Patent Publication Number: US-6664491-B2

Title: Push switch

Description:
FIELD OF THE INVENTION 
     The present invention relates to a small push switch used in various electronic appliances. 
     BACKGROUND OF THE INVENTION 
     In the recent trend of smaller size and higher quality for electronic appliances, push switches and other electronic components are desired to be small, thin, and to generate clear handling feeling. A push switch having a longer operation stroke is demanded. 
     A configuration of a conventional push switch disclosed in Japanese Laid-open Patent No.3-214519 will be explained, referring to FIG.  14  and FIG.  15 . 
     FIG. 14 is a front sectional view of a conventional push switch  5 . In the bottom of a switch case  1  of molded resin box, two outside fixed contacts  2  coupled to a connection terminal  2 A and a central fixed contact  3  coupled to a connection terminal  3 A are fixed by insert molding. A movable contact  4  of elastic thin metal is disposed on the two outside fixed contact points  2 . 
     The movable contact point  4  is made of elastic thin metal plate, and includes a ring-shaped periphery  4 C and a tongue  4 A extending from the periphery  4 C toward its center. The tongue  4 A is folded in an upward slope at a junction  4 B with the periphery  4 C. The periphery  4 C of the movable contact  4  is disposed on the outside fixed contacts  2  to contact with the contacts  2  electrically. The tongue  4 A in the center faces the central fixed contact  3  in this arrangement, providing a switch contact. 
     An elastic element  6  is made of rubber or other elastic material, and has a columnar bar section  6 B at its upper part, and a thin conical section  6 D at its lower part. A drooping section  6 C projecting downward from a inside central part of the conical section  6 D faces the tongue  4 A of the movable contact  4  at a certain gap. An outer lower end  6 A of the conical section  6 D is disposed on the top of the periphery  4 C of the movable contact  4 . 
     An operation element  7  is disposed on the bar section  6 B. The periphery of a lower part  7 A of the operation element  7  is regulated by the inner periphery of a wall  1 A of the switch case  1 , thus allowing the operation element  7  to move up and down without inclination. 
     Two protrusions  7 B on the periphery are engaged with upper and lower grooves  1 B provided in the inner periphery of the wall  1 A of the switch case  1 , respectively. The operation element  7  is locked so as not to rotate or slip out upward. A protrusion  7 C projecting upward from the switch case  1  is an operation part. 
     An operation of the push switch  5  will be explained below. 
     The protrusion  7 C of the operation element  7  is pushed during the switch being turned off as shown in FIG. 14, and then, the operation element  7  pushes the elastic element  6  in the switch case  1 . This operation deforms the conical section  6 D of the elastic element  6 , and generates a clear click feel at the time of the deformation. Simultaneously, the drooping section  6 C of the elastic element  6  pushes down the tongue  4 A into the center of the movable contact  4 , and the lower side of the tongue  4 A contacts with the central fixed contact  3 . And the outside fixed contacts  2  and the central fixed contact point  3 , that is, the two connection terminals  2 A and  3 A then conduct with each other. 
     Then, when a pushing force to the operation element  7  is removed, the elastic element  6  and movable contact  4  return to an initial state with their own elastic restoring force, and the two connection terminals  2 A and  3 A opens again. 
     The push switch  5  installed in an electronic appliance will be explained. FIG. 15 is a front view of a conventional push switch installed in an electronic appliance. The push switch  5  is disposed on a wiring board  8  with the connection terminals  2 A and  3 A connected electrically at the lower side by, e.g. soldering, and is placed immediately beneath an operation button  9  fitted to a case  10  of the appliance corresponding to the position of the operation element  7 . 
     The interval between the lower side of the operation button  9  and the upper side of the wiring board  8  is determined according to the height of the push switch  5 . 
     In the conventional push switch  5 , however, due to fluctuations of components and their combination in the electronic appliance including the switch, or to an installing state of the push switch  5 , it is difficult to set the interval between the lower side of the operation button  9  and the upper side of the wiring board  8  to be the height of the push switch  5 . If the interval is too wide, a gap between the operation button  9  and the upper side of the push switch  5  makes the operation button  9  loose. If the interval is too narrow, on the other hand, the operation button slightly pushes the operation element  7  of the push switch  5 , and this makes the sensation of manipulation of the push switch  5  dull. 
     SUMMARY OF THE INVENTION 
     The push switch can absorb fluctuations of components and their combination of an electronic appliance, and is prevented from looseness in an operation button of the electronic appliance including the switch, thus maintaining a clear manipulation feeling. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front sectional view of a push switch according to a first exemplary embodiment of the present invention. 
     FIG. 2 is a perspective exploded view of the push switch according to the first embodiment. 
     FIG. 3 is a front sectional view of the push switch according to the first embodiment. 
     FIG. 4 is a front sectional view of the push switch according to the first embodiment. 
     FIG. 5 is a diagram showing the relation between an operating distance and an operating force for the push switch according to the first embodiment. 
     FIG. 6 is a sectional view of the push switch installed in an electronic appliance according to the first embodiment. 
     FIG. 7A to FIG. 7J are partial outline perspective views of another push switch according to the first embodiment. 
     FIG. 8 is a front sectional view of a push switch according to a second exemplary embodiment of the invention. 
     FIG. 9 is a perspective exploded view of the push switch according to the second embodiment. 
     FIG. 10 is a front sectional view of the push switch according to the second embodiment. 
     FIG. 11 is a front sectional view of the push switch according to the second embodiment. 
     FIG. 12 is a front sectional view of another push switch according to the second embodiment. 
     FIG. 13 is a front sectional view of the push switch installed in an electronic appliance according to the second embodiment. 
     FIG. 14 is a front sectional view of a conventional push switch. 
     FIG. 15 is a front view of the conventional push switch installed in an electronic appliance. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     (Exemplary Embodiment 1) 
     FIG. 1 is a front sectional view of a push switch according to a first exemplary embodiment of the present invention, and FIG. 2 is an exploded perspective view of the switch. 
     In an inner bottom  11 B of a resin-made switch case  11  of a box shape, a central fixed contact  12  and two outside fixed contacts  13  are disposed at symmetrical positions thereof being fixed by insert molding. The contacts are exposed nearly at the same heights. Connection terminals  12 A and  13 A communicating with the fixed contacts  12  and  13 , respectively, are drawn out of a side wall of the case. A columnar crimping protrusion  11 A is provided on an upper side of the switch case  11 . A movable contact  14  made of elastic thin metal plate includes a periphery  14 A of a circular ring shape, a tongue  14 B provided in the center of the contact, and a linkage  14 C linking the periphery  14 A and the tongue  14 B. The tongue  14 B is folded with an upward inclination at the linkage  14 C. In the movable contact  14 , the periphery  14 A is mounted on the outside fixed contact  13  on the switch case  11 . The tongue  14 B faces the central fixed contact  12  at a certain interval. 
     An elastic element  15  made of elastic insulating material includes an upward bar section  15 C and a conical section of a thin wall opening downward both being formed integrally in its lower part. A straight groove is provided in the center of the upper side of the bar section  15 C, and the other portion functions as a first deforming section  15 E. The conical section disposed in the lower part of the bar section  15 C functions as a second deforming section  15 A. The conical section as the second deforming section  15 A includes a drooping section  15 D projecting downward in its inside. 
     The elastic element  15  has its lower end portion  15 B of conical section disposed on the periphery  14 A of the movable contact  14 , and the movable contact  14  electrically conducts with the outside fixed contact  13  at its downward side. 
     When the first deforming section  15 E pushes the elastic element  15  down to deform, the first deforming section  15 E deforms by compressing elastically, and then, the second deforming section  15 A, i.e., a conical section of a thin wall buckles and deforms. That is, the width and depth of the groove are determined, so that a force for deforming the first deforming section  15 E may be smaller than a force for deforming the second deforming section  15 A. 
     A cover  16  has a box shape opening downward, and has a central hole  16 A in the center of its upper side. A crimping bump  11 A on the upper side of the switch case  11  is inserted in a crimping hole  16 B formed in a downward flange surface, and the upper part of crimping bump  11 A is crushed to be crimped, and is fixed to the switch case  11 . 
     While the cover  16  is fixed, the bar section  15 C of the elastic element  15  projects upward from the central hole  16 A, and the upper side of the lower end portion  15 B of the elastic element  15  is pushed to contact elastically with the periphery  14 A of the movable contact  14  at the lower end side of the cover  16 . An elastic force maintains a stable electrical conduction of the lower side of the periphery  14 A and the outside fixed contact  13 . The elastic force holds the elastic element  15  so as not to rotate or slip out upward. 
     An operation of the push switch will be explained. 
     In case that the switch is turned off, as shown in FIG. 1, when the elastic element  15  is pushed down, only the first deforming section  15 E of the upper part of the elastic element  15  deforms elastically as shown in FIG.  3 . The deformation corresponds to a first deforming stage in FIG. 5, which shows the relation between an operating distance and an operating force. After the first deforming section  15 E deforms, when a further pressing force is applied, the second deforming section  15 A of thin wall conical section of the elastic element  15  buckles to deform, thereby creating a click feel. 
     The lower end side of the drooping section  15 D at the inside of the second deforming section  15 A pushes the tongue  14 B of the movable contact point  14  down to have the tongue  14 B contact with the central fixed contact  12  on the bottom of the switch case  11 . As a result, the central fixed contact  12  and outside fixed contacts  13 , that is, the connection terminals  12 A and  13 A conduct with each other, and the switch is turned on, as shown in FIG.  4 . The stroke from the beginning of deformation of the second deforming section  15 A in the thin wall conical section until the switch is turned on corresponds to the second deforming stage shown in FIG.  5 . 
     When the pressing force on the elastic element  15  is removed, the elastic element  15  and movable contact  14  return to the initial state shown in FIG. 1 by their own elastic restoring force, and the switch is turned off. 
     FIG. 6 is a sectional view of the push switch according to the embodiment installed in an electronic appliance. Being turned off, the push switch is disposed, so that the elastic element  15  may be positioned immediately beneath an operation button  19  provided in a case  18  of the electronic appliance. 
     A switch mounting interval between the upper side of the wiring board  17  on which the push switch is installed and the lower side of the operation button  19  varies according to dimension or combination state of the components of the electronic appliance. In this embodiment, the switch mounting interval is slightly smaller than the height of the push switch. Therefore, the push switch is installed so that the first deforming section  15 E in the upper part of the elastic element  15  abuts on the lower side of the operation button  19 , being deforming. This dimensional arrangement absorbs fluctuation of the switch mounting interval with the first deforming section  15 E provided in the upper side of the bar section  15 C of the elastic element  15 , thus eliminating looseness of the operation button  19  of the electronic appliance. 
     If the switch mounting interval is smaller than the maximum deforming dimension of the first deforming section  15 E of the elastic element  15 , the second deforming section  15 A of the conical section of the elastic element  15  does not deform. This prevents the handling feeling of the push switch from being influenced due to excessive pushing of the elastic element  15 . 
     Thus, according to the embodiment, fluctuation due to components of the electronic appliance and their combination can be absorbed, looseness of the operation button  19  does not occur, and a push switch maintaining a favorable operation feeling is obtained. 
     It is important to set the switch mounting interval properly in consideration of the mounting of the push switch in relation to the wiring board  17 . 
     In the foregoing explanation, the first deforming section  15 E of the push switch is the bar section  15 C having a straight groove in the elastic element  15 , but it may be formed as shown in FIG. 7A to FIG.  7 J. FIG. 7A shows a straight convex shape  15   d . FIG. 7B shows a straight convex shape  15   d  having a circular convex part  15   e  at its center. FIG. 7C shows a concave shape  15   f , a shape reverse to that shown in FIG.  7 B. FIG. 7D shows a ring-shaped protruding shape  15   g . FIG. 7E shows a circular convex part  15   h  only at its center. FIG. 7F shows a cross-shaped convex shape  15   i  symmetrical about its center. FIG. 7G shows a cross concave shape  15   j  reverse to that shown in FIG.  7 F. FIG. 7H shows a convex shape  15   k  having cross shape and circular shape. FIG. 71 shows a concave shape  151  reverse to that shown in FIG.  7 H. FIG. 7J shows a concentric pointed shape  15   m  in which the bar section becoming smaller in diameter toward its upper side. 
     These shapes may be combined, and the configuration is not particularly defined as far as the first deforming section maintains a specified deforming amount and deforms elastically with a force smaller than a force for deforming the second deforming section. 
     (Exemplary Embodiment 2) 
     FIG. 8 is a front sectional view of a push switch accorfing to a second exemplary embodiment of the invention, and FIG. 9 is an exploded perspective view of the switch. In an inner bottom of a central concave portion of a square switch case  21  made of insulating resin, a central fixed contact  22  and two outside fixed contacts  23  is disposed at symmetrical positions, being fixed by insert molding while exposing nearly at the same height. Connection terminals  22 A,  23 A communicating with the fixed contacts  22  and  23 , respectively, are drawn out outward of a side wall of the case, and a columnar crimping bump  21 A is provided at the upper side corner. 
     In a movable contact  24 , similarly to the contact point  14  of embodiment 1, a periphery  24 A of a circular ring shape is disposed on the outside fixed contact  23  of the switch case  21 , and a tongue  24 B folded upward at a linkage  24 C in this state and disposed in the center of the outer periphery  24 A. The tongue  24 B faces the central fixed contact  22  at a certain interval. 
     An elastic element  25  made of insulating elastic material includes an upper conical section  25 C and a thin wall conical section opening downward formed integrally in its lower part. The elastic element  25  has a step  25 F in the middle position of the bar section  25 C. From the step  25 F, its upper part has a circular convex shape having a slightly smaller diameter than the bar section  25 C. 
     The circular convex portion functions as a first deforming section  25 E, and the conical section in the lower part of the bar section  25 C functions as a second deforming section  25 A. When the elastic element  25  is pushed down and deformed, the first deforming section  25 E in the upper part of the bar section  25 C is elastically compressed and deformed, and then the second deforming section  25 A of thin wall conical section buckles to deform. That is, the diameter and height of the circular convex portion are defined so that a force for deforming the first deforming section  25 E may be smaller than a force for deforming the second deforming section  25 A. 
     Similarly to embodiment 1, the elastic element  25  has a drooping section  25 D in the inside of the conical section, and the lower end portion  25 B of the conical section is disposed on the periphery  24 A of the movable contact  24 . In this configuration, the drooping section  25 D faces the tongue  24 B of the movable contact  24  at a certain interval. 
     An operation element  26  is a resin-made box opening downward having a central hole  26 C in the center of its upper side. The operation element  26  has two engaging portions  26 D each having a convex shape in a vertical direction at a specified width outward of a side wall  26 B and stopping pawls  26 A for preventing the element from slipping out. The pawls are provided at the lower end of the side wall  26 B of positions orthogonal to the engaging portions  26 D at symmetrical positions about the center of the central hole  26 C. 
     The operation element  26  is disposed on the elastic element  25 , having the first deforming section  25 E of the elastic element  25  project upward through the central hole  26 C in the center of its upper side. The peripheral lower side  26 E of the central hole  26 C pushes the step  25 F of the bar section  25 C of the elastic element  25 . 
     The size of the central hole  26 C of the operation element  26  is defined, so that the first deforming section  25 E of the elastic element  25  may not contact with the inner peripheral wall of the central hole  26 C even if being elastically compressed to be positioned flush with the upper side of the operation element  26 . 
     In a tubular resin-made linkage  27 , the upper part of the operation element  26  projects upward through a center hole  27 A. A lower crimping notch  27 B of the linkage  27  is crimped and fixed to the crimping protrusion  21 A at the upper side corner of the switch case  21 , and is fitted to the switch case  21 . 
     The linkage  27  has, at its inner wall, a groove  27 C penetrating in the vertical direction corresponding to the engaging portion  26 D of convex shape provided in the side wall  26 B of the operation element  26 . The engaging portion  26 D is engaged with the groove  27 C without looseness, thus allowing the operation element  26  to be smoothly guided vertically. In an ordinary state in which a pushing force is not applied as shown in FIG. 8, the stopping pawl  26 A of the operation element  26  stops at the lower side around the center hole  27 A, and this prevents the operation element  26  from slipping out. 
     An engaging area between the groove  27 C and engaging portion  26 D is not illustrated in the sectional view in FIG.  8 . 
     In the side wall downward from the stopping pawl  26 A of the linkage  27 , a recess  27 D is formed toward radially. When moving downward of the operation element  26 , the stopping pawl  26 A can move along recess  27 D without obstacle. At the side of the recess  27 D, the stopping pawl  26 A moves while having its side guided. That is, the engaging portions  26 D and stopping pawl  26 A of the operation element  26  are regulated in their movement in the vertical direction by the groove  27 C and recess  27 D, and prevents the operation element  26  from rotation and upward slip-out. 
     An operation of the push switch according to this embodiment will be explained. 
     In an ordinary state in which a pushing force is not applied as shown in FIG. 8, the first deforming section  25 E of the elastic element  25  projecting through the upper side of the operation element  26  is pushed by a pushing force applied through an operation button (not shown) of an electronic appliance. The button is slightly larger than the central hole  26 C of the operation element  26 . As a result, as shown in FIG. 10, the first deforming section  25 E is compressed and deforms elastically until the push button abuts on the upper side of the operation element  26 . The deforming at this moment corresponds to the first deforming stage in FIG.  5 . 
     Upon being further pushed down, the operation element  26  is pushed by the operation button, and the operation element  26  straightly moves down while the engaging portions  26 D and stopping pawl  26 A are guided by the groove  27 C and side of the recess  27 D. Simultaneously, the peripheral lower side  26 E of the central hole  26 C applies a downward pushing force to the step  25 F of the bar section  25 C of the elastic element  25 . 
     When the pushing force to the step  25 F exceeds a predetermined value, the second deforming section  25 A in the thin wall conical section of the elastic element  25  buckles to deform, and generates a click feel. Simultaneously, the lower end side of the drooping section  25 D in the inside pushes the tongue  24 B of the movable contact point  24  down to have the tongue contact with the central fixed contact  22  on the switch case  21 . Then, the central fixed contact  22  and outside fixed contacts  23 , that is, the connection terminals  22 A and  23 A conduct with each other, thus having the switch turned on, as shown in FIG.  11 . 
     In this explanation, the stroke from beginning of the deformation of the second deforming section  25 A until the switch is turned on corresponds to the second deforming stage in FIG.  5 . 
     When the switch according to this embodiment is mounted, similarly to embodiment 1, in consideration of fluctuations of dimensions and combination of components of the electronic appliance, only the first deforming section  25 E of the elastic element  25  deforms slightly. This arrangement has the operation button of the electronic appliance positioned at a predetermined clearance against the operation element  26 . This eliminates looseness of the operation button. 
     Since the first deforming section  25 E is deformed by a smaller force than the second deforming section  25 A of the conical section of the elastic element  25 , the push switch can be installed while having a desired operation feeling. 
     Thus, the switch of the embodiment, similarly to embodiment 1, can be installed while absorbing fluctuations of components of the electronic appliance and their combination, is prevented from looseness of operation button, and generates a favorable operation feeling. 
     If the operation button of the electronic appliance has a hinge shape and is pressed obliquely in the switch of the embodiment, the operation element  26  is guided by the linkage  27 , and can be moved up and down smoothly. Therefore, the switch generates a favorable feeling stably at its manipulation. 
     According to the embodiment, the first deforming section  25 E of the elastic element  25  projects upward through the central hole  26 C of the operation element  26 . However, as shown in a sectional view of another switch in FIG. 12, the upper side of an elastic element  28  may be covered with an operation element  29 . This switch can be installed, while having only a first deforming section  28 A deform slightly. At this moment, a silencing measure may preferably be employed for its manipulation. 
     The push switch of the embodiment can be used in a operation unit for telephoto imaging operation or wide-angle imaging operation at a zoom operation unit of a video camera, as shown in a front view of the switch installed in an electronic appliance shown in FIG.  13 . 
     In this case, two push-ON switch are arranged and soldered on a wiring board  30 , and an operation button  31  of seesaw action for pushing the push switches is provided thereon in a case  32  of the electronic appliance. 
     In this case, when changing over from telephoto imaging operation to wide-angle imaging operation, or from wide-angle imaging operation to telephoto imaging operation, the lower side of the operation button  31  collides against an operation plane of the push switch. This generates a colliding noise, which is recorded together with an image. In the push switch of the embodiment shown in FIG. 8, the first deforming section  25 E in the upper part of the elastic element  25  projects to the upper part of the operation element  26 . Therefore, the lower side of the operation button  31  collides against the first deforming section  25 E of the elastic element  25 , so that the first deforming section  25 E functions as a shock absorber. This prevents the colliding noise from being generated. Even if the operation button  31  is pushed obliquely to press the push buttons, the switch of the embodiment assures a smooth and favorable operation since the operation element  26  moves up and down smoothly. 
     Thus, the push switch of the embodiment does not require a cushion member adhered to the upper or lower side of the operation button, the colliding noise can be eliminated easily, and its operation efficiency is excellent.