Abstract:
In a wood burning stove comprising a burning chamber ( 1 ) and a wood pellet burner ( 3 ), said wood pellet burner ( 3 ) is movable between a retracted position, in which the components of the wood pellet burner ( 3 ) are positioned outside the burning chamber ( 1 ), whereby the burning chamber ( 1 ) is suitable for burning wood logs etc., and an inserted position, in which the main components of the wood pellet burner ( 3 ) are positioned inside the burning chamber ( 1 ), and the wood pellet burner ( 3 ) can be activated to burn wood pellets ( 19 ) or similar particulate solid fuel inside the burning chamber ( 1 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a wood burning stove with wood pellet burner of a kind, in which there is provided a possibility of burning either wood logs or wood pellets, and where the burning of wood pellets can be performed in an automated manner. 
       BACKGROUND ART 
       [0002]    In wood burning stoves with wood pellet burners, it has been known to rearrange the components of the wood pellet burner manually in order to make it possible to burn wood logs, whenever this is desired. A wood burning stove with wood pellet burner of this kind is known from the firm Bioline. In the Bioline construction, a covering has to be placed manually on top of the wood pellet burner in order to be able to burn wood logs in the stove. A corresponding manual removal of the cover is required in order to be able to start the wood pellet burner 
         [0003]    EP-A-1,653,154 discloses a wood burning stove comprising a burning chamber and a wood pellet burner. The connection between the wood burning burner and the burning chamber is restricted by a cover, which is removed in order to be able to activate the wood pellet burner. 
       DISCLOSURE OF THE INVENTION 
       [0004]    It is the object of the present invention to provide a wood burning stove with wood pellet burner of the kind referred to above, with which it is possible to change from wood log burning to wood pellet burning and vice versa without manual rearrangement of the components of the wood pellet burner of the stove, and this object is achieved with a wood burning stove with wood pellet burner of said kind, which according to the present invention comprises the features set forth in the attached claim  1 . With this arrangement, a simple repositioning of parts of the wood pellet burner is performed in order to change from wood burning to wood pellet burning and vice versa. 
         [0005]    This repositioning can be performed automatically such that an automatic change can be performed when the wood logs in the burning chamber are burned out. Automatic introduction of the wood pellet burner into the burning chamber and starting thereof can be performed without any manual intervention. 
     
    
     
       SHORT DESCRIPTION OF THE DRAWINGS 
         [0006]    In the following detailed part of the present description, the invention will be explained in more detail with reference to the exemplary embodiment of a wood burning stove with wood pellet burner according to the invention shown in the drawings, in which 
           [0007]      FIG. 1  schematically shows an overview of essential parts of the wood burning stove with wood pellet burner in accordance with the present invention, and 
           [0008]      FIG. 2  schematically shows an enlarged view of some parts of the wood pellet burner of  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0009]    The wood burning stove with a wood pellet burner shown in  FIG. 1  comprises a burning chamber  1  provided with a refractory lining  2 . A wood pellet burner, generally indicated by the number  3 , comprises, as shown in  FIG. 2 , a fire pot  4  provided with a grate  5  for supporting the burning wood pellets  19 , combustion air being supplied from underneath the grate  5  via an air supply tube  6  The wood pellets  19  will be ignited when starting up the wood pellet burner by means of a hot bulb  7  positioned in a separate part of the air supply tube  6  separated from other parts of this air supply tube  6  by means of a separating wall  17 , whereby the air supplied via the separated part of the air supply tube containing the hot bulb  7  will have a sufficiently high temperature to ignite the wood pellets  19 . 
         [0010]    Supply of wood pellets  19  to the fire pot  4  is provided from a wood pellet storage  20  by means of a screw conveyor  10  extracting the wood pellets  19  from the wood pellet storage  20  and delivering the wood pellets to a supply tube  9 , through which the wood pellets fall down on the chute  8  for receiving the wood pellets and delivering the wood pellets to the fire pot  4  on top of the grate  5 . The screw conveyor  10  is driven intermittently by a motor  11  in order to deliver the wood pellets at a suitable rate, said rate possibly being variable, depending on the required heating level. 
         [0011]    The delivery of combustion air via the air supply tube  6  and the flexible tube  16  is provided by means of a fan, not shown in the drawings, said fan possibly being controlled in its velocity in order to deliver a suitable amount of combustion air corresponding to the amount of wood pellets delivered to the fire pot  4 . 
         [0012]    The hot bulb  7  is naturally only used for ignition when starting up the wood pellet burner, and as soon as the wood pellets  19  are burning inside the fire pot  4 , the hot bulb  7  is no longer supplied with electricity to heat up the combustion air delivered thereby. 
         [0013]    As shown in  FIG. 1 , the parts of the wood pellet burner comprising the fire pot  4 , the back wall  18  and the wall section  15  are movable in a longitudinal direction along the slide bars  14  controlling said sliding movement, and said movement is furthermore controlled by the spindle  12  driven by the motor  13 , By this moving mechanism, the wood pellet burner  3  can be moved to the right as seen in  FIG. 1 , whereby the wall section  15  is brought into alignment with the refractory lining  2  of the burning chamber  1 , whereby the burning chamber  1  is freed from all the components of the wood pellet burner  3  and thus can be used for burning wood logs or the like. 
         [0014]    Preferably, the burning chamber  1  is supplied with primary air for the burning of wood logs through a grate at the bottom of the burning chamber and the burning wood delivers heat by the combustion air circulating inside the burning chamber and through suitable channels connecting to a chimney. The burning chamber may, as is ordinary within the art of wood burning stoves, be provided with a glass door such that the burning wood or burning wood pellets can be viewed from outside. 
         [0015]    Preferably the control of the electrical components, i.e. the hot bulb  7 , the spindle motor  13 , the screw conveyor motor  11  and the combustion air fan, are controlled automatically in order to secure the correct functioning of the stove. Preferably, different temperature sensors are provided in order to secure this correct functioning of the stove, whereby detection of correct ignition of the wood pellets, the burn out of possible wood logs can be detected correctly in order to automatically shift from wood log burning to wood pellet burning, based on e.g. a thermostat detecting the room temperature close to the stove. 
         [0016]    The control of the insertion and retraction of the wood pellet burner components may comprise detectors for detecting the end positions of the wood pellet burner components, and furthermore in order to avoid faults due to possible blocking of the movement due to residual material inside the burning chamber  1 , an over-current detection on the motor  13  for the spindle  12  may be provided such that insertion of the wood pellet burner components into the burning chamber  1  can be stopped without destruction of any of the components and a fault report or signal be set when such fault has been detected. 
         [0017]    Above the invention has been described in connection with a specific embodiment thereof, however, many modifications may be envisaged without deviating from the main principles of the invention. Among such deviations, the following may be stated. The movement of the pellet burner in and out of the burning chamber may be provided by means of a rack and pinion drive or other linear movement drives instead of the mentioned spindle drive. The guidance of the movement of the pellet burner in and out of the burning chamber may be provided by means of other types of rails than the rails shown in the drawings, which are rods of circular cross-section co-operating with corresponding bushings on the pellet burner system. Thus, the rails may be simple rails on which sliding elements of the pellet burner are sliding, or rails on which wheels connected to the pellet burner are rolling or vice versa, rails on the pellet burner rolling on wheels mounted inside the stove. 
         [0018]    Furthermore, the transport of the pellets from the storage means to the wood pellet burner may be provided in many other ways than the shown screw conveyor, thus e.g. the screw conveyor may be positioned horizontally instead of obliquely upwardly extending, and other types of conveyors may be used for controlled delivery of the wood pellets to the wood pellet burner. 
         [0019]    Moreover, the insertion and retraction of the wood pellet burner into and out of the burning chamber may be performed through a sidewall instead of through the back wall as shown in the drawings.