Abstract:
A keyboard comprises: a base board; and keyswitches each comprising a keytop, a support mechanism set on the base board and supporting the keytop for vertical movement, a biasing member disposed below the keytop to bias the keytop upward, and a switch element to be operated by depressing the keytop; wherein the keytop has a hard top part supported by the support mechanism, and a flexible skirt extending from the periphery of the hard top part.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a keyboard to be used as an input device for entering characters and the like and, more particularly, to a thin keyboard suitable for use in combination with a notebook computer.  
           [0003]    2. Description of the Related Art  
           [0004]    Referring to FIG. 5 showing one of keyswitches  30  of a conventional keyboard in a side elevation, the keyswitch  30  comprises, in combination, a keytop  31 , a pantograph type support mechanism  32  supporting the keytop  31 , a base board  37 , a pressing member  38  and a biasing member  39 . The upper ends of the links of the support mechanism  32  are connected pivotally to bearing parts  33   a  and  33   b  formed in four corners of the lower surface of the keytop  31 . The lower ends of the links of the support mechanism  32  are supported on bearing parts  34   a  and  34   b  formed on the base board  37 . The bearing parts  33   a  and  34   a  support the corresponding ends of the links of the support mechanism  32  pivotally. The bearing parts  33   b  and  34   b  support the corresponding ends of the links of the support mechanism  32  slidably.  
           [0005]    The pressing member  38  is formed on the lower surface of the keytop  31  opposite to the biasing member  39  disposed on the upper surface of the base board  37 . The biasing member is substantially cylindrical. When the keytop  31  is depressed, the biasing member  39  pushes up the keytop  31  to return the keytop  31  to its initial position. A membrane switch sheet, not shown, is placed on the upper surface of the base board  37 . When the keytop  31  is depressed, the biasing member  39  is deformed and the corresponding switch of the membrane switch sheet is closed. Thus, the keytop  31  of the keyswitch  30  disposed on the keyboard is depressed to give a signal represented by the keytop  31  to a computer.  
           [0006]    As known from FIG. 5, the conventional keyboard has a thickness equal to the sum of the thickness A of the keytop  31 , the stroke B of the keytop  31  and the thickness C of the base board  37 . The values of A, B and C are at least 3 mm, 3 mm and 1 mm, respectively. Therefore, the thickness A of the keytop  31  or the stroke B of the keytop  31  must be reduced to form the keyboard  30  in a further reduced thickness. However, the reduction of the thickness of the keyboard by reducing the thickness or the stroke of the keytop  31  entails the following problems. The reduction of the thickness A of the keytop  31  will reduce the bulkiness of the keytop  31  and may possibly spoil the appearance of the keytop  31 . The reduction of the stroke B of the keytop  31  will affect adversely to the operator&#39;s feeling of touch to the keytop  31 .  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide a keyboard formed in a small thickness without spoiling the appearance of its keytops and without deteriorating the feeling of touch to the keytops.  
           [0008]    According to one aspect of the present invention, a keyboard comprises a base board; and keyswitches each comprising a keytop, a support mechanism set on the base board and supporting the keytop for vertical movement, a biasing member disposed below the keytop to bias the keytop upward, and a switch element to be operated by depressing the keytop; wherein the keytop has a hard top part supported by the support mechanism, and a flexible skirt extending from the periphery of the hard top part.  
           [0009]    When the keytop is depressed by finger, the soft skirt comes into contact with the base board and is deformed as the keytop is further depressed, so that a sufficient stroke can be secured for the keytop. Accordingly, a gap between the keytop and the base board which must be formed to secure a sufficient stroke of the keytop in the conventional keyboard is scarcely necessary in the keyboard of the present invention. Thus, the distance between a plane including the upper surfaces of the keytops and the upper surface of the base board can be reduced and hence the keyboard can be formed in a reduced thickness.  
           [0010]    Preferably, the skirt of the keytop starts being deformed upon the depression of the keytop by a distance to close the switch element. Then, the skirt can be deformed simultaneously with the closing of the switch element. The skirt may be in contact with the base board or may be spaced a small distance apart from the base board in a state where any pressure is not applied to the keytop.  
           [0011]    Preferably, the hard part and the skirt are joined together. For example, the top part of the keytop maybe formed of a hard material, the skirt may be formed of a flexible material such as rubber, and the top part and the skirt may be bonded together with an adhesive or the like. The top part and the skirt may be of the same color to avoid spoiling the appearance of the keytop.  
           [0012]    The skirt may be formed of a flexible, soft material so as to cover the top part. The keytop may be formed entirely of a flexible, soft material, and hard bearing parts to be connected to a support mechanism may be attached to the lower surface of a top part of the keytop. The hard bearing parts may be bonded to the top part with an adhesive or the like. The top part of the keytop may be formed in a thickness smaller than that of the skirt. Recesses may be formed at positions for the hard bearing parts in the lower surface of the top part of the keytop to facilitate locating the hard bearing parts on the top part of the keytop.  
           [0013]    Thus, the keyboard of the present invention does not need the gap which must be formed in the conventional keyboard to secure the stroke of the keytop and hence the thickness of the keyboard can be reduced accordingly. Since the bulkiness of the keytop is not reduced, the appearance of the keytop is not spoiled. Since a sufficient stroke of the keytop can be secured, the feeling of touch to the keytop is not spoiled.  
           [0014]    The application of the keyboard of the present invention to a notebook computer is effective in forming the notebook computer in a reduced thickness.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings, in which:  
         [0016]    [0016]FIG. 1 is a perspective view of a computer;  
         [0017]    [0017]FIG. 2 is a side elevation of one of keyswitches included in a keyboard in a preferred embodiment according to the present invention in a nonactuated state;  
         [0018]    [0018]FIG. 3 is a side elevation of the keyswitch shown in FIG. 2 in an actuated state;  
         [0019]    [0019]FIG. 4 is a side elevation of one of keyswitches included in a keyboard in a second embodiment according to the present invention in a nonactuated state; and  
         [0020]    [0020]FIG. 5 is a side elevation of one of keyswitches included in a conventional keyboard.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Referring to FIG. 1, a keyboard  1  in a first embodiment according to the present invention is provided with an array of a plurality of keyswitches  10 . The keyboard  1  can be applied to a notebook computer.  
         [0022]    Referring to FIG. 2 showing one of the keyswitches  10  of the keyboard  1 , the keyswitch  10  comprises a keytop  2 , a support mechanism  14  set on a base board  15  to support the keytop  2  for vertical movement, and a biasing member  5  mounted on the base board  15 . The keytop  2  has a substantially flat hard top part  3 , and a skirt  4  extending from a peripheral part of the top part  3  toward the base board  15 . The hard top part  3  is formed of a hard resin, such as an ABS resin. The skirt  4  is formed of rubber or an elastic resin which permits the skirt  4  to be deformed when the keytop  2  is depressed by finger. The skirt  4  is formed so that a small gap is formed between the edge of the skirt  4  and the base board  15  when the keyswitch  10  is in an nonactuated state. The skirt  4  may be formed so that its edge is in contact with the base board  15  when the keyswitch  10  is in a nonactuated state.  
         [0023]    Bearing parts  7   a  and  7   b  are formed on the hard top part  3  in four corners of the lower surface of the hard top part  3 . In FIG. 2, only the bearing parts  7   a  and  7   b  on the side out of the sheet are shown. A hemispherical pressing member  6  is formed in a central region in the lower surface of the hard top part  3 . When the keytop  2  of the keyswitch  10  is depressed, the hemispherical pressing member  6  presses the biasing member  5 .  
         [0024]    The support mechanism  14  comprises a first lever  11  having the shape of a flat plate, and a second lever  12  having the shape of a flat plate joined at intermediate portions thereof by a pivot  9  in a scissors-like linkage. The first lever  11  and the second lever  12  are combined so that the first lever  11  extends inside the second lever  12 . Projections  11   a  of a circular cross section project laterally from the opposite sides of an upper end part of the first lever  11 , and the projections  11   a  are supported pivotally on the bearing parts  7   a.  Projections  12   b  of a circular cross section project laterally from the opposite sides of an upper end part of the second lever  12 , and the projections  12   b  are supported slidably on the bearing parts  7   b.  A circular opening, not shown, is formed in a central part of the first lever  11  to permit the biasing member  5  of a substantially cylindrical shape to extend therethrough.  
         [0025]    The base board  15  is a thin plate. Bearing parts  8   a  and  8   b  are formed on the upper surface of the base board  15  to support the lower ends of the first levers  11  and the second levers  12  thereon. Projections  11   b  of a circular cross section project laterally from the opposite sides of a lower end part of the first lever  11 , and projections  12   a  of a circular cross section project laterally from the opposite sides of a lower end part of the second lever  12 . The projections  11   b  are supported slidably on the bearing parts  8   b,  and the projections  12   a  are supported pivotally on the bearings  8   a.    
         [0026]    The substantially cylindrical biasing member  5  is disposed on the base board  15  opposite to the pressing member  6 . The biasing member  5  is compressed when the keytop  2  is depressed by finger. The keytop  2  is returned to its initial position by the force of the biasing member  5  when the keytop  2  is released.  
         [0027]    A switch element, not shown, is mounted on the base board  15  at a position corresponding to the biasing member  5 . The switch element is a membrane switch. An opening is formed in the base board to enable the biasing member  5  to come into contact with the switch element. When the keytop  2  is depressed to compress the biasing member  5 , the biasing member  5  closes the switch element, so that a signal representing a function assigned to the keyswitch  10  is given to the computer.  
         [0028]    Referring to FIG. 3, when he keytop  2  is depressed, the first lever  11  and the second lever  12  are turned on the pivot  9  so that the height of the support mechanism is reduced. The projections  11   a  of the first lever  11  turn on the bearing parts  7   a,  the projections  11   b  of the same slide horizontally in the bearing parts  8   b;  the projections  12   a  of the second lever  12  turn on the bearing parts  8   a  and the projections  12   b  of the same slide horizontally in the bearing parts  7   b.    
         [0029]    The skirt  4  is pressed against the base board  15  and an edge part of the skirt  4  is deformed so as to be bent outward as shown in FIG. 3 by the pressure exerted by finger on the keytop  2 . Consequently, the keytop  2  can be moved by a stroke corresponding to the stroke B of the keytop  31  of the conventional keyswitch  30  shown in FIG. 5 and the operator is able to feel the same touch to the keytop  2  as that felt by the operator when the operator operates the conventional keyswitch  30  when the operator operates the keyswitch  10 . Since the skirt  4  yields to the pressure exerted on the keytop  2  by finger to permit the keytop  2  to be depressed by the sufficient stroke, a gap between the skirt  4  of the keytop  2  and the base board  15 , which must be formed to secure a sufficient stroke of the keytop in the conventional keyboard, is scarcely necessary in the keyboard of the present invention. Since the keytop  2  can be moved by the sufficient stroke, the feeling of touch to the keytop  2  is satisfactory. The appearance of the keytop  2  is not spoiled because the thickness of the keytop  2  need not be reduced.  
         [0030]    [0030]FIG. 4 shows one of keyswitches  20  included in a keyboard in a second embodiment according to the present invention. The keyswitch  20  has a keytop  21  different from that of the keyswitch  10  included in the keyboard in the first embodiment, and the keyswitch  20  shown in FIG. 4 is the same in other respects as the keyswitch  10  shown in FIGS. 2 and 3. As shown in FIG. 4, the keyswitch  20  has a keytop  21  having a top part  22  and a skirt  24  formed integrally with the top part  22 . The keytop  21  is formed of a soft, flexible material. A rectangular hard member  23  is bonded to the lower surface of the top part  22  with an adhesive or the like. The hard member  23  is formed of a hard resin, such as an ABS resin. The hard member  23  is provided on its lower surface with bearing parts  23   a  for supporting projections  11   a  formed on an upper end part of a first lever  11 , and a bearing members  23   b  for supporting projections  12   b  formed on an upper end part of the second lever  12 .  
         [0031]    The keyboard is formed by arranging the keyswitches  20  on the base board  15 . When the keytop  21  is depressed, the skirt  24  comes into contact with the base board  15  and then the same is deformed as the keytop  21  is further depressed. An edge part of the skirt  24  is deformed so as to be bent outward as shown in FIG. 3. When the pressure applied to the keytop  21  is removed, the biasing member  5  pushes up the pressing member  6  to return the keytop  21  to its initial position.  
         [0032]    The notebook computer including the thin keyboard in accordance with the present invention can be formed in a small thickness. The keytop  21  may be formed of a material that enables the skirt  24  to be compressed so that its length is decreased when the keytop  21  is depressed.  
         [0033]    As apparent from the foregoing description, according to the present invention, any gap for the stroke of the keytop need not be secured between the skirt of the keytop and the base board, and the keyboard can be formed in a small thickness without spoiling the appearance of its keytops, with the sufficient stroke of the keytops secured and without deteriorating the feeling of touch to the keytops.  
         [0034]    Although the invention has been described in its preferred embodiments with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing from the scope and spirit thereof.