Abstract:
A temperature switch includes a housing, a switching unit installed in the housing and including a resilient movable conductive plate that is movable between on and off positions, and a temperature control unit mounted on the housing and including a heat-conductive cover that is adapted to conduct heat of a heating element, a temperature-responsive element abutting against the cover, and a control rod and a fuse element disposed between the temperature-responsive element and the movable conductive plate to be moved by the temperature-responsive element so as to contact the movable conductive plate. The control rod has two opposite ends respectively extending towards the temperature-responsive element and the movable conductive plate. The fuse element is disposed at one of the ends. When the fuse element is melted, the control rod is disconnected from the temperature-responsive element either structurally or functionally.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a temperature switch, more particularly to a temperature switch that has a temperature-sensing capability for controlling supply of power.  
         [0003]     2. Description of the Related Art  
         [0004]     Referring to FIGS.  1  to  3 , a conventional temperature switch includes a porcelain housing  11 . The housing  11  has a bottom wall  111 , and a surrounding wall  113  that projects upwardly from an outer periphery of the bottom wall  111  and that cooperates with the same to define a receiving space  112 . The bottom wall  111  has a stepped portion  114 . The conventional temperature switch further includes opposite first and second conductors  12 ,  13  disposed below the bottom wall  111  and connected electrically and respectively to two electrical wires  22 ,  23 , a first conductive plate  14  disposed in the receiving space  112  and extending through the bottom wall  111  so as to connect electrically with the first conductor  12 , a second conductive plate  15  disposed in the receiving space  112  and extending through the stepped portion  114  so as to connect electrically with the second conductor  13 , a resilient movable conductive plate  16  disposed in the receiving space  112  and abutting against the first conductive plate  14 , a rod-support seat  17  mounted on the surrounding wall  113 , a porcelain control rod  18  extending slidably in a hole in the rod-support seat  17 , a temperature-responsive element  19  disposed in the rod-support seat  17  and abutting against the control rod  18 , and a metal cover  10  disposed on top of the rod-support seat  17  so as to cover the housing  11  and abutting against a heating element  21  of an electrical appliance (not shown). The movable conductive plate  16  has a contact part  161  located below the second conductive plate  15 , and a dome-shaped portion  162  disposed below and abutting against the control rod  18 . The second conductive plate  15  has a downwardly projecting contact part  151  for contacting the contact part  161  of the movable conductive plate  16 . The temperature-responsive element  19  has a curved portion  191  which deforms when reaching a preset deformation temperature. The preset deformation temperature is set as needed and may be either hot or cold. For example, the temperature switch installed in an electric iron requires a high deformation temperature, while the temperature switch installed in a drinking dispenser requires a low deformation temperature.  
         [0005]     When the temperature switch is in an “on” position, as shown in  FIG. 2 , the curved portion  191  of the temperature-responsive element  19  opens downwardly, and is in contact with the cover  10 . Furthermore, the control rod  18  is disposed between the curved portion  191  of the temperature-responsive element  19  and the dome-shaped portion  162  of the movable conductive plate  16 . Power is supplied through the electrical wire  22 , such that electrical current associated therewith passes through the first conductor  12 , the first conductive plate  14 , the movable conductive plate  16 , the second conductive plate  15 , the second conductor  13 , and into the electrical wire  23 .  
         [0006]     Assuming a high (hot) preset deformation temperature when heat of the heating element  21  is transmitted from the cover  10  to the temperature-responsive element  19 , and the preset deformation temperature is reached, the curved portion  191  of the temperature-responsive element  19  will deform from opening downwardly shown in  FIG. 2  to opening upwardly shown in  FIG. 3 . As a result, the curved portion  191  downwardly biases the control rod  18 , which in turn downwardly biases the movable conductive plate  16  so as to move the contact part  161  of the movable conductive plate  16  away from the contact part  151  of the second conductive plate  15 . As such, electrical current cannot flow from the first conductive plate  14  to the second conductive plate  15 , thereby placing the temperature switch at an “off” position.  
         [0007]     Although the aforementioned conventional temperature switch can achieve its intended purpose, when movable cooperation between components is not smooth, or when the curved portion  191  of the temperature-responsive element  19  fails to deform when the preset deformation temperature is reached, the “off” state of the temperature switch cannot be obtained. Furthermore, to enhance safe use of the electrical appliance, some manufacturers add a fuse to one of the electrical wires  22 ,  23 . However, this complicates assembly of the conventional temperature switch.  
       SUMMARY OF THE INVENTION  
       [0008]     Therefore, the object of the present invention is to provide a temperature switch that is capable of overcoming the aforementioned drawbacks of the prior art.  
         [0009]     According to this invention, a temperature switch comprises an insulation housing, a switching unit installed in the housing, and a temperature control unit mounted on the housing. The switching unit includes a resilient movable conductive plate that is movable between on and off positions. The temperature control unit includes a heat-conductive cover that is adapted to conduct heat of a heating element, a temperature-responsive element abutting against the heat-conductive cover, a control rod, and a fuse element. The control rod and the fuse element are disposed between the temperature-responsive element and the movable conductive plate to be moved by the temperature-responsive element so as to contact the movable conductive plate. The control rod has two opposite ends respectively extending towards the temperature-responsive element and the movable conductive plate. The fuse element is disposed at one of the ends. When the fuse element is melted, the control rod is disconnected from the temperature-responsive element either structurally or functionally. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments with reference to the accompanying drawings, of which:  
         [0011]      FIG. 1  is an exploded perspective view of a conventional temperature switch;  
         [0012]      FIG. 2  is a fragmentary sectional view of the conventional temperature switch in an assembled state, illustrating the conventional temperature switch in an “on” position;  
         [0013]      FIG. 3  is a view similar to  FIG. 2 , but with the conventional temperature switch in an “off” position;  
         [0014]      FIG. 4  is an exploded perspective view of the first preferred embodiment of a temperature switch according to the present invention;  
         [0015]      FIG. 5  is a fragmentary sectional view of the first preferred embodiment in an assembled state, illustrating the temperature switch of the present invention in an “on” position;  
         [0016]      FIG. 6  is a view similar to  FIG. 5 , but illustrating the temperature switch of the present invention in an “off” position;  
         [0017]      FIG. 7  is a view similar to  FIG. 5 , but illustrating a fuse element of the first preferred embodiment in a melted state;  
         [0018]      FIG. 8  is a view similar to  FIG. 5 , but illustrating the second preferred embodiment of a temperature switch according to the present invention; and  
         [0019]      FIG. 9  is a view similar to  FIG. 5 , but illustrating the third preferred embodiment of a temperature switch according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     Before the present invention is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure.  
         [0021]     Referring to FIGS.  4  to  7 , the first preferred embodiment of a temperature switch  20  according to the present invention is adapted to be installed in an electrical appliance, and is shown to comprise an insulation housing  3 , a switching unit  4 , and a temperature control unit  5 .  
         [0022]     The housing  3  is made of porcelain, and includes a bottom wall  31 , and a surrounding wall  33  projecting upwardly from an outer periphery of the bottom wall  31  and cooperating with the same to define a receiving space  32 . The bottom wall  31  has a stepped portion  311 .  
         [0023]     The switching unit  4  includes two opposite first and second conductors  41 ,  42  disposed below the bottom wall  31  and adapted to be connected electrically and respectively to electrical wires  22 ,  23 , a conductive connecting plate  43  disposed within the receiving space  32  and having a downward projection  431  that extends through the bottom wall  31  and that is fixed to the first conductor  41 , a fixed conductive plate  44  disposed on the stepped portion  311  and having a downward projection  442  that extends through the bottom wall  31  and that is fixed to the second conductor  42 , and a resilient movable conductive plate  45 . The fixed conductive plate  44  has an upwardly projecting contact part  441 . The movable conductive plate  45  has a curved portion  450  fixed to the bottom wall  31  and abutting against the conductive connecting plate  43 , and a resilient portion  451  disposed above the fixed conductive plate  44 . The resilient portion  451  has a downwardly projecting contact part  452  located above the contact part  441  of the fixed conductive plate  44 , and a dome-shaped part  453  between the curved portion  450  and the contact part  452 . In an “off” position of the temperature switch  20 , the contact part  452  of the resilient portion  451  is spaced apart from the contact part  441  of the fixed conductive plate  44 , and electrical current from the electrical wire  22  can only be transmitted to the conductive connecting plate  43  and the movable conductive plate  45  through the first conductor  41 . The electrical current cannot flow to the second conductor  42  through the fixed conductive plate  44  in this state.  
         [0024]     A plastic rod-support seat  51  is mounted on top of the surrounding wall  33  of the housing  3 , and has a bottom plate  511 , and an annular protrusion  513  projecting downwardly from the center of the bottom plate  511  and defining a passage hole  512 . The movable conductive plate  45  is located below the rod-support seat  51 .  
         [0025]     The temperature control unit  5  includes a control rod  52 , a temperature-responsive element  53 , a fuse element  54 , and a heat-conductive cover  55 . The control rod  52  is made of porcelain, and extends slidably in the passage hole  512 . In this embodiment, the dome-shaped part  453  of the resilient portion  451  of the movable conductive plate  45  is in contact with a bottom end of the control rod  52 .  
         [0026]     The fuse element  54 , in this embodiment, is configured as a tin ball, and is positioned in the passage hole  512 .  
         [0027]     The temperature-responsive element  53  is formed as a convex disc, and is disposed above the rod-support seat  51 . The convex disc has an outer periphery  532 , and a convex portion  531  in contact with the fuse element  54 . The fuse element  54 , in this embodiment, is disposed between a top end of the control rod  52  and the convex portion  531  of the temperature-responsive element  53 .  
         [0028]     The fuse element  54  has a melting temperature that can be set as needed. Generally, the melting temperature of the fuse element  54  is set between 180˜220° C. The temperature-responsive element  53  has a deformation temperature that can also be set as needed. For example, the deformation temperature can be set at 100° C., 140° C., 180° C., etc.  
         [0029]     The heat-conductive cover  55  is disposed above the rod-support seat  51 , and is connected to the housing  3  opposite to the bottom wall  31 . The cover  55  is adapted to abut against a heating element  21  of an electrical appliance (not shown) so as to conduct heat emanating from the heating element  21 . Normally, the outer periphery  532  of the temperature-responsive element  53  is placed in contact with a bottom surface of the cover  55 , and the convex portion  531  of the temperature-responsive element  53  extends away from the bottom surface of the cover  55 .  
         [0030]     When the temperature switch  20  is in an “on” position, as shown in  FIG. 5 , the resilient portion  451  of the movable conductive plate  45  is pressed downwardly through coordination of the control rod  52 , the temperature-responsive element  53 , and the fuse element  54 , so that the contact part  452  of the resilient portion  451  abuts against the contact part  441  of the fixed conductive plate  44 . At this time, electrical current supplied through the electrical wire  22  passes consecutively through the first conductor  41 , the conductive connecting plate  43 , the movable conductive plate  45 , the fixed conductive plate  44 , the second conductor  42 , and into the electrical wire  23 .  
         [0031]     In use, when heat from the heating element  21  is transmitted to the temperature-responsive element  53  through the heat-conductive cover  55 , and reaches the deformation temperature of the temperature-responsive element  53 , the convex portion  531  of the temperature-responsive element  53  deforms from a state shown in  FIG. 5  to another state shown in  FIG. 6 . At this time, the resilient portion  451  of the movable conductive plate  45  biases upwardly the control rod  52  and the fuse element  54 , resulting in movement of the contact part  452  of the resilient portion  451  away from the contact part  441  of the fixed conductive plate  44 . This prevents electrical current from flowing to the fixed conductive plate  44 , and places the temperature switch  20  in an “off” position, as shown in  FIG. 6 .  
         [0032]     When the temperature reaches another preset value, the convex portion  531  of the temperature-responsive element  53  deforms again from the state shown in  FIG. 6  to the state shown in  FIG. 5 , so that the temperature switch  20  is restored to its “on” position.  
         [0033]     It should be noted that the convex portion  531  of the temperature-responsive element  53  deforms when a preset temperature is reached. However, if the convex portion  531  did not deform as expected due to the abnormal operation of the temperature-responsive element  53 , the heat absorbed by the heat-conductive cover  55  will increase continuously until the heat transmitted to the fuse element  54  through the temperature-responsive element  53  reaches the melting point of the fuse element  54 , at which point the fuse element  54  will start to melt. Eventually, a gap is produced between the fuse element  54  and the convex portion  531  of the temperature-responsive element  53 , as shown in  FIG. 7 . This will permit the resilient portion  451  of the movable conductive plate  45  to bias upwardly the control rod  52  and move the contact part  452  of the resilient portion  451  away from the contact part  441  of the fixed conductive plate  44 , thereby putting the temperature switch  20  in the “off” position. Hence, when the temperature transmitted to the cover  55  is higher than the deformation temperature of the temperature-responsive element  53 , but the temperature-responsive element  53  is defective, through the melting of the fuse element  54 , the flow of current through the temperature switch  20  can still be prevented. The temperature switch  20  of the present invention, therefore, has a built-in safety function.  
         [0034]     Referring to  FIG. 8 , the second preferred embodiment of a temperature switch  20  according to the present invention is shown to be similar to the first preferred embodiment. However, in this embodiment, the fuse element  54  is disposed between the bottom end of the control rod  52  and the dome-shaped part  453  of the resilient portion  451  of the movable conductive plate  45 . When the temperature inside the receiving space  32  is higher than the melting temperature of the fuse element  54 , the fuse element  54  will melt, and a gap will be produced between the control rod  52  and the convex portion  531  of the temperature-responsive element  53 . This will permit the resilient portion  451  of the movable conductive plate  45  to bias upwardly, which in turn results in movement of the contact part  452  of the resilient portion  451  away from the contact part  441  of the fixed conductive plate  44 .  
         [0035]     Referring to  FIG. 9 , the third preferred embodiment of a temperature switch  20  according to the present invention is shown to be similar to the second preferred embodiment. However, in this embodiment, the fuse element  54  is configured as a stud or a rivet fixed to there silient portion  451  of the movable conductive plate  45 . Similarly, when the temperature inside the receiving space  32  is higher than the melting temperature of the fuse element  54 , the fuse element  54  will melt and permit there silient portion  451  of the movable conductive plate  45  to bias upwardly and away from the fixed conductive plate  44 .  
         [0036]     While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.