US3628521A - Heater for enclosed spaces - Google Patents

Abstract

A heater for enclosed spaces includes a casing which is easily installed in a cabinet having a rectangular cutout in one wall thereof. The casing houses a removable sealed combustion chamber assembly having a heat fin positioned behind the actual walls which define the combustion chamber, but in heat-conducting and radiant-heat-absorbing relation therewith. An interior heat shield in the casing surrounds the upper portion of the combustion chamber assembly so that the temperature of the outer walls on the casing does not become excessive, thus enabling those walls to be positioned next to wood and other conventional construction material. A removable airdrop is connected to the backwall of the casing for diverting combustion air from an inlet pipe to the inlet duct leading to the combustion chamber. The airdrop also conveys the flue gases into a flue pipe located within the inlet pipe. The flue pipe and inlet pipe connect with a vent cap which projects only a slight distance beyond the outer wall of the enclosed space. The vent cap enables the burner in the combustion chamber to operate under a wide variety of wind velocity conditions, from a slight wind to a high-velocity wind. Thus, the heater is ideally suited for use in over-the-road vehicles such as trailers.

Description

United States Patent ABSTRACT: A heater for enclosed spaces includes a casing which is easily installed in a cabinet having a rectangular cutout in one wall thereof. The casing houses a removable sealed combustion chamber assembly having a heat fin positioned behind the actual walls which define the combustion chamber, but in heat-conducting and radiant-heat-absorbing relation therewith. An interior heat shield in the casing surrounds the upper portion of the combustion chamber assembly so that the temperature of the outer walls on the casing does not become excessive, thus enabling those walls to be positioned next to wood and other conventional construction material. A removable airdrop is connected to the backwall of the casing for diverting combustion air from an inlet pipe to the inlet duct leading to the combustion chamber. The airdrop also conveys the flue gases into a flue pipe located within the inlet pipe. The flue pipe and inlet pipe connect with a vent cap which projects only a slight distance beyond the outer wall of the enclosed space. The vent cap enables the burner in the combustion chamber to operate under a wide variety of wind velocity conditions, from a slight wind to a high-velocity wind. Thus, the heater is ideally suited for use in overthe-road vehicles such as trailers.

[72] inventor RalphR.Hodges Belleville, Ill. [211 App]. No. 15,684 [22] Filed 'Mar.2, 1970 [45] Patented Dec.21, 1971 [73] Assignee Empire Stove Company Belleville, 111.

[ 54] HEATER FOR ENCLOSEDSPACES 16 Claims, 10 Drawing Figs.

[52]U.S.Cl 126/85 B, 126/116 B, 126/307 R [51] 1nt.Cl F24h 3/00, F23j 11/00 [50] Field ofSearch 126/85,85 8,90,91, 110,11013,116,116B,307

[56] References Cited UNITED STATES PATENTS 3,056,397 10/1962Little 126/85 B 2,964,034 12/1960 NordholtetaL. 126/1108 3,410,193 11/1968Clark 126/8513X 2,974,650 3/1961McCorquodale 126/85 BUX 3,136,309 6/1964Martz 126/85 B 3,496,927 2/1970 De Werth eta1 126/85 B 32 [L It? T c e l l, l n gl; 5 "1: u I r- I I 54 l ;l l 66 h H s: Ii i 5,M l ll 185H 34 1/1] 88- .l

92 lfl I 4 jflj l| l r --.u:1.... lT 7; l I l s l= 30 I I PATENTED 0am m SHEET 2 UP 3 3y W H69 M4 M4 m2 HEATER FOR ENCLOSED SPACES BACKGROUND or THE INVENTION This invention relates in general to heaters and more particularly to heaters for enclosed spaces.

Trailers and other recreational vehicles must be equipped with some sort of heating devices in order to be useful the year around. Since most recreational vehicles carry a bottled combustible gas for cooking purposes, it is logical to use the same fuel source for heating the interior of the vehicle also, and heretofore this has been done with limited success.

Vehicular heaters of current construction, however, are quite bulky and consume valuable space within the interior of the vehicle where space is at a premium. This bulkiness is due to a large measure to the desire to isolate the combustion chamber of the heater as much as possible from the surrounding portions of the vehicle in order to reduce the risk of a fire. Moreover, heaters of current construction are difficult to install, and require special brackets and mountings in the vehicle. Once installed they are difficult to service.

Most heaters of current construction which utilize the sealed combustion chamber principle employ an airdrop for supplying combustion air to the lower end of the combustion chamber. These airdrops are positioned vertically and often receive too much heat from the remaining portion of the heater. As a result the combustion air resists downward flow through the airdrop and this adversely affects the efficiency and operation of the burner in the sealed combustion chamber.

I Also many heaters of current construction which employ the sealed combustion chamber principle utilize vent caps which are flush with the exterior of the vehicles. When the wind across these vent caps reaches a critical velocity a blocked vent effect is created, which extinguishes the flame in the combustion chamber. Other vent caps of current construction protrude considerably beyond the outer surface of the vehicle, and while they are not susceptible to the blocked vent effect, they present a hazard for people walking near the vehicle. The projection of this type of end cap also renders the vent cap susceptible to damage as the vehicle is moved.

OBJECTS OF THE INVENTION One of the principal objects of the invention is to provide a highly compact heater for heating enclosed living spaces. Another object is to provide a heater which is easily installed in a simple and compact cabinet constructed from wood or other conventional construction materials. A further object is to provide a heater which is ideally suited for installation in over-the-road vehicles such as trailers, campers, and other recreational vehicles. An additional object is to provide a heater having a sealed combustion chamber and a vet cap which protrudes only a slight distance beyond the exterior surface of the wall on which the vent cap is mounted. Still another object is to provide a heater of the type stated with a vent cap which allows free circulation of air through the heaters combustion chamber, even when the vent cap is subjected to slight or high wind velocities. Yet another object is to provide a heater which is simple in construction and easily serviced. An additional object is to provide a heater of the type stated with an airdrop which does not significantly impede the flow of combustion air to the heater's combustion chamber. These and other objects and advantages will become apparent hereinafter.

SUMMARY OF THE INVENTION The present invention is embodied in a heater including a casing having walls defining a combustion chamber therein. The walls have a fin spaced therefrom, but in heat-conducting relation therewith. The invention is also embodied in a heater having a casing wall on which a removable airdrop is mounted. A heater having a vent cap which for the most part is recessed into a wall also forms part of the invention. The invention also consists in the parts and in the arrangements and combinations of parts hereinafter described and claimed.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the specification and wherein like numerals refer to like parts wherever they occur:

FIG. I is a perspective view of the heater of the present invention mounted in a cabinet shown partially broken away and in section;

FIG. 2 is an exploded perspective view of the heater;

FIG. 3 is a front elevational view showing the interior of the heater casing;

FIG. 4 is a rear elevational view of the heater casing show ing the airdrop mounted thereon;

FIGS. 5 and 6 are sectional views taken along lines 5-5 and 6-6, respectively, of FIG. 3;

FIG. 7 is an elevational view of a vent cap forming part of the present invention;

FIGS. 8 and 9 are sectional views taken along lines 8-8 and 9-9, respectively, of FIG. 7; and

FIG. 10 is a sectional view taken along lines 10-10 of FIG. 3 and showing the expansion clips used to hold the heater casing in the wall.

DETAILED DESCRIPTION Referring now in detail to the drawings, 2 designates a heater which is adapted to warm the air within an enclosed space 4 (FIG. 1) to which the front of the heater 2 is exposed. The enclosed space 4 is bounded on one side by anouter wall 6 having acabinet 8 constructed against it. The heater 2 is installed in and for the most part is enclosed by thecabinet 8. In particular, it is recessed into afront panel 10 ofcabinet 8, thewall 10 having arectangular opening 12 sized for reception of a component of theheater 8. The enclosed space 4 is normally the interior of over-the-road vehicle such as a trailer or other recreational vehicle, but it may also be the room of a building.

The heater 2 includes acasing 14 which slides into the cabinet 8 (FIG. 1) through therectangular opening 12 in thefront panel 10 thereof. Thecasing 14 includes a pair ofsidewalls 16 which are connected across their upper and lower ends by top andbottom walls 18 and 20, (FIG. 5) respectively. At their rear margins the walls l6, l8 and 20 are formed integral with and merge into a backwall 22 (FIG. 4) which extends across and closes the back of thecasing 14. The front of thecasing 14 remains open (FIG. 3) to provide access to the interior thereof.

Thetop wall 18 of thecasing 14 is inclined downwardly at a slight angle to the horizontal and underlies a heat shield 24 (FIGS. 1 and 5) havingside flanges 26 which extend downwardly along and are spot welded to thesidewalls 16. Theheat shield 24 is spaced from the inclinedtop wall 18 and projects horizontally a considerable distance beyond thebackwall 22.

At their forward ends theheat shield 24 and thesidewalls 116 turn outwardly in the formation of mounting flanges 28 (FIGS. 5 and 6) which project beyond the margins of theopening 12 and abut against the exposed face on thefront panel 10 when thecasing 14 is fully inserted in thecabinet 8. Theflanges 28 on thesidewalls 16 haveguide lips 30 projecting forwardly from them, whereas at the upper end of thecasing 14 thetop wall 18 projects forwardly beyond themounting flange 28 of theheat shield 24 and it turns upwardly and then backwardly in the formation of aretention lip 32. The front of thecasing 14 is normally covered by aremovable grill 34, (FIGS. 1 and 2) the upper end of which fits over and engages the retention lip on thetop wall 18. The sides of thegrill 34 turn rearwardly and overlie theguide lips 30 which prevent lateral movement of thegrill 34. The lower end of thegrill 34 also turns rearwardly and is frictionally engaged by a securinglip 35 formed integral with thebottom wall 20 on thecasing 14. Thus, when thecasing 14 is installed in thecabinet 8 the only portion of the heater 2 which is visible from the enclosed space 4 is thegrill 34.

Thecasing 14 is affixed to thecabinet 8 by expansion clips 36 (FIGS. 1 and 10) which are expanded byscrews 38 extending through the mountingflanges 28, on thesidewalls 16. Actually, thescrews 38 collapse the clips 36 (FIG. 10) along the longitudinal axes of thescrews 38 and in so doing expand theclips 36 laterally, causing them to lodge between the sidewalls 16 and the adjacent edges of theopening 12 in thefront panel 10. Thus, the expansion clips 36 both secure thecasing 14 in thecabinet 8 and furthermore space thesidewalls 16 from the edges of theopening 12 in thefront panel 10 so that heat from thewalls 16 is not conducted to thefront panel 10. The expansion clips 36 are more fully described in the application of Ralph R. Hodges, Ser. No. 827,539, filed May 26, I969, and entitled EXPANSION CLIP AND METHOD OF IN- STALLING RECESS FIXTURES WITH SUCI-I CLIPS.

Thecasing 14 further includes an interior heat shield 40 (FIGS. 2, and 6) havingside panels 42 which are spaced inwardly from the sidewalls l6 and at their forward ends turn outwardly where they are spot welded to the front faces of the mountingflanges 28. Theheat shield 40 also includes aback panel 44 and atop panel 46 which are spaced inwardly from thebackwall 22 andtop wall 18, respectively.

Eachside panel 42 has a pair of reinforced tabs 48 (FIGS. 3 and 6) projecting inwardly into the interior of thecasing 14, and thosetabs 48 have acombustion chamber assembly 50 bolted thereto so that thecombustion chamber assembly 50 is in effect suspended within the'interior of thecasing 14. Thecombustion chamber assembly 50 includes (FIGS. 3, 5 and 6) a back wall 52 and afront wall 54 both of which possess a hol lowed-out configuration and are joined together to form acombustion chamber 56. The lower end of thecombustion chamber 56 is closed by acover plate 57 which overlies and is fastened to thewalls 52 and 54 by means ofscrews 58. Access to the interior of thecombustion chamber 56 is gained by removing thescrews 58, and withdrawing thecover plate 57. Thescrews 58 also compress a gasket 59 (FIG. 5) between the overlapping portions of thecover plate 57 and thewalls 52 and 54.

The combustion chamber.assembly 50 further includes a heat fin 60 (FIGS. 2, 5 and 6) which is positioned between theback panel 44 of theinterior heat shield 40 and the back wall 52 of thecombustion chamber 56. At its ends thefin 60 has connectingflanges 62 which extend forwardly and are spot welded to the sides of the backwall 52 so that heat from thecombustion chamber 56 is conducted through theflanges 62 to thefin 60.

Near its lower end the backwall 52 has an inlet duct 64 (FIG. 5) connected to it and that duct opens into thecombustion chamber 56 for delivering combustion air thereto. At its upper end the backwall 52 has adischarge duct 66 connected to it, and that duct likewise opens into thechamber 56 for allowing the products of combustion to escape from thechamber 58. Thus, thecombustion chamber 56 is of the sealed variety.

The duct 64 projects rearwardly beyond theheat fins 60 as well as beyond theback panel 44 of theinterior heat shield 40 and terminates adjacent to but slightly inwardly from thebackwall 22 which is apertured to expose the end of theduct 66 therethrough. Thedischarge duct 66 on the other hand projects completely through and is snugly embraced by theheat fin 66 so that heat from the flue gases in theduct 66 is conducted to theheat fin 60. Beyond theheat fin 60 theduct 66 projects through theback panel 44 of theheat shield 40, and further through thebackwall 22 which is apertured to receive it. Between the ends of theducts 64 and 66 thebackwall 22 is provided witha shallow recess 72 (FIGS. 5 and 6) which opens rearwardly, and appears as an embossment on the opposite or forward side of thewall 22.

Mounted within and extending completely across the lower part of thecombustion chamber 56 is aburner 74, (FIGS. 5 and 6) access to which is gained by removing thecover plate 57 of thecombustion chamber assembly 50. Theburner 74 draws combustion air from within thechamber 56 and is supplied with a combustible gas through a manifold 76 which is connected thereto at its one end and projects through the side of the backwall 52 at its opposite end. Near the center of theburner 74 thecover plate 57 is recessed inwardly and fitted with an inclined mounting plate 78 (FIGS. 3 and 6) through which apilot nozzle 80 and athermocouple junction 82 project. Thepilot nozzle 80 is positioned within thechamber 56 near the gas orifices in theburner 74, while thethermocouple junction 82 is positioned next to thepilot nozzle 80. Immediately above thenozzle 80 thefront wall 54 has an access opening 84 which is normally covered bywindow 86 formed from mica or some other suitable transparent material and anoverlying cover plate 88. Thewindow 86 andplate 88 are held in place bywingnuts 90 which thread overstuds 92 projecting from thefront wall 54.

At its lower end the manifold 76 is threaded into a thermostat regulator 94 (FIGS. 2 and 3) which is in turn connected to an adjoiningcontrol valve 96. The combustible gas is furnished to the heater through agasline 98 which threads into thecontrol valve 96. Thepilot nozzle 80 is connected to thevalve 96 through a gasline 97, and gas will flow through this line only when thethermocouple junction 86 is heated or the solenoid valve to which it is connected is temporarily bypassed in the conventional manner. Thethermostat regulator 94 is of the hydraulically operated variety and includes athermostat bulb 100 which is confined in a pair of mounting tabs 102 (FIGS. 3 and 5) projecting outwardly from thebottom wall 20 of thecasing 14 beneath the securinglip 35. Thethermostat regulator 94 also includes acontrol knob 104 which is exposed through an opening in the lower right-hand comer of thegrill 34.

Turning now to the back of thecasing 14, an airdrop (FIGS. 4-6) is bolted against that portion of thebackwall 22 into which theshallow recess 72 is formed. Theairdrop 110 includes aninner wall 112 which is provided slightly inwardly from its peripheral margin with a shallow recess 114 (FIG. 2) identical in configuration to therecess 72. Therecess 114 however opens toward therecess 72 so that a space (FIG. 5) exists between thewalls 22 and 112 in the area between and slightly beyond the ends of theducts 64 and 66. Indeed, theinner wall 112 only abuts thebackwall 22 along a relatively narrow peripheral rim through which self-tappingscrews 116 extend for securing theairdrop 110 to thebackwall 22 of thecasing 14. Thus, the transfer of heat between the backwall 22 and of theairdrop 110 is minimized by the presence of the opposed recesses 72 and 114. At its lower end theinner wall 112 is provided with a forwardly projecting circular boss 118 (FIGS. 5 and 6) which fits into the lower aperture in thebackwall 22 through which the end of the inlet duct 64 is exposed. The forward end of theboss 118 turns inwardly upon itself in the formation of a circularinternal lip 119 which defines an aperture sized to receive the end of the inlet duct 64 leading into thecombustion chamber 56.

At its upper end theairdrop 110 is fitted with a tapered collar 120 (FIG. 5) having one end flared outwardly and spot welded to theinner wall 112 in alignment with the end of thedischarge duct 66 which it snugly receives.

In addition to theinner wall 112, theairdrop 110 includes anouter wall 122 which for the most part is spaced outwardly from theinner wall 112, but is attached at its sides and ends to the sides and ends of theinner wall 112 so as to form anair supply channel 123 through theairdrop 110. At its upper end theouter wall 124 has an outwardly flaredcircular lip 124 which is spaced radially from and is concentric to the rear end of thecollar 120. Thus, the annular void between thecircular lip 124 and the end of thecollar 120 forms the entrance into theair supply channel 123 within theairdrop 110.

Thecircular lip 124 on theairdrop 110 is tapered slightly and fits snugly into the end of aninlet pipe 126 which extends rearwardly toward theouter wall 6 of the enclosed space 4. Similarly, the end of thecollar 120 fits snugly within aflue pipe 128 and also extends rearwardly through theinlet pipe 126. Both of thepipes 126 and 128 terminate at a vent cap 129 (FIGS. 1, 2 and 7-9) which is recessed into theouter wall 6 of the enclosed space 4.

Thevent cap 129 includes aninlet box 130 which is set into theouter wall 6, and connects with theinlet pipe 126. In particular, theinlet box 130 has a recessed center portion 132 (FIGS. 8 and 9) which is surrounded by a mountingflange 134. Thecenter portion 132 fits into a hole 135 (FIG. 1) formed in thewall 6, whereas theflange 134 projects beyond the margins of thehole 135 and overlies the outer surface of thewall 6. Theflange 134 and likewise theentire inlet box 138 are held to thewall 6 byscrews 136. The recessedportion 132 merges into a taperedcircular lip 138 which projects toward thecasing 14 and fits snugly into the rear end of theinlet pipe 126 just as thecircular lip 124 on theairdrop 1 10 fits into the forward end of theinlet pipe 126.

On the other hand, the rear end of theflue pipe 128 connects with anend cap 140 which also forms part of thevent cap 129 and for the most part is disposed within the recessedportion 132 of theinlet box 130. More specifically, theend cap 140 includes (FIGS. 2, 8 and 9) a pair ofside flanges 142 having mountingtabs 144 which are secured against the mountingflanges 134 of the inlet bybox 130 by thescrews 136. The mountingtabs 144 position theside flanges 142 slightly outwardly from the mounting flange 134 (FIGS. 8 and 9) of the inlet box so that combustion air is free to pass between the two and enter the recessedportion 132 of theinlet box 130. Theside flanges 142 at their inner margins merge into adepressed center portion 146 which extends into the recessedportion 132 of theflue box 130 but is spaced inwardly from the walls thereof so as not to inhibit the flow of combustion air through the recessedportion 132 toward theinlet pipe 126. Thedepressed portion 146 includes across wall 148 which extends through the interior of the recessedportion 132 and at its upper end merges into anoblique wall 150. Theoblique wall 150 in turn merges into atop flange 152 which is positioned coplanar to theside flanges 142 and is likewise disposed outwardly from the mountingflange 134 at the top of theinlet box 130. Thecross wall 148 is centrally provided with atapered collar 154 which projects through thecircular lip 138 of theinlet box 130 and fits snugly into the rear end of theflue pipe 128, just as thecollar 120 fits into the opposite end of thepipe 128. Thecollar 154 projects completely through thecross wall 148 so that the flue gases from thepipe 128 are carried beyond thewall 148 into the confines of thedepressed portion 146.

Outwardly beyond thecross wall 148 thedepressed portion 146 is transversed by a defectingwall 156, the outer surface of which is flush with the side andtop flanges 142 and 152 and furthermore continuous with theside flanges 142. The defectingwall 156 actually consists of two plates spaced about onequarter inch apart with the lower ends of the plates canted inwardly to form aslight lip 158 projecting into thedepressed portion 146. The inner of the two plates deflects the flue gases from theflue pipe 128 generally upwardly toward theoblique wall 150, while the outer of the two plates being spaced from the inner plate remains relatively cool and serves as a protective shield across the inner plate.

The heater 2 is supplied with thecombustion chamber assembly 50 including theburner 74 andvalves 94 and 96 installed in thecasing 14 and theairdrop 110 attached to the back of thecasing 14 and connected with intake anddischarge ducts 64 and 66 on thecombustion chamber assembly 50. Theinlet pipe 126,flue pipe 128,inlet box 130 andend cap 140 are all furnished individually, but in the same packing container.

To install the heater 2, the cabinet 8 (FIG. 1) with therectangular opening 12 in itsfront panel 10 is constructed adjacent theouter wall 6 and an opening is cut in theouter wall 6 at the proper location to receive theinlet box 130 of thevent cap 129. Thereupon, thecasing 14 is inserted into theopening 12 in thecabinet 8 until the mountingflanges 28 abut against the outer face of thefront panel 10. At that time thescrews 38 are tightened, causing (H0. 16) the expansion clips 36 to expand laterally and lodge between the edges of theopening 12 and thesidewalls 16 on thecasing 14. This secures thecasing 14 firmly in thecabinet 8 and furthermore spaces itssidewalls 16 from the margins of theopening 12.

With the casing secured in thecabinet 8, the inlet andflue pipes 126 and 128 are cut to the proper length and then installed on thecircular lip 124 andcollar 120, respectively, of the airdrop through the opening cut in theouter wall 6. Next thecircular lip 138 and theinlet box 130 is fitted into the rearmost end of theinlet pipe 126, and theinlet box 138 is secured against thewall 6 by driving at least onescrew 136 through its mountingflange 134 at a location thereon which is not normally covered by theflanges 142 and 152 on theend cap 140. Thescrew 136 of course threads into theouter wall 6 and thereby holds the inlet box 1311 temporarily in place. Theinlet box 138 should be installed such that theinlet pipe 126 is pitched downwardly toward it at a slight angle so that any moisture which finds its way into thepipe 126 will drain toward theinlet box 130 and not into theairdrop 118.

Once theinlet box 130 is temporarily set in place in thewall 6, thecollar 154 on theend cap 140 is fitted into the rearmost end of theflue pipe 128, in which case thedepressed portion 146 will be disposed within the recessedportion 132 of theinlet box 130. Thereafter the remainingscrews 136 are passed through the mountingtabs 144 on theend cap 140 and the underlying mountingflange 134 on theinlet box 138 and are driven into thewall 6 so as to permanently secure thevent cap 129 as well as thepipes 126 and 128 permanently in place. Since theinlet pipe 126 slopes away from theairdrop 118, so will theflue pipe 128 and water will not drain intocombustion chamber 56.

To light the heater 2, thewindow 86 andcover plate 88 are lifted away from the access opening 84 and thecontrol valve 96 is set to override thethermocouple junction 82 and direct the combustible gas through the line 99 to thepilot nozzle 80. Thereupon, the burning head of a lighted match is inserted through the access opening 84, and since thatopening 84 is positioned directly above thepilot nozzle 88, the gas from thenozzle 88 will ignite. The flange at thepilot nozzle 88, heats thethermocouple junction 82, and once that junction reaches the prescribed temperature the pilot flame remains selfsustaining.

After the pilot is lit thecontrol valve 96 is set so that gas is directed to thethermostat regulator 94 which in turn discharges the gas into themanifold 76. From the manifold 76 the gas enters theburner 74 where it is mixed with combustion air from the lower end of thecombustion chamber 56, forming a combustible mixture which is discharged upwardly through the orifices in theburner 74. The combustible mixture is, of course, ignited by the flame at thepilot nozzle 88, creating a flame along the entire length of theburner 74 andcombustion chamber 56. This flame sets up convention currents in thecombustion chamber 56 and heats the baclt andfront walls 52 and 54 of thecombustion chamber assembly 50.

The heated products of combustion rise through thecombustion chamber 56 and induce convention currents therein. At the upper end of thechamber 56 the products of combustion enter thedischarge duct 66 and flow into theflue pipe 128 after passing through the collar 1211 at the upper end of theairdrop 110. Theflue pipe 128 discharges the products of combustion against the deflectingwall 156 of theend cap 148 which directs it upwardly through thedepressed portion 146 of theend cap 140. The rising flue gases pass along theoblique wall 150 in theend cap 140, at the end of which they leave thevent cap 129 and are vented to the atmosphere.

The convection currents induced by the flame at theburner 74 draw fresh combustion air into the bottom of thecombustion chamber 56 through the inlet duct 64 which is connected to theair supply channel 123 in theairdrop 118. Thesupply channel 123 in turn receives air from theinlet pipe 126 which is connected to the recessedportion 132 of theinlet box 130. The combustionair enters the recessedportion 132 of theinlet box 130 below thelip 158 on theend cap 140 and between theflanges 142 and 152 on theend cap 140 and the underlying mountingflanges 134 on theinlet box 130.

The flow of combustion air into theinlet box 130 andinlet pipe 126 and the flow of flue gases out of theflue pipe 128 andend cap 140 remains continuous even when wind exists across theouter wall 6, and no blocked vent effect occurs irrespective of whether the wind velocity is slight or great. The flow through thecombustion chamber 58 remains unaffected by the wind velocity across theinlet box 130 andend cap 140 due to the balance bias created by locating theend cap 140 in a turbulent area next to thewall 6 and by allowing ample relief areas between theflanges 142 and 152 on one hand and the mountingflange 134 on the other. This enables wind or turbulent air to enter theinlet'box 130 and create a pressure differential across thecombustion chamber 56.

In a balanced vent system such as a true flush vent or an extended concentric vent, the only force available to move air into the air inlet and out the flue outlet is the heat developed by the burner. This creates a very slight negative pressure in the flue outlet and a very slight positive pressure in the air inlet. When a balanced vent operates in wind conditions it does not maintain perfect balance but swings across zero, allowing flue outlet pressures and inversely inlet pressures to fluctuate very slightly positive or negative. A slight positive pressure in the flue outlet can overpower the slight negative pressure due to burner heat and thus cause a blocked flue condition, and this will result in a burner outage. Thevent cap 129 avoids the blocked flue condition due to the form and location of air inlet apertures and flue outlet apertures which allows the flue outlet pressure to swing from zero to slightly negative and the air inlet pressure inversely to swing from zero to slightly positive with neither being able to cross the zero line. This effectively prevents a reversed or blocked airflow condition which could cause outage.

Thus, thevent cap 129 avoids the blocked vent effect associated with conventional flush-type vent caps when they are subjected to gentle winds. Thevent cap 129 is therefore ideally suited for use on trailers and other recreational vehicles designed for over-the-road use.

Since thevent cap 129 projects only'a very short distance beyond the;outer surface of thewall 6 it does not present a hazard to one walking close to thewall 6. This is in contrast to many conventional vent caps which project considerably beyond the wall into which they are fitted. The double plate construction of the deflectingwall 156 in theend cap 140 prevents that exposed surface from reaching high temperatures, and accordingly the risk of someone being burned by theend cap 129. is minimized.

The flue gases, of course, heat theflue pipe 128 into a relatively high temperature, but that pipe is disposed entirely within and completely shielded by theinlet pipe 126 so that no fire hazard exists. Theupper heat shield 24 which extends partially over thepipes 126 and 128 further reduces the danger.

By reason of the opposed recesses 72 and 114 on theback wall 22 of thecasing 14 and on theinner wall 112 of theairdrop 110, respectively, theairdrop 110 for the most part is spaced away from thebackwall 22 of thecasing 14. This insulates theairdrop 110 from thebackwall 22 so that the air within it remains relatively cool and at a constant temperature. Consequently, it has little tendency to resist the normal conventive flow and flow downwardly into the inlet duct 64 leading to thecombustion chamber 56.

Turning now to the interior of thecasing 14, the back and frontheated walls 52 and 54 of thecombustion chamber assembly 50 heat the air surrounding them and causes that air to rise, thereby inducing convection currents through thecasing 14. The heated air rising from thewalls 52 and 54 is deflected forwardly and out of thecasing 14 by the inclinedtop wall 18. Since theheat fin 60 is connected to the backwall 52 by the connectingflanges 62 at the ends thereof, considerable heat is conducted to it through theflanges 62. More heat is conducted from thedischarge duct 66 to thefin 60 at the location where thefin 60 embraces theduct 66. Theheat fin 60 receives still more heat by way of radiation from the heated backwall 52. inasmuch as thetin 60 extends vertically through the casing and is exposed on both sides to the airstream induced through thecasing 14, it dissipates heat into that airstream and enhances the efficiency of the heater 2.

Theside panels 42 and backpanel 44 of theinterior heat shield 40, being respectively spaced from thesidewalls 16 and backwall 22 of thecasing 14, are also exposed on both faces to the airstream passing through thecasing 14 and further serve to impart heat to that airstream and increase the efficiency of the heat 2 thereby. In this connection, it should be noted that the front ends of thetop wall 22 andtop panel 46 in thecasing 14 are spaced apart at their forward ends so that the heated air between them discharges into the enclosed space 4 through thedrill 34. Thepanels 42, 44 and 46 on theheat shield 40 receive heat primarily by radiation and by reason of this fact they shield those portions ofouter walls 16, 18 and 22 which would normally be exposed to the heat of the backwall 52 on thecombustion chamber assembly 50. Consequently, thesidewall 16,bottom wall 20, and backwall 22 which form the outwardly presented surface of the casing do not reach high temperatures and can be used against wood and other conventional construction materials without danger. Theupper heat shield 24 provides additional protection across the top of thecasing 14 and does not reach high temperatures either. Therefore, it too can be used against wood and most other construction materials.

Access to the interior of thecasing 14 is gained by merely pulling the lower end of the grill away from the securinglip 35 on thebottom wall 20 and then lifting it upwardly off of theretention lip 32 on thetop wall 18. The entirecombustion chamber assembly 50 is positioned in thecasing 14 by only four screws at thetabs 48 and can be easily withdrawn from thecasing 14 by removing those screws. Removal of thecover plate 57 on thecombustion chamber assembly 50 affords access to the lower end of thecombustion chamber 56 for servicing theburner 74 or the pilot nozzle andthermocouple junction 82. Thus, the heater 2 is easily serviced.

If the natural convection through thecasing 14 does not supply enough heated air, a blower may be mounted on thebottom wall 20 beneath thecombustion chamber assembly 50 and opposite to thevalve 96. Such a blower should be oriented to force air upwardly between the backwall 52 theheat fin 60 of thecombustion chamber assembly 50.

This invention is intended to cover all changes and modifications of the example of the invention herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

l. A heater comprising a casing including a pair of sidewalls, a backwall, a top wall, and an interior heat shield, the heat shield having side panels spaced inwardly from the sidewalls, a back panel spaced inwardly from the backwall, and a top panel spaced inwardly from the top wall; combustion chamber walls mounted in the casing and attached to the interior heat shield, the combustion chamber walls defining a sealed combustion chamber; a burner in the combustion chamber; inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air thereto and exhausting flue gases therefrom; and a fin mounted in the casing in outwardly spaced relation to at least one of the combustion chamber walls, the tin being in heat-conducting relation with respect to the combustion chamber walls so that the heat generated in the combustion chamber is transferred to the fin. whereby air circulating through the casing will be heated by the combustion chamber walls and the tin.

2. A heater according toclaim 1 wherein the tin has a flange along at least one of its margins, the flange being connected to the one of the combustion chamber walls for conducting heat to the fin.

3. A heater according toclaim 1 wherein the side panels of the interior heat shield are provided with inwardly projecting mounting tabs and the combustion chamber walls are detachably connected to the tabs.

4. A heater according toclaim 1 wherein the top and backwalls of the casing are connected; wherein the top and baclt panels of the interior heat shield are connected; wherein a continuous channel exists between the back and top walls and the back and top panels so'that the heat from the combustion chamber will induce air to flow through the channel and be discharged between the forward ends of the top wall and top panel.

5. A heater according to claim 4 wherein the top wall and top panel are inclined downwardly toward the backwall and panel so that the heated air will be deflected out of the front of the casing.

6. A heater comprising a casing having a wall provided with a shallow recess; combustion chamber walls defining a sealed combustion chamber in the casing; a burner in the combustion chamber; inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air to and for exhausting the products of combustion from the combustion chamber; and an airdrop detachably connected to the casing wall, the airdrop defining an air supply channel and including an inner wall presented adjacent to the outer surface of the casing wall and having a shallow recess positioned opposite the shallow recess in the casing wall such that the casing wall and the inner wall are for the most part spaced apart to minimize transfer of heat from the casing to air within the airdrop, an outer wall, a collar which extends through the air supply channel and engages the discharge duct leading from the combustion chamber, an inlet port formed in the outer wall and exposing the collar, and an outlet port formed in the inner wall below the inlet port and engaged with the inlet duct leading to the combustion chamber.

7. A heater comprising a casing having a wall, combustion chamber walls defining a sealed combustion chamber in the casing, a burner in the combustion chamber, inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air to and for exhausting the products of combustion from the combustion chamber, an airdrop detachably connected to the casing wall, the airdrop defining an air supply channel and including an inner wall presented adjacent to the casing wall, an outer wall, a collar extending through the air supply channel and engaged with the discharge duct leading from the combustion chamber, a inlet port formed in the outer wall and exposing the collar, and an outlet port formed in the inner wall below the inlet port, and comprising an embossment extending outwardly from the inner wall and through the casing wall, and an inwardly turned lip at the outer end of the embossment, the lip defining an aperture which snugly receives the inlet duct leading to the combustion chamber.

8. A heater according to claim 7 and further characterized by an inlet pipe connected with the inlet port on the airdrop, a flue pipe connected with the collar and disposed within inlet pipe, and a vent cap connected to the ends of the flue and inlet pipes for introducing fresh air into the inlet pipe and for exhausting the products of combustion from the flue pipe.

9. A heater for heating an enclosed space defined in part by an outer wall, said heater comprising a casing, means defining sealed combustion chamber in the casing, supply and discharge conducts leading to and from the combustion chamber for supplying combustion air to and exhausting the products of combustion from the combustion chamber, the portion of the discharge conduct located remote from the combustion chamber extending through the outer wall and being disposed within the supply conduct, and a vent cap mounted in the outer wall for introducing combustion air into the supply conduct and for exhausting the products of combustion from the discharge conduct, the vent cap comprising lllll an inlet box recessed into the outer wall and forming a cavity which opens outwardly from the wall and is exposed to the atmosphere, the inner end of the inlet box being connected with the supply conduit so that air for combustion is drawn into the supply conduit from the inlet box, an end cap disposed within the inlet box cavity and having walls spaced from the surfaces defining the cavity of the inlet box, the end cap being connected with the discharge conduit at its inner end and opening outwardly into the atmosphere at its outer end so that the products of combustion from the discharge duct are discharged into the atmosphere through the end cap, walls of the end cap projecting outwardly slightly beyond the outer margins of the inlet box cavity, the end cap further having flanges connected to the outwardly projecting walls thereof, the flanges extending laterally beyond the margins of the inlet box cavity and being spaced outwardly from those margins so that air for combustion can enter the inlet box cavity from behind the end cap flanges.

10. A heater according to claim wherein the end cap further comprises a deflecting wall extending between two of the walls thereof which project beyond the margins of the inlet box cavity and being spaced outwardly from the discharge conduct so that the flue gases are deflected away from the incoming combustion air.

11. A heater according to claim 10 wherein the end cap opens upwardly but not laterally whereby the flue gases are exhausted upwardly.

12. A heater according to claim 111 wherein one of the walls of the end cap is a cross wall which extends through the cavity of the inlet box behind the deflecting wall, and another is an oblique wall connected to the cross wall and terminating above and in spaced relation to the upper margin of the deflecting wall.

113. A heater according to claim lll wherein the inlet box includes a mounting flange which surrounds the cavity and overlies the outer surface of the outer wall, wherein the flanges of the end cap are located at the sides thereof and are spaced outwardly from the mounting flanges, whereby combustion air can enter the cavity between the end cap flanges and mounting flanges.

M. A heater according to claim 13 wherein one of the walls of the end cap is a cross wall extending across the cavity of the inlet box behind the deflecting wall and another is an oblique wall connected to the cross wall and terminating above and in spaced relation to the upper margin of the deflecting wall; and wherein the oblique wall is connected to a top flange which is located in outwardly spaced relation to the mounting flange on the inlet box.

15. A heater comprising a casing having a backwall and sidewalls projecting away from the backwall, a combustion chamber wall mounted in the casing and defining a sealed combustion chamber, the combustion chamber walls being presented opposite to and spaced outwardly from the casing backwall and the casing being unobstructed at the top and bottom of the combustion chamber wall so that air flows between the bacltwall and the combustion chamber wall, an inlet duct connected to the combustion chamber wall near the lower end of the combustion chamber and communicating with the combustion chamber for admitting air to the com bustion chamber, an outlet duct connected to the combustion chamber wall near the upper end of the combustion chamber and communicating with the combustion chamber for exhausting the products of combustion from the combustion chamber, the inlet and outlet ducts projecting through the backwall in vertically spaced relation to one another with the outlet duct being positioned above the inlet duct, a tin interposed between and spaced from both the casing back wall and the combustion chamber wall, and connecting flanges extending between the fin and the combustion chamber wall so that heat from the combustion chamber is conducted through the connecting flanges to the tin, the connecting flanges being spaced inwardly from the casing sidewall, whereby air circulating through the casing will be heated by the combustio chamber wall and the tin.

3 62 8 2 1 11 16. A heater according to claim 21 wherein the discharge duct extends through and is embraced by the fin whereby the heat from the flue gases is transferred to the fin.

* i i i UNHED STATES PATENT @FEFMZE QERTH MATE @F RRE CMN Patent No. 3,628,521 Dated December 21, 197].

Inventor(s) Ralph R. Hodges It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1,, line 53, "vet" should be "vent",

Col. 8,line 18, "drill" should be "grill'H.

C01. 11,line 1, "21" should be "15".,

Signed and sealed this 30th day of January 1973.,

(SEAL) Attest:

,EDWARD MWFLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM P0-1050 (10-69) USCOMM-DC scam-ps9 US. GOVERNMENT PRINTING OFFICE: I965 0-3fi6-334

Claims (16)

1. A heater comprising a casing including a pair of sidewalls, a backwall, a top wall, and an interior heat shield, the heat shield having side panels spaced inwardly from the sidewalls, a back panel spaced inwardly from the backwall, and a top panel spaced inwardly from the top wall; combustion chamber walls mounted in the casing and attached to the interior heat shield, the combustion chamber walls defining a sealed combustion chamber; a burner in the combustion chamber; inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air thereto and exhausting flue gases therefrom; and a fin mounted in the casing in outwardly spaced relation to at least one of the combustion chamber walls, the fin being in heat-conducting relation with respect to the combustion chamber walls so that the heat generated in the combustion chamber is transferred to the fin, whereby air circulating through the casing will be heated by the combustion chamber walls and the fin.

2. A heater according to claim 1 wherein the fin has a flange along at least one of its margins, the flange being connected to the one of the combustion chamber walls for conducting heat to the fin.

3. A heater according to claim 1 wherein the side panels of the interior heat shield are provided with inwardly projecting mounting tabs and the combustion chamber walls are detachably connected to the tabs.

4. A heater according to claim 1 wherein the top and backwalls of the casing are connected; wherein the top and back panels of the interior heat shield are connected; wherein a continuous channel exists between the back and top walls and the back and top panels so that the heat from the combustion chamber will induce aIr to flow through the channel and be discharged between the forward ends of the top wall and top panel.

5. A heater according to claim 4 wherein the top wall and top panel are inclined downwardly toward the backwall and panel so that the heated air will be deflected out of the front of the casing.

6. A heater comprising a casing having a wall provided with a shallow recess; combustion chamber walls defining a sealed combustion chamber in the casing; a burner in the combustion chamber; inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air to and for exhausting the products of combustion from the combustion chamber; and an airdrop detachably connected to the casing wall, the airdrop defining an air supply channel and including an inner wall presented adjacent to the outer surface of the casing wall and having a shallow recess positioned opposite the shallow recess in the casing wall such that the casing wall and the inner wall are for the most part spaced apart to minimize transfer of heat from the casing to air within the airdrop, an outer wall, a collar which extends through the air supply channel and engages the discharge duct leading from the combustion chamber, an inlet port formed in the outer wall and exposing the collar, and an outlet port formed in the inner wall below the inlet port and engaged with the inlet duct leading to the combustion chamber.

7. A heater comprising a casing having a wall, combustion chamber walls defining a sealed combustion chamber in the casing, a burner in the combustion chamber, inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air to and for exhausting the products of combustion from the combustion chamber, an airdrop detachably connected to the casing wall, the airdrop defining an air supply channel and including an inner wall presented adjacent to the casing wall, an outer wall, a collar extending through the air supply channel and engaged with the discharge duct leading from the combustion chamber, a inlet port formed in the outer wall and exposing the collar, and an outlet port formed in the inner wall below the inlet port, and comprising an embossment extending outwardly from the inner wall and through the casing wall, and an inwardly turned lip at the outer end of the embossment, the lip defining an aperture which snugly receives the inlet duct leading to the combustion chamber.

8. A heater according to claim 7 and further characterized by an inlet pipe connected with the inlet port on the airdrop, a flue pipe connected with the collar and disposed within inlet pipe, and a vent cap connected to the ends of the flue and inlet pipes for introducing fresh air into the inlet pipe and for exhausting the products of combustion from the flue pipe.

9. A heater for heating an enclosed space defined in part by an outer wall, said heater comprising a casing, means defining sealed combustion chamber in the casing, supply and discharge conducts leading to and from the combustion chamber for supplying combustion air to and exhausting the products of combustion from the combustion chamber, the portion of the discharge conduct located remote from the combustion chamber extending through the outer wall and being disposed within the supply conduct, and a vent cap mounted in the outer wall for introducing combustion air into the supply conduct and for exhausting the products of combustion from the discharge conduct, the vent cap comprising an inlet box recessed into the outer wall and forming a cavity which opens outwardly from the wall and is exposed to the atmosphere, the inner end of the inlet box being connected with the supply conduit so that air for combustion is drawn into the supply conduit from the inlet box, an end cap disposed within the inlet box cavity and having walls spaced from the surfaces defining the cavity of the inlet box, the End cap being connected with the discharge conduit at its inner end and opening outwardly into the atmosphere at its outer end so that the products of combustion from the discharge duct are discharged into the atmosphere through the end cap, walls of the end cap projecting outwardly slightly beyond the outer margins of the inlet box cavity, the end cap further having flanges connected to the outwardly projecting walls thereof, the flanges extending laterally beyond the margins of the inlet box cavity and being spaced outwardly from those margins so that air for combustion can enter the inlet box cavity from behind the end cap flanges.

10. A heater according to claim 9 wherein the end cap further comprises a deflecting wall extending between two of the walls thereof which project beyond the margins of the inlet box cavity and being spaced outwardly from the discharge conduct so that the flue gases are deflected away from the incoming combustion air.

11. A heater according to claim 10 wherein the end cap opens upwardly but not laterally whereby the flue gases are exhausted upwardly.

12. A heater according to claim 11 wherein one of the walls of the end cap is a cross wall which extends through the cavity of the inlet box behind the deflecting wall, and another is an oblique wall connected to the cross wall and terminating above and in spaced relation to the upper margin of the deflecting wall.

13. A heater according to claim 11 wherein the inlet box includes a mounting flange which surrounds the cavity and overlies the outer surface of the outer wall, wherein the flanges of the end cap are located at the sides thereof and are spaced outwardly from the mounting flanges, whereby combustion air can enter the cavity between the end cap flanges and mounting flanges.

14. A heater according to claim 13 wherein one of the walls of the end cap is a cross wall extending across the cavity of the inlet box behind the deflecting wall and another is an oblique wall connected to the cross wall and terminating above and in spaced relation to the upper margin of the deflecting wall; and wherein the oblique wall is connected to a top flange which is located in outwardly spaced relation to the mounting flange on the inlet box.

15. A heater comprising a casing having a backwall and sidewalls projecting away from the backwall, a combustion chamber wall mounted in the casing and defining a sealed combustion chamber, the combustion chamber walls being presented opposite to and spaced outwardly from the casing backwall and the casing being unobstructed at the top and bottom of the combustion chamber wall so that air flows between the backwall and the combustion chamber wall, an inlet duct connected to the combustion chamber wall near the lower end of the combustion chamber and communicating with the combustion chamber for admitting air to the combustion chamber, an outlet duct connected to the combustion chamber wall near the upper end of the combustion chamber and communicating with the combustion chamber for exhausting the products of combustion from the combustion chamber, the inlet and outlet ducts projecting through the backwall in vertically spaced relation to one another with the outlet duct being positioned above the inlet duct, a fin interposed between and spaced from both the casing back wall and the combustion chamber wall, and connecting flanges extending between the fin and the combustion chamber wall so that heat from the combustion chamber is conducted through the connecting flanges to the fin, the connecting flanges being spaced inwardly from the casing sidewall, whereby air circulating through the casing will be heated by the combustion chamber wall and the fin.

16. A heater according to claim 21 wherein the discharge duct extends through and is embraced by the fin whereby the heat from the flue gases is transferred to the fin.

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