Heating stoves or heating ovens that include a heat exchanger as well as a combustion chamber have been known for some considerable time. They include, for example, tiled stoves and metal stoves whose walls are heated by the combustion gasses.

Channels of air are arranged in the walls, through which air is introduced for heating prior to it being supplied to the surrounding space.

Current heating stoves or ovens are commonly built piece-by-piece or put together on site and then bricked or welded to form one unit when they are made ready for use. Assembly and later disassembly and/or repair of similar structures consequently involves a great deal of work that requires a specialist craftsman.

In modern, efficient heating stoves, the combustion takes place under over- pressure, in contrast to traditional stoves. Forced air is introduced into the combustion space, for example, by means of a fan or similar. Because of this, it is clear that the requirements for the tight sealing of the stove increase.

Using different materials that are fixed to one another introduces problems when the changes in thermal expansion vary between the material, which results in the risk of formation of gaps and associated leaks.

It is the objective of the present invention to reduce or overcome the problems and disadvantages named above and to achieve a heating stove that can easily be assembled and disassembled plus, when needed, be partially replaced for upgrading to newer, more efficient technology, for example.

This objective is achieved with a heating stove that is first named above and that has the characteristics that are defined in the attached independent claim.

Further characteristics and advantages of the invention will be evident from the dependent claims and from the following detailed description of one preferred embodiment of the invention that constitutes one example and is thus not limiting for the scope of protection of the invention. To facilitate understanding, references are included to the attached drawings in the text, in which equivalent or similar parts have been given the same reference mark.

Fig. 1 shows schematically a partially cut-away view from the front of a heating stove according to one embodiment of the present invention.

Fig. 2 shows schematically a side view in cross-section of the embodiment according to Fig. 1.

Figs 3 and 4 show components of the embodiment according to Figs. 1 and 2.

With reference to the figures, a preferred embodiment of the present invention is shown. A heating stove for burning pellets of wood fibre is built up of modules removably arranged on one another.

A first module 10 includes a fan housing 11 and a fan 12 capable of achieving a flow of air.

A second module 20 is arranged on the first module 10 and includes a combustion chamber 21. The combustion chamber 21 is a radially demarcated upright cylindrical combustion space made from stainless steel plate 22. A heat-resistant insulating ceramic material 23 is arranged on the outside of the demarcating plate 22, and an outer casing 24 of steel plate is arranged on the outside of the insulating material 23.

An access door 25 is arranged in the front side of the combustion chamber 21.

The door can advantageously be provided with glass, as in the example shown. The glass is intended to increase the feeling of warmth and comfort by exposing a view of the burning flames.

Grooves 14 to guide and accommodate the second module 20 are arranged in the fan housing 11, which in this preferred embodiment is executed in grey cast iron by casting.

In addition, a shaped sealing material can advantageously be arranged in the groove to ensure a tight seal between the two hard materials where they meet.

At least one outlet 15 is also arranged in the fan housing 11 for the air-flow forced by the fan. Outlet 15 is so arranged that its openings coincide with the inlet to the channels in the second module 20 to guide the air to the combustion chamber, partly as primary air at the burning fire bed and partly as secondary air to the fumes above the bed.

The channels in the combustion chamber are made by forming grooves in the insulating material 23 that open to the demarcating plate 22 of the chamber 21. Air is introduced to the combustion chamber in desired locations by arranging holes in the demarcating plate 22.

According to Fig. 2, it is evident that the bed of pellets is intended to lie in a tray 26 that also demarcates the lower limit of the combustion chamber. The bottom of the tray is perforated and the tray 16 rests along the edge of a collar 16 that projects out from the fan housing 11.

An ignition unit 13 is arranged in the fan housing 11 directly under the bottom of the said tray 26. The ignition unit has an electric spiral that ignites the fuel in the tray when heated.

In the upward direction, combustion chamber 21 opens to a third module 30.

The third module receives the fumes from the combustion chamber for recycling the thermal energy. The heat exchange can take place as gas-to-gas or gas-to-liquid. Lops with separate channels for fumes and air are indicated in the embodiment shown.

A fourth module, the top module 40, is arranged on the heat exchange module 30. This can even be fully integrated with the heat exchange module 30. The top module constitutes a lid to the heat exchange module and it collects together the fumes to an outlet channel 41 for transport onwards to a chimney, for example. The top module can advantageously be made by casting, whereby grooves for directing the accommodation of the plate edges of the heat exchange module can be easily produced.

To ensure a gas-tight seal between the combustion chamber module 20 and the heat exchange module 30, a sealing joining device 50 can advantageously be arranged. In the embodiment shown, the joining device has an essentially rectangular plate-like form that on its main surfaces has module-specific grooves 51 for directing the accommodation of the combustion chamber module 20 and the heat exchange module 30 respectively. In addition, the joining device 50 has an opening 52 on the inner side of the innermost demarcations for allowing fumes to pass through from module 20 to module 30.

The plate made with grooves can advantageously be produced by casting a chrome alloy grey iron material.

A sealing material, preferably a ceramic material, can advantageously be brought in groove 51 between the joining device 50 and the plate edges (22; 24; 31 ; 32).

When the modules are on site, that are assembled in a gas-tight yet nevertheless removable manner so that they can later be able to be separated should the need arise for upgrading or replacement of individual modules. According to the present embodiment, this is solved by the modules being pressed against one another and clamped together by means of pull rods 60 that extend between the two outermost modules.

The pull rods 60 are equipped with threaded free-ends 61 that link together threaded nuts 62 that press against flanges 17,42 at the outer clamped modules and pull the modules together to one gas-tight unit. To allow variations in length due to thermal effects, sprung plates 63 are arranged between at least one nut 62 and the associated flange 17 per pull rod.

A variation in length can thus be allowed with a retained pretension within acceptable limits, i. e. without the pretensioning being so great that cracks or other damage

occurs on the modules. In the present embodiment, the pull rods are approximately 1000 mm and the expected variations in dimensions approximately 5 mm.

The modules are brought together as one unit by means of removable flexible pre-tensioned clamping joints. In the example shown, four pull rods distributed around the column of the modules and acting between the two outermost modules constitute the joint. In the example shown, the sprung plates are plane plates that are shaped as cups.

Each module, for example, the combustion chamber module, has connecting surfaces with specific profiles. This standardisation allows both industrial manufacture of the modules and replacement on a module basis if defects arise or when more efficient technology is introduced.

The temperatures that can be expected at different levels in the heating stove determine the choice of materials of its components. The following rough distribution can be given. Approximately 750 °C in pellet tray 26, approximately 900-1000 °C in the combustible gases above the bed, and approximately 200 °C after the heat exchanger. As such, the sections in the heating stove will alternate from room temperature between periods of heating to 1000 °C during use.