Patent Publication Number: US-6657147-B2

Title: Key switch

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a key switch to be mounted on a controller for a game machine or the like. 
     A related-art key switch of this type will be described with reference to FIG.  3 . In the drawing, a key switch  1  has, in a guide hole  3  which is formed in a case  2  of a controller for a game machine or the like, a key top  4 , a click rubber  5  which is formed in a lower part of the key top  4  integrally with the key top  4 , a movable contact  6  formed of an electrically conductive body which is provided on a lower face of a head  5   a  of the click rubber, and fixed contacts  8  which are provided on a circuit board  7  positioned below the movable contact  6 . 
     The click rubber  5  is formed in the shape of a bowl, and the moveable contact  6  is provided on an inner face of the head  5   a  of the click rubber  5  as described above in such a manner that the movable contact  6  can be contacted with and detached from the fixed contacts  8  by elastic force of the click rubber  5  that is adapted to be flexed and restored according to motions for striking the key top  4 . 
     Moreover, a circumferential edge of the click rubber  5  at its lower end is bent upwardly to form a recess  9  at a bent part. In the recess  9 , a guide wall  10  for defining the guide hole  3  holds the click rubber  5  at its lower end, thereby to fix the click rubber  5  inside the case  2 . 
     In the related-art, there is interposed a slight gap M between the guide wall for defining the guide hole that is formed in the case and the key top that is idly inserted inside the guide wall so as to move vertically. 
     Accordingly, fatty oils of a user&#39;s hand my adhere to the top when the key top is struck, and the fatty oils that have adhered to the key top often fall along a peripheral face of the key top through the gap M to adhere to the click rubber. On such occasions, there will occur in may cases such inconveniences that since the click rubber will be swollen with the fatty oils, the feeling of a click may be lost and a smooth function of key stroke cannot be performed. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a key switch for preventing fatty oils of a user&#39;s hand which have adhered to a key top from directly adhering to a click rubber, so that the function of the click rubber may be fully performed. 
     In order to achieve the above object, according to the present invention, there is provided a key switch, comprising: 
     a key top, including a body part having a first width and a flange formed on a lower end portion of the body part so as to have a second width which is larger than the first width; 
     a click rubber, provided on a bottom face of the body part of the key top, the click rubber being elastically deformable such that the key top is vertically moved between an upper first position and a lower second position; 
     a case, formed with a first chamber having a third width which is larger than the first width but smaller than the second width, for accommodating the body part of the key top therein, and a second chamber continued from the first chamber and having a fourth width which is larger than the second width, for accommodating the flange of the key top and the click rubber therein. 
     Consequently, the fatty oils of a user&#39;s hand that have adhered to the key top will be received by the flange even though the fatty oils fall down at the stroke of the key top, and the fatty oils will not reach the click rubber in the lower part. Therefore, such drawbacks in the prior art that the click rubber may be swollen with the fatty oils that have adhered to the click rubber resulting in a loss of the feeling of a click and a smooth switching motion cannot be performed. Hence, a malfunction occurring in the key stroke operation will be eliminated. Further, since not only the fatty oils but other foreign substances will not get in direct contact with the click rubber, quality of the key switch will also be improved. 
     Preferably, an upper face of the flange is abutted against a ceiling part of the second chamber when the key top is placed in the upper first position. 
     The above described preventive effect for fatty oils or foreign substances can be further enhanced. 
     Preferably, a recess is formed in a ceiling part of the second chamber. A protrusion is formed on an upper face of the flange. The protrusion is fitted into the recess when the key top is placed in the upper first position. 
     Since the fatty oils and the foreign substances are accommodated within a recess defined by an outer periphery of the body part and the protrusion, the above described preventive effect for fatty oils or foreign substances can be further enhanced. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein: 
     FIG. 1 is a front view in a vertical section of a key switch according to a first embodiment of the present invention; 
     FIG. 2 is a front view in a vertical section of a key switch according to a second embodiment of the present invention; and 
     FIG. 3 is a front view in a vertical section of a related-art key switch. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments according to the present invention will be described with reference to FIGS. 1 and 2. 
     A key switch  11  according to a first embodiment is shown in FIG.  1 . The key switch  11  has, in a large diametered guide hole  14  defined by a large diametered guide wall  13  which is provided in a case  12  of a controller for a game machine or the like, a key top  15 , a click rubber  16  which is arranged in a lower part of the key top  15 , a movable contact  17  formed of an electrically conductive body which is provided on a lower face of a head  16   a  of the click rubber  16 , and fixed contacts  19  which are provided on a circuit board  18  positioned below the movable contact  17 . 
     The click rubber  16  is formed in the shape of a bowl, and the moveable contact  17  is provided on an inner face of the head  16   a  of the click rubber  16  in such a manner that the movable contact  17  can be contacted with and detached from the fixed contacts  19  by elastic force of the click rubber  16  that is adapted to be flexed and restored according to motions for striking the key top  15 . 
     Moreover, a circumferential edge of the click rubber  16  at its lower end is bent in a U-shape to form a recess  20 . A lower end face of the large diametered guide wall  13  is abutted against the recess  20  and holds the click rubber  16 , thereby to fix the click rubber  16  inside the case  12 . 
     There is further provided, as shown in FIG. 1, a flange  21  outwardly projecting from a circumferential edge of a body part  15   a  of the key top  15  at a lower end thereof. The flange  21  is formed so as to move up and down along an inner peripheral face of the large diametered guide wall  13 . Still further, there is provided a small diametered guide wall  22  which is projected downward inside the large diametered guide wall  13  keeping a determined distance therefrom. The small diametered guide wall  22  is formed to have such a length that when the click rubber  16  has been returned to an upper position, the flange  21  can be abutted against a lower end face of the small diametered guide wall  22 . The body part  15   a  of the key top  15  is idly inserted into a small diametered guide hole  23 , which is defined by the small diametered guide wall  22 , so as to move vertically therein. 
     Incidentally, when the key top  15  is operated for key strokes, the fatty oils of the hand adhering to the surface of the body part  15   a  of the key top  15  will be received by the flange  21  and will not reach the click rubber  16  in the lower part, even though the fatty oils may fall down through a gap between the small diametered guide wall  22  and the body part  15   a  of the key top  15 . Thus, the likelyhood that there would occur an event such that the function of the click rubber  16  would be damaged by the fatty oils is greatly reduced. 
     Furthermore, even in case where the body part  15   a  of the key top  15  exposed out of the case  12  is formed to have a small size so as to vertically move inside the small diametered guide hole  23 , the flange  21  provided on the key top  15  is so constructed as to move up and down inside the large diametered guide hole. Therefore, a space for encasing the click rubber  16  can be formed to be sufficiently large, and accordingly, a head of the click rubber  16  as well as the click rubber  16  itself can be formed to have a sufficiently large size. As the results, because a smooth operation of striking the key top  15  can be performed, not only a stable switching motion can be conducted, but a favorable touch of click can be expected. Furthermore, because the flange  21  is so formed as to be abutted against a lower end face of the small diametered guide wall  22 , not only the above described fatty oils but other foreign substances will not directly reach the click rubber  16 , and accordingly, quality and durability of the key switch will be enhanced. 
     A key switch according to a second embodiment of the invention is shown in FIG.  2 . It is to be noted that same constituent elements as shown in FIG. 1 will be denoted with the same reference numerals, and their explanation will be omitted. 
     A difference between a structure as shown in FIG.  2  and the structure as shown in FIG. 1 is that there is provided a projected edge portion  24  in a ring-like shape extending upwardly from an outer circumferential edge of the flange  21  which is provided on the key top  15 , and that the projected edge portion  24  is idly inserted into a gap  25  between the large diametered guide wall  13  and the small diametered guide wall  22 . Accordingly, at a stroke of the key top  15 , the fatty oils of the user&#39;s hand which have adhered to the body part  15   a  of the key top  15  will be prevented from falling down by the presence of the flange  21 , and at the same time, not only the fatty oils but other foreign substances will be received in a recess  26  which is formed by the projected edge portion  24 , and will not directly reach or adhere to the click rubber  16 . Thus, the above described advantages can be further promoted. 
     Although the present invention has been shown and described with reference to specific preferred embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.