Patent Publication Number: US-6661332-B1

Title: Press-type varistor switch

Description:
FIELD OF THE INVENTION 
     The present invention relates to switches, and particularly to a press-type varistor switch with adjustable impedance so that the switch can be operated in various operation modes. 
     BACKGROUND OF THE INVENTION 
     Conventionally, a switch is operated at two status, one being fully turning-on and the other being full turn-off. Referring to FIGS. 8 to  10 , the cross section views of some prior art switches are presented. These prior art switches are operated at two states, i.e., fully open and fully close. FIG. 9 and 10 shows the operation of one prior art switch. It is illustrated these kinds of switches are operated only at two modes. However recently, the electronic products are made more and more complex, and thus they need some operation modes other than full turning-on or turning off. That is, a switching state between full turning-on and turning-off is necessary, for example to press a switch continuously or to press a switch twice, or to press a switch for a predetermined time period so as to execute a desired operation, etc. However many prior art designs have complex structures and thus the costs are high. 
     Thereby, there is an eager demand for a novel switch which can improve above flaws in the prior art. 
     SUMMARY OF THE INVENTION 
     Accordingly, the primary object of the present invention is to provide a press-type varistor switch. A center of a upper cover is formed with a round hole. A head of a silicide cap is embedded into the round hole. Opposite sides of the seat are formed with a metal guide pin. The head of the silicide cap protrudes from a round hole of the upper cover so that the silicide cap is enclosed between the upper cover and the seat. Each to the adjacent sides of the metal guide pins is extended with a carbon-film resistor; the two carbon-film resistors are not in contact to one another. An interior of the head is installed with a conductive rubber. The conductive rubber is above the two carbon-film resistor. When a force is applied to the silicide cap, the two carbon-film resistors are in contact with the two metal guide pins partially or fully so that the impedance is adjustable. 
    
    
     The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a preferred embodiment of the present invention. 
     FIG. 2 is an assembled view of FIG.  1 . 
     FIG. 3 is a cross section view of FIG.  1 . 
     FIG. 4 is an exploded view of a second embodiment of the present invention. 
     FIG. 5 is an assembled view of FIG.  4 . 
     FIG. 6 is a cross section view about the device shown in FIG.  4 . 
     FIG. 7 is a schematic view showing the operation of the embodiment shown in FIG.  4 . 
     FIG. 8 is a cross section view of a prior art switch. 
     FIG. 9 is a cross section view of another prior art switch. 
     FIG. 10 is a schematic view showing the operation of the switch shown in FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, the press-type varistor switch of the present invention is illustrated. In the present invention, the switch  1  is formed by an upper cover  10 , a seat  20 , and a silicide cap  30  installed between the upper cover  10  and the seat  20 . A center of the upper cover  10  is formed with a round hole  11 . A head  31  of the silicide cap  30  is embedded into the round hole  11 . The corners of the bottom of the upper cover  10  are formed with a plurality of posts  12 . Each side of a pair of opposite sides of the bottom of the upper cover  10  is installed with a buckling block  13 . 
     The seat  20  is designed to have the configuration matching the upper cover  10 . The corners of the seat  20  are formed with combining holes  21 . The posts  12  of the upper cover  10  are inserted into the combining holes  21  of the seat  20 . Each side of a pair of opposite sides of the seat  20  is formed with a recess  22  for receiving the buckling block  13 . Each side of another set of opposite sides is formed with a metal guide pin  23 . Each to the adjacent sides of the metal guide pins  23  is extended with a carbon-film resistor  24 . The two carbon-film resistors  24  are not in contact to one another. 
     The silicide cap  30  has a trumpet shape. The head  31  of the silicide cap  30  protrudes from a round hole  11  of the upper cover  10  so that the silicide cap  30  is enclosed between the upper cover  10  and the seat  20  and thus is positioned therein. An interior of the head  31  is installed with a conductive rubber  33  with a round cross section view. When a force is applied to the silicide cap  30  to force the head  31  to the move downward, the conductive rubber  33  can be as an electric medium for communicating the two metal guide pins  23 . 
     Based on above said construction, in assembly, the silicide cap  30 , upper cover  10  and seat  20  are assembled sequentially. At first, the seat  20  of the silicide cap  30  is embedded into the round hole of the upper cover  10 . Furthermore, the posts  12  at the periphery of the upper cover  10  are embedded into the combining holes  21  corresponding to the seat  20  for being positioned therein. 
     Referring to FIG. 2, in realizing the present invention, as shown in FIG. 3, when no force is applied to the silicide cap  30 , the conductive rubber  33  is suspended in the inner surface of the head  31  and is not in contact with the seat  20 . At this time, the carbon-film resistors  24  between the two metal guide pins  23  at the surface of the seat  20  have higher impedance, i.e., they are not conductive. When an external force is applied to the silicide cap  30 , the head is pressed downwards so that a center of the round conductive rubber  33  will contact the two carbon-film resistors  24 . Then the current flowing through one metal guide pin  23  will flow through one carbon-film resistor  24  to the other carbon-film resistor  24  and then to the other metal guide pin  23  so that a lower impedance electric loop is formed. If the force applied to the silicide cap  30  is increased continuously, it will induce that the contact area between the conductive rubber  33  and the carbon-film resistor  24  is increased. Thereby, the current from one metal guide pin  23  to the other metal guide pin  23  through the two carbon-film resistors  24  and the conductive rubber  33  will increase so that the impedance of the loop is reduced. Finally, when the force applied is increased to a predetermined range, the cambered surface of the conductive rubber  33  will cover the two carbon-film resistors  24  completely and touch the two metal guide pins  23 . Then the current will flow from one metal guide pin  23  to another metal guide pin  23  through the conductive rubber  33  directly. This is the same as the conduction of a conventional push button. 
     Therefore, the present invention has the feature of complete conduction or turning-off as a conventional switch and has the function of variation of impedance with the external force. Functionally, the present invention is superior that the prior art switch. 
     Referring to FIGS. 4 to  7 , another embodiment about the press-type varistor switch of the present invention is illustrated. As shown in FIG. 4, a periphery of the round hole  11  at the center of the upper cover  10  is formed with an annular edge  101 . A press cover  102  is embedded in the round hole. Interior of the press cover  102  serves for being embedded by the head  31  of the silicide cap  30 . In the present invention, other structures, such as seat  20  and silicide cap  30  are the same as those describe above. Thereby, after assembly, as shown in FIGS. 5 and 6, when external force is applied to the press cover  102  continuously, the head  31  and conductive rubber  33  therewithin can be pressed at the same time so as to partially or wholly contact the two carbon-film resistors  24 , even to touch the two metal guide pins  23 . Thus, the impedance will be varied with the applied force, as shown in FIG.  7 . 
     Thereby, in the present invention, a conductive rubber  33  is installed at the inner surface of the silicide cap  30  and is suspended above two opposite but non-contact carbon-film resistors  24 . The rear ends of the two carbon-film resistors  24  are connected with respective metal guide pins so as to form a switch module. In operation, other than the full turning-on and full turning-off operations, the impedance between the two metal guide pins are varied with the force applied to the silicide cap. 
     The present invention is thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.