Abstract:
An electrically conductive structure is provided with a hollow elastic member including an open bottom, a cavity, a pillar extending downward from a center of an inner surface into the cavity, a top platform, at least one hole open to the cavity, and a silver layer formed on a bottom of the pillar. Advantages such as elimination of short circuit and without heavy key depressing are obtained.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to electrically conductive structures and more particularly to an electrically conductive structure for each key of keyboard or keypad to improve characteristics such as eliminating short circuit and to avoid pushing the key too strongly. 
         [0003]    2. Description of Related Art 
         [0004]    A conventional electrically conductive structure for each key of keyboard or keypad is shown in  FIG. 7  and includes a hollow elastic member  11 , a pillar  12  structure in center of the elastic member  11 , and able to extend downward, a cavity  13  defined by the elastic member  11  and a circuit board (not numbered), a plurality of openings  14  located on a joining portion of the elastic member  11  and the circuit board, a carbon layer  15  formed on a bottom of the pillar  12 , and a membrane switch  20  on the circuit board directly under the carbon layer  15 . 
         [0005]    In response to press down the elastic member  11 , the pillar  12  moves downward to contact the membrane switch  20  for conduction and push air out of the cavity  13  via the openings  14 . 
         [0006]    However, the carbon layer  15  may be worn after many times of use. And in turn, it may increase electrical resistance, resulting in a poor contact. Thus, to push the key strongly when operating is required. Further, liquid may enter the cavity  13  to short circuit the membrane switch  20  via the openings  14 . 
         [0007]    Thus, the need for improvement still exists. 
       SUMMARY OF THE INVENTION 
       [0008]    It is therefore one object of the invention to provide a electrically conductive structure combining a hollow elastic member including an open bottom, a cavity, a pillar structure in center of the elastic member, and able to extend downward, a top platform, at least one hole open to the cavity, and a silver layer formed on a bottom of the pillar. 
         [0009]    The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1A  is a perspective view of an electrically conductive structure according to a first preferred embodiment of the invention; 
           [0011]      FIG. 1B  is a longitudinal sectional view of  FIG. 1A ; 
           [0012]      FIG. 2A  is a longitudinal sectional view of the electrically conductive structure of  FIG. 1A  mounted on one of keys of a keyboard or keypad; 
           [0013]      FIG. 2B  is a view similar to  FIG. 2A  showing a depressing of the electrically conductive structure; 
           [0014]      FIG. 3A  is a perspective view of an electrically conductive structure according to a second preferred embodiment of the invention; 
           [0015]      FIG. 3B  is a longitudinal sectional view of  FIG. 3A ; 
           [0016]      FIG. 4A  is a longitudinal sectional view of the electrically conductive structure of  FIG. 3A  mounted on one of keys of a keyboard or keypad; 
           [0017]      FIG. 4B  is a view similar to  FIG. 4A  showing a depressing of the electrically conductive structure; 
           [0018]      FIG. 5A  is a perspective view of an electrically conductive structure according to a third preferred embodiment of the invention; 
           [0019]      FIG. 5B  is a longitudinal sectional view of  FIG. 5A ; 
           [0020]      FIG. 6A  is a longitudinal sectional view of the electrically conductive structure of  FIG. 5A  mounted on one of keys of a keyboard or keypad; 
           [0021]      FIG. 6B  is a view similar to  FIG. 6A  showing a depressing of the electrically-conductive structure; and 
           [0022]      FIG. 7  is a longitudinal sectional view of a conventional electrically conductive structure of one of keys of a keyboard or keypad. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Referring to  FIGS. 1A to 2B , an electrically conductive structure in accordance with a first preferred embodiment of the invention comprises the following components as discussed in detail below. 
         [0024]    A hollow elastic member  30  is provided in one of a plurality of keys (not shown) of a keyboard or keypad. The elastic member  30  is formed of silicone rubber or plastic (i.e., being elastomeric). A pillar  32  structure in center of the elastic member  30 , and able to extend downward. The elastic member  30  has an open bottom  31 . A cavity  35  is defined by the elastic member  30  and a circuit board (not numbered). A fillister  34  is formed on a center of a top of the elastic member  30 . Four platform  33  are formed on a circular edge of the top of the elastic member  30  and are engaged with a bottom of a keycap (not shown) of the key. Four channels  38  each are formed between two adjacent platform  33 . An hole  301  is formed from bottom of the pillar  32  to the bottom of the fillister  34 . The hole  301  is closed in a non-pressed state of the elastic member  30  (i.e., the key being not pressed). A silver layer  36  is formed on a bottom of the pillar  32 . A membrane switch  40  is formed on the circuit board directly under the silver layer  36 . 
         [0025]    Alternatively, the silver layer  36  is replaced by an indium tin oxide (ITO). 
         [0026]    As shown in  FIG. 2B , in response to press down the elastic member  30 , the elastic member  30  is deformed flexibly and the pillar  32  moves downward to contact the membrane switch  40  for conduction and push air out of the cavity  35  exiting via the open hole  301 , the fillister  34 , and the channels  38  as indicated by dashed arrows. To the contrary, the hole  301  is closed when the depressing force exerted on the elastic member  30  is released. 
         [0027]    Referring to  FIGS. 3A to 4B , an electrically conductive structure in accordance with a second preferred embodiment of the invention is shown. The characteristics of the second preferred embodiment are substantially the same as that of the first preferred embodiment except the following: 
         [0028]    A larger hole  301  is formed from bottom of the pillar  32  to a position proximate to the bottom of the fillister  34 . A flap  37  is formed of silicone rubber or plastic (i.e., being elastomeric) and is adapted to interconnect the bottom of the fillister  34  and a top-end of the elastic member  301 . A central opening  371  is formed through the flap  37  but it is closed when the elastic member  30  is not depressed. 
         [0029]    Wherein the flap  37  is disposed on a top, bottom or middle of the hole  301 , the opening  371  is disposed in a center or edge of the flap  37 , and the flap  37  is formed of silicone rubber or plastic. 
         [0030]    As shown in  FIG. 4B , in response to press down the elastic member  30 , the elastic member  30  is deformed flexibly, the central opening  371  is open, and the pillar  32  moves downward to contact the membrane switch  40  for conduction and push air out of the cavity  35  exiting via the hole  301 , the central opening  371 , the fillister  34 , and the channels  38  as indicated by dashed arrows. To the contrary, both the central opening  371  and the flap  37  are closed when the depressing force exerted on the elastic member  30  is released. 
         [0031]    Referring to  FIGS. 5A to 6B , an electrically conductive structure in accordance with a third preferred embodiment of the invention is shown. The characteristics of the third preferred embodiment are substantially the same as that of the first preferred embodiment except the following: 
         [0032]    A platform  33  having a flat top is formed on the elastic member  30 . Two opposite holes  301  are formed on a periphery of the platform  33 . No opening is formed through the pillar  32 . 
         [0033]    As shown in  FIG. 6B ; in response to press down the elastic member  30 , the elastic member  30  is deformed flexibly and an opening  371  is formed between the pillar  32  and the flexibly deformed flap  37 . Thus, air in the cavity  35  exits via the openings  371  and the holes  301  as indicated by dashed arrows. To the contrary, the openings  371  are closed when the depressing force exerted on the elastic member  30  is released. 
         [0034]    There are two grooves  39  shaped as a cross formed on the platform  33  for preventing the platform  33  from contacting bottom of the keycap. 
         [0035]    It is envisaged by the invention that the following advantages are obtained: The silver or ITO layer formed on the bottom of the pillar  32  can increase times of contact between itself and the membrane switch without being worn. Thus, electrical resistance is not increased and good electrical contact is substantially maintained and these are great improvements over the prior art. The cavity inside the elastic member  30  is closed when the elastic member  30  is not been pushed, and the opening  371  is open only when the elastic member  30  is pushed. Thus, no liquid may enter the elastic member  30 . This can prevent short circuit and to avoid pushing the key too strongly is required. 
         [0036]    While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the appended claims.