CA2498289C - High-output heating device - Google Patents

Abstract

The invention concerns a multiple-fuel heating apparatus characterized in that: the combustion chamber (1) forms the main support structure of the heating apparatus and is made of sheet metal bent and welded (2) so as to be completely sealed, optionally except at the joint with said door; the elements (20) forming the outer cover are fixed to the combustion chamber, the fixing elements not passing through the chamber and said elements not being necessarily fixed together.

Description

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 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 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 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.

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 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.

[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 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 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 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 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 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.

Claims (12)

1. Multi-fuel heating device comprising:
- a combustion chamber (1) comprising a main carrier structure of said device, of folded and weldable steel sheet (2) having a welded assembly of a rear wall, two lateral walls, a lower wall and an upper wall, said chamber having predetermined standard dimensions depending on a nominal power required;
- a cold air inlet device comprising a first damper or valve (15) for intaking cold external air, the first damper or valve being openable to a plurality of positions intermediate a fully closed position and a fully open position;
- a front access door (3) having a window (9) connected to the combustion chamber;
- a primary air duct (6) isolated from the combustion chamber other than externally contacting the lateral walls, the rear wall and the upper wall of the combustion chamber and having a first end at the cold air inlet device and terminating at a second end in a neck creating a venturi effect; the neck opening at an upper part of the combustion chamber proximate a top of the window (9);
- at least one outlet device (30) for burnt gases connected to the combustion chamber;
- a motor (16) controlled by a cordless remote control (17) for activating the first damper or valve (15);
wherein all the external air is intaken through the first damper or valve (15) of the cold air inlet device, heated in the primary air duct (6) upon contact with the walls of the combustion chamber and then directed downwards into the combustion chamber proximate the top of the window (9), and, wherein the combustion chamber (1) is sealed except at a level of the first damper or valve (15) for intaking cold air, at the outlet device (30) for burnt gases, and at a joint for the door.

2. Heating device according to Claim 1, further comprising plates made of a material selected from the group consisting of cast iron, ceramic, enamel and firestone, said plates forming an outer hood fixed to the combustion chamber by fixation means so as to maintain the seal of the chamber.

3. Heating device according to Claim 2, wherein the plates of the hood are fixed to the combustion chamber by fixation means selected from the group consisting of screws, rivets, glue and putty.

4. Heating device according to Claim 1, wherein the cordless remote control (17) is an infrared or ultrasound remote control.

5. Heating device according to Claim 1, wherein the opening or closing of the first damper (15) is controlled by a timer.

6. Heating device according to Claim 1, wherein the opening or closing of the first damper (15) is carried out at a pre-programmed value by an infrared sensor.

7. Heating device according to Claim 1, further comprising a duct (6') provided with a second damper or valve (18) to guide secondary outside air towards the chamber (1), said second damper or valve (18) being controllable by a user.

8. Heating device according to Claim 1, wherein the remote control (17) is provided with a thermostat, a digital programmer and display means or is provided with a thermostat and display means or is provided with a digital programmer and display means.

9. Heating device according to Claim 2, wherein the combustion chamber has protrusions (4', 4") that allow external covering elements (20) to be attached to the device.

10. Heating device according to Claim 1, wherein the heating device uses gas and is of the type with a stack or vent-hole, uses liquid fuel by evaporation under pressure, or, with gasification under atmospheric pressure, uses wood, coal or another solid fuel.

11. Heating device according to Claim 8, wherein the display means comprises liquid or electroluminescent crystals.

12. Heating device according to Claim 9, wherein the external covering elements (20) comprise plates, feet or cooking plates made of a material selected from the group consisting of cast iron, ceramic, enamel and firestone.