents

Description

p 1949. H. J. DE N. McCOLLUM 2,482,987

INTERNAL-COIBUSTION HEATER VIITH.AIR'-COOLD IUFFLER r1104 Jun. 5, 1943 a shuts-sheet 1 Sept. 27, 1949. .11. J. as N. M coLLuM 2,482,987

IITBRNAL-COIBUSTION HEATER WITH AIR-COOLBD MUFFLER l'ilod Juno 5, 19$ 9 Sheets-Sheet 2 Sept. 27, 1949. H. 4. DE N. M coLLuM 2,432,987

INTERNALCOIBUSTION HEATER WITH AIR-COOLED IUFFLE R Filed Juno 5, 1943 9 Sheets-Sheet 3 Sept. 27, 1949. H. J. DE N. M coLLuM 2,482,987

INTERNAL-COMBUSTION- HEATER, w-r'rn AIR-COOLBD MUFFLER Filed Jun. 5; 1943 9 Shee'ts-Sheet 5 Sept. 27, 1.949. H. J. as N. M COLLUM 2,482,937

INTERNAL-COIQUSTION HEATER WITH AIR-COOLBD IUFPLBR Filed m. s. 194: 9 Sheath-Shoat s @Zkmz M.

p 1949- 'H. .J- m: N M coLLuM 2,482,987

, INTERNAL-COMBUSTION HEATER WITH AIR-000L313 IUPPLBR Filed June 5, 1943 9 Sheets-Sheet 7 Se t. 27, 1949. H. J. DE N. M coLLuM 2,432,987

INTERNAL-COIBU'l-ION HEATER WITH AIR-COOLBD IUFFLER Filqd Jun 5, 1943 9 Shots-Shoot 8 Se t. 27, 1949. H. m a. M C OLLUM 2,482,987

INTERNAL-COMBUSTION HEATER WITH MR-COOLED IUFFIJER Filed Juno 5.. 1943 s slmu-shuz 9 filmy/Ear?- L @rjfiPlfDi/cf/Zmn Patented Sept. 27, 1949 INTERNAL-COMBUSTION HEATER WITH AIR-COOLED MUFFLER Henry J. De N. McCollum, Chicago, 111.; Thelma McCollum, executrix of said Henry J. DeN. McCollum, deceased, assignor to Stewart-Warner Corporation, Chicago, 111., a corporation of Virginia Application June 5, 1943, Serial No. 489.7

26 Claims. (01. 128-116) Another object of my invention is to provide a heater havingnew and improved means for preventing the accumulation of combustible mixture in the muflier.

Another object of my invention is to provide a heater having an improved means for cooling the exhaust gases.

Another object of my invention is to provide a heater having new and improved means for introducing secondary air into the hot products of combustion.

Another'object of my invention is to provide a heater havinga new and improved arrangement for preheating air utilized for combustion purposes.

Another object of my invention is to provide a heater having new and improved heat exchange means for heating the ventilating air.

Another object of my invention is to provide a heater having a less expensive and lighter weight muiller than those heretofore used.

Another object of my invention is to provide a heater having novel means for introducing secondary air into the products of combustion and for preventing products of combustion from entering the ventilating air.

Another object of my invention is to provide a new and improved heater which offers minimum resistance to gas and air flow therethrough.

Another object of my invention is to provide a new and improved heater which may be easily disassembled and re-assembled for inspection, repair, cleaning, or other similar purposes.

Another object of my invention is to provide a heater having the foregoing advantages and which is inexpensive to manufacture and capable of affording long and trouble-free service.

Other objects and advantages will become apparent as the description proceeds.

In the drawings:

Fig. 1 is a longitudinal, sectional view through a preferred embodiment 01' my invention;

Fig. 2 is a transverse, sectional view taken on the line 2-2 of Fig. 1;

Fig. 3 is a partial, transverse, sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is an irregular, transverse, sectional view taken on the net-4 of Fig. 1;

Fig. 5 is a longitudinal, sectional view through a modified form of my invention;

Fig. 6 is a transverse, sectional view taken on the line 6-6 of F18. 5;

Fig. 7 is a partial, horizontal section taken on the line 1-1 of Fig. 5;

Fig. 8 is an irregular, generally horizontal, sectional view taken on the line 8-! of Fig. 6;

Fig. 9 is an end view of the combustion chamber and associated parts and is taken in the plane of theline $401218. 7;

Fig. 10 is a longitudinal, sectional view of a further modification;

Fig. 11 is a longitudinal, sectional view of another modification;

Fig. 12 is a longitudinal, sectional view of another modification;

Fig. 13 is a longitudinal, sectional view of an other modification; and

Fig. 14 is a longitudinal, sectional view of another modification.

That embodiment of my invention which is shown in Figs. 1 to 5, inclusive, comprises a tubular casing 2|, having an inlet end 22 adapted to be supplied with air by a ram, blower, or other suitable means. The outlet end 24 of the casing may discharge directly into an airplane cabin or other space to be heated, or may be connected to a duct system leading to a plurality of outlets arranged at selected locations in the same or diilerent spaces. Any suitable or usual means may be provided for controlling communication between the ram and the casing 20 and between this casing and the space or spaces to be heated.

A combustion chamber 26 is located in the easing 2| adjacent the inlet end 22 and has an end wall 28 and a cylindrical side wall, 30. A pipe 32 is attached to the end wall 23 and extends through the center of the combustion chamber in coaxial relationship to the cylindrical wall 30 thereof. The lei'thand or inlet end of the pipe 30 is in open communication with the inlet end 22 of the casing II so that the combustion chamber 26 is annular.

A carburetor 34 is shown as being provided for the purpose of supplying combustible mixture to the combustion chamber 2. A pipe 38 connects the carburetor ll with any suitable source of fuel and one or more nozzles 38 deliver this fuel into the throat of a Venturitube 40 which forms a part of the carburetor 34. The lefthand or outlet end of the Venturi tube 46 is connected to one end of an induction pipe 42 which extends through the casing 26 and an opening 44 in the wall 36 of the combustion chamber and has a curved end 46 lying closely adjacent this wall. This end 46 is exposed to the heat of the combustion chamber and serves to preheat to the desired extent the combustible mixture being delivered to this chamber by way of the induction tube 42. As best shown in Fig. 1, this end 46 is inclined toward the end wall 28 of the combustion chamber whereby the combustible mixture is caused to whirl about the axis of this chamber adjacent the rear wall thereof and all fuel is completely consumed within this chamber.

As best shown in Fig. 2, a housing 48 is attached to the cylindrical wall 46 of the combustion chamber and provides a passageway 56 which communicates with the combustion chamber by way of an inlet 52 and an outlet 54. An igniter plug 56 is located in the passage 56 in spaced relation to'the walls thereof so that combustible mixture may flow around the plug 56 and be ignited by the electrical coil 56 in the lower end thereof. In ordinary practice, the igniter plug 56 is automatically disconnected from its source of current when the heater attains operating temperature and one or more re-igniters 66 (Fig. 1) may be provided to maintain combustion thereafter.

A ring 62 is attached to the cylindrical wall of the combustion chamber by welding, or in any other suitable manner, and serves to prevent the escape of liquid fuel from this chamber. The righthand end of the cylindrical wall 36 is provided with a flange 64 which is attached by screws 66, Or in any other suitable manner, to supporting brackets 68 and also to one end of a heat exchanger, indicated generally by reference numeral 16. Similar brackets I2 attach the other end of the heat exchanger to the casing 26, the brackets 68 and 12 being secured to the casing by screws I4, or in any other suitable manner.

The heat exchanger 16 comprises a sheet metal generally cylindrical shell I6 having its opposite ends welded or otherwise suitably secured to rings 18 and 86. The shell I6 is corrugated, as best shown in Fig. 3, and fins 62 have their bases secured in folds of the corrugated shell I6. The radially outward portions of the fins 82 project into the ventilating air passage 84 formed between the casing 26 and the shell I6.

A mufiler indicated generally by a reference character 86 is located in the heat exchanger I6 and has a cylindrical body 68 of sheet metal, or other suitable material, which cooperates with the shell I6 of the heat exchanger to form longi tudinally extending passages 66 for the hot products of combustion issuing from the combustion chamber 26. A sheet metal cone 92 connects the lefthand end of muifler body 66 with pipe 32 and serves to direct the hot gases issuing from the combustion chamber into the lefthand ends of the gas passages 96. As the hot products of com bustion traverse these gas passages, heat is given up to the shell I6 and fins 62, which transmit this heat to ventilating air flowing through the ventilating air passage 64. The gases then pass into an outlet chamber 84 and are discharged to atmosphere through outlet pipe 86 and fitting 96 and any suitable exhaust pipe attached to the threaded end I66 of this fitting.

The outlet pipe 66 is attached to a plate I6I which closes the righthand end of the heat exchanger I6 and which is attached thereto by bolts I63, some of which also serve to attach this heat exchanger to bracket I2. As best shown in Fig. 1, the outlet pipe 96 is provided with a boss or foot I65 which rests against the plate I6I at a special place provided by omitting one of the bolts I63. The pressure toot I65 forms an extra support for the outlet pipe 66 and gives this pipe and the fitting 66 attached thereto additional stability.

The mufller 66 has an annular sound absorbing chamber I62, which is illustrated as being in communication with the gas passages 96 through a single, annular row of openings I64 forming acoustic couplings between the annular chamber I62 and the gas passages. As clearly shown in Fig. 1, this single annular row of openings I64 is located adjacent the leithand end oi. the muiller 86 and serves to conduct sound into the annular chamber I62 where it is absorbed by the glass wool or stainless steel wool I66 located in this chamber.

The inner wall of the annular muiiier chamber I62 is formed by a tube I66 supported in end walls I I6 and H2. The tube I66 is in axial alignment with the pipe 62 and is shown as being of the same size as this pipe. The leithand end of the tube I66, however, is spaced from the righthand end of the pipe 62, so that air leaving the righthand end of the pipe 62 must pass through a conical chamber I I4 before entering the tube I66. This conical chamber H4 is formed by the cone 92 and end wall I I2 of the runner body and serves to prevent the wool in the lefthand end of the mumer from being overheated by the hot products of combustion issuing from the combustion chamber. The air passing from pipe 62 to tube I68 absorbs heat from the walls 01' this chamber so that this chamber also serves to increase the preheating of the air entering the tube I66.

Most oi the air flowing through the tube I66 enters pipes II 6 and I I6 leading to the air inlet of the carburetor 64. when the heater is operating normally, the air delivered to the carburetor through these pipes is preheated to'the desired temperature, and this preheating materially im proves the operation of the heater by aiding in the vaporization of the fuel delivered by the jet 36. A small part of the air flowing through the tube I66, however, passes through the annular space I26 formed between the righthand end of the tube I66 and the leithand end of pipe H6 and enters the outlet chambers 94 where it mixes with, dilutes and cools the products 01' combustion discharged to atmosphere by ways oi pipe 96 and fitting I66. This arrangement for diluting the exhaust is accomplished with very low pres sure drop and without requiring outside connecions.

The purpose in diluting the exhaust gases is primarily to prevent explosions when the heater is being started. In other words, the exhaust gases are diluted to such an extent that any mixture of fuel and air entering the exhaust pipe and discharged therefrom will not explode even though combustible mixture delivered to the combustion chamber passes therefrom to the exhaust outlet without being burned in the heater itself. The introduction of secondary air into the exhaust chamber 64 also serves to muile the exhaust end of the heater and permits the acoustic couplings between the interior of the muiiier and the gas passages to be confined to the combustion end 01' the heater, as clearly shown in Pig. 1.

I wish to call particular attention to the fact that I have provided a simple and emcient arrangement whereby the combustion air is preheated in such a way that it cools the muiller and serves to prevent overheating of any part of this muiller by the heat of the combustion chamber and the hot products issuing therefrom. These objects, together with the dilution of the exhaust are accomplished by a simple structure which may be easily assembled and disassembled for inspection, cleaning or repair. This structure also offers minimum resistance to flow of air and gas therethrough and may be constructed of light weight but sturdy parts which are capable of withstanding rough usage and giving long and trouble-free service. This heater is highly efficient and has a high heat output for a given size and weight and so is particularly adapted for use in airplanes wherein these factors are especially important, although it is to be understood that my heater is not limited to such use and is also adapted for other purposes.

In Figs. to 9, inclusive, I have shown a modified form of my invention wherein the heater com-- prises a casing I30 having its inlet end attached I are located in the casingI30 and are supported therefrom by brackets I38 and I40 attached by screws, or other suitable means, to the casing, heat exchanger and combustion chamber. As in the previous embodiment, the screws I42 which attach the brackets I38 to the combustion chamber and heat exchanger also serve to secure the combustion chamber and heat exchanger to each other.

A combustion air tube I44 has its lefthand end secured to the end wall of the combustion chamber and is in open communication with the air inlet pipe I32. The righthand end of the tube I44 is in sealed engagement with the lefthand end of a pipe I48 which connects with an external pipe I48 (Fig. 8) leading to a carburetor I80. A fuel supply pipe I52 connects the carburetor I I50 with an suitable source of fuel and this fuel is delivered to a jet I84 located in the restricted throat of the Venturl tube I88 forming part of the carburetor I80. A mixture of fuel and-air is formed in the Venturl tube I58 and this mixture is delivered to the combustion chamber I34 by way of induction tube I88, having an end I80 which extends through the casing I30 and side wall of the combustion chamber I34.

of combustion into the lefthand ends of the gas passages I10. The righthand ends of these gas passages discharge the cooled gases into an outlet chamber I18 formed between the end wall I80 of the muiller and a plate I82, which closes the righthand end of the heat exchanger. These gases are discharged to atmosphere through outlet pipe I84 and fitting I86 and any suitable exhaust pipe attached to the threaded end of this fitting.

In this embodiment of my invention, the mufiier I12 has an annular chamber I88 formed between the tube I44 and the outer wall I14, but in this embodiment of my invention this chamber is not filled with glass wool or stainless steel wool, or other sound absorbing material. Instead, the particular arrangement of the muiller and especially the flow of air therethrough are relied upon to absorb sound and prevent rumbling or other noises in the heater. A single row of openings I90- provided in the tube I44 connects the annular chamber I88 of the muilier with the air passageway'through the tube I44 and permits a. small amount of air to flow from the tube I44 into the annular space I88. Annular rows of openings I92 and I94 connect the annular space I88 with the gas passages I10 and a third an- The openings m, 192,194 and I88 are preferably of such size as to form acoustic couplings which connect the annular space with the air passage in the tube I44 and also with the gas passages through the heater. A small amount of air flows into the annular space I88 through openings I90 and this air flows slowly through the lefthand end of the muffler chamber I88 and out of the openings I92, I94 and I88 to mix with the hot products of combustion. This air performs several functions. It cools the lefthand end of the muiller and prevents this end from beingoverheated by the heat of the combustion chamber and the hot gases issuing therefrom. It also absorbs sound entering the muilier through the openings I92, I94 and I98 and The mixture delivered to the combustion chamber I34 by the induction tube I88 is ignited by an electrical igniter I82 located in the bracket provided by a housing I84 attached to the cylindrical wall of the combustion chamber. The combustion chamber is provided with one or more reigniters I68 to maintain combustion after the igniter I62 has been cut out by the usual thermostatic switch. A ring I88 is welded or otherwise secured to the cylindrical wall of the combustion eliminates rumbling and other noises. This air flow, together with the large annular space pro vided by. the inuiller chamber I88, serves eiTectively to quiet the heater. This air also functions as secondary air to dilute and slightly reduce the temperature of the gases entering the passages I10 and prevents the lefthand ends of these passages from being overheated by the inflowing gases.- The flow of secondary air through the muiller shell also prevents combustible gases from entering the chamber I88 when the heater is first turned on and before combustion occurs in the combustion chamber.

All of the foregoing advantages are obtained with a very small flow. of air from the tube I44 through the mufller and into the gas passages of the heater. The operation of this heater is exceedingly eflicient and thisefllciency is accomplished by a structure of minimum weight-since no sound absorbing material need be provided in the mufller chamber. The elimination of this sound absorbing material has a further advantage in that such sound absorbing material is a part of the heater which has the shortest life and which requires the most frequent attention and service.

In Fig. 10, I have shown a form of my invention which is more nearly th embodiment of Figs. 1 to 4, inclusive. In the embodiment of Fig. 10, the combustion chamber 2" and the heat exchanger 202 are attached to each other and to brackets 204 by screws 2", or in any other suitable manner. The other end of the heat exchanger 202 is separated by brackets 2" and the brackets 204 and 2" are attached to the heater casing 2lll by screws 212. The lefthand or inlet end of the casing 210 is connected to an air inlet pipe 214 which may lead from a ram, blower, or other suitable source of air supply. The righthand end of the casing 2| I, as in the previous embodiments, delivers the hot air to the space or spaces to be heated.

The heat exchanger 202 may be identical with the heat exchangers of the previous embodiments and a muffler 2l6 is located in this heat exchanger to cooperate therewith in the formation of the gas passages 2l8. A tube 22l extends through the combustion chamber and muilier and has its lefthand end in open communication with the air inlet pipe 2. The righthand end of this tube 220 is sealed to the lefthand end of a pipe 222 which connects with a second pipe 224 leading to the air inlet of the usual carburetor 226. A fuel supply pipe 22! connects the carburetor with any suitable source of fuel and an induction tube 230 conducts the combustible mixture formed in the carburetor to the combustion chamber 200.

The tube 220 forms the inner wall of an annular muiiier chamber 232 which is filled with stainless steel wool or glass wool or other suitable sound absorbing material. A single annular row of openings 234 connects this annular chamber with the gas passages 2 l8 and is clearly shown in the drawing. This annular row of openings is located adjacent the leithand end of the annular mulller chamber.

The outer cylindrical wall 2" of the muiiler has a conical extension 230 which serves to direct the hot products of combustion issuing from the combustion chamber into the lefthand ends of the gas passages 2I8. This conical extension 23! forms a tapered annular chamber 240 surrounding that portion of the tube 220 which is intermediate the combustion chamber 2 and the mufller 2I6. Annular rows of openings 242 and 244 connect opposite ends of the chamber 24. with the interior of the tube 22.. An annular member 246 is located in the tube 22. between the openings 242 and 244 and serves to restrict the flow of air through this portion of tube 22. sufiiciently to cause some of the air entering the lefthand end of this tube to pass through openings 242 into annular. chamber 24! and thence through openings 244 back into this tube. This circulation of air through the chamber 2" cools the lefthand end of the mumer 2l6 and also aids in preheating the combustion air delivered to the carburetor 228. In this form of my invention, no secondary air is introduced into the products of combustion and all air entering the lefthand end of the tube 220 is delivered to the carburetor 226.

The embodiment of Fig. 11 is generally similar v to that of Fig. 10, but shows a somewhat different The combustion chamber 250 and heat exchanger 252 are secured to each other by screws 254, which also connect these parts to brackets 25. The other end of the heat exchanger 252 is supported by similar brackets 25' and the brackets 258 and 258 are secured to the casing 2 by screws 262. The lefthand end of the casing 2 is connected to an air inlet tube 264 and the righthand end of the casing discharges heated air to one or more spaces to be heated.

A mufller 266 is located in the heat exchanger 252 and has an outer cylindrical wall 2" which cooperates with the heat exchanger 252 to form gas passages 210' therethrough. The wall 2" has a tapered lefthand end 212 connected to the enlarged righthand end 214 of a pipe 218 which extends through the combustion chamber 2" and whose lefthand end is in open communication with the air inlet pipe 284. The inner wall of the annular mullier 266 is formed by a tube 210 in sealing engagement with end walls 2" and 2'2 an intermediate partitions 224, 2", 2" and 2, which cooperate with the end walls and with each other to form compartments 222, 294, 2, 298 and ill. A single annular row of openings "2 connects each compartment with the gas passages 21l whereby sound may enter the several compartments and be absorbed by the glass wool or stainless steel wool or other sound absorbing material located therein.

A sheet metal cup 304 is located in thtapered end 212 of the wall 268. The openvend of this cup is closed by the end wall 2" of the munler and a single annular row of openings 3 forms the sole means of communication between pipe 21 and tube 218. All air entering pipe 21 flows around the base and side walls of cup "4 and passes through openings 3" into the interior of this cup and thence into tube 21!. In passing around the outside of cup 204, this air is preheated and serves to protect the lefthand end of the muffler against the heat or the combustion chamber 250 and the hot gases issuing therefrom. This preheated air then flows through tube 212 and pipes ill and 3" to carburetor 212, where a combustible mixture is formed which is delivered to the combustion chamber through induction tube 3 H. The usual igniter plug II and re-igniter II I are provided to initiate and maintain combustion of this mixture. A pipe 32. connects the carburetor with any suitable source of fuel.

In the embodiment of Fig. 11, all air entering the pipe 216 is preheated and delivered to the carburetor as combustion air. There is no provision for introducing secondary air into the products of combustion formed in the combustion chamber. The combustion air is preheated to the desired temperature and this preheating is so accomplished that it serves to protect the muffler against undue heat from the combustion chamber and hot products of combustion issuing therefrom. The mufller in this form of my invention is divided into a plurality of compartments arranged lengthwise of the gas passages and connected thereto at intervals throughout their length.

In the embodiment of Fig. 12, the combustion chamber 350 and heat exchanger 352 are attached to each other and are suspended from the casing 354 by brackets 356, as in the previous embodiments. The heater shown in this figure is similar to that shown in Fig. 11, except that a diii'erent type of muflier is used and the air which passes through the combustion chamber and muilier is not directed to the carburetor but is discharged to the end wall 888 of the combustion chamber and in open communication'with the air'inlet pipe 382. The opposite end of the pipe 888 is enlarged, as indicated at 888, and is attached to the conical end 888 of the outer cylindrical sheet metal wall 388 of the mumer 818, which is located within the heat exchanger 882. The inner. wall of the annular mufller is formed by a tube 812, which is secured to cylindrical wall888 by end walls 318 and 318. The elongated annular muffling chamber formed between the cylindrical wall 388. and tube 312 is preferably filled with stainlessfsteel wool or glass wool, as indicated in the drawing. A single annular row of openings 318 forms acoustic couplings between the elongated chamber of the muffler and the gas passages 388 through which the hot products of combustion pass in flowing from the combustion chamber 388 to outlet chamber, 882 from which these gases are discharged to atmosphere by way of outlet pipe'388 and fitting 888 and any suitable exhaust pipe which may be connected thereto.

The tapered end 888 of the cylindrical muilier wall 388 forms an air chamber 888 interposed between the combustion chamber 888 and the muffler 318. A sheet metal cup 888 is located in this chamber and has a single annular row of perforations 392 through which air must pass in flowing from the pipe 888 to the tube 812. This air flows around the outside of the cup 888 andthen through openings 882 into the interior thereof, absorbing heat from the pipe 888 and tapered end 388 and protecting the adjacent end of the muffler against excessive heat. This heated air then flows through tube 812 and is discharged intothe righthand or outlet end of the casing 388.

Most of the air delivered to the heater by the pipe 382 which connects this heater with a ram, blower, or other air supply means, passes between the casing 388 and heat exchanger 882 and absorbs heat from this heat exchanger. This heated air is then discharged from the rlghthand end of the heat exchanger into the righthand or outlet end of the casing 388, where it mixes with air which has passed through the center of the combustion chamber and the, center of the muifler by way of pipes 388, chamber 388, muiiler tube 312, and a pipe 888 which forms an extension thereof and which is welded or otherwise maintained in sealing engagement with the closure plate 388 for the righthand end of the heat exchanger.

The carburetor 398 may be of any conventional.

or suitable type and is supplied with fuel through a fuel supply pipe 888 which connects this carburetor with any suitable source of fuel. This carburetor is supplied with combustion air through a pipe 882 whose inlet end 888 passes through the casing 888 and is located inside this casing adjacent but downstream from the righthand end of the heat exchanger. Air entering this pipe 882 has passed over the heat exchanger or through the passageway passing through the center of the combustion chamber and muffler and when the heater is in operation, has attained a temperature which facilitates vaporization of the fuel mixed therewith in the carburetor 338. An induction tube 888 extends generally parallel to and outside of the casing 888 and has an end 888 which through the casing 888 and a wall of the combustion chamber 388 to deliver a combustible mixture to this combustion chamber. This mixture is originally ignited by an electrical igniter 8 and combustion is maintained by one or more re-igniters 2 after the igniter 818 has been cut out by the usual-thermostatic switch.

In the heater of Fig. 12, all of the heated air is'used either for ventilation or as combustion air delivered to the carburetor 338. None of this heated air is introduced as secondary air into the products of combustion. The arrangement I of Fig. 12 is preferableto that of Fig. 11, where the amount of air necessary to cool the muffler is considerably greater than the quantity of combustion air required by the carburetor. The somewhat simpler muiiler of Fig. 12 is satisfactory for most purposes, but the more complex and expensive muiller of Fig. 11 can be substituted therefor, if required.

The heater shown in Fig. 13 is similar to Fig. 11 in that most of the air passing through the muffler is directed to the carburetor and used as combustion air. The heater of Fig. 13 diifers from Fig. 11, however, in that Fig. 13 shows a different type of muiiler and part of the air directed into the mufiler is introduced into the products of combustion as secondary air to aid in the reduction of noise.

In Fig. 13, the heater has a combustion chamber 858 attached to one end of a heat exchanger 882 and supported in a casing 888 by means of brackets 888 and 888. The lefthand or inlet end of the casing 888 is attached to an air supply pipe 888 connected with a ram, blower, or other suitable air supply means.

A muiller 882 is located in the heat exchanger 882 and comprises a cylindrical wall 888 and end 812 which is welded or otherwise sealed to the' muffler end wall 888. The cylindrical wall 888 of the mufller is provided with an annular series of openings 818 adjacent the end wall 888. These openings form acoustic couplings between the muiller chamberand the gas passages 818 in the heat exchanger 882. These openings 818 also permit secondary air toflow into the passages 818 and mix with the products of combustion passing therethrough to aid in reducing noise.

A sheet metal baflie 818 is located in the muffler chamber and is attached to the end wall 888 by rivets 818, or in any other suitable manner. This baille 818 causes the air entering the muiiler through pipe 818 to flow in close contact with the end walls of this muffler and to prevent these walls from becoming overheated. The presence of the bafiie 818 also facilitates flow of air through the openings 812 into the gas passages 8 18.

Pipes 888 and 882 connect the righthand end of the muiller chamber with the air inlet of a carburetor 888 which'is supplied with fuel from any suitable source through a fuel supply pipe 838. An induction tube 888 has its outlet end 898 located in the combustion chamber 888 and delivers a combustible mixture of fuel and air to this chamber. This mixture is initially ignited l 1 is cut out by the usual thermostatic switch, combustion is maintained by one or more re-igniters Only a small proportion oi the air delivered to the heater by air supply pipe Ill is required for combustion purposes, or as secondary air. Most of this air is heated by passing between the easing 454 and heat exchanger "1 and is discharged from the righthand end of the casing 454 into one or more spaces to be heated. The products of combustion leave the righthand ends or the gas passages I to enter an outlet chamber 4", from which they flow to atmosphere through outlet pipe 488 and outlet fitting III and any suitable exhaust pipe connected thereto.

As clearly shown in this figure, the pipe III which conducts heated air to the carburetor inlet is preferably formed of two sheet metal sections 502 and 5M. The section I" has a pair of diametrically opposed flanges Ill and the section 504 has a pair of diametrically opposed iianges 508, abutting flanges Ill and "I, being welded together to form the unitary DlDe structure. The outlet pipe 49! is preferably of the same construction and the pressure loot ill constitutes an extension of the inner flanges of two pipe sections.

In this figure, the combustion air is supplied by the same air supply pipe which furnishes the ventilating air to be discharged into the cabin or other space or spaces to be heated. In some installations it may be duirable to provide a separate source for the combustion air and in this figure the end wall ill or the combustion chamher 450 is provided with a ring ill welded to this wall and provided with tapped holes ll, so that assaosv walls andnnsorthisheatexchanger. 'lhecooled gases flow from the righthand ends of these as passages ill into an outlet chamber Ill and are discharged to atmosphere through outlet pipe i" and fitting I", and any suitable exhaust pipe attached to the threaded end 0! this nttlnz. In this heater, all or the air supplied by pipe passes around the combustion chamber Ill and through the annular passage I between the casing I24 and shell I42 0! the heat exchanger. This air absorbs heat irom the heat exchanger and passes from the righthand end of the heat exchanger into the outlet end or the casing.

A muiller, indicated generally by reierence numeral I, is located in the heat exchanger in and has a cylindrical side wall I and end walls "8 and I" towing a mulling chamber which communicates-with the gas passages I82 through a single annular row of openings "2 located in the side wall 5 adjacent the end wall I. This muiiler is exposed to the heat or the combustion chamber and the hot gases issuing therefrom and I have provided means for cooling this muiller by introducing air thereinto. This cooling means comprises a pipe I, having an inlet end "0 located in the outlet end of the casing!" and positioned to receive heated air discharged from i the righthand end oi the heat exchanger. This a separate air inlet pipe for the combustion air may be secured to this end wall in sealed relation to the pipe 410 extending through the combustion chamber. Where a separate source of air is provided for combustion purposes, this separate source may be a ram, blower, or any other suitable means. Certain of the other figures have identical means for attachment or aseparate air supply pipe for the combustion air.

The murder 2 is of simple construction and design and the muiiiing chamber requires no sound absorbing material, such as stainless steel wool, or glass wool. The sound absorbing qualities of the chamber itself, together with the flow of air therethrough which increases these sound absorbing properties, is adequate to provide a quiet heater where some secondary air is discharged into the gases flowing through the gas passages 416. In this particular embodiment of my invention, the weight and cost of the sound absorbing material are eliminated and since only a very small amount of air is introduced into the products of combustion as secondary air, the heater is highl eiiicient and has a high beat output for a given size and weight.

The heater of Fig. 14 has a somewhat diflerent arrangement for introducing cooling air into the mumer. In this heater the combustion chamber 520 and heat exchanger I22 are supported in the cylindrical casing 2| by brackets I28 and ill. The lefthand or inlet end of the casing 524 is conneoted to the usual air supp y P pe "I and the righthand or outlet end or this casing discharges directly or indirectly into the space or spaces requiring heat.

The hot products of combustion flow from the ri hthand end of the combustion chamber III into the lefthand ends 01' the gas passages 32 in pipe passes through the rear wall III of the munier and is inclined downwardly so that its outlet end 558 is located closely adjacent to and substantially opposite the center of the end wall 5".

The ventilating air entering the muiler through pipe 5" serves to prevent overheating of any part of the muiiler 5 and a mall part of this air passes through openings I52 into gas passages I32 and serves as secondar air which mixes with the products of combustion and tends to eliminate noise therefrom The end wall "I is the part of the mufller which is most likely to become overheated and the pipe "4 is so positioned and arranged that it discharges air directly against this wall to prevent such overheating. Most oi the air entering the muiiier through pipe Ill is utilizedas combustlonairandpassestothecarburetor I" by way 01' pipes in and I". This air absorbs additional heat from the walls of the muilier so that the combustion air reaching the carburetor is considerably hotter than the ventilating air passing from the rkhthand end of the heater casing 524 into the airplane cabin or other space or spaces requiring heat. v

A fuel supply pipe I" connects the carburetor I with any suitable source or fuel and the mixture of fuel and air formed in this. carburetor is delivered to the combustion chamber ill through an induction pipe "I having an outlet end "I located in this chamber. The combustible mixture delivered to the combustion chamber III is ignited by the usual electrlcal'igniter I12 and after this igniter is cut out by the usual thermostatic switch, a re-igniter I," insures continued combustion of the inflowing fuel and air mixture. A ring "I prevents escape of liquid ll fuel from the combustion chamber when the heater is first started.

The heater of Fig. 14 is particularly advantageous where it is desirable to have the combustion air supplied to the carburetor at a tempera- 7c ture materially greater than that of the ventilating air leaving the heater. This heater also utilizes a muiiler oi simple construction which requires no sound absorbing material, such as stainless steel wool or glass wool, and is inexthe heat exchanger and give up their heat to the II p i and 8m inweight.

- 13 Rachel the embodiments herein shown and described, comprises a simple heater which may be" made of lightweight but strong and rugged parts and which has a high heat output for a relatively small, compact andlightweight struc-' ture of high efllciency. In each of these embodiments, special air circulating means is provided to prevent any part of the mumer from becoming overheated so that the portion of the muiiler which is most exposed to the heat of the combustion chamber and the gases issuing therefrom is protected against burning out and is afforded a life equivalent to that of the other parts of the heater. These advantages are accomplished in a heater which may be easily disassembled and reassembled for purposes of inspection, cleaning and repair and all parts of the heater are so designed that they may be easily manufactured by conventional methods and equipment.

Because the heaters herein shown and described are compact and eflicient and have a high heat outputfor agiven weight, these heaters are particularly adapted for heating the cabins and other spaces in an airplane. My novel heaters, however, are equally capable of use for other purposes. The particular heat exchanger shown herein is claimed in my co pending application, Serial No. 464,451, filed November 4, 1942, now Patent No. 2,380,602 of July 31, 1945, and the various combustion chambers and other features not herein claimed are claimed in other co -pending a. A heater oi the class described, comprising a casing having one end adapted to be connected to a source of air supply, means forming a combustion chamber located in said casing, a heat exchanger connected to said combustion champrior applications.' Other forms of heat exchangers and combustion chambers could be used in lieu of those herein shown and described and various other changes could be made without departing from the scope of my invention. In

fact my invention may be incorporated in numerous other forms and includes all variations and modifications falling within the scope of the appended claims.

Iclaim:

1. A heater comprising a casing adapted to be connected with a source of air supply, means forming a combustion chamber in said casing, a tubular heat exchanger in said casing connected to said combustion chamber and receivingproducts of combustion therefrom, a mufller located in said heat exchanger, said mui'iler including a muiliing chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, and means for circulating part of the air supplied to said casing through said mufller to prevent any part of said mufller from becoming overheated.

2. A heater of the class described, comprising a casing having one end adapted to be con nectedto a ram or other source of air supply, means forming a combustion chamber located in i said casing, a heat exchanger of tubular conformation having one end attached to said combustion chamber, a sheet metal muilier located in said heat exchanger and having a wall cooperating therewith to form gas passages for hot i products of combustion issuing from said combustion chamber, said muiller including a'muffling chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, means forming an air cham-. ber between said muiiier and combustion chamber, and means for creating air flow through said air chamber to protect said muiller against overheating.

ber and receiving hot products of combustion therefrom, a muiiier located in said heat exchanger, said mufller including a mui'iling chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, means forming an air chamber between said mufller and combustion chamber, means providing a passage for supplying air to said chamber from said source, and an outlet passage for said chamber extending through said muiiler.

4. A heater of the class described, comprising a casing having one end adapted to be connected to a source of air supply, means forming a combustion chamber located in said casing, a heat exchanger connected to said combustion chamber and adapted to receive hot products of combustion therefrom, a mufiler located in said heat exchanger, said muflier including a mufliing chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, means forming an air chamber between said muiiier and combustion chamber, and a pipe extending through said combustion chamber and connecting said air chamber with said I source of air supply.

5. A heater of the class described, comprising a casing having one end adapted to be connected to a source of air supply, means forming a coma exchanger connected to said combustion chamber and adapted to receive hot products of combustion therefrom, a muiiier located in said heat exchanger, s'aid mufller including a muiiiing chamber and means-acoustically coupling said chamber to said heat exchanger andcombustion chamber for damping out incipient sound and pressure waves, means forming an air chamber between said muiiier and combustion chamber, and means for creating'air flow through said air chamber to protect said muiiier against overheating, said means comprising a pipe extending through said 'combustion chamber and a second pipe extending through said mumer.

6. A heater comprising a cylindrical casing having one end adapted to be connected with a source of air supply and a second end connected to one or more spaces requiring heat, means forming a combustion chamber located in said metal mumer located in said tubular heat excasing in spaced relation to the walls thereof, a tubular heat exchanger in said casing, said heat exchanger having one end connected to said combustion chamber and re'ceivinghot products of combustion therefrom, a cylindrical sheet changer and having one end adjacent said com bustion chamber, said mufiler including a muiiiing chamber and means acoustically coupling said source of air supply and a second end connected to one or more spaces requiring heat, means forming, a combustion chamber located in said casing 76 in spaced relation to the walls thereof, a tubular chamber to said heat exchanger and combustion 15 heat exchanger in said casing, said heat exchanger having one end connected to said combustion chamber and receiving hot products oi combustion therefrom, a cylindrical sheet metal muiiier located in said tubular heat exchanger and having one end adjacent said combustion chamber, means for circulating air adjacent said end oi the muiiler to prevent said end from becoming overheated, a carburetor for supplying combustible mixture to said combustion chamber, and means ior conducting said circulated air to said carburetor.

8. A heater of the class described, comprising a casing having one end adapted to be connected to a source of air, means forming a combustion chamber located in said casing, a heat exchanger connected to said combustion chamber and located in said casing and receiving hot products of combustion from said combustion chamber, a muiiler located in said heat exchanger, said mumer including a muflling chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, means providing a conical air chamber interposed between said combustion chamber and said muiiler, and means for creating a circulation of air through said air chamber to prevent overheating of said muiiler.

9. A heater of the class described, comprising a casing having one end adapted to be connected to a source oi air, means forming a combustion chamber located in said casing, a heat exchanger located in said casing and connected to said combusticn chamber, a mufller located in said heat exchanger, said muiiler including a muming chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, said mufller and heat exchanger cooperating to provide passages for hot products assaosv of combustion issuing from said combustion,

chamber, means providing a passageway extending through said combustion chamber and muiiier, means for supplying air to said passageway, said passageway being provided with openings for admitting air to said muiller, and means provided by said muilier for discharging said air into said products of combustion adjacent said combustion chamber.

10. A heater of the class described, comprising a casing having an end adapted to be connected to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger located in said casing and connected to said combustion chamber, a tubular muiller located in said heat exchanger and cooperating therewith to provide passages for hot gases issuing from said combustion chamber, said mufller including a muiiling chamber and meansacoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, means for directing air through the interior of said muh iler, and means for directing a small portion of said air through said muiiler and into said gas passage.

11. A heater of the class described, comprising a casing having one end adapted to be connected to a source of air supply, means'torming a combustion chamber located in said casing, a tubular heat exchanger having one end connected to said combustion chamber and receiving products of combustion therefrom, a pipe extending through said combustion chamber and heat exchanger,

16- means for supplying air to said pipe, a shell surrounding said pipe and cooperating therewith to provide a mulling chamber, said shell cooperating with said heat exchanger to form a passage for said products of combustion, means providing openings connecting said pipe with said chamber, and means providing openings connecting said chamber with said gas passage, said muiiier including a muming chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber ior damping out incipient sound and pressure waves, said two last-named means creating air circulation throughsaidmuiliing chem r 12. A heater or the class described, comprising acasinghavingoneendadsptedtobeconnected to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger having one end connected to said chamber and receiving products of combustion therefrom, a pipe extending through said combustion chamber and heat ex-- changer, a shell surrounding said pipe and cooperating therewith to provide a mulling chamher, said shell cooperating with said heat exchanger to form a passage for said products of combustion, means providing openings connecting said pipe with said chamber, means provid-v ing openings connecting said chamber with said gas passage, said two last-named means creating air circulation through said mulling chamber, a carburetor for supplying combustible mixture to said combustion chamber, and a connection between said pipe and said carburetor.

v 13. A heater 0! the class described, comprising a casing of generally cylindical cross section and having an end adapted to be connected to a source 0! air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger having one end connected to said combustion chamber and receiving hot products of combustion therefrom, a muiiier shell located in said heat exchanger and cooperating therewith to form a gas passage for said products of combustion, said shell having a tapered end adiacent said combustion chamber, a. conduit extending through said combustion chamber and muiiier shell and cooperating therewith to form a casing of generally cylindrical cross section and having an end adapted to be connected to a source or air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger having one end connected to said combustion chamber and receiving hot products of combustion therefrom, a muflier shell located in said heat exchanger and cooperating therewith to form a gas passage for said products 01' combustion, said shell having a tapered end ad- .iacent said combustion chamber, a conduit extending through said combustion chamber and muiiier shell and cooperating therewith to form a muiiiing chamber, a single row of openings connecting said conduit with said mulling chamber, a row of openings in the tapered portion of said muiiler shell connecting said muming chamber with said gas passageway, and two rows of openings in the cylindrical portion of said muiiler shell and connecting said muiiiing chamber with said mps sss m.

15. A hater of the class described, comprising a generally cylindrical casing having an end adapted to be connected to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger connected to said combustion chamber and receiving hot gases therefrom, means providing a passageway extending through said combustion chamber and heat exchanger, means supplying air to said passageway, a mui'fler shell surrounding said pipe and cooperating therewith to form a muiiling chamber, said mufller shell having a tapered end adjacent said combustion chamber, and sound absorbing material located in said muiiling chamber.

16. A heater of the class described, comprising a shell having one end adapted for connection to a source of air supply, means forming a combustion chamber located in said shell and having an end wall, a tubular heat exchanger located in said shell and connected to said combustion chamber, a muiller located in said heat exchanger, said muiiier including a muilling chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, and conduit means supplied with air from said source and extending through said muiiler, combustion chamber and end wall to pass cooling air therethrough to prevent overheating said muiller.

17. A heater of the class described, comprising a tubular casing having one end adapted to be connected to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger having one end connected to said combustion chamber receiving hot gases therefrom, a muiiier located in said heat exchanger, said muiller including a muflling chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, a cup interposed between said combustion chamber and muiller, said cup having a bottom located adjacent said combustion chamber and a top abutting a part of said muilier, said muilier having an extension surrounding said cup in spaced relation thereto, said cup having perforations therein, through said combustion chamber and connected to said extension, means for supplying air to said pipe, and a second pipe extending through said muffler and communicating with the interior of said cup.

18. A heater f the class described, comprising a tubularcasing having one end adapted to be connected to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger connected to said combustion chamber receiving hot gases therefrom, a muiiler located in said heat exchanger, a cup interposed between said combustion chamber and muilier, said cup having a bottom located adjacent said combustion chamber and a top abutting a part of said muiller, said muiiier having an extension surrounding said cup in spaced relation thereto, said cup having perforations therein, a pipe extending through said combustion chamber and connected to said extension, means for supplying air to said pipe, a second pipe extending through said muffler and communicating with the interior of said cup, said mufller having a muilling chamber, and sound absorbing material located in said chamber.

19. A heater of the class described, comprising a pipe extendingatubularcasinghavingoneendadaptedtobe connected to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger connected to said combustion chamber receiving hot gases therefrom, a muilier located in said heat' exchanger, a cup interposed between said combustion chamber and mumer, said cup having a bottom located adjacent said combustion chamber and a top abutting a part ofsaidmumer, said muiiier having an extension surrounding said cup in spaced relation thereto, said cup having perforations therein, a pipe extending through said combustion chamber and connected to said extension, means for supplying air to said pipe, a second pipe extending through said muilier and communicating with the interior of said cup, said munler having a single muilling compartment, and a single row of openings adjacent said cup and connecting said muming chamber with gas passages between said muiller and said heat exchanger.

20. A heater of the class described, comprising a tubular casing having one end adapted to be connected to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger connected to said combustion chamber receiving hot gases therefrom, a muiller located in said heat exchanger, said muiller including a mulling chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, a cup interposed between said combustion chamber and mumer, said cup having a bottom located adjacent said combustion chamber and a top abutting a part of said muiller, said muiller having an extension surrounding said cup in spaced relation thereto, said cup having perforationstherein, a pipe extending through said combustion chamber and connected to said extension, means for supplying air to said pipe, and a second pipe extending through said mufller and communicating with the interior of said cup, said last-named pipe dischar in into said first-named casing.

21. A heater of the class described, comprising a tubular casing having one end adapted to be connected to a source of air supp y. means forming a combustion chamber located in said casing,

' a tubular heat exchanger connected to said combustion chamber receiving hot gases therefrom, a muiller located in said heat exchanger, a cup interposed between said combustion chamber and muiller, said cup having a bottom located adjacent said combustion chamber and a top abutting a part of said muiller, said muiller having an extension surrounding said cup in spaced relation thereto, said cup having perforations therein, a pipe extending through said combustion chamber and connected to said extension, means for supplying air to said pipe. a second pipe extending through said muiller and communicating with the interior of said cup, said last-named pipe discharging into said first-named casing, a carburetor for supplying combustible mixture to said combustion chamber, and an inlet pipe for said carburetor, said inlet pipe communicating with said casing adjacent the end of said heat exchanger remote from said combustion chamber.

22, A heater of the class described, comprising a tubular casing having one end adapted for connection to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger connected to said combustion chamber, a cylindrical muiller located in said heat exchanger and cooperating therewith amass? to form a gas passage for hot products oi combustion from said combustion chamber, said mutfier having a large muming chamber, means for introducing air into the end or said muming chamber which is closest to said combustion chamber, means for discharging air from the other end of said munling chamber, and acoustic coupling means for discharging a small amount of air from the inlet end of said mufliing chamber into said gas passageway and for acoustically coupling said muiiiing chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves.

23. A heater of the class described, comprising a tubular'casing having one end adapted for connection to a source of air supply, means forming a combustion chamber located in said casing, a tubular heat exchanger connected to said combustion chamber, a cylindrical muiiler located in said heat exchanger and cooperating therewith to form a gas passage, said muiiier having a, single large muiiier chamber and means acoustically coupling said chamber to said heat exchanger and combustion chamber for damping out incipient sound and pressure waves, said muiiler having an end adjacent said combustion chamber, said heat exchanger having an and remote from said combustion chamber, means for conducting air from said remote end oi the heat exchanger to said end of the muiliing chamber, and means for discharging air from the opposite end of said muiiiing chamber.

24. A heater oi the class described, comprising a tubular casing having an inlet end and an outlet end, means forming a combustion chamber located in said casing adjacent said inlet end, a tubular heat exchanger located in said casing intermediate the ends thereof and connected to said combustion chamber, a muilier located in a said heat exchanger and cooperating therewith to form a gas passageway for hot products 01' combustion from said combustion chamber, said muiiler having a sound-absorbing chamber and a sheet metal end located adjacent said combustion chamber, a pipe for conducting air from the outlet end of said casing to a point adjacent said muiiier end and discharging said air against said end, and an opening connecting said end of the mumer with said gas passageway, said opening being of such size as to constitute an acoustic coupling between said muiiiing chamber and said heat exchanger and combustion chamber for damping out incipient sound and pressure waves.

25. A heater or the class described, comprising a casing having an inlet end and an outlet end,

means forming a chamber located in saidcasingaheatexchangerlocatedinsaid casing and connected to said combustion chamber, a mufler located in said heat exchanger and having an end adjacent said combustion chamber, said muiller providing a single large acoustic chamber, means for conducting air into said mu!- nln cnamberanditss i t e or said muilier adjacent said combustion chamber, a carburetor for supplying a, combustible mixture to said combustion chamber, and means for conducting air Iran the other end of said combustion chambertosaid carburetor.

26. A heater of the class described, comprising acasinghavinganinletendandanoutletend, means forming a combustion chamber located in said naming. a tubular heat exchanger located in said casing and connected to said combustion chamber, a muiller having a sound-absorbing chamber and one end adjacent said combustion chamber, and means for cooling said muiiier, said means comprising a ripe for conducting air into said mumer, said pipe extending lengthwise oi said muiiler and scharging adjacent said end thereof, penings adjacent said end of the muiller for connecting the interior thereof with said combustion chamber, said openings being of such size as to constitute an acoustic coupling between said sound-absorbing chamber and said heat exchanger and combustion chamber for damping out incipient sound and prasure waves, and an air outlet for the other end 01' said musler.

HENRY J. D! N. HOCOLLUIL REFERENCES CITED 'lheiollowingrelerencesareotreeordinthe flleotthispatent:

UNIT!) STATE PA'IINTB

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