Abstract:
A firewood retainer assembly and a fireplace incorporating the same are provided. The assembly includes a grate for supporting firewood at a level above a floor of a fireplace combustion chamber. The grate includes a first end opposite a second end such that a width of said grate is defined between these ends. The assembly also includes a deflector positioned adjacent the grate for deflecting air entering said combustion chamber below the level. A method of burning firewood is also provided which results in reduced particulate emissions. The method requires the deflection of air used for combustion below the firewood, heating the air with embers located below the firewood, and using the heated air for combustion.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    In wood burning fireplaces, firewood, such as wood logs, are typically placed on a log retainer or grate that sits above the floor of the fireplace fire box. Grates  10  are well known in the art and typically consist of spaced apart interconnected bar members which provide a support  11  for the wood logs at a distance  13  above a combustion chamber floor  17 . As combustion of the wood logs  12 ,  14  supported by the grate takes place, air is drawn into the fireplace combustion chamber  15  where the logs are located. Gaseous combustion products generated by the combustion of the logs are collected and exhausted via a chimney system above the combustion zone, whereas ambers  16  from log combustion remain underneath the grate and can be removed manually after the flame is extinguished. 
         [0002]    In conventional wood burning fireplaces, as the air  18  enters the combustion chamber, it is drawn through the side of the grate, as for example shown in  FIG. 1 , and partially underneath the grate as also shown in  FIG. 1 . Most of the air enters through the grate striking the front log  12 , cooling the log. Applicant has discovered that this cooling of the front log results in inefficient combustion resulting in high particulate matter emissions. In fact, a good portion of the air that enters the combustion chamber  15  is not used for combustion and just gets exhausted through the chimney along the path  20 , resulting in an inefficient use of the air. Moreover, this unused air tends to have a cooling effect resulting in high particulate combustion. Consequently, a grate or grate system is desired that would improve the efficiency of the combustion and that would reduce the particulate matter emissions. 
       SUMMARY OF THE INVENTION 
       [0003]    In an exemplary embodiment, a firewood retainer assembly is provided. The assembly includes a grate for supporting firewood at a level above a floor of a fireplace combustion chamber. The grate includes a first end opposite a second end. The assembly also includes a deflector positioned adjacent the grate for deflecting air entering the combustion chamber below the level. In another exemplary embodiment, the deflector extends beyond the first end in a direction away from the second end and extends beyond the second end in a direction away from the first end. In yet another exemplary embodiment, the deflector includes a first surface opposite a second surface and a thickness there between. The first surface faces away from the grate and the second surface faces the grate, and the first surface is angled relative to a vertical plane for deflecting the air entering the combustion chamber below the level. In a further exemplary embodiment, the deflector first surface includes a vertex and extends from opposite directions of the vertex and towards the grate. In yet another exemplary embodiment, the deflector first surface includes opposite end portions, such that each end portion extends in a direction opposite the other end portion and towards the grate. 
         [0004]    In another exemplary embodiment a wood burning fireplace is provided including a combustion chamber having an opening for receiving air for combustion. The fireplace includes a grate in the combustion chamber, at least one piece of firewood supported by the grate at a level above a floor of the combustion chamber, and a deflector between the grate and the opening for deflecting air entering the opening below the level. In yet another exemplary embodiment, the deflector includes a top end opposite a bottom end, such that the top end is further from the floor than the bottom end. A height of the deflector is defined between the top and bottom ends. The at least one piece of firewood supported on the grate extends to a height level such that the top end extends to at least the same height level as the at least one piece of firewood. In yet a further exemplary embodiment, the combustion chamber includes a first side wall opposite a second side wall and the deflector includes a main portion, a first end portion extending from the main portion and a second end portion extending from the main portion opposite the first end portion, such that the first end portion extends beyond the grate toward the first side wall and the second end portion extends beyond the grate toward the second sidewall. In another exemplary embodiment, the deflector includes an outer surface opposite an inner surface and a thickness there between, such that the outer surface faces away from the grate and the inner surface faces the grate, and such that the outer surface is angled whereby the top end is further from a rear wall of the combustion chamber than the bottom end. In yet another exemplary embodiment, the outer surface includes a vertex whereby the outer surface extends from opposite directions from the vertex toward the opposite side walls and toward the rear wall. In a further exemplary embodiment, the first end portion extends at an angle relative to the main portion and in a direction toward the rear wall, and the second end portion extends at an angle relative to the main portion and in a direction toward the rear wall. In yet a further exemplary embodiment, the first end portion extends to a location adjacent to the first side wall and the second end portion extends to a location adjacent to the second side wall. In another exemplary embodiment the at least one piece of firewood includes a first end opposite a second end and a length there between, and the deflector extends beyond the at least one piece of firewood first end and away from the at least one piece of firewood and in an opposite direction beyond the at least one piece of firewood second end and away from the at least one piece of firewood. In yet another exemplary embodiment, the grate includes a first side facing the first side wall and a second side facing the second side wall, and a first space is defined having a first width bounded by the grate first side and the first side wall and a second space having a second width bounded by the grate second side and the second side wall, such that the deflector first end portion extends along a majority of the first width and the deflector second end portion extends along a majority of the second width. In another exemplary embodiment, the first end portion occupies substantially the entire first width and the second end portion occupies substantially the entire second width. In a further exemplary embodiment, the bottom end is positioned to be at a height of least 2 inches from the floor. In yet a further exemplary embodiment, the bottom end is positioned to be at a height of about 1 inch to about 4 inches from the floor. 
         [0005]    In another exemplary embodiment a method of burning wood in a wood burning fireplace having the firewood supported on a grate in a combustion chamber having a floor and an opening is provided. The method includes burning the firewood creating a combustion, providing air through the opening, deflecting the air entering through the opening to an area above the floor and below the grate, heating said deflected air by embers located on the floor, and using the heated air in the combustion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a cut away end view of a fireplace combustion chamber with a prior art log retainer assembly including logs. 
           [0007]      FIG. 2  is a cut away end view of a fireplace combustion chamber with an exemplary embodiment retainer assembly with logs retained thereon. 
           [0008]      FIG. 3  is a top view of an exemplary embodiment log retainer assembly with logs retained thereon. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0009]    Applicant has discovered that a way to improve the burning efficiency and to reduce particulate emissions of a wood burning fireplace is to have the air entering the combustion chamber that is used for combustion be pre-heated. Applicant has discovered that this can be achieved by guiding the air entering the combustion chamber  15  beneath the firewood, e.g., the logs  12 ,  14  in a space  22  between the logs and the heated embers  16 , as for example shown in  FIG. 2 . As the air moves past the heated embers, it is heated and then rises to aid in the combustion of the logs  12 ,  14 . To achieve this effect, a baffle or deflector  24  such as for example a deflector plate is positioned in front of the grate so that air  18   a  entering the combustion chamber strikes the deflector  24  and is deflected downward towards the embers, as for example along a path  26 . In an exemplary embodiment, the deflector is a plate angled from the vertical plane along an angle  28 . In an exemplary embodiment, the angle  28  between a vertical plane and the deflector plate  24  is 15°, such that the air striking the deflector plate is guided beneath the grate. In other exemplary embodiments, the angle  28  may be in the range from about greater than 0° to 60°. 
         [0010]    In a further exemplary embodiment, the deflector outer surface  29  which is facing the incoming air, is angled toward the grate, as for example shown in  FIG. 3 . With this exemplary embodiment, the deflector outer surface  29  defines a vertex  30  which is positioned generally about the center of the grate. In an exemplary embodiment, the vertex is also formed about a center of the deflector outer surface. In an exemplary embodiment an angle  31  that the outer surface is bent on either side of the vertex is in the range of greater than 0° to about 45°. When using a plate as a deflector, this can be achieved by bending the deflector plate toward the grate. In other embodiments, the angle may be formed by machining. 
         [0011]    In a further exemplary embodiment, opposite end portions  32  of the deflector outer surface extending from opposite sides of a main portion  33  of the deflector outer surface extend beyond either end  34  of the grate and beyond the ends  36  of the wood logs such that air attempting to reach the logs by moving around the sides of the grate will strike these ends portions  32  of the deflector and will be consequently also guided to the sides away from the logs and beneath the grate. In an exemplary embodiment, the deflector is long enough so as to extend to each opposite side wall  38  of the combustion chamber  15 . In another exemplary embodiment, the deflector does not extend all the way across the combustion chamber. In a further exemplary embodiment, end portions  32  of the deflector outer surface  29  are angled in a direction towards the grate, as for example shown in  FIG. 3 , so as to guide the air away from the logs and underneath beneath the grate and/or logs. In an exemplary embodiment, the angle  35  that the outer surface end portions  32  are bent relative to their respective main portions is in the range of greater than 0° to 90°. In an exemplary embodiment, the outer surface portions may extend toward the firewood without extending beyond the ends of the firewood or grate. In an exemplary embodiment, the length of the deflector is at least half as long as the width  43  of the combustion chamber and may be as long as the width of the combustion chamber. 
         [0012]    In another exemplary embodiment, the end portions  32  are not angled relative to their respective main portions toward the grate. In a further exemplary embodiment, the deflector outer surface including the end portions or the outer surface end portions individually extend across a majority of the width  40  between grate end  34  and its respective combustion chamber side wall  38  and/or a majority of the width  42  between a log end  36  and its respective side wall  38  of the combustion chamber. 
         [0013]    Applicant has discovered that increased burning efficiency and a reduction in combustion particulates can be obtained by positioning the bottom edge  44  of the deflector to a level not higher than the lowest level  48  of the wood logs. In an exemplary embodiment, the deflector bottom edge extends to the wood log support level  11  defined by the bar members  19  of the grate. In another exemplary embodiment, the bottom edge of the deflector extends to the lower surface of the bar members  19  of the grate as for example shown in  FIG. 2 . In an exemplary embodiment a distance  46  of about 2¼ inches from the floor  17  the combustion chamber to the lower edge  44  of the deflector provided desired results. In another exemplary embodiments, the distance  46  is at least 2 inches. In yet another exemplary embodiment, the distance  46  is in the range of 1 inch to about 4 inches. Furthermore, Applicant has discovered that a deflector plate having a top edge  50  extending to at least the uppermost height level  52  of the logs  12 ,  14  will work sufficiently in deflecting an appropriate amount of the air. A deflector outer surface height  54  of about 2 to 4 inches should be sufficient for most applications so as to cover the height of the logs when resting in the grate. In other exemplary embodiments, the deflector outer surface may have a height of about 1 to about 7 inches. The deflector plate may have flat surfaces or ornamental surfaces  56  surfaces facing away from the grate. In other exemplary embodiments, the deflector plate may be perforated. In further exemplary embodiments, the perforations may be such that the air striking the plate is guided downwards through the perforations and beneath the grate. 
         [0014]    With the deflector plate, the air entering the combustion chamber is significantly kept away from the logs and is directed beneath the grate just above the embers where it is heated. By doing so, a maximum combustion temperature is maintained as the cooler incoming air is kept away from the logs and the log extremities and is directed above the embers where it is heated prior to combustion. Furthermore, the guidance plate keeps the embers from the wood combustion to remain within a combustion zone below the firewood, thus maintaining a maximum temperature in the combustion zone. Applicant believes that bed of embers is kept hot during combustion due to the incoming air flow path created by the deflector. The air is forced to circulate right above the bed of embers as shown by arrow  18   a  ( FIG. 2 ) causing oxygen to be fed constantly underneath the firewood. This causes a higher temperature to be maintained in the combustion zone resulting in a more complete firewood combustion and lower particulate emissions. 
         [0015]    Applicant has conducted tests with an exemplary embodiment deflector plate used in a wood burning fireplace. Tests were conducted using ASTM test methods. In a test without the use of a deflector plate, the particulate emissions exhausted from the fireplace were measured to be at 7.08 grams per kilogram of wood burned. By using a simple flat plate as the deflector plate, the emissions were reduced to 3.41 grams per kilogram of wood burned. By using a deflector plate that extended to either side wall of the combustion chamber, the particulate emissions were reduced to 3.2 grams per kilogram of wood burned. By using a deflector plate where the ends of the deflector plate were bent backward in a direction towards the grate, as for example shown in  FIG. 3 , the particulate emissions were further reduced to 2.69 grams per kilogram of wood burned. 
         [0016]    Although the present invention has been described and illustrated to respect to exemplary embodiments, it is to be understood that it is not to be so limited, since changes and modifications may be made therein which are within the full intended scope of this invention as hereinafter claimed.