Abstract:
A keyboard switch includes an improved interlock mechanism that 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. The interlock mechanism converts a rotary motion from a device lid to a linear motion for the switch sheet guided by a slider block slidably retained in a device case.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a keyboard switch suitable for use in a notebook-type personal computer having a lid that closes to cover at least one key top. More particularly, the present invention relates to an improved keyboard switch that allows a cover-closing motion to move the key tops downward and allow the cover to easily close without undue ware. 
     2. Detailed Description of the Related Art 
     It is conventionally known to move key tops downward during a closing motion and accommodate a keyboard switch in a closed notebook-type personal computer. 
     Referring now to FIGS. 12 to  14 , showing a conventional keyboard switch  100  as disclosed in the publication of Japanese Patent No. 2857353, includes a supporting plate  107  for supporting a large number of key tops  102 . Each key top  102  is attached to a cross link  101 . Keyboard switch  100  is included between a lid  115  and an equipment case  109  of a conventional notebook-type personal computer. 
     Cross link  101  includes a first link member  101   a  and a second link member  101   b , each formed generally in the shape of the letter “U”, and being rotatably linked together about an intermediate rotatable fulcrum (not shown). Cross link  101  guides key top  102  during motion in an up-and-down movement. 
     In the operational position shown in FIG. 13, a dome-like rubber elastic portion  114  is disposed below each key top  102  and serves as a return spring, pressing key top  102  upward in response to a key stroke. Elastic portion  114  abuts the bottom surface of a pressure-applying portion  106  formed at the intersection between first and second link members  101   a ,  101   b.    
     Elastic portion  114  is integrally formed on a rubber sheet  104  superimposed on a switch sheet  103 . Switch sheet  103 , is located below elastic portion  114 , and includes an integrally formed switch portion  103   a.  Rubber sheet  104  and switch sheet  103  are both flexible and are superimposed and generally laminated together forming a flexible sheet that is slidable along a guide rail  108  included in supporting plate  107 . Switch sheet  103  and rubber sheet  104  are contactable with a return spring  118  and disposed between their end portions (not shown) and equipment case  109 . The laminated flexible sheet  103  and rubber sheet  104  are loaded by return spring  118  with a force that tends to move them toward the left-hand portion in FIGS. 12 through 14. 
     In the operational position shown in FIGS. 12 and 13, when downward pressure is applied to key top  102  from above, key top  102  is guided by cross link  101  and is thereby moved downward and kept generally horizontal relative to equipment case  109  without being significantly inclined. As a result, pressure-applying portion  106  of key top  102  presses on and deforms elastic portion  114 , so that an ‘ON’ operation of switch portion  103   a  is effected. 
     Equipment case  109  is rotatively coupled to lid  115  and rotates closed to protect key tops  102 . A cam projection  117  projects outward from the inside of lid  115 . Cam projection  117  has a top surface formed as an inclined plane. During a lid  115  closing-motion, the top surface of cam projection  117  presses on a side surface (not shown) of both switch sheet  103  and rubber sheet  104 . As the top surface of cam projection  117  presses on the side surfaces of both switch sheet  103  and rubber sheet  104  the inclined plane exerts a force that acts to counter the spring force supplied by return spring  118 . As a result of this counter-action, both switch sheet  103  and rubber sheet  104  move toward the right-hand side of FIGS. 12 and 13. As a result, when lid  115  is rotatably closed toward equipment case  109 , switch sheet  103  and rubber sheet  104  are slid, in a synchronization with lid  115 , into a retracted position and key tops  102  are lowered toward support plate  107 . 
     During closing, dome-like rubber elastic portion  114  and switch portion  103   a  retract into the lower portion of a housing concave portion  116  formed in key top  102 . Also during closing, an upward projection  104   a , projecting from rubber sheet  104  and located near the lower leg portion of first link member  101   a , contacts first link member  101   a  and forces cross link  101  into a retracted position as rubber sheet  104  slides leftward, as shown in FIG.  14 . Thus, simultaneous with the motion of elastic portion  114  and cross link  101 , key tops  102  move into the retracted position, reduce the overall height of keyboard switch  100 , and allow keyboard switch  100  to fit within equipment case  109 . 
     It should be recognized that, while key top  102  move downward into the retracted position, switch portion  103   a  remains deactivated. It should also be noted, that when key top  102  is in a retracted position, elastic portion  114  maintains an un-compressed state within concave portion  116 , thus reducing the material fatigue and increasing the operational life of elastic portion  114 . 
     During opening, lid  115  is rotated away key tops  102  and cam projection  117  loses contact with switch sheet  103  and rubber sheet  104 . As cam projection  117  loses contact with switch sheet  103  and rubber sheet  104 , return spring  118  forces both switch sheet  103  and rubber sheet  104  leftward into the operation position shown in FIG.  13 . In the operational position, key top  102  is supported by elastic portion  114  through cross link  101 . 
     It should be additionally noted that the above-described action of conventional keyboard switch  100 , shows one possible way to reduce the thickness of the equipment case  109  and hence the overall thickness of a notebook-type personal computer. It should also be noted that in conventional keyboard switch  100 , switch portion  103   a  is not activated during the closing motion and elastic portion  114  is kept in an extended state. 
     Additionally, in the conventional keyboard switch  100 , the inclined plane of cam projection  117  both horizontally and vertically presses on the contact surface of switch sheet  103  and rubber sheet  104 . While the horizontal-pressing motion of cam projection  117  is generally desirable in this device to activate key tops  102 , the vertical- pressing motion subjects switch sheet  103  and rubber sheet  104  to undue stress and fosters the formation of an undesirable warp along the contact surface of both sheets. Consequently, it is very difficult to achieve either a smooth sliding motion as lid  115  rotates relative to equipment case  109  or sufficient durability in switch sheet  103  and rubber sheet  104 . 
     Moreover, while the horizontal-pressing motion of cam projection  117  is generally desirable to activate key tops  102 , the horizontal-pressing motion also subjects switch sheet  103  and rubber sheet  104  to a compressive stress in the sliding direction. This compressive stress fosters the formation of an undesirable warp throughout flexible switch sheet  103  and rubber sheet  104 . A reinforcing lining sheet  121 , made of metal, is applied to the back surface of switch sheet  103  and rubber sheet  104  to counteract the formation of this undesirable warp. Unfortunately, lining sheet  121  increases the overall thickness of keyboard switch  100  which results in an increase in the overall thickness of a notebook-type personal compute and an increase in cost. 
     Furthermore, return spring  118  requires a relatively heavy spring-force to operate switch sheet  103  and rubber sheet  104  between the operational position and the retracted position and creates an increasingly complex construction. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved keyboard switch that offers durability while requiring only moderate physical force during an opening and closing operation. 
     It is another object of the present invention to provide an improved keyboard switch that does not require a return spring and thus retains a simplified configuration. 
     It is another object of the present invention to provide an improved keyboard switch that allows a thin flexible sheet to reciprocate in synchronization with an opening and closing motion of a lid. 
     The present invention relates to a keyboard switch including an improved interlock mechanism that 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. The interlock mechanism converts a rotary motion from a device lid to a linear motion for the switch sheet guided by a slider block slidably retained in a device case. 
     According to an embodiment of the present invention there is provided an a keyboard switch, comprising: a support plate supporting a plurality of keys inside a device case; an interlock moving the keys from a first to a second position; the interlock including a cylindrical cam that rotates about a pivot shaft; the pivot shaft rotatably fixed in a bearing plate for pivotally connecting the cylindrical cam to an equipment case, the cylindrical cam including a radial interlocking plate for pivotally connecting the cylindrical cam to an equipment lid, the cylindrical cam including a cylindrical body, the cylindrical body including a cam grove, a slider having a follower fitting slidably inside the cylindrical cam and movably captured in the cam grove, the slider having a slider body extending away from the cylindrical cam, the slider including a slider block, the slider block extending perpendicularly from the slider body, the slider block slidably engaging a guide grove formed in the equipment case, an rigid angle plate fixedly attached to the slider, a switch sheet fixedly attached to the angle plate allowing the switch sheet to slidably reciprocate with the angle plate, and the interlock causing the switch sheet to slidably reciprocate in response to rotational operation of the lid whereby the interlock converts the rotational motion to a linear motion. 
     According to another embodiment of the present invention there is provided a keyboard switch, further comprising: a short portion, a long portion, and a coupling piece included in the rigid angle, the long portion extending perpendicular to the short portion, the switch sheet fixedly attached between both the short and the long portions, the coupling piece extending perpendicular from the long portion, and the coupling piece fixedly attached to the slider whereby transmitting the linear motion to the switch sheet is accomplished without crimping the switch sheet. 
     According to another embodiment of the present invention there is provided a keyboard switch, further comprising: at least one hole in the long portion, at least one rivet affixing the long portion to a first side of the switch sheet through the hole, a U-shaped portion on the short portion, and the U-shaped portion fixably engaging an orthogonal side of the switch sheet whereby the switch sheet is affixed between the first and second sides. 
     According to another embodiment of the present invention there is provided a keyboard, comprising: at least one keyboard switch in the keyboard, a keyboard cover, means for actuating the at least one keyboard switch to a retracted position in response to closing the keyboard cover, the means for actuating including a coupling piece, the means for actuating further including a cam actuated by the closing to displace the coupling piece, a first guide element affixed to the coupling piece, a second guide element affixed to the keyboard, and the first and second guide elements being effective for guiding displacement of the coupling piece, whereby precise retraction of the at least one keyboard switch is attained when the keyboard cover is closed. 
     According to another embodiment of the present invention there is provided a keyboard, further comprising: a plurality of keyboard switches in the keyboard, and the means for actuating retracting the plurality of keyboard switches to the retracted position in response to closing the keyboard cover. 
     According to another embodiment of the present invention there is provided a keyboard, wherein: the first guide element is a slider block, the slider block extending away from the coupling piece, the slider block being substantially shaped as a parallelepiped having a first and a second side, and the slider block and the second guide element are effective -for guiding displacement of the coupling piece, whereby precise retraction of the plurality of keyboard switches is attained when the keyboard cover is closed. 
     According to another embodiment of the present invention there is provided a keyboard, wherein: the second guide element is guide groove, the guide groove shaped to slidably receive the slider block, the guide grove contacting the first and second side of the slider block, and the slider block sliding in the guide grove in response to closing the keyboard cover whereby precise retraction of the plurality of keyboard switches is attained when the keyboard cover is close. 
     In this construction, the switch sheet is guided along the sliding direction by the supporting projection loosely received in a slit in the switch sheet. This eliminates the need for an extra guiding member. 
     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 perspective view illustrating a notebook-type personal computer according to an embodiment of the present invention. 
     FIG. 2 is an exploded view illustrating an embodiment of the present invention. 
     FIG. 3 is a plan view illustrating the structure of a angle plate and a membrane switch sheet according to an embodiment of the present invention. 
     FIG.  4 (A) is a plan view illustrating an angle plate according to an embodiment of the present invention. 
     FIG.  4 (B) is a plan view illustrating an angle plate according to an embodiment of the present invention. 
     FIG. 5 is a plan view illustrating the keyboard switch according to an embodiment of the present invention. 
     FIG. 6 is an enlarged exploded view illustrating the interlocking mechanisms according to an embodiment of the present invention. 
     FIG. 7 is an enlarged plan view illustrating the interlocking mechanisms according to an embodiment of the present invention. 
     FIG. 8 is a sectional view of a key switch in an operational position according to an embodiment of the present invention. 
     FIG. 9 is a sectional view of a key switch depressed in an operational position according to an embodiment of the present invention. 
     FIG. 10 is an enlarged plan view illustrating the interlocking mechanisms according to an embodiment of the present invention. 
     FIG. 11 is a sectional view of the key switch in a retracted position according to an embodiment of the present invention. 
     FIG. 12 is a partially front view illustrating the structure of a conventional keyboard switch. 
     FIG. 13 is a vertical sectional view illustrating the principal portions of a conventional keyboard switch in an operational position. 
     FIG. 14 is a vertical sectional view illustrating the principal portions of a keyboard switch in a retracted position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, a notebook-type personal computer  30  includes a lid  29  rotatively coupled to an equipment case  14  containing a keyboard switch  1 . Lid  29  is rotatively coupled to equipment case  14  by a cylindrical cam  31  linked to an angle plate contained in the equipment case  14 . Cylindrical cam  31  includes a slider  26  and a cylinder  25  and operates lower keyboard switch  1  from an operational position into a retracted position, into equipment case  14  in response to a lid  29  closing motion, as will be explained. 
     Additionally referring now to FIG. 2, keyboard switch  1  includes a number of a key switches  10  arranged in arrayed and formed on the top surface of a rectangular support plate  18  made of a suitable flexible material such as sheet metal, synthetic resin, or other ceramic materials. 
     Key switch  10  includes a key top  2 , a cross-link  13 , a switch sheet  3  containing a switch portion  3   a , and a support plate  18 . Switch sheet  3  is built as a flexible sheet and slides on support plate  18 , as will be explained. Key top  2  is formed as a molded part from a synthetic resin material such as ABS resin. Key top  2 , has a pair of U-shaped bearing portions  6  formed integrally on a rear-end portion of a bottom surface of key top  2 . Key top  2  also has a pair of guide bearing portions  5  formed integrally on a front-end portion of a bottom surface of key top  2 . 
     Bearing portions  6  rotatively attach key top  2  to cross-link  13 , and guide bearing portions  5  both slidably and rotatively attach key top  2  to cross-link  13 , as will be explained. 
     Cross-link  13  includes an inner link  7  and an outer link  8 . Inner link  7  includes a pair of integral arm portions  7   a , a pair of pivot shafts  7   b  pivotably linked to bearing portions  6 , and a pair of slidable projections  7   c . Outer link  8  includes a pair of integral arm portions  8 a, a pair of slidable projections  8   b  linked to guide bearing portions  5 , and a pair of pivot shafts  8   c . Inner link  7  and outer link  8  are rotatable together and intersect at the center of arm portions  7   a ,  8   a . It is important to note, that both inner link  7  and outer link  8  have one end built as a hinged portion ( 7   b  and  8   c ) and one end built as a slidable-and-hinged moving end portion ( 7   c  and  8   b ). 
     Inner link  7  is rotatably and slidably supported on a first side by slidable projection  7   c  formed as a projection on the side of arm portion  7   a  and are slidably and rotatively retained in an elongated slot  11   a , piercingly formed in the front-side portion of a pair of front supporting projections  11 , as will be explained. Arm portions  7   a  extend beyond slidable projections  7   c  into a pair of pawl pieces  15 , as will be explained. Inner link  7  is rotatably supported on a second end by pivot shafts  7   b  received in bearing portions  6 . Pawl pieces  15  are contiguously formed from arm portions  7   a  in an arc-shape and positioned obliquely below sliding parts  7   c.    
     Outer link  8  is rotatably and slidably supported on a first end by slidable projection  8   b  protruding from coupling plate  22  formed between arm portions  8   a , and slidably and rotatively retained in guide bearing portions  5 . Outer link  8  is rotatably supported on a second end by pivot shafts  8   c , protruding from arm portion  8   a  and loosely received in a pair of circular holes  12   a  piercingly formed in a pair of rear supporting projections  12 , as will be explained. 
     Cross link  13  attaches key top  2  to a support plate  18  by front supporting projections  11  and rear supporting projections  12  that are cut and raised from support plate  18 . When front and rear supporting projections  11 ,  12  are cut and raised from support plate  18 , a pair of corresponding front and rear cut-out openings  11   b ,  12   b  remain. In this manner, key top  2  is linked by cross link  13  to support plate  18  so that during actuation of key top  2 , key top  2  is maintained in a generally horizontal plane relative to support plate  18 . 
     Outer link  8  includes a strip-like spring piece  24 , formed integrally with coupling plate  22 , and extending obliquely downwards away from key top  2 . Spring piece  24  has a free end formed opposite coupling plate  22 . On the free end, is formed an abutting portion  24   a , molded to protrude in a conical form and shaped to come into elastic contact with switch portion  3   a  of membrane switch sheet  3 , as will be explained. 
     Membrane sheet  3  is composed of an upper plastic sheet, a lower plastic sheet, and an insulating spacer sheet all superimposed together. The upper plastic sheet, has a moving contact and a route pattern therefor is printed on its back surface. The lower sheet, has a fixed electrode and a route pattern therefor printed on its top surface. The insulating spacer sheet is interposed between the upper and lower plastic sheets. The sheets are bonded together through their interfaces with adhesive and formed into rectangular, three-layer laminated flexible sheets. The insulating spacer sheet has a circular opening piercingly formed in a position on its surface where the moving and fixed contacts of the upper and lower plastic sheets are printed. Through the circular opening, the moving and fixed contacts face each other with a minimum interval secured therebetween to form switch portion  3   a.    
     On membrane switch sheet  3 , is a dish-shaped spring  4  [hereinafter called dish spring  4 ] formed in the shape of a disk and made from an elastic metal plate. Dish spring  4  has an outer rim periphery fixed to switch sheet  3  above switch portion  3   a.    
     Switch sheet  3  is superimposed on and aligned along the length direction of support plate  18 . Switch sheet  3  is reciprocally slidable along support plate  18  in its length direction. Switch sheet  3  has a pair of guide slits  19  formed to slidably receive front supporting projections  11  and a second pair of guide slits  19  formed to receive rear support projections  12 . Guide slits  19  are formed along the length direction of support plate  18 , and enable switch sheet  3  to slide relative to support plate  18  without interference from front and rear supporting projections  11  and  12 . Guide slits  19  are slightly wider than the thickness of front and rear supporting projections  11  and  12 , and allow switch sheet  3  to be guided by supporting projections  11  and  12  and thereby freely slide along support plate  18 . 
     A pair of engagement openings  16  extend from the pair of front-side guide slits  19 . Each engagement opening  16  has a corresponding rear edge  16   a.  Engagement openings  16  are formed in switch sheet  3  to receive pawl pieces  15  extending from inner link arm portions  7   a . During retraction of key switch  10 , rear edges  16   a  abut pawl pieces  15  and exert force on arm portions  7   a  of cross link  13  thereby bringing key switch  10  into a retracted position, as will be further explained. During operation of key switch  10 , pawl pieces  15  extend into front cut-out openings  11   b  thereby allowing key switch  10  to extend into the operational position, as ill be further explained. 
     A circular opening  17  is formed on switch sheet  3  between the rear-side guide slits  19  and beyond dish spring  4 . Circular opening  17  accommodates abutting portion  24   a  of spring piece  24  as switch sheet  3  slides into the retracted position. As a result, key switch  10  is able to help achieve a narrow retracted position without exerting upward pressure on key top  2  through cross link  13 . 
     Additionally referring now to FIGS. 3,  4 , and  5 , an angle plate  27  is affixed to switch sheet  3  along its upper edge and right edge relative to FIG.  3 . Angle plate  27  is built as a frame-shaped linked portion from metal generally having an inverted L-shape. Angle plate  27  has a short-side portion  27   a , a long-side portion  27   b , and a coupling piece  27   c  extending from angle plate  27 . Short side portion  27   a  has an edge folded back upon itself in a general U-shape to enable it to affix to the right edge of switch sheet  3 . Long side portion  27   b  is affixed to the upper edge of switch sheet by a rivet or other means passing through multiple holes formed in long side  27   b . It should be understood, that angle plate  27  may be fixed to switch sheet  3  in multiple ways as long as a left-right motion of angle plate  27  slides switch sheet  3  in a corresponding manner. It should be further understood that while switch sheet  3  is a flexible sheet, since its upper and right sides are affixed to rigid angle plate  27 , switch sheet  3  is not generally subject to local stresses during sliding movement, and thus the risk of warp occurring on switch sheet  3  is minimized. 
     Coupling piece  27  is coupled to a slider  26  attached to a cylindrical cam  31 , as will be described. Slider  26  transmits the action of cylinder cam  31  to coupling piece  27 . During actuation, angle plate  27  slides switch sheet  3  to the left and right in FIG. 3, thereby sliding switch sheet  3  in a corresponding direction relative to support plate  18 . As a result, cross link  13  and key top  2  are actuated and move key switch  10  between the raised operational position and the lowered retracted position. 
     An interlocking mechanism is coupled between lid  29  and equipment case  14  and transmits the rotary opening and closing operation of lid  29  through cylinder cam  31  into rectilinear reciprocating motion of angle plat  27  to switch sheet  3 . Cylinder cam  31  includes a cylinder  25  and slider  26 . Cylinder  25  rotates around a pivot shaft  25   c  (later shown) parallel to the direction of the length of equipment case  14 . Slider  26  is loosely fitted in cylinder  25  and has a follower  26   a  protruding therefrom to engage a cam grove  25   b  formed in cylinder  25 . 
     Additionally referring now to FIGS. 6 and 7, the cylinder cam  31  of the interlocking mechanism includes cylinder  25  containing a cylindrical body  25   a  having cam grove  25   b  formed through the wall of cylindrical body  25   a . Cylinder  25  is rotationally attached to pivot shaft  25   c . Pivot shaft  25   c  is normally made of metal and is inserted through a bearing plate  32  attached to and extending upwardly from equipment case  14 . As a result, cylinder  25  is rotationally supported on bearing plate  32  and affixed to equipment case  14 . An interlocking plate  33  is fixed on a first end to the periphery of an intermediate portion of pivot shaft  25   c . Interlocking plate  33  is fixed on a second end to the rear side of lid  29  so that the rotation of lid  29  is transmitted to pivot shaft  25   c . It is to be understood that interlocking plate  33  may be fixed to lid  29  in multiple ways to transmit the rotary motion of the lid to cylinder  25 . 
     Slider  26  includes follower  26   a , a slider body  26   b , and a slider block  26   c.  Slider body  26   b  has a generally cylindrical shape so as to be loosely received inside cylinder  25 . Follower  26   a  is generally shaped as a circular pin or bulged portion and engages cam grove  25   b  of cylinder  25  to transmit the motion of cylinder  25  to slider  26 . Slider block  26   c  is shaped generally as a parallelepiped and is affixed to a bottom portion of slider body  26   b  through coupling piece  27   c  of angle plate  27  generally by means of a screw or threaded bolt. As a result, slider block  26   c  fixes coupling plate  27  to slider  26  and cylinder  25 . 
     A guide grove  34  is concavely formed in a top surface of equipment case  14  in a length direction of equipment case  14  parallel to the axial direction of pivot shaft  25   c  of cylinder  25 . Guide grove  34  loosely receives slider block  26   c , and reciprocally guides slider block  26   c  in the length direction of equipment case  14 , parallel to the axial direction of cylinder  25   c.    
     As a result, when lid  29  is rotated, slider  26  is moved reciprocally and rectilinearly along the direction of the length of equipment case  14 . In synchronization with the movement of slider  26 , switch sheet  3  slides reciprocally with angle plate  27  between the retracted position and the operational position. 
     In the operational position, with lid  29  in an open state, slider body  26   b  of slider  26  is rotationally accommodated inside cylindrical body  25   a  of cylinder  25 , and switch sheet  3  is kept in the operational position. In the retracted position, with lid  29  in a closed state, slider body  26  is directed outward from cylindrical body  25  also forcing angle plate  27  guided by slider block  26   c  away from cylinder  25 . 
     Additionally referring now to FIG. 8, key switch  10  is shown in the operational position in a stand-by state, without downward pressure on key top  2 . Dish spring  4  is located above switch portion  3   a  to abut against abutting portion  24   a  under adequate resilient force to project cross arms  13  upward and bring key top  2  to its highest position. As a result, abutting portion  24   a  of spring piece  24  does not depress dish spring  4  and a switch portion  3   a  of switch sheet  3  is not activated and an ‘OFF’ operation of switch portion  3   a  occurs. 
     Additionally referring now to FIG. 9, pressure is applied to key switch  10  the operational position, and key top  2  is pressed downward to an activated-state. As key top  2  is moved downward, cross link  13  keeps key top  2  generally horizontal to support plate  18 , and force is transmitted through outer link  8  and coupling plate  22  to spring piece  24 . As force is applied to spring piece  24 , abutting portion  24   a  presses on and deforms dish spring  4 . As dish spring  4  deforms switch portion  3   a  of switch sheet  3  is activated and key switch  10  achieves the activated-state and an ‘ON’ operation of switch portion  3   a  occurs. Upon release of the downward pressure, dish spring  4  elastically returns to its original position, deactivates switch portion  3   a , and elastically presses spring piece  24  and cross link  13  upward, returning key top  2  to its operational position. 
     Additionally referring now to FIGS. 10 and 11, cylinder cam  31  is rotatably attached to interlocking plate  33  shown here without cover  29 . FIG. 10 shows the interlocking mechanism for keyboard switch  1  in a retracted state with slider  26  projected axially outward(away) from cylinder  25  by a sliding interaction between follower  26   a  and cam grove  25   b . As slider  26  is projected axially outward from cylinder  25 , cylinder body  26   b  which is attached to angle plate  27  and guided by slider block  26   c  sliding in guide grove  34  along the length of support plate  18 . As angle plate  27  slides, switch sheet  3  is guided by and slides past front and rear support projections  11 ,  12 , to the left in FIG.  11 . 
     As switch sheet  3  slides to the retracted position, rear edges  16   a  of engagement openings  16 , engage pawl pieces  15  and rotate arm portions  7   a  of inner link  7  in a clockwise about slidable projections  7   c . As cross link  13  retracts. slidable projections  7   c  both slide and rotate within elongated slots  11   a  and slidable projections  8   b  both slide and rotate within guide bearing portions  5 . As a result, cross link  13  moves into a retracted position. 
     As cross link  13  further slides to the retracted position, abutting portion  24   a  of spring piece  24  slides from dish spring  4  into retracting opening  17  of switch sheet  3 . Further, as switch sheet  3  slides leftward in FIG. 11, switch portion  3   a  protected by dish spring  4  also slide leftward. As a result, dish portion  4  is not elastically deformed and fatigue and plastic deformation is minimized. As a further result, switch sheet  3   a  is protected from unintended activation and damage. 
     As lid  29 , and interlocking plate  33  are rotated open to allow active use of keyboard switch  1 , slider  26  moves inward toward cylinder  25  to an operational position. Through the opening motion of lid  29  and locking plate  33 , the rotational motion is transferred by the interlocking mechanism with angle plate  27  to slide switch sheet  3  to the operational position (to right in FIG.  11 ). Thus, switch sheet  3 , in synchronization with the opening movement slides from the retracted position to the operational position and eliminates the need for an additional spring mechanism to provide a shifting force. 
     Further, as switch sheet  3  slides, rear edges  16   a  no longer contact pawl pieces  15  and spring piece  24  is slid from retracting opening  17 . As a result, abutting portions  24   a  elastically contact dish springs  4  and project cross links  13  upward to restore key tops  2  and keyboard switch  1  to the operational position. 
     The present invention provides multiple benefits. First, it should be appreciated that during the above-described reciprocating movement, membrane switch sheet  3  is not subjected to undesirable warp, nonlinear stress, or bending motions. As a result, each switch portion  3   a  enjoys extended life and can be made thinner and lighter thus providing a lighter overall product. 
     Second, it should be appreciated that front and rear side supporting projections  11 ,  12  provide guidance to switch sheet in addition to that provided by angle plate  27 . As a result, switch sheet  3  is able to slide smoothly and securely along supporting plate  18 . 
     Third, it should be appreciated that while angle plate  27  currently attaches to switch sheet  3  on the upper and right sides, all sides or any combination of sides may be connected to the interlocking mechanism to effect the reciprocating sliding motion. As a result, multiple options are provided to manufacturers and customers in designing adaptively shaped equipment cases  14 . 
     Fourth, it should be appreciated that when keyboard switch  1  is accommodated inside device case  14 , key tops  2  may be kept in a lowered state without the need for an additional complicated retaining structure. According, the complete notebook-type personal computer  30  may be constructed in a lighter and cheaper manner. Additionally, since key tops  2  retract, notebook-type personal computer  30  may be made thinner and lighter and without the risk of damage to either a viewing screen (usually a liquid-crystal display) or key tops  2 . 
     Fifth, it should be appreciated that using the interlocking mechanism to change rotational motion into linear motion no additional return spring is necessary to return key tops  2  to their fully raised operational position. As a result, notebook-type personal computers  30  may be made more simply and less expensively with a lower risk of stress or elastic failure. 
     Sixth, it should be appreciated that since spring pieces  24  are removed from elastic contact with dish spring  4  or switch portion  3   a , and retracted into retracting opening  17 , the risk of fatigue or plastic failure of spring piece  24 , dish spring  4  and switch portion  3   a  are reduced. Accordingly, equipment reliability and customer satisfaction are increased. 
     It should be also noted that various changes and modifications may be made in the construction of each component constituting the key switch  10  without departing from the spirit of the present invention. For example, here, the plate spring piece  24  for restoring the key top  2  to its original position also serves as an actuator for driving the switch portion  3   a  to operate. However, it is also possible to provide, apart from the plate spring piece  24  acting as a return spring, an actuator for applying downward pressure to the switch portion  3   a  in the key top  2  or in the cross link  13 . 
     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.