EP2467644B1 - Wood pellet stove for power outputs of down to less than 1 kw - Google Patents

Description

The burning of small portioned and therefore granular firewood, such as wood pellets, wood chips, small pieces of wood or dried corn proves to be energetically favorable and convenient to use. It does not have large and unwieldy pieces of wood to be transported and stored and also no large logs to be fed to the fire. The dosing of the fire power down to a low value is made possible today by a special fuel feed device for granular fuel. This makes it possible to ensure performances down to less than 1 kW. It is worked with a arranged in a pipe screw conveyor for the conveyance of the granular material. The central screw axis tube of the screw conveyor, on the outer wall of the screw winding is mounted and with which together the screw conveyor is rotatably mounted in the tube, thereby filling at least a quarter of the pipe diameter. This screw axis tube runs up as a cone in a tip. Above the snail is a circular grid with central round hole and air supply openings in the outer area of the grate. The hole is dimensioned slightly smaller than the diameter of the auger and from its edge extends a flared wall as a sliding wall for the kiln to be conveyed downwards, which runs approximately or exactly parallel to the cone of the upper end of the screw axis. With such or a similar conveyor, a wood pellet stove can operate largely automatically, even at very low power of less than 1 kW ensures that the fire does not go out. Also the Ash removal is ensured and it is prevented that the fire in the feed stream of the fuel vorfrisst.

Such a wood pellet stove is therefore an efficient heating, and it is preferably placed in the living room. But here he should meet even more technical requirements. Previously known wood pellet stoves can only be placed next to a wall if this is, for example, a concrete wall, that is incombustible. However, if the wall or its lining is flammable, they must be installed freestanding for fire protection reasons. It must then be complied with a prescribed distance to the rear wall. This is a technical limitation that often looks unattractive. In addition, one would like to achieve not only a heat output in a Holzpelletofen, but he should also exude cosiness and blend in harmoniously with the furniture landscape of a living room. In addition, one finds in many living rooms next to the dining area a seating area. If you sit here like there, you want to be able to see the fire. But this is not possible with the existing wood pellet oven designs. The fire is visible only within a limited viewing angle. The direct heat radiation of the fire can not be aligned with the current whereabouts of the residents.

For example, we know the document JP 60 117003 WO 02/56066, which discloses a wood pellet oven with feeder for automatic metering of wood pellets from a pellet hopper associated with the oven, the pellet hopper with feeder and grate being housed in a stationary base and the combustor being housed in an upper furnace part.

From the document AT 410 364 We also know a wood pellet oven with feeding device in which the burner bottom is rotatably supported via a bearing on the supply device. The upper part of the furnace and the supply device but are arranged stationary.

It is therefore the object of the present invention to provide a wood pellet oven indicate, which has a combustion chamber whose open side can be aligned in different directions, and the gap-free closed with a rear wall is connectable.

The object is achieved by a wood pellet furnace according to claim 1.

Based on the drawings, this wood pellet stove will be introduced and described below, explaining its structure and function.

Figur 1:

Den Holzpellet-Ofen bestehend aus Unterteil mit den Anschlüssen und darauf aufgesetztem Oberteil;

Figur 2:

Den Holzpellet-Ofen bestehend aus Unterteil und dem darauf verschwenkbar gelagerten Oberteil, vor einer Rückwand aufgestellt;

Figur 3:

Den Holzpellet-Ofen mit Unterteil und davon abgehobenem Oberteil mit der Drehscheibe für die schwenkbare Lagerung des Oberteils;

Figur 4:

Die Drehscheibe nach Figur 3 in vergrösserter Darstellung gezeigt;

Figur 5:

Die Zufuhrvorrichtung mit dem am oberen Ende angeordneten Rost in einem Längsschnitt gesehen;

Figur 6:

Einen Querschnitt durch die Förderschnecke, von oben gesehen;

Figur 7:

Die gesamte Förderschnecke von der Seite her gesehen, in einem Längsschnitt dargestellt;

Figur 8:

Den Unter- und Oberteil des Ofens mit demontierten Verkleidungsteilen.

It shows:

FIG. 1:

The wood pellet stove consisting of base with the connections and top part mounted thereon;

FIG. 2:

The wood pellet stove consisting of lower part and the upper part mounted pivotally on it, placed in front of a rear wall;

FIG. 3:

The wood pellet stove with base and raised top with the turntable for the pivotal mounting of the upper part;

FIG. 4:

The turntable after FIG. 3 shown in an enlarged view;

FIG. 5:

The supply device with the arranged at the upper end grate seen in a longitudinal section;

FIG. 6:

A cross section through the auger, seen from above;

FIG. 7:

The entire screw conveyor seen from the side, shown in a longitudinal section;

FIG. 8:

The bottom and top of the stove with disassembled trim parts.

The FIG. 1 shows the wood pellet stove in an overall view. It consists of a lower part 20 and pivotally mounted on top 21. The front of the upper part 21 is made in heat-resistant glass and gives the Look into the combustion chamber, which is not shown here. The lower part 20 contains the bunker for the wood pellets and the feeder for the metered feeding of wood pellets on the grid. The lower part 20 remains cold during operation and is designed here as orthorhombic body. All ports 34-38 are connected to the furnace at the rear of the base 20, namely the fresh air supply pipe 36, the flue gas exhaust pipe 37, the pellets delivery electric connections 38 and the supply air supply fan and if appropriate, the flue gas path discharge, and any water connections 34, 35 for a circuit in the casing of the combustion chamber for receiving and removing heat to a central heating system. In a further expansion can also be an additional, opening on the rear pipe for the pellet supply be present, so then these pellets can be refilled from a separate room in the reservoir inside the lower part 20 of the furnace, which otherwise happens from the front through Removing the front cover on the lower part 20. Around the lower part 20 along the rear edge of a shutter 39 is arranged, which forms a clean conclusion to the rear wall, to which the oven is placed at a distance. This panel 39 forms a bent to a U-shape sheet metal strip, so that the aperture 39 can be plugged from above to the back of the lower, cold furnace part 20. So far, a stove had to be installed for fire police reasons always with a prescribed distance from the wall in front of the same, because he is so hot. In this oven, however, the lower part 20 remains cold and can therefore easily form a trim 39 with a clean conclusion with the rear wall, so that a disturbing gap between the oven and the rear wall is omitted, which is aesthetically much tidier.

In FIG. 2 the oven is shown mounted in front of a rear wall 40. The upper part 21 of this wood pellet opening is pivoted as a special feature relative to the lower part 20 and pivoted here from above viewed at about 20 ° in the counterclockwise direction relative to the lower part 20. With the rear wall 40 of the lower part 21 of the furnace via a shutter 39, which closes the gap between the lower part 20 and rear wall 40, a clean conclusion. The pivoting range of the upper part 21 on the lower part 20 is approximately ± 25 °, ie a total of about 50 °, but depending on the design of the intermediate turntable also be full 180 °, so so that the upper part 21 can be directed with its glass front, which releases the view into the combustion chamber, all the way to the left or right.

The FIG. 3 shows this wood pellet stove with base 20 and lifted off top 21 with a view of the hub 22 for the pivotal mounting of the upper part 21. This hub 22 is constructed on top of the lower part 20 and its structure is based on the FIG. 4 described in more detail. It consists of a base plate 23 with a central hole 24, an intermediate plate 25 with also a central hole 24 which is pivotable about the same. This washer 25 has peripherally arranged holes 26, in each of which a ball 27 is caught. Finally, a cover plate 28 which annularly surrounds the central hole 24 around a large part of the circumference, resting on these balls 27 so that it is pivotable about the central hole 24 by rolling on the balls 27. The balls 27 roll inside the holes 26 of the washer 25 in which they are caught, and thus roll on the base plate 23 from. The intermediate plate 25 pivots with the rolling balls 27 in their holes, always by half the extent of the pivoting of the cover plate 28. This ball-mounted pivoting of the upper part 21 of the wood pellet stove on its lower part 20 ensures a low-friction running and the balls 27 wear the load of the furnace top 21, which is mounted on the cover plate 28. The hub 22 leaves a curved slot 42 open, through which the flue gas duct 37, and possibly the lines 34,35 are performed for the water cycle, and the hole 42 is large enough that it can be pivoted with the turntable to these stationary lines. Another such slot 43 is used for receiving the fresh air line. Down in hole 24 is the actual grate 1, to which the wood pellets are automatically fed, as shown below.

This feeder is in FIG. 5 shown with the arranged at the upper end grate 1 shown in a longitudinal section, for granular kiln for a kiln designed for performances down to less than 1 KW. The kiln can consist of wood pellets, but also of wood chips, small pieces of wood or dried corn or other grains. The grate 1 of the furnace cooperates with the feed device, and this is equipped with a screw conveyor 2. The screw conveyor 2 is arranged in the example shown perpendicular to the grate surface and the central screw axis tube 3, on the outer wall 4, the screw 5 is mounted and with which together the screw conveyor 2 is rotatably mounted in the conveyor tube 8, fills a considerable part of the conveyor tube 8, which the whole screw conveyor 2 encloses. The conveyor tube 8 with the screw conveyor 2 can also be arranged obliquely to the perpendicular. It is then achieved on the bottom of additional friction of the fuel with the delivery pipe 8, which is beneficial to the promotion. In the example shown, the tube diameter of the screw axis tube 3 measures one third of the screw diameter or the tube diameter, and measures, for example, 60 mm. The diameter of the screw axis tube 3 should be at least a quarter of the screw conveyor diameter, because thus also a sufficient torque on the actual screw 2 and on the helical to the screw axis tube 3 wound smoothest possible conveying surface 5 are transmitted. On the conveying surface 5 of the screw 2 here is a single wood pellet 18 drawn to give an approximate size comparison. This screw axis tube 3 runs up as a cone 10 in a tip, wherein above the screw 2, the grate 1 is arranged horizontally with a central circular hole 6. It fits exactly on the upper end of the auger axle tube 8 and is placed on this.

The grate 1 is preferably circular as shown and penetrated in the outer region with air supply openings 7. The circular hole 6 in the grate 1 measures approximately half of the delivery pipe diameter. From this circular hole 6 includes a downwardly projecting, funnel-shaped edge 9, which opens as a funnel down. The funnel wall runs almost or exactly parallel to the cone 10 on the worm axis tube 3 As shown, the cone 10 encloses an acute angle with the running direction of the funnel inner wall, the angle tip being at the top. This angle may only be very small, otherwise a jamming of the fuel in the area between the cone 10 and the funnel inner wall is provoked. The actual screw 2 or its winding conveying surface 5 terminates with an approximately perpendicular to the grate surface extension 11. The outer side of the extension with respect to the axis of rotation adjoins flush with the inner edge of the hole 6. This auger 2 as shown here rotates clockwise in operation as seen from above. Of course, it could also be designed to boost in a counterclockwise direction. The firing material to be conveyed remains approximately at the same point in relation to its rotational position in the conveying tube 8, and the conveying surface 5 of the screw 2 slides under the kiln, being lifted up in the conveying tube 8, until finally at the height of the hole 6 arrives. Important for a reliable conveyance of the kiln by the auger also proves that the inside of the tube 8 is equipped with a plurality of preferably axially extending plateaus or grooves 14, on which the auger turns past with a minimum distance, and between the plateaus or grooves a distance of the height of the plateaus or grooves to the inner wall of the tube 8 leaves open. For the same purpose, the inner wall of the tube 8 may also be provided with a rough surface.

However, the screw 2 rotates only very slowly, with a rotational speed of less than 1 U / min ^-1 . Once at the top, the kiln is captured by the extension 11 and pushed clockwise as seen from above. Where the extension almost touches the edge of hole 6, its absolute speed is only about 1.5-2.0 mm / s. By this slow rotation of the extension 11 but it is ensured that the voraneschobenen parts of the fuel due to the forces wander radially outward and are finally pushed onto the area 12 of the grate surface 1. This area, a concentric ring, which adjoins immediately to the hole 6 in the grate 1, is free of ventilation holes 7. Accordingly, burn the parts of the fuel there heavy and must first be further pushed radially outward. This takes place at the next round of the Fortsatzes 11, if from the same again parts of kiln are pushed a little bit on the grate surface. In this way, the kiln parts are moved every minute, handling handling of the extension 11, very slowly on the grate and finally on the fire zone, which is formed by that area 13, which is equipped with air holes 7. The diameter of the whole grate 1 is about twice the diameter of the conveyor tube 8. So if this measures 60mm, then the grate 1 measures about 120mm in diameter. Due to the gentle and continuous supply of fresh fuel a nice, high and regular flame pattern on the grate 1 is achieved, and no flickering, technically effective flames.

In FIG. 6 If one sees the screw conveyor and the delivery pipe 8 in a cross section. Here you can see the grooves or the elevations 14 on the inside of the conveying tube 8, and a segment of the actual screw, 2 with its outer edge just past these elevations 14. 1. The kiln parts find at these ridges or grooves a backing, which helps avoid that they rotate with the screw conveyor 2. The rotation of the screw conveyor 2, which slides under the kiln, yes causes a force component which points radially outwards. Accordingly, the firing material is pressed against the inner wall of the conveying tube 8 and finds a hold on the elevations. If the outermost parts of the fuel are kept there, they keep the parts adjacent to the inside and these the more adjacent inside, etc., so that co-rotation of the Brenngutstücke is effectively avoided, regardless of whether the Brenngut of wood pellets, from wood chips, from small Pieces of wood or dried corn kernels or the like.

The FIG. 7 shows the screw conveyor 2 in its entire height. It measures between 200mm to 800mm in height and between 55mm and 85mm in diameter. The auger axle tube 3 measures one-quarter to a little over one-third of the diameter in diameter, and the pitch of the auger per revolution is about one-half auger diameter. Down the conveyor pipe 8 can be completely in a pile of kiln parts, or in a box 15, the of above or over, for example, an inclined surface 16 can be charged as Brennüttgosse with fuel. The conveying tube 8 is open at the bottom on one side, and through this opening 17 in the conveying tube 8 trickle the kiln pieces, in the example shown cylindrical wood pellets, the screw 2 after.

The kiln feed device for such wood stoves for powers of less than 1 kW is equipped with an electric motor which drives the screw 2 via a reduction gear. Depending on the voltage-dependent control of the electric motor, the rotational speed of the screw conveyor 2 can be adjusted from 0.5 to 2 revolutions per minute and thus the supply amount of fuel per time and thus the heating power can be regulated.

The FIG. 8 shows the lower and upper part of the furnace with disassembled trim parts 29-32. The oven is constructed in such a way that it can be assembled on site without the use of tools. Only the inner structure of the lower part 20 and upper part 21 is factory assembled together, where also wherever possible plug, hooking and sliding connections are realized to get along as possible without screws. The combustion chamber 19 is enclosed on its sides and the back of fireclay bricks or of a sheet-metal hollow body 41. Thus, the generated heat can be supplied via a water cycle to a central heating. The side parts 31,32 are preferably carried out in sheet metal, but instead of sheet metal, other materials can be used, such as stone slabs, wood or plastic plates or plates made of other materials. These are then provided on one side with hooks 33 so that they can be hung on corresponding eyelets or slots on the lower part 20 of the furnace. The windscreen 29 to the combustion chamber 19 is made of temperature-resistant glass and can also be hooked by means of hooks 33 on the upper part 21 of the furnace.

The FIG. 9 shows a special detail of the kiln feed device. The ash often clumps into a structure and is then distributed irregularly on the grate. If the furnace is equipped with an ignition element for an automatic ignition of the burning material, it may cause an ash accumulation in front of the ignition element, which impairs or prevents its function. It produces larger clumps of ash, which soon exhaust the volume in the ash catcher. The feeder after FIG. 9 fixes these problems by continuously crushing the ash structure during operation and ensuring that the ash is distributed evenly on the grate, preventing ashes from accumulating in front of a mounted ignition element. For this purpose, a steel bracket 49 which extends from the upper end of the auger shaft further upwards and thus first forms a screw conveyor axially extending portion 50, and then via an arc or here radially outwardly extending central portion 51 in a to the axial Section 50 parallel outer section 52 leads. The lower end 53 of this outer portion 52 terminates just above the grate surface, ideally about 8mm above it. Depending on the size of the grate and the nature of the pellets, the distance may vary between 4mm to 12mm. Now, when the auger rotates, for example, at a speed of less than 1 Umin ^-1 , so goes this outer bracket portion 52 with its lower end over the grate and through the ash lying thereon. As a result, the ash structure is plowed and crumbled, so that a fine, homogeneous ash layer remains on the grate. This is gradually pushed by the nachgestossene from the middle of the grate firing material around the outer edge of the grate of this and falls down into the ash container. Because the ashes become very fine and homogeneous as a result of their plowing through, less total volume is produced in the ash catcher. Obliquely inclined towards the grate and peripheral to this an ignition element 54 is arranged here. The tip 55 of the ignition element 54 remains constantly free by the movement of the steel bracket 49 and there is no threat of clogging or ash accumulation in front of the tip 55 of the ignition element 54 and thus no impairment of its function.

The FIG. 10 shows this kiln feed device with the steel bracket 49 shown in a longitudinal section. In this illustration, it can be seen that the outer portion 52 of the bracket 49 is above the outer third of the radius of the grate 1 and its end over the grate surface, in detail about 8mm above the grate surface. The tip 55 of the ignition element 54 is located close to the past rotating outer portion 52 of the bracket 49 and this area is therefore kept free of ash or cyclically.

The kiln feed device for such wood stoves for powers of less than 1 kW is equipped with an electric motor which drives the screw 2 via a reduction gear. Depending on the voltage-dependent control of the electric motor, the rotational speed of the screw conveyor 2 can be adjusted from 0.5 to 2 revolutions per minute and thus the supply amount of fuel per time and thus the heating power can be regulated. Overall, the steel strap offers the advantage that the ash on the grate 1 is uniformly distributed, the ash quality is finer and thus less volume is produced, and the ash falls evenly from the outer edge of the grate down on this fuel feed device. Furthermore, it is reliably avoided that an ash stowage can build up in front of the ignition element, and this ensures that the furnace can be operated for a long time without any maintenance. The ash finally falls evenly over the outer edge of the grate and the ash quality generally becomes finer and firmer, resulting in less volume.

Claims (12)

1. Wood pellet stove with a pellet hopper, comprising a feed device (2) for automatically adding wood pellets from the pellet hopper, and with a stationary lower part (20) and with an upper part (21), wherein the pellet hopper with the feed device (2) and a grate (1) is accommodated in a stationary lower part (20), which does not become hot during operation, and the burning chamber (19) is accommodated in an upper stove part (21), characterised in that the upper stove part (21) is mounted on the lower stove part (20) by means of a turntable (22) so that it can swivel relative to the lower, stationary stove part (20).
2. Wood pellet stove according to claim 1, characterised in that the turntable (22) between the lower stove part (20) and the upper stove part (21) has a central hole (24) for receiving the grate (1) and consists of a bottom disc (23), an intermediate disc (26) having holes (26) and balls (27) which are trapped therein and rest on the bottom disc (23), and a top disc (28) which rests on the balls (27) and supports the upper part (21).
3. Wood pellet stove according to claim 1, characterised in that the turntable (22) has two curved elongate holes (42, 43), each having a constant radius, which are intended for the passage of the flue gas and of the water pipes from the sheet metal body of the burning chamber in the upper stove part (21) into the lower part (20), and an elongate hole (43) for the supply of fresh air which leads from the lower stove part (20) into the burning space.
4. Wood pellet stove according to one of the preceding claims, characterised in that the lining of the lower stove part (20) and upper stove part (21) consists of plug-in, push-in or hook-on parts (29-32), so that the stove lining can be installed and dismantled or replaced without the need for tools.
5. Wood pellet stove according to claim 4, characterised in that the plug-in or hook-on parts (29-32) are steel panels, stone slabs, wood panels, fibre cement panels, plastic panels or are made of high temperature resistant glass.
6. Wood pellet stove according to one of the preceding claims, characterised in that the lower stove part (20), which does not become hot, includes on its rear side a bezel (39) for gap-free connection between the rear side of the lower stove part (20) and a wall (41) running behind the latter.
7. Wood pellet stove according to claim 6, characterised in that the bezel (39) forms a sheet metal strip which is bent into a U-shape, so that the bezel (39) can be placed from above onto the rear side of the lower stove part (20), which does not become hot.
8. Wood pellet stove according to one of the preceding claims, characterised in that the burning chamber of the upper stove part is equipped with a sheet metal hollow body (41).
9. Wood pellet stove according to one of the preceding claims, characterised in that the feed device (2) is a conveyor screw (2) and the spindle of the conveyor screw (2) runs out at the top into a steel bracket (49) which protrudes beyond the grate surface, and the end (52) of which on an outer portion (51) is directed downwards towards the grate (1) and ends in the outer third of the radius of the grate (1) at a distance from the grate surface.
10. Wood pellet stove according to claim 9, characterised in that the steel bracket (49) has a portion (50) which is axial to the conveyor screw (2) as well as a downwardly projecting outer portion (51) which is parallel thereto and which ends at a distance of 5 mm to 12 mm from the grate surface.
11. Wood pellet stove according to one of claims 9 to 10, characterised in that the circular grate (1) has an external diameter of 150 mm to 170 mm and the steel bracket (49) has a portion (50) which is axial to the conveyor screw (2) as well as a downwardly projecting portion (51) which is parallel thereto and which ends at a distance of 6 mm to 12 mm from the grate surface, said latter portion being spaced apart from the axial portion (50) by 55 mm to 65 mm.
12. Wood pellet stove according to one of claims 9 to 11, characterised in that an ignition element (53) is arranged above the grate (1) in a manner inclined towards the grate (1), wherein the front end (54) of said ignition element ends in front of the outer portion (51) of the steel bracket (49).

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