Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an improved,
insulated chimney structure of the type comprising an
inner flue, an outer casing spaced from the flue and a
solid insulating material therebetween.
Insulated chimney structures of the above mentioned
type are well known in the art and commonly used in building
construction for use with a furnace, a stove, a fire place
or any other appliance requiring a chimney. In such a
construction, the chimney is generally made in two parts.
The first one which is located indoor and comes from the
appliance and goes to the first floor or ceiling of the
building is not insulated and is made of cylindrical, sheet-
metal tubings fitted together end to end. The second part
of the chimney which extends the first part from the first
floor or ceiling either indoor and/or outdoor to above
the roof, is usually- made of insulated tubings having the
above mentioned structure to protect the wall, ceiling and/or
roof structure from the heat of the hot combustion gases
and to improve the chimney draft by preventing the hot gases
from cooling too fast thus slowing their rising movement.
Insulated chimney structures of the modular type
that can be positively engaged with, and attached to, each
other for facilitating chimney installation, are also known
in the art and commonly used in building construction.
As aforesaid, these known structures each comprise
an outer casing, an inner flue coaxial with the casing but
spaced apart therefrom and a solid insulating material
therebetween. The casing and flue are usually made of metal
sheets each having a pair of longitudinal edges and each
folded into a closed cylinder with their respective edges
rigidly connected to each other to define a continuous, non
expansible lock joint or seam. Both metal sheets are of
a given length to define a tubular chimney module which is
advantageously provided at one end with a male coupling
and at the other end with a female coupling positively
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engageable and lockable with the opposite couplings of another
module of the same type. Of course, the annular space defined
between the flue and casing is filled with the solid insulat-
ing material which generally consists of a mixture of silica
and mineral wool.
In all these known structures have the above men-
tioned advantages of protecting the building structure and
improving chimney draft, they all have also a major drawback
due to the differential expansion existing between the inner
flue, when the same is heated at substantially high temper-
atures by the combustion gases, and the outer casing which
remains substantially at the same temperature. As can
easily be understood, when the inner flue made of metal sheet
is heated by the combustion gases from the appliance, it
undergoes a radial expansion. However, as the outer casing
does not undergo the same expansion and the solid insulating
material is not compressible or very little only, the surface
of the inner flue warps , the outer casing tears or the
lock joint of the flue or casing breaks. In all cases, the
chimney structure is damaged and the draft is reduced. In
some critical cases, the chimney may even become a fire
hazard for the building.
The object of the present is to provide an improved
insulated chimney structure which overcomes the above
mentioned drawback.
In accordance with the invention, this object is
achieved in a chimney structure of the above mentioned type
wherein the longitudinal edges of the metal sheet flue are
connected to each other in a non rigid manner to make the
continuous lock joint of the flue expansible.
Preferably, the longitudinal edges of the flue
are both bent back over themselves to form a pair of
oppositely directed U-shaped hooks engaged one inside the
other to form the expansible lock joint.
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As can be easily understood, this improved struc-
ture allows the metal sheet flue to freely expand whenever
it is heated, without radially pressing against the insulating
material and the outer casing. Thus, this improved structure
advantageously prevent all the structural damages mentioned
hereinabove.
The invention will be better understood with refe-
rence to the following non restrictive description of a
preferred embodiment thereof, taken in connection with the
accompanying drawings wherein:
Fig. 1 is a perspective view of a length of an
insulated chimney structure according to the invention;
Fig. 2 is a side elevational, cross-section, view
of a wall of the chimney length shown in Fig. l;
Fig. 3 is a top plan view in cross-section of the
chimney length shown in Fig. l; and
Figs. 4a and 4b are partial, perspective views of
the lock joints of the flue and casing of the chimney length
shown in Fig. 1, respectively.
The insulated chimney length 1 as shown in Fig. 1,
is of the modular type. As every chimney length of this
type, it comprises an outer casing 5 and an inner flue 7
spaced from the casing.
The casing 5 and flue 7 are both made of metal
sheets. These sheets can be made of stainless steel or
of any other metal resistant to heat and corrosion.
The metal sheet forming the casing 5 has a pair
of longitudinal edges. This metal sheet is folded into a
closed cylinder and its longitudinal edges are connected
to each other to define a continuous, non expansible lock
joint or seam 23. As shown in greater detail Figs. 3 and
4b, the joint 23 is preferably of the double type, with the
edges 29 and 31 of the casing folded back upon themselves
to form a pair of oppositily directed U-shaped hooks that
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are engaged one inside the other and both locked in a rigid
manner by a pair of abutment edges 33 and 35 obtained by
radially bending the metal sheets over the U-rounded ends
of the U-shaped hooks 29 and 31. The joint 23 can be made
by cold-forming or by any other method known for shaping
metal sheet.
The metal sheet forming the flue 7 also has a pair
of longitudinal edges. This metal sheet is folded into a
closed cylinder having a diameter smaller than that of the
casing 5. The longitudinal edges of the flue are connected
to each other to define a continuous, expansible lock joint
21 as will be described in greater detail hereinafter.
The flue 7 is coaxially positioned inside the
casing 5 and connected thereto by a pair of braces which are
shaped at one end into an annular cap 9 and, at the other
end, into an annular bottom 11, respectively. The cap 9
and bottom 11 can be made of stainless steel and be attached
to the flue and casing by means of rivets 17 and 19 of
stainless steel and/or by means of spot welds 17'.
As can easily be understood, the casing 5, flue
7, annular cap 9 and annular bottom 11 altogether define a
closed annular volume forming the body of the chimney length,
which volume is filled with a solid insulating material 3
to produce a complete module. As solid insulating material,
use can be made of a mixture of silica with mineral wool or
of any other heat resistant, insulating material or powder.
This insulation advantageously protects the wall, ceiling
and/or roof structure through which the chimney module 1
passes, from the heat of the combustion gases passing
through the flue 5. This insulation also improves the draft
of the whole chimney made from module 1 by preventing the
combustion gases passing through the flue from cooling too
fast before they leave the top of the chimney, which cooling
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would slow down their rising movement.
To facilitate the installation of a chimney to
a building construction, each module 1 is advantageously
provided at one end with a male coupling and at the other
end with a female coupling. Each of these couplings are
of course sized to match when fitted into one another.
In the illustrated embodiment, the male coupling
is formed by the cap 9 while the female coupling is formed
by the bottom 11. Of course, the cap and bottom are
appropriately sized to match with the opposite couplings of
another module of the same inner and outer diameters.
advantageously, the cap 9 and bottom 11 are each
provided with punched out fingers 13 and 15 which interlock
when the couplings are fit together whereby securely joining
adjacent chimney modules together.
As aforesaid, the longitudinal edges of the flue 7
are connected to each other to define a continuous, expansible
lock joint 21.
Referring now to Figs. 3 and 4a, the edges 25 and
27 of the flue are bent back over themselves to form a pair
of oppositely directed U-shaped hooks that are engaged one
inside the other.
Contrary to the joint 23 of the casing 5, the joint
21 of the flue is not locked in a rigid manner by a pair
of abutment edges such as 33, 35 of casing 5 or any other
means. In contrast, the joint 21 is allowed freely to expand
in a circumferential direction whenever the flue is heated,
to prevent radial compression of the insulating material 3
and thus radial pressure applied against the outer casing
5 which is of course heated at a substantially lower tem-
perature due to the material 3 and thus undergoes a substan-
tially smaller expansion.
This in turn prevents the surface of the inner
flue 7 from warping;
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and the lock joint 21 from breakin~, all o~ these struc-
tural damages constituting sure fire hazars for the
building in which the chimney is installed.
Of course, the expansible lock joint 21 can
be made in any other manner, provided it remains expansible
circumferentialy to absorb radial expansion of the
flue when the chimney is in operation.
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