Patent Publication Number: US-10788266-B2

Title: Kiln

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention is related to a heating apparatus, and more particularly to a kiln. 
     2. Description of Related Art 
     Conventional kilns are adapted for cooking food, such as baking pizza, roasting chicken, stewing vegetables, etc. The stove of conventional kilns is usually built by stacking stone material, and an entry is formed at the front side of the stove to communicate with an inside of the cavity. During the stove is in use, woods are placed into the cavity via the entry and then be ignited to heat the cavity. When the cavity is heated to a temperature suitable for baking food, food ingredients are provided into the cavity via the entry so as to cook the food. 
     The stove of conventional kilns further includes an exhaust pipe adapted to exhaust waste air out of the stove. However, the exhaust pipe only exhausts air through chimney effect, and only provides a limited exhaust effect which could not effectively improve a circulation of the hot air flow inside of the stove, thereby reducing a heating efficiency of the kilns. 
     Therefore, there is a persisting need for an improvement on the design of the conventional kilns so as to overcome the above drawbacks. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the above, an object of the present invention is to provide a kiln capable of exhausting air efficiently. 
     The present invention provides a kiln which includes a stove and a heat source wherein the stove includes a chamber, an air guide structure, an exhaust pipe and a heat storage member. The chamber includes a cavity, an entry, and an air outlet. The cavity includes a front section and a rear section, wherein the front section communicates with the entry, and the rear section is away from the entry. The air outlet is located between a top of the front section of the cavity and the entry. The air guide structure is disposed at the top of the front section of the cavity, and the air guide structure communicates with the air outlet. The air guide structure includes a guide plate, wherein the exhaust pipe is disposed above the guide plate, and an exhaust channel is formed by the guide plate of the air guide structure and the exhaust pipe. The heat storage member covers an exterior of the cavity which is corresponding to the top of the front section of the cavity, and contacts the air guide structure. The heat source is disposed in the stove and adapted to heat the cavity. 
     The advantage of the present invention is that by transferring part of the heat of the heat storage member to the interior of the air guide structure, the exhaust channel could be heated to form rising of steams which generates an upward pulling force to increase an exhaust rate of the hot air flow, whereby the exhaust efficiency could be improved, and the circulation result of the hot air flow inside of the cavity could be enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which 
         FIG. 1  is a perspective view of a kiln of a first embodiment according to the present invention; 
         FIG. 2  is an exploded view of the kiln of the first embodiment; 
         FIG. 3  is a perspective view of the door of the first embodiment; 
         FIG. 4  is a perspective view of the cavity of the first embodiment; 
         FIG. 5  is a cross-sectional view of the kiln of the first embodiment; 
         FIG. 6  is a schematic view of the thermal insulation structure of the first embodiment; 
         FIG. 7  is a partial cross-sectional view of the kiln of first the embodiment; 
         FIG. 8  is a perspective view of the combustion device of the first embodiment; 
         FIG. 9  is an exploded view of the combustion device of the first embodiment; 
         FIG. 10  is a schematic view showing that inside of the cavity of the kiln as illustrated in  FIG. 1  is being heated; 
         FIG. 11  is a perspective view of a combustion device of a second embodiment according to the present invention; 
         FIG. 12  is a partial perspective view of the combustion device of the second embodiment; 
         FIG. 13  is a perspective view of a kiln of a third embodiment according to the present invention, wherein a thermal insulation structure and a heat conductive structure are omitted; 
         FIG. 14  is a cross-sectional view of the kiln of the third embodiment; 
         FIG. 15  is a schematic view of a kiln of a fourth embodiment; and 
         FIG. 16  is a schematic view of a kiln of a fifth embodiment according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following illustrative embodiments and drawings are provided to illustrate the the present invention and its advantages and effects so it can be clearly understood by persons skilled in the art after reading the disclosure of this specification. 
     As illustrated in  FIG. 1  to  FIG. 10 , a kiln  100  of a first embodiment according to the present invention includes a stove  10 , a housing  36 , a door  38 , and a heat source which is a combustion device  40  as an example. 
     The stove  10  includes a cavity  12  and an entry  14 . The cavity  12  includes a front section  122  and a rear section  124 . The front section  122  communicates with the entry  14 , and a top wall surface at the front section  122  tilts toward the entry  14  downwardly. The rear section  124  is away from the entry  14 . An inner wall surface  124   a  is located at the rear section  124  and faces the entry  14 . A top wall surface at the rear section  124  tilts upwardly in a direction away from the inner wall surface  124   a . The cavity  12  further includes a middle section  126  which is located between the front section  122  and the rear section  124 . A top wall surface at the middle section  126  is higher than those of the front section  122  and the rear section  124 , wherein a maximum distance L between the top wall surface and a bottom of the middle section  126  along a direction from the front section  122  to the rear section  124  remains the same (as shown in  FIG. 5 ). That is, the maximum distance L between the between the top wall surface and the bottom of the middle section  126  remains as a constant in the middle section. The top wall surface at the rear section  124  tilts downwardly from the middle section toward a direction away from the entry  14 . 
     In the current embodiment, the stove  10  includes a chamber  16 , an air guide structure  18 , a heat storage member  22 , a thermal insulation member  24 , and a base  28 . Wherein, the chamber  16  is a substantially arch shape and made of metal such as stainless steel. A front end of the chamber  16  is open, and the entry  14  is formed at the front end of the chamber  16 . A rear end of the chamber  16  is closed, and includes the inner wall surface  124   a . The cavity  12  is within the chamber  16 . The chamber  16  is disposed on the base  28 , wherein the chamber  16  includes a main body  162 , a first inclined plate  164  and a second inclined plate  166 . A middle part  162   a  is formed on a top of the main body  162 , wherein the first inclined plate  164  and the second inclined plate  166  are joined to a front end and a rear end of the middle part  162   a  respectively. The first inclined plate  164  is corresponding to the front section  122  of the cavity  12 , the middle part  162   a  is corresponding to the middle section  126  of the cavity  12 , and the second inclined plate  166  is corresponding to the rear section  124  of the cavity  12 . An inner surface of the first inclined surface  164  constitutes the top wall surface of the front section  122 , while an inner surface of the second inclined plate  166  constitutes the top wall surface of the rear section  124 . 
     An air outlet  164   a  is formed on the first inclined plate  164  of the chamber  16 , wherein the air outlet  164   a  communicates with the entry  14  and is disposed between the top of the front section  122  of the cavity and the entry  14 . The air guide structure  18  is disposed in the chamber and located at the top of the front section  122  of the cavity  12 , wherein the air guide structure  18  communicates with the air outlet  164   a . In the current embodiment, the air guide structure  18  includes a guide plate  182  and a lid plate  184 . The guide plate  182  is joined to the first inclined plate  164 , wherein an angle between the guide plate  182  and the first inclined plate  164  is smaller than 90 degrees. The lid plate  184  is an arch shape, wherein two sides of the lid plate  184  are joined to the chamber  16 , and an inner surface of the lid plate  184  is joined to a peripheral edge of the guide plate  182 . A space S 1  is enclosed by the lid plate  184 , the guide plate  182 , and the first inclined plate  164 . The space S 1  is adapted to receive the heat storage member  22 . An exhaust pipe  20  is joined to the lid plate  184  and disposed above the air guide structure  18 . The guide plate  182  tilts upwardly from the air outlet  164   a  toward a direction away from the entry  14 . Whereby, an exhaust channel E is formed by the guide plate  182  of the air guide structure  19  and the exhaust pipe  20 . The heat storage member  22  covers the first inclined plate  164 , i.e., the heat storage member  22  is disposed at an exterior of the chamber  16  at the top of the front section  122  of the cavity  12 , and at least part of the heat storage member  22  is located in the space S 1  and contacts the air guide structure  18 . In the current embodiment, part of the heat storage member  22  is located in the space S 1 , while another part of the heat storage member  22  protrudes out of the space S 1 , and the air guide structure  19  contacts an exterior surface of the guide plate  182 . Preferably, a thermal conductivity of the heat storage member  22  is equal to or greater than 0.7 W/(mK), and a heat storage density thereof is equal to or greater than 1 KJ/m 3 K. In the current embodiment, the thermal conductivity of the heat storage member  22  is 0.8˜0.93 W/(mK), and the heat storage density thereof is 1.4 KJ/m 3 K. The heat storage member  22  includes a plurality of stacked particles (e.g. sands, or pebbles), and the air fills the gaps between the stacked particles. By enclosing within the space S 1 , the particles could be prevented from sliding down. 
     In addition, the thermal insulation structure  24  covers the exterior of the chamber  16  which is corresponding to the rear section  124  and the middle section  126 , and is disposed at an outer peripheral of the heat storage member  22 . A heat insulation effect of the thermal insulation structure  24  is better than that of the heat storage member  22 , whereby a temperature at the middle section  126  of the cavity  12  is higher than that of the front section  122  so as to increase heat convection. In practice, the heat storage member  22  also could be omitted, and part of the thermal insulation structure  24  could extend to a position where the heat storage member  22  locates. As illustrated in  FIG. 6 , the thermal insulation structure  24  includes, from outward to inward, a first reflection layer  241 , a barrier layer  242 , a thermal insulation layer  243 , a second reflection layer  244 , a heat storage layer  245 , and a heat conduction layer  246 . 
     The thermal conductivity of the heat conduction layer  246  is greater than that of the heat storage layer  245 . The heat conduction layer  246  is adapted to absorb part of heat from the chamber  16  rapidly and transfer the heat to the heat storage layer  245 , whereby the heat could be stored into the heat storage layer  245 . Wherein, the thermal conductivity of the heat conduction layer  246  is equal to or greater than four times of that of the heat storage layer  245 . Preferably, the thermal conductivity of the heat conduction layer  246  is equal to or greater than 35 W/(mK), and more preferably, greater than 40 W/(mK). In the current embodiment, the thermal conductivity of the heat conduction layer  246  is between 40.096 and 46.285 W/(mK). Meanwhile, the thermal conductivity of the heat storage layer  245  is preferably equal to or smaller than 8.5 W/(mK), and more preferably smaller than 8.3 W/(mK). In the current embodiment, the thermal conductivity of the heat storage layer  245  is between 1.689 and 8.203 W/(mK). 
     The second reflection layer  244  includes a second heat reflection surface  244   a  which is made of metal, and faces the heat storage layer  245  and the chamber  16 . The second heat reflection surface  244   a  could reflect radiation heat back to the chamber  16 , and thereby to stop 70% of the heat from dissipating out and could block heat convection as well. When heat storage layer  245  is thermally saturated, the heat dissipates from the heat storage layer  245  would transfer back to the chamber  16  through the heat conduction layer  246 , and thereby to provide heat insulation effect for the chamber  16 . The thermal conductivity of the second reflection layer  244  is preferably between 0.62 and 0.72 W/(mK). In the current embodiment, the thermal conductivity of the second reflection layer  244  is 0.67 W/(mK). 
     In addition, the heat conducted from the second reflection layer  244  would be retained in the thermal insulation layer  243 . The thermal conductivity of the thermal insulation layer  243  is equal to or smaller than that of the heat storage layer  245 . Preferably, the thermal conductivity of the thermal insulation layer  243  is lower than that of the heat storage layer  245 . The barrier layer  242  is adapted to insulate the heat convecting from the thermal insulation layer  243  so as to barrier the convection heat and reduce the heat dissipation from thermal insulation layer  243 . The thermal conductivity of the barrier layer  242  is greater than that of the thermal insulation layer  243  and smaller than that of the heat storage layer  245 . The first reflection layer  241  includes a first heat reflection surface  241   a  which is made of metal, and faces the thermal insulation layer  243  and the chamber  16 . The first heat reflection surface  244   a  could reflect the heat radiated from the thermal insulation layer  243  back to the chamber  16 . Preferably, the heat conductivity of the thermal insulation layer  243  is equal to or smaller than 0.2 W/(mK). In the current embodiment, the heat conductivity of the thermal insulation layer  243  is between 0.04 and 0.16 W/(mK). Preferably, the thermal conductivity of the barrier layer is between 0.4 and 0.6 W/(mK). In the current embodiment, the thermal conductivity of the barrier layer  243  is between 0.483 and 0.551 W/(mK). 
     A cladding layer  26  could be further disposed on the thermal insulation structure  24 , wherein the cladding layer covers the thermal insulation structure  24  and the heat storage member  22 , whereby to fix the thermal insulation structure  24  and the heat storage member  22 . However, the cladding layer  26  also could be omitted. 
     In the current embodiment, the first reflection layer  241  and the second reflection layer  244  could be made of aluminum foil, which not only could reflect the radiation heat but also could effectively block the heat source, and further could provide water resistance and moisture resistance. The barrier layer  242  could include refractory material, such as lime. The thermal insulation layer  243  includes organic fiber material (e.g. ceramic fiber, glass fiber, rock wool, etc.) which is filled with air, thereby forming the thermal insulation layer  243  with a thermal conductivity similar to air so as to insulate heat. The heat storage layer  245  could be formed by mixing materials of clay, stone material particles or powder, refractory material, cement, etc. The heat conduction layer  246  could be formed by mixing materials of silicon carbide, magnesium oxide, refractory material, cement, etc. 
     In practice, except the thermal insulation structure having a multi-layer arrangement as described above, the thermal insulation structure  24  also could have, but is not limited to, other types of arrangement methods which would be illustrated below: 
     Type (1): at least including the heat conduction layer  246 , the heat storage layer  245 , and the second reflection layer  244 , wherein the heat conduction layer  246  contacts the chamber  16 , and the heat storage layer  245  is disposed between the second reflection layer  244  and the heat conduction layer  246 ; 
     Type (2): including the arrangement as mentioned in type (1), and further including the first reflection layer  241  and the thermal insulation layer  243  on the second reflection layer  244 ; alternatively, further including the barrier layer  242  in addition to the first reflection layer  241  and the thermal insulation layer  243 , wherein the barrier layer  242  is disposed between the thermal insulation layer  243  and the first reflection layer  241 ; 
     Type (3): at least including the first reflection layer  241  and the thermal insulation layer  243 , wherein the thermal insulation layer  243  is disposed between the first reflection layer  241  and the chamber  16 ; 
     Type (4): in addition to the first reflection layer  241  and the thermal insulation layer  243 , further including the barrier layer  242 , wherein the barrier layer  242  is disposed between the thermal insulation layer  243  and the first reflection layer  241 ; 
     Type (5): in addition to the first reflection layer  241  and the thermal insulation layer  243 , further including the heat storage layer  245 , wherein the heat storage layer  245  is disposed between the thermal insulation layer  243  and the chamber  16 ; 
     Type (6): including the arrangement as mentioned in type (5), and further including the second reflection layer  244 , wherein the second reflection layer  244  is disposed between the thermal insulation layer  243  and the heat storage layer  245 ; alternatively, further including the heat conduction layer  246  in addition to the second reflection layer  244 , wherein the heat conduction layer  246  is disposed between the heat storage layer  245  and the chamber  16 , and contacts the chamber  16 ; and 
     Type (7): including the arrangement as mentioned in type (5), further including the heat conduction layer  246 , wherein the heat conduction layer  246  contacts the chamber  16 , and the heat storage layer  245  is disposed between the heat conduction layer  246  and the thermal insulation layer  243 . 
     In the current embodiment, the thermal insulation structure  24  is utilized in a heater which is the kiln  100  as an example, but it is not limited thereto. The heat insulation structure also could be applied to chambers of other types of heaters, such as an oven, a baking apparatus, a heating apparatus, a thermal insulation apparatus, etc. Wherein, a heat insulation effect could be further achieved if the housing  36  is disposed on the exterior of the insulation structure  24 , and an air gap is formed therebetween as described in the current embodiment. 
     The stove  10  is disposed on a stage  30 . In more detail, the stove  10  is mounted on the stage  30  via the base  28 , which at least includes a carrier plate  282  and a thermal insulation plate  284 . In the current embodiment, the base  28  includes two carrier plates  282  which face the cavity  12  and are adapted for placing food ingredients. The thermal insulation plate  284  is disposed under the carrier plate  282  and across a plurality of frames of the stage  30 . In practice, the carrier plate  282  could be rock board as an example, and the thermal insulation plates could be rock wool as an example. An air isolation is disposed between the stage  30  and the base  28  for heat insulation. A gas regulation valve is disposed in the stage  30  (not shown), wherein the gas regulation valve includes a knob  32  disposed at a front side of the stage  30  for a user to adjust a flow rate of gas manually. An ignition switch  34  is further disposed at the front side of the stage  30 . 
     The housing  36  is joined to the stage  30  and surrounds the stove  10 , wherein an isolation space S 2  is formed between the housing  36  and the stove  10 . The housing  36  is made of metal such as stainless steel and includes a front plate  362 , a rear plate  364 , and a cover  366 . Wherein, the front plate  362  is joined to the stage  30  and disposed at a front side of the entry  14  of the stove  10 ; the front plate  362  includes a feeding opening  362   a  which communicates with the entry  14  and the exhaust channel E formed by the guide plate  182  and the exhaust pipe  20 . The front plate  362  and the stove  10  are spaced apart with a distance D 1 . The rear plate  364  is joined to the stage  30  and is disposed at a rear side of the stove  10 . The rear plate  364  and the stove  10  are spaced apart with a distance D 2 . The cover  366  includes a front edge  366   a  and a rear edge  366   b  which are respectively joined to the front plate  362  and the rear plate  364 . A through hole  366   c  is formed on the cover  366  above the front section  122  of the cavity  12 , wherein the through hole  366   c  is adapted for penetration of the exhaust pipe  20 . The cover  366  and the stove  10  are spaced apart with a distance D 3 . The isolation space S 2  consists of the distance D 1 , D 2  and D 3  which are respectively formed between the stove  10  and the front plate  362 , the rear plate  364 , and the cover  366 , and the isolation space S 2  is adapted to insulate heat and avoid heat dissipating from the stove  10  to the housing  36  directly whereby in designing a compact kiln, the metallic chamber could provide a sufficient support to sustain the thermal insulation structure, which could effectively improve the drawback of being difficult to be scaled down in size corresponding to conventional kilns which are formed by stacking thick stone material. In addition, a flameproof layer  368  could be further disposed on an interior surface of the cover  366  of the cover  366 . Wherein, the flameproof layer  368  is formed by a flameproof coating and adapted to reduce an amount of residual heat dissipated from the stove  10  to the exterior of the cover  366  so as to avoid an over-high temperature on the exterior surface of the cover  366 . In the compact size design, the flameproof layer  368  also could prevent the user from being burned by touching the cover  366 . Furthermore, the flameproof layer  368  also could be disposed on interior surfaces of the front plate  362  and the rear plate  364 , which could reduce the amount of residual heat dissipated from the stove to the housing  36  as well. 
     The door  38  is adapted to cover at least one portion of the entry  14 . The door  38  includes a main plate  382 , at least one shield  384 , and a blocking plate  386 , wherein the main plate  382  is detachably joined to the stove  10  at the entrance  14 ; the main plate  382  includes a plurality of first vents  382   a  and a plurality of second vents  382   b ; the plurality of first vents  382   a  are laterally arranged at the bottom of the main plate  382 ; the plurality of second vents  382   a  are divided into two groups, and each of the two groups is disposed above the plurality of first vents  382   a ; the second vents  382   b  of each group are arranged in a circular shape. In the current embodiment, the door  38  includes two shields  384 , each of which is movably disposed on an exterior surface of the main plate  382  corresponding to each group of the second vents  382   b . Each of the shields  384  includes a plurality of adjusting holes  384   a . By turning the shields  384  to close the plurality of second vents  382   b  or partially shield the plurality of second vents  382   b , an air flow passing through the plurality of second vents  382   b  could be adjusted via the adjusting holes  384   a . The blocking plate  386  is joined to an inner edge of the main plate  382 , wherein the blocking plate  386  would close the air outlet  164   a  when the door  38  is at the entry  14  whereby the exhaust channel E formed by the air guide structure  18  and the exhaust pipe  20  would be isolated from the interior of the cavity  12 . 
     The combustion device  40  is disposed within the cavity  12  at the rear section  124  and includes at least one burner  42 , a supporting assembly  46 , and an infrared ray generation assembly  54 . In the current embodiment, the combustion device  40  includes a plurality of burners  42 , wherein the plurality of burners  42  jointly communicate with a flow divider  44  via a plurality of terminals thereof, and then communicate with a gas regulation valve disposed in the stage  30  through the flow divider  44 . A flame outlet  422  is disposed at another terminal of each of the burners  42 , and the burners  42  are adapted to burn gas to generate flames through the flame outlets  422 . An ignition assembly  56  is disposed beside the burners  42 , wherein the ignition assembly  56  is connected to the ignition switch  34  and adapted for igniting gas supplied from the flame outlet  422 ; the ignition assembly  56  includes an ignitor and a pilot pipeline. An axis i which passes through a corresponding center of each flame outlet  422  is extended along a longitudinal direction of each of the burners  42 . 
     The supporting assembly  46  includes a cover plate  48  which is substantially a bowl shape and disposed above the burners  42 . In a vertical direction, the cover plate  48  is located at a position with a height greater than a half of the distance L between the top and the bottom of the middle section of the cavity  12  (as shown in  FIG. 5 ). The cover plate  48  includes at least one hollow area. In the current embodiment, there are a plurality of hollow areas, including an opening  482  and a plurality of holes  484 , wherein the opening  482  is corresponding to the flame outlet  422  of each of the burners  42 . The infrared ray generation assembly  54  is disposed in the supporting assembly  46 , and the cover plate  48  is disposed between the infrared ray generation assembly  45  and the burners  42 . In the current embodiment, the infrared ray generation assembly  54  is located above the cover plate  48 , such that the flames generated by the burners would pass through the opening  482  to apply on the infrared ray generation assembly  54 , which makes the infrared ray generation assembly  54  generate infrared ray. The infrared ray generation assembly  54  includes an emission surface  542   a  to emit infrared ray which faces the cover plate  48  and is corresponding to the opening  482  and the holes  484 , thereby enabling the generated infrared ray to pass through the opening  482  and the holes  484 . In practice, the emission surface  542   a  is at least corresponding to the holes  484 . An angle is formed between the emission surface  542   a  and the axis, wherein the angle is between 100 and 135 degrees. In addition, another function of the cover plate  48  is to maintain a temperature of the infrared ray generation assembly  54  so as to reduce heat dissipation of the infrared ray generation assembly  54 . 
     In the current embodiment, the supporting assembly  46  further includes a supporting plate  50  and another cover plate  52 . Wherein, the supporting plate  50  includes a first part  502  and a second part  504 ; the second part  504  is located above the first part  502 , and an obtuse angle is formed between the first part  502  and the second part  504 ; the first part  502  and the inner wall surface  124   a  of the rear section  124  are spaced apart with a gap a 1 , while the second part  504  and the top wall surface of the rear section  124  are spaced apart with a gap a 2 . The burners  42  are mounted to the first part  502 , and another cover plate  52  is mounted to second part  504  and joined to the cover plate  48 , whereby the two cover plates  48 ,  52  jointly form a containing space S 3 . The infrared ray generation assembly  54  is disposed in the containing space S 3 . Said another cover plate  52  also includes a plurality of holes  522 , and also could maintain the temperature of the infrared ray generation assembly  54  so as to reduce heat dissipation of the infrared ray generation assembly  54 . 
     The infrared ray generation assembly  54  includes an infrared ray generation mesh  542  and a reflection plate  544 . The infrared ray generation mesh  542  includes two surfaces which are opposite to each other, wherein one of the two surfaces is the emission surface  542   a , while the other surface is the emission surface  542   b  which faces a reflection surface  544   a  of the reflection plate  544 . The reflection surface  544   a  is an arc surface which is concaved toward a direction away from the infrared ray generation mesh  542 , whereby the infrared ray emitted by the other emission surface  542   b  could be centralized and reflected downwardly. The cover plate  48  includes an exterior surface having an arc shape and is protruded outwardly toward a direction away from the infrared ray mesh  542  of the infrared ray generation assembly  54 . The cover plate  48  also could generate infrared ray by heating, while the arc-shape exterior surface thereof could increase a range covered by the infrared ray. In the current embodiment, the infrared ray mesh  542  includes a plurality of grids, each of which includes a size smaller than that of each of the holes  484 ,  522  of the cover plates  48 ,  52 . The flame outlets  422  of the burners  42  are corresponding to different portions of the infrared ray generation mesh  542  respectively. 
     The infrared ray generation mesh  542  could be an alloy mesh, such as heat-resistant steel (e.g. FCHW2) mesh, iron-chromium-aluminum alloy mesh, iron-nickel-aluminum alloy mesh, etc. The two cover plates  48 ,  52  could be made of different stainless steel material. The reflection plate  544  could be made of metal alloys which reflect infrared ray. In practice, the reflection plate  544  also could be omitted. 
     The infrared ray generation assembly  54  and the cover plate  48  constitute a heating device of the heat source and are adapted to generate heat for heating the cavity  12 , which could heat the food ingredients from top down so as to make surfaces of the food ingredients to be heated uniformly. 
     With the aforementioned structure, a heating method for the kiln  100  according to the present invention includes the following steps. 
     First, the user adjusts the knob  32  of the gas regulation valve and the ignition switch  34  to control the burners  42  to generate flames. As illustrated in  FIG. 7  to  FIG. 10 , after generating the flames, the infrared ray generation assembly  54  is heated by the flames to generate infrared ray. In the current embodiment, the flames apply to the infrared ray generation mesh  542 , which makes the two emission surfaces  542   a ,  542   b  to emit infrared ray. Wherein, the infrared ray emitted by the emission surface  542   a , which is close to the cover plate  48 , irradiates on the carrier plate  282  through the holes  484  of the cover plate  48 , thereby providing a larger heating area. Meanwhile, the infrared ray emitted by the emission surface  542   b  which is close to the reflection plate  544  is reflected to the infrared ray generation mesh  542  by the reflection surface  544   a  of the reflection plate  544 , and irradiates on the carrier plate  282  through the grids of the infrared ray generation mesh  542 , and the holes  484  of the cover plate  48  so as to increase an intensity of the infrared ray irradiated on the carrier plate  282 . Since the angle formed between the axis i of the burners and the emission surfaces  542   a ,  542   b  of the infrared ray generation mesh  542  is between 100 and 135 degrees, the flames could be uniformly acted on the emission surfaces  542   a ,  542   b  of the infrared ray generation mesh  542 , which achieves an optimal performance for the infrared ray emission. The flames generated by the burners  42  also apply on the cover plate  48  to make the cover plate  48  to generate infrared ray, and thereby to increase the intensity of the infrared ray irradiated on the carrier plate  282 . 
     The temperature of the infrared ray generation assembly  54  is maintained to be between 900 and 100° C., and the infrared ray generation assembly  54  is blocked by the cover plate  48 , which enables the infrared ray having an optimum range of infrared ray wavelength to pass through the holes  484  of the cover plate  48 . Preferably, a wavelength range is between 4 to 8 μm, which could provide a better transmission efficiency for the heated food ingredients on the carrier plate  282  so as to heat an interior of the food ingredients. A temperature on the exterior surface of the cover plate  48 , i.e., the surface which faces toward a direction away from the infrared ray generation assembly  54 , is between 600 and 800° C. 
     The flames generated by the burners  42  penetrates upwardly through the holes  484 ,  522  of the two cover plates  48 ,  52  to form an open fire at the top of the middle section  126 . The open fire is adapted to heat the surface of the food ingredients, such as scorching the surface of the food ingredients to form golden color. Whereby, the combustion device  40  could have a larger heating area so as to achieve a uniform heating and increase a heating efficiency. 
     Since coke is formed on the infrared ray generation assembly  54  when gas burns, and an over-heated steam is generated from the steam formed by burning the gas, a reaction to generate water-gas which includes hydrogen and carbon monoxide would occur when the over-heated steam passes through the hot coke having a temperature between 900 and 1100° C. on the infrared ray generation assembly  54 , which provides an auxiliary fuel to the gas burning. 
     For example, water-gas is generated when the steam passes the high-temperature coke according to equation 1:
 
C+H 2 O→H 2 +CO−113.4KJ  (1)
 
     Wherein the generation heat equals to −113.4 KJ, which represents that equation 1 is an endothermic reaction. However, the generated hydrogen and carbon monoxide would react with the steam formed in the combustion according to equation 2, which is an exothermic reaction.
 
CO+H 2 O→H 2 +CO 2 +42.71KJ; H2+½O 2 →H 2 O+237.4KJ  (2)
 
     A total generation heat of equation 2 equals to 280.11 KJ. An overall reaction heat of equation 1 and equation 2, which subtracts 113.4 KJ from 280.11 KJ, would be 166.71 KJ. It could be understood that the generation of the water-gas when the over-heated steam passes through the coke on the infrared ray generation assembly  54  could increase a heating efficiency, whereby a consumption of gas could be reduced. The advantage of placing the infrared ray generation assembly  54  between the two cover plates  48 ,  52  is that the temperature of the infrared ray generation assembly  54  could be kept between 900 and 1000° C. which is necessary for generating the water-gas under a limited amount of gas consumption by utilizing the cover plates  48 ,  52  to maintain the temperature of the infrared ray generation assembly  54 . Meanwhile, the cover plates  48 ,  52  are concaved toward a direction away from the infrared ray generation assembly  54 , which enables part of the heat to be concentrated and reflected back to the infrared ray generation assembly  54 , thereby providing a better performance in maintaining the temperature. In contrast, simply utilizing the cover plate  48  also could maintain the temperature of the infrared ray generation assembly  54  between 900 and 1000° C., but the gas consumption thereof would be higher than that of the examples of utilizing the two cover plates  48 ,  52 . 
     A temperature of the overheated steam is about 300° C. and higher, wherein water molecules would become smaller water vapor which could penetrate food and dissolve fat at high temperature to increase a heating efficiency of cooking food ingredients, whereby the over-heated steam also could be adapted to heat food ingredients. Moreover, the water vapor generated from the food ingredients also would be heated to form over-heated vapor so as to further increase the heating efficiency. 
     The burners  40  creates a high-temperature zone at a higher position to make the hot air flow formed by combustion, i.e., the hot air flow formed by the heat generated from the heating assembly of the heat source, be guided downwardly by the wall surface of the top of the front section  122  of the cavity  12 , which facilitates the hot air flowing back to the burners  42  and reduces heat dissipation. Meanwhile, external air would be drawn in from the entry  14  as combustion-supporting air together with the flowing-back of the hot air flow. By mixing the external air with the hot air flow which flows back, a temperature of the air flowing back to the burners  42  could be increased to avoid cold air directly flowing back to the burners  42 , whereby heat dissipation could be reduced so as to increase heat efficiency. Moreover, the thermal insulation structure  24  covers the chamber  16 , which could maintain the temperature inside of the cavity  12 , prevent heat dissipating from the combustion device  40  through the chamber  16 , and thereby to keep the temperature of the infrared ray assembly  54  between 900 and 1100° C. and reduce the gas consumption. The heat storage member  22  would absorb part of the heat from the top of the front section  122  of the cavity  12 , which makes the temperature at the top of the front section  122  be lower than the temperature at the top of the middle section  126  so as to drive the hot air to flow downwardly whereby, the flowing back of the hot air could be increased, and the heating effect improved. Moreover, it is also favorable to keep the temperature of the infrared ray generation assembly  54  between 900 and 1100° C. and reduce the gas consumption. 
     With the heating method as described above, the food ingredients in the chamber could be heated sufficiently, and the gas consumption could be reduced as well. 
     Furthermore, a retained air flow could be generated in the gap a 1  and the gap a 2 , which are respectively formed between the first part  502  of the supporting plate  50  and the inner wall surface  124   a  at the rear section  124  of the cavity  12 , and between the second part  504  of the supporting plate  50  and the top wall surface at the rear section  124  of the cavity  12 , to pull the hot air flow, which flows back, to move upwardly again, and to thereby make a circulation effect of the hot air flow in the cavity  12  become better. 
     In addition, redundant hot air flow would be exhausted from the outlet  164   a  to the outside through the air guide structure  18  and the exhaust pipe  20 . During the exhaust process, cold air would be drawn in from the outside via the feeding opening  362   a  of the front plate  362  and the entry  14 , and then be pulled up to the air guide structure  18  and the exhaust pipe  20  through the air outlet  164   a  so as to lower a temperature of the front plate  362  and a temperature of the exhaust pipe  20 , thereby avoiding the user to be burned by the front plate  362  and the exhaust pipe  20 . Since the heat storage member  22  contacts the air guide structure  18 , part of the heat of the heat storage member  22  would be transferred to the air guide structure  18  to heat the exhaust channel E, which results in rising of steam as an upward pulling force to speed up an exhaust rate of the hot air flow, and thereby to increase the exhaust efficiency and improve the circulation effect of the hot air flow in the cavity. The guide plate  182  which tilts upwardly is also favorable to increase air guide performance such that the exhaust efficiency could be further improved. Meanwhile, the increase in the exhaust rate of the hot air flow also would increase the speed of cold air drawing into the air guide structure  18 , which could make the temperature of the front plate  362  and the exhaust pipe  20  become lower. The exhaust pipe  20  is located at the top of the front section  122  of the cavity  12 , which could make the exhaust path shorter, whereby the air flow could be exhausted out faster. 
     A combustion device  60  of a second embodiment according to the present invention is illustrated in  FIG. 11  and  FIG. 12 . The combustion device  60  of the second embodiment includes a basic structure similar to the combustion device  40  of the first embodiment, and further includes a steam generation assembly  62 , which is adapted to generate steam to be used as an over-heated steam for combustion. The steam generation assembly  62  includes a steam source which is a water tank  64  as an example, a first pipe  66 , and a second pipe  68 . Wherein, the water tank  64  is disposed at one side of the burners  42 . In more details, the water tank  64  is mounted on the first part  502  of the supporting plate  50 , and is located between the first part  502  and the burners  42 . The water tank  64  includes a water inlet  642  for filling water. The first pipe  66  is connected to a top of the water tank  64 , and two terminals of the first pipe  66  communicate with an interior of the water tank  64 . A section  662  of the first pipe  66  includes a plurality of spraying holes  662   a . In practice, there could be only one spraying hole  662   a , and the section  662  is located between the flame outlet  422  of the burners  42  and the reflection surface  542   a  of the infrared ray generation assembly  54 . Two terminals of the second pipe  68  are respectively connected to two sides of the water tank  64  and communicate with the interior of the water tank  64 . The second pipe  68  surrounds the burners  42 , and a section  682  of the second pipe  68  is located below the exterior surface of the cover plate  48 . The burners  42  are located between the section  682  of the second pipe  68  and the water tank  64 . The section  682  includes a plurality of spraying holes  682   a  which face toward the front section  122  of the cavity  12 . In practice, there could be only one spraying hole  682   a.    
     After heating of the water contained in the water tank  64  of the steam generation assembly  62 , the water becomes steam which would spray out from the spraying holes  662   a  of the first pipe  66 , wherein the steam could be either guided to the infrared ray generation mesh  542  by the first pipe  66  to be used as the over-heated steam for forming the water-gas, or be used as the over-heated steam for heating the food ingredients. The steam which sprays out from the spraying holes  682   a  of the second pipe  68  is mainly used as the over-heated steam for heating the food ingredients, however, also could be used as the over-heated steam for forming the water-gas. 
     With the steam generated from the steam generation assembly  62  as the source of the over-heated steam, the heating efficiency could be improved efficiently. In practice, the steam generation assembly  62  could only include the first pipe  66  or the second pipe  68 . On the other hand, the steam source also could be disposed outside of the cavity  12 , and the first pipe  66  and the second pipe  68  could be directly connected to the steam source. 
     As illustrated in  FIG. 13  and  FIG. 14 , a kiln  300  of a third embodiment according to the present invention includes a structure which is similar to that of the first embodiment, wherein the kiln  300  of the third embodiment is different from that of the first embodiment in that in the current embodiment, a first inclined plate  704 , and a second inclined plate  706  of a chamber  70  are respectively joined to a main body  702  of the chamber  70  with edges of the main body  702 , the first inclined plate  704 , and the second inclined plate  706 , which are to be joined, being bent in advance, which forms a plurality of ridges  70   a . The ridges  70   a  could reinforce the strength of the chamber  70  and avoid the heat storage member  22  or the thermal insulation structure  24  from sliding down effectively. For example, part of the heat storage member  22  which is outside of the space S 1  is surrounded by the plurality of ridges  70   a  at the periphery of the first inclined plate  704 , thereby avoiding the heat storage member  22  from sliding down from the first inclined plate  704 . Meanwhile, the ridges  70   a  at other positions of the chamber  70  could prevent the thermal insulation structure  24  from sliding down, which reinforces the joined strength of the chamber  70  and the thermal insulation structure  24 . 
     In the current embodiment, an exhaust pipe  72  includes an outer pipe  722  and an inner pipe  724 , wherein one end of the outer pipe  722  is connected to the housing  36 , and the outer pipe  722  is adapted to communicate the isolation space S 2  inside of the housing  36  with an outside of the cover  366 ; the inner pipe  724  penetrates through the through hole  366   c , and the inner pipe  366  is adapted to communicate the air guide structure  18  with the outside of the cover  18 . Whereby, the redundant hot air in the isolation space S 2  could be exhausted out through the outer pipe  722  so as to reduce heat dissipation from the isolation space S 2  to the housing  36  and lower the temperature of the front plate  362 . The configuration of the outer pipe  722  and the inner pipe  724  of the exhaust pipe according to the current embodiment also could be utilized in the first embodiment. 
     In addition, a carrier plate  74  of the current embodiment is a disc shape and is rotatably disposed on the bottom of the chamber  70 . In more details, a driving motor  78  is further disposed on a stage  76 . The driving motor  78  is connected to the carrier plate  74  via a rotation member  80  to drive the carrier plate  74  to rotate whereby the food ingredients disposed on the carrier plate  74  could be uniformly heated. The rotatable design of the carrier plate  74  of the current embodiment also could be utilized in the first embodiment. 
     As illustrated in  FIG. 15 , a kiln  400  of a fourth embodiment according to the present invention includes a structure which is similar to that of the first embodiment. The kiln  400  of the current embodiment is different from that of the first embodiment in that the gas regulation valve provided in the first embodiment is adapted for the user to adjust the gas flow rate of the burners  42  manually, but a control system is provided in the current embodiment to replace the manual adjustment instead. In the current embodiment, the control system of the kiln  400  includes a thermometer  82 , a flow rate regulation device  84 , and a control device  86 , wherein the flow rate regulation device  84  and the control device  86  are disposed in the stage  30 , which would be described in detail as follows. 
     The thermometer  82  is disposed in the cavity  12  to detect the temperature inside of the cavity  12 . In the current embodiment, the thermometer  82  is located at the middle section  126  of the cavity  12 . However, the thermometer  82  also could be disposed at the front section  122  of the cavity  12 . 
     The flow rate regulation device  84  communicates with at least one of the burners  42 , and a flow rate regulation valve  844  is controlled to adjust a gas flow of the at least one burner  42 . In the current embodiment, the flow rate regulation device  84  includes a channel valve  842  and a flow rate regulation valve  844 , wherein one end of the channel valve  842  is connected to the gas source; one end of the flow rate regulation valve  844  is connected to the channel valve  842 , and another end of the flow rate regulation valve  844  communicates with the burners  42 . The channel valve  842  could be controlled to close or open so as to shut or pass the gas. The flow rate regulation valve  844  could be controlled to regulate the gas flow to be transported to the burners  42 . 
     The control device  86  is electrically connected to the thermometer  82 , and the channel valve  842  and the flow rate regulation valve  844  of the flow rate regulation device  84 . The control device  86  is also electrically connected to the ignition assembly  56 , an input unit  88 , and a display unit  90 , wherein the input unit  88  is adapted for the user to input an ignition command, and a setting temperature; the display unit  90  is adapted to display a message. 
     After inputting the ignition command via the input unit  88  by the user, the control device  86  would control the ignition assembly  56  to ignite and the channel valve  842  to open so as to ignite the gas of the burners  42 . Then, the control device would control the flow rate regulation valve  844  of the flow rate regulation device  84  to adjust the outputted gas flow based on the inputted setting temperature and the temperature of the cavity which is detected by the thermometer  82 , and thereby to maintain the temperature inside of the cavity at a constant temperature range corresponding to the setting temperature. Whereby, an automatic temperature control could be realized. 
     In order to fulfill the object of infrared ray heating, the infrared ray generation assembly  54  of the combustion device  40  would generate infrared rays of a predetermined wavelength range which irradiate toward the middle section  126  and the front section  122  of the cavity  12  when the gas flow output from the flow rate regulation device  84  is above a predetermined flow rate. The predetermined wavelength range is between 4 and 9 μm. When the temperature detected by the thermometer  82  is between the constant temperature range or higher than an upper limit of the constant temperature range, the control device  86  would control the flow rate regulation valve  844  of the flow rate regulation device  84  to make the gas flow output from the flow rate regulation valve  844  be equal to or higher than the predetermined flow rate. Whereby, in addition to keep the cavity  12  at a constant temperature, the infrared ray generation assembly  54  also could generate infrared ray for heating food ingredients. If a maximum gas flow rate is determined as the gas flow output from the regulation device  84  when the regulation device  84  is being controlled, the predetermined flow rate is preferably equal to or higher than one-third of the maximum gas flow rate. 
     In the current embodiment, the kiln  400  further includes an infrared ray detector  92 , a flame sensor  94 , and a carbon monoxide detector  96  which are electrically connected to the control device  86  respectively. Wherein, the infrared ray detector  92  is disposed at the bottom of the middle section  126  of the cavity  12 , and adapted to detect the infrared ray emitted by the combustion device  40 . When the wavelength of the infrared ray detected by infrared ray detector  92  is between the predetermined wavelength range, the control device  86  would control the display  90  to display a prompt message (e.g. a light signal or a text message) to remind the user that the infrared ray suitable for penetrating food ingredients is already generated by the combustion device  40 . Of course, the infrared ray detector  92  also could be disposed at the front section  122  of the cavity  12 . 
     The flame detector  94  is disposed at the top of the middle section  126  of the cavity, and is higher than the infrared ray generation assembly  54 . When a flame is detected by the flame detector  94 , the control device  86  would control the display unit  90  to display a prompt message to remind the user that an open fire is already generated and could be used to heat the food ingredients. 
     The carbon monoxide detector  96  is disposed in the exhaust channel E, and adapted to detect a concentration of carbon monoxide in the air flow passing through the exhaust channel E. When the concentration of the carbon monoxide detected by the carbon monoxide detector  96  is higher than a predetermined value, the control device  86  would control the channel valve  842  of the flow rate regulation device  84  to shun the gas so as to avoid the concentration of the carbon monoxide contained in the exhausted gas from becoming too high to harm the human body. 
     As illustrated in  FIG. 16 , a kiln  500  of a fifth embodiment according to the present invention includes a structure which is similar to that of the fourth embodiment. Wherein, the kiln  500  of the fifth embodiment is different from that of the fourth embodiment in that a flow rate regulation device  98  of the current embodiment includes a plurality of gas switch valve  982 , which are electrically connected to a control device  99 . The plurality of gas switch valves  982  communicate with the burners  42  respectively, and could be controlled by the control device  99  to close or open respectively, and thereby to adjust the gas flow output to the burners  42 . When all of the gas switch valves are open, a gas flow output to the burners  42  is a maximum gas flow rate; when only one of the gas switch valves  982  is turned on, the gas flow output from the flow rate regulation device  98  is the predetermined flow rate which enables the combustion device  40  to generate the infrared ray of the predetermined wavelength range. When the temperature detected by the thermometer  82  is between the constant temperature range or higher than the upper limit of the constant temperature range, the control device  99  would control at least one of the gas switch valves  982  to open, whereby the infrared ray generation assembly  54  could be maintained at the temperature which enables the combustion device  40  to generate the infrared ray of the predetermined wavelength range. 
     In the current embodiment, when the temperature detected by the thermometer  82  is between the constant temperature range or higher than the upper limit of the constant temperature range, the control device  99  would control the gas switch valves  982  to open by turns so as to make the burners  42  generate flames sequentially. For example, if only the first gas switch valve  982  is turned on, the second gas switch valve  982  would be turned on after a period of time and then the first gas switch valve  982  would be turned off; the third gas switch valve  982  would be turned on after another period of time, and the second gas switch valve  982  would be turned off; thereafter, the first gas switch valve  982  would be turned on again, and the third gas switch valve  982  would be turned off. In this way, the burners  42  could generate flames by turns to heat different portions of the infrared ray generation assembly  54 , and thereby avoid the flames from applying on a single position, which would result in degradation and premature damage to the infrared ray generation assembly  54 . The control systems of the fourth and the fifth embodiments also could be utilized in the second and the third embodiments. 
     As mentioned above, with the structural design of the combustion device and the stove, the kiln of the present invention is conducive to increase of the heating efficiency and shorten a cooking time of the food ingredients. In addition, the combustion device and the thermal insulation structure of the present invention are not limited to kilns, and could be utilized in other heating apparatus. The aforementioned combustion devices are not limitations to the kilns of the first, the second, and the third embodiments. In particular, the kilns also could include firewood, fire rows disposed in the cavity, or an electrothermic heat source, and preferably the kilns could include a heat source which is capable of generating infrared ray. 
     It must be pointed out that the embodiments described above are only some embodiments of the present invention. All equivalent structures which employ the concepts disclosed in this specification and the appended claims should fall within the scope of the present invention.