Note: Descriptions are shown in the official language in which they were submitted.
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The presen-t inventi4n ~late~ to improvements in the boiler
for heating water, disc]osed in my copending Canadian Patent
Application Serial No. 288,355, filed October 7, 1977, and en-
titled "~eating Boiler for the Combustion of Liauid or Gaseous
Fuel".
The boiler comprises a casing for holding the water to be
heated and including two end walls defining apertures and a side
wall e~tending between the end walls, the casing walls being
of steel sheet. A fire box unit is inserted in the casing and
includes a tubular cast iron body mounted fluid-tightly in the
apertures of the end walls of the casing, the cast iron body hav-
ing an inlet end and an outlet end protruding beyond the end
walls and having a plurality of radially inwardly extending webs
distributed over the circumference of the tubular body. A com-
bustion chamber shell is mounted in the inlet end of the tubular
cast iron body, the shell having a fuel burner inlet for burning
a liquid or gaseous fuel in the combustion chamber defined by
the shell and a closure wall opposite the fuel burner inlet
; whereby the combustion gases of the burnt fuel are deflected
back towards the fuel burner inlet. A gas guide chamber at
-the fuel burner inlet receives the deflected gases and a gas
collecting chamber is adjacent the closure wall at the outlet
end of the cast iron body. The shell with the bas guide and
collecting chambers is support3d on the radially inwardly ex-
tending webs of the cast iron body and defines therewith gas
flues leading f~rom the gas guide to the gas collecting chamber.
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The points of conn2ction between the ca~t iron bocly
and the ~teel sheet casing are not machined and the good
malleability of the sheet steel i~ combined with the cast
iron body so that no welding is required for providing a
fluid tight connection therebetween while the integral
ca~ting of the radial webs with the tubular body provides
the required ducts for the flue gases.
The combination of a ~teel sheet casing holding the
water and a cast iron fire box unit inserted therein
has the advantage that the casing may be readily connected
to one or more ho-t water storage chambers, which ls
practically impossible with an all-cast iron boiler because
of the resultant complexity of the castings and the problems
of providing fluid tight connections. Furthermore, this
combination makes it possible to arrange several superposed
cast iron fire box inserts in the water casing and to
operate with separate ~uel burners so that it iq possible
to operate a selected number of t~ese units, depending on the
hot water requirements.
Operation of this advantageous boiler di;,closed in my
copending application has shown that, while the gases in
the flues heat the water in the casinc~, condensate tends
to form in a bottom re~ion o:f the protruding ends of the
tubular cast iron body in the gas flues.
In accordance with this invention, the boiler has been
improved by shaping the tu~ular cast iron body to converqe
frusto-conically from the inlet towards the outlet end, and
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a shoulder dams the flow of the condensate in the botto~
region of at least the protruding lnlet end of the tubular
cast iron body.
~ en a boiler of the indicated type is operated at
different tempera-tures, a considerable amount of condensate
will form in the ducts for the flue gases. I-t has proved
to be very difficult to seal the connections between the
end walls of the water casing and the fire box unit fluid
tightly enough to prevent escape of condensate through
the gasket. The condenqate tends to corrode and destroy
the gaskets since it consists ,of sulfuric acid or sulfurous
acid. If it passes out of~the gas flues, it will run down
the steel sheet wall of the casing and ~r.roy the same or
the insulating jacket surrounding it, : .
The above and other ob'jects, advantages and f2atures,
of the invention will become more apparent from t~e following , :
detailed description of certain no~,~ pre~erred embodiments :
thereof, taken in conjunction with the accompanying schematic .:
drawing wherein '~::
I FIG. 1 shows on~ embodiment of the boiler in longi-
tudinal cross sec-tion throug~ e axis of the boiler, , :~
FIG~ 2 is an end view of the boiler, partly ~ transverse ~ , ,,-
cross section
FIGS. 3, 4 and 5 are sim~lified long:itudinal sections o~
modified embodiments of the boiler,
FIG. ~ is a partial longitudinal section o a port.ion
~'l of the boiler showin~ a modified detai.l, and
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FIG. 7 is a like partial section illustrating another
rnodified detail~
Referring now to the drawing wherein like reference
numerals desi~nate like parts functioning in a like manner
in all figures, FIG. 1 shows the essential parts of a
boiler for heating water according to the present invention.
This boiler comprises casing 29 for holding water to be
heated and including end walls 3 and 4 each defining central
apertures arranged concentrically about axis 31 of the
boiler and side wall 12 extending between the end walls.
The casing walls are of steel sheet.
Fire box unit 1 is inserted in casing 29 and surrounded
thereby. ~e fire box unit includes tubular cast iron body
2 mounted fluid-tightly in the apertures of end walls 3, 4
of casing 29 in a manner to be described hereinafter~ Cast
iron body 2 is also arranged concentrically about boiler
axis 31 and has inlet end 22 and an outlet end. The ends
of the cast iron body protrude beyond end walls 3 and 4,
and body 2 is shaped to converge frusto-conically from tha
inlet toward3 the outlet end. As best sho~n in FIG. 2,
a plurality o~F radially inwardly extending webs 9 are
distributed over the circumference of tubular body 2,
projecting from interior wall 5 of cast iron body 2 and being
cast integrally therewith~
Combustion c~amber shell 7 is mounted in ~et en~ 22 of
tubular cast iron body 2 and has a fuel ~urner inlet 13 for
burning a ~aseous or li~uid fuel in the combustion ctlamber
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defined by shell 7 ( the fuel burner not being shown ).
Clo~ure wall 14 opposite fuel burner inlet 13 deflects
the combustion ga~es of the burnet fuel back towards the
fuel burner inlet where gas guide chamber 10 receives the
deflected gases, this chamber having a somewhat larger
diameter than the combustion chamber. Gas collecting cham~er
11, which also ha~ a larger diameter than the combustion
chamber, i~ adjacent closure wall 14 at the outlet end of
cast iron body 2. The shell with the ~as guide and col~
lecting chambers i9 supported on radially inwardly extending
webs 9 of cast iron body 2 and defines therewith gas flues
15 leading from ~a~ guide chamber 10 to gas collecting chamber
11. In view of the enlarged diameters of the gas guide and
collecting chambers, webs 9 are higher in the center region
supporting the portion of shell 7 defining the combustion
chamber than in the end regions 9' of the webs so that ends
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30 of ~he webs support the shell in ~he cast iron body,
the ~hell being readily removably by sliding it along the
supporting ends of the webs which hold ~he shell in position.
The ~héll may be o~ stainless steel.
The hot ga~es flowing in flues 15 Erom guide chamber
10 to collec~ing chamber 11 heat the water in the annular
chamber defined between tubular cast iron body 2 and casing 29.
Particularly when the boiler is operated at changing
temperatures, condensate will inevitably tend to form in
the bo-ttom region of the tu~ular cast iron body in the gas
~lues~
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To prevent such condensate to reach gas~ets 34 which
are interposed as a fluid-tight seal between I-he inlet
and outlet ends of the cast iron body and closures 33
mounted thereover, shoulder 23 dams the flow of the conden~ate
in the bottom region of the protruding inlet end 22 of the
tubular cast iron body, the illustrated e~bodiments
showing a like condensate damming shoulder 23' at the
outlet end.
In the embodiment of FIG. 1, closure 33 at the outlet
end is integral with flue connection 24 for removing the flue
gase~ from gas collecting chamber 11. Inqulating collar 16
is mounted on inlet closure 33 and surrounds the fuel burner
~not shown) whose flame projects therethrough.
In the absence of shoulders 23, ~ ', conden3ate would
flow into contact with gaskets 34 and would eventually des- -
troy them. The conicity of tubular cast iron body 2 assures
flow of the condensate formed particularly in the bo-ttom
half of the boiler towards the inlet end which is in contact
with the hottest part of the combustion gases. ~nis will
facilitate evaporation of at least a portion of the condensate.
The lower the temperature of the gases, the higher the deg~e~
of condensation, i.e. the flue gases tend to condensate
mostly towards the outle-t end, i.e. in the region of gas
collecting chamber 11. Therefore, it is advantageous to
assure flow of the condensate from that region towards the
inlet end, i.e. into the gas guide chambe~ , wherein the
temperature i~ hottest. As indicated, the conicity OL th~
-tubular cast iron bod~ forces this con~ensate flow even if it
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e~tends onl~ over three fourths or two thirc~s of -the len3th
of tu~ular body 2 and the remaining length of the body at
the inlet end is cylindrical.
If the tubular cast iron body of the fire box unit
is frusto-conical along its entire length, i-t may be
use~ul to shape the central portion of the shell d~fining
the combustion chamber accordingly. Such an embodiment is
shown in FIGS. 3 and ~ where shell portion 7' is frusto-
conical and extends parallel to tubular cast iron body 2.
For this purpose, suppor-t ends 30' of radially extending
webs 9 are similarly inclined from the inlet towards the
outlet end so as to positio~ shell 7' coaxially in the boiler~
Su~h a cast iron unit may be cast with a "green" core,
i.e. the body would be shape~ and cast vertically. Since
all walls are conical and if the webs are thinner in front
than in back, the form may be so prepared that the core is
formed of sand in the interior. This make~ it possible to
cast the body with a su~stantially dome-shaped end wall 33'
(see FIG. 4) at the outlet end there~y body 2 assumes a be71
shape. A suitable opening may ~e cast into the dome-shaped
erld wall to receive flue 2~' extending from the end wall for
removing the gases from gas collectin~ chamber 11. The
manufacturing cost of casting such a unit are le~s than when
the tubular body has to be cast with separately prepared
cores, which is neces3ary wlth cylindrical interiors.
The fire box unit i9 fluid-tightly connected with water
casing 2~ without weldin~, which is very advantageous ~ecal~se
welding steel sheet to cast iron is rather dif,icult ancl
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does not assure a fluid tight seal in -~iew o:F the
difference in the thermal expansion coefficient be~ween
the two materials.
One preferred fluid-tig}lt connection according to -this
inven-tion is shown in FIG. 1. In this preferred embodiment
of the connection, tubular cast iron body 2 has machined
annular circumferential regions 25 and end walls 3, 4
of casing 29 having corresponding annular rims 26 forming
a press or friction fit with the machined reyions of the
cast iron body, Sealing medium 27 forms a fluid-ti~ht
interface between the machined regions of the cast iron
body and the annular rims of the steel shset end walls. The
sealing medium may be a hea-t- and liquid-resistant putty which ',
also operates as a lubricant. To provide the required friction
fit, the inner diameter oF rim 26 is slightly less than the
outer diameter of tubular body 2 at the machined regions.
The cast iron body has annular collars 28 adjacent machin~d
reglons 25 to form abutments for end walls 3, 4 of t-he casing.
FIG. 6 illustrates a less desirable fluid-tight connection
wherein end walls 3, 4 of casing 29 are threadedly connected
with annular collars of the cast iron bocl~, with sealing ri~gs - ,,
ox gas~ets making the threacled connection fluid-tight. This
produces a fluid-tight but detachable connection ~etween ~ ''
the steel shee-t walls of the casing and the cast iron kody
,
of the fire box unit~ ~'
~ o avoid su~jec~ing ~-teel shcet casing 29 to t'he~ load
caused by mounting closures 33 on the boiler, cast iron
body 2 is cast ~ith parts 32, 32' for affixinc3 the closures
I
`~ to the cast iron bocly, ~or example hingedly. In t~.is manner,
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the cast iron body is the carrier oE the boiler closu-es.
This makes the entire manufacture of the boiler more
economical.
In ~he embodiment of FIG. 5, cast iron body 2 is shown
to be conical only over part of its length while being
cylindrical near the inlet end. In this e~mbocliment, the
shell defining the combustion chamber may be cylindrical,
as in FIG. l. As long as the tubular ca~t iron body
tapers inwardly toward the outlet or colder end of t~e
fire box unit, it has the advantage that t.he volume of the
colder gas is reduced in relation to the volume of the hot-ter
gas.
~ IG. 7 shows a modified emhodiment o the fluic1~tight
connection between steel sheet end walls 3, ~ and tuhular
cast iron body 2. In this e~.~bodiment, machined annular region
25' of tubular body 2 i5 frusto-conical and rim 2~' of the
end wall is correspondingly frusto-coni~al to provide a press
or friction fit therebetween. The tubular body has a slight
circum~erential shoulder 25" spaced from machined re~ion 2S'
by an annular groove~ The outer dlamet-er of shoulder 25"
is between the inner and ~uter d.iameters of rim 26'. In
this manner, when rim 26' is moved against collar 28 for
frictional enga~emen-t with machi~ed annular region 2S', the `
rim snaps lnto position over shoulder ~ and is thus securely
positioned. I~ any leak should ever develop at this
co.nnection, it may be readily repaired by placing a sealin~
tape thereover.
~ hile tubular ~ody 2 has heen illu.strated .15 C~/L'ndriCcl
lt may be oval in cross sectlon.
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