Note: Descriptions are shown in the official language in which they were submitted.
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HIGH-OUPTUT HEATING DEVICE
Field of the invention
[0001] The present invention relates to a new concept
for high-output, multi-fuel, domestic, heating device
comprising a sealed (or almost sealed) heating body whose
operation can be remotely controlled.
[0002] Sealed heating body should be understood as a
heating body whose only communication with the outside
consists of an inlet for primary cold air and an outlet for
burnt gases.
Technological background and state of the art
[0003] In recent years, major efforts have been
undertaken to create "modular" domestic heating devices that
have the same shape, design or covering irrespective of the
fuel used or of the nominal power required. These different
devices are characterised by a combustion chamber (or a
heating body) of specific dimensions for a solid, liquid or
gaseous fuel or for a specified power level. Thus, the rear
wall of the combustion chamber may comprise an intermediate
part with an outlet opening adapted to each predefined
situation (see patents US-B-6,209,535 and EP-B-0 883 782).
[0004] This type of design has in particular allowed the
mass-production manufacturers to achieve productivity gains
and rationalisation of intermediate parts stockholding.
[0005] Another trend observed is that of bringing to the
domestic stove and heater sector the benefits of technological
innovations that allow to increase the comfort of use and the
user-friendliness of these devices. Hence, the Applicant also
proposed a heating device with a double casing for the
circulation of air, having on its front face a plate blocking
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the free space between the two casings and provided with sized
apertures for air inlet and outlet so as to simultaneously
optimise both the temperature and the speed of the outgoing
flow of air (patent application EP-A-1 111 307).
[0006] At the present time, heating devices such as
stoves comprise the hybrid assembly of a combustion chamber,
possibly rationalised as mentioned above, that can for
instance be made of sheet steel, with structural parts and/or
a decorative covering comprising for example elements made of
cast iron, ceramic or even firestone such as oleaginous stone
(steatite, "soapstone"). The fixing of the parts is achieved
by complex and inefficient techniques making use of tie-rods,
throats and putty. This complexity is justified by the need to
guarantee the best possible seal of the combustion chamber in
order to obtain the minimum desired output. Indeed, the
combustion chamber can be considered as a closed prismatic
shape only open on its front face comprising a door, possibly
letting flames be seen through a window, and/or on its upper
face to allow the placing of a cooking plate.
[0007] Apart from the loss of productivity, this method
of assembly has drawbacks associated with the use of putty. In
fact, when the putty dries, it may shrink or present micro-
cracks, which lets air enter the chamber, thus adversely
affecting the output of the device. The presence of putty
makes it difficult to obtain the required seal in accordance
with the various standards in force in different countries
(e.g.: EPA standards in the US).
[0008] Moreover, during transportation of the device
after manufacture, flows of putty may appear on visible
surfaces, which requires the intervention of expensive after-
sales service.
[0009] Lastly, there are numerous licensing standards
for the introduction of the above-mentioned heating devices to
the market, the technical requirements generally varying from
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one country to another (American, French, DIN+, European,
Norwegian etc. standards). It is thus often necessary to make
successive modifications to a given device with a view to meet
licensing regulations in several countries (regulation of the
combustion-air opening, device for guiding the hot air to the
flame, etc.).
[0010] Document DE-A-30 09 251 describes a heating
device for solid fuel whose combustion chamber is defined by
stainless steel sheets in the form of concave flanges, which
are fixed to the outer walls so as to form channels allowing
to lead the secondary air into said chamber, through inlet air
openings made in its upper part. The flanges are arranged at
the back and on both sides of the chamber. The joint at the
front is formed by a grate. Slits for air inlet made at the
bottom of the flanges allow part of the primary air to be
diverted as secondary air. The outer walls making up the main
carrier structure of the stove, and the flanges are provided
with rims that allow to apply the sheets one over the other in
a peripheral area in order to form a lining where these are to
be fixed by welding or screwing. The assembly of the various
walls thus proves difficult and the seal of the combustion
chamber is not guaranteed. The secondary air supply may be
manually or automatically controlled.
[0011] Document WO-A-99 64789 describes a heating device
for solid fuel comprising a control means, associated with
sensors and automatically controlled for instance by a motor,
at the level of three types of air inlet: primary, secondary
and tertiary. The device is provided with a programmable
control unit for selective control of the regulation means so
as to optimise the combustion in different operating
conditions, in particular during the ignition phase, "high"
and "low" running, re-ignition and extinction phases. The
primary air is guided to the furnace at the bottom of the
combustion chamber. The secondary air is guided by a channel
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adjacent to the chamber where it is heated over the furnace,
along the window, so as to reduce soot deposition. Lastly, the
tertiary air is guided to the centre of the chamber by another
channel so as to ensure the complete combustion of the unburnt
gases. The apertures of these air inlets are preferably
regulated by a valve or a damper controlled by an actuator
such as a step motor, controlled by the programmable unit.
[0012] The control unit may be connected to a clock or
to a thermostat. The control parameter on which regulation is
based is the combustion temperature. The different operating
conditions are displayed on a control display unit also
showing indicator lights and push-buttons that allow the user
to select the operating conditions.
[0013] The reaction times to the air-inlet controls in
terms of reached combustion temperature are of the order of
several minutes at least.
Aims of the invention
[0014] The present invention aims to provide a solution
which dispenses with the drawbacks of the state of the art.
[0015] In particular, the invention aims to provide a
heating device designed to allow the achievement of major
productivity gains during the mass-assembly process.
[0016] In addition, the invention aims to provide a
heating device whose combustion chamber is almost perfectly
sealed.
[0017] The invention moreover aims to propose a domestic
heating device that ensures to the user the comfort of
remotely controlling its operation conditions with precision
and automatically.
[0018] Finally, the invention aims to propose a domestic
heating device that has a high degree of flexibility so as to
pass licensing tests in various countries.
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Main characteristic elements of the invention
[0019] A first aspect of the present invention relates
to a multi-fuel heating device comprising:
- a combustion chamber made of weldable sheet metal, preferably
5 steel, obtained by the assembly of a rear wall, two lateral
walls, a lower wall and an upper wall, said chamber having
predetermined standard dimensions depending on the nominal
power required,
- at least one outlet device for the burnt gases connected to
said chamber,
- an outer hood fixed to said chamber, comprising elements such
as plates made of cast iron, ceramic, enamel or firestone,
- a front access door, possibly provided with a window,
connected to the combustion chamber,
characterised in that:
- the combustion chamber forms. the main carrier structure of
the heating device and is made of sheet metal that is folded
and welded so as to be totally sealed, except possibly at the
level of the joint with said door,
- said elements forming the outer hood are fixed to the
combustion chamber without the fixation means passing through
the chamber and without said elements necessarily needing to
be fixed to each other.
[0020] The invention aims at any heating device using
gas of the type with a stack or vent-hole using liquid fuel,
in particular by evaporation under pressure or with
gasification under atmospheric pressure, using wood, coal or
other solid fuel.
[0021] As a particular advantage, the outer hood is
formed by the combustion chamber itself. The sealed feature of
the combustion chamber of the device according to the
invention allows to achieve a very high output, of the order
of even 80% for heating with wood, which is a considerable
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advantage to those skilled in the art and/or to the user
(reduced consumption).
[0022] Preferably, the elements of the hood are fixed to
the combustion chamber with screws, rivets, glue or putty.
[0023] The heating device according to the invention
also comprises a first damper or valve for regulating the
entry of cold external air into the chamber, that can be open
at a position intermediate between a totally closed position
and a totally open position, activated by a remotely
controlled motor, the remote control being a cordless remote
control, preferably infrared or ultrasound. This possibility
of remotely controlling the heating device according to the
invention is not a simple, obvious application by those
skilled in the art of techniques known elsewhere. Its interest
is a direct result of the almost perfect seal of the chamber
and of its very high output. Indeed, it is only under these
conditions that rapid, effective and reproducible control of
the combustion is possible. The reaction time to the remote
control is in fact only a few seconds.
[0024] As an advantage, the above-mentioned remote
control is provided with a thermostat and/or a digital
programmer, and possibly a display means, preferably with
liquid or electroluminescent crystals.
[0025] The opening or closing of the first damper is
advantageously controlled by a timer, the opening or closing
of the first damper may also be operated at a pre-programmed
value by means of a presence detector in a volume, preferably
by an infrared sensor.
[0026] According to a preferred embodiment of the
invention, the heating device comprises a heating duct for the
external air in contact with the combustion chamber, before
entering the latter, said duct terminating in a neck and
opening into the upper part of the chamber near its front
face.
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[0027] According to another preferred embodiment of the
invention, the heating device also comprises a duct provided
with a second damper or valve for bringing the secondary air
from the outside towards the chamber, said damper being
controllable by the user. This additional air supply
advantageously allows to improve the elimination of the solid
particle residues in the smoke, at low operating levels
(slow).
[0028] Another aspect of the present invention relates
to a combustion chamber intended to be incorporated into a
multi-fuel heating device, forming the main carrier structure
of the heating device, only open on its front face and made of
folded and welded sheet metal.
[0029] Advantageously, this combustion chamber has
protrusions that allow to fix external covering elements of
the device such as plates, feet or cooking plates made of cast
iron, ceramic, enamel or firestone.
Brief description of the figures
[0030] Figure 1 shows a perspective view of the
combustion chamber of the heating device according to the
present invention.
[0031] Figure 2 schematically shows the air circuit of a
heating device according to a first embodiment of the present
invention.
[0032] Figure 3 schematically shows the air circuit of a
heating device according to a second embodiment of the
invention.
Description of a preferred embodiment of the invention
[0033] As described in Figure 1, the present invention
proposes a combustion chamber 1 made of folded and welded
sheet steel 2. Alternatively, a different weldable metal could
be used. In this way, a combustion chamber is made in a
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prismatic shape, constructed in accordance with the principle
of the "thermos ". The only aperture provided toward the area
to be heated is that allowing the placement of a door 3, for
instance also in steel or in decorative cast iron, on the
front face.
[0034] The principle of a closed combustion chamber
according to the invention is a great advantage in as much
that the latter may be made in an almost perfectly sealed
manner. Slight losses of seal may in fact inevitably occur at
the door joint. Therefore, an exceptionally high output is
obtained (of the order of. 80%). Moreover, the stove or the
heating device may comprise only said combustion chamber and
have compact dimensions, solely depending on the nominal power
desired.
[0035] Advantageously, the heating device described
above can be extended by structural elements upwards 4' or
downwards 4", for instance. The protrusions downwards 4" may
allow the fixation of feet. These elements may in general
allow to attach decorative parts 20, such as for instance
plates made of cast iron, enamel or ceramic. The fixation
means are all fixation means known to those skilled in the
art, such as screws, glue, putty, rivets, etc. According to
the invention, it is not necessary for the decorative elements
to be fixed or assembled to each other, which avoids the
losses of productivity associated with such generally
complicated fixing or assembly. The fixation of decorative
elements 20 to the steel combustion chamber are designed so as
to respect the seal of the chamber. Therefore, there will not
in any event be fixings perforating the wall of the combustion
chamber.
[0036] The combustion chamber according to the invention
will of course benefit from the advantageous features
described in the American patent US-B-6,209,535, such as for
instance an interchangeable rear face depending on the fuel
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and/or the power. This rear face will advantageously include
an air inlet opening and an opening for the outlet of the
burnt gases. The latter opening 30 may also be provided in the
upper face of the chamber. The fuel used may be solid (wood,
coal), liquid (diesel) or gaseous (natural gas, propane). A
grate or a valve is provided at the bottom of the chamber in
order to generate a small additional air inlet allowing to
help with start-up ("ignition booster") which is optional for
wood but indispensable for coal.
[0037] As an advantage, the combustion chamber also has
a wall 5 that allows a heating duct 6 to be created for the
incoming air, as schematically shown in Figure 2. At the
outlet 7 from this duct, which has a neck so as to create a
venturi effect and to give the heated air increased speed
(acceleration), the latter is injected into the chamber
itself, at the level of its upper part 10, along the door and
more precisely along the window 9 inserted in the latter, if
there is one. It is not necessary for the air entering the
chamber to be "cold": it is the difference between the
temperature of this heated air and the temperature reigning in
the chamber which causes the suction movement of the air in
the chamber (as does the draw of the stack). This difference
in temperature simply has to be sufficient.
[0038] According to the preferred embodiment described
here, the temperature of the heated air when it enters the
chamber is about 30040.
[0039] A first part of the heated air, moving at a
certain speed, flows down the window to the bottom of the
chamber 11 and feeds the combustion by acting as primary air.
A second part of the heated air allows volatile unburnt or
partly burnt materials to be ignited in the upper part 10 of
the chamber, thus acting as secondary air. The fact of heating
the air before it enters the combustion chamber prevents the
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chamber from cooling down and thus hinders the creation of
unburnt volatile materials.
[040] An important advantage of the invention comprises
the seal of the combustion chamber. As a result, an extremely
5 precise control of the operating conditions can be carried
out. For instance, a damper or valve for the air inlet 15
situated at the back of the chamber can be automatically
controlled. It is fixed to a remotely controlled, motorised
device 16, preferably by infrared or ultrasound 17 means.
10 Thus, the user may adjust the combustion operation without
getting out of his seat, for example, depending on the desired
heat level or appearance. The remote control 17 allows, by
means of a push-button, to adopt an intermediate operation
level between a maximum setting corresponding to the maximum
opening of the air inlet damper and a minimum setting
corresponding to the minimum opening of said damper. The
reaction of the combustion to the remote control is very
rapid, even instantaneous, thanks to the excellent seal of the
chamber. The user may thus advantageously use the cordless
remote control to watch the instantaneous (or almost
instantaneous) response to the command of the combustion,
namely a change in the appearance of the flame. In that
respect, it would be neither of great use nor convenient to
use a control located on the heating device, some distance
being necessary for this view. Moreover, this type of heating
device allows continuous heating (> 10 hours with wood).
[0040] In an alternative embodiment, the setting or
turning off can also be provided for at set hours, controlled
by a programmer/timer or even the lighting of the stove by the
detection with infrared or other of people within a given
volume.
[0042] Thus, at maximum operation, there is an excess of
(sub-stoichiometric) combustion air with the presence of blue
flames. At the other extreme, at minimum operation, the system
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is in sub-stoichiometric conditions with the presence of
yellow-orange flames, of a more or less "feeble" appearance.
The shortage of air in the latter case is such that there are
no longer enough flames at the bottom of the chamber, yellow
flames still being present at the top of the chamber, as well
as small flames that "trickle down" along the vertical edges
of the window. The latter are of course fed by the very slight
inlets of air at the level of the front door.
[043] When the air supply is completely cut off, the
air already present in the heating duct loses its speed and
forms a "plug." The lack of air in the chamber also causes a
build-up in unburnt or partially burnt gases. The
configuration of the heating duct, in particular its
thickness, has been studied so as to avoid any explosion in
the chamber when the air supply from the outside is suddenly
restored. In fact, in this case, the obstructing plug is
gradually eliminated and the flames reappear only gradually in
the combustion chamber (5 to 10 seconds after the opening of
the valve).
[0044] In order to further improve the combustion
cleanliness during slow operation and to eliminate the last
residues of solid particles in the smoke, the combustion
chamber according to the invention may be provided with an
additional duct 6' for secondary air adduction (Figure 3).
This duct 6' will ideally be provided with a control device 18
for the flow of air allowed into the combustion chamber that
can be operated from the outside by the user. Said device 18
can of course be in a completely closed position during medium
or high level operation.
[0045] At high levels of combustion, the temperature
reached inside the sealed combustion chamber and the high
temperature of the primary and secondary air allow a maximum
amount of the solid particles in the smoke to be burnt. In
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this case, the quantity of secondary air supplied by the
existing air valve 15 is sufficient.
[0046] At lower levels of combustion (slow), the
temperature inside the sealed combustion chamber is lower and
the quantity of secondary air passing through the air valve is
reduced, given that this air inlet is itself reduced so as to
achieve slow operation. Although this type of operation
nevertheless allows the fire to burn clean thanks to the seal
of the combustion chamber and to the large pre-heating surface
for the incoming air, it is thus possible to improve it by
adduction of an additional amount of secondary air only, as
shown in Figure 3.
[0047] As regards the licensing tests to be performed
for this device, there will be advantageously provided,
mutatis mutandis, an adequate opening range of the damper or
valve 15 as well as set positions for the latter (with or
without stop notches) corresponding to the different running
levels to be tested so as to satisfy the different
requirements of the various standards in force. Another
advantage of the invention will of course also reside in the
possibility of controlling these tests by means of the above-
mentioned remote control 17.
