Abstract:
A switch mechanism of a detection sensor unmounted type has a configuration in which an attaching surface for a case body for containing a movable member moved in conjunction with a button operation and a mounting surface for a detection sensor operative to electrically detect a change in the position of the movable member attendant on the button operation are different, and a magnifying mechanism operative to magnifyingly transmit the change in the position of the movable member attendant on the button operation is mounted in the switch mechanism.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   The present invention contains subject matter related to Japanese Patent Application JP 2005-142607 filed with the Japanese Patent Office on May 16, 2005, the entire contents of which being incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   The present invention, in its one embodiment, relates to a switch mechanism of a type in which a detection sensor containing a movable member moved in conjunction with a button operation is not mounted. In another embodiment, the present invention relates to an electronic apparatus wherein the switch mechanism of the type in which the detection sensor is not mounted is attached to an operating surface. 
   In contents production sites and output sites, a large number of material data and program data are dealt with daily. For example, in a contents production site, a multiplicity of material data are dealt with in an editing work. Also, in a contents output site, in addition to produced program data, a large number of live data are switchedly outputted. 
   In carrying out such works, generally, a control panel having an arrangement of a large number of switches is used. The number of the switches arranged may, in some cases, mount up to several hundreds. 
   Therefore, each of these switches incorporates a mechanism for enabling easy confirmation of the operation state (ON/OFF) of the switch. For example, a switch incorporates a mechanism for turning ON a button surface when the switch is in the ON state. 
     FIG. 1  illustrates a conceptual configuration of a switch.  FIG. 1  shows a structure example of a switch based on a system in which a drive mechanism and an electric part are separate from each other. 
   In the case of this example, the drive mechanism is composed of a button top  3  and a shaft  5  which are housed in a main body case  1 . Incidentally, the drive mechanism is attached to an operating surface  7  through the main body case  1 . 
   On the other hand, the electric part is composed of a photosensor  11  mounted on a wiring board  9 . 
   In the switch with this configuration, as the button top  3  is depressed, the tip end of the shaft  5  attached to a bottom portion of the button top  3  is lowered to such a position as to intercept the optical path of the photosensor  11 . This condition is detected, whereby the operation of the pushbutton is detected. The condition where the shaft  5  has been pushed down is shown in  FIG. 1B . 
   Incidentally, the main body case is provided on the inside thereof with a step for providing a lowermost point of the depressed position, so that when the button top  3  is depressed to the lowermost point, the bottom surface of the button top  3  abuts on the step and is thereby stopped. 
   Besides, when a finger having depressed the button top  3  is put off, the button top  3  is returned to its original position by a repelling force of a compression coil spring (not shown). In this instance, the photosensor  11  is again set into a light-detecting condition, to detect that the pushbutton operation is removed. The condition where the shaft  5  has been returned into its original position is shown in  FIG. 1A . 
   (See, for example, Japanese Patent Laid-open No. 2005-85506) 
   SUMMARY OF THE INVENTION 
   Meanwhile, the drive mechanism and the detection sensor are connected through many component parts. Therefore, there is a tendency toward accumulation dimensional dispersions of the component parts, assembly errors of the component parts, mounting errors of the detection sensor, etc. 
   In particular, where deviations in the vertical direction (the direction in which the drive mechanism and the detection sensor on the wiring board are away from each other) are present, there is the possibility that the tip end of the shaft  5  may not reach the position of the detection sensor even when the button top is depressed. 
     FIG. 2  shows such a situation.  FIG. 2A  shows the condition where the operating surface  7  and the wiring board  9  are remote from each other further by ΔL, as compared with the designed mounting position (indicated by broken line). In this case, as shown in  FIG. 2B , even when the button top  3  is depressed, the tip end of the shaft  5  cannot intercept the light of the detection sensor  11 . The value of ΔL is, for example, 2 mm. 
   In addition, even in the case where the tip end of the shaft  5  can intercept the light of the detection sensor  11 , the position of detection of the ON/OFF state may be shifted. 
   In such a situation, accurate ON/OFF operations cannot be expected. For example, the switching operations become instable, or the feeling of operation may be worsened. 
   Therefore, in the case of a switch having a conventional structure, it may be necessary to keep the dimensional accuracy and assembly accuracy of component parts very high. At the same time, also as to the attaching surface and the mounting surface, high mounting accuracies and restrictive conditions may be needed. 
   Paying attention to the above-mentioned technical problems, the present inventors propose a switch mechanism of a detection sensor unmounted type, wherein an enlarging mechanism for transmitting, in a magnified form, a change in the position of a movable member attendant on a button operation is mounted. 
   Incidentally, an attaching surface for a case body for containing the movable member moved in conjunction with the button operation is assumed to be different from a mounting surface for the detection sensor for electrically detecting a change in the position of the movable member attendant on the button operation. 
   With the magnifying mechanism adopted, the reliability of the switching operations is enhanced. Besides, the mounting accuracy and restrictive conditions required on the side of a housing to which the switch mechanism is attached can be moderated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  are diagrams illustrating the relationship between a shaft and a photosensor in the case where no mounting error is present (an example of the related art); 
       FIGS. 2A and 2B  are diagrams illustrating the relationship between the shaft and the photosensor in the case where a mounting error is present (an example of the related art); 
       FIG. 3  is a diagram illustrating an example of use form of a live switcher; 
       FIG. 4  is a diagram illustrating a configuration example of a control panel surface for the live switcher; 
       FIG. 5  is a diagram illustrating a mounted condition of an operating button; 
       FIG. 6  is a diagram showing optical paths inside a light guide tube along which light reflected on a silk screen printed surface passes; 
       FIG. 7  is a diagram showing an appearance of an operating button; 
       FIG. 8  is a diagram illustrating the inside structure of the operating button (at normal time); 
       FIG. 9  is a diagram illustrating the inside structure of the operating button (when depressed); 
       FIG. 10  is a diagram illustrating the relationship between a shaft and a photosensor in the case where no mounting error is present (an embodiment of the present invention); and 
       FIG. 11  is a diagram illustrating the relationship between the shaft and the photosensor in the case where a mounting error is present (an embodiment of the present invention). 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Now, an embodiment of a switch mechanism of a detection sensor unmounted type and a control panel according to the technique pertaining to the present invention will be described below. 
   It is to be noted that known technologies in the art pertaining to the invention are applied to the portions not specifically shown in the drawings or described in this specification. 
   Besides, the embodiment described below is merely an embodiment of the present invention, and the invention is not limited to or by the embodiment. 
   (A) Control Panel 
     FIG. 3  illustrates an example of a control panel for a live switcher.  FIG. 3  corresponds to an operating surface of the control panel  21 . Operating buttons  23  are arranged in a number of stages on the control panel  21 . By operating the operating buttons  23 , it is possible to perform switching of signals to be connected, turning ON/OFF of various functions, switching of mode, and the like operations. 
     FIG. 4  illustrates the face structure of the control panel  21  in the condition where the operating buttons  23  have been removed. The operating buttons  23  are inserted into openings  25  formed in the panel face of the control panel  21 , from the face side, and are locked mechanically. 
   (B) Operating Button 
     FIG. 5  is a diagram showing, in enlarged form, a mounting portion of one operating button  23 . Incidentally, the operating button  23  is composed of a plurality of plastic parts. 
   The operating button  23  is composed of a key top  31  and a main body case  33 . 
   The key top  31  is detachably attached to an end portion, on the face side, of the main body case  33 . In this embodiment, lock pawls  311  for attachment are arranged so as to respectively face two side surfaces of the key top  31 . 
   The key top  31  has an appearance which is roughly square as viewed from the face side of the control panel  21 . Incidentally, the operating surface of the key top  31  is provided with a concavity for easy operation thereof. 
   The key top (button&#39;s operating surface)  31  is formed of a light-transmitting material so that the operation status of the operating button  23  can be visually confirmed by the turning-ON/OFF of light or changes in light emission color which are confirmed through the key top  31 . Namely, the operating button  23  is a lighting button. Here, the key top  31  is mounted in a hole in an inside upper portion of the main body case  33  by hook pawls. 
   In this embodiment, the operating button  23  is composed only of a drive mechanism, and electronic parts (surface-mounted parts, a wiring pattern, a resistor, etc.) are all mounted on a printed wiring board  27 . In other words, the operating button  23  is completely separated from the electric circuit, and the light confirmed through the key top  31  is guided from a light emitting device mounted on the printed wiring board  27 . 
   As the light emitting device, for example, two kinds of LEDs (Light Emitting Diodes) different in light emission color are used. Incidentally, the number and the layout positions of the LEDs  271  allotted to one operating button  23  may be arbitrarily selected. In this embodiment, six LEDs  271  are arranged for one operating button  23 . The six LEDs  271  consist of four green LEDs  271 A and two red LEDs  271 B. 
   A technique is adopted in which the light emitted from each LED  271  is guided to the key top  31  through the light guide tube  331  arranged in the inside of the main body case  33 . 
     FIG. 6  shows a layout example of the light guide tube  331 . The light guide tube  331  is formed of a transparent resin, for example, an acrylic resin. In view of a structural restriction imposed on the operating button  23 , an inverted U-shaped structure is adopted for the light guide tube  331 . The restriction here is the need to dispose a compression coil spring  333  under a central portion of the operating surface. 
   The light of the LED  271  is emitted roughly hemispherically toward the upper side of the board, due to the light orientation characteristic of the LED  271 . In view of this, the shape of the light guide tube  331  on the light intake side is specially designed so that reflection of the light on the surface of the light guide tube  331  is prevented as much as possible. 
   Incidentally, a lighting button (an operating button of which the operating surface can be luminous) may be disposed very close to the adjacent lighting button. In view of this, a contrivance is also adopted such as to obviate the situation in which the light radiated from the LED might be transmitted through the light guide tube of the adjacent switch to illuminate the adjacent key top. Specifically, a structure is adopted in which the light guide tube  331  is covered with the main body case  33 , to a position very close to the printed wiring board  27 . 
   In addition, the inside surface of the light guide tube  331  is contrived to enhance reflection efficiency so as to prevent light from escaping. For example, the inside surface of the light guide tube  331 , exclusive of an upper end surface, is mirror finished. Therefore, the light entering the inside of the light guide tube  331  undergoes total reflection, to be thereby guided to the upper end surface. Incidentally, with the light reflected (disturbed) in the interior of the light guide tube  331 , the light guided to the upper end surface becomes uniform, whereby irregularities in luminance or in color are reduced. 
   Incidentally, the light guided to the upper end surface of the light guide tube  331  is radiated at all angles from the ceiling surface by crimps or a diffusing material formed on the ceiling. 
   The light radiated from the light guide tube  331  is incident on the inside surface of the key top  31 . In this embodiment, for further enhancing the light diffusing effect, a diffuser plate is disposed just on the inside of the key top  31 . The diffuser plate is formed of a material loaded with a diffusing agent. For example, the diffuser plate is formed of a material loaded with PET (PolyEthylene Terephthalate). 
   Further, in this embodiment, a contrivance for increasing the amount of light guided to the key top  31  is adopted. Specifically, a white-colored silk screen printed surface  273  is formed in the surroundings of the LEDs  271  (on the surface, opposed to the light guide tube  331 , of the printed wiring board  27 ). 
   With the silk screen printed surface  273  thus provided, the reflectance of the board surface is enhanced. This ensures that the light radiated toward the printed wiring board  27  and the light reflected by the lower surface of the light guide tube  331  to return to the board surface can be wastelessly guided in the direction of the light guide tube  331 . 
   Incidentally, the silk screen printed surface  273  can be formed by utilizing the silk screen process for producing the printed wiring board  27 . Therefore, little additional cost is needed. 
   With the silk screen printed surface  273  thus arranged, the key top  31  of the lighting switch becomes brighter and is thereby enhanced in visibility. 
   In addition, a detecting device for detecting an operation of depressing the key top  31  is mounted on the printed wiring board  27 . In this embodiment, a non-contact type sensor is used as the detecting device. For example, there is arranged a transmission-type photosensor  275  having a light emitting portion and a light receiving portion opposed to each other, with the moveable range of a turnable light-shielding plate  335  as a movable member therebetween. 
   The photosensor  275  detects the movement of the turnable light-shielding plate  335 , thereby the turning ON/OFF of the switch by the depressing of the key top  31 . Incidentally, the result of the detection is given to a control circuit for controlling the light emission of the LEDs  271 . 
   In this embodiment, when the key top  31  is not depressed, the turnable light-shielding plate  335  intercepts the light emitted from the light emitting portion, resulting in that the light receiving portion does not detect the light. 
   On the other hand, when the key top  31  is depressed, the condition where the light from the light emitting portion is detected by the light receiving portion results. The detecting device is not limited to the transmission-type photosensor; for example, a reflection-type photosensor, an electromagnetic induction type or electrostatic type non-contact sensor, a contact-type sensor using metal or rubber as contacts, or the like can also be used. 
     FIG. 7  shows an example of an appearance of the operating button  23 . As has been described referring to  FIG. 5 , the operating button  23  is composed of the key top  31  and the main body case  33 . 
   The main body case  33  is formed in a tubular shape rectangular in section. The outside size of the main body case  33  is determined based on the inside size of the opening  25  of the control panel  21 . Specifically, the outside size of the main body case  33  is set to be slightly smaller than the inside size of the opening  25 . On the other hand, the top outer edge portions  337  of the main body case  33  are formed to be larger than the opening  25 . The top outer edge portions  337  of the main body case  33  function as a stopper for preventing the main body case  33  from falling into the inside of the control panel  21 . 
   A total of four lock pawls  339  are formed at side surfaces of the main body case  33 . Of the four lock pawls  339 , two are formed on each of two opposite ones of the four side surfaces constituting the main body case  33 . 
   Each of the lock pawls  339  is fixed to the side surface at one end thereof, whereas the other end thereof is completely separated from the main body case  33  by gaps  341  so formed as to surround the outer periphery of the lock pawl  339 . 
   In addition, the lock pawl  339  is so mounted that its projection amount relative to the side surface of the main body case  33  increases along the direction from its fixed end toward its free end. In other words, the lock pawl  339  is mounted in a skew direction relative to the insertion direction of the main body case  33 . 
   Due to this structure, at the time of inserting the main body case  33  into the opening  25 , the outside inclined surfaces of the lock pawls  339  abut on the inner wall surfaces of the opening  25 , and are deflected to the inside of the main body case  33  by the attendant stress. 
   It is to be noted here that when the main body case  33  is inserted until it reaches a prescribed position, the outside inclined surfaces of the lock pawls  339  are released from the abutment on the inner wall surfaces of the opening  25 . In this instance, each lock pawl  339  restores its positional relationship with the main body case  33  before the insertion, under its own elastic restoring force. In other words, each lock pawl  339  is opened to the outer side relative to the side surface of the main body case  33  under its own restoring force. 
   In this instance, the condition where the control panel  21  is clamped from both sides thereof by the top outer edge portions  337  and the lock pawls  339  is obtained. This results in that the main body case  33  is locked to the control panel  21 . In other words, the top outer edge portions  337  function to prevent the main body case  33  from falling into the inside of the control panel  21 , and the lock pawls  339  function to prevent the main body case  33  from being disengaged to the face side of the control panel  21 . 
   Accordingly, for releasing the locked condition, it suffices to deform the lock pawls  339  to the inside of the main body case  33  and thereby to release the lock pawls  339  from the abutment on the back surface of the control panel  21 . 
   In addition, a component part operated according to button operations is incorporated in the main body case  33 . In this embodiment, a movable mechanism for converting the button operations into rotating motions of the turnable light-shielding plate  335  is mounted in the main body case  33 . 
   Referring to  FIGS. 8 and 9 , the movable mechanism will be described in brief. Incidentally,  FIG. 8  shows the engagement relationship of the movable mechanism in the condition where the key top  31  is not depressed. On the other hand,  FIG. 9  shows the engagement relationship of the movable mechanism in the case where the key top  31  is depressed. A diffuser plate  313  arranged on the inside of the key top  31  is also shown in  FIGS. 8 and 9 . 
   The movable mechanism is composed of a slider  343 , a compression coil spring  345 , a torsion coil spring  347 , and the turnable light-shielding plate  335 . Incidentally, the turning mechanism is contained in a holder  349  which is fitted in a bottom portion of the main body case  33 . 
   The slider  343  is a component part which is moved up and down correspondingly to the operations of the key top  31 . The slider  343 , for not slipping off from the main body case  33 , is guided along guide grooves  33 A in the main body case  33  by guide projections  343 A 1  and  343 A 2  formed on side surfaces thereof. 
   The guide projections  343 A 1  are stoppers for stopping an upward sliding motion by abutting on the upper ends  33 A 1  of the guide grooves  33 A. On the other hand, the guide projections  343 A 2  are stoppers for stopping a downward sliding motion by abutting on the lower ends  33 A 2  of the guide grooves  33 A. 
   A portion of the slider  343  constitute a shaft  343 B. The shaft  343 B is a component part by which a depressing force exerted on the key top  31  is transmitted to one end portion  335 A of the turnable light-shielding plate  335 . Here, the turnable light-shielding plate  335  is turned about a turning shaft  335 B fitted in a shaft hole formed in the holder  349 . 
   The turnable light-shielding plate  335  corresponds to the see-saw structure as set forth in the claim. Therefore, when the end portion  335 A is depressed by the shaft  343 B, the other end  335 C of the turnable light-shielding plate  335  is lifted up, reversely. On the contrary, when the other end  335 C of the turnable light-shielding plate  335  is lowered, the end portion  335 A is lifted up, reversely. 
   At the times of the turning motions, the other end portion  335 C of the turnable light-shielding plate  335  is moved across the optical axis of the photosensor  275 . 
   Here, the arms of the turnable light-shielding plate  335  are formed to be asymmetric with respect to the turning shaft  335 B. In this embodiment, the length of the arm from the turning shaft  335 B to the end portion  335 C is set to be larger than the length of the arm from the turning shaft  335 B to the end portion  335 A. 
   With the arm lengths set to be asymmetric, the shifting amount of the longer arm is magnified, as compared with the shifting amount of the shorter arm. Therefore, the moving amount of the end portion  335 C is magnified to several times the depression amount. 
   Incidentally, the moving amount of the end portion  335 C is magnified in the vertical direction. Accordingly, even where the parts accuracy and the assembly accuracy are lowered and the vertical distance is enlarged as compared with the originally designed positional relationship, it is possible for the end portion  335 C to be moved across the optical axis of the photosensor  275 . 
   Here, the timing at which the end portion  335 C crosses the optical axis is the timing of switching. In this embodiment, the end portion  335 C is inverted U-shaped downwardly so that the switching timing will be stable irrespectively of variations in the relative distance. The recessed portion in the inverted U shape is provided at a position of crossing the optical axis. The presence of the recessed portion (or the inverted U shape) ensures that the condition of not intercepting the optical axis can be generated even at a stage where the moving amount of the end portion  335 C is small. 
   Incidentally, the depressed slider  343  is returned into the state before the depression, by a repelling force generated by the compression coil spring  345  which is fitted between a dowel formed on the lower surface of the slider  343  and a dowel formed on the holder  349 . 
   In addition, the end portion  335 C of the turnable light-shielding plate  335  lifted up attendant on the depressing operation is turned in the reverse direction by a restoring force of the torsion coil spring  347 . To be more specific, the end portion  335 C of the turnable light-shielding plate  335  is turned so as to be lowered to the position for intercepting the optical path of the photosensor  275 . 
   (C) Assembly of Operating Button 
   First, the compression coil spring  345  is attached to the dowel of the slider  343 . In this condition, the slider  343  is inserted from the upper opening side of the main body case  33 . 
   In this instance, the guide projections  343 A 1  and  343 A 2  are fitted in the guide grooves  33 A in the main body case  33 . In addition, the shaft  343 B of the slider  343  is inserted in a hole provided in the main body case  33 . Thereafter, the light guide tube  331  is inserted from the lower opening side of the main body case  33 . Incidentally, the light guide tube  331  is so structured that a projected portion at its tip end is hooked on a pawl at the bottom of the main body case  33  and, therefore, it will not slip off. 
   Next, the torsion coil spring  347  is attached to the turning shaft  335 B of the turnable light-shielding plate  335 . In this condition, the turning shaft  335 B of the turnable light-shielding plate  335  is fitted into a bearing portion of the holder  349 . In this condition, the holder  349  is mounted into position from the lower opening side of the main body case  33 . 
   Upon the above assembling steps, the switch mechanism of the detection sensor unmounted type is completed. In this specification, the whole of the main body case  33  and the drive mechanism incorporated therein is referred to as the “switch mechanism”. 
   Subsequently, the switch mechanism is mounted into the opening  25  from the face side of the control panel  21 . The switch mechanism is so structured that it is prevented, by the lock pawls  339  provided at the side surfaces of the main body case  33 , from easily slipping out of position. 
   At this state, the diffuser plate  313  is attached to the key top  31 . Specifically, the diffuser plate  313  is lightly press fitted into the inside of inner edge portions of the key top  31 . In this instance, lock pawls of the diffuser plate  313  are inserted into and hooked in side grooves of the key top  31 , and the key top  31  and the diffuser plate  313  are united. 
   The groove at the press fit portion between the key top  31  and the diffuser plate  313  functions also as a hook portion at the time of detaching the key top  31  from the slider  343  by use of a tool. 
   Thereafter, the key top  31  is attached to the slider  343  inside the main body case  33  attached to the control panel  21 . 
   The control panel  21  is mounted on an apparatus main body for housing the printed wiring board  27 , whereby the live switcher is completed. 
   (D) Switch Actions 
   (a) Basic Action 
   As shown in  FIG. 8 , in the condition where the key top  31  is not depressed, the tip end portion  335 C of the turnable light-shielding plate  335  is at a position for intercepting the optical axis of the photosensor  275 . 
   With the key top  31  depressed under this condition, the slider  343  is moved downwards. When the depression amount reaches or exceeds a predetermined amount, the tip end of the shaft  343 B formed at the lower end of the slider  343  begins to depress the one end portion  335 A of the turnable light-shielding plate  335 . 
   As a result, the turnable light-shielding plate  335  is turned counterclockwise about the turning shaft  335 B, resulting in the condition where the optical axis of the photosensor  275  is opened as shown in  FIG. 9 . 
   The opening of the optical axis is detected by a control circuit connected to the photosensor  275 . This means that the depression of the key top  31  has been successfully detected in a non-contact manner. 
   When the depression of the key top  31  is stopped under this condition, the slider  343  (i.e., the key top  31 ) is returned into its original position by the repelling force of the compression coil spring  345 . Attendant on this, the turnable light-shielding plate  335  freed from the depressing force exerted by the shaft  343 B is rotated clockwise by the restoring force of the torsion coil spring  347 . As a result, the turnable light shielding plate  335  is returned into its original position, so as to again intercept the optical axis of the photosensor  275 . 
   The interception of the optical axis is detected by the control circuit connected to the photosensor  275 . 
   The switch mechanism includes no portion that receives external forces, inclusive of friction, other than the repelling force of the compression coil spring  345 , and the detection sensor of the non-contact type is used in the switch mechanism; therefore, a good feeling of operation can be obtained with the switch mechanism. 
   In addition, the repelling force of the torsion coil spring  347  is a very light restoring force which is required only to rotate only the turnable light-shielding plate  335  into its original position when the slider  343  is not being pushed down. 
   Therefore, there is no possibility that the repelling force might rapidly increase from an intermediate point in the stroke of the key top  31  to thereby worsen the feeling of depression. 
   (b) Actions in the Case of a Large Error in Relative Position 
   Referring to  FIGS. 10 and 11 , description will be made of the difference generated in the switching operation in the case where a mounting error is generated between the control panel  21  and the printed wiring board  27 . 
   Incidentally,  FIG. 10  corresponds to the case where the positional relationship between the control panel  21  and the printed wiring board  27  accords to a designed center value. On the other hand,  FIG. 11  corresponds to the case where the positional relationship between the control panel  21  and the printed wiring board  27  is widened by 2 mm, as compared with the designed center value. 
   Here, a is the distance between the shaft-side end portion  335 A of the turnable light-shielding plate  335  and the turning shaft  335 B, and b is the distance between the photosensor-side end portion  335 C of the turnable light-shielding plate  335  and the turning shaft  335 B. 
   Besides, in  FIGS. 10 and 11 , it is assumed that the relation of b=2.5a is satisfied. Namely, it is assumed that the distance b is 2.5 times the distance a. 
   With the arm length on the photosensor side set to be 2.5 times that on the shaft side, the stroke on the photosensor side can be made to be 2.5 times the stroke on the shaft side. Therefore, it is possible to substantially exclude the influence of a mounting error, if any, in the vertical direction between the operating button  23  and the photosensor  275 . 
   In other words, the switch can be turned ON/OFF at the time when the operating button  23  is stroked by a specified amount, irrespectively of the presence or absence of the mounting error in the vertical direction. This is effective for stabilizing the feeling of switch operation. In both cases of  FIG. 10  and  FIG. 11 , the stroke margin is substantially the same. 
   In addition, with the rotation range of the turnable light-shielding plate  335  widened, it is always possible to produce the optical axis intercepting condition through abutment of the turnable light-shielding plate  335  on a bottom portion of the photosensor  275 , as shown in  FIG. 11 , even in the case where the positional error in the direction of parting away in the vertical direction is enlarged. Accordingly, it is possible to maintain assured switch actions. 
   Incidentally, in the case where a mounting error in the approaching direction is generated between the control panel  21  and the printed wiring board  27 , the end portion  335 C of the turnable light-shielding plate  335  interferes with and collides on the bottom portion of the photosensor  275 . In this case, a relief mechanism such as a torsion coil spring is provided, for obviating the breakage of a component part or the exertion of an irrational force. 
   (E) Effects 
   In the case of a switch mechanism composed of a plurality of component parts, it is necessary to take into account the dispersions in dimensional accuracy of the individual parts, assembly errors and the like. It is difficult to always secure the dimensional accuracy among the component parts, and enhancing the accuracy is inevitably accompanied by rises in the parts cost and the assembly cost. 
   However, where a stroke magnifying mechanism (the turnable light-shielding plate  335  such that the arm length on the photosensor side is set to be several times the arm length on the shaft side) is mounted on a switch mechanism, secure switching actions can be ensured even where a lowering in accuracy or an assembly error is present. 
   Even though the mounting of the magnifying mechanism is accompanied by a slight increase in the cost of the switch mechanism, an enhanced reliability according to the raised cost can be secured. 
   In addition, it is possible to provide margins as to the reliability of the switch mechanism component parts themselves. Therefore, it is possible to reduce the assembly accuracy and restrictive conditions demanded on the side of the housing of the live switcher. This facilitates the designing on the housing side. 
   From the foregoing, it is understood that reliability of operations can be secured not only for the individual switch mechanisms but also for the apparatus as a whole. 
   Besides, in this embodiment, the white color silk screen printed surface  273  is formed in the surroundings of each LED. Therefore, the luminance of the key top  31  can be enhanced without increasing the number of the LEDs or passing an increased current so as to increase the power consumption. Accordingly, the useful life of the LEDs can be prolonged. 
   The enhanced luminance of the key top  31  naturally leads to an enhanced visibility to the operator. 
   In addition, the formation of the silk screen printed surface  273  does not need any special component part or technology; namely, the silk screen printing conventionally used on the wiring board can be utilized as it is. Therefore, an additional cost would not be generated. 
   (F) Other Embodiments 
   
       
       (a) While two kinds of LEDs, i.e. green and red LEDs, have been arranged in the above embodiment, one kind of LEDs emitting light in an arbitrary color may be arranged. Besides, one kind of LEDs capable of emitting light in a plurality of colors may be arranged. Incidentally, in the case where one kind of LEDs capable of emitting light in a plurality of colors are used, color irregularities according to the light emission colors can be suppressed easily. 
       (b) In the above embodiment, the case where the main body case  33  has a tubular shape rectangular in cross section has been described. However, the main body case may be circular or polygonal in cross section, inasmuch as the basic shape of the main body case is a tubular shape. 
       (c) In the above embodiment, the arm length on the photosensor side has been set to be 2.5 times that on the shaft side. However, this is merely an example, and the value of the magnification factor may be appropriately selected according to the sizes which can be adopted in mounting the turnable light-shielding plate  335 . 
       (d) In the above embodiment, the case where the light guide tube  331  for guiding the light generated at the printed wiring board  27  to the key top  31  is mounted in the inside of the operating button  23  has been described. 
     
  
   However, a configuration in which the light is not guided to the key top  31  may also be adopted.
     (e) In the above embodiment, the case where the see-saw structure is used as the mechanism for magnifying the stroke relative to the key top  31  has been described.   

   However, the magnifying mechanism can be realized by other mechanisms such as a link mechanism, a crank mechanism, and a mechanism using gears or a belt.
     (f) In the above embodiment, the turnable light-shielding plate  335  having the see-saw structure has been described.   

   However, where an electrostatic induction type detection sensor or an electromagnetic induction type detection sensor is utilized for the detection of the switching actions, it suffices that a detection element according to the detection sensor is arranged at the end portion  335 C of the turnable light-shielding plate  335 . 
   In addition, where a contact-type detection sensor is utilized for the detection of the switching actions, it suffices that a contact element is arranged at the end portion  335 C of the turnable light-shielding plate  335 .
     (g) In the above embodiment, the structure of the operating button in a business-use switcher has been described as an example of the switch mechanism.   

   However, the switch mechanism in the present invention is applicable to other switch mechanisms than the switcher and to a general-purpose switch mechanism, inasmuch as the switch mechanism is of the type in which an electric circuit such as a detection sensor and a drive mechanism are separate from each other. 
   For example, the switch mechanism in the present invention is applicable not only to an editing apparatus and a special effect apparatus but also to home-use electronic apparatuses and electric products.
     (h) Various modifications of the above-described embodiment are possible within the scope of the gist of the present invention. Besides, various modified examples and applied examples created on the basis of the description in the present specification are also possible.