Patent Publication Number: US-2022221146-A1

Title: Double-stacked gas burner

Description:
FIELD OF THE INVENTION 
     The present invention relates to gas burners for a cooktop appliance, and more particularly, to a top-breathing, double-stacked gas burner assembly with a main burner flame exiting an upper chamber and a simmer burner flame exiting a separate, lower chamber. 
     BACKGROUND OF THE INVENTION 
     Gas cooktop appliances often have one or more gas burners. The gas burners are designed to mix fuel gas with air and then ignite the mixture to generate a flame. Many gas burners are top-breathing, meaning that they draw air from above a cooktop surface of the appliance. However, the flames produced by these gas burners are susceptible to being extinguished, often referred to as “flame out,” due to changes in the environment (e.g., pressure waves). Such changes can cause the flame produced by the burner to detach or “lift off” the face of the burner and become extinguished. During flame out, combustible gas supplied to the burner continues to emanate from the burner, which can be undesirable. 
     Some conventional gas burners include retention flame burner ports that are configured to reignite the air-fuel mixture emanating from main burner ports during flame out. The retention flame burner ports in some gas burners also function as “simmer” burner ports when heating cookware at a low power rating. In these conventional gas burners, the main burner ports and the simmer ports are supplied from the same mixing chamber in the burner. Drawing from the same mixing chamber limits the volume of the air-fuel mixture that may be supplied to the simmer burner ports thereby causing the retention flames to be more likely extinguished when operating at low power settings. 
     Therefore, it is desirable to have a gas burner that can sustain retention flames at low power settings. 
     SUMMARY OF THE INVENTION 
     There is provided a gas burner assembly for a cooktop appliance. The gas burner assembly includes an upper chamber, a first plurality of burner ports communicating with the upper chamber, a lower chamber isolated from the upper chamber and a second plurality of burner ports communicating with the lower chamber. A first fuel-gas injector is configured to direct a first stream of fuel gas into a first opening that communicates with the upper chamber, thereby drawing surrounding air to be combined therewith in the first opening to yield injection of a first mixture of fuel gas and air into the upper chamber, to flow out the first plurality of burner ports. A second fuel-gas injector directs a second stream of fuel gas into a secondary opening that communicates with the lower chamber, thereby drawing surrounding air to be combined therewith in the secondary opening to yield injection of a second mixture of fuel gas and air into the lower chamber, to flow out the second plurality of burner ports. The upper chamber being isolated from the lower chamber so that the first mixture of fuel gas and air in the upper chamber does not mix with the second mixture of fuel gas and air in the lower chamber. 
     The is also provided a gas burner assembly for a cooktop appliance. The gas burner assembly includes a lower body having a pass-through opening and a secondary opening extend between an upper surface and a lower surface of the lower body. An intermediate body rests on the lower body and includes a first opening extending between the upper surface and the lower surface. The first opening of the intermediate body is aligned with the pass-through opening of the lower body. The lower surface of the intermediate body and the upper surface of the lower body at least partially defining a lower chamber of the gas burner assembly. The secondary opening of the lower body defines an inlet to the lower chamber. At least one of the lower body and the intermediate body define a simmer burner port fluidly communicating with the lower chamber. A cap is positioned on the intermediate body and includes a top planar wall and a peripheral side wall. The peripheral side wall includes a main burner port of the gas burner assembly. The top planar wall and the peripheral side wall of the cap and the upper surface of the intermediate body define an upper chamber of the gas burner assembly. The first opening of the intermediate body defines an inlet to the upper chamber. The main burner port fluidly communicates with the upper chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments are disclosed and described in detail herein with reference to the accompanying drawings which form a part hereof, and wherein: 
         FIG. 1  is a perspective view of a gas range having a plurality of gas burners disposed thereon; 
         FIG. 2  is a perspective view of an example double-stacked gas burner assembly as herein disclosed; 
         FIG. 3  is an exploded, perspective view of a gas burner assembly in relation to a cooktop panel of a gas range, having an intermediate body and a lower body according to a first embodiment; 
         FIG. 4  is a top perspective view of an orifice holder of the gas burner assembly of  FIG. 2 ; 
         FIG. 5  is a top perspective view of a lower body of the gas burner assembly of  FIG. 2 ; 
         FIG. 6 a    is a bottom perspective view of the lower body of  FIG. 5 ; 
         FIG. 6 b    is a closeup section view of a boss extending from a lower surface of the lower body of  FIG. 5  taken along line  6   b - 6   b  of  FIG. 6   a;    
         FIG. 7  is a side perspective view of an intermediate body of a gas burner assembly, according to the first embodiment; 
         FIG. 8  is a bottom perspective view of the intermediate body of  FIG. 7 ; 
         FIG. 9  is a top perspective view of a cap of the gas burner assembly of  FIG. 2 ; 
         FIG. 10  is an exploded, perspective view similar to  FIG. 3 , but illustrating only an intermediate body and a lower body according to a second embodiment; 
         FIG. 11  is a top perspective view of a lower body of a gas burner assembly according to the second embodiment; 
         FIG. 12 a    is a bottom perspective view of the lower body of  FIG. 11 ; 
         FIG. 12 b    is a closeup section view of a boss extending from a lower surface of the lower body of  FIG. 11  taken along line  12   b - 12   b  of  FIG. 12   a;    
         FIG. 13  is a side perspective view of an intermediate body of a gas burner assembly, according to the second embodiment; 
         FIG. 14  is a bottom perspective view of the intermediate body of  FIG. 13 ; 
         FIG. 15  is a side section view of the gas burner assembly of  FIG. 2  taken along line  15 - 15  of  FIG. 2 ; 
         FIG. 16  is an enlarged perspective view of a notch formed in a flange of the lower body of  FIG. 5 ; 
         FIG. 17  is a top perspective view illustrating the intermediate body resting on the lower body and the orifice holder of the gas burner assembly; 
         FIG. 18  is an enlarged perspective section view of the gas burner assembly of  FIG. 2  taken along line  18 - 18  of  FIG. 2 ; and 
         FIG. 19  is a schematic diagram illustrating a valve arrangement for the gas burner assembly of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now to the drawings,  FIG. 1  shows a gas cooktop appliance in the form of a domestic range, indicated generally at  50 . Although the detailed description that follows concerns a domestic range  50 , the burners described herein can be incorporated into gas cooktop ranges other than a domestic range  50 , as well as in stand-alone gas cooktops (or hobs) that are designed to be mounted in a countertop and not as part of a full range. In the illustrated embodiment, the range  50  includes a gas burner assembly  100 . Referring to  FIGS. 2 and 3 , the gas burner assembly  100 , in general, according to a first embodiment includes an orifice holder  110 , a lower body  200 , an intermediate body  300 , and a cap  400 . 
     Referring to  FIG. 4 , the orifice holder  110  includes a contoured bowl  114 , a first gas inlet port  160 , and a second gas inlet port  162 . The contoured bowl  114  is formed in an upper surface of the orifice holder  110 . A plurality of seats  116  are formed in a side wall of the contoured bowl  114 . Each seat  116  is positioned and dimensioned to accommodate therein and engage with a portion or protrusion of the lower body  200 , such as legs  206  as described in detail below. A first gas outlet port  140  extends through a central portion of the bowl  114  and is fluidly connected to the first gas inlet port  160  via a first internal passage  161  ( FIG. 15 ). The first gas outlet port  140  is dimensioned to receive a first gas nozzle  141 . 
     A recess  118  is formed in the side wall of the contoured bowl  114 . The recess  118  includes a bottom surface  118   a  and a second gas outlet port  142  formed in the bottom surface  118   a . The second gas outlet port  142  is fluidly connected to the second gas inlet port  162  via a second internal passage  163  ( FIG. 15 ). The second gas outlet port  142  is dimensioned to receive a second gas nozzle  143 . 
     Referring back to  FIG. 3 , a contoured opening  121  is formed in a cooktop panel  52  of the range  50 . The opening  121  is shaped and dimensioned to correspond to an upper opening or mouth of a contoured portion  122  ( FIG. 4 ) of the orifice holder  110 . The orifice holder  110  is positioned or suspended below the cooktop panel  52  such that the contoured portion  122  ( FIG. 4 ) is substantially aligned with and extends below the opening  121  in the cooktop panel  52 . It is contemplated that an upper perimeter rim or surface of the contoured portion  122  ( FIG. 4 ) may be flush with an upper surface of the cooktop panel  52 . 
     Referring back to  FIG. 4 , a plurality of countersunk mounting holes  124  are formed along a recessed ledge  123  of the orifice holder  110 . The mounting holes  124  are dimensioned and positioned to align with holes (not shown) in a substructure (not shown) of the range  50  ( FIG. 1 ), as described in detail below. It is also contemplated that the mounting holes  124  may be dimensioned and positioned to align with holes (not shown) in the cooktop panel  52  such that fasteners (not shown) may secure the orifice holder  110  to a bottom surface of the cooktop panel  52 . A tab  126  extends from one side of the orifice holder  112  and includes an opening  128  therein for receiving a spark ignitor  129 . The spark ignitor  129  is configured to generate a spark upon command to ignite an air-fuel mixture exiting the gas burner assembly  100 , as described in detail below. 
     Referring to  FIG. 5 , the lower body  200  (according to the first embodiment) includes an upper surface  202 , a lower surface  204  ( FIG. 6 a   ), and a pass-through opening  208  extending through a central portion of the lower body  200  between the upper surface  202  and the lower surface  204  ( FIG. 6 a   ). The upper surface  202  may include a raised annular portion  210  formed around the pass-through opening  208 . Notches  212  may be disposed about an outer periphery of the pass-through opening  208 . In the illustrated embodiment, there are three notches  212 . It is contemplated that the notches  212  may be different in shape, number, and location. Mounting holes  214  may extend through the lower body  200  between the upper surface  202  and the lower surface  204  ( FIG. 6 a   ). In the embodiment shown, the mounting holes  214  are formed in the raised annular portion  210  and there are four mounting holes  214 . It is contemplated that the mounting holes  214  could be different in number and location. 
     An upwardly extending flange  240  is disposed about an outer periphery of the upper surface  202 . The flange  240  defines a recessed area that is dimensioned to receive and accommodate the intermediate body  300 , as described in detail below. In the embodiment shown, the flange  240  includes a sloped outer wall  244  and a generally vertical inner wall  246 . A first notch  250  extends through the flange  240  and defines a generally rectangular-shaped passageway or opening  242  leading to an underside of the lower body  200 . The flange  240  also includes a second notch  260  that is positioned above a stability chamber  270 , and leading to an upper side of the lower body  200 . 
     Referring to  FIG. 6 a   , the stability chamber  270  is a generally box-shaped, recessed cavity extending from the lower surface  204  of the lower body  200 . The stability chamber  270  is defined by downwardly extending side walls  270   a  and a bottom wall  270   b . Downwardly extending side walls  258  are also formed around the opening  242  formed in the flange  240 . A bridge  254  extends over the opening  242  and includes a spark target  256  on a bottom surface of the bridge  254 . 
     A plurality of legs  206  extend from the lower surface  204  of the lower body  200 . The legs  206  are dimensioned and positioned to rest on or within the seats  116  ( FIG. 4 ) in the orifice holder  110  ( FIG. 4 ), as described in detail below. In the embodiment shown, there are three legs  206  each including a projecting portion  206   a . It is contemplated that more than three legs  206  may extend from the lower surface  204  and the legs  206  may have other shapes. 
     A boss  234  extends from the lower surface  204  of the lower body  200 , and a secondary opening  218  of the lower body  200  extends through the boss  234  to the upper surface  202 . In the embodiment shown, the secondary opening  218  is radially offset relative to the pass-through opening  208  of the lower body  200 . Referring to  FIG. 6 b   , the secondary opening  218  may be substantially frustoconical such that its interior diameter generally decreases from the lower end of the boss  234  to its upper end where the opening  218  opens to the upper surface  202  ( FIG. 5 ). Moreover, the secondary opening  218  also may include a chamfered wall portion  236   a  inclined radially inward from a lower end thereof up to its upper end adjacent to the upper surface  202  ( FIG. 5 ), resulting in the opening  218  appearing semi-circular 230 from above the upper surface  202  ( FIG. 5 ). The resulting secondary opening  218  is uniformly frustoconical at a lower portion  238  thereof, and substantially frustoconical at an upper portion  236  thereof wherein one wall segment thereof is chamfered so that it slopes radially inward as described above. 
     Referring to  FIG. 7 , the intermediate body  300  (according to the first embodiment) is a generally disc-shaped element having an upper surface  302  and a lower surface  304  ( FIG. 8 ). The upper surface  302  is frustoconically contoured to slope downwardly from a location adjacent a first opening  308  of the intermediate body  300 , toward a raised annular band  310  that extends about and adjacent a periphery of the intermediate body  300 . The raised annular band  310  is spaced inwardly from an outer circumferential edge  351  of the intermediate body  300  to define an annular ledge  312 . A slot  320  is formed in the annular band  310 . In the embodiment shown, a base portion of the slot  320  is formed in an upper portion of the annular ledge  312 . 
     Referring to  FIG. 8 , a boss  334  extends from the lower surface  304  of the intermediate body  300 , and the first opening  308  extends through the boss  334 . The first opening  308  has a diameter that increases from a first diameter at the upper surface  302  ( FIG. 7 ) of the intermediate body  300  to a second, larger diameter at a bottom or distal end of the boss  334 , such that the first opening  308  converges upward. The lower surface  304  may include a lower annular portion  324  surrounding the boss  334 . The lower annular portion  324  stands proud of the surrounding portion of the lower surface  304 . 
     A plurality of protrusions  338  are formed at a junction of the lower annular portion  324  and the boss  334 . In the illustrated embodiment, two of the protrusions  338  are shown, and one of the protrusions  338  is eclipsed by the boss  334 . It is contemplated that the protrusions  338  may be different in number and in location. The protrusions  338  are dimensioned and positioned to engage the notches  212  ( FIG. 5 ) formed around the pass-through opening  208  of the lower body  200 , as described in detail below. Bores  340  extend into the lower surface  304  and are configured to receive fasteners (not shown), as described in detail below. 
     A plurality of radial slots  354  are formed along a lower peripheral annulus  350  of the intermediate body  300 . Each slot  354  is defined by a pair of adjacent, rectangular-shaped cogs or standoffs  352  that extend radially and protrude downwardly from the lower peripheral annulus  350 . Alternatively, the slots  354  may be formed by machining grooves into the lower peripheral annulus  350 . In the illustrated embodiment, the slots  354  are square-shaped. It is contemplated that the slots  354  could have other shapes, for example, but not limited to, U-shaped, V-shaped, etc. In the embodiment shown, the slots  354  extend along straight radial lines. It is contemplated that the slots  354  may be skewed or curved. It is also contemplated that the slots  354  could be different in number and location. 
     Referring to  FIG. 9 , the cap  400  includes a top planar wall  401  and a downwardly extending peripheral side wall  402  having a sloped upper portion  402   a  and a vertical lower portion  402   b . A plurality of first gas burner ports  412  are disposed in the sloped upper portion  402   a . In the embodiment shown, the first gas burner ports  412  are illustrated as circular burner ports. It is contemplated that the first gas burner ports  412  could be defined by other shapes, for example, but not limited to, U-shaped openings, rectangular openings, or slanted slits, etc. 
     Referring to  FIGS. 10-14  a second embodiment will be described. The second embodiment is essentially the same as the first embodiment with the changes noted below. 
     Referring to  FIGS. 11, 12   a  and  12   b , the lower body  1200  shares some similarities with the lower body  200  of the first embodiment, and similar reference numbers (+1000) will be used for similar components. The lower body  1200  includes an upper surface  1202 , a lower surface  1204 , and a pass-through opening  1208  extending through a central portion of the lower body  1200  between the upper surface  1202  and the lower surface  1204 . A protrusion  1212  may extend into the pass-through opening  1208  from an outer periphery of the pass-through opening  1208 . In the illustrated embodiment, there is a single protrusion  1212 . It is contemplated that the protrusion  1212  may be different in shape, number, and location. 
     A boss  1234  extends from the lower surface  1204  of the lower body  1200 , and a secondary opening  1218  of the lower body  1200  extends through the boss  1234  to the upper surface  1202 . In the embodiment shown, the secondary opening  1218  is radially offset relative to the pass-through opening  1208  of the lower body  1200 . Referring to  FIG. 12 b   , the secondary opening  1218  may be substantially frustoconical such that its interior diameter generally decreases from the lower end of the boss  1234  to its upper end where the opening  1218  opens to the upper surface  1202 . A portion  1235  of the upper surface  1202  around the upper end of the opening  1218  is raised relative to the adjacent portion of the upper surface  1202  and has a conical-shape surrounding the opening  1218 . 
     Referring to  FIGS. 13 and 14 , the intermediate body  1300  according to the second embodiment is illustrated. The intermediate body  1300  shares similarities with the intermediate body  300  of the first embodiment, and similar reference numbers (+1000) will be used for similar components. 
     The intermediate body  1300  is a generally disc-shaped element having an upper surface  1302  and a lower surface  1304 . A raised annular band  1310  is spaced inwardly from an outer circumferential edge  1351  of the intermediate body  1300  to define an annular ledge  1312 . A first slot  1320  is formed in the annular band  1310 . In the embodiment shown, a base portion of the first slot  1320  is formed in an upper portion of the annular ledge  1312 . The first slot  1320  is positioned, as described in detail below. A second slot  1322  is also formed in the annular band  1310 . In the embodiment shown, a base portion of the second slot  1322  is formed in the upper portion of the annular ledge  1312 . The second slot  1322  is positioned, as described in detail below. 
     A plurality of protrusions  1323  are formed at a junction of the annular ledge  1312  and the annular band  1310 . In the illustrated embodiment, the protrusions  1323  are generally square-shaped and extend radially and protrude outwardly from an outer vertical wall  1311  of the annular band  1310 . It is contemplated that the protrusions  1323  could have other shapes, for example, but not limited to, round, V-shaped, etc. 
     Referring to  FIG. 14 , a boss  1334  extends from the lower surface  1304  of the intermediate body  1300 , and the first opening  1308  extends through the boss  1334 . A groove  1338  is formed into an outer surface of the boss  1334  and extends axially along the boss  1334 . It is contemplated that the groove  1338  may be machined into the boss  1334  via a slot or end milling process. The groove  1338  is positioned and dimensioned, as described in detail below. The lower surface  1304  may include an annular ledge  1324  surrounding the boss  1334 . The annular ledge  1324  stands proud of the surrounding portion of the lower surface  1304 . 
     Referring to  FIGS. 3 and 15 , the gas burner assembly  100  will now be described in relation to mounting the gas burner assembly  100  (according to the first embodiment) to the cooktop panel  52 . Assembly of the gas burner assembly  100  includes securing the orifice holder  110  to the substructure (not shown) of the range  50  ( FIG. 1 ) via fasteners (not shown) that extend through the mounting holes  124  of the orifice holder  110 . In this manner, a portion  53  of the cooktop panel  52  may be seated on the recessed ledge  123  of the orifice holder  110  for concealing the mounting holes  124  of the orifice holder  110 . In another embodiment, fasteners may extend through holes (not shown) in the cooktop panel  52  that are aligned with the mounting holes  124  of the orifice holder  110  for securing the orifice holder  110  to the cooktop panel  52 . A first fuel supply line (not shown) is connected to the first gas inlet port  160 , and a second fuel supply line (not shown) is connected to the second gas inlet port  162 , respectively. 
     The intermediate body  300  may be secured to the lower body  200  to create a subassembly or lower stack of the gas burner assembly  100 . The subassembly will be described herein with reference to the assembly of the intermediate body  300  of the first embodiment and the lower body  200  of the first embodiment. The assembly of intermediate body  1300  of the second embodiment and the lower body  1200  of the second embodiment is similar, except as noted below. The intermediate body  300  may be placed on the lower body  200  such that the boss  334  of the intermediate body  300  extends through the pass-through opening  208  of the lower body  200 . In this respect, the boss  334  and the pass-through opening  208  are dimensioned and positioned to axially align with each other along a central axis CA of the gas burner assembly  100 . 
     As the intermediate body  300  is placed on the lower body  200 , the protrusions  338  ( FIG. 8 ) of the intermediate body  300  are positioned and dimensioned to align with the notches  212  ( FIG. 5 ) in the lower body  200 . In particular, the protrusions  338  ( FIG. 8 ) and the notches  212  ( FIG. 5 ) are configured such that the rotational orientation of the intermediate body  300  is fixed relative to the lower body  200 . As shown in  FIG. 17 , the cooperation between the protrusions  338  and the notches  212  also serves to align the slot  320  in the intermediate body  300  with the spark ignitor  129  disposed in the tab  126  of the orifice holder  110 . 
     Referring back to  FIG. 15 , when the intermediate body  300  of the first embodiment is seated on the lower body  200 , the lower surface  304  of the intermediate body  300  rests against the upper surface  202  of the lower body  200  to define a lower chamber  500  of the gas burner assembly  100 . In particular, the raised annular portion  210  of the upper surface  202  is pressed against the lower annular portion  324  of the lower surface  304 , and the lower peripheral annulus  350  of the lower surface  304  rests against the upper surface  202 , respectively. 
     In the configuration illustrated, the slots  354  in the lower peripheral annulus  350  of the intermediate body  300  and the upper surface  202  of the lower body  200  define second gas burner ports  360  of the gas burner assembly  100 . It should be understood that in other embodiments, the slots  354  and the peripheral annulus  350  may be formed along the upper surface  202  of the lower body  200  for defining the second gas burner ports  360  when the intermediate body  300  rests on the lower body  200 . In this manner, it should also be appreciated that the standoffs  352  ( FIG. 8 ) of the intermediate body  300  may be formed on the upper surface  202  of the lower body  200 . In the embodiment shown, the secondary opening  218  of the lower body  200  defines an inlet to the lower chamber  500  of the gas burner assembly  100 . Fasteners (not shown) may extend through the mounting holes  214  ( FIG. 5 ) formed in the lower body  200  and into the corresponding bores  340  ( FIG. 8 ) formed in the lower surface  304  of the intermediate body  300 , respectively, for securing the intermediate body  300  to the lower body  200 . 
     The subassembly composed of the lower body  200  and the intermediate body  300  is positioned on the orifice holder  110 . In particular, the legs  206  extending from the lower surface  202  of the lower body  200  are dimensioned and positioned to align with and be received/seated in the seats  116  formed in the orifice holder  110 . When the lower body  200  is positioned on the orifice holder  110 , the legs  206  are dimensioned such that the lower surface  204  of the lower body  200  is spaced above the upper surface of the cooktop panel  52  to define a circumferential air inlet  392  therebetween. 
     As shown in  FIG. 17 , the lower body  200  is placed on the orifice holder  110  in a specific rotational orientation such that the slot  320  in the intermediate body  300  and the opening  242  in the flange  240  of the lower body  200  align with the spark ignitor  129  disposed in the tab  126  of the orifice holder  110 . In this respect, the opening  242  defined by the first notch  250  in the flange  240  is dimensioned to accommodate the spark ignitor  129  therein. In this orientation, and referring back to  FIG. 15 , the first gas nozzle  141  aligns with the first opening  308  in the intermediate body  300 , and the second gas nozzle  143  aligns with the secondary opening  218  in the lower body  200 , respectively. When assembled this way, the contoured bowl  114  of the orifice holder  110  defines a mixing volume or mixing chamber  390  of the gas burner assembly  100 . 
     The cap  400  is placed on the intermediate body  300  to define an upper chamber  600  of the gas burner assembly  100 . In particular, the upper chamber  600  is defined by the top planar wall  401  and the peripheral side wall  402  of the cap  400 , and the upper surface  302  of the intermediate body  300 . Together, the intermediate body  300  and the cap  400  also embody an upper stack of the gas burner assembly  100 . In this configuration, a distal end  403  of the peripheral side wall  402  is dimensioned to rest on the annular ledge  312  formed on the intermediate body  300 . Additionally, the first opening  308  in the intermediate body  300  defines an inlet to the upper chamber  600  of the gas burner assembly  100 . 
     As noted above, the assembly of the second embodiment is similar in most respects to the first embodiment, except for the differences noted below. 
     Referring to  FIG. 10 , in the second embodiment the intermediate body  1300  is placed on the lower body  1200  such that the groove  1338  ( FIG. 14 ) of the intermediate body  1300  aligns with the protrusion  1212  of the lower body  1200 . The groove  1338  ( FIG. 14 ) and the protrusion  1212  are configured such that the rotational orientation of the intermediate body  1300  is fixed relative to the lower body  1200 . As shown in  FIG. 10 , the cooperation between the groove  1338  ( FIG. 14 ) and the protrusion  1212  also serves to align the first slot  1320  in the intermediate body  1300  with the opening  1242  formed in the flange  1240  of the lower body  1200  and to align the second slot  1322  in the intermediate body  1300  with the second notch  1260  that is positioned above the stability chamber  1270 . 
     Referring to  FIG. 10 , when the intermediate body  1300  is seated on the lower body  1200 , the annular ledge  1324  ( FIG. 14 ) of the intermediate body  1300  rests against the upper surface  1202  of the lower body  1200 . In the second embodiment, the intermediate body  1300  and the lower body  1200  are illustrated as not including fasteners to secure the respective bodies  1200 ,  1300  together. 
     When the cap  400  ( FIG. 9 ) is placed on the intermediate body  1300  of the second embodiment, the plurality of protrusions  1323  on the intermediate body  1300  engage an inner surface of the peripheral side wall  402  ( FIG. 9 ) to center the cap  400  ( FIG. 9 ) on the intermediate body  1300 . In this respect, the plurality of protrusions  1323  may help reduce movement of the cap  400  ( FIG. 9 ) when it is fitted on the intermediate body  1300 . 
     Referring to  FIG. 15 , the gas burner assembly  100  will now be described with respect to operation of the same. In particular, the operation will be described relative to the gas burner assembly  100  including the orifice holder  110 , the lower body  200 , the intermediate body  300  and the cap  400 . The operation of the gas burner assembly  100  including the lower body  1200  and the intermediate body  1300  is similar to the operation of the gas burner assembly  100  with the lower body  200  and the intermediate body  300 , except where noted below. When fuel (e.g., a combustible gas such as natural gas) is supplied to the first gas inlet port  160 , it passes through the first internal passage  161  and enters the mixing chamber  390  via the first gas nozzle  141  along flow path A. Gas exiting the first gas nozzle  141  is ejected into the mixing chamber  390  toward the first opening  308  of the intermediate body  300 . As the gas flows from the mixing chamber  390  into a throat of the first opening  308  at the lower end of the boss  334 , combustion air is drawn into the mixing chamber  390  from a surrounding environment along flow path B via the circumferential air inlet  392 , and induced to flow together with the combustion gas via a Venturi effect into the first opening  308 . The air mixes with the fuel to form a first air-fuel mixture on entering the first opening  308 . The first air-fuel mixture is supplied to the upper chamber  600  via the inlet of the upper chamber  600  along flow path C through the first opening  308  in boss  334 . The first air-fuel mixture exits the upper chamber  600  along flow path D via the first gas burner ports  412  of the gas burner assembly  100 , whereupon it is combusted to yield main flames emanating from-the first burner ports  412 . 
     Referring to  FIG. 17 , a portion of the first-air fuel mixture in the upper chamber  600  ( FIG. 15 ) flows along flow path J through the slot  320  formed in the intermediate body  300 . This portion of the first air-fuel mixture is directed toward the spark ignitor  129  disposed in the tab  126  of the orifice holder  110 . Referring back to  FIG. 16 , the spark ignitor  129  (not shown in  FIG. 16  for clarity) ignites the first air-fuel mixture by directing a spark to the spark target  256  to form a main flame emanating from the first gas burner ports  412  and about the peripheral side wall  402  of the cap  400 . In this respect, the first gas burner ports  412  are also referred to as main burner ports of the gas burner assembly  100 . 
     Referring back to  FIG. 15 , fuel is supplied to the second gas inlet port  162 , and passes through the second internal passage  163  and enters the mixing chamber  390  via the second gas nozzle  143  along flow path E, toward a throat of the secondary opening  218  in lower body  200 , at a lower end of the boss  234 . Fuel exiting the second gas nozzle  143  is ejected into mixing chamber  390  toward the secondary opening  218 . Similarly as above for the first gas nozzle  141 , the fuel stream exiting the second gas nozzle  143  draws combustion air into the mixing chamber  390  along flow path B via the circumferential air inlet  392 , and into the throat of the secondary opening  218  via a Venturi effect where the fuel mixes with combustion air to form a second air-fuel mixture. The second air-fuel mixture is supplied to the lower chamber  500  via the inlet of the lower chamber  500  along flow path F, through the secondary opening  218  in the boss  234 -. The second air-fuel mixture exits the lower chamber  500  along flow path G via the second gas burner ports  360  of the gas burner assembly  100 . Referring to  FIG. 16 , a portion of the second air-fuel mixture exiting the second gas burner ports  360  flows through the opening  242  in the flange  240  along flow path H toward the spark target  256  disposed on the bottom surface of the bridge  254 . The spark ignitor  129  ( FIG. 17 ) ignites the second air-fuel mixture by directing a spark at the spark target  256  to form a “curtain or simmer flame” emanating from the second burner ports  360  of the gas burner assembly  100 . In this respect, the second gas burner ports  360  are also referred to as simmer burner ports of the gas burner assembly  100 . 
     Referring to  FIG. 17 , the curtain flame is formed substantially about an annular recess  280  located between the inner-wall  246  of the flange  240  of the lower body  200  and the circumferential edge  351  of the intermediate body  300 . Another portion of the second air-fuel mixture is directed along flow path I toward the stability chamber  270 . This portion of the second air-fuel mixture fills the stability chamber  270  and creates a separate stability flame (not shown), described in detail below. 
     Referring back to  FIG. 15 , in normal operation, the composition and pressure of the second air-fuel mixture will be equal in both the stability chamber  270  and the lower chamber  500 . Accordingly, the stability chamber  270  and the second gas burner ports  360  will be fed continuously to sustain their respective flames. However, because the gas burner assembly  100  is a top-breather that draws combustion air from the ambient environment, momentary or transient pressure waves resulting from activities in the room may impact the supply of combustion air to the circumferential air inlet  392  of the gas burner assembly  100 , especially at low turn-down. For example, opening or closing a door or activation of an HVAC system may generate instantaneous pressure waves sufficient to disrupt the flow of combustion air so as to extinguish flames. 
     The stability chamber  270  is at least partially isolated from the remaining lower chamber  500  such that the aforementioned pressure wave is impeded from impacting the composition and pressure of the second air-fuel mixture in the stability chamber  270 ), and therefore the instantaneous flow characteristics of the second air-fuel mixture resident in the stability chamber  270 . In addition, the stability chamber  270  stores a small excess of the combustion mixture (not shown), which may continue burning during transient pressure effects that otherwise will extinguish the flames ( FIG. 16 ) emanating from the first gas burner ports  412  and the second gas burner ports  360 . As a result, combustion of the second air-fuel mixture to produce the stability flame from the stability chamber  270  may be substantially unaffected by instantaneous, transient pressure waves that may otherwise ‘blow out’ the flames emanating from the second gas burner ports  360  and the first gas burner ports  412 . Thereafter, once the instantaneous, transient pressure waves have passed, the stability flame sustained in the stability chamber  270  may help reignite the first air-fuel mixture exiting the first gas burner ports  412  and the second air-fuel mixture exiting the second gas burner ports  360  resulting in substantially uninterrupted flame performance. 
     Referring to  FIG. 18 , during the reignition of the second gas burner ports  360 , the curtain flame emanating from the second gas burner ports  360  spans the peripheral side wall  402  of the cap  400  to reignite the first gas burner ports  412 . In this manner, the curtain flame serves as a retention flame that helps reignite the main flame during a “blow-out,” as explained above. More specifically, the curtain flame spans the peripheral side wall  402  and “carries” the flame from one gas burner port  412  to adjacent gas burner ports  412 . It is contemplated that the curtain flame may be continuous about the entire periphery of the cap  400  or the curtain flame may be segmented and exist only between adjacent first gas burner ports  412 . 
     Referring to  FIGS. 15 and 19 , a controller  700  may control a first valve  702  and a second valve  704  for supplying fuel from a source  706  to the first gas inlet port  160  and the second gas inlet port  162 , respectively. In particular, the supply of fuel to each of the gas inlet ports  160  and  162  may be selectively controlled by the first and the second valves  702  and  704 . For example, the controller  700  may regulate the first valve  702  and the second valve  704  so that fuel may be supplied only to the first gas inlet port  160 . In this mode of operation, gas is ejected only into the mixing chamber  390  via the first gas nozzle  141  located at the bottom of the bowl  114  in the orifice holder  110 . Combustion air is drawn into mixing chamber  390  via a Venturi effect based on gas exiting the first gas nozzle  141  toward and into the throat of the first opening  308  to form the first air-fuel mixture that is supplied to the inlet of the upper chamber  600 . 
     Similarly, when operating in a low power or simmer mode, the controller  700  may regulate the first valve  702  and the second valve  704  so that fuel is supplied only to the second gas inlet port  162 . In this mode of operation, gas is ejected only into the mixing chamber  390  via the second gas nozzle  143  located at the bottom of the bowl  114  in the orifice holder  110 . Combustion air is drawn into the mixing chamber  390  via a Venturi effect based on gas exiting the second gas nozzle  143  toward and into the throat of the secondary opening  218  to form the second air-fuel mixture that is supplied to the inlet of the lower chamber  500 . The independent supply of the second air-fuel mixture to the lower chamber  500  is particularly beneficial when operating the second gas burner ports  360  at a low turn-down ratio. It should be understood that the controller  700  may regulate the valves  702 ,  704  so that fuel is supplied to the first gas inlet port  160  and the second gas inlet port  162  simultaneously, such as, for example, when forming a main flame via the first gas burner ports  412  and a curtain or retention flame via the second gas burner ports  360 . 
     Because the controller  700  can selectively supply gas to the first gas inlet port  160  and the second gas inlet port  162 , it is contemplated that the intensity of the flames exiting the first gas burner ports  410  and the second gas burner ports  360  can be separately varied and/or independently operated, as described above. 
     As noted above, the operation of the second embodiment is similar to the operation of the first embodiment, except for the differences noted below. 
     Referring to  FIG. 10 , in the second embodiment wherein the gas burner assembly  100  includes the intermediate body  1300 , a portion of the first-air fuel mixture in the upper chamber  600  ( FIG. 15 ) flows along a flow path J2 through the second slot  1322  formed in the intermediate body  1300 . This portion of the first air-fuel mixture is directed toward the stability chamber  1270  of the lower body  1200 . As a result, combustion of the first air-fuel mixture to produce the stability flame from the stability chamber  1270  may be substantially unaffected by instantaneous, transient pressure waves that may otherwise ‘blow out’ the flames emanating from the second gas burner ports  360  and the first gas burner ports  412 . 
     Illustrative embodiments have been described hereinabove. It should be appreciated that features of the first embodiment may be combined with features of the second embodiment. Therefore, the inventive concept, in its broader aspects, is not limited to the specific details and representations shown and described. It will be apparent to those skilled in the art that the above apparatuses and methods may incorporate changes and modifications without departing from the scope of this disclosure. The invention is therefore not limited to particular details of the disclosed embodiments, but rather encompasses the spirit and the scope thereof as embodied in the appended claims.