Abstract:
A keyboard switch actuates a switch sheet from a first position to a second position and correspondingly narrows a gap between a key top and the switch sheet. In keyboard switch operation, trailing claw pieces cause a cross-link to submerge allowing the switch sheet to accommodate an integrally formed return springwithout elastic deformation.

Description:
This application is a continuation of PCT/JP99/07109 filed Dec. 17, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a keyboard switch for a lidded computer case. More particularly, the present invention relates to a keyboard switch that retracts multiple key switches from a stand-by orientation to a narrower storage orientation. 
     2. Description of the Prior Art 
     Conventionally known is a keyboard switch that retracts a plurality of key switches to a storage orientation within a lidded computer case. 
     A shown in FIGS. 7 through 9, a conventionally known keyboard switch (not shown) contains a plurality of key switches  100  each containing a cross-link  101 . Each cross-link  101  includes a first link member  101   a  and a second link member  101   b  pivotably coupled at intermediate pivot points  101   c . Each cross-link  101  is located between a key top  102  and a support plate  107 . 
     A bottom end of first link member  1 O 1   a  hinges to a hinged end portion  110  and couples pivotally to a support projection  109  formed from support plate  107 . A top end of first link member  101   a , having a pivotal and slidable end portion  111 , engages a guide portion  105  formed on the underside of key top  102 . Thus, first link member  101   a  both pivots and slides in a left-to-right direction in FIGS. 7 through 9. 
     A bottom end of second link member  101   b , having a pivotable and slidable end portion  112 , engages an engagement long hole  108 . A top end of second link member  101   b  hinges to a hinged end portion  113  and couples pivotally to the underside of key top  102 . 
     In FIG. 7, keyboard switch  100  is shown in a stand-by position. A dome shaped rubber elastic portion  114  is disposed under key top  102 , and serves as a return spring. Elastic portion  114  is in contact with the underside of a depressing portion  106  projected perpendicularly from the bottom side of key top  102 . 
     Elastic portion  114  is formed integrally with a rubber sheet  104  on switch sheet  103 . A membrane switch portion  103   a  is formed integrally with switch sheet  103 . Switch sheet  103  is disposed continuously under keyboard switch  102 . Rubber sheet  104  and switch sheet  103  are slidable together on support plate  107 . 
     Depressing key top  102  (from above in FIG. 7) causes key top  102 , guided by cross-link  101 , to lower in parallel with switch sheet  103 , toward switch sheet  103 , without significantly inclination. Depressing key top  102 , depresses depressing portion  106  and deforms elastic portion  114 . Deformed elastic portion  114  contacts and actuates membrane switch portion  103   a.    
     In FIG. 8, keyboard switch  100  is shown in a fully depressed position. In a fully depressed position, deformed elastic portion  114  contacts switch portion  103   a.    
     A computer unit case, mounting a keyboard switch, connects rotatably with a lid  115  which covers key tops  102  in a closing motion. 
     In FIG. 9, as lid  115  closes, rubber sheet  104  and switch sheet  103 , slide relative to support plate  107  (leftward in FIG.  9 ), in response to the closing motion. Thus, deformed elastic portion  114  retracts into a storage recessed portion  116  formed under key top  102 . 
     When deformed elastic portion  114  retracts, key top  102  and cross-link  101  drop due to their own weight provide a low profile. When deformed elastic portion  114  retracts, it does not contact switch portion  103   a.    
     Retracting elastic portion  114  into storage recessed portion  116  allows elastic portion  114  to return to an original dome shape. Retracting elastic portion  114  into storage recess  116  also removes contact with depressing portion  106 . As a result, conventional key switch  100  allows computer units to reduce overall thickness during the closing of lid  115 . However, the distance between support plate  107  and key top  102  may not be made less than the free-state height of elastic portion  114  thus limiting the minimum thickness of the computer unit. 
     Furthermore, the need for depressing portion  106  and storage recess  116 , cause each key top  102  and, hence keyboard switch  100 , to be correspondingly larger. Additionally, retracting return spring  114  into storage recess portion  116  requires sliding, thereby requiring the lid  115  mechanism to be larger and more complex. Also, sliding integral rubber sheet  104  and elastic portion  114  require a relatively large force. 
     A conventional keyboard switch (not shown) allows rubber sheet  104  and integral elastic portion  114  to slide relative to switch sheet  103 . However, this type of conventional keyboard switch has a possibility of malfunction. To limit this possibility, a friction-limiting membrane, for example polyester, has been placed between rubber sheet  104  and switch sheet  103 , thus increasing cost. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a thinner keyboard switch that does not compress a return spring during a closing motion. 
     It is another object of the present invention to provide a keyboard switch with a return spring means movable to a retracted position. 
     It is another object of the present invention to provide a keyboard switch with a simplified configuration where a return spring means is integral with a cross-link or a key top. 
     It is another object of the present invention to provide a keyboard switch, without a friction-limiting membrane, that allows a lidded computer case to open and close with little operational force. 
     In a closing operation, a keyboard switch actuates a switch sheet and a support plate from a stand-by position to a retracted position and correspondingly narrows a gap between a key top and the switch sheet. In the closing operation, trailing claw pieces cause a cross-link to submerge thereby allowing a switch sheet to accommodate an integrally formed return spring, thus allowing the return spring to retract without being elastically deformed. At the retracted position, the return spring is accommodated inside a retracting hole in the switch sheet. 
     According to an embodiment of the invention, there is provided a keyboard switch in a lidded device case comprising: a support plate within the device case, a cross-link, mounted between support projections of the support plate and a key top, the cross-link guides the key top up and down, a switch sheet arranged slidably on the support plate avoids contact with the support projections, and provides a switch portion, formed on and actuated by the key top, a return spring attached integrally to the key switch contacts the switch sheet for biasing the lowered key top upwardly, an interlock mechanism for sliding at least one of the switch sheet and the support plate relative to the other from a stand-by position to a retracted position in response to a closing operation of a lid covering the key top and sustains the key top in a lowered state, the keyboard switch for sliding the switch portion actuated by lowering the key top from the stand-by position to the retracted position where the switch portion is not actuated by lowering the key top. 
     According to another embodiment of the invention there is provided a keyboard switch further comprising: a retracting hole formed in a portion of the switch sheet, and in a retracted position, part of the return spring is accommodated inside the retracting hole. 
     According to another embodiment of the invention there is provided a keyboard switch further comprising: engagement holes into which trailing claw pieces integrally provided on the cross-link insert, where at least one of the switch sheet and the support plate slides to the retracted position, peripheral edges of the engagement holes contact with the trailing claw pieces to cause the cross-link to submerge and the key top to lower. 
     According to another embodiment of the invention there is provided a keyboard switch further comprising: a return spring means, the return spring serving as an actuator for the switch portion and upwardly biasing the key top. 
     According to another embodiment of the invention there is provided a switch sheet further comprising: slits formed integrally with the switch sheet, the slits formed on the switch sheet to fit the support projections of the support plate and serve as guide means for the support projections. 
     The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view illustrating an embodiment of the invention in a stand-by position for a key switch. 
     FIG. 2 is a cross-sectional view illustrating an embodiment of the invention in a depressed position for a key switch. 
     FIG. 3 is a cross-sectional view illustrating an embodiment of the invention in a retracted position for a key switch and a lid. 
     FIG. 4 is an exploded view illustrating an embodiment of the key switch components. 
     FIG. 5 is a plan view illustrating an open lid and keyboard switch with interlocking mechanism of the present embodiment. 
     FIG. 6 is an enlarged plan view illustrating the main portion of the interlocking mechanism shown in FIG.  5 . 
     FIG. 7 is a cross-sectional view illustrating a prior art key switch in in a stand-by position; 
     FIG. 8 is a cross-sectional view illustrating a prior art key switch in a depressed position. 
     FIG. 9 is a cross-sectional view illustrating a prior art key switch in a retracted position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 through 3, a key switch  10 , is arranged on a support plate  18 . Key switch  10  includes a key top  2 , a cross-link  13  containing an inner link  7  and an outer link  8 , connecting, to a switch sheet  3  with an integrally formed membrane switch portion  3   a.    
     Inner link  7  contains a pair of arm portions  7   a , a pair of pivot axes  7   b , and a pair of slidable projections  7   c . Arm portions  7   a  are continuously provided with a pair of trailing claw pieces  15 . Trailing claw pieces  15 , shaped in a diagonal arc, are projectable through a pair of engagement holes  16 , each having a rare edge  16   a  and an integrally formed guide slit  19  formed in switch sheet  3 . Switch sheet  3  also integrally forms a circular retracting hole  17  and a second pair of rear guide slits  12   a  for each key switch  10 . 
     Outer link  8  contains a pair of arm portions  8   a , a pair of slidable projections  8   b , and a pair of pivot axes  8   c.    
     Cross-link  13 , comprising inner link  7  and outer link  8 , is pivotally connected and crossed at respective intermediate longitudinally portions of arm portions  7   a  and  8   a.    
     At a rear portion of key top  2  (on the right in FIG.  1 ), a pair of U-shaped bearing portions  6 , formed integrally with key top  2 , pivotally support and retaining inner link pivot axes  7   b . At a front portion of key top  2  (on the left in FIG.  1 ), a pair of guide receiving portions  5 , formed integrally with key top  2 , pivotally and slidably guide outer link slidable projections  7   b.    
     Cross-link  13  is interposed between a bottom side of key top  2  and a pair of front support projections  11  (on the left in FIG. 1) and a pair of rear support as, projections  12  (on the right in FIG.  1 ). Support projections  11 ,  12 , formed by cutting and erecting part of support plate  18 , project through switch sheet  3  (vertically in FIG. 1) 
     Each front support projection  11  contains a long hole  11   a , for pivotally and slidably guiding inner link slidable projection  7   c , and a punch hole hole  11   b  formed in support plate  18 . 
     Each rear support projection  12  contains a circular hole  12   a , for pivotally supporting outer link pivot axis  8   a.    
     Thus, inner link  7  is supported pivotally and slidably back and forth and outer link  8  is supported pivotably and slidably back and forth. Cross-link  13  is therefore pivotally and slidably connected to key top  2  and support plate  18 . When depressing keyboard switch  10 , from the top in FIG. 1, key top  2  is freely guided by means of cross-link  13  while being kept primarily in a horizontal plane. 
     An elongated plate spring piece  24  is integrally and continuously formed on outer link  8  between pivot axes  7   c  and a connecting plate  22 . Connecting plate  22  extends between pivot axes  7   c  and plate spring piece  24 . Spring piece  24 , has a conical contact portion  24   a , formed by embossing, and extends in a cantilever manner diagonally and downwardly, at a rear portion of connecting plate  22 . Spring piece  24  elastically contacts the surface of switch sheet  3  on a membrane switch portion  3   a.    
     In FIG. 1, key switch  10  is shown in a stand-by position. In the stand-by position, contact portion  24   a  contacts a dish spring  4 , placed on switch sheet  3 , directly above membrane switch portion  3   a . A defined switch portion includes membrane switch portion  3   a  and dish spring  4  above membrane switch portion  3   a.    
     Membrane switch portion  3   a  includes a movable contact (not shown) and a stationary contact (not shown) printed on flexible sheets stacked one on the other with an insulating spacer interposed to allow the sheets to face to one another with a slight gap being left between. Dish spring  4 , made from a substantially elastic metal plate formed into a circular dish shape having a flanged peripheral rim. The peripheral rim of dish spring  4  is adhered to the flexible sheets and is thereby fixedly attached to switch sheet  3  above membrane switch portion  3   a.    
     At the stand-by position, contact portion  24   a  of plate spring piece  24  elastically contacts dish spring  4 , and upwardly biases outer link  8  (vertically in FIG.  1 ). Consequently, key top  2  is held at the stand-by position by means of the cross-link  13 . 
     In FIG. 2, depressing key top  2  causes key top  2  to lower in a parallel plane by means of cross-link  13 . Thus, contact portion  24   a , of plate spring piece  24 , depresses and deforms dish spring  4 . Deforming dish spring  4  causes contact between movable contact and stationary contact (described above), thereby activating membrane switch portion  3   a.    
     Releasing key top  2  causes dish spring  4  to return by its own elastic bias, thereby deactivating the switch portion. Releasing key top  2 , also energizes cross-link  13  to push upwardly by means of returning plate spring, piece  24 , thereby causing key top  2  to return to the stand-by position. 
     In FIG. 3, a closed lid  29  retracts key top  2 , creating a retracted position as shown. When retracting, switch sheet  3  shifts left relative to the cross-link  13  attached to support plate  18 . Accordingly, switch sheet  3  causes rear edges  12   a  of the engagement holes  16  to contact trailing claw pieces  15  and arm portions  7   a  of inner link  7  to rotate about slidable projections  7   c  within long holes  101   a . Consequently, cross-link  13  submerges and key top  2  is lowered, thus allowing a device case  14  (later shown in FIG.  5 ), with lid  29  covering key tops  2 , to be made thinner and with fewer pieces. 
     At the retracted position, contact portion  24   a  of plate spring piece  24  is accommodated in retracting hole  17  formed in switch sheet  3 . This allows plate spring piece  24  to be accommodated inside the device case  14  without being elastically deformed. Accordingly, this limits the occurrence of fatigue or plastic deformation of the plate spring piece  24 . 
     Furthermore, dish spring  4  and membrane switch portion  3   a , previously deflected by contact portion  24   a  of plate spring piece  24 , retract leftward (in FIG. 3) by the sliding of switch sheet  3 . This motion allows dish spring  4  and membrane switch portion  3   a  to return to a non-deflected position. This motion prevents key switch  10  from malfunctioning due to the lowering of key top  2  and provides a long life to the keyboard switch. 
     As shown in FIG. 4, switch sheet  3  is arranged slidably back and forth relative to support plate  18 . Guide slits  19  are bored at positions where front support projections  11  and rear support projections  12  protrude therethrough. This allows switch sheet  3  to slide without interfering with front support projections  11  or rear support projections  12 . The width of each guide slit  19  is larger than the thickness of each front support projection  11  and each rear support projection  12 . Guide slits  19  thereby allow switch sheet  3 , guided by means of front and rear support projections  11 ,  12 , to slide back and forth. 
     The inner sides of guide slits  19  into which front support projections  11  insert, connect continuously with engagement holes  16  thus allowing trailing claw pieces  15  of inner link  7  to penetrate a surface plane of switch sheet  3 . When the switch sheet  3  slides to a retracted position, trailing claw pieces  15  contact rear edges  12   a  of engagement holes  16  and are pushed upwardly. Trailing claw pieces  15  cause arm portions  7   a ,  7   a  of the inner link  7  to rotate about slidable projections  7   c  and thus allow arm portions  7   a ,  7   a  to recline. 
     As shown in FIGS. 5 and 6, a keyboard switch  1 , having a plurality of key switches  10  each with a key top  2 , is contained within device case  14 . Switch sheet  3  is slidable back and forth in response to the opening and closing of lid  29  by means of a conversion mechanism provided at a connecting portion between switch sheet  3  lid  29 , and device case  14 . The conversion mechanism is shown in the top left portion of FIG.  5 . 
     The conversion mechanism contains a cylindrical cam  25  that rotates integrally with a pivot axis (not shown) for pivotally supporting lid  29 . Cylindrical cam  25  contains a crank-shaped cam grove  25   a  bored in cylindrical cam  25 . A slider  26 , having a follower  26   a , is fit from inside cylinder cam  25  into cam grove  25 . A slide angle  27 , rigidly formed in the shape of an inverted English letter “L”, is fixedly attached to slider  26 . 
     An upper and left edges of switch sheet  3 , shown in FIG. 5, are fixedly pressed against a bent grove along the inside of slide angle  27 . This allows flexible switch sheet  3  to slide in conjunction with slide angle  27 . Consequently when lid  29  moves, the conversion mechanism actuates and slider  26  reciprocates in a straight line (to the left and right of FIG.  6 ). As slider  26  reciprocates, switch sheet  3  slides in conjunction with slider  26 . 
     Closing lid  29  causes switch sheet  3 , moving in conjunction with slider  26 , to slide (downward in FIG.  5  and leftward in FIG. 6) from the stand-by position, shown by the dashed line, to the retracted position, shown by the solid line. 
     Opening lid  29  causes switch sheet  3  and slider  26  to slide from the retracted position shown by the solid line to the stand-by position shown by the dashed line. 
     Additionally referring now to FIGS. 1 through 4. Opening lid  29  causes rear edges  12   a  of engagement holes  16 , in contact with trailing claw pieces  15 , to retract rightward and release restraint on trailing claw pieces  15 . At the same time, the sliding of switch sheet  3 , described above, causes the free end of plate spring piece  24  to escape from retracting hole  17 , and allow contact portion  24   a  to elastically contact switch sheet  3 . Consequently, the elasticity of plate spring piece  24  causes cross-link  13  to be pushed upward and key top  2  to return to the stand-by position. Furthermore, the sliding of switch sheet  3  causes dish spring  4  and membrane switch portion  3   a  to return to contact portion  24   a  of plate spring piece  24 . Thus the elastic pressure of contact portion  24   a  and dish spring  4  allows key switch  10  to return to the stand-by position of FIG.  1 . 
     The present invention may be modified with respect to the aforementioned embodiment. For example, the present invention moves the switch sheet  3  in response to lid  29  movement. Alternatively, lid  29  movement may move support plate  18 . In a second example, plate spring piece  24  both allows key top  2  to return to a stand-by position and serves as an actuator for actuating the key top  2 . Alternatively an actuator for key top  2  may be connected separately to key top  2  or differently to cross-link  13 . 
     Furthermore, the aforementioned embodiment employs dish spring  4  to actuate membrane switch portion  3   a , alternatively, dish spring  4  may be inverted and still sustain the actuating operation of membrane switch portion  3   a . Additionally, it is not necessary to provide dish spring  4  at membrane switch portion  3   a , contact portion  24   a  may independently actuate membrane switch  3   a.    
     The aforementioned embodiment employs cylindrical cam  25  and slider  26  as an interlock mechanism for allowing switch sheet  3  to slide in conjunction with lid  29  motion. However, other interlock mechanisms containing, for example, a connective bevel gear or the like may be employed. 
     Additionally, when keyboard switch  1  is accommodated inside device case  14 , key top  2  may be kept in a lowered state using switch sheet  3  or support plate  18  without the need for a special complicated structure. Accordingly, this lowered state prevents key top  2  from interfering with closed lid  29  and prevents both key tops  2  and, for example a liquid crystal display, disposed on the reverse side of lid  29  from being damaged. 
     Additionally, since plate spring piece  24  serves both as a return spring means and as an actuator for depressing and actuating membrane switch portion  3   a  the number of parts used reduced and the structure is simplified. 
     Additionally, since sliding switch sheet  3  retracts plate spring, piece  24  lid  29  may be actuated a small amount of force. 
     Additionally, switch sheet  3  may be guided in the sliding direction without providing a separate guide member thus further simplifying construction. 
     Having described preferred embodiments of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. 
     Although only a single or few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiment(s) without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus although a nail and screw may not be structural equivalents in that a nail relies entirely on friction between a wooden part and a cylindrical surface whereas a screw&#39;s helical surface positively engages the wooden part, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures.