Patent Publication Number: US-6339200-B1

Title: Electrostatic insulation for an operating unit for electronic equipment

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electrostatic insulation for an operating unit for electronic equipment that perform a variety of operations. 
     2. Related Art Statement 
     Conventionally, electronic equipment, such as a camera, is provided with an operating unit having operating members for performing a variety of operations. In such apparatuses, however, static electricity generated at operating portions of the operating members must be prevented from effecting electric circuits within the equipment because such static electricity may cause the failure of an electric circuit element. 
     An operating unit for electronic equipment presented and disclosed in Japanese Unexamined Patent Publication No. 7-263042 comprises a switch circuit substrate  34  disposed in the casing  31  of the equipment as shown in FIG.  5 . The switch circuit substrate  34  is constructed in such a manner that even when static electricity passes into the casing through the periphery of a operating button  32 , it is redirected to the ground via a grounding pin  36 . 
     The switch circuit substrate  34  is covered with an insulating sheet  35 , and provided with a grounding pin  36  with one end exposed from the insulating sheet and the other end soldered to the ground pattern on the main circuit substrate  33  located within the equipment. Therefore, even when static electricity generated at or applied to the periphery of the operating button  32  enters into the electronic equipment, such static electricity will be redirected to the ground on the main circuit substrate  33  via the grounding pin  36 . A switch element  37  and other components disposed on the switch circuit substrate  34  are protected against damage due to static electricity. 
     However, in the operating unit for electronic equipment disclosed in Japanese Unexamined Patent Publication 7-263042, as a measure against static electricity, a specific insulating sheet  35  for covering the switch circuit substrate  34  is required. Also, the grounding pin  36  attached to the insulating sheet  35  has to be connected to the main circuit substrate  33  by soldering, which could be disadvantageous in terms of space and cost. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an operation unit for electronic equipment which is free of the aforementioned disadvantages and is able to protect electronic parts disposed on the electric circuit against static electricity created by the operating members and the peripheries thereof, and is advantageous in terms of space and cost. 
     The operating unit of electronic equipment of the present invention comprises an electrically conductive supporting member for supporting the operating member, an electric circuit substrate being disposed at the inner part of the electronic equipment with respect to the supporting member and having a conductive pattern as well as an electric circuit element, and a ground connecting means for connecting the supporting member to the ground portion provided on the electric circuit substrate, wherein a part of the supporting member is in contact with the ground of the electric circuit substrate. 
     The operating unit for electronic equipment according to the present invention ensures protection of electronic parts on the electric circuit substrate against static electricity from the operating members or the peripheries thereof, and is advantageous in terms of space and cost. 
     These and other characteristics and advantages of the present invention will become more fully apparent from the following description in light of the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in detail below with reference to the following figures, throughout which similar reference characters denote corresponding features consistently, wherein: 
     FIG. 1 is an exploded perspective view of a switch operating unit for electronic equipment in accordance with one embodiment of the present invention; 
     FIG. 2 is a cross-sectional detail view of the switch-operating unit in accordance with the embodiment shown in FIG. 1; 
     FIG. 3 is a perspective view of the switch-operating unit in accordance with the embodiment shown in FIG. 1, disposed on a camera. 
     FIG. 4 is a perspective view of a supporting plate and a flexible printed circuit in the switch-operating unit in accordance with the embodiment shown in FIG. 1, as assembled; and 
     FIG. 5 is a vertical cross-sectional detail view of an operating unit for conventional electronic equipment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, an embodiment of the present invention will be described. 
     FIG. 1 is an exploded perspective view of the switch operating unit for electronic equipment in accordance with one embodiment of the present invention; FIG. 2 is a vertical cross-sectional detail view of the switch-operating unit shown in FIG. 1; FIG. 3 is a perspective view of the switch-operating unit shown in FIG. 1, disposed on a camera; and FIG. 4 is a perspective view of a supporting plate for supporting a switch button and a flexible printed circuit in the switch-operating unit of FIG. 1, as assembled. 
     The switch-operating unit of this embodiment is a switch for setting a variety of shooting conditions of a camera. The camera includes a camera body  1  as a body of electronic equipment. A switch supporting frame  2  is formed as a part of a front cover  10  which is a camera casing. A supporting plate  6  supports the operating member and is formed of electrically conductive material, such as metal plate. A dial  5 , an inner button  4 , and an outer button  3  are switch-operating members. A conical spring  11  is disposed between the outer button  3  and the inner button. An electric circuit substrate provides a flexible printed circuit (hereinafter FPC) having an electrically conductive resistance pattern  7   a.  A switch substrate  8  has a slide contact segment  12  slidable on the conductive pattern  7   a  on the FPC  7  and a plurality of metal switch armatures  17  and  18  disposed under the switch supporting frame. 
     On the switch supporting frame  2 , there a ratcheting ball retaining portion  2   c,  having an opening thereon, receives a ratcheting ball  13  for the dial  5  and a compressed spring  14  for urging the ball  13  toward the opening. 
     The supporting plate  6  pressably supports the outer button  3  and the inner button  4  and rotatably supports the inner periphery of the dial  5 . The supporting plate  6  is positioned at a specified distance above the switch supporting frame  2  in such a manner that it covers the FPC  7 . The supporting plate  6  is fixed with screws  19  passing through tapped holes  2   a  and  2   b  of the supporting frame  2 . The supporting plate  6  is provided with screw inserting holes  6   a  and  6   b,  through holes  6   c  and  6   d  for receiving projecting legs  3   b  and  4   a  of the outer and inner buttons, described below, and a contact for ground connection  6   e  formed by bending a part thereof downwardly as a ground connecting means. 
     The dial  5  is supported by the supporting plate  6  in such a manner that the axial position of the dial  5  is limited by the supporting plate  6 . The dial  5  can be rotated by holding and turning the outer peripheral portion above the switch supporting frame  2 . On the inner periphery thereof, there are provided depressions  5   a  and projections  5   b  alternately at specified pitches. When the dial  5  is rotated, the depressions  5   a  and projections  5   b  effect engagement with and disengagement from the ratcheting ball  13  to allow ratcheting rotation thereof. The extent of rotation of the dial  5  is limited to the specified angle by stoppers  2   h  provided on the switch supporting frame  2 . 
     The outer button  3  is received in the inner periphery of the dial  5  and is biased by the conical spring  11  downwardly or toward the switch supporting plate. The outer button  3  is supported so as to be tiltable in four directions on the supporting plate  6 . On the outer button  3 , there are provided projecting legs  3   b  which are to be passed through the supporting plate  6 . 
     The inner button  4  has a projecting leg  4   a  which is slidably inserted into a guide hole  3   a  formed on the outer button  3  and then passed through the supporting plate  6 . The inner button  4  is biased upwardly by the conical spring  11  and locked to the supporting plate  6  by means of claws. The claws inhibit the upward movement of the inner button  4 , but allow a specified extent of downward movement by pressing action. 
     The FPC  7  is disposed on the upper surface of the switch supporting frame  2  below the supporting plate  6  and the dial  5 . The FPC  7  is provided with a ground pattern  7   b  to be connected to the ground line of the electric circuit portion on the side of the body  1 . The ground pattern  7   b  also connects with the above described conductive resistance pattern  7   a,  and is equipped with an electric circuit element  7   c.  Holes  7   d  and  7   c  receive projecting legs  3   b  and  4   a  of the outer and inner buttons. 
     The slide contact segment  12  is supported on the inner side of the dial  5  and rotated integrally therewith. By rotating the dial  5 , the slide contact segment  12  slides on the conductive resistance pattern  7   a  formed of FPC  7  and outputs signals corresponding to the angular position of the dial  5  via FPC  7 . 
     The switch substrate  8  is disposed between the lower surface of the switch supporting frame  2  and the camera body  1 . A plurality of switch armatures  18  located on the upper surface of the switch substrate  8  may be selectively pressed by a plurality of projecting legs  3   b  of the outer button  3 . A switch armature  17  located in the center thereof may be pressed by the projecting leg  4   a  of the inner button  4 . Accordingly, the switch patterns of the switch substrate  8  positioned respectively under switch armatures  17  and  18  are turned on and off to output operation signals. 
     With this switch unit assembled, the supporting plate  6  and FPC  7  are supported at a specified distance as shown in FIGS. 2 and 4. The supporting plate  6  and FPC  7  are kept in contact with each other by the tip of the contact  6   e  of the supporting plate  6  being in contact with the ground pattern on FPC  7 . In other words, the supporting plate  6  is electrically connected to the ground line of the electric circuit portion on the side of the body  1  via the ground pattern  7   b.    
     With this switch-operating unit constructed as described, by pressing the inner button  4 , the switch armature  17  is pressed, and by pressing the outer button  3  by tilting same, any one of switch armatures  18  is pressed, which initiate associated switch-on signals output from the switch substrate  8 . By rotating dial  5 , output signals corresponding to the angular positions thereof are issued from FPC  7 . Based on each output signal, as described above, the shooting conditions are set up by the electric circuit portion on the side of the body  1  of the equipment. 
     If static electricity is generated or even applied to each operating member, such as the inner button  4 , the outer button  3 , and the dial  5 , or vicinity thereof and reaches the FPC  7 , such static electricity may be redirected toward the ground line of the electric circuit portion on the side of the body  1  of the equipment through the supporting plate  6  disposed inside those operating members and the ground pattern  7   b  of FPC  7 . Thus, the electronic circuit element and the like equipped on FPC  7  are protected against damage due to static electricity. 
     In the switch-operating unit of this embodiment, if static electricity is introduced by operating members, such as the outer button  3 , the inner button  4 , the dial  5  and so on into the inner electric circuit substrate, the electronic components mounted on the electric circuit may be protected against static electricity. In addition, since specific constructing members for redirecting static electricity are not required, the invention may be advantageous in terms of space and cost. 
     According to the present invention, as described, although static electricity may easily reach the inner electric circuit portion from the operating members, the electronic components mounted on the electric circuit substrate may be protected against static electricity because such static electricity may be redirected through the supporting member for supporting the operating members. In addition, since special constructing members for redirecting static electricity are not required, the invention may be advantageous in terms of space and cost. 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.