Patent Publication Number: US-6909062-B2

Title: Key-switch device corresponding to miniaturized notebook-size personal computer with reduced-thickness

Description:
This application is a continuation of application Ser. No. 10/122,023, filed on Apr. 4, 2002 and now U.S. Pat. No. 6,777,634. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a key-switch device for use as various input devices of personal computers and word processors, etc., and in particular it relates to a key-switch device corresponding to miniaturization and reduction in thickness of notebook-size personal computers. 
   2. Description of the Related Art 
   Along with demands for reduction in size and miniaturization of the entire device, various key-switch devices have been proposed, in which a key-top is attached at the upper end of a pair of lever members crosswise linked together so as to change the angle between the pair of lever members link-crossing each other by moving the key-top up-and-down. 
   The type of conventional key-switch device will be described below with reference to  FIGS. 26  to  29 . 
   As shown in  FIG. 26 , the conventional key-switch device principally comprises a key-top  101 , a holder member  130  disposed beneath the key-top  101 , a guide-supporting member  106  for guiding and supporting the key-top  101  between an elevated position separated from the holder member  130  and a lowered position coming close to the holder member  130 , and a rubber spring  131  arranged between the key-top  101  and the holder-member  130 . 
   The key-top  101 , as shown in  FIGS. 26 and 27 , is provided with a character (not shown) formed on the top surface thereof by printing, and a pair of rotational retainers  101   a  and a pair of slide-retainers  101   b , which are respectively arranged on the back surface. The pair of rotational retainers  101   a  are provided with retaining slots  104  respectively formed thereon while the pair of slide-retainers  101   b  are provided with retaining slots  105  respectively formed thereon. 
   The guide-supporting member  106  is formed of two resin-made lever members  107  and  108 . As shown in  FIG. 28 , one U-shaped lever member  107  comprises a pair of arms  107   a  and a base-end part  107   b  connecting one end of one arm  107   a  to that of the other arm  107   a . The other end of each arm  107   a  is provided with a retainer pin  107   d  protruded therefrom, and the central part of each arm  107   a  is provided with a shaft  107   c  formed inside thereof to protrude therefrom. 
   The other lever member  108 , as shown in  FIG. 29 , comprises a pair of arms  108   a , a base-end part  108   b  connecting one end of one arm  108   a  to that of the other arm  108   a , retainer pins  108   d  formed at the other end of each arm  108   a , and a depressing shaft  110  for connecting inside central parts of the arms  108   a  together. The central part of each arm  108   a  is provided with a hole  108   c  formed outside thereof, and at one end of each arm  108   a , a retainer pin  108   e  is formed to protrude from outside. 
   The holder member  130 , as shown in  FIGS. 26 and 27 , is formed of a metallic flat plate and comprises a pair of fitting parts  126  and a pair of retainers  127 , which are cut-up from the surface. In addition, on the top surface of the holder member  130 , a metallic frame  132  having plural openings  132   a  is arranged, and the fitting parts  126  and the retainers  127  protrude upwardly from the openings  132   a  of the frame  132 . 
   The base-end part  107   b  of the one lever member  107  is rotatably retained in the retaining slots  104  of the rotational retainers  101   a  while the retainer pins  107   d  are slidably retained to the fitting parts  126  of the holder member  130 . 
   Also, the retainer pins  108   d  of the other lever member  108  are slidably retained in the retaining slots  105  of the slide-retainers  101   b  of the key-top  101 , while the retainer pins  108   e  are rotatably retained in the retainers  127  of the holder member  130 . 
   Next, assembling of the key-switch device will be described: a conductive film sheet (not shown) is placed on the holder member  130 . In addition, the sheet has the rubber spring  131  bonded thereon in advance. From the sheet, the fitting parts  126  of the holder member  130  and the retainers  127  protrude upwardly through the openings  132   a  of the frame  132 . 
   Next, the one lever member  107  and the other lever member  108  are crosswise combined together so that each shaft  107   c  is rotatably inserted into the hole  108   c  so as to complete the guide-supporting member  106 . Then, while the retainer pins  108   e  of the lever member  108  are press-fitted into holes of the retainers  127  of the holder member  130 , the retainer pins  107   d  are slidably retained in the fitting parts  126 . At this time, the depressing shaft  110  is positioned on the rubber spring  131 . 
   Next, the key-top  101  is prepared so as to elastically abut the retainer pins  108   d  of the lever member  108  by depressing them from an obliquely upper direction (upper right part of FIG.  26 ), and the retainer pins  108   d  of the lever member  108  are inserted into the retaining slots  105  of the key-top  101  by trial and error. 
   Furthermore, the key-top  101  is urged to an upper part (the base-end part  107   b  and the retainer pins  108   d ) of the lever members  107  and  108  from the upper part so as to snap the retaining slots  104  of the key-top  101  into the base-end part  107   b  of the lever member  107 . 
   In such a manner, the key-switch device is completed. 
   Next, operation of the key-switch device will be described: referring to  FIG. 26 , when pushing down the key-top  101 , the base-end part  107   b  of the one lever member  107  rotates within the retaining slots  104  of the rotational retainers  101   a  while the retainer pins  108   d  of the other lever member  108  slides within the retaining slots  105  of the slide-retainers  101   b  horizontally (the lateral direction in FIG.  26 ). Simultaneously, the base-end part  108   b  of the lever member  108  rotates within retaining holes of the retainers  127  of the holder member  130  while the retainer pins  107   d  of the lever member  107  slides within the fitting parts  126  for slidably retaining the pin horizontally (the lateral direction in FIG.  26 ). 
   As a result, a bearing A for mutually journaling the lever members  107  and  108  on bearings moves downwardly while the depressing shaft  110  pushes the rubber spring  131  down gradually so as to be buckled. Thereby, a movable contact (not shown) within the rubber spring  131  establishes a short circuit in a fixed-contact pattern (not shown) on the holder member  130  so as to perform a predetermined switching operation. 
   When the pushing-down of the key-top  101  is canceled, the bearing A of both the lever members  107  and  108  is pushed up due to an elastic restoring force of the rubber spring  131  so as to perform the reverse operation (switching-off operation) to that mentioned above, resulting in returning the key-top  101  to the original position. 
   As mentioned above, various different characters or symbols may be printed on the key-tops  101  attached to the lever members  107  and  108 . 
   A number of problems exist with the conventional key-top thus described. For example, after the key-switch device is assembled in advance, it may need to be changed to that of a different kind according to demand during assembling or after assembling. When removing the key-top  101  from the lever members  107  and  108 , the key-top  101  has to be changed while maintaining the intersecting angle between the lever members  107  and  108 . This is an extremely complicated operation unless a specially designed jig is used. 
   Another problem occurs when assembling the key-switch device: first, after assembling the guide-supporting member  106 , in which the lever members  107  and  108  are crossed with each other, both the retainer pins  108   e  and  108   e  of the lever member  108  are press-fitted into the retainers  127  of the holder member  130 . 
   Then, the retainer pins  107   d  and  107   d  of the one lever member  107  are inserted into both the fitting parts  126  and  126  so as to assemble the lever members  107  and  108  into the holder member  130 . However, since the slender resin lever member  107  is liable to deflect, the retainer pins  107   d  and  107   d  sliding on the surface of the holder member  130  may simply come off the fitting parts  126  during the assembling. 
   In addition, also when operating as the key-switch device, the retainer pins  107   d  of the lever member  107  are slidably retained in the fitting parts  126 ; however, since each retainer pin  107   d  simply extends in the longitudinal direction, it may come off the fitting part  126  when sliding. 
   The rotational retainers  101   a  of the key-top  101  are snapped into the base-end part  107   b  of the lever member  107  via the retaining slots  104 ; however, since the lower snapping side of the rotational retainer  101   a  is open, there is a problem that the key-top  101  may simply come off the lever member  107  when an external force pushing up the key-top  101  is applied. 
   When the key-top  101  is assembled into the lever members  107  and  108 , the key-top  101  is assembled in a state that the retaining slots  104  and the retaining slots  105  formed on the back side of the key-top  101  are downward oriented so that they cannot be visually confirmed, resulting in the complicated assembling operation. 
   Also, when the base-end part  108   b  of the lever member  108  is inserted and assembled into the retainers  127  of the holder member  130 , there is a problem that the base-end part  108   b  cannot be smoothly inserted by catching on the sliding contact part of the retainers  127  into the base-end part  108   b  of the lever member  108  on the top surface of the holder member  130 . 
   SUMMARY OF THE INVENTION 
   One object of the present invention is to provide a key-switch device, in which assembling operation is simplified when a key-top is attached to lever members crosswise intersecting each other. 
   In order to solve at least one of the problems described above, in accordance with a first aspect of the present invention, a key-switch device comprises a key-top having retainers formed on the back surface of the key-top, first and second levers disposed under the key-top, each lever including a base-end part and a pair of arms opposing each other and extending from both ends of the base-end part, the first and second levers being connected together rotatably about the substantial center of the pair of arms as an intersecting point, a lever-holding plate, which can retain each lower end of the first and second levers, and an actuator member attached to and spanned between both the base-end parts of the first and second levers, wherein the actuator member has a concave slide-retainer-receiving part with the open top, and wherein the base-end part of the second lever is slidably retained in the slide-retainer-receiving part. 
   Preferably, the base-end part of the first lever comprises a support-receiving part formed in the center of the base-end part for retaining one end of the actuator member, both ends of the support-receiving part being provided with retainer-receiving parts formed for retaining the retainers of the key-top, and wherein the retainers of the key-top and the retainer-receiving parts of the first lever are opposed in order to be retained together to have a section shaped like two-commas. 
   Preferably, the retainers of the key-top comprise a pair of first retainers and a pair of second retainers, the pairs of first and second retainers being formed on the back surface of the key-top so as to protrude therefrom, wherein the back surface of the key-top is provided with a pair of first ribs formed to protrude from the back surface more distal to a center of a lateral side of the key-top than the second retainers, which oppose each other, and a second rib extending in parallel with the first ribs in the vicinity of the first retainers any without extending to a position between the first retainers, and wherein the key-top is inserted into and mounted on the first lever and the actuator member by respectively guiding the pair of arms of the first lever and the other end of the actuator member with the first ribs and the second rib. 
   Preferably, the base-end part of the first lever is rotatably journaled on bearings by one end of the actuator member, and the lower corner of the other end of the actuator member is obliquely cut with respect to a lower surface of the actuator member. 
   In accordance with a second aspect of the present invention, a key-switch device comprises first and second levers rotatably connected to each other about an intersecting point, a key-top supported by the first and second levers so as to be movable up and down, a switch member being switchably operable in accordance with the up-and-down movement of the key-top, and a lever-holding plate having a lower-slide retainer for slidably retaining the lower end of the first lever and a retainer unit for rotatably journaling the lower end of the second lever on bearings, and wherein the lower end of the first lever is provided with a detachment-preventing part formed for preventing the lower end of the first lever from coming off (inadvertently detaching from) the lower-slide retainer. 
   Preferably, the detachment-preventing part is an L-shaped retainer pin protruding from the lower end of the first lever and retained in the lower-slide retainer. 
   In accordance with a third aspect of the present invention, a key-switch device comprises first and second levers rotatably connected to each other about an intersecting point, a key-top supported by the first and second levers so as to be movable up and down, a switch member being switchably operable in accordance with the up-and-down movement of the key-top, and a lever-holding plate having retainers for respectively retaining lower ends of the first and second levers, wherein the respective first and second levers are provided with a base-end part and a pair of arms formed so as to extend from both ends of the base-end part and to oppose each other, the base-end part and the pair of arms being formed for guiding the up-and-down movement of the key-top, wherein the retainers of the lever-holding plate are classified into a lower-slide retainer for slidably retaining the lower end of the first lever and a retainer for rotatably journaling the lower end of the second lever on bearings, and wherein an end face of the first lever at the lower end, the end face sliding on the top surface of the lever-holding plate, is obliquely cut so as to have an acute angle relative to the extending direction of each arm. 
   In accordance with a fourth aspect of the present invention, a key-switch device comprises a key-top having a plurality of retainers formed on the back surface of the key-top, first and second levers disposed under the key-top, each lever including a base-end part and a pair of arms opposing each other and extending from both ends of the base-end part, the pairs of the arms being arranged movably with each other, a lever-holding plate, which can retain each of lower ends of the first and second levers, a connection member attached to and spanned between both of the base-end parts of the first and second levers, and a sheet switch arranged on the bottom surface of the lever-holding plate, wherein both ends of the connection member are provided with engaging parts formed for retaining to the retainers of the key-top, and the lever-holding plate is made of a metallic flat plate having substantially the same area as that of the key top. 
   In accordance with a fifth aspect of the present invention, a key-switch device comprises first and second levers connected to each other rotatably about an intersecting point, a key-top supported by the first and second levers so as to be movable up and down, a switch member being switchably operable in accordance with the up-and-down movement of the key-top, and a lever-holding plate for respectively retaining lower ends of the first and second levers, wherein the lever-holding plate is provided with a lower-slide retainer for slidably retaining the lower end of the first lever and a retainer unit for rotatably journaling the lower end of the second lever on bearings. 
   Preferably, part of the retaining unit is open and the retaining unit comprises a lower-rotational retainer for positioning the lower end of the second lever and a detachment-preventing retainer for preventing the lower end of the second lever from becoming detached. 
   Preferably, the detachment-preventing retainer is a projection protruding from the lever-holding plate. 
   Preferably, the second lever comprises a pair of arms arranged in parallel with each other, a connection part for connecting one end of one arm to that of the other arm of the pair of arms, and a pair of lower-rotational-retaining projections formed to extend from each of the arms, in which the connection part is formed, and wherein the respective lower-rotational-retaining projections are retained in the lower-rotational retainer. 
   Preferably, the projection is provided with a fractured plane formed by projecting part of the lever-holding plate, and the connection part abuts the fractured plane. 
   Preferably, a plurality of the projections protrude from the lever-holding plate to form the detachment-preventing retainer and are disposed in the vicinity of the lower-rotational retainer such that the connection part is clampable by the lower-rotational retainer and the projections forming the detachment-preventing retainer. 
   Since the key-switch device according to the present invention is configured in the manner described in the first aspect of the present invention, the key-top can be simply mounted in a state that a predetermined intersecting angle between the first and second levers is maintained due to the actuator member. 
   Since the key-switch device is configured in the manner described in the second aspect of the present invention, even when the first lever, which slides laterally when pressing the key-top in the vertical direction, deflects due to defects or irregularities in the resin or changes caused by the passage of time, predetermined operation can be securely performed without detachment. 
   Since the key-switch device is configured in the manner described in the third aspect of the present invention, the first lever can be smoothly assembled while sliding it in contact on the top surface of the lever holding plate. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of a key-switch device according to an embodiment of the present invention; 
       FIG. 2  is a plan view of the key-switch device according to the embodiment of the present invention, in which a key-top is omitted; 
       FIG. 3  is a partial plan view of the key-switch device according to the embodiment of the present invention viewed from the back-face side of a key-top; 
       FIG. 4  is a back view of the key-top in the key-switch device according to the embodiment of the present invention; 
       FIG. 5  is a sectional view of the key-top shown in FIG.  4 ; 
       FIG. 6  is a plan view of a lever holding plate in the key-switch device according to the embodiment of the present invention; 
       FIG. 7  is a drawing of the lever holding plate shown in FIG.  6  and viewed in the arrow direction at the line  7 — 7 ; 
       FIG. 8  is a drawing of the lever holding plate shown in FIG.  6  and viewed in the arrow direction at the line  8 — 8 ; 
       FIG. 9  is a plan view of an outside lever in the key-switch device according to the embodiment of the present invention; 
       FIG. 10  is a front view of the outside lever shown in  FIG. 9 ; 
       FIG. 11  is a partially enlarged view of the outside lever shown in  FIG. 10 ; 
       FIG. 12  is a rear view of the outside lever shown in  FIG. 9 ; 
       FIG. 13  is a side view of the outside lever shown in  FIG. 9 ; 
       FIG. 14  is a sectional view of the outside lever shown in  FIG. 9  at the line  14 — 14 ; 
       FIG. 15  is a drawing of the outside lever shown in FIG.  9  and viewed in the arrow direction at the line  15 — 15 ; 
       FIG. 16  is a partially enlarged sectional view of the outside lever shown in  FIG. 15 ; 
       FIG. 17  is a back view of the outside lever shown in  FIG. 9 ; 
       FIG. 18  is a drawing of the outside lever shown in FIG.  17  and viewed in the arrow direction at the line  18 — 18 ; 
       FIG. 19A  is a plan view of an inside lever in the key-switch device according to the embodiment of the present invention; 
       FIG. 19B  is a side view of the inside lever; 
       FIG. 20A  is a plan view of an actuator member in the key-switch device according to the embodiment of the present invention; 
       FIG. 20B  is a sectional view of the actuator member viewed in the arrow direction at the line  20 B— 20 B; 
       FIG. 21A  is a partial plan view for illustrating assembling of a link member in the key-switch device according to the embodiment of the present invention; 
       FIG. 21B  is a rear view of the link member; 
       FIG. 22  is a partial plan view of the key-switch device according to the embodiment of the present invention, in which the key-top is removed; 
       FIGS. 23A ,  23 B, and  23 C are schematic representations for illustrating assembling of the link member in the key-switch device according to the embodiment of the present invention:  FIG. 23A  is a schematic representation for illustrating a state before the link member is assembled into the lever holding plate;  FIG. 23B  is a schematic representation for illustrating a state that the link member is placed on the lever holding plate; and  FIG. 23C  is a schematic representation for illustrating a state that the link member is assembled into the lever holding plate; 
       FIG. 24  is a schematic representation for illustrating an example of assembling operation of the link member into the lever holding plate in the key-switch device according to the embodiment of the present invention; 
       FIG. 25  is a schematic representation for illustrating assembling of the key-top into the link member in the key-switch device according to the embodiment of the present invention; 
       FIG. 26  is a sectional view of a conventional key-switch device; 
       FIG. 27  is an assembly view of the conventional key-switch device; 
       FIG. 28  is a plan view of one link member for use in the conventional key-switch device; and 
       FIG. 29  is a plan view of the other link member for use in the conventional key-switch device. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A key-switch device according to an embodiment of the present invention will be described with reference to  FIGS. 1  to  25 . 
   The key-switch device, as shown in  FIG. 1 , principally comprises a key-top  11  made of a resin, a lever-holding plate  15  disposed beneath the key-top  11 , a link member  20  for guiding and supporting the key-top  11  between an elevated position of the key-top separated from the lever-holding plate  15  and a lowered position in which the key-top is disposed closer to the lever-holding plate  15  than when in the elevated position, and a switch member  30  arranged between the link member  20  and the lever-holding plate  15 . 
   The key-top  11  has a substantially rectangular external-shape, as shown in  FIGS. 3  to  5 . The key-top  11  comprises an operating surface  11   a  (see  FIG. 5 ) with a character (not shown) such as an alphabet letter printed on the top surface thereof, an inclined surface  11   b  slantingly formed in the front (the left side in FIG.  5 ), a rear face  11   c  formed substantially at a right angle in the rear, a back surface  11   d  formed underneath the operating surface  11   a  substantially in parallel with the operating surface  11   a , and an external-peripheral-fringe surface  11   e  formed on the external-peripheral fringe in the side of the back surface  11   d.    
   The back and front sides (both the lateral sides in  FIG. 4 ) of the back surface  11   d  are provided with a pair of first hook-like retainers  11   f  arranged to oppose each other and to be spaced by a predetermined distance therebetween and a pair of hook-like second retainers (retainers)  11   g  arranged to oppose each other and to be spaced by a distance larger than that of the first retainers  11   f , both the first and second retainers  11   f  and  11   g  being arranged integrally with the back surface  11   d  so as to protrude downwardly. 
   The back surface  11   d  of the key-top  11  is provided with a pair of first ribs  11   j  formed to protrude from the back surface  11   d  in the vicinity of the exterior of the second retainers  11   g  (which oppose each other) and a second rib  11   h.  The second rib  11   h  extends in parallel with the first ribs  11   j  in the vicinity of the first retainers  11   f , but does not extend to a position between the first retainers  11   f . Both the first and second ribs  11   j  and  11   h  are arranged integrally with the back surface  11   d  so as to be flush with the external-peripheral-fringe surface  11   e.    
   The link member  20 , as shown in  FIGS. 1 ,  21 A, and  21 B, comprises a pair of lever members (a first lever  24  and second lever  25 )  23  and one actuator member  26 . 
   The first lever (outside lever)  24  made of a resin, as shown in  FIGS. 9  to  18 , comprises a base-end part  24   a  and a pair of arms  24   b  integrally arranged to extend from both ends of the base-end part  24   a  and to oppose each other, the base-end part  24   a  and the arms  24   b  being arranged to be a substantially U-shape. 
   The end (the other end) of each arm  24   b  is a free end and is provided with a pair of retaining pins (detachment preventing parts)  24   c  formed to outwardly protrude. 
   More specifically, the retaining pin  24   c  comprises a sliding contact part  24   c   1  formed on the external wall of the arm  24   b  in the end side to extend in parallel with the longitudinal direction of the base-end part  24   a  and an end part  24   c   2  bent upwardly from the end of the sliding contact part  24   c   1  at a substantially right angle (see FIG.  11 ). 
   Also, the end (lower end) of the arm  24   b , as shown in  FIGS. 13 and 15 , is provided with an inclined part  24   u  formed by slantingly cutting an end face thereof so as to have an acute angle (θ) relative to an extending direction (extension line L) of each arm  24   b.    
   The base-end part  24   a , as shown in  FIG. 16 , is provided with a support-receiving part  24   e  formed in the central part of the base-end part  24   a  so as to have a circular cross-section with a small diameter and retainer-receiving parts  24   f  formed in both-ends sides of the base-end part  24   a  so as to have a substantially L-shaped cross-section (see FIG.  18 ). 
   The pair of second retainers  11   g  of the key-top  11  are tightly mated to the retainer-receiving parts  24   f.  When the retainer-receiving parts  24   f  of the first lever  24  oppose the second retainers  11   g  of the key-top  11 , the section of the retaining part thereof is shaped like two commas (see FIG.  18 ). Engaging slots  24   d  and  24   d  are formed by cuffing-up from the inside so as to oppose each other on internal walls of the arms  24   b  in substantially central parts, as shown in FIG.  17 . 
   The second lever (inside lever)  25  made of a rectangular resin-frame having an opening in the center, as shown in  FIGS. 19A and 19B , comprises a base-end part  25   a , a base-shaft part  25   c  arranged in parallel with the base-end part  25   a , and a pair of arms  25   b  arranged in parallel with each other so as to integrally connect respective both ends of the base-end part  25   a  and the base-shaft part  25   c  together. Or in other words, the pair of arms  25   b  are connected by a connection part, i.e. the base-shaft part  25   c.    
   On the substantially central outside wall of each arm  25   b , an engaging shaft  25   d  is formed to protrude outside. 
   On the outside wall of each arm  25   b  in the side of the base-shaft part  25   c , a lower-rotational-retaining projection  25   e  is formed to protrude outside. 
   The respective engaging shafts  25   d  are brought into engagement with the engaging slots  24   d  of the first lever  24  so as to form an intersecting point S (see FIG.  1 ), so that the first lever  24  and the second lever  25  are rotatable with each other via the intersecting point S. In addition, the base-shaft part  25   c  is placed as the lower end of the second lever  25 . 
   Then, the actuator member  26  made of a resin, as shown in  FIGS. 20A and 20B , comprises a base  26   a  having a substantially rectangular flat-plate shape. The base  26   a  is provided with a rubber-cap abutting part  26   b  formed on the central back surface to have a circular shape with a thinner thickness than other portions of the base  26   a.    
   On the back surface of the base  26   a , a substantially rectangular retaining-projection  26   d  is integrally formed on one end side of the longitudinal direction of the base  26   a  (in the right of  FIG. 20A ) so as to protrude from the base  26   a . Also, on the central internal side of the retaining projection  26   d , a second retaining-projection  26   k  is integrally formed so as to protrude from the back surface of the base  26   a  and to oppose the retaining-projection  26   d.    
   The base  26   a  between the retaining-projection  26   d  and second retaining-projection  26   k  is provided with a substantially rectangular retaining-hole  26   e  formed so as to pass through the base  26   a , and a circular slot  26   g  with a C-shaped cross-section is formed along the retaining-hole  26   e  on one end side of the actuator member  26 . 
   On the base  26   a , an upper slide-receiving part (slide retainer-receiving part)  26   c  having a substantially U-shaped cross-section is formed on the other end side of the longitudinal direction of the base  26   a  (in the left of FIG.  20 A). The upper slide-receiving part  26   c  is provided with a groove  26   m  with an open upper part. 
   Furthermore, on the central outside end-face of the upper slide-receiving part  26   c  (on the left end-face of FIG.  20 A), a retaining projection  26   t  is formed to protrude, and on both sides of the retaining projection  26   t , retaining-receiving parts  26   s  are respectively formed. 
   Also, the lower corner of the retaining projection  26   t  of the upper slide-receiving part  26   c  is formed to be an inclined-face part  26   u  by diagonally cutting. 
   Next, the lever holding plate  15 , as shown in  FIGS. 6  to  8 , comprises a base  15   a  formed of a substantially rectangular metallic flat plate. 
   As shown in  FIG. 6 , the base  15   a  of the lever holding plate  15  is provided with a through-opening  15   b  formed in the central part. 
   On one end side of the base  15   a  (in the left of the drawing), a pair of first rectangular openings  15   c  are formed close to the through-opening  15   b , and on the other end side of the base  15   a  (in the right of the drawing), a pair of second substantially rectangular openings  15   d  are formed to have a predetermined space therebetween. 
   The base  15   a  is further provided with a retainer unit  17  comprising a pair of detachment-preventing retainers (projections)  19  disposed between the pair of second rectangular openings  15   d  and a pair of lower rotational retainers  18  formed to respectively face the internal sides of the second rectangular openings  15   d.    
   Specifically, the pair of lower rotational retainers  18  are formed by cutting-up (i.e. cutting and bending) the internal edges of the second rectangular openings  15   d  at a substantially right angle so as to have a substantially L-shape, and the pair of detachment-preventing retainers (projections)  19  are formed by projecting so as to protrude partly from the top surface of the base  15   a  to form fractured planes erected at a substantially right angle on the side of the through-opening  15   b.    
   As shown in  FIG. 6 , the lever holding plate  15  is provided with a pair of lower-slide retainers  16  formed at corners on the sides of the base  15   a  (vertical sides of  FIG. 6 ) by cutting-up (i.e. cutting and bending) the corners of the lever holding plate  15  from the base  15   a  at a substantially right angle so as to have an L-shape. 
   At side ends of the base  15   a  (ends on vertical sides of the drawing), cut-up parts  15   f  are formed by cutting-up from the base  15   a  at a substantially right angle and arranged to be adjacent to the right in the drawing of the lower-slide retainers  16 . 
   The central part of each cut-up part  15   f  is a cut-slot, in which a tongue piece  15   g  extends downwardly and also slightly protrudes outwardly. 
   The base  15   a  is further provided with detachment-preventing-protruded pieces  15   h  integrally formed at side ends of the base  15   a  (ends on vertical sides in  FIG. 6 ) and arranged to be adjacent to the cut-up parts  15   f.    
   Then, the switch member  30 , as shown in  FIGS. 1 and 22 , is a so-called membrane switch having an elastic rubber cap  31  arranged in the upper part. 
   The switch member  30  comprises an insulating film sheet  33  and a pair of fixed electrodes (not shown), which are arranged on the film sheet  33  as part of plural switching elements. 
   The rubber cap  31  is provided with a pressing projection  31   a , which is formed inside a dome-like ceiling part of the rubber cap  31  so as to protrude downwardly, and a movable electrode  32 , which is made of a conductive film and is formed by printing or the like at the end of the pressing projection  31   a  so as to abut the pair of fixed electrodes for switching. 
   Then, the lower end of the rubber cap  31  is bonded on the film sheet  33  with an adhesive, etc., so that the movable electrode  32  of the pressing projection  31   a  opposes the fixed electrode (not shown). 
   A rectangular metallic holding plate  37  having plural openings  37   a  is put on top of the lever holding plate  15 , and the pair of lower-slide retainers  16 , the pair of lower rotational retainers  18 , the detachment-preventing retainers (projections)  19 , and the link member  20 , which are formed on the lever holding plate  15 , protrude upwardly from the openings  37   a.    
   Under the film sheet  33 , a metallic plate  40  is also laid. 
   Next, an assembling method of the key-switch device configured in such a manner will be described below with reference to  FIGS. 21A and 21B  to  25 . 
   First, as shown in  FIGS. 21A and 21B , the first lever (outside lever)  24  is put on the second lever (inside lever)  25  from the upper part so that each engaging slot  24   d  of the first lever  24  is brought into engagement with each engaging shaft  25   d  of the second lever  25  so as to assemble the lever members  23  which are connected together so as to be rotatable about an intersecting point S. 
   Continuously, the actuator member  26  is prepared; the side of the retaining projection  26   t  of the actuator member  26  is inserted into the central opening part of the second lever  25  among the first and second levers  24  and  25  forming the lever members  23 , while in this state, the base-end  25   a  of the second lever is abutted to the inside the upper slide-receiving part  26   c . Then, the retaining-projection  26   d  is downward moved to the support-receiving part  24   e  of the first lever  24  so that the slot  26   g  of the retaining-projection  26   d  is snapped and fitted into the support-receiving part  24   e . In such a manner, the link member  20  is completed. 
   Next, as shown in  FIG. 23A , the lever holding plate  15  is prepared; the link member  20  is downward inserted on the top surface of the lever holding plate  15 . The link member  20  is placed on the top surface of the lever holding plate  15  in a state that the first and second levers  24  and  25  of the link member  20  overlap horizontally. 
   Then, as shown in  FIG. 23B , the link member  20  is moved in the M direction of the drawing while sliding the link member  20  in contact with the top surface of the base  15   a  of the lever holding member  15  in the state that the first and second levers  24  and  25  of the link member  20  overlap horizontally. At that, each retaining pin  24   c  of the first lever  24  is slidably brought into engagement with the lower-slide retainer  16 . 
   In addition, even when the link member  20  is oblique relative to the top surface of the base  15   a  of the lever holding member  15 , as shown in  FIG. 24 , or even when the retaining pin  24   c  is directly inserted into the lower-slide retainer  16  obliquely from the rear (upper right in FIG.  23 A), the link member  20  can be smoothly inserted without any resistance by inserting it along the inclined part  24   u  of the first lever  24 . 
   Since the upper slide-receiving part  26   c , which is the free end of the actuator member  26 , is rotatably journaled by the support-receiving part  24   e  of the first lever  24  via the circular slot  26   g , the inclined-face part  26   u  slides on the top surface of the base  15   a  of the lever holding plate  15  during the assembling. At this time, the link member  20  is smoothly inserted due to oblique chamfering. 
   The base-shaft part  25   c  of the second lever  25  gets over the pair of detachment-preventing retainers  19  of the lever holding plate  15  while sliding in contact with them so as to be positioned in the clamped state between the lower rotational retainers  18  and the fractured planes of the detachment-preventing retainers  19 , while the lower-rotational-retaining projections  25   e  are brought into the lower rotational retainers  18 . 
   In such a manner, the lower ends of the first and second levers of the link member  20  are attached on the lever holding plate  15 . 
   Next, the lever holding plate  15  having the link member  20  attached thereto is upward inserted toward the openings  37   a  of the holding plate  37  and is brought into engagement therewith by snapping-in the cut-up parts  15   f  of the lever holding member  15 . 
   Continuously, the film sheet  33  having the rubber cap  31  bonded to the lower end thereof with an adhesive in advance is arranged under the holding plate  37 . Then, the film sheet  33  is put on the holding plate  37  while the rubber-cap abutting part  26   b  of the actuator member  26  abuts the top of the rubber cap  31 , and the metallic plate  40  is further put under the film sheet  33  (see FIG.  22 ). 
   Next, the key-top  11  is prepared: the key-top  11  is downward put on the link member  20 , which is exposed from the openings  37   a  of the holding plate  37 . 
   At this time, to the link member  20 , which is at the elevated position due to the elastic force of the rubber cap  31  as shown in  FIG. 1 , the key-top  11  is downward pressed using the pair of first ribs  11   j  and the second rib  11   h  as guides during inserting the key-top  11 . Then, as shown in  FIG. 3 , the retaining projection  26   t  of the actuator member  26  is fitted between the first retainers  11   f , so that the first retainers  11   f  of the key-top  11  are snapped in the retaining-receiving parts  26   s , while the retaining-projection  26   d  of the actuator member  26  is arranged between the second retainers  11   g , so that the second retainers  11   g  of the key-top  11  are snapped in the retainer-receiving parts  24   f  (see FIGS.  2  and  3 ). 
   Then, the rubber cap  31  recovers due to the elastic force thereof so that the link member  20  is elevated. According to the elevation, the sliding contact part  24   c   1  of the retaining pin  24   c  of the first lever  24  securely slides within the lower-slide retainer  16  while being guided by the end part  24   c   2 , thereby completing the key-switch device shown in FIG.  1 . 
   The embodiment according to the present invention has been described; however, the present invention is not limited the embodiment described above, and modifications may be made within the spirit and scope of the invention. 
   The key-switch device according to the embodiment configured and assembled as described above has the advantages as follows: 
   1) The actuator member  26  has the slide-receiving part  26   c  formed therein having the groove  26   m  with an open upper part, and the base-end part  25   a  of the second lever  25  is slidably retained to the slide-receiving part  26   c , so that the key-top  11  can be readily installed while maintaining a predetermined intersecting angle between the first and second levers  24  and  25  due to the actuator member  26 .
 
2) The base-end part  24   a  of the first lever  24  has the support-receiving part  24   e  at the center for retaining one end of the actuator member  26  while the retainer-receiving parts  24   f  for retaining the second retainers  11   g  of the key-top  11  are formed on both sides of the support-receiving part  24   e , so that the second retainers  11   g  and the retainer-receiving parts  24   f  are opposed and retained to each other. This portion is formed to have a patterned section shaped like two-commas, so that even when an external force is accidentally applied to the key-top  11 , the key-top  11  can be securely held not to simply come off the link member  20 .
 
3) The retainer of the key-top  11  comprises a pair of first retainers  11   f  and a pair of second retainers  11   g , which are formed on the back surface  11   d  so as to protrude therefrom, and the back surface  11   d  of the key-top  11  is provided with a pair of first ribs  11   j.  The first ribs  11   j  protrude from the back surface  11   d  in the vicinity of the exterior of the second retainers  11   g,  i.e. more distal to the center of the lateral side on which the first ribs  11   j  and the second retainers are formed. The second rib  11   h  extends in parallel with the first ribs  11   j  in the vicinity of the first retainers  11   f,  without extending to a position between the first retainers  11   f.  The key-top  11  is then mounted by respectively guiding the pair of arms  24   b  of the first lever  24  and the other end of the actuator member  26  with the first ribs  11   j  and the second rib  11   h.  Thereby, the key-top  11  can be simply and securely mounted by using the first ribs  11   j  and the second rib  11   h  as guides without mounting by guessing roughly as in a conventional device.
 
4) The base-end part  24   a  of the first lever  24  is journaled on bearings by the one end of the actuator member  26 , and the lower corner of the other end of the actuator member  26  is obliquely cut with respect to a lower surface of the actuator member  26 , so that the actuator member  26  can be smoothly assembled while sliding it in contact with the top surface of the base  15   a  of the lever holding plate  15 .
 
5) The retaining section of the lever-holding plate  15  comprises a lower-slide retainer  16  for slidably retaining the lower end of the first lever  24  and a retainer unit  17  for rotatably journaling the lower end of the second lever  25  on bearings, and the lower end of the first lever  24  is provided with a retaining pin  24   c , which is a detachment preventing part formed for preventing the lower end of the first lever  24 , so that when the key-top  11  is pressed to operate, even when the sliding first lever  24  deflects due to defects in the resin or changes caused by the passage of time, predetermined operation can be securely performed without detachment.
 
6) At the lower end of the first lever  24 , the end face sliding on the top surface of the base  15   a  of the lever-holding plate  15  is obliquely cut so as to have an acute angle relative to the extending direction of each of the arms  24   b , so that the lower end of the first lever  24  can be smoothly assembled while sliding the first lever  24  in contact with the top surface of the base  15   a  of the lever holding plate  15 .