Abstract:
A switch structure comprises a control element, which comprises an alloy piece and a swing contact device. The alloy piece includes an actuating piece with a convex part, which has a upper side normally pushing the lower surface of the end part in the swing contact device so that the actuating piece ejects outwards and escapes from the end part when the alloy piece is overheated because of the current flowing through therein overloaded. Therefore, the end part falls down due to no support force and the head part of the swing contact device deforms upwards and does not press on the elastic contact piece. The elastic contact piece is released from the pressing of the swing contact device to eject upwards. Two joints connected in an electric loop are tripped. The object of rapid response, cutting power source, and safety is therefore achieved.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a switch structure, and more specifically, to a power switch with a simpler structure that is capable of switching off the power source when the current is overloaded. 
     BACKGROUND OF THE INVENTION 
     Power switches with only two states of ON and OFF functions controlled manually have been widely used in many appliances. However, it is risky to use the above power switches when the power source is unstable because overheating may occur due to overloading of the appliance and the wire easily catches fire. The users can not be aware of such latent danger since overloading and overheating are invisible. Therefore, such improved power switches have been greatly needed to overcome the danger. 
     Some improved power switch of the prior arts includes an alloy element composed of more than one metal to automatically shut off the power source when the alloy element is thermally deformed because of overheating. 
     For example, the power switch disclosed in in the prior art includes an alloy piece, a lever, and a cam actuator. The lever is actuated by the alloy piece, and the cam actuator is used to coordinate with a seesaw actuator. Thermal deformation of the alloy piece causes the lever to move, and then the cam actuator loses support, escapes and further cuts off the power source. Overheating may occur on he alloy piece. The above power switch uses the lever, the cam actuator, and the seesaw actuator to indirectly control the conductive plate, which is used to contact with the power source. The response of the power off operation in the above power switch when overheating occurs is so slow that the overloaded current may flow into the operating appliance in a short time to damage the appliance. Additionally, the conductive plate and the alloy piece need the wire to connect to each other, and the whole structure is complicated to cause the manufacturing difficult. The alloy piece has to actuate the seesaw actuator and the lever to escape. The function of automatic power off may incorrectly operate. 
     Furthermore, the power switch disclosed in U.S. Pat. No. 5,786,742 uses the thermal deformation of the alloy piece to push a limited position base such that a button can automatically escape and return back. The button is used to directly contact with the contact point of the power source so that the button may conduct the overloaded current when overheating occurs. The whole structure is still complicated. In summary, those improved power switches in the prior arts can partly overcome the danger of overheating for the appliance but the response is slow and the whole structure is complicated. An advanced power switch with simpler structure and a short response time is greatly desired. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a switch structure comprising a control element, which consists of an alloy piece and a swing contact device. The alloy piece includes an actuating piece with a convex part, which has a upper side normally pushing the lower surface of the end part in the swing contact device so that the actuating piece ejects outwards and escapes from the end part when the alloy piece is overheated because the current flowing through the alloy piece is overloaded. Therefore, the end part falls down due to no support force and the head part of the swing contact device deforms upwards and does not press on the elastic contact piece. The elastic contact piece is released from the pressing of the swing contact device to eject upwards. Two joints connected in an electric loop are tripped. The object of rapid response, cutting power source, and safety is therefore achieved. 
     Other features and advantages of the invention will become apparent from the following description of the invention that refers to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the exploded diagram of the switch structure according to the present invention; 
     FIG. 2 is a sectional view of the switch structure illustrating the ON state of the switch structure according to the present invention; 
     FIG. 3 is a sectional view illustrating the OFF state of the switch structure according to the present invention; 
     FIG. 4 is a sectional view illustrating the operation of the switch structure according to the present invention when the current is overloaded; 
     FIG. 5 is a sectional view of another embodiment illustrating the ON state of the switch structure according to the present invention; and 
     FIG. 6 is a sectional view of another embodiment illustrating the operation of the switch structure according to the present invention when the current is overloaded. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, the exploded diagram of the present invention shows that the switch structure comprises a switch cover body  10 , a contact reed  30 , a switch contact device  40 , a switch body  50 , an alloy piece  60 , and an elastic contact piece  70 . The switch cover body  10  is combined with a switch seat  20  and has a concave cambered surface  11 . Two axial holes  12  and two buckle holes  13  are formed on the two sides of the switch cover body  10 . Two fulcrums  21  and two tenons  22  on the switch seat  20  respectively correspond to the two axial holes  12  and two buckle holes  13  so as to joint with the switch cover body  10 . Accordingly, the switch cover body  10  may rotate around the fulcrums  21  clockwise or counterclockwise by external force applied. A resistor seat  23  included in the switch seat  20  comprises a chip resistor  24  to serve as a current limiting resistor for the neon lamp  14 , which is used to indicate the ON state of the switch. The resistor seat  23  has two through holes  25  on both sides. The switch seat  20  further includes a triangular piece  26 , which has a supporting rod hole  27 . 
     The contact reed  30  has one end inserting through the through holes  25  and connects to the chip resistor  24 . Another end forms a hook  31  hooking the third contact terminal  56  of the switch contact device  40  to electrically connect to one pin of the neon lamp  14  and eject the switch cover body  10  if desired. 
     The switch contact device  40  is wide at the head part  41  and becomes narrower towards the end part  42 . The head part  41  has an elliptical slot hole  411  and a through hole  412 . The slot hole  411  is used to connect the switch contact device  40  to the convex pillar  51  on the switch body  50 . A supporting rod  43  penetrates through the through hole  412  and the supporting rod hole  27  of the switch seat  20  so that the switch contact device  40  may act with the switch cover body  10 . Additionally, the head part  41  has a convex part  413  at the bottom. 
     The switch body  50  forms a hollow body with an opening  52  on the top, which is connected with the switch cover body  10 . The bottom of the switch body  50  forms a plurality of slots  53  to contact with the first contact terminal  54 , the second contact terminal  55 , and the third contact terminal  56 . 
     The alloy piece  60  has a shape of U. An actuating piece  61  with a convex part  62  at the bottom is formed at the central region of the alloy piece  60 . The actuating piece  61  and the alloy piece  60  forms an appropriate angle. 
     The elastic contact piece  70  has a round convex part  71  on the top, which comprises a contact hole  72  at the front end to joint with the upper contact terminal  73 . 
     The above elastic contact piece  70  is combined with one pin of the alloy piece  60  by the fixing base  63  and the rivet  64 . Another pin of the alloy piece  60  is fixed to he first contact terminal  54  so that the elastic contact piece  70  is located over the second contact terminal  55  and the third contact terminal  56 . 
     Furthermore, the second contact terminal  55  has a lower contact terminal  551  at the top to connect the elastic conductive device  15  to another pin of the neon lamp  14  so as to form a complete electrical loop. 
     The action of the switch according to the present invention includes OFF, ON, and trip when the current is overloaded. The detail will be described in the following. 
     With reference to FIG. 2, the OFF state of the present invention or the OFF state performed by the user is illustrated. When the user presses the switch cover body  10 , the contact reed  30  spreads and the switch cover body  10  rotates around the fulcrum  21  clockwise because the switch cover body  10  and the switch seat  20  are combined. Therefore, the supporting rod hole  27  also rotates around the fulcrum  21  clockwise as arc motion (left in this embodiment). The top end of the supporting rod  43  moves up left to pull up the head part  41  of the switch contact device  40  so that the elastic contact piece  70  ejects upwards without the pressing of the switch contact device  40 . The upper contact terminal  73  escapes from the lower contact terminal  551  to disconnect the first contact terminal  54  and the second contact terminal  55 , thereby cut off the power source. The neon lamp  14  thus turns off without power applied from the second contact terminal  55 . 
     As shown in FIG. 3, the ON state of the present invention is illustrated. When the user presses the left of the switch cover body  10 , the contact reed  30  is deformed and the switch cover body  10  rotates around the fulcrum  21  counterclockwise because the switch cover body  10  and the switch seat  20  are combined. Therefore, the supporting rod hole  27  also rotates around the fulcrum  21  counterclockwise as arc motion (right in this embodiment). The top end of the supporting rod  43  moves down left so that the head part  41  of the switch contact device  40  moves downwards. The bottom edge of the end part  42  in the switch contact device  40  pushes the top side of the convex part  62  of the actuating piece  61 . The convex part  413  rotates downwards around the end part  42  to push the round convex part  71 . The elastic contact piece  70  is thus pressed down so that the upper contact terminal  73  on the bottom side of the elastic contact piece  70  contacts the lower contact terminal  551  of the second contact terminal  55 . The external power source is supplied from the first contact terminal  54 , the alloy piece  60 , the elastic contact piece  70 , the upper contact terminal  73 , the lower contact terminal  551 , and the second contact terminal  55  to form a complete electrical loop. 
     Moreover, after the above electrical loop is connected, the power is conducted to one pin of the neon lamp  14  through the elastic conductive device  15 . Another pin of the neon lamp  14  is connected to the third contact terminal  56  through the chip resistor  24 , the contact reed  30  to form an electrical loop so as to turn on the neon lamp  14  to indicate that the switch is ON. 
     The switch contact device  40  swings upwards and downwards within the slot hole  411  with respect to the convex pillar  51 , as shown in FIGS. 2,  3 , and  4 . It should be noted that in the above OFF state and ON state, the bottom edge of the end part  42  of the switch contact device  40  pushes the top side of the convex part  62  of the actuating piece  61  without any motion. 
     With reference to FIG. 4, the schematic diagram illustrates the action for overloaded situation. When the current is overloaded, the alloy piece  60  thermally deforms due to the heat generated by the current and bend towards the switch contact device  40 . The actuating piece  61  ejects to the opposite direction and the end part  42  does not supported by the top side of the convex part  62  so as to fall down. The head part  41  of the switch contact device  40  moves upwards and the end part  42  downwards. The convex part  413  does not presses the round convex part  71  so that the elastic contact piece  70  can eject upwards to separate the upper contact terminal  73  and the lower contact terminal  551  to cut off the power source. 
     If the switch cover body  10 is not applied by any external force, the contact reed  30  spreads and the switch cover body  10  moves upwards so that the switch cover body  10  rotates around the fulcrum  21  clockwise towards the OFF position (as shown in FIG.  2 ). The end part  42  of the switch contact device  40  is pulled up as the supporting rod  43  moves upwards. The circuit is open-circuited. The alloy piece  60  and the actuating piece  61  gradually cool down to return to the original state, i.e., the actuating piece  61  resiles left and the end part  42  of the switch contact device  40  again inserts into the top side of the convex part  62  of the actuating piece  61  to prepare for the next switch operation. 
     Further referring to FIG. 5, another embodiment of the present invention provides another type of the switch contact device  40 ′. The switch contact device  40 ′ comprises the head part  41 ′ and the convex part  413 ′ at one end. Another end bends upwards to form an end part  42 ′. In the embodiment, the alloy piece  60 ′ approximately has a U shape and the end part  42 ′ pushes the top end of the alloy piece  60 ′. 
     As shown in FIG. 6, the schematic diagram illustrates the action for overloaded situation in this embodiment. When the current is overloaded, the alloy piece  60 ′ thermally deforms due to the heat generated by the current and bend towards the switch contact device  40 ′. The end part  42 ′ does not supported by the top side of the actuating piece  61 ′ so as to fall down. The head part  41 ′ of the switch contact device  40 ′ moves upwards and the end part  42 ′ downwards. The convex part  413 ′ does not presses the round convex part  71 ′ so that the elastic contact piece  70  can smoothly eject upwards to separate the upper contact terminal  73  and the lower contact terminal  551  to cut off the power source. 
     From the above description, the switch contact device  40 (or  40 ′) and the alloy piece  60 (or  60 ′) are used to rapidly respond to the status of overloaded current so that the elastic contact piece  70  ejects to cut off the power source. Then the switch can automatically recover to the open state under overloaded current. The response of the present invention is rapid and the structure is simple without any error operation. 
     Although only the preferred embodiments of this invention were shown and described in the above description, it is requested that any modification or combination that comes within the spirit of this invention be protected.