Abstract:
The present invention provides a keyboard switch structure that allows the height of a keyboard switch to be sufficiently minimized so as to be suitable for notebook personal computers or other portable devices. The present invention also provides a keyboard switch assembly that allows the keytop attached to the keyboard switch to be removed and replaced in a simple manner without destroying or damaging the keyboard switch. The keyboard switch is configured in a pantograph structure having cross arms that intersect each other to form an X-like structure. The upper portion of the pantograph structure is movably attached to a coupling plate on the underside of the keytop and the lower portion of the structure is movably attached to a base plate so as provide the keytop with movement in the vertical direction. The keyboard switch has two frame members that each have two cross arms that are parallel and fixed relative to each other. The first and second frame members intersect and engage each other so as to allow at least partial rotational movement about an intersection point lower than the center of each cross arm and in such a manner as to minimize the height of the keyboard switch.

Description:
BACKGROUND OF THE INVENTION 
     This application claims priority from Japanese Patent Application No. 2002-052214, filed Feb. 27, 2002. 
     FIELD OF THE INVENTION 
     The present invention relates to an apparatus and method of assembly for a personal computer keyboard switch. More particularly, the present invention pertains to a keyboard switch that can be used in thin notebook type personal computers. 
     DESCRIPTION OF THE PRIOR ART 
     With the advent of desktop computers, the keyboard switch has been widely used as a data input device, and because of technological advances in computer technology such use has significantly increased over the years. Advances in technology are responsible for the significant miniaturization of notebook computers and other portable data devices that has taken place over the last few years. The height of some notebook computers is less than two centimeters. To accommodate the reduction in height of notebook computers, the structure of the keyboard switch has also necessarily evolved. Developments in keyboard switch technology include the use of a film-membrane structure that contains a plurality of keyboard switches. The keyboard switches are configured in the form of thin structures called pantographs and are positioned on the film-membrane. 
     An example of such a keyboard switch is disclosed and described in Japanese Laid Open Patent Publication No. Hei 6/1994-36647. Publication No. Hei 6/1994-36647 discloses a pantograph type keyboard switch structure that has a first intersecting member which is formed by allowing an extending section to extend in one direction. The extending section extends from the upper side of a rotation support section with it as the center and two link members each of which have arms that extends parallel to the extending section in the other direction from the lower side thereof so as to intersect each other at an intersecting point at the upper side from the center of the mutual arms in a rotatable manner. A second intersecting member having the same structure as the first intersecting member is arranged and placed a certain distance from the first intersecting member, thereby forming a pantograph shaped member, the tip section of the link member positioned at the one side with the intersecting point of the intersecting members as a center is allowed to be supported by a shaft on a holder plate arranged on a flexible circuit board and at the underside of a keytop in a freely rotatable manner, and at the same time the tip section of the link member positioned at the opposite side is allowed to be supported with respect to the holder plate and the underside of a keytop in a freely rotatable manner and in a freely slidable and movable manner, in such a manner that when the key top is pressed down, a switching member may be actuated by an attaching rod of the pantograph shaped member and at the same time the extending sections of the folded pantograph shaped member may be kept in parallel. 
     In conventional keyboard switches, such as the example given above, a rod attached to the pantograph shaped keyboard switch makes contact with an elastic tactile rubber cap when the keytop is pressed, thereby actuating the keyboard switch. This configuration may not allow the height of the pantograph structure to be reduced sufficiently to accommodate the reduced height requirements present in notebook computers. In addition, in conventional keyboard switches the keytop is directly attached to the upper ends of the pantograph keyboard switch structure, thereby making the pantograph structure and keytop inseparable. As a result, when removal and/or replacement of a keytop are desired, the pantograph structure must also be removed and replaced or disassembled. 
     SUMMARY 
     In general the first aspect of the present invention features a keyboard switch that includes a pantograph structure. The pantograph structure has a first frame member and a second frame member. The first frame member has two cross arms fixed and parallel relative to each other and the second frame member has two cross arms fixed and parallel relative to each other. The first frame member and the second frame member engagedly intersect at an intersection point located below the center of the cross arms of each frame member forming an roughly X-like structure so as to allow free rotational movement of the first frame member and the second frame member about the intersection point to provide vertical movement for a keytop. 
     The keyboard switch also includes a coupling plate coupled to the underside of the keytop, a base plate, wherein the base plate is pivotally coupled to the lower ends of the cross arms of the first frame member by protrusions that extend from the cross arms so as to allow at least partial rotational movement. The base plate is also pivotally coupled to the lower ends the cross arms of said second frame member so as to allow at least partial sliding movement which may be in the direction roughly perpendicular to the direction of movement of the keytop. The upper ends of the first frame member and the second frame are moveably coupled to the coupling plate, wherein the coupling plate is also coupled to the underside of keytop so as to allow the keytop to be removed from or attached to the coupling plate. The switch further includes an elastic cap, wherein the elastic tactile cap is positioned between the coupling plate and the base plate. 
     An embodiment of the present invention may include the keyboard switch mentioned above, wherein the intersection point is one-third from the bottom of the cross arms of the first and second frame members. 
     Another embodiment of the present invention may include the keyboard switch mention above, wherein the first frame member has a first shaft receiving section that includes a shaft receiving groove and a shaft receiving plate having an arc section so that the shaft receiving plate is adjacent to the shaft receiving groove at the inner side of each cross arm. The second frame member may have a second receiving section that includes a shaft receiving groove and a shaft receiving plate having an arc section adjacent to each other at the outer side of each cross arm. The shaft receiving plate of second shaft receiving section engages into the shaft receiving groove of the first receiving shaft second and may allow free rotational movement and at the same time, the shaft receiving plate of first shaft receiving section engages into the shaft receiving groove of said second receiving shaft second an may also allow at least partial rotational movement. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded front view of a keyboard switch in accordance with a preferred embodiment of the present invention in a disassembled form. 
     FIG. 2 shows a coupling plate of the keyboard switch in accordance with a preferred embodiment of the present invention. 
     FIG. 3 shows a first frame member of the keyboard switch in accordance with a preferred embodiment of the present invention. 
     FIG. 4 shows a second frame member of the keyboard switch in accordance with a preferred embodiment of the present invention. 
     FIG. 5 shows a positional relationship between an elastic cap and a hinge frame and a film-like or flexible membrane circuit board in a preferred embodiment of the present invention. 
     FIG. 6 is a front view of a keyboard switch in accordance with a preferred embodiment of the present invention. 
     FIG. 7 is a cross sectional view showing the positional relation between the plastic cap and the membrane sheet in accordance with a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, we will describe a preferred embodiment of the present invention. FIG. 1 is an exploded side view of a keyboard switch configured in accordance with a preferred embodiment of the present invention. As shown in FIG. 1, keyboard switch  1  includes keytop  11  having coupling protrusions  13  and  14  that extend from the underside of keytop  11  so as to allow keytop  11  to be coupledd with coupling plate  21 . Coupling plate  21  may be made of a thin synthetic resin sheet. Keyboard switch  1  also includes a first frame member  31 , a second frame member, elastic cap  71 , hinge frame  81 , circuit board  91 , and base plate  94 . Circuit baord  91  may be made of a film-like member or some other suitable material. First frame member  21  includes protrusions  35  and  36  that extend perpendicularly from frame member  21 . Second frame member  51  includes protrusions  55  and  56  that extend perpendicularly from second frame member  51 . Hinge frame  81  includes a first cross arm receiving section  82  and a second cross arm receiving section, wherein the first receiving section may be a bearing hole and the second receiving section may be a slide groove  83 . Elastic cap  71 , which may be made of a synthetic material such as rubber or some other suitable material, includes moveable contact point  74  and lower edge section  75 . Typically, letters, numbers or other characters are inscribed or otherwise placed on topside  12  of keytop  11 . 
     Referring to FIG. 2, coupling plate  21  (shown in FIG. 1) includes flat plate section  22 . Flat plate section  22  makes contact with and presses upon elastic tactile cap  71  when keytop  11  is pressed. Step sections  23  and  24  are formed in the front and rear sections of flat plate section  22 . Flat plate  22  includes coupling holes  25  and  26  that allow coupling protrusions  13  and  14  that extend from the underside keytop  11  to pass through flat plate  22 . Coupling holes  25  and  26  are located in close proximity of step sections  23  and  24 , respectively. First frame member  31  and second frame member  51  are coupled to step sections  23  and  24 , respectively, of flat plate  22 . 
     Referring to FIG. 3, first frame member  31  may be made of a synthetic resin material or some other suitable material. First frame member  31  has two symmetric and parallel cross arms  32  and  33 . One end of cross arm  32  and one end of cross arm  33  is connected by connecting rod  34 . On the opposite ends of cross arms  32  and  33 , protrusions  35  and  36  extend outwardly from perpendicular to cross arms  32  and  33 , respectively. Shaft receiving plates  39  and  40  having arc sections  37  and  38 , respectively, may be positioned approximately two-thirds the total length of cross arms  32  and  33  when using connecting rod  34  as a reference point. Shaft receiving grooves  41  and  42  are located adjacent to shaft receiving plates  39  and  40 , respectively, along the inner side cross arms  32  and  33 . Shaft receiving plates  39  and  40  and corresponding shaft receiving grooves  41  and  42  form first shaft receiving sections  43  and  44 , respectively. Although cross arms  32  and  33  extend parallel to each other, they are positioned on different levels between the connecting rod  34  side and protrusions  35  and  36  sides with the first shaft receiving sections  39  and  40  as the center. 
     Referring to FIG. 4, second frame member  51  may be made of a synthetic resin material. Second frame member  51  has two symmetric and parallel cross arms  52  and  53 . Cross arms  52  and  53  are connected by a connecting rod  54 . Protrusions  55  and  56  extend outwardly from and perpendicular to cross arms  52  and  53 . At the other end of second frame member  51 , cross arms  52  and  53  are further connected by connecting rod  57 . Shaft receiving plates  60  and  61  having arc sections  58  and  59 , respectively, may be positioned approximately one-third the total length of cross arms  52  and  53  when using connecting rod  54  as a reference point. Shaft receiving grooves  62  and  63  are located adjacent to receiving shaft plates  60  and  61 , respectively, along the outer side of cross arms  52  and  53 . Shaft receiving plates  60  and  61  and corresponding shaft receiving grooves  62  and  63  form second receiving sections  64  and  65 , respectively. Although cross arms  52  and  53  extend parallel to each other, they are positioned on different levels between connecting rod  54  side and connecting rod  57  with the second shaft receiving sections  64  and  65  as the center. 
     Referring to FIG. 5, elastic tactile cap  71  is shaped like a hollow cup. Elastic tactile cap  71  includes pressing section  72  at the top of cap  71 , elastic section  73  that forms the cup portion of cap  71  and movable contact point  74 , shown in FIG. 1, is located inside cap  71 . As pressing section  72  is pressed down upon by keytop  11  elastic section  73  is likewise depressed down. Such pressing action produces a familiar clicking noise and accompanying sensation. FIG. 5, also shows circuit board  91 , which may be a flexible membrane or film-like type circuit board. Circuit board  91  is mounted on base plate  94  (shown in FIGS. 1 and 7) and includes at least two fixed contact points,  92  and  93 . Depressing pressing section  72  causes movable contact point  74  to make contact with fixed contact points  92  and  93  on circuit board  91 . Such contact results in electrical conductivity at fixed contact points  92  and  93 . 
     The following is a detailed description of assembly and operation of the keyboard switch in accordance with a preferred embodiment of the present invention. First, hinge frame  81  may be attached to circuit board  91  by pinching with an appropriate means where for example, a protrusion extending from base plate  94  under circuit board  91  is inserted into receiving slot on hinge frame  81  causing hinge frame  81  to be coupled to base plate  94 . Lower edge section  75  of elastic cap  71  is thinly coated with an adhesive, and then adhered onto fixed contact points  92  and  93  of circuit board  91 . Shaft receiving plates  60  and  61  of second shaft receiving sections  64  and  65 , respectively, are rotatably fitted into shaft receiving grooves  41  and  42  of first shaft receiving sections  43  and  44 , respectively, of the cross arms  32  and  33 . Concurrently shaft receiving plates  39  and  40  of first shaft receiving sections  43  and  44 , respectively, are also rotatably fitted into shaft receiving grooves  62  and  63  of second shaft receiving sections  64  and  65 , respectively of the cross arms  52  and  53 . As a result cross arms  32  and  33  and cross arms  52  and  53  are allowed to engagedly intersect each other in at least a partially rotatable manner, thereby forming a roughly X-shaped pantograph structure. 
     Next, protrusions  35  and  36  provided respectively at the lower ends of cross arms  32  and  33  are fitted into a bearing hole  82 , which may be provided on the surface of hinge frame  81  so that cross arms  32  and  33  may move in at least a partially rotatable manner. Similarly, protrusions  55  and  56  provided respectively at the lower ends of cross arms  52  and  53  are fitted into slide groove  83  provided on the surface of hinge frame  81  so that cross arms  52  and  53  may slide and move in at least a partially rotatable manner. During assembly, connecting rod  57  that connects cross arms  52  and  53  is positioned and mounted on step section  24  of coupling plate  21 . Similarly, connecting rod  34  that connects cross arms  32  and  33  is positioned and mounted on step section  23  of coupling plate  21 . Next, keytop  11  is placed on coupling plate  21  so that coupling protrusions  13  and  14  extending from the underside of keytop  11  are fitted through the coupling holes  25  and  26  of coupling plate  21  so as to attach keytop  11  to coupling plate  11 , thereby completing the method of keyboard switch assembly in accordance with the present invention. It should be understood that the steps of the method of keyboard switch assembly do not necessarily have to be performed in the order described above. 
     FIG. 6 is a cross sectional view of an assembled keyboard switch in accordance with a preferred embodiment of the present invention. As FIG. 6 illustrates, when the keyboard switch is fully assembled elastic rubber cap  71  is in a fully extended position so as to place the switch in an OFF state. When keytop  11  is pressed, while the keyboard switch in its normally OFF state, the pantograph structure, which includes cross arms  32 ,  33 ,  52 , and  53 , is likewise depressed or made to collapse. More specifically, when keytop  11  is pressed it causes coupling plate  21  attached to the underside of keytop  11  in turn to press down on elastic cap  71 . When elastic cap  71  is so depressed it produces a familiar clicking noise and/or accompanying sensation. Depressing elastic cap  71  causes movable contact point  74  located within elastic cap  71  to make contact with fixed contact points  92  and  93 . Contact between movable contact point  74  and fixed contact points  92  and  93  causes the keyboard switch to be set to the ON state. At this time, since cross arms  32 ,  33 ,  52  and  53  are structured on different levels, cross arms  32  overlaps the cross arm  52  and cross arm  33  overlap cross arm  53  completely in the vertical direction. When keytop  11  is no longer being depressed, keytop  11  is restored to its normal position by the restorative force produced in the rubber or other synthetic material of elastic cap  71 . 
     FIG. 7 illustrates another embodiment of the present invention. FIG. 7 shows elastic tactile cap  76  in its extended normal position that corresponds to the keyboard switch being set to the OFF state. In contrast to the embodiment described above where film-like circuit board  91  includes at least two fixed contact points,  92  and  93 . The embodiment described in FIG. 7 illustrates that film-like circuit board  91  may be substituted with three-ply circuit membrane  95 , wherein three-ply membrane  95  includes at least two contact points, movable contact point  96  and fixed contact point  97 . Elastic tactile cap  76  includes movable protrusion  77  inside its elastic section  73  and pressing section  72  is positioned at the top of cap  76 . When elastic tactile cap  76  is pressed in the downward direction movable protrusion  77  presses a synthetic resin plate which holds movable contact point  96 , thereby allowing movable contact point  96  to make contact with fixed contact point  97 . When movable contact point  96  and fixed contact point  97  makes contact, electrical conductivity results setting the keyboard switch to the ON state. Conversely, in the case where elastic tactile cap  76  is no longer depressed movable switch  96  is restored to a non-contact position by the restoring force of the synthetic resin plate that holds movable contact point  96 . When movable contact point  96  and fixed contact point  97  are in a non-contact position the keyboard switch is set to the OFF state. 
     As explained in detail above, the keyboard switch in accordance with one aspect of the present invention includes a first frame member having two parallel cross arms that are fixed relative to each other. A second frame member also has two parallel cross arms that are similarly fixed. Because the intersection point of first frame member and second frame member may be located at a point below the center of each of the cross arms, which allow the cross arms to be engaged with each other in a freely rotatable manner, it is possible to construct a pantograph structure having a reduced height that will make it suitable for use in notebook or other thinly dimensioned computers or portable data devices. 
     In accordance with another aspect of the present invention, because there is no rod suspended from the two frames that attach the cross arms of the pantograph structure as is found in conventional switches, the pantograph structure here may provide sufficient space to accommodate a conventional size elastic tactile rubber cap such as those used in conventional keyboard switches thereby providing the same tactile feel or sensation as is produced in conventional switches. 
     In accordance with another aspect of the present invention, keytop  11  is coupled to coupling plate  21  so as to allow keytop  11  to be attached to or removed from the keyboard switch in a manner that eliminates the need to remove or disassemble the underlying pantograph structure. 
     In the foregoing description, the apparatus and method of the present invention have been described with reference to specific examples. It is to be understood and expected that variations in the principles of the apparatus and method herein disclosed may be made by one skilled in the art and it is intended that such modifications, changes, and substitutions are to be included within the scope of the present invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.