Abstract:
The present invention includes a universal combustion chamber preferably shipped from a factory as a separate unit for field installation into a plurality of different fireplace units and includes a top panel and a floor panel connected to sidewall panel to form a complete ready to use gas tight structure. The combustion chamber is fabricated from flat and/or curved panels which are preferably molded from a thick paste slurry of mixed vitreous alumina silicate fibers combined with an aqueous solution of silica binder and fired to form non-porous gas tight panels which are interconnected to form a gas tight combustion chamber. The connecting joints are preferably reinforced by the addition of a high temperature adhesive added to the mating joints. The joints may be further reinforced and/or sealed by mechanical reinforcing at or in the joints. The joints may be eliminated by forming a one piece combustion chamber on forming molds that are designed to be separated from a formed but uncured combustion chamber.

Description:
Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No.  5 , 541 , 237 . The reissue applications are application Ser. Nos.  09 / 935 , 483  ( the present application )  and  10 / 473 , 858  which is a divisional reissue application of Ser. No.  10 / 437 , 858 .   
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a universal combustion chamber useful for installation in metal fabricated fireplaces or a stand alone combustion chamber. More particularly, the present invention relates to an assembled non-porous cast fiber-reinforced combustion chamber that is machinable in its cured stage and moldable in its uncured preformed stage. 
     2. Description of the Prior Art 
     Heretofore, panels made from high temperature ceramic materials were known. Heat-N-Glow of Savage, Minn. has incorporated high temperature ceramic panels under the gas burners of some of their gas fireplaces in the form of loose panels. Heat-N-Glow has also incorporated both refractory firebrick and cast ceramic blocks or panels in numerous stoves and fireplaces for insulation purposes as well as for aesthetic purposes. 
     Manufacturers of commercial and home heating systems have employed cast refractory fireboxes in the base of furnaces. Such refractory fireboxes are protected against exhaust leakage because they are placed in an area where leakage would not escape from the furnace or boiler or are completely backed up by another non-porous sheet or wall. 
     Unvented or non-vented gas heaters and fireplaces are not concerned with preventing escape of burned exhaust gases into a living area, thus, do not totally enclose the combustion chamber or burners. Such unvented gas stoves have been known to deplete the oxygen supply in a living area. 
     Applicants are not aware of any gas fireplace which employs a gas combustion chamber that virtually eliminates the need for any fireplace enclosure or shroud around the gas combustion chamber for heat protection. 
     It would be desirable to provide a universal combustion chamber which would accommodate a variety of gas burners and a variety of vents. It would further be desirable to provide an assembled leak proof combustion chamber made from non-porous cast fiber reinforced moldable and machinable material that is cool enough at its outer surface to be installed without additional insulation or heat protective barriers on the outside of the combustion chamber. 
     SUMMARY OF THE INVENTION 
     It is a principal object of the present invention to provide an assembled gas fireplace combustion chamber that comprises a plurality of non-porous cast fiber reinforced panels. 
     It is another principal object of the present invention to provide a fabricated kit of non-porous cast fiber reinforced panels that are accurately formed to be assembled into a leak proof fireplace combustion chamber. 
     It is another principal object of the present invention to provide an assembled prefabricated non-porous cast fiber reinforced combustion chamber that is machined and ready for installation of a gas burner. 
     It is another principal object of the present invention to provide a plurality of assembled or unassembled machined non-porous cast fiber reinforced panels that when assembled form a combined combustion chamber and fireplace ready for completion by addition of a gas burner and/or a gas vent. 
     It is yet another object of the present invention to provide a universal gas combustion chamber/fireplace unit that does not require a metal enclosure for operation in a fireplace. 
     It is yet another principal object of the present invention to provide a universal gas combustion chamber/fireplace unit that is operable with a gas burner and has an outer wall temperature cool enough to meet standards for zero clearance installations. 
     It is another object of the present invention to lower the cost of manufacturing gas fireplace units while increasing their efficiency by combining the functions normally associated with a separate gas combustion chamber and fireplace enclosure. 
     According to these and other objects of the present invention there is provided a universal gas combustion chamber of the type having a bottom floor panel, a top panel and vertical side panels assembled to form a fireplace when a gas burner is installed in or on the floor panel. Said gas combustion chamber panels being made from a moldable slurry of refractory ceramic fibers (preferably vitreous alumina silicate fibers) and a binder (preferably amorphous silica) to form strong machinable fiber reinforced panels. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a section in side elevation taken through a novel assembled non-porous cast ceramic fiber combustion chamber having a burner opening in the floor panel and an exhaust opening in the top panel and installed flush mounted as a vented gas fireplace; 
         FIG. 2  is a front view of the vented fireplace shown in  FIG. 1  showing a decorative surround with a simulated brick pattern which compliments the pattern in the interior of the non-porous cast ceramic combustion chamber; 
         FIG. 3  is a section and side elevation taken through a modified assembled ceramic combustion chamber having a metal rear panel and a fireplace enclosure which forms a heat exchange around the bottom, back and top of said combustion chamber; 
         FIG. 4  is a diagrammatic drawing in sectional plan view of the combustion chamber of  FIG. 1 ; 
         FIG. 5  is a diagrammatic drawing in sectional plan view of a combustion chamber of  FIG. 3  showing a two-level gas pipe gas burner therein; 
         FIG. 6  is a front view of a vented fireplace comprising the novel ceramic combustion chamber and a fabricated metal base support; 
         FIG. 7  is a diagrammatic drawing in plan view showing the bias support of  FIG. 6 ; 
         FIG. 8  is a front view of the base support of  FIGS. 6 and 7  with the front trim panel and transfer support bar removed; 
         FIG. 9  is a section in side elevation taken through a modified assembled ceramic combustion chamber completed for installation as a horizontal vented zero clearance fireplace; 
         FIG. 10  is a section in side elevation taken through a modified assemble ceramic combustion chamber completed for installation as a vertical vented zero clearance fireplace; 
         FIG. 11  is a diagrammatic isometric view of the novel assembled non-porous cast ceramic combustion chamber before modification for use as an unvented fireplace, a vented fireplace or a direct vented fireplace with or without a heat exchanger modification; 
         FIG. 12  is a plan view of a floor or top panel of a novel ceramic combustion chamber illustrating a second preferred embodiment panel; 
         FIG. 13  is a section taken at lines  13 — 13  of  FIG. 12 ; 
         FIG. 14  is a section as it would appear if taken at lines  13 — 13  through a top panel when reverse oriented; 
         FIG. 15  is an enlarged section in elevation taken through a floor panel showing a preferred metal flat pan burner; 
         FIG. 16  is an enlarged and section in elevation taken through a floor panel showing a non-porous ceramic flat pan burner; 
         FIG. 17  is an enlarged section in elevation taken through a floor panel showing another non-porous ceramic flat pan burner; 
         FIG. 18  is an enlarged section in elevation taken through a floor panel showing a composite metal/non-porous ceramic flat pan burner; 
         FIG. 19  is an enlarged detail of a vertical joint formed by a side and a rear panel of a ceramic combustion chamber having three vertical panels; 
         FIG. 20  is an enlarged detail of a another vertical joint formed by a separate side and rear panel; and 
         FIG. 21  is a block diagram showing the steps preferably employed to form the panels used in the novel gas combustion chamber described in the Figures hereinbefore. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Refer now to  FIG. 1  showing a vented gas fireplace unit  10  in side elevation taken through the novel assembled non-porous cast ceramic fiber combustion chamber  11 . The combustion chamber  11  comprises a top panel  12 , a rear panel  13  and a bottom or floor panel  14 . The floor panel  14  is provided with an aperture  20  in which a flat pan gas burner  15  is placed either below or at the surface of the floor panel  14 . The flat pan burner  15  is shown connected to a gas valve  16  via a gas connection pipe  17 . Air for combustion at the gas burner  15  enters through the louvered cover  19  and passes as burning gas around the logs  18  and is exhausted through the exhaust stack  21 . A glass front panel  22  may be provided on the vented gas fireplace unit  10  or may be removed if so desired. A decorative surround panel  23  formed as a simulated brick mantel piece is mounted directly to the studs  24  which are used to form a chase or enclosure around the combustion chamber. 
     Refer now to an enlarged front view of the vented fireplace  10  shown in FIG.  1 . The decorative surround panel  23  is provided with an aperture in which the combustion chamber  11  is placed. The combustion chamber  11  is further provided with a decorative brass trim  25  which complements the surround panel  23 . The panel  13  in the back and side of the combustion chamber  11  is shown having a simulated brick embossed surface which complements the surround panel  23 . 
     Refer now to  FIG. 3  showing a side elevation taken through a modified assembled ceramic combustion chamber which has a metal rear panel  29 . The metal rear panel and the rear panel  28  of a fireplace enclosure form a heat exchanger rear wall  31 . A similar heat exchanger wall  27  is formed between the top panel  12  and the top metal panel of the fireplace enclosure  26 . A bottom heat exchanger wall  32  is formed between the bottom or base of the fireplace unit  10  and the bottom or floor panel  14 . A blower  33  is installed in the bottom wall  32  of the fireplace unit and moves air from the outside room through walls  32 ,  31  and  27  to form a heat exchanger for the combustion chamber  11 . A baffle  34  is shown in installed in the upper and rear portion of the combustion chamber  11  to increase the exhaust gas flow and efficiency to the heat exchanger. 
     Refer now to  FIG. 4  showing a diagrammatic drawing in sectional plan view of the combustion chamber  11  of FIG.  1 . The aforementioned rear panel  13  and the side panels  35  and  36  are preferably made from a non-porous cast fiber reinforced insulating material which will be described in greater detail hereinafter. The combustion chamber  11  is shown assembled from panels  13 ,  35  and  36  and the floor panel  14  before the top panel  12  is assembled and not shown. Corner brackets  37  and  38  are preferably provided at the sharp edges of the combustion chamber  11  to provide corner reinforcements. The corner brackets  37  and  38  are preferably attached to the combustion chamber  11  with high temperature adhesives. However, it will be understood that ordinary silicon caulking compound which is durable up to 500 degrees Fahrenheit may also be used as an adhesive to attach the corner brackets  37  and  38 . The aperture  20  through which the flat pan burner  15  is installed is shown in the rear and center of the combustion chamber  11 . It will be understood that other types of apertures and other types of burners may be used within the universal combustion chamber  11  as will be explained hereinafter. 
     Refer now to  FIG. 5  showing a diagrammatic drawing in sectional plan view of the combustion chamber of FIG.  3 . The combustion chamber  11  in this drawing is shown provided with a two-level pipe burner  39  and an appropriate aperture for a combustion gas pipe will be provided in the floor or bottom panel  14 . The side walls  35  and  36  are preferably abutted against the rear panel  29  of the heat exchanger and is overlapped by the back panel  28  or the back wall of the fireplace enclosure  28 . These panels may be attached with high mechanical fasteners because the heat which passes through the panel  29  is intended to be hot enough to serve as a heat exchanger for the back wall  31  as explained hereinbefore. 
     Refer now to  FIG. 6  showing a front view of a vented fireplace which comprises the aforementioned novel ceramic combustion chamber  11  which comprises two side walls  35  and  36 , a top wall  12 , a bottom wall  14  and a rear wall  13 . The edges of the aforementioned walls  43  are shown exposed but may have attached thereto either decorative trim or surround pieces as described hereinbefore. The combustion chamber  11  is further provided with a fabricated metal base  41  onto which a trim piece or closure piece  42  is attached. A baffle  34  is installed in the combustion chamber  11  and supported therefrom by means not shown. The stack  21  is shown attached to the combustion chamber by means of a collar  44  and screws  45 . It will be understood that the fiber reinforced ceramic material is thick enough and dense enough to accept conventional screws for attachment purposes. 
     Refer now to  FIG. 7  showing a diagrammatic drawing in plan view of the base support  41 . The base support  41  is preferably formed from a single piece or three pieces of sheet metal to form an enclosure or surround which nests at the outer edges of the floor or bottom panel  14 . In the preferred embodiment of the present invention, a transverse support bar  46  is provided between the two side panels of the base support  41  and used to support the aforementioned gas valve  16  and flat pan burner  15 . 
     Refer now to  FIG. 8  showing a front view of the base support  41  and support tabs  47  which are formed by piercing tabs from the panel metal and diverting it from a vertical axis into a horizontal axis by bending the tab inward. The front of the metal base  41  may be closed by the trim piece  42  or the trim piece  42  may be made in the form of a louver for access air. However, by making the tabs  47  from the parent panel metal, air is capable of passing through the apertures made when the support tabs are formed. 
     Refer now to  FIG. 9  showing a section in side elevation through a modified assembled ceramic combustion chamber  11  which is completed for installation as a horizontal direct vented zero clearance fireplace. The numerals used in the previous figures which are substantially the same as those employed in  FIG. 9  are number the same and do not require additional description. The fireplace  11  is shown provided with a horizontal stack  48  which is adapted to fit onto the rear of the rear panel  13  of the combustion chamber  11  by a collar  49 . Surrounding the collar  49  is a combustion air chamber  51  which extends downward along the back of the rear panel  13  and forms a plenum  52  for providing a fresh air passageway into the bottom of the combustion chamber through either into the wall  32  or through an aperture  53  into the combustion chamber  11 . It will be understood that the plenum  52  shown along the back of the rear panel  13  may be formed as a duct which enters the bottom or the sides of the combustion chamber  11  but still forms a duct for communicating fresh combustion air into the combustion chamber. 
     Refer now to  FIG. 10  showing a side elevation taken through a modified assembled ceramic combustion chamber completed for installation as a vertical zero clearance fireplace. The aforementioned plenum  52  is shown as a plenum  54  which also passes down the rear of the rear panel  13  of the combustion chamber  11  and communicates with the rear or bottom of the combustion chamber  11  at panel  14 . In the preferred embodiment of the present invention, it is desired to bring the fresh combustion air down below the floor panel  14  and to permit it to rise along the edges of the flat pan burner  15  so as to effect a more complete combustion and flame color around the decorative logs  18 . The vertical stack  21  is adapted to the combustion chamber  11  by a collar  49  and the plenum or passageway  54  is formed from sheet metal and attached to the top and rear of the panels  12  and  13  of the combustion chamber  11 . The numerals in the  FIG. 10  are the same as those employed in FIG.  9  and do not require additional explanation. 
     Refer now to  FIG. 11  showing an isometric view of a novel assembled non-porous cast ceramic combustion chamber  11  before modification for use as an unvented fireplace or as a vented fireplace or as a direct vented fireplace with or without a heat exchanger modification. 
     The novel combustion chamber shown in  FIG. 11  is preferably made from an alumina silicate fiber solution, or an equivalent, with a binder and mixed to agitate the fibers to absorb the solution. Once the mixture of fibers forms a slurry as thick as a paste, it may be molded into any desired shape. The trapezoidal flat panel shape shown in  FIG. 11  is a preferred embodiment. However, the top and bottom panels may be made as a segment of a circle and the side walls  35 ,  36  and  13  may be made as a continuous curved panel. In any event, it is desired that the novel combustion chamber  11  be assembled from at least three pieces. The advantage to employing substantially flat panels is to enable one to ship the novel gas combustion chamber in a knock down kit easily packaged package for a minimum of transportation cost. 
     When the fireplace chamber  11  shown in  FIGS. 1  to  5  and  11  is molded as a one piece unit on a forming mold, care must be taken so that the uncured combustion chamber is not distorted. This is preferably accomplished by pre-drying on the mold before stripping the unit from the mold. This permits sealing or spraying before final drying. 
     Refer now to  FIG. 12  showing a plan view of a floor or top panel of a novel ceramic combustion chamber illustrating a second preferred embodiment panel. The panel  14  shown in  FIG. 12  is provided with grooves  55  which will accept and precision locate the aforementioned side panels  35 ,  36  and the rear panel  13 . 
     Refer now to  FIG. 13  showing a section taken at lines  13 — 13  of FIG.  12  and showing the aforementioned groove  55  which will accept a side panel  36  and precision locate it therein. Similarly, a groove  56  is shown in  FIG. 14  which is identical to the groove  55  shown in FIG.  13 . When the panel  14  is reversed 180 degrees, the groove on the left side of the lower panel becomes the groove on the right side for the upper panel. 
     Refer now to  FIG. 15  showing an enlarged section in elevation taken through a floor panel  14  showing a preferred embodiment metal flat pan burner  15  located in an aperture  20  which is preferably formed by cutting dies. 
     Refer now to  FIG. 16  showing an enlarge section in elevation taken through a floor panel  14  showing a non-porous ceramic flat pan burner  57  formed by drilling gas port apertures  58  into the floor panel  14  and providing air access slots  59  adjacent thereto. In the preferred embodiment shown in  FIG. 16 , the lower portion of the flat pan burner is formed by non-porous ceramic fiber reinforced material the same as a metal flat pan burner and the bottom portion  61  has the same interior spacing as a flat pan burner  15  so as to provide the same gas distribution within the flat pan burner as before. The lower portion of the flat pan burner  57  is preferably attached to the lower or bottom panel  14  by mechanical attachment means as well as adhesives. 
     Refer now to  FIG. 17  showing an enlarged section in elevation taken through a floor panel  14  which has machined therein the interior dimensions of a flat pan burner  15  shown as the area  62 . Gas ports  63  are drilled or punched in the panel  14  opposite the lower pan portion  64  which is attached to the bottom panel  14  by mechanical and adhesive means and provided with air slots  65  extending through both parts  64  and  14 . 
     Refer now to  FIG. 18  showing an enlarged section in elevation taken through a floor panel  14  showing a composite metal and non-porous ceramic flat pan burner. The upper portion of the flat pan burner is similar to that described with reference to FIG.  17  and is provided with gas ports  63  which communicate with a lower metal pan portion of a gas pan burner  66 . Air slots  65  are provided through the panel  14  to provide combustion air for the burner  66 . 
     Refer now to  FIG. 19  showing an enlarged detail of a vertical joint formed by a side panel  35  and a rear panel  13  held together by a corner support bracket  37  which is preferably attached with a high temperature adhesive or even a silicone caulking compound. 
     Refer now to  FIG. 20  showing in enlarged detail of another vertical joint formed by a side panel  35  and a rear panel  13  which are held together by a reinforcing spline  67 . Again, it is preferred that the panels be closed with a high temperature cement to assure that they are exhaust gas leak proof. 
     Refer now to  FIG. 21  showing a block diagram of the steps employed to make a moldable and castable slurry or paste of reinforced ceramic fibers used to make panels which are used to assemble the novel universal gas combustion chambers. In block  69  fibers of alumina silicate are mixed with a binder solution which is in aqueous form. The preferred aqueous solution is a binder of amorphous silicate which may be purchased from Nalco Chemical Company in Naperville, Ill. under the designation Nalco 1140. The high temperature reinforced fibers preferably are made from a mixture of silica and alumina (SiO 2  and Al 2 O 3 ) which are mixed and then melted and formed as fibers by blowing drops or portions of the melted mixture to form fibers that are graded by length and preferably are in a form of ½ to 1½ inches in length when mixed with amorphous silica. After the combination of fibers and binder solution are mixed together, they are agitated so that the fibers completely absorb the binder solution as shown in block  70 . After the mixing and agitation occurs, a slurry or paste is formed as shown in block  71  which is of a consistency which permits pouring or filling into molds or casting receptacles. The slurry or paste is then molded or cast or formed into this desired shape as shown in block  72 . The molding and casting of a desired shape of the paste may be formed on a continuous line in a flat panel form in which case the material is passed into a drying oven and would not require removal from a mold as shown in block  73 . The step performed at block  73  could be a progressive stamping mold or a rotary mold. After the material passes from the molding or casting operation at block  73 , it is dried as molded panels by firing or by holding in heated molds to dry off the water from the green paste mold. In the preferred embodiment, firing is accomplished at temperatures between 350 degrees Fahrenheit up to 1800 degrees Fahrenheit to drive off the water solution which comprises up to 25% by weight. 
     After drying or firing the panels at block  74 , the panels are trimmed or machined to a preliminary shape or trimmed or machined to a final shape at block  75 . Apertures and slots and gas ports and burners are formed therein, depending on the intended use of the panel. It will be appreciated that in some forms of individual molds, the edges of the dried panels are so precise that they do not require machining while being fitted together to form an assembled gas combustion chamber. After forming the desired panels in the desire shapes with the desired slots, holes and burners which may be formed by drilling or punching, the panels may be assembled into a combustion chamber shown in block  76  if the production operation is a continuous operation. However, if the panels to be assembled into a combustion chamber are for assembly at a production site or installation site, it is preferred that individual kits be manufactured from which assembled combustion chambers may be made on site to assure minimum damage and minimum cost of shipping. Thus, the desired panels for a particular preformed gas combustion chamber are packaged as a set of preformed parts for shipment as shown in block  77 . 
     Having explained a preferred embodiment of the present invention used in several different types of fireplaces, it will be appreciated that use of a universal combustion chamber greatly reduces the factory inventory as well as the field site inventory of combustion chambers. The fired and dried fiber reinforced combustion chamber is slightly hydroscopic but non-porous to exhaust gases and may be sealed without a steel or reinforcing backing layer even when used for burning wood logs. The reinforced panel can be made thicker and stronger for wood logs so as to meet wood stove standards and impact tests performed by underwriters as well as meeting zero clearance outside temperature of 160° F. if needed. 
     Manufacturers of Refractory Ceramic Fibers (RCFS) and aqueous binders publish data sheets on several different RCF. While the exact formulation may differ, the preferred silicate base is vitreous alumina silicate for making high temperature ceramic fibers. An equivalent silicate fiber would be operable when combined with a compatible RCF binder.