PLAQUE DE PROTECTION DE CHAMBRE DE COMBUSTION POUR CHAUFFE-EAU

COMBUSTION CHAMBER SHIELD FOR HOT WATER HEATERS

Abrégé français

Description d'une plaque de protection pour chambre de combustion pour chauffe-eau. La chambre de combustion est une chambre scellée ou sans combustion, et la plaque de protection en métal l'enveloppe et est séparée du brûleur et de la veilleuse, qui se trouvent dans la chambre de combustion. La plaque de protection est également séparée de la jupe et de la paroi inférieure de la chambre de combustion. La plaque de protection comporte en outre des orifices pour permettre le passage de l'air dans un conduit d'aération. La plaque de protection concentre la chaleur sur une paroi de transfert de chaleur inférieure de l'enveloppe inférieure contenant l'eau à chauffer. Elle réduit aussi la perte de chaleur par la jupe et la paroi inférieure de la chambre de combustion.

Abrégé anglais

A shield for a combustion chamber of a hot water heater is described. The combustion chamber is a sealed or not combustion chamber and the metal heat shield encircles and is spaced about the burner and pilot which is located in the combustion chamber. The shield is also spaced from the skirt and a bottom wall of the combustion chamber. The shield is further provided with apertures to permit passage of air supplied by an air supply duct. The shield provides for heat concentration on a lower heat transfer wall of the inner casing containing the water to be heated. The shield also reduces heat loss through the skirt and the bottom end wall of the combustion housing.

Revendications

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CLAIMS,
1. A shield for a gas-fired combustion chamber of a hot water heater,
said hot water heater having an inner casing for the containment of water to
be
heated by a combustion chamber disposed under said inner casing, a burner and
pilot in said combustion chamber, a flue pipe extending from said combustion
chamber to evacuate combustion gases, an outer casing secured spaced about
said
internal casing and insulated therefrom by a thermal insulating material, a
support
base at a bottom end of said water heater, a skirt about said combustion
chambe r
spaced internally from a lower end portion of said outer casing, air passage
means
to supply air to said combustion chamber, and a heat shield formed of metal in
said combustion chamber encircling and spaced under and to the sides of said
burner and pilot, said shield being spaced from said skirt, air aperture means
in
said shield and disposed under and to the sides or said burner and pilot, to
permit
passage of air supplied through said air passages means; said shield providing
heat
concentration in said combustion chamber and on a heat transfer surface of a
lower wall of the inner casing, and reducing heat loss through said skirt and
a
bottom end of said combustion chamber.
2. A shield as claimed in claim I wherein said combustion chamber is a
sealed combustion chamber, said passage means being an air channel means, said
shield being spaced also from a bottom end wall of said combustion chamber.
3. A shield as claimed in claim 2 wherein said bottom end wall is
supported elevated by said support base, said support base having vent holes
to
circulate air against said bottom end wall.
4. A shield as claimed in claim 2 wherein said aperture means is one or
more apertures formed in said heat shield.

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5. A shield as claimed in claim 4 wherein said shield is a cup-shaped.
cylinder shield having a circular bottom wall, a cylindrical side wall secured
to a
periphery of said bottom wall and projecting thereabove, and an open top end
facing said heat transfer wall of said inner casing.
6. A shield as claimed in claim 5 wherein said cylinder shield is secured
by support means to position said cylinder shield spaced from said sealed
bottom
wall and said skirt to provide an air supply space about said shield, said
channel
means communicating with said air supply space.
7. A shield as claimed in claim 6 wherein said air aperture means is
constituted by a single large central aperture formed in said circular bottom
wall,
said burner being supported above said central aperture and concentrically
spaced
from said circular side wall.
8. A shield as claimed in claim 6 wherein said air aperture means is
constituted by a plurality of holes provided in said circular bottom wall and
said
cylindrical side wall.
9. A shield as claimed in claim 4 wherein said shield is an inverted
dome-shaped shield defining a concave inner surface facing an open top end
thereof and a convex outer surface disposed spaced from said sealed bottom
wall
and said skirt, said open top end facing said heat transfer surface of a lower
wall
of said inner casing.
10. A shield as claimed in claim 9 wherein said heat transfer wall of said
inner casing is a concave wall, said shield being secured concentrically below
said
heat transfer wall whereby heat radiation from said concave inner surface will
be
concentrated on said heat transfer wall.

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11. A shield as claimed in claim 10 wherein said air
aperture means is constituted by a single large central
aperture formed in said inverted dome-shaped shield at an
apex thereof, said burner being supported above said central
aperture.
12. A shield as claimed in claim 10 wherein said air
aperture means is constituted by a plurality of holes
provided in said inverted dome-shaped shield.
13. A shield as claimed in claim 3 wherein said
channel means is a vertical duct connected at a lower end to
an air supply space about said shield between said sealed
bottom wall and said skirt, said vertical duct having a top
inlet end spaced a predetermined distance from said support
base to admit fresh air in said duct to supply said air
supply space and burner.
14. A shield as claimed in claim 1 wherein said
passage means is constituted by apertures formed in a
support base of said hot water heater.

Description

CA 02417551 2003-01-28
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COMBUSTION CHAMBER SHIELD
FOR HOT WATER HEATERS
TECHNICAL FIELD
The present invention relates to a shield for a
combustion chamber of a gas-fired hot water heater whereby
to provide heat concentration in the combustion chamber and
on a lower heat transfer wall of the inner casing and also
to reduce heat loss through the skirt and the bottom end of
the water heater.
BACKGROUND ART
With known gas-fired hot water heaters using
combustion chambers, there is a substantial heat loss
through the lower skirt of the housing which is disposed
adjacent the combustion chamber of the water heater and
through the lower end portion of the housing. With the new
designs of sealed combustions, combustion air is supplied
through a vertical duct which is in registry with a supply
hole provided in the skirt and therefore the insulation in
that area is reduced. Also, the insulation between the
lower skirt and the outer casing is not sufficiently thick
and this results in heat loss as sealed combustion chambers
become very hot. Accordingly, there is excessive heat loss
through the skirt and the lower region of the hot water
heater housing and the performarlce or efficiency of the hot
water heater is reduced. There is therefore a need to
overcome this problem.
SUMMARY OF INVENTION
It is a feature of the present invention to
provide a shield for the combustion chamber of a hot water
heater which substantially overcomes the above-mentioned
disadvantage of prior art water heaters of this type.
Another feature of the present invention is to
provide a shield for the combustion chamber of a hot water

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heater and which shield reduces heat loss through the skirt and
outer casing and the bottom end of the hot water heater housing by
about 30 to 50 percent over previous designs.
According to a further broad aspect of the present
invention there is provided a shield for the combustion chamber of a
hot water heater wherein the heat in the sealed combustion chambe=-
is concentrated on the lower transfer wall of the inner casing while
at the same time reducing heat loss through the skirt and the bottorn
end wall of the housing.
According to above features, from a broad aspect, the
present invention provides a shield for a gas-fired combustio:~
chamber of a hot water heater. The heater has an inner casing for
the containment of water to be heated by a combustion chamber
disposed under the inner casing. A burner and a pilot are provided
in the combustion chamber. A flue pipe extends frorn the combustion
chamber to evacuate combustion gases. An outer casing is secured
spaced about the internal casing an insulated therefrom by a thermal
insulating material. A support base is provided at a bottom end of
the water heater. A skirt is provided about the combustion chamber
and spaced internally from a lower end portion of the outer casing.
Air passage means is provided to supply air to the combustion
chamber. A heat shield, formed of metal, is secured in th.e
combustion chamber and encircles and is spaced under and to the
sides of the burner and pilot. The shield is spaced from the skirt.
Air aperture means is provided in the shield to permit passage of
combustion air supplied through the air passage means. The shield
provides heat concentration in the combustion chamber and on a heat
transfer surface of a lower wall of the inner casing and also
reduces heat loss through the skirt and a bottom end of the
combustion chamber.

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BRIEF DESCRIPTION OF DRAWINGS
A preferred embodiment of the present invention
will now be described with reference to the accompanying
drawings in which:
FIG. 1 is a fragmented side view of a hot water
heater having a sealed combustion chamber and illustrates a
first example of the construction of the shield of the
present invention; and
FIG. 2 is a view similar to Figure 1 but showing
a further example of the construction of the shield of the
present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the drawings, and more particularly
to Figure 1, there is shown generally at 10 a lower portion
of a hot water heater and which illustrates the basic
component parts thereof and more particularly its lower
combustion chamber 11 which is provided with the heat shield
12 of the present invention. As hereinshown, the hot water
heater has an inner casing 13 which is of elongated
cylindrical shape and provided with a central flue 14
extending therethrough and exhausting at a top end in a
manner well known in the art. Water 15 to be heated is
contained within the inner casing 13 and dispensed
therefrom, as is also well known in the art.
The hot water heater as herein illustrated is a
gas-fired hot water heater and its sealed combustion chamber
11 is provided with a burner 16 and a pilot 17 which is
provided with an igniter 18 to kick-start the burners 16. A
control 19 controls the burner and is provided with a water
temperature sensor 20 to effectuate this control. This is
also well known in the art.
An outer casing or shroud 21 is secured spaced
about the inner casing 13 and an insulated material 22 such
as identified by the trade mark Green Foam, registered trade
mark of Giant Factories Inc., is injected in this space

CA 02417551 2003-01-28
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whereby to provide good insulation between the outer wall
13' of the inner casing and the outer casing 21 which is
usually a thin metal sheet cylinder.
The hot water heater is supported elevated from
a support surface 23 by a support base 24 which is provided
with vent holes 25 to provide air circulation under the
bottom wall 26 of the housing which is in communication with
the combustion chamber 11 which is hereinshown as a sealed
combustion chamber, although not essential. Accordingly, it
is desirable to have air circulation under this bottom wall.
It is further pointed out that the entire hot water heater
10 may be supported elevated by other means such as a
platform 23' as shown in Fig. 2, depending on the location
of the air intake ports which supplies air for combustion.
If the air intake is low, then it is preferable that the
combustion chamber be elevated as hi_gh as possible from the
ground surface 23 in the event that ignitable gas fumes may
circulate over the ground surface 23, whereby to provide
added security. The combustion chamber 11 may be a non-
sealed combustion chamber wherein air is supplied thereto
through the vent holes 25 in the support base 24.
Accordingly, the vertical duct 28, as will be described
later would not be required. As well, the bottom wall 26
would not be required or would have air openings therein.
A skirt 27 is disposed about the sealed
combustion chamber 11 and spaced internally from a lower end
portion 21' of the outer casing 21. Combustion air is
supplied to the sealed combustion chamber by suitable means,
and as herein shown by an elongated vertical duct 28, which
is secured at a lower end 29 to the combustion chamber 11.
The vertical duct 28 has a top inlet end 30 which is
provided with aperture means, herein louvered openings 31 to
admit air into the vertical duct to supply the combustion
chamber. The inlet end 31 is elevated to reduce the risk of
explosive gases entering the combustion chamber.

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The present invention provides the heat shield
12 in the combustion chamber 11. As shown in the embodiment
of Figure 1, this heat shield 12 is a cup-shaped cylinder
shield having a circular flat bottom wall 36 and a
cylindrical side wall 37 secured to the outer periphery of
the bottom wall 36 and projecting thereabove. The cylinder
shield has an open top end 38 facing the heat transfer wall
13" of the inner casing 13. This heat transfer wall 13" is
usually a concave dome-shaped wall with the flue 14 disposed
centrally at the apex thereof. Spacing brackets 39 maintain
the shield side wall 37 spaced from the skirt 27 and the
bottom wall 36 spaced from the bottom wall 26 of the
combustion chamber whereby to provide an air space 40 about
the shield. The vertical duct 28 provides fresh combustion
air in this space 40 to supply the burner. Air is drawn
within the space 40 by the hot flame of the burner which
creates a draft within the space about the shield 12 of the
burner drawing air through the holes 41 and about the side
walls 37 of the shield as well as over the top edge. This
helps to cool the skirt 27 and the bottom wall 26. For
example, the skirt 27 without the shield attained
temperatures of about 350 F and with the shield this has
been reduced to 150 F.
As can be seen, the shield 12 is provided with a
plurality of apertures or holes 41 in at least a bottom wall
36. Additional holes 41 may also be provided in the
cylindrical side wall 37. As an alternative, a single large
through-bore 42 may be provided centrally in the shield
bottom wall 36 in line with the burner 16 which is supported
elevated at the center inside the heat shield 12. This
shield 12 provides heat concentration in the combustion
chamber 11 and on the lower heat transfer wall 13' of the
inner casing and reduces heat loss through the skirt 27 and
the bottom end wall 26 of the combustion chamber.
Referring now to Figure 2, there is shown a
further example of the construction of the heat shield,

CA 02417551 2003-01-28
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herein identified by reference numeral 12'. As can be seen,
this shield 12' is a bowl-like shield and therefore has the
shape of an inverted dome which defines a concave inner
surface 45 which faces the open top end 46 of the shield,
and a convex outer surface 47 which is disposed spaced from
the sealed bottom wall 26 of the combustion chamber and the
skirt 27. The open top end 46 faces the heat transfer wall
13" of the inner casing and disposed concentrically below
this heat transfer wall whereby heat radiation from the
concave inner surface is concentrated on the heat transfer
wall 13" to achieve better heat exchange between the inner
casing and the combustion chamber.
The heat shield 12' is also provided with
apertures 48 all around the inverted dome-shaped shield or
alternatively a single large aperture 49 may be disposed at
the apex of the dome and concentrically aligned with the
burner 16, similar to the aperture 42 in the previous
embodiment of the shield as above-described. The dome
shield 12' is secured by the spacing brackets 39' similar to
the embodiment of Figure 1. As can be seen with this
embodiment, the air space 50 surrounding the shield is much
larger and this inverted dome-shape shield design enhances
the heat concentration on the transfer wall and the
reduction of heat loss through the skirt 27 and bottom end
wall 26 of the sealed combustion housing. These shields are
preferably, but not exclusively, formed of steel material
capable of resisting the high temperature heat of the
combustion chamber.
It is within the ambit of the present invention
to cover any obvious modifications of the examples of the
preferred embodiment described herein, provided such
modifications fall within the scope of the appended claims.

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