Abstract:
A water heater having improved operating characteristics and lower costs of manufacturing is described. The water heater has an unified combustion chamber and burner construction with a ceramic fiber matrix burner.

Description:
This application is a continuation of application Ser. No. 08/333,871, filed on Nov. 3, 1994, now U.S. Pat. No. 5,511,516 which is a continuation of prior application Ser. No. 08/113,618, filed Aug. 27, 1993, now abandoned. 
     The present invention relates to an improved construction for a gas water heater and particularly to a unified burner and combustion chamber construction and a low NO ceramic burner. 
    
    
     BACKGROUND OF THE INVENTION 
     Water heaters are commonly employed in homes and small businesses to heat water for domestic use. Water heaters are produced in large numbers and sold to consumers in a very competitive market. A large portion of these devices use gaseous fuel, such as natural gas or bottled gas, as an energy source. 
     Conventional gas fired water heaters often include a tank adapted to contain a body of water, a water inlet, a water outlet, a combustion chamber disposed below or within the tank, a gas regulator and a burner disposed within the combustion chamber. The entire structure is thermally insulated. Conventionally, the gas regulator senses the temperature of water within the tank. When the water temperature drops below a certain minimum, gas is allowed to flow to the burner within the combustion chamber where it is ignited, heating the combustion chamber and the body of water above or around the combustion chamber. The products of combustion are vented through a flue connected to the combustion chamber and passing through the water containing tank. This general construction has been common for many years. Numerous variations upon this construction have been created in attempts to increase efficiency and otherwise improve operating characteristics. 
     Over the last several years, the efficiency of water heaters, especially fuel efficiency, has become an important characteristic. This is the result of government regulation and also heightened consumer awareness concerning consumption of natural resources. Over recent years, insulation technology has improved insulation characteristics of water heaters. However, production line burner technology has remained comparatively stagnant and, therefore, inefficient. Additionally, concern for the environment has made the elimination of potentially polluting substances from the products of combustion more important. While gas fired water heaters are very low polluters when compared to other fuel consuming products, there are many water heaters. Government bodies and consumers have therefore sought to further reduce the contribution of pollutants emanating from water heaters. 
     In addition to all of the above very important design criteria, cost is a very important factor in producing water heaters. Water heaters are purchased by builders and home owners in a very competitive environment. The products are mass produced and sold throughout a large marketplace. In the United States, national companies compete very aggressively for sales. Water heaters must therefore be very economically manufactured or they will not sell and consumers will not gain the benefits of design improvements. 
     In conventional water heaters, the above objects are not optimally achieved. Additionally, the cost of manufacturing remains high. A number of different components including a tank, a combustion chamber, a burner, a reflecting pan under the burner to protect the bottom of the water heater from burner heat and numerous other elements and insulation are manufactured and assembled. Often, changing a design to address one of the above identified problems compromises another of the problems or increases cost significantly. 
     OBJECTS OF THE INVENTION 
     An object of the invention is to provide a water heater of improved operating characteristics which is inexpensive to manufacture on a production basis. 
     It is another object of the present invention to provide a water heater which has reduced emissions of oxides of nitrogen. 
     It is still another object of the present invention to provide a water heater of improved fuel efficiency and having low standby heat loss. 
     It is yet another object of the present invention to provide a water heater which consumes less materials in production and is less expensive to manufacture. 
     It is still another object of the present invention to provide a water heater having cooler external surfaces around the combustion chamber whereby special insulation techniques are not required and which economically extracts the maximum amount of heat from flue gasses. 
     Further objects and advantages to the invention will appear from the following detailed description of a preferred embodiment thereof and from the accompanying drawings. 
     SUMMARY OF THE INVENTION 
     The present invention contemplates a new and improved water heater construction which overcomes the above referred to problems and others and provides a water heater of simpler construction which is economical to manufacture, economical to operate, burns fuel cleanly and answers governmental regulations. 
     Briefly stated, in accordance with one aspect of the invention, a water heater is provided having a tank adapted to contain a body of water and an integrated combustion chamber and ceramic burner assembly below the tank. 
     Still further in accordance with the invention, a skirt generally matching the cross section of the tank is positioned below the tank and gas tightly fixed to the tank. A burner shelf is positioned within this skirt and gas tightly fixed to the skirt around its entire periphery. A ceramic burner is positioned on the burner shelf separating the volume within the skirt into a combustion chamber above the burner shelf and a burner volume below the burner shelf. A bottom pan is gas tightly sealed to the skirt around its bottom forming a gas tight burner chamber below the burner shelf. An air and gas proportioner communicates through the skirt and into the burner chamber in a gas tight manner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a water heater in accordance with the invention, mostly cut-away to the center line of the flue; 
     FIG. 2 is an enlarged detail drawing of the combustion chamber burner area of the water heater shown in FIG. 1; 
     FIG. 3 is a downward looking cross-sectional view taken along line  3 — 3  of FIG. 2 showing details of the burner construction; 
     FIG. 4 is a top plan view of the burner shown in FIGS. 1-3; 
     FIG. 5 is a cross sectional view taken along line  5 — 5  of FIG. 4; 
     FIG. 6 is a top plan view of a burner shelf used in accordance with the invention; 
     FIG. 7 is a side elevational view of the shelf shown in FIG. 6; 
     FIG. 8 is a cross-sectional view of the combustion chamber burner area of a submerged combustion type water heater using a burner of the invention. 
     FIG. 9 is a cross-sectional view of the combustion chamber burner area of FIG. 8 taken along the line  9 — 9  of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings wherein the structures shown are for purposes of illustrating the embodiments of the invention and not for the purposes of limiting same, the figures generally, and FIGS. 1 and 2 in particular, show a water heater  10  comprised of a tank  12  adapted to contain a body of water having an inlet  14  and an outlet  16 . A conventional drain  18  is also provided. Tank  12  has a cylindrical side wall  20 , a dome-shaped top  22 , water tightly fixed to side wall  20  and a bottom wall  24 . A cylindrical flue  26  containing baffles  100  passes through the center of tank  12  and communicates with the space below bottom wall  24 . Flue  26  having baffles  100  is conventionally connected to a conduit which conduct products of combustion from the flue out of the building in which the water heat is located. 
     Bottom wall  24  is provided with a downwardly extending cylindrical flange  30  around its entire periphery. This flange  30  is permanently fixed to tank side wall  20  by means of welding or the like. A cylindrical skirt  32  is positioned below tank  12 . Skirt  32  is provided with either a reduced portion  34  or an enlarged portion (not shown) which engages the bottom of tank  12 . In the embodiment shown, reduced portion  34  is permanently fixed to the inside surface of flange  30  of bottom wall  24 . Welding or the like provides a permanent gas tight joint between reduced portion  34  and flange  30 . 
     A ring-shaped burner shelf  36  is provided with a flange  38  which is air tightly fixed to skirt  32  below the reduced portion  34 . Burner shelf  36  is provided with a central opening  40  which is covered by a burner  42 . A combustion chamber  44  is defined by tank bottom wall  24 , the top portions of skirt  32 , burner shelf  36  and burner  42 . The combustion chamber  44  is air tight other than through the burner  42  and the flue  26 . A disc-shaped burner bottom pan  52  is provided at the bottom of skirt  32 . Burner bottom pan  52  is either provided with a flange  53  allowing attachment to the skirt  32  or is formed integrally with skirt  32 . In either embodiment, burner bottom pan  52  is joined to skirt  32  in an air tight manner. Skirt  32  is pierced on one side by an air and fuel proportioner  54 . Air and fuel proportioner  54  is comprised of a tube  56  mounted in a circular opening  58 . Tube  56  is open at its inboard end  60 . Tube  56  is provided with a conical enlarging portion  62  near its outboard end  64 . The outboard end  64  is also provided with an open drape portion  66 . As can be best seen in FIG. 2, drape portion  66  connects to the top half of the outboard end of tube  56  and to the bottom half end of tube  56 . 
     A thermostat  72  senses the temperature of the body of water contained in tank  12  by means of a sensor  74 . Thermostat  72  receives gas through a supply line  76  and provides gas through a gas line  78  to air and fuel proportioner  54 . Thermostat  72  also controls the operation of igniter  80  located in combustion chamber  44 . When thermostat  72  senses low water temperature, it provides gas to air and fuel proportioner  54  through a nozzle  82 . Gas and air are drawn through tube  56  into burner chamber  86  defined by the lower portion of skirt  32 , burner shelf  36 , burner  42  and burner bottom pan  52 . The air and fuel mixture flows through burner  42  and is combusted at the top surface  90  of burner  42 . 
     Burner  42 , shown in FIGS. 1-5, comprises a one-piece, fiber matrix construction resembling ceramic. Burner  42  is non-metallic and approximately one-half inch thick. A single structure comprised of a fiber matrix having a multiplicity of regularly arrayed ports  144  having a diameter of about 0.076 inches is provided. The ports account for approximately one-third the surface area  90  of fiber matrix burner  42 . Burner  42  is preferably ported over its entire area except for a peripheral area used for attachment to burner shelf  36 . The turbulation in burner chamber  86  caused by rapidly moving fuel and air, and associated mixing action, results in an even distribution of fuel and air against the bottom surface of burner  42 . This permits a substantially even flow of fuel/air mixture through ports  144 . The fuel and air flows through ports  144  and out of burner  42  at burner top surface  90  and is consumed, producing heat along burner top surface  90 . Heat is radiated from a combustion zone above burner top surface  90  in a pattern following the surface contour of burner top surface  90 . 
     FIGS. 4 and 5 show particular aspects of burner  42  in one preferred embodiment selected for illustration. Burner  42  includes a central combustion disc  145  and a peripheral flange  147 . Central combustion disc  145  includes ports  144  and a disc edge portion  149 . Disc edge portion  149  connects to flange  151 . Flange  151  includes a sloped inner wall  153  and an exterior wall  155 . Exterior wall  155  is shaped and configured to closely conform to the upper portion of skirt  32  and, in particular, to conform to reduced portion  34 , thereby providing a tight fit. Flange  151  also contains a pilot opening  157  through which igniter  80  (FIG. 1) extends inwardly toward central combustion disc  145 . It should be noted that although burner  42  shown in FIGS. 4 and 5 is depicted as a single integral burner, multiple piece burners  42  are within the scope of the invention. For example, central combustion disc  145  and peripheral flange  147  can be made separately for ease of manufacture. Similarly, the material of manufacture for central combustion disc  145  and peripheral flange  147  could be different, although employing the same material is preferred. Further, burner  42  may be molded or cast or formed by any of a number of processes. 
     FIGS. 6 and 7 show burner shelf  36  from top plan and side elevational views. Burner shelf  36  includes a vertically oriented flange  38  that is air tightly fixed to skirt  32 . Burner shelf  36  further includes a horizontally oriented ledge  159  upon which burner  42  rests. In particular, the bottom surface of peripheral flange  147  rests on ledge  159 . 
     Burner top surface  90  provides a pattern of radiation directing the heat of combustion at tank bottom wall  24  and not at skirt  32  as is typical of burners in many water heaters made and sold throughout the United States. This results in at least two significant advantages. First, maximum usable heat is directed to tank  12  containing the water to be heated. Second, the temperature of skirt  32  surrounding combustion chamber  44  is kept low. Moreover, peripheral flange  147  serves as a refractory to severely reduce heat from radiating outwardly of the water heater. Special insulation techniques involving use of high temperature insulation material are therefore not required. Thus, the body of insulation  98  surrounding water tank  12  and combustion chamber  44  can be a single body of foamed in place insulation. In many typical prior art water heaters, foamed in place insulation  98  is used around the tank  12  and a separate body of insulation, such as fiberglass or special heat resistant foam, is used around combustion chamber  44 . These extra efforts, different materials and construction techniques, all of which are costly and inefficient, are unneeded. 
     Drape structure  66  is also useful in submerged combustion chamber type water heaters such as that shown in FIGS. 8 and 9. A cylindrical burner  242  is positioned within a cylindrical combustion chamber  244 . Burner  242  includes a multiplicity of ports  144  in the same manner as burner  42  previously described. Ports  144  are located around and along the circumference of burner  242 , which also has a top surface  90 . Burner  242  is fed air and fuel through an air and fuel proportioner  254  similar to air and fuel proportioner  54  previously described. The primary difference resides in the cylindrical burner structure  242  being mounted on the end of the air and fuel proportioner  254 . Fuel and air travel through tube  26  and into burner chamber  286 . Burner chamber  286  is formed completely on the top and bottom by burner  242  and on the ends by tube  256  on one side and end closure  261  on the other side. Drape  66 , nozzle  82 , and other elements operate in substantially the same manner. The fuel and air mixture exit ports  144  and top surface  90  where combustion occurs all around the circumference of burner  242 . Radiant heat radiates radially outwardly from top surface  90  into contact with tank bottom wall  224 . 
     As can be seen in FIG. 1, the operation of water heater  10 , which is apparent to the end user, is similar in many aspects to the operation of the conventional water heater. When hot water is required, thermostat  72  provides fuel to air and fuel proportioner  54  which is burned within combustion chamber  44  and heat extracted in combustion chamber  44  and flue  26 . When the water in tank  12  is heated, thermostat  72  interrupts the flow of gas to nozzle  82  and combustion ceases. Because hot water is contained within the tank, a draft through the water heater is maintained and the air and fuel mixture contained within burner chamber  86  is drawn up through burner  42  to be combusted prior to the extinguishing of combustion on the top surface  90  of burner  42 . 
     However, operation of a water heater in accordance with the invention has several significant advantages. Efficiency is improved. Heat is primarily directed to the water containing tank and is not directed to skirt  32  where it would be wasted. Foam of the type used as insulation for tank  12  can be used around the combustion chamber resulting in better insulation and better efficiency. Burner  42  acts as a flame arrester preventing the migration of combustion into burner chamber  86 . Drape  66  assists in minimizing the likelihood of the escape of minor amounts of gas when combustion is initiated or terminated. The initial or terminal portion of gas dispensed from nozzle  82  will be contained within tube  56  to be drawn into the water heater by the draft of water heater  10  even when the water heater is not in operation. 
     Importantly, a water heater constructed in accordance with the present invention is less expensive to manufacture than a conventional water heater. No burner separate from the combustion chamber need be constructed. No radiant heat reflector sheet needs to be positioned below the burner as the burner itself acts to localize radiation of heat upwardly towards the bottom of the water containing tank. Standby losses are also minimized in the current design as only primary air is being used. Primary air is that drawn through the burner for use directly in the combustion process as opposed to secondary air which is drawn around the burner and used to cool the burner as well as sometimes in the combustion process. 
     The invention has been described with reference to preferred embodiments. Modifications and alterations will occur to others upon the reading and understanding of this specification and it is my intention to include such modifications and alterations insofar as they come within the scope of the appended claims. For example, their materials, shapes and sizes may be substituted for a number of the components of the water heaters shown herein. Metal or plastic jackets may be used. Various types of foam forming insulation materials may be employed. Various foaming techniques and processes may be utilized in addition to different types of water tanks, high efficiency flues, igniters, thermostats, gas control devices and the like.