Abstract:
A first bearing member is provided on one of an upper face of a board member and a lower face of a key top member. A first guide member is provided on the other one of the upper face of the board member and the lower face of the key top member. A first link member is disposed between the board member and the key top member, and has a first end portion rotatably supported by the first bearing member and a second end portion engaged with the first guide member. The first link member is pivotable in a first direction about the first end portion thereof to allow the key top member to move in a vertical direction. The second end portion of the first link member is slidable relative to the first guide member in a horizontal direction in accordance with the movement of the key top member.

Description:
BACKGROUND Of THE INVENTION  
       [0001]     The present invention relates to a key switch device and more particularly to a key switch device of a link type to be suitably used for a thin keyboard in a personal computer of a notebook type.  
         [0002]     For example, Japanese Patent Publication No. 2001-283675A discloses a key switch device of a link type as shown in  FIG. 6 . In the key switch device, a rubber spring  3  is attached to a portion between a board  1  and a key top  2 , and the key top  2  is formed to be movable upward and downward. Furthermore, a small link  4  and a large link  5  which are pivotable in directions orthogonal to each other are provided between the board  1  and the key top  2  so as not to mutually come in contact. The small link  4  is formed by a synthetic resin and the large link  5  is formed by a U-shaped wire.  
         [0003]     The small link  4  is slidably attached to a slide guide (not shown) having a lower end provided on an upper face of the board  1 , and furthermore, a pivot shaft portion  7  formed at an upper end of the small link  4  is pivotably supported on a pivot support  8  formed with a slit and provided on a back face of the key top  2 . In addition, an upper end and a lower end in the large link  5  are pivotably supported on pivot supports  9  and  10  formed on the upper face of the board  1  and the back face of the key top  2 , respectively.  
         [0004]     The key top  2  is held on the small link  4 , the large link  5  and the rubber spring  3  so that a stable stroke in a vertical direction can be secured.  
         [0005]     In a Z-link mechanism in the above key switch device, however, upper and lower ends of the large link  5  are pivotably coupled and held on the pivot supports  9  and  10 , so that the large link  5  carries out a pivoting motion around a pivot shaft portion thereof held on the pivot support  10  of the board  1 . When the key top  2  is pressed down, therefore, it is not moved right vertically but is moved in a slightly horizontal direction by a dimension D. Accordingly, it is necessary to carry out a design securing a key top space corresponding to the dimension D.  
         [0006]     Moreover, since a clearance is made between the large link  5  and the key top  2 , the clearance generates a looseness of the key top  2 .  
       SUMMARY OF THE INVENTION  
       [0007]     It is therefore an object of the invention to provide a key switch device in which a key top is smoothly moved just downward and the looseness of the key top is eliminated when the key top is pressed down.  
         [0008]     In order to achieve the above object, according to the invention, there is provided a key switch device, comprising:  
         [0009]     a board member;  
         [0010]     a key top member;  
         [0011]     a first bearing member, provided on one of an upper face of the board member and a lower face of the key top member;  
         [0012]     a first guide member, provided on the other one of the upper face of the board member and the lower face of the key top member; and  
         [0013]     a first link member, disposed between the board member and the key top member, and having a first end portion rotatably supported by the first bearing member and a second end portion engaged with the first guide member, wherein:  
         [0014]     the first link member is pivotable in a first direction about the first end portion thereof to allow the key top member to move in a vertical direction; and  
         [0015]     the second end portion of the first link member is slidable relative to the first guide member in a horizontal direction in accordance with the movement of the key top member.  
         [0016]     With this configuration, the key top member which is pressed down can be moved just downward. Therefore, it is possible to reduce a clearance between the adjacent key top members to each other, thereby increasing a key arrangement density. Consequently, it is possible to reduce the size of the whole keyboard. Alternatively, a size of each key top member in the keyboard having a predetermined size can be enlarged, thereby enhancing the operability of the keyboard.  
         [0017]     The first bearing member may be formed with a hole rotatably supporting the first end portion of the first link member and a slit communicating with the hole and adapted to be expanded when the first end portion of the first link member is press-fitted into the hole through the slit.  
         [0018]     With this configuration, it is possible to easily couple the first link member to the bearing member. Consequently, it is possible to enhance the assembling workability.  
         [0019]     The key top device may further comprise rib members, formed on the lower face of the key top member and clamping the first link member in the horizontal direction.  
         [0020]     With this configuration, it is possible to reliably prevent a looseness in the horizontal direction of the key top member, and to allow smoother operation for pushing the key top member with a sense of high grade.  
         [0021]     The key top device may further comprise;  
         [0022]     a second bearing member, provided on one of the upper face of the board member and the lower face of the key top member;  
         [0023]     a second guide member, provided on the other one of the upper face of the board member and the lower face of the key top member; and  
         [0024]     a second link member, disposed between the board member and the key top member, and having a third end portion rotatably supported by the second bearing member and a fourth end portion engaged with the second guide member.  
         [0025]     In this case, the second link member is pivotable in a second direction orthogonal to the first direction about the third end portion thereof. The fourth end portion of the second link member is slidable relative to the second guide member in the horizontal direction in accordance with the movement of the key top member. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]     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:  
         [0027]      FIG. 1A  is a schematic side view of a key switch device according to one embodiment of the invention;  
         [0028]      FIG. 1B  is a schematic perspective view of the key switch device;  
         [0029]      FIG. 2  is a schematic top plan view showing the inside of the key switch device;  
         [0030]      FIG. 3  is a side section view of the key switch device, viewed from the side of a large link;  
         [0031]      FIG. 4  is a side section view of the key switch device, viewed from the side of a small link;  
         [0032]      FIG. 5  is a side section view of a modified example of the key switch device, viewed from the side of a large link; and  
         [0033]      FIG. 6  is a side section view of a related-art key switch device, viewed from the side of a large link. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0034]     A key switch device according to the invention will be described below by taking a preferred example. The best mode of the invention has such a gist that one of ends of a large link is attached to a pivot shaft portion on a back face side of a key top or a slide guide portion on a board side, and furthermore, the other end of the large link is attached to the slide guide portion on the board side or the pivot shaft portion of the back face side of the key top, and a rib (a position regulating member) for suppressing a looseness in a transverse direction of the large link is integrally provided on both left and right sides of the back face of the key top with the large link interposed in the transverse direction.  
         [0035]     More specifically, in order to achieve such an object as to obtain a structure in which the key top is smoothly moved just downward and the looseness of the key top is eliminated, the invention is characterized in that an upper end or a lower end of the large link is slid in a horizontal direction while maintaining a parallel state with an upper face of the board and the key top can be thus moved just downward when the key top is pressed down. Moreover, the invention is characterized in that both left and right sides of the large link are interposed and pressed by the rib provided on the back face of the key top and a displacement movement in the transverse direction of the key top with respect to the large link is regulated.  
         [0036]     Embodiments of the invention will be described below in detail with reference to the accompanying drawings.  
         [0037]     As shown in  FIGS. 1A and 1B , a key switch device  11  according to one embodiment comprises a board  12  and a key top  13  provided above the board  12 . A small link  14  and a large link  15  are attached between the board  12  and the key top  13 . The small link  14  and the large link  15  are constituted to be pivotable in directions orthogonal to each other without any contact.  
         [0038]     Lower end portions of the small link  14  are so bent in a lateral direction X as to form slide shaft portions  14   a  and  14   b . The slide shaft portions  14   a  and  14   b  are slidably engaged with slide guides  12   a  and  12   b  provided on the board  12 , respectively. Upper end portions of the small link  14  are so bent in the lateral direction X as to form pivot shaft portions  14   c  and  14   d . The pivot shaft portions  14   c  and  14   d  are pivotably attached to pivot supports  13   a  and  13   b  provided on a back face of the key top  13 , respectively.  
         [0039]     The slide guides  12   a  and  12   b  guide the lower ends of the small link  14 , that is, the slide shaft portions  14   a  and  14   b  in a horizontal direction along the upper face of the board  12  when the key top  13  is moved upward and downward. Moreover, slits provided on the peripheral faces of the pivot supports  13   a  and  13   b  are temporarily expanded when the pivot shaft portions  14   c  and  14   d  of the small link  14  are strongly pressed against the slits from above, and permit the pivot shaft portions  14   c  and  14   d  to be engaged with the inner parts of the pivot supports  13   a  and  13   b . With this configuration, it is possible to easily couple the small link  14  to the pivot supports  13   a  and  13   b  in the board  12 .  
         [0040]     Lower ends of the large link  15  are so bent in a lateral direction Y as to form shaft portions  15   a  and  15   b . The pivot shaft portions  15   a  and  15   b  are pivotably attached to pivot supports  12   c  and  12   d  provided on the board  12 , respectively. Upper ends of the large link  15  are so bent in the lateral direction Y as to form slide shaft portions  15   c  and  15   d . The slide shaft portions  15   c  and  15   d  are slidably engaged with slide guides  13   c  and  13   d  provided on the back face of the key top  13 , respectively.  
         [0041]     The slide guides  13   c  and  13   d  guide the upper ends of the large link  15 , that is, the slide shaft portions  15   c  and  15   d  in a horizontal direction which is parallel with the upper face of the board  12  when the key top  13  is moved upward and downward. Moreover, slits provided on the peripheral faces of the pivot supports  12   c  and  12   d  are temporarily expanded when the pivot shaft portions  15   a  and  15   b  of the large link  15  are strongly pressed against the slits from above, and permit the pivot shaft portions  15   a  and  15   b  to be engaged with the inner parts of the pivot supports  12   c  and  12   d . With this structure, it is possible to easily couple the large link  15  to the pivot supports  12   c  and  12   d  in the board  12 .  
         [0042]     As shown in  FIG. 2 , an almost dome-shaped rubber spring  16  is provided in a central part of the key switch device  11  and is laid over the board  12 . Moreover, ribs  17  are provided integrally with the key top  13  so as to protrude inward from both inner peripheral side edges of the back face of the key top  13 . The ribs  17  always abut on both left and right sides of the large link  15  coupled to the key top  13  and maintain the large link  15  to be interposed in a transverse direction, and reliably suppress a looseness in the transverse direction of the key top  13  with respect to the large link  15 .  
         [0043]     In  FIGS. 3 and 4 , a solid line indicates a state before the key top  13  is pressed down. In this state, the rubber spring  16  urges the key top  13  upward so that the small link  14  and the large link  15  also rise at a predetermined angle with respect to the board  12 .  
         [0044]     When the operator presses down the key top  13  in this state, the key top  13  presses and deforms the rubber spring  16 , and furthermore, presses the upper end sides of the small link  14  and the large link  15  downward. At this time, the slide shaft portions  14   a  and  14   b  on the lower end side of the small link  14  are slid along the upper face of the board  12  in the slide guides  12   a  and  12   b  at the board  12  side. At the same time, the pivot shaft portions  14   c  and  14   d  on the upper end side of the small link  14  are rotated in the pivot supports  13   a  and  13   b  on the back face side of the key top  13 .  
         [0045]     On the other hand, the pivot shaft portions  15   a  and  15   b  on the lower end side of the large link  15  are rotated in the pivot supports  12   c  and  12   d  provided on the board  12 . At the same time, the pivot shaft portions  15   c  and  15   d  on the upper end side of the large link  15  are slid in a horizontal direction in parallel with the upper face of the board  12  in the slide guides  13   c  and  13   d  on the key top  13  side. In  FIGS. 3 and 4 , a dashed chain line indicates a state in which the key top  13  is pressed down.  
         [0046]     Accordingly, the key top  13  is pressed just downward while maintaining an almost parallel state with respect to the board  12  by the link function of the small link  14  and the large link  15 . The key top  13  is displaced downward to a predetermined position so that the rubber spring  16  presses a switch member  18  provided on the board  12  and is thus conducted electrically.  
         [0047]     When the key top  13  is further pressed down to a lowermost point, then, the lower face of the key top  13  abuts on the board  12  so that the operation for pressing the key top  13  down is stopped.  
         [0048]     Consequently, it is possible to reduce a clearance between the adjacent key tops to each other, thereby increasing an arrangement density of a large number of keys and reducing a size of the whole keyboard. On the other hand, in a case where a size for the key board is predetermined, it is possible to increase a size of each key top, thereby enhancing the operability of an operator. Furthermore, the movement in the lateral direction of the large link  15  is restricted by the ribs  17  provided on the key top  13 . Therefore, it is possible to easily obtain a key switch device in which the key top  13  has no looseness in the lateral direction with respect to the large link  15  and which has an excellent operation feeling and high grade.  
         [0049]     As a modified example of this embodiment, as shown in  FIG. 5 , pivot shaft portions  25   a  and  25   b  may be formed on upper ends of a large link  15 , and pivot supports  22   c  and  22   d  may be provided on the key top  13 . On the other hand, slide shaft portions  25   c  and  25   d  may be formed on lower ends of the large link  15  and slide guides  23   c  and  23   d  may be provided on the board  12 .  
         [0050]     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.