Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the field of portable forced air heaters as used on build-
ing construction sites and the like; more specifically to a forced air heater with no exit
flame and wherein the heated air flow is substantially free from exhaust gases.
The use of portable, forced air heaters in buildings under construction is a well
05 established practice for purposes of both drying and heating. Typically such heaters
utilize propane as a source of combustible fuel. The propane is burned and the result-
ant exhaust gases directed to the work site.
Not surprisingly, the exhaust stream carries with it the odor associated with the
burning air/fuel mixture, which odor often leads to headaches and/or nausea in work-
10 ers exposed to it for extended periods.
The nature of the construction of such portable heaters, whether propane pow-
ered or otherwise, is such that the flame is generally open, hence making the use of
such heaters impossible in a potentially explosive environment.
It is desirable, therefore, to devise a portable heated air delivery system wherein
15 the means for igniting the fuel and the combustion process itself is completely con-
tained. It is also desirable to provide a portable heated air delivery system wherein the
heated air stream is substantially odor free.
The device embodied herein accomplishes these ends by providing a heat ex-
changer shell which completely encloses the fuel burner and acts as a combustion cham-
20 ber within which the ignited air/fuel flame-front propagates. Outside air, or air at room
temperature, is directed by fan means over the outer surface of the heat exchanger and
delivered, substantially odor free, to the desired worksite.
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According to one aspect the present invention is a flame free, hot air delivery
system co~ lisillg:
a first ribbed, conical heat exchanger shell having an open apex and base;
a second ribbed, conical heat exchanger shell having an open apex and base and per-
S manently affixed, base to base, to the first heat exchanger shell;
a cylindrical exhaust plenum incorporating a perforated exhaust baffle plate at one
end, capped at the other end and axially affixed at the baffle end to an open apex of
one of the heat exch~nger shells;
at least one exhaust pipe permanently affixed to the outer surface of the exhaust ple-
10 num and colllmullicating therethrough with the interior of the plenum;
a cylindrical fuel burner support structure axially affixed at one end to the open apex of
the other heat exchanger shell;
fuel burner means attached to the other end of the burner support and extending
coaxially into the burner support;
15 outer shroud means enclosing the heat exchanger shells and exhaust, and open at both
ends; and
fan means attached to one end of the outer shroud to direct air flow into the outer
shroud, over the heat exchanger shells and out the other end of the outer shroud means.
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According to another aspect the present invention is a forced air heating deviceCOlll~l isil~g:
heat exchanger means;
burner means enclosed within the heat exchanger means so that combustion is con-05 fined to within the heat exchanger means;
exhaust means collllllunicating with the heat exchanger means so that the products of
combustion are removed from within the heat exchanger means;
shroud means enclosing the heat exchanger means and the exhaust means and open at
both ends; and
10 fan means to drive outside air into one end of the shroud means, over the heat ex-
changer means and out the other end of the shroud means.
A detailed description of a prerell ed embodiment of the present invention is set
forth herein having reference to the accompanying drawings wherein closely related
drawings bear the same number but differing alphabetical suffixes and wherein:
1S Figure 1 is an exploded view of the heat exchanger showing the relative positions of the
various component parts of the heat exchanger;
Figure lA is an assembled view of the heat exchanger;
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Figllre lB is a frontal view of the heat exchanger;
Figure 2 is a side view of the heat exchanger and burner assembly with cut-away section;
Figure 2A is a rear view of the heat exchanger and burner showing the placement of the
forced air fan motors; and
05 Figure 3 is a side view of the invention showing the outer shroud and the relative posi-
tioning of the heat exchanger and burner within the shroud.
Refer to figures 1 to lB
At the core of the presently preferred embodiment of the invention is a heat
exchange unit generally designated as 4. In practice it was found that Inconel (Trade-
mark) 62 gauge, Alloy 601, heat designation NX5044MG/CK89A provided the best
results as heat exchanger construction material.
The heat exchanger unit 4 is comprised of a first conical shell 6 having a pluralityof surface ribs 8, the ribs 8 significantly increasing the overall surface area of the shell 6
relative to an equivalent non-ribbed structure. The shell 6 is open at both base and
15 apex and is permanently affixed, base to base, by conventional means such as welding
to a substantially identical second conical shell 6' such that the structure thus formed is
hollow with axially aligned openings at both ends.
An exhaust plenum 18 comprised of a robust, rigid walled, generally cylindrical
structure having at least one circulllferentially placed through hole 22 is permanently
20 capped at one end, via welding means, by a rigid plate 20.
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A generally circular, rigid, exhaust baffle plate 16 of uniform wall thickness hav-
ing a plurality of surface perforations is inserted into the other end of the plenum 18
substantially flush with the rim of the plenum 18 and permanently affixed therein by
welding means.
05 At least one rigid walled exhaust pipe 24 contoured to generally follow the slope
of the heat exchanger shell 6 and 6' is inserted at one end into the cir~;ulllrerentially
placed through hole 22 of the plenum 18 and permanently affixed thereto by welding
means.
The exhaust plenum 18 is axially and permanently affixed at the baffle plate 16
end to the open apex of the first heat exchanger shell 6.
A generally cylindrical, rigid walled burner housing 10 incorporates at one end a
mounting plate 12 having a plurality of through holes 14, and is axially and permanently
affixed by welding means at the other end to the open apex of the second heat ex-
changer shell 6'.
Refer to Figures 2 to 3.
A collvenlional fuel burner, generally designated as 28 and comprising a fuel de-
livery system 30, a fan motor 32, a burner tube 38 and a mounting flange 34 is attached
- via bolts 36 firstly to a robust, rigid annular frame 26 having a rigid cross brace which
incorporates multiple mounting hole configurations and therefrom to the burner hous-
ing 10 mounting plate 12 such that the burner tube 38 extends co-axially into the burner
housing 10 and partly into the body of the heat exchanger shells 6 and 6'. At least one
fan motor 42 is attached to the cross brace of the annular frame 26 such that the outlet
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of the fan motor 42 faces the second heat exchanger shell 6'.
A first hemi-spherical outer shroud 48 having an open crown and an open, lipped
base is positioned over the frame 26 and secured to the frame 26 by any conventional
and a~lo~liate means such that the base of the shroud 48 faces away from the frame
05 26.
A second hemi-spherical outer shroud 46, substantially equal to the first shroud48 is positioned over the heat exchanger 4 and secured to the first shroud 48, base to
base, by means of a conventional binding strip 52. The second shroud 46 further incorpo-
rates an opening on its top surface to accommodate an exhaust flue 54, which flue
10 aligns with and encloses the heat exchanger 4 exhaust pipe 24.
In use, the heating system of the present invention, generally designated as 44
may be permanently fixed within a structure to be heated or mounted to an applol)ri-
ate conveyancing system (not shown) to facilitate portability.
An ap~ro~l iate source of fuel - diesel or propane - and electrical power (neither
15 source shown) is connected to the burner 28 and ignited by conventional means such as
a electric spark generator (not shown) at the burner tip 38.
Combustion occurs within the heat exchanger shells 6 and 6' respectively and thesurface of the respective shells 6 and 6' begin to heat. Outside air is forced over the
surface of the heat exchanger shells 6 and 6' by means of at least one fan motor 42, the
20 air temperature is raised and the air passed to the worksite via the crown opening in
the second outer shroud 46.
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Exhaust gases are collected in the exhaust plenum 18 and evacuated to the at-
mosphere via exhaust pipe 24 and exhaust flue 54. It may be readily appreciated that by
adding collvenlional galvanized heat ducting 56 to the crown opening of the shroud 46,
the hot air output of the system 44 may be routed to areas remote to the system 44
05 itself.
While the heated air output of the system 44 is substantially odor free and is
appropriate in those environments where the release of the air into the environment is
required for heating purposes, it will also be understood that the heat from the exhaust
gases need not be simply vented but may, instead, become a source of radiated heating
10 in appropliate cir-;u~lls~ances. For example, passage of the exhaust ductwork through a
green house structure before venting may well be a practical and cost effective alterna-
tive to convelllional green house heating systems.
It will also be understood that, by virtue of the fact that there is no naked flame
and the only source of potential sparking is to be found at the electrical fan motors and
15 the burner, that the complete system may be readily rendered suitable for use in poten-
tially explosive envirolllllents with relatively little modifications.
The above description should not be construed as limiting the scope of the inven-
tion but rather as an illustration of a presently preferred embodiment. It is readily
apparent that variations in the placement of components may be achieved without
20 detracting in any significant manner from the efficient operation of the invention. It is
also reasonable to suppose that enhancements may be made to the way in which theinvention pelrolllls without departing from the spirit of the invention as herein dis-
closed. For example, it is not beyond available technology to limit cycle the operation
of the burner in response to a thermostat, thus maintaining a constant output tempera-
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ture over a range of climatic conditions. Thus the scope of the present invention should
be determined by the appended claims and their legal equivalents.
