Patent Publication Number: US-11022317-B2

Title: Movable burner of gas cooktop and gas cooktop

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the priority of Chinese Patent Application, Serial No. 201821789602.X, filed Oct. 31, 2018, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to the technical field of cooktops, and in particular, to a movable burner of a gas cooktop and a gas cooktop. 
     A traditional gas cooktop typically includes a burner and a pot rack arranged around the burner. The pot rack is configured to support a pot and the burner is used as a heating source to heat foods in the pot. However, the structure design of the existing pot rack and burner is relatively single, and cannot match well with pots with changeable shapes. This affects use experience of users. As a result, a problem of a mismatch between the gas cooktop and the pot is caused, and there is a phenomenon that the pot cannot be placed on the gas cooktop stably, or that the pot is unevenly heated and has a poor heating effect, which affects use experience of users. 
     BRIEF SUMMARY OF THE INVENTION 
     A purpose of embodiments of the present invention is to provide an improved burner of a gas cooktop and a gas cooktop. 
     According to one aspect of the present invention, a movable burner of a gas cooktop includes a rotating shaft, a linear motion mechanism configured to perform a linear motion, a burner head having a plurality of brackets including a plurality of gas outlets for gas to flow out and form a flame, each of the brackets being separately hinged to the rotating shaft and separately connected to the linear motion mechanism such as to execute a rotation about the rotating shaft between at least two working positions, when driven by the linear motion mechanism, with the burner head having a flat upper surface in one of the two working positions, and with the burner head having a concave configuration in the other one of the two working positions, and a limit unit configured to limit a stroke range of the linear motion mechanism. 
     Compared with an existing fixed burner, the burner head of the burner in accordance with the present invention can switch between a plurality of working positions to meet supporting and heating requirements of pots with different shapes. Specifically, the linear motion mechanism drives the bracket to change an angle, so as to implement a switch of the burner head between different working positions. Therefore, advantages of simple solutions, low costs, low structure complexity, and easy manufacture are achieved. Further, each of the brackets remains in the corresponding working position due to the presence of the limit unit to provide a stable supporting structure, so as to avoid overturning of a pot supported on the bracket due to an unexpected displacement of the bracket during a use process. Further, the bracket remains in different working positions, so that the burner head can be made into different shapes to adapt to pots with different shapes and calibers. 
     According to another advantageous feature of the present invention, the linear motion mechanism can include a linear motor, a helical linear motion mechanism, or a linear motion mechanism with a connecting rod. In this way, the bracket may be effectively driven to rotate up and down about the rotating shaft along a vertical direction, so that the bracket can switch between different working positions with a shortest motion mileage. 
     According to another advantageous feature of the present invention, the linear motion mechanism can include a driving portion, a transmission shaft defining an axis and driveable by the driving portion for rotation about its own axis, the transmission shaft having first and second ends that are opposite to each other along a length direction, with the first end coupled with the driving portion, a transmission portion sleeved on the transmission shaft and executing an up and down motion in the length direction along the transmission shaft as the transmission shaft rotates, a fixing unit coupled to the transmission portion to limit a rotation of the transmission portion, when the transmission shaft is caused to rotate, and a plurality of supporting rods, each of the supporting rods having first and second ends that are opposite to each other along a length direction, with the first end being directly or indirectly hinged to the transmission portion, and with the second end of each of the supporting rods being hinged to a corresponding one of the brackets. In this way, a rotational motion of the transmission shaft is transformed into a linear motion of the transmission portion through the cooperation of the components, and the linear motion is transmitted to the bracket through the supporting rod. Further, overall structure complexity of the linear motion mechanism is low, the driving portion, the transmission shaft, the transmission portion, the fixing unit, and the supporting rod can be combined through a simple splicing method, and are easy to assemble, and a processing technology of the components is simple. 
     According to another advantageous feature of the present invention, the fixing unit can include a guiding pillar sleeved on a periphery of the transmission shaft and the transmission portion, with the guiding pillar provided with a groove along the length direction of the transmission shaft, and a pin portion having one end extending into a socket arranged in the transmission portion and capable of moving up and down in the groove while limiting the transmission portion from rotating when the transmission shaft is caused to rotate. In this way, a rotational motion of the transmission portion can be effectively transformed into a linear motion. Therefore, the structure is simple and easy to manufacture and assemble. 
     According to another advantageous feature of the present invention, the linear motion mechanism can include a slider sleeved on a periphery of the guiding pillar, with the slider being fixed with the transmission portion and caused to move up and down during the up and down motion of the transmission portion, wherein the first end of the supporting rods is hinged to the slider. In this way, a linear motion trend of the transmission portion can be transmitted to the supporting rod through the slider, and then an angle of the bracket can be adjusted. 
     According to another advantageous feature of the present invention, the slider can include a socket, with the pin portion passing through the socket of the slider and extending with the one end into the socket of the transmission portion to fix the slider with the transmission portion. In this way, a synchronous motion of the slider and the transmission portion can be implemented on the basis of making full use of the existing components, the number of overall components can be reduced, and assembly complexity can be reduced. 
     According to another advantageous feature of the present invention, the transmission portion can be configured as a trapezoidal nut, and the transmission shaft can have a trapezoidal thread coupled with the trapezoidal nut. In this way, a helical transmission effect can be achieved, so that a rotational motion of the transmission shaft can be transformed into a linear motion of the transmission portion. 
     According to another advantageous feature of the present invention, a housing can be arranged on a periphery of the linear motion mechanism, with the housing provided with a through hole for passage of the transmission shaft on one side near the driving portion. In this way, the linear motion mechanism can be protected by the housing, so that the linear motion mechanism can be prevented from being damaged by external force collision during a use process. 
     According to another advantageous feature of the present invention, a quantity of the supporting rods can be in accordance with a quantity of the brackets, with the second end of each of the supporting rods being hinged to a first hinge point of the corresponding one of the brackets, the linear motion mechanism being provided with a supporting portion on one end near the burner head, with the rotating shaft being fixed on the supporting portion and hinged to the brackets at a second hinge point of each of the brackets so that the linear motion of the linear motion mechanism causes a rotation of the first hinge point of each of the brackets about the second hinge point. In this way, with the linear motion of the linear motion mechanism, the angle of the bracket can be changed. Therefore, the bracket can switch between different working positions. Further, as the first hinge point of each of the brackets rotates about the second hinge point, one end of each of the brackets away from a burner head center can move in a direction away from or close to a panel of the gas cooktop. Therefore, a flat or a concave burner head is formed to stabilize and support pots with different shapes and calibers. 
     According to another advantageous feature of the present invention, the first hinge point can be located at a lower end of the corresponding one of the brackets, and the second hinge point can be located at one end of an upper surface of the corresponding one of the brackets near a center of the burner head. In this way, a length of the supporting rod can be reasonably shortened to reduce costs, and an effect that one end of the bracket away from the burner head center can rotate about another end close to the burner head center can be achieved. 
     According to another advantageous feature of the present invention, each bracket can have a protruded portion extending to the burner head center and provided with a through hole running through an upper surface and a lower surface of the protruded portion, the supporting portion being fixed with one end of the rotating shaft and extending into the through hole of the protruding portion to hinge the bracket to the rotating shaft. In this way, the supporting portion can pass through the bracket and be hinged to the inside of the bracket, so that the hinged position is not easily damaged by external forces This prolongs service life of the burner head. 
     According to another advantageous feature of the present invention, the limit unit can include micro switches respectively provided for the at least two working positions and configured to stop the linear motion of the linear motion mechanism, when being touched, so that the brackets remain in the corresponding one of the at least two working positions. In this way, the linear motion mechanism can automatically stop operation, so that after driven to move to a suitable working position, the bracket can automatically remain in the working position for users to use. 
     According to another aspect of the present invention, a gas cooktop includes a moveable burner as set forth above. In this way, the burner head of the gas cooktop can switch between a plurality of working positions, and can adapt to pots with different shapes and calibers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which: 
         FIG. 1  is a schematic diagram of a movable burner of a gas cooktop in a first working position according to an embodiment of the present invention; 
         FIG. 2  is a sectional view of the burner of  FIG. 1 , taken along the section line A-A in  FIG. 1 ; 
         FIG. 3  is an enlarged detailed view of the region B encircled in  FIG. 2  to show a linear motion mechanism of the burner in greater detail; 
         FIG. 4  is a schematic diagram of the burner shown in  FIG. 1  in a second working position; 
         FIG. 5  is an exploded view of the burner of  FIG. 1 ; 
         FIG. 6  is a sectional view of the burner, taken along a section line C-C in  FIG. 5 ; 
         FIG. 7  is a schematic diagram of a guiding pillar of the burner; 
         FIG. 8  is a sectional view of the guiding pillar in  FIG. 7 , taken along the section line D-D in  FIG. 7 ; 
         FIG. 9  is a top view of the guiding pillar in  FIG. 7 ; 
         FIG. 10  is a schematic diagram of a slider of the burner; 
         FIG. 11  is a top view of the slider; and 
         FIG. 12  is a top view of the burner of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION 
     Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments may be illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. 
     Turning now to the drawing, and in particular to  FIG. 1 , there is shown a schematic diagram of a movable burner according to the present invention, generally designated by reference numeral  100  and forming part of a gas cooktop. In this exemplary embodiment, the burner  100  includes a burner head  116 , which includes a plurality of brackets  110 . Each of the brackets  110  is provided with a plurality of gas outlets  111  for gas to flow out and form a flame, and is separately hinged to a rotating shaft  120 . The burner  100  further includes a linear motion mechanism  130 , which is shown in greater detail in  FIG. 3 , and a limit unit which is configured to limit a stroke range of the linear motion mechanism  130 . Each of the brackets  110  is separately connected to the linear motion mechanism  130 . When the linear motion mechanism  130  performs a linear motion, each of the brackets  110  can be driven by the linear motion mechanism  130  to rotate about the rotating shaft  120 , so that each of the brackets  110  has at least two working positions. 
       FIG. 1  and  FIG. 2 , which is a sectional view of the burner  100 , taken along the section line A-A in  FIG. 1 , depict the brackets  110  in a first working position, and  FIG. 4  shows the brackets  110  in a second working position in which the burner head  116  has a flat upper surface, i.e. each of the brackets  110  is in the second working position. When each of the brackets  110  is in the other first working position, the burner head  116  may be concave, as shown in  FIGS. 1 and 2 , i.e. each of the brackets  110  is in the first working position. 
     As a result, the burner head  116  can switch between a plurality of working positions to meet supporting and heating requirements of pots with different shapes. For example, when in the first working position shown in  FIG. 1 , the burner head  116  may be suitable for supporting a pot; and when in the second working position shown in  FIG. 4 , the burner head  116  may be suitable for supporting a pan. 
     Further, a linear motion direction of the linear motion mechanism  130  is indicated by a z direction in the drawings. Thus, the linear motion mechanism  130  can execute an up and down motion at an angle shown in the drawings, thereby driving each of the brackets  110  to switch between the first position shown in  FIG. 1  and the second position shown in  FIG. 4 . 
     Of course, in addition to the first working position and the second working position shown in  FIG. 1  and  FIG. 4 , each of the brackets  110  may further be placed in more than two working positions. A person skilled in the art can adjust an angle between the bracket  110  and a panel  210  of the gas cooktop as needed to better meet supporting requirements of pots with different shapes. The linear motion mechanism  130  can thus drive the bracket  110  to change the angle, so as to implement a switch of the burner head  116  between different working positions. Therefore, advantages of simple solutions, low costs, low structure complexity, and easy manufacture are achieved. 
     Each of the brackets  110  is held in the corresponding working position by the limit unit so as to provide a stable supporting structure and to avoid overturning of a pot supported on the bracket  110  due to an unexpected displacement of the bracket  110  during a use process. 
     Further, the brackets  110  can be held in different working positions, so that the burner head  116  can be made into different shapes to adapt to pots with different shapes and calibers. 
     The linear motion mechanism  130  may include a linear motor, a helical linear motion mechanism  130 , or a linear motion mechanism  130  with a connecting rod. In this way, the bracket  110  can be effectively driven to rotate up and down about the rotating shaft  120  in a vertical direction (i.e., the z direction), so that the bracket  110  can switch between different working positions with a shortest motion. 
     For example, the linear motion mechanism  130  with a connecting rod may be a structure with four connecting rods, so that an effect that the bracket  110  is driven by the linear motion to rotate about the rotating shaft  120  in the z direction can also be achieved. 
     Referring now to  FIGS. 5 and 6 , there are shown an example of the linear motion mechanism  130  embodied as the helical linear motion mechanism. For ease of illustration,  FIG. 5  omits depiction of the panel  210 . The linear motion mechanism  130  may include: a driving portion  131 ; a transmission shaft  132  having a first end  132   a  coupled with the driving portion  131  and a second end  132   b , with the first and second ends  132   a ,  132   b  being opposite to each other along a length direction. The transmission shaft  132  is driven by the driving portion  131  to rotate about its own axis r. A transmission portion  133  and a fixing unit  134  are mutually coupled, with the transmission portion  133  being sleeved on the transmission shaft  132 , and limited by the fixing unit  134 . The transmission portion  133  can perform an up and down motion along the transmission shaft  132  as the transmission shaft  132  rotates. The up and down motion refers hereby to a motion along the length direction of the transmission shaft  132  (i.e., a motion along the z direction). The linear motion mechanism  130  further includes a plurality of supporting rods  135 , with each of the supporting rods  135  having a first end  135   a  and a second end  135   b  that are opposite to each other along a length direction. The first end  135   a  of each of the supporting rods  135  can be directly or indirectly hinged to the transmission portion  133 , and the second end  135   b  of each of the supporting rods  135  is hinged to the corresponding bracket  110 . 
     In this way, a rotational motion of the transmission shaft  132  is transformed into a linear motion of the transmission portion  133  through the cooperation of the components, and the linear motion is transmitted to the bracket  110  through the supporting rod  135 . 
     Further, overall structure complexity of the linear motion mechanism  130  is low, the driving portion  131 , the transmission shaft  132 , the transmission portion  133 , the fixing unit  134 , and the supporting rod  135  can be combined through a simple splicing method, and are easy to assemble, and a processing technology of the components is simple. 
     In a non-restrictive embodiment, the driving portion  131  may be a rotary motor or another driving device capable of driving the transmission shaft  132  to rotate about its own axis r. 
     Further, the driving portion  131  may include a motor spindle  131   a , and the first end  132   a  of the transmission shaft  132  may be coupled with the motor spindle  131   a  through a shaft sleeve (not shown in the drawings). 
     In a non-restrictive embodiment, the transmission portion  133  may be a trapezoidal nut, and the transmission shaft  132  may have a trapezoidal thread coupled with the trapezoidal nut. In this way, a helical transmission effect can be achieved, so that a rotational motion of the transmission shaft  132  can be transformed into a linear motion of the transmission portion  133  with the cooperation of the fixing unit  134 . 
     Referring now to  FIGS. 7 and 8 , details of the fixing unit  134  will now be described. The fixing unit  134  includes a guiding pillar  151  which is sleeved on a periphery of the transmission shaft  132  and the transmission portion  133 . The guiding pillar  151  is provided with a groove  152  along the length direction of the transmission shaft  132  (i.e., the z direction). A pin portion  153  of the fixing unit  134  has one end which extends into a first socket  154  arranged in the transmission portion  133 , and the pin portion  153  is able to move up and down in the groove  152  to limit the transmission portion  133  from rotating with the rotation of the transmission shaft  132 . 
     In this way, a rotational motion of the transmission portion  133  can be effectively transformed into a linear motion. Therefore, the structure is simple and easy to manufacture and assemble. 
     When the transmission shaft  132  is driven by the driving portion  131  to rotate about its own axis r, the transmission portion  133  sleeved on the transmission shaft  132  is driven to rotate together. However, because the transmission portion  133  is coupled with the pin portion  153 , the rotational motion of the transmission portion  133  is blocked by the pin portion  153  and the groove  152  arranged on the guiding pillar  151  sleeved on the periphery of the transmission portion  133 , so that the transmission portion  133  cannot rotate with the transmission shaft  132 , but can only execute the linear motion in the z direction along the thread on the transmission shaft  132 . In this way, a helical transmission effect can be achieved through the cooperation between the pin portion  153  and the groove  152 . Therefore, space occupied by the entire linear motion mechanism  130  in the z direction can be effectively saved. 
     A length of the groove  152  along the length direction of the transmission shaft  132  can be determined based on a height difference between the bracket  110  in the first working position and the bracket  110  in the second working position, so as to ensure that the bracket  110  can be driven to the first working position or the second working position with the up and down motion of the transmission portion  133  (i.e., a motion along the z direction). 
     When the brackets  110  are able to assume more than two working positions, the length of the groove  152  along the length direction of the transmission shaft  132  may be determined by a height difference between a highest working position and a lowest working position that the bracket  110  assumes. 
     A width of the groove  152  may be coupled with a diameter of the pin portion  153  to ensure that the pin portion  153  can pass through the groove  152  and be coupled with the transmission portion  133 , so as to block the pin portion  153  from rotating about the r axis. In this way, by blocking the rotation of the pin portion  153  through the groove  152 , an effect of blocking the transmission portion  133  coupled with the pin portion  153  from rotating about the r axis can be achieved. 
     The width of the groove  152  may be slightly greater than the diameter of the pin portion  153  to avoid a problem of component damage caused by friction between the pin portion  153  and the groove  152  during the up and down motion of the transmission portion  133 . 
     As further shown in  FIG. 5 , the linear motion mechanism  130  can further include: a slider  136  which is shown in greater detail in  FIG. 10  and is sleeved on a periphery of the guiding pillar  151 . The slider  136  is fixed with the transmission portion  133  and performs the up and down motion with the transmission portion  133 . As shown in particular in  FIG. 3 , the first end  135   a  of each of the supporting rods  135  is hinged to the slider  136 . In this way, a linear motion of the transmission portion  133  can be transmitted to the supporting rod  135  via the slider  136  to thereby allow adjustment of an angle of the bracket  110 . 
     For example, referring to  FIG. 3  and  FIG. 11 , the slider  136  may be provided with a through hole  136   a  along the z direction. The transmission shaft  132 , the transmission portion  133  sleeved on the transmission shaft  132 , and the guiding pillar  151  sleeved on the periphery of the transmission shaft  132  and the transmission portion  133  pass through the through hole  136   a  to achieve an effect that the slider  136  is sleeved on a periphery of the guiding pillar  151 . 
     Meanwhile, a position of a first socket  155  arranged on the slider  136  corresponds to a position of the groove  152  arranged on the guiding pillar  151  and a socket  154  arranged on the transmission portion  133 , so that the pin portion  153  can pass through the socket  155  and the groove  152  and extend into the socket  154 , thereby effectively fixing the slider  136  and the transmission portion  133 , and limiting movement of the pin portion  153  to the groove  152 . 
     As the guiding pillar  151  is sleeved on the periphery of the transmission shaft  132  and the transmission portion  133 , the slider  136  may be coupled with a part of the transmission portion  133  exposed from the groove  152  so that the slider  136  can be fixed with the transmission portion  133  and move with the up and down motion of the transmission portion  133 . 
     Optionally, a further hinge point  136   b  may be arranged on the slider  136 , and the first end  135   a  of the supporting rod  135  may be hinged to the hinge point  136   b . A quantity of hinge points  136   b  may be in accordance with a quantity of the supporting rods  135 . 
     With reference to  FIGS. 3, 6 and 10 , the slider  136  may be provided with a second socket  155 , with one end of the pin portion  153  passing through the second socket  155  and extending into the socket  154  on the transmission portion  133  to fix the slider  136  with the transmission portion  133 . In this way, a synchronous motion of the slider  136  and the transmission portion  133  can be implemented on the basis of making full use of the existing components, a quantity of overall components can be reduced, and assembly complexity can be reduced. 
     For example, when the slider  136  has a cube structure, second sockets  155  may be arranged on four surfaces perpendicular to the z direction of the slider  136 . Correspondingly, the guiding pillar  151  is provided with grooves  152  in four corresponding directions respectively, and the transmission portion  133  is provided with sockets  154  in the four corresponding directions respectively. In this way, an effect can be respectively achieved on the four surfaces of the slider  136  that the slider  136  and the transmission portion  133  are fixed through the pin portion  153 , and perform the up and down motion together along the grooves  152 , so that overall strength of the linear motion mechanism  130  can be optimized to better block the transmission portion  133  from rotating with the rotation of the transmission shaft  132  and to ensure implementation of a spiral motion. 
     The slider  136 , the pin portion  153 , and the transmission portion  133  may be formed integrally. For example, two ends of the pin portion  153  are respectively formed with the slider  136  and the transmission portion  133  to improve firmness of the overall structure and prolong a service life of the components. 
     As further shown in  FIGS. 1 and 2  and  FIGS. 4 to 6 , the burner  100  of the gas cooktop may include a housing  160 , which is arranged on a periphery of the linear motion mechanism  130 . The housing  160  is provided with a through hole  161  for passage of the transmission shaft  132  on one side near the driving portion  131 . In this way, the linear motion mechanism  130  can be protected by the housing  130 , so that the linear motion mechanism  130  can be prevented from being damaged by external force collision during a use process. 
       FIG. 6  further shows the arrangement of a lining portion  162  around the through hole  161  to prevent the transmission shaft  132  driven by the driving portion  131  from swaying left and right during a rotation. The lining portion  162  may hereby wrap the transmission shaft  132  to prevent the transmission shaft  132  from swaying left and right while at the same time enhancing wear resistance and lubrication. 
     A quantity of the supporting rods  135  may be in accordance with a quantity of the brackets  110 , with the second end  135   b  of each of the supporting rods  135  being hinged to a hinge point  112  of the corresponding bracket  110 . As shown in particular in  FIGS. 5-9 , the linear motion mechanism  130  is provided with a supporting portion  170  on one end near the burner head  116 . The rotating shaft  120  is fixed on the supporting portion  170 , with a hinge point  113  of each of the brackets  110  being hinged to the rotating shaft  120 .  FIG. 9  is a top view of the guiding pillar  151  of the fixing unit  134  of the linear motion mechanism  130 , depicting the provision of four support portions  170  for the brackets  110 , respectively. When the linear motion mechanism  130  executes a linear motion, the hinge point  112  of each of the brackets  110  rotates about the hinge point  113  of the brackets  110 . In this way, with the linear motion of the linear motion mechanism  130 , the angle of the bracket  110  can be changed. Therefore, the bracket  110  can switch between different working positions. 
     Further, as the hinge point  112  of each of the brackets  110  rotates about the hinge point  113 , one end  110   a  of each of the brackets  110  away from a center  116   a  of the burner head  116 , as shown in  FIG. 2 , can move in a direction away from or close to panel  210  of the gas cooktop. Therefore, a flat or a concave burner head is formed to stabilize and support pots with different shapes and calibers. 
     The hinge point  112  of the brackets  110  may be located at a lower end of the bracket  110 , and the hinge point  113  of the brackets  110  may be located at one end  110   c  of an upper surface  110   b  of the bracket  110  near the burner head center  116   a . In this way, a length of the supporting rod  135  can be reasonably shortened to reduce costs, and an effect that one end  110   a  of the bracket  110  away from the burner head center  116   a  can rotate about another end  110   c  close to the burner head center  116   a  can be achieved. 
     As further shown in  FIGS. 5 and 6 , the bracket  110  can have a protruded portion  114  extending to the burner head center  116   a . The protruded portion  114  is provided with a through hole  115 , which is readily apparent from  FIG. 12  and runs through an upper surface  114   a  and a lower surface  114   b  of the protruded portion  114 . The supporting portion  170  is fixed with one end of the rotating shaft  120  and extends into the through hole  115  to hinge the bracket  110  to the rotating shaft  120 . In this way, the supporting portion  170  passes through the bracket  110  and is hinged to the inside of the bracket  110 , so that the hinged position is not easily damaged by external forces, and is conducive to prolonging a service life of the burner head  116 . 
     Optionally, the upper surface  114   a  of the protruded portion  114  may be level with the upper surface  110   b  of the bracket  110  to form a flat upper surface when the burner head  116  is in the second working position. 
     The limit unit may include micro switches at a quantity in accordance with a quantity of the working positions. When the linear motion mechanism  130  executes a linear motion until the micro switch is touched, the linear motion mechanism  130  stops performing the linear motion so that the bracket  110  remains in the corresponding working position. In this way, the linear motion mechanism  130  can automatically stop operation, so that after driven to move to a suitable working position, the bracket  110  can automatically remain in the working position for users to use. 
     Micro switches of the limit unit may be placed at the two ends of the groove  152  along a length direction of the two parallel grooves  152 , to ensure that the transmission shaft  132  is blocked from continuing to rotate when the slider  136  moves along the z direction to a top or a bottom of the groove  152 , so that the bracket  110  remains in the first working position or the second working position. 
     For example, the micro switch may be arranged in a position in the housing  160  coupled with the pin portion  153 . In this way, the micro switch is touched by the pin portion  153  and stops the driving portion  131  when the pin portion  153  moves with the slider  136 , i.e., the driving portion  131  stops driving the transmission shaft  132  to continue to rotate, so that the bracket  110  remains in the first working position or the second working position. 
     As an alternative, the motion of the linear motion mechanism  130  may also be restricted by the limit units through programs. 
     The driving portion  131  can be embodied as a rotary motor. Limit programs may be embedded in operating programs of the rotary motor. For example, a quantity of rotating cycles of the motor moving from the first working position to the second moving position is set. In actual operations, when the quantity of rotating cycles of the rotary motor reaches the set value, the rotary motor is controlled to automatically stop running. Therefore, the linear motion mechanism  130  is effectively restricted and unable to continue to execute the linear motion. As a result, the bracket  110  is securely held in the first working position or the second working position. 
     Another aspect of the present invention involves the provision of a gas cooktop, which is provided with a movable burner  100  as described above and shown in  FIGS. 1-12 . The burner head  116  of the gas cooktop can thus switch between a plurality of working positions, and can adapt to pots with different shapes and calibers. 
     The burner head  116  of the burner  100  may be located above the panel  210 , and the linear motion mechanism  130  of the burner  100  may be located below the panel  210  and thus invisible to users, thereby optimizing user experience. 
     Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.