Abstract:
This invention relates generally to a fireplace having a firebox chamber exhausting upwardly to a chimney, a front opening and fuel positioned in the firebox chamber and more specifically to an easily removable cover apparatus for the upper portion of the front opening whereby air flowing through the front opening will predominately flow through the lower portion of the firebox which increases the air flow onto the fuel.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates generally to a fireplace having a firebox chamber exhausting upwardly to a chimney, a front opening and fuel positioned in the firebox chamber and more specifically to an easily removable cover apparatus for the upper portion of the front opening whereby air flowing through the front opening will predominately flow through the lower portion of the firebox which increases the air flow onto the fuel.  
           [0003]    2. Description of the Prior Art  
           [0004]    One of the more important issues to be addressed in fireplace design or fireplace tools and devices is how to get the maximum amount of air (i.e. oxygen) to the fuel (eg wood, coal, peat and so forth). This issue of maximizing air flow to the fuel is especially important during the initial stages of starting a fire. For a standard residential fireplace it is not as important once a fire is well underway in the fireplace. This is because most residential fireplaces are obviously designed such that once the fuel is fully burning they draw quite well, burn efficiently and do not require additional means or structures to focus air flow on the fuel.  
           [0005]    In the past, the issues of maximizing air flow on the fuel at the early stages of the fire have been addressed by both (1) the design of the fireplace or fireplace openings to increase the airflow over the fuel, and (2) by the use of tools or methods to direct air on the fuel by manually blowing, fanning or pumping the air to the fuel (e.g. diaphram blowers or methods as simple as fanning the fuel with magazines).  
           [0006]    In most commercial situations or in residential situations where aesthetics is not an issue (i.e. the primary means of heating the home is the fireplace) these problems are typically solved by focusing the airflow onto the fuel by means such as restricting openings, dampers and deflectors. These methods result in fires which are easily started and efficient but almost by definition they are not as aesthetically pleasing since they necessarily involve in some way restricting the opening to the fireplace. In other words, what you gain in ease of starting and efficacy you give up in aesthetics since one can&#39;t see the fire burning in the fireplace as well as one can see the fire with an unobstructed view  
           [0007]    Examples of such fireplace designs to increase the oxygen/air flow over the fuel includes the following patents:  
           [0008]    The Brown patent (U.S. Pat. No 4,173,967) discloses a grate which has orifices which force the air to flow toward the center of the grate to maximize combustion in this area.  
           [0009]    The Wilkening patent (U.S. Pat. No 4,706,647) discloses an air flow damper-director control which controls the flow of air to fire from openings disposed in the fireplace enclosure.  
           [0010]    The Shults patent (U.S. Pat. No 2,814,287) for draft control shows and adjustable deflector used with seperate damper controls over openings in the front of fireplace to control the direction and amount of air flow.  
           [0011]    The Merryweather patent (U.S. Pat. No. 2,707,946) shows a stationary deflector for directing the air flow from an adjustable damper which controls the flow of air from openings in the front of the fireplace enclosure.  
           [0012]    The Lydle patent (U.S. Pat. No. 3,459,173) discloses a fireplace front or screen with a plurality of openings that are connected to a chamber with a damper which allows air flow in one direction and a deflector that is always open that deflects air in another direction.  
           [0013]    These strucural examples all have the additional disadvantages (in addition to not being aesthetically pleasing) of being relatively complicated from a structural point of view and also they are typically built into the structure of the fireplace, grates or fireplace openings. This permanence of the structure means that it is normally still there after the fire is self perpetuating (i.e. with sufficient fuel will remain burning without additional human intervention such as fanning the flames or adding combustible materials such as newspaper or lighter fluids). Lastly, the prior art structural solutions above require retrofitting of the existing fireplace, grates or fireplace openings. This can be expensive, time consuming, and complicated.  
           [0014]    What is needed is a simple, inexpensive, cover apparatus which is easily mountable and easily removable from the front entrance of a fireplace to focus the air flow on the fuel. This mobility and ease of attachment of the cover apparatus to the front of the fireplace or the fireplace opening will allow for removal (including detachment, retraction, rolling up or compression) of the cover apparatus once the fire is self perpetuating. This removal of the cover apparatus allows one to see the full frontal opening of the fireplace. The advatages of such an apparatus is simplicity, no retrofitting and no change of appearance of the fireplace once the apparatus has been removed or retracted.  
         SUMMARY OF THE INVENTION  
         [0015]    Our invention provides a novel and unobvious apparatus which helps to improve air flow to the fuel in a fireplace. This apparatus involves an easily attachable or positioned and easily removable or retractable cover apparatus which can be placed over the front opening of the firebox of the fireplace. This cover is placed and sized such that it covers the upper portion of the front opening of the firebox and accordingly forces the air flow through the lower portion of the front opening which in turn increases the air flow to the fuel. This cover is especially useful during the time period when the fire is being started. It will normally be either retracted or removed once the fire is self perpetuating. By removing or retracting the cover apparatus the fireplace owners can enjoy seeing the full front opening of the fireplace.  
           [0016]    In one embodiment of our invention the apparatus is a fireproof cover (for example a rectangular canvas cloth possibly covered with fire retardant material) which hangs down from a rod which in turn is attached to two or more hooks or other attachment devices over the front opening of the fireplace. The cover is sized such that it covers the top portion of the front opening but not the lower portion. The cover is hung over the opening after the fire has been started and is beginning to draw air into chimney but before the fire is self perpetuating (or the cover apparatus can be used to revive a fire that is beginning to die down). Normally but not necessarily the cover apparatus would be removed once the fire is self perpetuating. This detachment or retraction of the cover would return a normal appearance to the fireplace (i.e. nothing obstructing the front opening of the fireplace).  
           [0017]    This invention solves the problems with previous prior art because it is: (1) simple and inexpensive; (2) easy to retrofit; (3) does not change the appearance of the fireplace (except when it is in use when starting or reviving a fire); and (4) does not involve the manual methods of fanning a fire such as a diaphram blower, fans, or newspapers used as fans. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    In the drawings:  
         [0019]    [0019]FIG. 1 is front view of a fireplace with the cover apparatus attached above the opening of the fireplace but in a retracted (rolled up) position.  
         [0020]    [0020]FIG. 2 is the same front view of the fireplace with the cover surface unrolled and hanging in front of the fireplace opening.  
         [0021]    [0021]FIG. 3 is the same front view of the fireplace but there is a different cover apparatus which is standing on the hearth as opposed to hanging from above the opening of the fireplace. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    The embodiment of the invention shown in FIGS. 1, 2 and  3  shows a standard residential fireplace which has hearth  11  (it could also just be called the floor or base), firebox  12 , and front opening  20  which is defined by the front perimeter walls  13 . It has been observed by inventors that when making a fire in a fireplace such as is shown in FIG. 1 (or in fact any type of fireplace) that it is important to have maximum air flow over or toward or through fuel  50  (in this case wood). It has further been observed that once a fire has been started and the chimney is drawing air that much of the air flow ends up not being helpful to the oxidation of fuel  50  but instead simply goes up the chimney or flue (not shown in these figures) through the upper portions of front opening  20 . In short, the air (with the vital oxygen) is wasted and never comes in contact with fuel  50  because of its upper level path through front opening  20  and out the flue. (This is despite the fact that grate  60  attempts to maximize the air flow on fuel  50  by raising fuel  50  higher in firebox  12  and grate  60  also allows for air flow to go underneath grate  60  since it is typically a series of open spaces defined by bars of metal).  
         [0023]    In order to maximize the air flow on fuel  50 , persons over the years have tried numerous methods as discussed in the Background section. As may now be easily understood from the description and the drawings, inventors have determined that an easily removable or retractable cover apparatus will force air flow through the lower portion of front opening  20  and into the lower portion of firebox  12  and onto or toward fuel  50 . This is especially effective once the fireplace has begun to draw. This is because once the fire has begun to draw if one puts cover surface  41  over the top portion of front opening  20  the fireplace will continue to draw but all the air flow is forced through the much smaller opening at the bottom of front opening  20 .  
         [0024]    In fact, if the fire is drawing well there will be significant pressure on cover surface  41  since there will be low pressure on the backside (i.e. in firebox  12 ) and higher pressure on the front side of cover surface  41  (i.e. facing the room). This pressure differential acts to pull cover surface  41  toward firewall  12 . If cover surface  41  is canvas or cloth or some other easily rollable material the pressure differential may necessitate attaching support structures  70  onto cover surface  41  or incorporating support structures  70  into cover surface  41  (as shown in FIG. 2). Support structure  70  can be any of a number of well known materials (metal, wood etc) and can be in the form of a rod, bar, slat, or webbing and so forth. The good news about the pressure differential is that it acts to pull cover surface  41  agaisnt the walls and perimeter  13  which can minimize the leakage of air around cover surface  41  and force the great majority of the air flow through the lower portion of the frontal opening where it is most beneficial in oxidizing fuel  50 .  
         [0025]    There are a number of different ways in which cover surface  41  can be placed over the top portion of front opening  20 . In FIG. 1, the preferred embodiment shows cover apparatus  40  attached to attachment means  30 . It could also be attached to a fireplace screen if the screen was flush agaisn&#39;t front opening  20  (see the Experiments below). In FIG. 1 attachment means  30  are simple hooks which have been anchored into the wall above fireplace front opening  20 . Cover apparatus  40  is comprised of cover surface  41  which has been rolled around rod  42 . The ends of rod  42  are attached to attachment means  30  (in a preferred embodiment it is very easy to attach or detach cover apparatus  40  so that it installed (e.g. hung) and removed very quickly and easily such as would be the case with the simple hooks shown as attachment means  30 ).  
         [0026]    [0026]FIG. 2 shows cover apparatus  40  (which includes cover surface  41 ) unrolled, unfurled or pulled down such that cover surface  41  covers the upper portion of front opening  20 . In the preferred embodiment one can alter the length of cover surface  41  hanging over front opening  20  to modify air flow and direction into firebox  12 . This unrolling, pulling down or unfurling of surface  40  can be done by methods identical to the extremely well known action of pulling down window blinds and by using identical mechanisms (e.g. rolling and unrolling a flat sheet or compressing, extending a pleated sheet in a concertina type action or even the use of slitted materials similar to those used in Levolar™ window blinds). For example, the unrolling, pulling down or unfurling action could be accomplished either manually by simply turning rod  42  in a circular motion or if cover apparatus  40  is designed like the well known window blinds then this unrolling could also be accomplished by pulling down on surface  41  until cover surface  41  covers the desired upper portion of front opening  12 . In short, there are numerous ways in which surface  41  could be placed over front opening  20  and they will be well known to those skilled in the art.  
         [0027]    It is important that cover surface  41  and support means  70  are sized such that they extend beyond perimeter  13  and out onto the wall beyond perimeter  13  because the pressure differential will tend to bow or pull cover surface  41  in towards firewall  12  and accordingly cover surface  41  and support(s)  70  needs to be somewhat larger than the horizontal dimension of front opening  20 . Also it may be desirable to make support(s)  70  out of heavy material so that they keep cover surface  41  pulled taut so that the pressure differential does not pull cover surface  41  into firebox  12 .  
         [0028]    In a less preferred embodiment, cover apparatus  40  could be designed such that it does not roll up into a cylinder as shown in FIG. 1. It is possible that cover apparatus  40  could simply be permanently as shown in FIG. 2, where surface  41  is not rolled around rod  42 . In such a case cover apparatus  40  would simply be attached to attachment means  30  and would always be in an unrolled or rectangular configuration. In this configuration, cover surface  40  might even be rigid (as shown in the embodiment of the FIG. 3). However a rigid application is probably not a preferred embodiment since it would take up more space then the embodiment where cover surface  41  is able to be rolled up onto rod  42 . In the “window blind” embodiment cover apparatus  40  is a relatively compact cylinder that is able to be stored unobtrusively near the fireplace for frequent use.  
         [0029]    [0029]FIG. 3 shows another less preferred embodiment of cover apparatus  40  which does not involve hanging cover surface  41  from attachment means above the fireplace opening. In FIG. 3 surface  41  is rigid and is supported by legs  45  which set on hearth  11 . In this instance surface  41  and legs  45  can be any of a number of different well known metallic or fireproof materials (fireproofing is probably preferred but is not strictly necessary as applicants actually used newspaper agaisn&#39;t a screen in proof of concept experments detailed below and the newspapers had small burn marks but never caught entirely on fire). The embodiment shown in FIG. 3 is also not preferred because it is difficult to change the amount of the upper portion of front opening  12  which cover surface  41  is covering.  
       EXPERIMENTS  
       [0030]    Proof of concept experments were run in a standard residential fireplace with an upwardly extending flue and chimney and which had a standard metallic screen which laid flush agaisn&#39;t the front opening of the fireplace. The fireplace front opening was approximately 26 inches high and approximately 46 inches wide. The screen could be drawn shut so that it covered the entire front opening of the fireplace. Wood was placed on a standard metal grate. Assuring that the flue was open to the chimney, we used scrap newspaper underneath the grate to attempt to light the slightly damp wood (it had been stored outside without cover) on top of the grate. Using standard methods we were successful in getting the .chimney to draw air flow into it and we were successful in getting the wood partially burning but not self perpetuating (these moderate successes were attained with great effort by continuing to feed newspaper under the grate and fanning the newspaper and wood).  
         [0031]    In proof of concept of the invention, we then proceeded to take portions of newspaper and put them agaisn&#39;t the front opening screen. The pressure differential caused by the draw from the chimney was such that the newspaper (in single sheet thicknesses) was forced agaisn&#39;t the screen and did not have to be held in place agaisn&#39;t the vertical screen by hand. Experimenting with placement of the newspapers we found that by covering the upper portion of the front opening screen and leaving the bottom portion uncovered that comparatively large quantities of air (and obviously oxygen) flowed through the bottom portion of the screen and onto the wood. The effect was dramatic and could even be heard as the rush of air flowed past the newspapers and onto the burning wood. In a matter of seconds the wood was burning more intensely. In a matter of 1-2 minutes the fire (which previously had been difficult to start) was roaring and self perpetuating. We found that the invention worked best by covering roughly the upper two thirds (16 to 18 inches) or the upper three quarters (19-21 inches) of the screen over the front opening (although it is entirely possible that in other fireplaces with other geometries and designs that other ratios may prove more effective—in addition, the effect is apparent, but not optimized, with almost any amount of coverage of the upper portion of the fireplace opening). After the fire becomes self perpetuating it was very easy to remove the newspapers and enjoy the full frontal view of the fireplace.  
         [0032]    This experiment was repeated a handful of times over a 3-4 day period and in each experiment it worked quite well in starting or in reviving a fire.  
         [0033]    An invention has been described that provides advantages in the art of fireplace cover apparatuses. Although the preferred embodiments have been described specifically with regard to detail, it should be noted that many details my be changed without departing from the scope of the invention as it is defined in the following claims.