US 3274989 A
Description (OCR text may contain errors)
Sept. 27, 1966 K. s. JENSON ETAL AIR HEATER 4 Sheets-Sheet 1 Filed Dec. 31, 1965 1 MOW U 7);
s gll p 27, 1 K. s. JENSON ETAL 3,274,989
AIR HEATER 4 Sheets-Sheet 2 Filed Dec. 31, 1963 Sept. 27, 1966 K. s. JENSON ETAL 3,274,989
AIR HEATER Filed Dec. 31, 1963 4 Sheets-Sheet 5 ja /Q Sept. 27,1966
K. S. JENSON ETAL AIR HEATER 4 Sheets-Sheet 4,
Filed Dec. 31, 1963 United States Patent 3,274,989 AIR HEATER Kenneth S. Jensen and Frederick W. Suhr, Wisconsin Rapids, Wis., wsignors to Preway, Inc., a corporation of Wisconsin Filed Dec. 31, 1963, Ser. No. 334,693 Claims. (Cl. 126-110) This invention relates to air heaters and especially air heaters for heating air within a building or room thereof.
Air heaters of the type installed and used within living areas of dwellings have in recent years come more and more into use. Such heaters include space heaters as well as heaters for heating the entire dwelling. These heaters are often constructed with attractive exterior designs because they may be installed directly in living quarters rather than in a cellar space or other isolated space. However, because of the heating function of the air heater, often a hot surface is provided in the heater which may constitute a hazard when the heater is installed and used in living quarters. Inadvertent contact with such a hot wall may result in a severe burn or discomfort.
Further, such an air heater is conveniently installed with an outlet through a wall or ceiling structure. Additional hazards may be created by leakage of vent ducts. Also, where a burner is employed for heating purposes, the efliciency of the heater may be decreased by flow of exhausted gases back into the burner intake.
The heat within the air heater structure may also damage electrical control systems or the like. Often it is difiicult to gain access to internal working parts and the electrical system for servicing, especially where a separate flow system is provided for the combustion gases and air is circulated in heat exchange therewith for absorbing heat. Further, overly complex mechanisms are often employed for directing heat from the air heater to a particular chosen area of a room or building by deflectors or the like.
It is a general object of this invention to provide new and useful improvements in air heaters which may be installed within living quarters. Particularly, it is also an object of this invention to overcome or alleviate problems such as those discussed above.
It is a more partioularobject of this invention in one aspect thereof to provide a household air heater with an outer casing wall insulated from the internal heat by a flowing blanket of air.
Still another object is to provide a new and useful air heater of the type operated by flowing air in heat exchange withcombustion gases in a separate flow system wherein all parts of both flow systems are easily and conveniently available for servicing or the like.
FIGURE 1 is a perspective view of a form of air heater of this invention;
FIGURE 2 is a view looking into the air heater of FIGURE 1 with the front door removed;
FIGURE 3 is a section through the air heater of FIGURE 1 along lines 3-3 of FIGURE 2, with the air heater mounted on and supported by a wall of a building; and
FIGURE 4 is a view of a portion of the rear of the air heater of FIGURE 1 showing a form of venting arrange'ment; and
3,274,989 Patented Sept. 27, 1966 FIGURE 5 is a side view and partial section of the air heater of FIGURES 1-3 with another form of venting arrangement for use with a chimney.
In general, the embodiment of air heater illustrated in the drawings is of the type in which air is drawn in from a room or building to be heated and the air is passed in heat exchange with a combustion chamber wherein fuel is being burned. The heated air is then discharged back to the room or building and air is continuously passed through the heater while on, for heating purposes. The air for supplying the burner is drawn in through a separate intake system from outside of the room or building and the combustion gases and fumes are exhausted exteriorly of the room or building.
Referring to the drawings, as seen generally in FIGURE 1, the embodiment illustrated includes a hexahedral casing having outer walls on each of the six sides thereof. As seen in FIGURES 1-3, the outer side walls 12 and 13 and top wall 14 are formed of a single sheet member 15 and have inwardly turned flanges 16 overlapping and abut' ting peripheral edges of an outer sheet member 19 of a rear wall 20. The front edge of sheet 15 is folded inwardly within the casing at 21 and, thence downwardly in an inward flange 22 providing a recess flange or angle member 23, the purpose for which will be seen hereinbelow. Flange 22 forms one leg of the angle member 23, the other leg terminating at fold 21. The rear wall 20 includes sheet member 19 and an internal sheet support member 24 'facially secured thereto and terminating at its upper end in a channel-like configuration at 25 for adding rigidity to the upper rear edge of the casing.
The bottom wall 26 of the casing includes a bottom sheet 29 abutting inwardly turned flanges 30 of sheet member 15. Sheet 29 is backed with an inner sheet 31 and secured thereto, sheet 31 having a rearward channellike portion 32 which is secured by one channel leg to sheet 24. A rear flange 33 of sheet 29 turns upward overlying sheet 19 of rear wall 20, sheet 19 being backed by brace or sheet member 24 which is secured to both flange 33 and sheet 19. Inner sheet 31 is secured to the upper faces of flanges 30 and backs the abutting joint between flanges 30 and sheet 29.
The front edge of sheet 29 also terminates in a recessed angle portion 23, the bend at 21 clam-ping and holding the front edge of sheet 31 between the opposing surfaces of sheet 29. in forming the angle 23.
A second casing Wall structure is provided generally enclosing a combustion and air heating portion 34 of the illustrated air heater, except for the air intake and outlet passages thereof. The second casing wall structure is spaced inwardly from the outer casing structure to define a flow path 35 between the inner and outer casing structures in communication with an air intake chamber 36 for delivery of air to the heater from the room to be heated by the heater. The flow path 35 insulates outer casing top wall 14, rear wall 22, bottom wall 29, and side wall 12 from the combustion and air heating portion 34 of the device so that these walls remain cooler than otherwise. End 13 and the front of the illustrated air heater include air inlets and outlets, respectively, for circulating air through the heater and are not provided with the insulating air flow path, is. not backed by the inwardly spaced inner casing.
The inner casing, indicated generally at 39, is composed of a plurality of sheet members secured together by overlapping flanged edges to form an enclosure. spaced inpurposes.
rest on or be welded to channel member 32. Channel members 25 and 32 extend the length of the rear wall 19, blocking air communication between the portion of passage 35 along wall 19 andthe portion ofpassage 35 along top wall 14 and bottom wall 29.
Casing 39, it will be noted, is open at the end dis posed toward end 13 of the outer casing of the device.
A sheet metal member 42 is configurated to .definean air chamber 44 and has down-turned or inwardly turned flanges 43 along the front and rear edges thereof. Rear flanges 43 are secured to the interior surface of the rear wall of casing 39. Air chamber 44 is the intake chamber for receiving air to be used by a burner 45 mounted by suitable means within chamber 44. Burner 45 is illustrated in the form of an automatic gun-type? power burner, a type of burner used in central heating plants. Such a burner is electrically controlled for ignition and shut-off and is capable of drawing surrounding air and creating suflicient power draft for burning of the fuel, in this case, oil. The oil is; introduced to' the burner in normal manner by feed lines (not shown), flame and combustion gases being discharged from burner 45 through outlet passage 46 into a pot portion 49 of a furnace 50.
defining a combustion chamber internally thereof. Furnace 50 is provided with a service port c'over 51 bolted in place .as at 52. The combustion gases from combustion chamber 50 are passed through an outlet duct orfpassage 53 terminating in tubular projectionr54 for exhausting such' combustion gases from the device. Force for draft at the burner and for exhausting the gases'is provided integrally in the burner structure.
Upstanding from sheet 42 is a sheet member 55 extend mg the depth of the air heater casing, and, with sheet'42 t and casing 39 defining air intake chamber 36 to the left thereof, as viewed in FIGURE 2, asa chamber separate from the air heating chamber 34. The sheet is secured,
along its top edge to flange 56 projecting downward from the portion of casing 39 spaced inwardly from wall 14.
The lower edge of sheet 55 is secured by'flange 59 to sheet- 42 and the rear edge is secured to the rear wall of casing 39. An opening 60 is provided through sheet 55 surrounded by a skirt 61 defininga throat opening 61 extending inwardly into chamber 34; Mounted within the throat member 61, coaxial therewith, is a blower or fan having a plurality of blade members 62 driven by a motor 63 suitably mounted in chamber 36 by brackets (not shown).
The front wall of the illustrated air heater device is shown generally by reference numeral 64; Vertical and.
horizontal brace members'65, each having a cross-sectional T-shape, are interconnected across the front of the casing and are secured at their ends to each other or to angle legs 22, "providing. continuation of the recessed channel members 25 and,=32 from communication with,
flange or leg 22 vertically spanning the front and horizontally spanning a portion of the front, forming a frame structure of front wall 64. A'door 69 is mounted by hinges 70 to the rearward folded portion of wall- 13 ad jacent fold 21. Door 69 is provided with a handle 71 and is openable and closable on hinges 70. Door'69 is provided with a snap-catch (not shown) of conventional design for securing the door in closed position, but releasable for opening the door. The inner surface of door 69, when door 69 is closed, is flush against and abuts angle 43 and the forward edge of plate 55 to generally seal chamber 36 from chamber 34 except-via port 60. The inner surface of door 69 also seals olf and'forms the front wall of combustion air chamber 44, preventing use of appreciable amounts of room air for combustion and may include insulation between the two walls, if desired. Door 69 is provided for gaining access to the Door 69 may conveniently be double-walled mounted on a Wall of the room. Box or electrical system I 68 is mounted on wall 42a in chamber 44 and isthereby isolated from the hotter chamber 34;-also,' sheet member 42, of which wall 42a is a portion blocks substantial .heat exchange between the outlet chamber 53 from furnace 59 and the electrical system. With door 69 closed the peripheral, edges thereof arefacially disposed against flanges 22 and an arm of T-frame member 65. Thus, door 69 is used to close and substantially seal a plurality of chambers from each other without employing permanent seals of compositions'which may deteriorate with Front wall 64 also includes a pair of grillpanels V illustrated as being of generally square configuration and use.
shown generally by reference numeral 72. Each grill panel includes a frame 73 supporting a plurality of parallel vanes 74 having a distinct curvature for directing air passing therebetween laterally of the vanes, vanes 74 being secured against movement in the illustrated form.
Handles 75 are provided on each of grill panels-72. A
tension spring 76 is provided for each panel72, anchored at one endto a generally centrally disposed portion of panel 72 and anchored at the other end to the interiorf surface of casing 39 spaced inwardly from wall 12. Ten: sion spring 76 biases grill member 72 inward against a framework defined by flanges 22 and an arm of T-braces 65. Either or both of the grill members 72 may be grasped by handles 75, pulled outward and reorientated in rotation or in multiples of 90. in .rotation and reinserted, spring 76 being sufliciently resilient'to permit withdrawal of the panels 72 for reorientationthereof and having suflicient strength-to retain panel 72 inthei position shown in FIGURE1 after reorientation. Thus, by reorientating panels 72 as desired, warm air passing from chamber 34routwardly through 'vanes 74 may be directed upward, downward-or to either side or in any combination of two such directions.
Opening of door 69 and removal of grills 72 gives: ac.- cess to the complete interior of the device for servicing of component in any of the chambers thereof. The rear wall 'of casing 39 is provided with a plurality of ports 79.
for communicating the air space 35 between casing 39 and rear wall 20 with chamber 36. The portion of space along .rear wall 20 is in air communication with'the portion of air space 35 along end wall 12,"but is blocked, by
the portions of air space 35 along top wall-14 and bottom wall 29. The left edge, as viewed in FIGUREZfofthe 7 rear wall of casing 39 abuts and issecured to sidewall 13 adjacent'an edge thereof; peripherally of the louvers 77in wall 13." The top and bottom'walls of casing 39 stop short of wall 13 ;at the lefttin FIGURE. 2.. Thus;
the ends of the portions of air chamber 35lying beneath top and bottom walls 14 and 29 are open for receiving air, as at reference numeral 80, from the slot ports-defined in wall 13 by louversv 77. It will be seen that a pressure drop at ports 79,e.g. created by blower 62, would tend to draw air through open ends 80, along walls 14 and 29,"
thence into the portion of air space 35 beneath wall 1 2, into the portion of air space3'5 beneath'rear'wall'20 and through ports 79 into chamber 36. A flowing blanket of air beneath walls 12, 14, 20 and 29 is thereby created. This flowing blanket of air insulates the walls from the combustion and air heating chamber portion 34 of the.-
device providing external surfaces. of the thusly insulated wallsiwhich are cool to the touch.
However, the total supply of air'to chamber 36, is not obtained from the insulating blanket of flowing air. Sub- V stantial amounts of air are also drawn in through end wall 13. Accordingly, louvers 77 provide a plurality of flow slots through wall 77. Wall 13 is backed by filters 78 so that air passing between louvers 77 passes through filters 78 into chamber 36, filters 78 'being held in place by peripheral flanges projecting inwardly from the top, rear and bottom walls of casing 39 and forming a frame 81, the filters being contained between flanges 81. The filters 78, however, do not extend across openings 80 of air space 35.. For removal of the filters, door 69 is opened and filters 78 may be slid out from the front of the casing for cleaning, replacing or the like. Reinsertion of the filters will be apparent. Door 69, when closed, seals against the front edge of filters 78.
The filters 78 are packed filters having fibers sufliciently compacted to create resistance to flow into chamber 36 therethrough. With blower 62 drawing air from chamber 36, filters 78 serve to provide a pressure drop across the filters. As a result, air is readily drawn into and through air space 35 and into chamber 36, maintaining the blanket of air beneath the outer wall of the air heater device. Air is also drawn into chamber 36 through filters 7-8 and the resistance to flow, or pressure drop, created by filters 78 is sufficient to provide the desired or proper amount of cooling air flowing through chamber 35 for the desired cooling effect on the heater outer walls.
Outlet duct 54 projects through and is secured to the rear wall of casing 39 by means of a circular angle member 82 secured to the outer surface of duct 54 and the inner surface of casing 39. A plurality of concentric tubes 83, 84 and 85 is provided with. tube 83 slidably fitted over tubular duct 54. Tube 83 is the central tube of the plurality. A brace 86 is hooked at one end around the outer end of tube 85 and can be mounted at its other ,end to suitable building structure for supporting the outlet end of the assembly of concentric tubes. A flue shield liner is mounted within tube 85 by suitable spacer mounting brackets. Tube 84 projects through the liner. Two concentric flanges 89 and 90, each concentric with duct 54, are secured to the outer surface of the rear wall of casing 39 and project outwardly through rear wal1 19, as does duct 54. Tubes 84 and 85 are slidably received over flanges 89 and 90 respectively forming a telescoped assembly between tubes 83 through 85 secured to duct 54 and flanges 89 and 90 by force fit.
Cross braces 92 and 93, illustrated as long bolts, impale each of tubes 83 through 85 generally along diam eters thereof, bolts 92 and 93 being illustrated as disposed along different angular dispositions with respect to each other, e.g. at right angles to each other.
Bolts 92 and 93 also impale an inner tube member 94, suspending tube 94 generally centrally within tube 83. Bolts 92 and 93 receive nuts at their straight ends and serve to maintain general concentric disposition of tubes 83 through 85 which are also supported concentrically by exhaust duct 54 and flanges 89 and 90. Attached to and extending part way across the end of tubes 83 there is provided a deflector member in the form of a rigid fiap 95, the function of which will be more evident hereinbelow. Deflector 95 is secured to the upper surface of the outer end of tube 83 by a flange portion welded to tube 83.
A chain 96 extends through small aligned holes in the lower wall portions of each of tubes 94 and 83 through 85. Chain 96 is held generally taut and secured at opposite spaced ends by cotter keys 97 which retain the chain in position by functioning as stops against the inner surface of tube 94 and the outer surface of tube 85. Chain 96 aids in holding the tubes 94 and 83 through 85 in concentric disposition and prevents incorrect placement of the tubes during installation.
As gases are exhausted throughduct 54 there may be some leakage between duct 54 and the tube 83 telescoped thereover, the connection therebetween being a forced fit ,or sliding connection. For this reason, concentric tube 84 is provided surrounding tube 83 to conduct gases which may leak through the connection outwardly away from the area adjacent wall 20 and casing 39 where such gases may be carried into the air intake system and eventually be discharged into the room or building being heated. For like purpose, concentric tube is provided surrounding tube 84 to direct any gases which may leak between flange 89 and tube 84 outwardly away from wall 20.
Disposed below the combustion gas exhaust system described above is the combustion air inlet system which includes a tubular member 98 telescoped and force fitted over a flange. 99. The flange 99 defines the inlet duct for air being drawn into chamber 44 for use by burner 45. Cross brace members 100 and 101, in the form of bolts and nuts, suspend inner tube member 102 generally concentrically within tube 98.
Cross brace members 92, 93, 100 and 101, in addition to functioning for bracing purposes also help to block passage of objects inwardly through ducts 54 and 99 during operation of the device or otherwise. The centrally mounted tubes 94 and 102 are also provided for preventing birds from entering and building nests.
The purpose of the deflector 95 is to prevent reverse flow of combustion gases when the wind is blowing directly at the discharge end of tube 83. With wind blowing directly against the open ends of tubes 83 and 98, deflector 95 creates a cross flow of air which increases or aids the discharge of combustion gases from tube 83 because the wind can enter inlet tube 98 easier than outlet tube 83.
The heater device may be conveniently installed by setting the device on a supporting surface at the desired location and connecting the burner and electrical system in the usual manner to fuel line and thermostat. Means illustrated at 105 (FIGURE 3) are also provided for mounting the device in a position suspended from a wall, desirable where floor space is limited. Accordingly, each mounting 105 includes a circular hole 106 in rear wall 20 of suflicient size to clear the head of a bolt 107 or screw or the like. A slot 108, at least as wide as the shank of bolt 107 and narrower than the head of bolt 107, extends upwardly from hole 106. A plurality of such mountings is provided, each at a different location in rear wall 20, preferably near the top of wall 20. In installing, bolts 107 are secured into the wall at positions spaced in accordance with the spacings of holes 105, With the heads of bolts 107 protruding slightly. The heater is lifted to the wall and holes 105 are guided over the bolt heads and the bolt shanks are directed into slots 106. Burner and electrical connections, etc. are then made to the mounted device.
In operation of the device, motor 63 and burner 45 are started in the usual manner and air is drawn by burner 45 through intake duct 99 into combustion air chamber 44, thence through burner, 45 and the resulting flame and combustion gases are ejected into combustion chamber 50 and are exhausted through ducts 53 and 54 and 83 exteriorly of the room or building. Passage of air through chamber 44 serves to keep electrical system 68 cool. Meanwhile, fan 62 draws air from chamber 36 and forces the air through chamber 34 in heat exchange with furnace or combustion chamber 50 and thence outward through grill members 72 for direction of air into the room as desired. The air is heated in chamber 34. Fan 62 draws air into chamber 36 through louvers 77 and thence in separate paths to chamber 36, one path through filter 78 and the other path through the air space 35 beneath the surfaces of walls 12, 14, 20 and 29. Thus, there is provided a separate flow system, including two flow paths, for drawing air from a room and heating and returning the air and a separate flow system for drawing air from exteriorly of the room for burning fuel by the burner for heating the air by heat exchange with the first flow path, the combustion gases being exhausted exteriorly from the stood in the air heater illustrated therein that the portions not shown in detail are similar to those already described above with respect to FIGURES 1 through 3. The air heater, as shown in FIGURE 5, is particularly adaptedas a free-standing air heater for connection to a chimneysuch as illustrated at 109. For this purpose, a stack 110 is provided of proper length and direction to extend from outlet 54 of chamber 53 to chimney 109. Stack 110. is adapted to connect at its open stack end with chimney 109 for venting flue gas thereto in the usual manner. In the illustrated form, a furnace exhaust branch line 112 of stack 110 connects with flange 89 to enclose out-let duct 54. An end cap 111 is provided on the lower end of stack 110 to seal against escape of exhaust gases. Damper branch 113 is also provided branching from stack-.110 and a damper mechanism 114, of conventional design, is disposed across damper branch 113 at the extended end thereof. Damper114 is designed to swing only inwardly from its closed position and functions as a draft damper.
Damper 114, inclosed position, prevents exhausting of combustion gases therefrom.
A bracing or mounting bracket 115 is provided secured between rear wall 19 and stack 110 to hold stack 110 in proper supported position.
A mufller cap 118 is'disposed over an inlet duct 119 fitted on flange 99. Muffler cap 118 includes a dome-like shell 120 having a peripheral flange or rim 121. Spacing brackets 122 are secured by welding or the like to flange 121 at one end and are machine screwed or bolted to casing rear wall at the other end to support mufller cap 118 spaced from wall 20 a suflicient distance to permit inletof air for combustion purposes. Cap 118 includes a lining of insulation 123, 'e.g. fiberglass or the like, which functions for sound absorption purposes. Cap
118 decreases burner sounds emitted from the combustion chamber or burner inlet while still permitting free-flow of inlet combustion air.
The free-standing form of air heater illustrated in FIG- URE 5, includes apair of channel-shaped tapered leg members 126, one along each side edge of the bottom wall 26 of the furnace casing, forsuppo-rting the air heater from a floor or the like. The channel-shaped tapered legs 126 include outward projecting flanges, 127 from each edge thereof disposed against wall 26. Flanges 127 are secured to bottom wall 26 by machine screws,
welding or the like. It will be noted in FIGURE 5. that the taper of legs 126 provides a bearing surface at each '55' rear corner of the casing for supporting the casing from a surface therebelow, but the taper of the legs-is away from bearing engagement with the surface at the front of the air heater casing. At the front of each leg 126 there is provided a level adjusting support 128 in the form of a foot with a threaded 'shankor leg extending upwardly therefrom and, threaded througha nut -member' which in turn is secured through the bottom wall of channel 126. It will be apparent that the adjusting members are adjustable to change the height of each front corner of the casing by threading the members in one .direction or the other, as desired or needed, resulting in raising or lowering each or either of the rear corners of the air heater.
1. An air heater, comprising: a housing having an exterior wall defining at least an air inlet and an air outlet for said air heater; means defining an air heating chamber within said housing so that intake air is directed through separate branch flow paths from said inlet, one of said flow paths defining a blanket of insulating air between said exterior wall and said heating chamber, the other of said flow paths defining a generally direct route from said inlet, through said heating chamber, to said outlet; a blower mounted in said housing for drawing air in from a room, through said separate flow paths'and discharged as heated. air back to the room; and a filter in said other flow path adjacent said inlet creating a resistance to the flow of air through said other. flow path to insure'the flow of air induced by said'blower into said'insulating flow path while filtering air throughsaid other flow path.
2. An air heater, comprising: a housing having'an exterior wall defining at least an air inlet and anaair outlet for said air heater; means defining an air heating chamber within said housing adjacent to and in communication with said air outlet; means defining a combustion chamber 1 communicating with said combustion chamber for burning fuel therein; means defining an air inlet chamberwithin said housingadjacent to and in communication'with' said air inlet and in communication'with said air heating chamber; said exterior wall, heating chamber and inlet chamber comprising means for directing intake air through separate branch flow paths from said inlet, one of said flow paths defining a blanket of insulating air flowing from said air inlet between said exterior wall and at leasta portion of said heating chamber to said inlet chamber, the other of. said flow paths defining a. generally ,direct route from said inlet through said inlet chamber and said heating chamber to said outlet;'a blower in said other flow path downstream from said inlet chamber for drawing air in from a room, through said separate flow paths and discharged asfheated'air back to the room; and a filte'r' in said other flow path downstream from said inlet creating a resistance to the flow of air through said other flow 'path to insure the flow of air induced by said blower into said insulating flow path while filtering air through said other flow path.
3. In an air heater having a casing with walls and in whichintake air is drawn in from a room through an inlet,
heated in a heating chamber and discharged as heated air back to the room, the improvement which comprises means within the casing for directing the intake air. con-1+ ing from said inlet through separate flow paths, one of said flow paths defining a blanket of insulating air flow-' ing along the interior surfaces of said casing walls, the other of said flow pathsdefining a generally direct route from the room to the air heating chamber, and a filter.
in said other flow path adjacent the inlet creating a resistance to the flow of air through said otherflow path to insure the flow of air into said insulating flow path while filtering air through said other flow path.
' 4. The air heater of claim 3 stream from said inlet. 7 V a l 5. An air heater, comprising: a. housing having an ex terior wal l defining at least an air'inlet and-an air outlet". for said air heater;means defining'an air'heating chamber 4 within'said housing adjacent to and in communication with said air outlet; means defining an air inlet chamber within said housing adjacent to and in communication with said air inlet and in communication with said air heating chamber; said exterior wall, heating chamber and inlet chamber comprising means for directing intake air through separate branch flow paths from said inlet, one
of said flow paths defining a blanket of insulating air flowing from said air inlet between said exterior wall'and at least a portionof said heating chamber to said inlet.
chamber, the other of said flow direct route from said inlet. through said inlet chamber and said heating chamber tosaid outlet; a blower'in saidother filter in said other flow path downstream fromsaid inlet wherein said filter is down:
paths defining a generally creating a resistance to the flow of air through said other flow path to insure the cflow of air induced by said blower into said insulating flow path while filtering air through said other flow path.
5 References Cited by the Examiner UNITED STATES PATENTS 2/1935 Cornelius 1261-10 9/1935 Sadwith 126 1-10 3/1938 Bard 126 -110 10 5/1938 Williams 62-259 Sorsoleil 126-1-10 Ryder et 211. t 126-116 X Watts 126.1'10 Thompson et al 98-612 Roberts 9840 Humphrey 126110 Mueller 126-4 10 Chamberlain 98---62 Martz 1268S JAMES W. WESTHAVER, Primary Examiner.