Patent Publication Number: US-8115130-B2

Title: Electronic device

Description:
BACKGROUND 
     The present invention relates to an electronic device including a switch-type electronic device such as a push switch adapted to be mounted on a printed circuit board to be disposed in various kinds of electronic apparatuses. 
     There are known various kinds of switch-type electronic devices such as a push switch mounted on a printed circuit board of an electronic apparatus (see, Japanese Patent Publication No. 9-120742 A). 
     As the conventional switch-type electronic device to which the countermeasure for the static electricity is applied, one example will be described by referring to  FIGS. 10 to 14 . 
     As shown in  FIG. 11 , a push switch  101  comprises a box-shaped housing  102  formed with a space  103  an upper side of which is opened. A circular dome-shaped movable contact  104  made of an elastic thin metal plate is disposed on an inner bottom part of the space  103 . A central lower face of the movable contact  104  opposes fixed contacts  105   a  and  105   b  each of which is made of the thin metal plate and fixed on the housing  102  by insertion molding. A protective film  106  is disposed on an upper part of the movable contact  104 , and an operating member  107  made of resin is disposed on the protective film  106 . A cover  108  made of metal is attached to the housing  102  so as to cover the operating member  107  from above. 
     The housing  102  includes engaging projections  109  respectively protruding outward along a lower face  102   c  of the housing  102  at right and left corners of front and rear side faces  102   a  and  102   b  of the housing  102 . Further, in the other end sides, lead terminals  105 A and  105 B are provided that are directed outward the right and left side faces  102   d  and  102   d  of the housing  102  from the lower face  102   c.    
     The operating member  107  includes a pressed part  107   a  and an elastic actuator  107   b . The pressed part  107   a  extends from a front side face  102   a  of the housing  102  through an opening  111  formed in the front side face  102   a.    
     The cover  108  is located on an upper face of the housing  102 . The cover  108  includes an upper plate  108   a  having an inclined piece obliquely extended from a center part thereof toward the inside of the space  103 . A pair of legs  108   a  are extended downward from a front edge of the upper plate  108   a  along the front side face  102   a  of the housing  102 . A pair of legs  108   b  are extended downward from a rear edge of the upper plate  108   a  along a rear side face  102   b . At a lower end of each of the legs  108   b , an engagement piece  108   c  is formed so as to oppose a lower face of an associated one of the engagement projections  109 . The engagement pieces  108   c  are bent and caulked so that the cover  108  is retained on the housing  102 . 
     The pair of right and left legs  108   b  provided in the front side face  102   a  of the housing  102  are separated from each other sufficiently so that at least the operating member  107   b  of the operating member  107  can be translated therebetween. 
     In the push switch  101  mounted on the printed circuit board  115  in such a way, under a state that the operating member  107  is arranged at a position shown by a dashed chain line in  FIG. 11 , when a front end of the pressed part  107   a  is horizontally pressed rearward, the operating member  107  horizontally moves on the protecting film  106  along the upper face of the housing  102  and the end of the operating member  107   b  is directed downward by the inclined piece  110  to apply a push down force to the movable contact  104  located at a lower part. 
     When the push down force exceeds a prescribed level, as shown by a solid line of  FIG. 11 , the lower face of the central part of the movable contact  104  moves downward and comes into contact with the fixed contacts  105   a  and  105   b  to obtain a conductive state (turn-on state) in which the lead terminals  105 A and  105 B are short-circuited through the movable contact  104 . As an amount of pushing operation of the operating member  107 , when the rear face of the pressed part  107   a  abuts against the front side face  102   a  of the housing  102 , a further pushing operation is regulated. 
     When the operating force of the pressed part  107   a  is released, the movable contact  104  is self-restored to an original attitude to push up the operating member  107   b  and the end of the operating member  107   b  is guided by the inclined piece  110 , so that the operating member  107  is pushed back forward to the position shown by the dashed chain line in  FIG. 11  to return to an original non-conductive state (turn-off state). 
     However, the above-described conventional push switch has a structure that the operating member  107  is continued to be pressed from outside the front side face  102   a  of the housing  102  until the operating member  107  abuts against the front side face  102   a  of the housing  102 . The forces acting on the respective members during in the above pushing operation will be described with reference to  FIG. 13 . When the operating member  107  is pushed with a force (a pressing force) P, a pushing up force gradually acts on the cover  108  as the pushing operation proceeds. This force acts on the legs  108   b  as a force (a reaction force) f for pushing the legs  108   b  outward. In such a case, there is a probability that the legs  108   b  and the cover  108  would be deformed to damage a function of the switch. 
     In these days, downsizing of such a push switch is strongly demanded. The width of each side face of the housing  112  is required to be no greater than 3 mm, and the thickness of the cover  108  is required to be no greater than 0.2 mm. In such a size, the above-described deformation becomes remarkable. 
     As a countermeasure for preventing the deformation, the thickness or the size of the cover  108  or the width of the leg  108   b  may be increased to ensure the strength of parts. However, contrary to the above-described demand, the size of the push switch is increased. 
     SUMMARY 
     It is therefore one advantageous aspect of the present invention to provide an electronic device capable of preventing a cover from being deformed during a pushing operation of an operating member without increasing the size of the electric device. 
     According to one aspect of the invention, there is provided a switch-type electronic device adapted to be mounted on a circuit board, comprising: 
     a housing, having: 
     a first face, adapted to oppose the circuit board; and 
     a second face, intersecting with the first face and formed with a projection; 
     a cover, having: 
     a first part, covering a side of the housing opposite to the first face; 
     at least one second part, extending from the first part and opposing the second face; and 
     a third part, extending from each of the at least one second part and engaging with the projection; and 
     an operating member, having a first part disposed outside the housing and adapted to be operated by a user, and a second part disposed in the housing and configured to switch the electronic device between a first state and a second state when the first part is operated by the user, wherein: 
     the first part of the operating member has a portion opposing the second part of the cover, and is configured to abut against the second part of the cover when the electronic device is switched between the first state and the second state. 
     The switch-type electronic device may be configured such that: the at least one second part includes a pair of second parts; and the second part of the operating member is located between the pair of second parts. 
     The switch-type electronic device may be configured such that: a thickness of the cover is no greater than 0.2 mm. 
     According to one aspect of the invention, there is provided a push switch adapted to be mounted on a circuit board, comprising: 
     a housing, having: 
     a first face, adapted to oppose the circuit board; and 
     a second face, intersecting with the first face and formed with a projection; 
     a cover, having: 
     a first part, covering a side of the housing opposite to the first face; 
     at least one second part, extending from the first part and opposing the second face; and 
     a third part, extending from each of the at least one second part and engaging with the projection; 
     an operating member, having a first part disposed outside the housing and adapted to be operated by a user, and a second part disposed in the housing; 
     a movable contact, disposed in the housing and configured to be actuated by the second part of the operating member when the first part of the operating member is operated by the user; and 
     fixed contacts, disposed in the housing and configured to be electrically connected with each other by way of the movable contact when the movable contact is actuated by the second part of the operating member, 
     wherein the first part of the operating member has a portion opposing the second part of the cover, and is configured to abut against the second part of the cover when the fixed contacts are electrically connected with each other. 
     The push switch may be configured such that: the at least one second part includes a pair of second parts; and the second part of the operating member is located between the pair of second parts. 
     The push switch may be configured such that: a thickness of the cover is no greater than 0.2 mm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a push switch according to one embodiment of the present invention. 
         FIG. 2  is a sectional view taken along a line II-II in  FIG. 1  and showing a state that an operating member is pushed in. 
         FIG. 3  is a front view of the push switch. 
         FIG. 4  is a plan view of the push switch. 
         FIG. 5  is a side view of the push switch. 
         FIG. 6  is a bottom view of the push switch. 
         FIG. 7  is a perspective view of the push switch in a disassembled condition. 
         FIG. 8  is a perspective view showing a housing of the push switch. 
         FIG. 9  is a schematic view showing an arrangement of contact members and a cover of the push switch. 
         FIG. 10  is a perspective view of a conventional push switch. 
         FIG. 11  is a sectional view taken along a line XI-XI of  FIG. 10 . 
         FIG. 12  is a front view of the conventional push switch. 
         FIG. 13  is a plan view of the conventional push switch. 
         FIG. 14  is a side view of the conventional push switch. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLIFIED EMBODIMENTS 
     Exemplified embodiments of the invention are described below in detail with reference to the accompanying drawings. 
     As shown in  FIGS. 1 to 9 , a push switch  1  which is one example of a switch-type electronic device comprises a box-shaped housing  2  made of a resin material and formed with space  3  an upper side of which is opened shown in  FIGS. 2 ,  7  and  8 . A pair of first contact members  5  and  6  and a second contact member  7  are integrally embedded by an insert molding in an inner bottom part  4  of the space  3 . The pair of first contact members  5  and  6  are made of a metal plate. The second contact member  7  is made of a metal plate. As well as the conventional push switch, the width of each side face of the housing  2  is no greater than 3 mm. 
     As shown in  FIGS. 2 ,  7  and  8 , a fixed contact  5   a  is provided on one end of the first contact member  5  and exposed at the inner bottom face  4  of the space  3 . A lead terminal  5   b  is provided on the other end of the first contact member  5  and led out from a lower face  2   a  of the housing  2  so as to extend outward of one of opposite side faces  2   b  of the housing  2 . A fixed contact  6   a  is provided on one end of the first contact member  6  and exposed at the inner bottom face  4  of the space  3 . A lead terminal  6   b  is provided on the other end of the first contact member  6  and led out from the lower face  2   a  so as to extend outward of the other one of the opposite side faces  2   b  of the housing  2 . The first contact member  5  is provided with further lead terminals  5   b  which are led out from the lower face  2   a  so as to extend outward of the rear side face  2   c  of the housing  2 . 
     An external fixed terminal  7   a  is provided on one end of the second contact member  7  and exposed at a position on the rear side face  2   c  closer to one of the opposite side faces  2   b  (in  FIGS. 7 to 9 , the right side face) so as to extend downward from an upper face  2   d  of the housing  2  toward the lower face  2   a . A lead terminal  7   b  is provided on the other end of the second contact member  7  and led out from the lower face  2   a  so as to extend outward of the one of the opposite side face  2   b  on which the lead terminal  6   b  is disposed. 
     A front side face  2   e  of the housing  2  is formed with an opening  8  communicating with the space  3 . An operating member  9  includes a pressed part  9   a  and an actuator  9   b  (described later in detail). The operating member  9  is accommodated in the space  3  such that the pressed part  9   a  and a part of the actuator  9   b  extend outward through the opening  8 . At both side end portions of each of the rear side face  2   c  and the front side face  2   e , there are provided engagement projections  12  to which engagement pieces  10   c  of legs  10   b  provided on a cover  10  (described later in detail) are engaged by caulking. 
     A dome-shaped movable contact  13  made of a thin metal plate is disposed on above fixed contacts  5   a  and  6   a . A lower face of a top portion of the dome-shaped movable contact  13  opposes the fixed contact  6   a  across a gap therebetween. An outer peripheral portion of the dome-shaped movable contact  13  is in contact with the fixed contact  5   a.    
     A protecting sheet  14  made of an insulating resin sheet material such as polyamide resin is disposed above the movable contact  13 . The peripheral edge part of the protecting sheet  14  is mounted on the upper face of the housing  2  and fixed by adhesive agent so as to cover the space  3  therewith to prevent dust or foreign materials from entering the conductive members disposed in the space  3 . 
     As shown in  FIG. 7 , the operating member  9  is made of a resin and includes: the pressed part  9   a  which is always to be located outside the housing  2 ; the actuator  9   b  extended from the pressed part  9   a  toward inside the space  3 ; a slider  9   c  surrounding the actuator  9   b  across a gap  15   c  therebetween. The pressed part  9   a  has parts extended from a front end of the actuator  9   b  upward, downward, rightward and leftward. 
     The pressed part  9   a  serves as a face receiving an operation for pushing the operating member  9  from the outside of the housing  2 . Further, the pressed part  9   a  serves to prevent the legs  10   b  of the cover  10  located both sides of the opening  8  from being deformed forward. A lateral width of the pressed part  9   a  is, as shown in  FIG. 3 , sufficiently greater than a width of each of the legs  10   b . When the operating member  9  is pushed into the space  3  in the housing  2  and the turn-on state is established (described later in detail), a rear face of the pressed part  9   a  comes in contact with the legs  10   b  so that the pressed part  9   a  covers at least parts of the legs  10   b , thereby preventing the legs  10   b  from being deformed forward. Alternatively, the rear face of the pressed part  9   a  may come in contact with the front side face  2   e  and may oppose the legs  2   b  across minute gaps therebetween. 
     The operating member  9  is disposed above the protective sheet  14  so that an abutment part  9   d  which is a free end of the actuator  9   b  opposes an upper face of the top part of the dome-shaped movable contact  13  across the protective sheet  14 . The slider  9   c  is slidably disposed within the space  3 . 
     The cover  10  is formed by punching and bending a metal plate. The cover  10  includes: a flat upper plate  10   a  attached to an upper part of the housing  2  so as to cover the space  3 ; and four legs  10   b  extended from both side portions of each of a front edge and a rear edge of the upper plate  10   a  and bent downward. The engagement piece  10   c  is provided on a tip end of each leg  10   b . The engagement pieces  10   c  are caulked so as to engage with the lower faces of the engagement projections  12  to retain the cover  10  on the housing  2 . As well as the conventional push switch, the thickness of the cover  10  is no greater than 0.2 mm. 
     When the cover  10  is attached to the upper part of the housing  2 , one of the legs  10   b  attached on the rear side face  2   c  of the housing  2  comes in contact with the external fixed terminal  7   a  of the second contact member  7  so as to establish electric connection. The contact between the external fixed terminal  7   a  and the leg  10   b  is firmly retained by bending the engagement piece  10   c  of the leg  10   b  toward the housing  2  and caulking to engage with the engagement projection  12 . 
     An inclined part  10   d  is formed by bending a substantial center part of the upper part of the upper plate  10   a  toward the inside of the space  3  of the housing  2  by about 45 degrees. The inclined part  10   d  is so configured as to abut against the abutment part  9   d  of the actuator  9   b  to bias the actuator  9   b  in a direction pressing the movable contact  13 . When the cover  10  is attached to the upper part of the housing  2 , the inclined part  10   d  is located within the gap  15 . When the pressed part  9   a  is laterally (from front side) pressed, the abutment part  9   d  of the actuator  9   b  comes in contact with the inclined part  10   d  so that the abutment part  9   d  is guided in a direction that the movable contact  13  is pressed (downward perpendicular to the direction that the part  9   a  is pressed). Accordingly, the movable contact  13  is pressed downward and cones in contact with the fixed contacts  5   a  and  6   a.    
     In order to assemble the push switch  1 , the movable contact  13 , the protective sheet  14  and the operating member  9  are housed within the space  3  of the housing  2  in this order. Then, the cover  10  is attached to the upper part of the housing  2 . After that, the engagement pieces  10   c  of the legs  10   b  are respectively caulked to engage with the lower faces of the engagement projections  12 . 
     When the push switch  1  is mounted on the printed circuit board  20 , as shown in  FIG. 5 , the operating member  9  is projected forward from the printed circuit board  20 , and the lead terminals  5   b ,  6   b  and  7   b  are soldered with associated wiring parts. In this condition, the second contact member  7  is connected to a wiring part of the earth circuit on the printed circuit board  20  by way of the lead terminal  7   b . Also the cover  10  is connected to the wiring part of the earth circuit by way of the second contact member  7 . 
     There will be described how to operate the above-described push switch  1  with reference to  FIG. 2 . 
     First, under an initial condition shown by dashed chain lines, the abutment part  9   d  of the operating member  9   b  is in contact with the upper face of the top part of the dome-shaped movable contact  13  across the protecting sheet  14 . In accordance with a synergism of elastic urging force of the movable contact  13  directed upward and the inclined face of the inclined part  10   d , the operating member  9  is urged leftward in this figure (in an opposite direction to the direction that the pressed part  9   a  is pressed), thereby the pressed part  9   a  is projected outward (forward) from the housing  2 . Incidentally, the outer peripheral portion of the movable contact  13  is in contact with the fixed contact  5   a  but the lower face of the top part of the dome-shaped movable contact  13  is away from the fixed terminal  6   a , so that the push switch  1  is placed in the turn-off state. 
     From this state, when the pressed part  9   a  is pressed rightward in this figure, the abutment part  9   d  of the operating member  9   b  is guided downward (perpendicular to the direction that the pressed part  9   a  is pressed) along the inclined part  10   d  of the cover  10 , and presses the upper face of the top part of the dome-shaped movable contact  13  through the protecting sheet  14 . Accordingly, the movable contact  13  is moved downward and the lower face of the top part thereof comes into contact with the fixed contact  6   a . As a result, the fixed contacts  5   a  and  6   a  are electrically connected, and the push switch  1  is placed in the turn-of state. 
     When the operating member  9  is pushed into the space  3  of the housing  2  and the fixed contacts  5   a  and  6   a  are electrically connected, the rear face of the pressed part  9   a  comes in contact with the legs  10   b  and the pressed part  9   a  covers at least parts of the legs  10   b  in order to prevent the legs  10   b  from being deformed forward thereby the engagement pieces  10   c  are disengaged from the engagement projections  12 . With this configuration, the strength of the cover  10  can be eventually increased without increasing the width and thickness of the cover  10  and the legs  10   b . As a result, downsizing of the push switch can be attained. 
     The rear face of the pressed part  9   a  may not come in contact with the legs  10   b  but may be configured to be stopped at such a position that the rear face of the pressed part  9   a  opposes the legs  10   b  across such a minute gap that the deformed legs  10   b  immediately comes in contact with the rear face. 
     From the state, when the pressing against to the pressed part  9   a  is canceled, the movable contact  13  moves upward due to the own elastic restoration force and the push switch  1  is placed in the turn-off state. In accordance with the urging force generated by the restoring action, the abutment part  9   d  of the actuator  9   b  is guided leftward in this figure (the opposite direction to the direction that the pressed part  9   a  is pressed) along the inclined part  10   d , so that the pressed part  9   a  moves forward and returns to the original condition. 
     When the finger of a person who operates the push switch  1  mounted on the printed circuit board  20  installed in an electric apparatus pushes a front face of the pressed part  9   a , static electricity carried by the person may be of the operator is supplied to the operating member  9  through the finger. However, the supplied static electricity is transferred to the earth circuit on the printed circuit board  20  by way of the cover  10  and the second contact member  7 . 
     It is to be noted that although the above described embodiment is a preferable embodiment of the invention, the invention is not limited to this embodiment, but various modifications can be made within a scope not deviating from a gist of the invention. 
     The present invention is applicable to a switch-type electronic device other than the push switch and an electronic device other than the switch-type electronic device as long as it is adapted to be mounted on a circuit board by soldering. 
     The material of the housing  2  is not limited to resin as long as it is insulative. The material of cover  10 , the first contact members  5 ,  6  and the second contact member  7  is not limited to metal as long as they are conductive. 
     The lead terminal  7   b  may not be exposed at one of the opposite side face  2   b  but may be exposed at the front side face  2   e.