Abstract:
The first example of a keyboard apparatus of the invention intends to prevent the inclination and shake of a key button by forming retaining claws so as to project downwardly at locations near the corners of the quadrangular key button. The second example intends to prevent to shake of a small-sized key button by arranging the retaining claws formed for the small key button on a diagonal line of the key button, thereby elongating the distance between the retaining claws. The third example intends to automatically adjust the center of the position of the key button by forming the portion to restrict the top dead point of a key button so as to have almost a complementary zigzag shape.

Description:
This application is a continuation of application Ser. No. 073,882, filed July 16, 1987, now abandoned, which was a continuation of application Ser. No. 890,541, filed July 30, 1986, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a keyboard apparatus which can prevent unstable factors such as gradient, shake, rotation, and the like of quadrangular key buttons. 
     2. Related background art 
     A conventional keyboard apparatus is shown in FIGS. 1 to 23. First, a first conventional structure will be described with reference to FIGS. 1 to 7. 
     FIGS. 1 and 2 show an electronic desk calculator (hereinafter, abbreviated as an electronic calculator) as an example of an electronic equipment in which a keyboard apparatus is used. 
     An electronic calculator 101 has an upper casing 102 and a lower casing 103. The front half portion of the upper surface of the upper casing 102 (panel) serves as a keyboard section 104. The keyboard section 104 consists of a number of key buttons 105. A solar battery 106 and a display device 107 are also provided. 
     As shown in FIG. 1, a keyboard such as keyboard section 104 is filled with a number of key buttons 105 is called a full keyboard type keyboard. 
     As well as such a full keyboard type keyboard, there is also a keyboard of the type having a plurality of key buttons as shown in FIG. 2. In many cases, the keyboard as shown in FIG. 2 has a structure such that the respective key buttons are inserted from the upper side of the upper casing 102. 
     In the case of such a structure, the key buttons need to freely descend and ascend and at the same time, a slip-out preventing structure of the key button is also necessary. 
     FIGS. 3 to 5 show the first example of the key buttons provided with such a slip-out preventing mechanism. 
     Namely, the key button 105 is formed like A square plate. a prismatic guide axis 108 is projected from the lower surface of the key button 105. The guide axis 108 is slidably inserted into an opening portion 109 formed in the bottom surface of a recess portion 110 adapted to accommodate the key button of the upper casing 102. 
     On the other hand, retaining claws 111 and 112 are projected from the bottom surface of the key button 105 at the end portions substantially along a diagonal of the key button. Hooks 111a and 112a are outwardly projected from the lower end portions of the retaining claws 111 and 112. 
     The claws 111 and 112 are elastically deformed and inserted into guide holes 113 formed in the bottom surface of the recess portion 110 as so to sandwich the opening portion 109. 
     When the hooks 111a and 112a pass through the guide holes 113, the upper surfaces of those hooks are retained by notched portions 102a formed on the side of the lower surface of the upper casing 102 as shown in FIGS. 4 and 5, respectively. 
     A printed circuit board 114 is arranged on the side of the bottom surface of the upper casing 102 as shown in FIGS. 4 and 5. A key pattern 115 is formed on the printed circuit board 114 so as to face the guide axis 108. 
     An elastic rubber plate 116 is disposed on the board 114. The rubber plate 116 is formed with an expanded portion 116a having a trapezoidal cross section in correspondence to the guide axis 108. A conductive rubber 117 is fixed to the lower surface of the expanded portion 116a. 
     In the keyboard apparatus having the structure mentioned above, when none of the key buttons 105 is pressed, each key button 105 is upwardly pressed due to the elastic force of the expanded portion 116a so that the conductive rubber 117 is apart from the key pattern 115. 
     On the contrary, when the key button 105 is pressed, the expanded portion 116a is elastically deformed, so that the conductive rubber 117 comes into contact with the key pattern 115 and a key signal can be input. 
     When using the above-mentioned keyboard structure, for instance, in order to smoothly descend and ascend along the guide axis 108, clearance is required between the opening portion 109 and the peripheral surface of the guide axis 106. 
     When such a key button 105 is pressed, if it is pressed at either one of the positions corresponding to the retaining claws 111 and 112 as indicated at reference numerals 111b and 112b in FIG. 3, a slight force f will be applied to this position as shown in FIG. 6. However, in this case, an amount of inclination of the key button 105 will be small since the retaining claws 111 and 112 also serve as guide members. On the contrary, as shown at reference characters X and Y in FIG. 3, if the force f is applied to either one of the positions where the retaining claws 111 and 112 are not formed, the opposite side on the diagonal line will be greatly lifted up. 
     Thus, as shown in FIG. 7, there is the drawback such that the key button 105 is greatly inclined and shaken. 
     A second conventional structure will now be described with reference to FIGS. 8 to 14. 
     FIGS. 8 to 10 show a second example of key buttons equipped with a slip-out preventing mechanism as a modified form of FIGS. 3 to 5 mentioned above. 
     Namely, a key button 205 is formed like a square plate. A prismatic guide axis 208 is projected from the lower surface of the key button 205. The guide axis 208 is slidably inserted into an opening portion 209 formed in the bottom surface of a recess portion 210 adapted to accommodate the key button of the upper casing 202. 
     In addition, retaining claws 211 and 212 project from the bottom surface of the key button 205 at the edge portions substantially along a diagonal of the key button. Hooks 211a and 212a outwardly project from the lower end portions of the retaining claws 211 and 212. 
     The claws 211 and 212 are elastically deformed and inserted into guide holes 213 formed in the bottom surface of the recess portion 210 so as to sandwich the opening portion 209. 
     When the hooks 211a and 212a pass through the guide holes 213, the upper surfaces of the hooks are retained by notched portions 202a formed on the side of the lower surface of the upper casing 202 (panel) as shown in FIGS. 9 and 10, respectively. 
     A printed circuit board 214 is arranged on the side of the bottom surface of the upper casing 202 as shown in FIGS. 9 and 10.A key pattern 215 is formed on the printed circuit board 214 so as to face the guide axis 208. 
     On the other hand, an elastic rubber plate 216 is disposed over the board 214. The rubber plate 216 is formed with an expanded portion 216a having a trapezoidal cross section in correspondence to the guide axis 208. A conductive rubber 217 is fixed to the lower surface of the expanded portion 216a. 
     In the keyboard apparatus having the structure mentioned above, when none of the key buttons 205 is pressed, each key button 205 is upwardly pressed due to the elastic force of the expanded portion 216a so that the conductive rubber 27 is away from the key pattern 215. 
     On the contrary, when the key button 205 is pressed, the expanded portion 216a is elastically deformed, so that the conductive rubber 217 comes into contact with the key pattern 215 and a key signal can be input. 
     When using the above-mentioned keyboard structure, for instance, in order to smoothly descend and ascend along the guide axis 208, a clearance is required between the opening portion 209 and the peripheral surface of the guide axis 206. 
     Therefore, if a slight force f is applied to one end of the key button 205 as shown in FIG. 11, a rotational motion will occur in the key button 205 around the contact portion between the upper surface of the notched portion 202a and one end 212b of the hook 212a as a rotational center. 
     Thus, when the right end of the key button 205 descends by a distance α, the left end is contrarily lifted up by only a distance β as shown in FIG. 11. 
     In the case shown in FIG. 11, there is the relation of α&gt;β since the hook 212a is located at nearly the intermediate position between the guide axis 208 and the edge of the key button 205. 
     On the other hand, when the hook 212a is located near the side of the guide axis 208 as shown in FIG. 12, when the right end side of the key button descends by only the distance α, the left end is lifted up by a distance γ, so that there is the relation of γ&gt;β. 
     In such a case, the key button will also greatly shake. 
     Therefore, to prevent such a shake, there has been proposed the structure in which the hook 212a is formed at the maximum distance away from the guide axis 208 as shown in FIGS. 13 and 14. 
     When such a structure is used, even if the force f is applied to the right end side of the key button and this side accordingly descends by a distance α as shown in FIG. 13, the portion at a left end A won&#39;t be lifted up, so that the shaking motion of the key button will be reduced. 
     However, electronic equipment provided with the keyboard has been more and more miniaturized and both the keyboard and the key buttons have also been miniaturized in association with it. Thus, even if the hook portion is formed at the maximum distance away from the guide axis, the effect to reduce the shaking motion of the key button will be small. 
     There is also the drawback such that an increase in size of the button obstructs the miniaturization of the whole keyboard apparatus. 
     The third conventional structure will now be described with reference to FIGS. 15 to 23. 
     Such a conventional apparatus has the structure such that a part (e.g., 301a in FIG. 15) of the outer periphery of the key button, an outer peripheral surface (e.g., 307a in FIG. 17) of the axial portion formed integrally with the key button, or an outer peripheral surface (e.g., FIG. 21) of a slide part of a key button unit integrally formed from a plurality of members can slide with a part of an inner peripheral surface of an opening portion of a supporting member (a part of a casing is commonly used as this supporting member) which faces this outer peripheral slide surface. The position in the lateral direction in the opening portion of the supporting member of the key button is controlled due to each of those slide surfaces. 
     FIGS. 15 to 23 illustrate different practical conventional examples, respectively. 
     In the example shown in FIGS. 15 and 16, each side surface of a key button 301 serves as the slide surface 301a adapted to be slidable between the key button 301 and the supporting member. A flange 301b, also serving as a stopper to determine the top dead point of the key button, is formed on the lower end of the key button 301. 
     A supporting member (panel) 302 is provided as part of the casing. An inner surface of an opening portion into which the key button 301 is inserted functions as a sliding surface 302a of the key button. A surface 302b on the lower side of the peripheral surface of the opening portion is the surface to determine the top dead point of the key button. 
     An elastic member 303 consisting of flexible rubber or the like is arranged under the key button, thereby lifting up the key button. A conductive member 303a is integrally formed on the lower surface of the head portion of the elastic member 303. 
     A key pattern 305 is formed on a base plate 304. 
     In the above structure, the sliding clearance of dimension &#34;a&#34; is required between the slide surface 301a of the key button and the sliding surface 302a of the supporting member. 
     FIGS. 17 to 19 show another conventional example of a unit structure. Reference numeral 306 denotes a key button and 307 indicates a slide part pressure inserted into the key button 306. The side surface of the slide part 307 serves as the slide surface 307a. 
     As shown in the enlargement in FIG. 18, a projecting portion 307b having a right-angled triangular cross section is formed in the lower end portion on the outside of the slide surface 307a. The upper surface of the projecting portion 307b functions as an abutting surface of the portion to determine the top point of the slide part 307 against the supporting member. 
     Numeral 308 denotes a supporting member, 308a is a slide surface of the supporting member 308, and 308b is a supporting member surface to decide the top dead point of the slide part 307. 
     In addition, numeral 309 denotes a spring to lift up the key button unit and make the lower flexible base plate operative; 310 is a flexible base plate having a pattern 314 on the back side surface; 311 is a flexible base plate having a pattern 315 on the front side surface; 312 is a spacer interposed between the flexible base plates 310 and 311; 313 is a reinforcing plate to support the flexible base plates; and 314 and 315 are the key patterns. 
     When using the above-mentioned structure, a clearance &#34;b&#34; which provides a vertical slide motion is required between the slide surface 307a of the slide part of the key button unit and the slide surface 308a of the supporting member. 
     In the example shown in FIGS. 20 and 21, numeral 316 denotes a key button; 316a is a key button slide surface; and 317 is a side wall formed integrally with the key button 316 and serving as a slide surface. The outside of the lower end of the side wall 317 is formed with a projection 317a which determines the top dead point of the key button. 
     Numeral 318 denotes a supporting member and a cylindrical body 318a adapted to guide the slide surface 316a is formed as part of the supporting member 318. The inner peripheral surface of the supporting member 318 functions as a slide surface. 
     Numeral 318b denotes a supporting member surface to determine the top dead point of the key button 316; 319 is a flexible rubber to lift up the key button; 320 is a conductive member formed integrally with the flexible rubber 319; 321 is a base plate; and 322 is a key pattern section formed on the base plate 321. 
     When such a structure is used, a clearance of a dimension &#34;c&#34; is necessarily formed between the slide surface 316a of the key button and the slide surface 318a of the supporting member. 
     As described in the foregoing three conventional examples, a clearance is necessarily required between the slide surface of the key button and the slide surface of the supporting member and a shaking motion occurs due to this clearance in the conventional examples. 
     Thus, inclination, rotation, or eccentricity of a key button as shown in FIGS. 22 and 23 inevitably occurs. Therefore, there is the large drawback from the viewpoints of external appearance and quality. 
     SUMMARY OF THE INVENTION 
     It is the first object of the present invention to prevent the inclination and shake of the key button. 
     A second object of the invention is to provide a small-size key button in which rotation and shake are less likely to occur. 
     A third object of the invention is to automatically adjust the central position of a key button at the top dead point of the key button. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 to 7, 8 to 14, and 15 to 23 show the first, second, and third conventional structures, respectively. First, in the conventional structure: 
     FIGS. 1 and 2 are perspective views of an electronic calculator; 
     FIG. 3 is an exploded perspective view of the main part; 
     FIG. 4 is a cross sectional view taken along the line 4--4 in FIG. 3; 
     FIG. 5 is a cross sectional view taken along the line 5--5 in FIG. 3; and 
     FIGS. 6 and 7 are explanatory diagrams for explaining a shaking state. 
     In the second conventional structure; 
     FIG. 8 is an exploded perspective view of the main part; 
     FIG. 9 is a cross sectional view taken along the line 9--9 in FIG. 8; 
     FIG. 10 is a cross sectional view taken along the line 10--10 in FIG. 8; 
     FIGS. 11 to 13 are explanatory diagrams for explaining the position of a retaining claw and a shaking state of a key button; and 
     FIG. 14 is a perspective view of the key button. 
     Further, in the third conventional structure: 
     FIGS. 15 and 16 are views perspective view of a key top portion with a part cut away and a cross sectional view of a state in which the key top portion is actually installed for explaining the third example of the conventional structure; 
     FIGS. 17 to 19 are diagrams for explaining another example of the conventional structure; 
     FIG. 17 is a perspective view of a key button portion with a part cut away; 
     FIG. 18 is a perspective view of an engaging portion of a key button; 
     FIG. 19 is a cross sectional view showing an installed state; 
     FIGS. 20 and 21 are perspective views of a key button portion with a part cut away and a cross sectional view of an installed state for explaining further another conventional embodiment; and 
     FIGS. 22 and 23 are explanatory diagrams for explaining conventional drawbacks. 
     Next, FIGS. 24 to 34 show structures according to the present invention, in which: 
     FIGS. 24 and 25 are explained perspective views of the main parts for explaining the first and second embodiments of the present invention; 
     FIGS. 26, 27 A and 27B are diagrams for explaining the third embodiment of the invention; 
     FIG. 26 is a plan view of an electronic calculator; 
     FIGS. 27A and 27B are plan views of a key button; 
     FIG. 28 is a perspective view of a key button; FIG. 29 is a cross sectional view of a composite switch assembly of an installed for explaining the fourth embodiment of the invention; 
     FIGS. 30 and 31 are perspective views of key buttons for explaining the fifth and sixth embodiments of the invention, respectively; and 
     FIGS. 32 to 34 are cross sectional views for explaining the key button operation. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The first and second embodiments according to the present invention use the structure such that retaining claws are formed near the respective corners of each of a number of key buttons in order to solve the problems in the first conventional structure mentioned above. 
     With such a structure, the retaining claws respectively provided near the corners of each quadrangular key button function as guide members. Thus, even if any portion on the upper surface of the key button is pressed as well, the key button will be depressed without shaking. 
     The invention will now be described in detail hereinbelow with respect to the embodiments shown in the diagrams. 
     FIG. 24 is a diagram for explaining the first embodiment of the invention, in which the same or corresponding parts and components as those shown in FIGS. 1 to 7 are designated by the same reference numerals and their descriptions are omitted. 
     In this embodiment, retaining claws 118 and 119 are also projected at the corners indicated at reference characters X and Y of the key button 105 shown in FIG. 3. 
     Therefore, the key button 105 has four retaining claws 111, 112, 118 and 119. 
     The claws 118 and 119 are also formed with hooks 118a and 119a, respectively. 
     In addition to the guide holes 113 adapted to receive the retaining claws 111 and 112, guide holes 120 into which the retaining claws 118 and 119 can be inserted are formed in the upper casing 102. 
     In the embodiment shown in FIG. 24, the hook of each of those retaining claws outwardly projected from each side of the quadrangular key button 105. 
     In this embodiment, since the retaining claws are respectively formed at the corners of the key button as mentioned above, these claws serve as guide members. Therefore, even if any position of the upper surface of the key button 105 is pressed, the key button can descend and ascend without greatly inclining or shaking. 
     FIG. 25 is a diagram for explaining the second embodiment of the invention. In this embodiment, a pair of retaining claws 121 and 122 and another pair of retaining claws 123 and 124 are formed along the right and left sides of and near the corners of the key button 105, respectively. 
     The respective retaining claws are formed with corresponding hooks 121a to 124a so as to face outside. Guide holes 125 into which the retaining claws are respectively inserted are formed in the recess portion 110 of the upper casing 102. 
     When the foregoing structure is used as well, each retaining claw functions as a guide member, so that the key button 105 will not shake. 
     As will be obviously understood from the above description, according to the first and second embodiments of the invention, a structure is used such that the retaining claw is formed near each corner of the key button having a quadrangular shape. Thus, these retaining claws serve as guide members when the key button descends and ascends, thereby preventing the key button from inclining and shaking. 
     Next, to solve the problem in the second conventional structure mentioned above, the third embodiment of the invention uses the following structure. Namely, among a number of key buttons arranged adjacently, excluding the key buttons locating at both of the right and left end portions, each of the other key buttons is formed like a parallelogram and at the same time, retaining claws are projected from the lower surface of the corners in the direction of a long diagonal line of each key button. 
     By use of the above-mentioned structure, a length of one diagonal line of the key button can be set to be long. By providing the retaining claws at both ends in the direction of this diagonal line, the distance between the retaining claw and the guide axis can be increased. This is equivalent to a substantial enlargement of the key button, so that the shake of the key button can be remarkably reduced. 
     The invention will now be described in detail hereinbelow with reference to other embodiments shown in the drawings. 
     FIGS. 26, 27A, and 27B are diagrams for explaining the third embodiment of the present invention, in which the same or corresponding parts and components as those shown in FIGS. 8 to 14 are designated by the same reference numerals and their descriptions are omitted. 
     In this embodiment, key buttons constituting a keyboard section 204 are classified into key buttons 205a locating at both right and left ends and key buttons 205b locating at the central portion. Each key button 205b located at the central portion is formed in the shape of a parallelogram. Each of the key buttons 205a located at the right and left ends has a trapezoidal shape. 
     By use of the above-mentioned structure, as indicated at reference characters L 1  and L 2  in FIGS. 27A and 27B, a length of one diagonal line can be set to be fairly longer than that of the conventional key button 205. 
     Therefore, by providing the retaining claws 211 and 212 at the positions corresponding to both ends of each of the long diagonal lines L 1  and L 2 , each retaining claw can be arranged at the maximum distance away from the guide axis 208. 
     Therefore, the shake of key button is remarkably reduced. 
     In addition, as will be obvious from FIG. 26 as well, even if the shape of key button is deformed, the whole area of the keyboard section 204 won&#39;t change, so that the miniaturization of the electronic equipment of electronic calculators and the like will not be obstructed. 
     As will be apparent from the above description, according to this embodiment, among the key buttons constituting the keyboard, each of the key buttons locating at both right and left ends has almost a trapezoidal shape and each of the key buttons locating between both ends has the shape of a parallelogram. Thus, the retaining claws can be formed at the positions corresponding to both ends of a long diagonal line of each of these key buttons. The distance between the retaining claws can be elongated. The distance between the retaining claw and the guide axis can be also elongated. The shake of key button can be eliminated. The miniaturization of electronic equipment is not be obstructed. 
     Further, to solve the prblems in the third conventional structure mentioned above, the fourth to sixth embodiments of the invention use a structure such that the engaging portion which determines the top dead point of the key button is formed in a zigzag shape having substantially complementary structure at a plurality of positions between the key button and the supporting member. 
     By use of the above-mentioned structure, when the convex (or mountain-like) and concave (or valley-like) portions having mutually nearly complementary shapes come into engagement with each other, an automatic center adjusting force which horizontally moves the key button due to the horizontal component of force is provided, so that the key button is positively reoriented at an accurate location at its top dead point so as to have the proper position. 
     The fourth embodiment of the invention will now be described with reference to FIGS. 28 and 29. In the diagrams, numeral 323 denotes a key button. Each side surface of the key button serves as a slide surface 323a with the supporting member of the key button. By providing inclined surfaces 324 and 325 for the engaging surfaces of the key button with the supporting member, a convex portion which protrudes upwardly is formed at a total of four locations. 
     FIG. 29 is a cross sectional view of a key button similar to that depicted in FIG. 28 and shows an installed state of key buttons. In FIG. 29, numeral 326 denotes a supporting member; 327 and 327a are flexible portions formed of rubber or the like; and 328 is a base plate. Flexible portions 327 and 327a include a pair of conductive members which contact each other and transmit a key depression signal when key button 323 is depressed. The engaging portion of the supporting member 326 with the key button is formed with a recess portion 326a like a valley having a shape which is complementary to the convex portion on the key button side. 
     By use of such a structure, the position of the top dead point of the key button is not determined by the slide surface 323a of the key button and the slide surface of the supporting member adapted to contact it, but is determined by the positional relation between the mountain-like portion and the valley-like recess portion 326a consisting of the inclined surfaces 324 and 325 of the key button. 
     Numerals 324 and 325 denote the V-shaped surfaces of the key button flange portion or click portion (portion to determine the top dead point), and 326 indicates the supporting member. 
     Since there is a clearance between the slide surfaces of the key button 323 and the supporting member 326, with respect to the position of the key button at the bottom dead point, the center of the convex portion of the key button as shown in FIG. 32 rarely coincides with the center of the valley-like recess portion 326a of the supporting member. A central difference of dimension &#34;d&#34; occurs as shown in FIG. 33. In a state as shown in FIG. 34, the key button 323 abuts on the supporting member and thereafter the key button moves to the state as shown in FIG. 29. 
     At this time, the whole return force F of the key button 323 is not applied to the valley-shaped recess portion 326a of the supporting member 326 as shown in FIG. 34, but a vertical component Fa of the force F functions as an abutting force on the supporting member 326 and a horizontal component Fb of the force F serves an acting force to move the key button to the center and becomes a factor of the component of force to abut on the inclined surface on the opposite side. Thus, the automatic center adjusting function occurs. 
     In the conventional structure, the return force F of the key button causes an annoying hitting sound. On the other hand, according to the invention, Fa&lt;F is expressed as a hitting sound due to the vertical component Fa of force and at the same time, the horizontal component Fb of force abuts on the inclined surface on the opposite side as a reduced force lower than the value of Fb due to the friction upon movement of the key button to the center. Thus, the hitting sound can be reduced due to the distribution of the force and the decrease in the friction. 
     In addition, in the above description, the mountain portion having the convex shape has been formed on the key button side and the valley portion having the concave shape has been provided on the supporting member side. However, in the case where the concave valley portion is provided on the key button side and the mountain portion of the convex shape is provided on the supporting member side, a similar effect can be obtained. Also, a similar effect will be obtained even due to a combination of various kinds of zigzag shapes other than the V-shape. 
     Further, in the fourth embodiment mentioned above, the mountain portion has been provided in the flange portion of the key button 323. However, as in the fifth and sixth embodiments shown in FIGS. 30 and 31, respectively, the inclined surfaces 324 and 325 may be also provided in the projecting portions other than the flange portion of the key button and the supporting member may be also complementarily formed with valley-shaped concave portions at the positions adapted to come into engagement with these mountain portions. 
     As will be apparent from the above description, according to the present invention, the key button and the engaging portion of the supporting member are formed in a zigzag shape having a complementary relationship. Therefore, automatic center adjustment due to the zigzag portion is performed when the key button ascends and the key button can be positively reoriented at a predetermined location so as to have an accurate position. At the same time, hitting sound generated when the key button reaches the top dead point can be remarkably reduced.