Patent Publication Number: US-2021169307-A1

Title: Operation switch, medical device provided with operation switch, and endoscope provided with operation switch

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of PCT/JP2018/029956 filed on Aug. 9, 2018, the entire contents of which are incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an operation switch including an electric switch that is pressed to be turned on, and an elastic operation member elastically deformed when the switch is pressed, a medical device provided with the operation switch, and an endoscope provided with the operation switch. 
     2. Description of the Related Art 
     A medical endoscope generally includes an elongated insertion portion to be inserted into a body cavity, and an operation portion provided in a proximal end side of the insertion portion. 
     An observation optical system and an illumination optical system are provided at a distal end portion of the insertion portion. Some insertion portions are provided with a bending portion that is freely bendable to improve observation performance and insertability into an inside of a subject. Further, some insertion portions are provided with a fluid conduit to feed air/water into the insertion portion or to suction. 
     The operation portion is provided with a bending operation device to bend the bending portion. The operation portion is provided with a plurality of press-button switches being electric switches for instructing stopping of an endoscope image, recording of an endoscope image, changing over of illumination lights, and the like. Further, the operation portion is provided with a fluid control button for controlling air feeding, water feeding, and suctioning. 
     A press type switch device provided to an operation portion main body is illustrated in FIG. 7 or the like of PCT Patent Application No. WO2013/154106. The switch device includes a switch substrate with a switch portion disposed in the operation portion main body and a switch cover to transmit a switch operation of an operator from an outside of the operation portion main body to the switch substrate. 
     The switch cover includes a base, a cylindrical portion, a first deformable portion, a second deformable portion, and a stress transmission portion, for example. The stress transmission portion includes an operation input portion with a projection-shape and a pressing portion to transmit an inputted outer stress to a switch portion. A main portion of the switch cover is formed by integrally molding a flexible resin or the like. One of the three planes constituting the operation input portion is a pressed plane capable of inputting outer stress caused by the pressing of an operator. 
     According to the above-described press type switch device, an operator firstly presses the pressed plane of the switch device and inputs an outer stress to the operation input portion. Then, deformation of the first and the second deformable portions causes the operation input portion to be tilted, and an end portion of the pressing portion contacts the switch portion. As a result, two contacts (not illustrated) of the switch portion are electrically connected to each other, and the switch device is turned on. When the first pressed plane is released from the pressing, the operation input portion stands up and the switch device returns to an off state. 
     In recent years, a medical endoscope is subjected to an autoclave sterilization after use. In the autoclave sterilization, the endoscope is left in a chamber. The endoscope in the chamber is sterilized with autoclave sterilization through a pre-vacuum step, a high-pressure steam sterilization step, and a drying step. After the autoclave sterilization, the endoscope is left in an atmosphere. 
     SUMMARY OF THE INVENTION 
     An operation switch of an aspect of the present invention includes an elastic operation member, a pressing member, and a switch main body. The elastic operation member is formed of an elastic member with an elastic force and includes: a dome portion having a dome shape provided to one end side of the elastic operation member so as to be located in an outer plane side of a housing through-opening provided to a housing in order to allow an inside of the housing and an outside of the housing to communicate with each other; and a circumferential plane portion having a flange provided to the other end side of the elastic operation member. The dome portion is formed in a dome shape in a natural state, configured to be elastically deformed to a balanced state with a predetermined tension, and held in a dome shape different from the natural state. The pressing member moves by deforming a pressing region of the dome portion inward, and presses an electric switch. The switch main body includes a recess for switch in which the electric switch is disposed, a housing hole in which the pressing member is slidably housed, and a central protrusion having an outer circumferential plane around which an inner plane of the circumferential plane portion of the elastic operation member is disposed. 
     A medical device according to an aspect of the present invention includes the operation switch in the housing to be grasped by an operator. 
     An endoscope of an aspect of the present invention includes the operation switch in an operation portion to be grasped by an operator or in a holding base disposed in a proximal end side of the operation portion. 
     An operation switch of an aspect of the present invention includes: an elastic operation member formed of an elastic member with an elastic force including a dome portion formed as a dome shape protruding outward in a natural state, configured to be elastically deformed in a balanced state with a predetermined tension, and held in a dome shape protruding outward and different from the natural state; a compression member configured to apply force along a plane forming the dome portion such that the dome portion is in the balanced state; and a pressing member configured to be moved by the pressed dome portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram for describing a portable endoscope including an operation switch. 
         FIG. 2  is a sectional view of the portable endoscope in  FIG. 1  taken along line Y 2 -Y 2 , and is a diagram for describing a relationship between a holding base and a power switch provided to the holding base. 
         FIG. 3  is a diagram for describing a power switch disposing opening formed in the holding base. 
         FIG. 4  is an exploded view of a main component of the power switch, and is a perspective view for describing an operation cover, a sliding rod, a switch main body, and a ring member. 
         FIG. 5  is an exploded view of the main component of the power switch, and is a perspective view for describing the operation cover, the sliding rod, the switch main body, and the ring member. 
         FIG. 6A  is a diagram illustrating a mounting plate on which the switch main body with a fixed electric switch is disposed. 
         FIG. 6B  is a diagram illustrating the sliding rod disposed to a housing hole of the switch main body. 
         FIG. 6C  is a diagram illustrating the ring member attached to the operation cover housed in a circumferential groove of the switch main body. 
         FIG. 6D  is a diagram illustrating a switch set obtained by further housing a small diameter ring portion of the ring member in the circumferential groove. 
         FIG. 6E  is a diagram for describing a relationship between the switch set and a disposing opening of the holding base. 
         FIG. 6F  is a diagram illustrating that an entire circumference of an outer circumferential portion of a dome portion included by the switch set introduced into the disposing opening is in contact with a boundary portion. 
         FIG. 6G  is an enlarged view of part of  FIG. 6F , and is a diagram for describing a state in which a space is formed between a second opening side end plane and a bottom plane for ring member disposition. 
         FIG. 6H  is a diagram illustrating the switch set reaching a deeper side of the disposing opening against elastic force of the dome portion, and is a diagram for describing a state in which the dome portion is elastically deformed from a natural state. 
         FIG. 7  is a diagram for describing an action of the dome portion having a dome shape different from the natural state by being compressed and elastically deformed. 
         FIG. 8  is a diagram for describing the power switch operated by a finger. 
         FIG. 9  is a diagram for describing a relationship between an operation force amount and a pressing amount. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 
     In the drawings used in the following description, in order to make components recognizable in the drawings, some components are different from each other in terms of scale. That is, the present invention is not limited only to the number of the components, the shape of the components, the size ratio of the components, or the relative positional relationship between the components described in these drawings. 
     An endoscope  1  illustrated in  FIG. 1  is a medical device and is a portable endoscope. Main components of the endoscope  1  include an endoscope main body  2  and an image display portion  3 . 
     The endoscope main body  2  includes an elongated insertion portion  4  and an operation portion  5  grasped by an operator. The operation portion  5  is a housing connected to the proximal end side of the insertion portion  4 . 
     Reference numeral  6  denotes an image display portion holding base (hereinafter, simply referred to as a holding base). The holding base  6  is a housing disposed in the proximal end side of the operation portion  5 . The holding base  6  is connected to the proximal end side of the operation portion  5  by a coupling pipe  6   p.  The inside of the holding base  6  and the inside of the operation portion  5  are connected to each other by the coupling pipe  6   p.    
     The insertion portion  4  is inserted into a subject. The insertion portion  4  includes a distal end portion  4   a,  a bending portion  4   b,  and a flexible tube portion  4   c  in this order from the distal end side. The bending portion  4   b  is bendable in two directions, that is, up and down directions, for example. The flexible tube portion  4   c  has flexibility. 
     The operation portion  5  is provided with a bending operation lever  7  for bending the bending portion  4   b.  The bending operation lever  7  includes a finger hook  7   a  and an arm  7   b.  The arm  7   b  has an L-shape, for example. A finger of an operator is hooked on the finger hook  7   a.    
     The bending portion  4   b  may be configured to be bendable in four directions, that is, up, down, right, and left directions. In this case, the bending operation lever  7  is provided with an up-down bending operation lever and a right-left bending operation lever. 
     Reference numeral  8  denotes a treatment instrument insertion port. The treatment instrument insertion port  8  is connected to a treatment instrument channel (not illustrated) passing through the inside of the insertion portion  4 . The treatment instrument, such as forceps, is guided to the inside of a body from the treatment instrument insertion port  8  passing through the treatment instrument channel. 
     In the present embodiment, a light source such as an LED (not illustrated) for emitting illumination light to the inside of the subject is provided in the operation portion  5  of the endoscope  1 . The illumination light emitted from the light source is irradiated to the inside of the subject from a distal end plane of the distal end portion  4   a  through a bundle of optical fibers provided in the insertion portion  4  (not illustrated). 
     An image pickup apparatus (not illustrated) including an image pickup portion such as a CCD or a C-MOS (not illustrated) and a circuit component (not illustrated) is incorporated in the operation portion  5 , the holding base  6 , or the insertion portion  4 . Further, the operation portion  5  is provided with a suction cap  9  used to suction a liquid such as a body fluid or sputum. A connection tube extending from a suction device (not illustrated) is detachably attached to the suction cap  9 . 
     A first cap is denoted as reference numeral  10  and includes a check valve that opens when the pressure in the operation portion  5  is greater than the outer pressure. Reference numeral  11  denotes an image display portion. The image display portion  11  has an airtight inner space. 
     A monitor  12  and a second cap  13  are provided to the image display portion  11  attached to the holding base  6 . The monitor  12  includes an LCD panel and a cover glass covering a displaying plane of the LCD panel. The second cap  13  includes a vent valve that switches a flow-through state and a shut-off state between the space in the image display portion  11  and the outside thereof. 
     Reference numeral  20  denotes a power switch. In the present embodiment, the power switch  20  is one of operation switches, and is provided to the holding base  6 . Pressing the power switch  20  causes the endoscope  1  to be turned on. 
     A holding base through-opening (housing through-opening) (hereinafter, simply referred to as through-opening)  6   h  that allows a holding base inner space  6 S and the outside thereof to communicate with each other is formed in the holding base  6  as illustrated in  FIG. 2 . The power switch  20  is configured of an operation cover  30 , a sliding rod  40  (pressing member), a switch main body  50 , and a ring member  60 , all of which are integrally disposed in the through-opening  6   h.    
     An electric switch is denoted as reference numeral  70 , and is turned on when the sliding rod  40  moves and presses a movable contact  70   a.  Reference numeral  71  denotes a mounting plate. The mounting plate  71  is fixed at a predetermined position in the inner plane  6   i  of the holding base inner space  6 S. The electric switch  70  is fixed to the mounting plate  71  such that the sliding rod  40  is able to press the movable contact  70   a.    
     The through-opening  6   h  in the holding base  6  illustrated in  FIG. 3  is a power switch disposing opening. Hereinafter, the through-opening  6   h  will be described as a power switch disposing opening  6   h  (simply referred to as disposing opening  6   h ). 
     The disposing opening  6   h  includes a pressing plane exposing portion  6   a  having a first inclined plane  6   as,  a dome portion holding portion  6   b  having a second inclined plane  6   bs  (second pressing plane), a ring member disposing portion  6   c  having a bottomed opening, and a switch main body disposing portion  6   d  in order from the outer plane  6   o  side. 
     Reference numeral a 6   h  denotes a central axis of the disposing opening  6   h.  Reference numeral  6   om  denotes an outer plane opening, and reference numeral  6   im  denotes an inner plane opening. Reference numerals  6   e  and  6   g  denote bottom planes which will be described later, and reference numeral  6   f  denotes a recess which will be described later. 
     The cylindrical operation cover  30 , the solid sliding rod  40 , the switch main body  50 , and the ring member  60  are disposed in the disposing opening  6   h  as illustrated in  FIG. 4  and  FIG. 5 . 
     The switch main body  50  includes a central protrusion  51 , a circumferential groove  52 , and a circular plate portion  53  having a pair of projections  53   a.  The pair of projections  53   a  projects outward from the outer circumferential plane  53   b.  The pair of projections  53   a  is housed in the recess for projections  6   f  formed in the switch main body disposing portion  6   d  of the disposing opening  6   h  illustrated in  FIG. 3 . 
     The central protrusion  51  protrudes from the center of the outward side end plane  53   c  of the circular plate portion  53 . The outward side end plane  53   c  of the circular plate portion  53  is disposed in contact with the bottom plane for main body disposition  6   e  of the main body disposition portion  6   d.    
     The circumferential groove  52  is formed to surround the circumference of the central protrusion  51 . The circumferential groove  52  is set to a predetermined width and depth. An inclined plane  52   c  is provided between an outward inner plane  52   a  and a bottom plane  52   b  of the circumferential groove  52 . 
     The central protrusion  51  has a housing hole  51   h  having a stepped shape along the central longitudinal axis. The housing hole  51   h  is a through-hole having a small diameter hole  51   a  and a large diameter hole  51   b.  Reference numeral  51   c  denotes a stepped plane. The sliding rod  40  is slidably disposed in the housing hole  51   h.    
     Reference numeral  54  in  FIG. 5  denotes a recess for switch. The electric switch  70  fixed to the mounting plate  71  is disposed in the recess for switch  54 . 
     The sliding rod  40  illustrated in  FIG. 4  and  FIG. 5  is rigid. The sliding rod  40  has a small diameter portion  41  and a large diameter portion  42 . The small diameter portion  41  is loosely fitted in the small diameter hole  51   a.  That is, the outer diameter of the small diameter portion  41  is set to be smaller than the inner diameter of the small diameter hole  51   a.    
     On the other hand, the outer diameter of the large diameter portion  42  is set to fit to the inner diameter of the large diameter hole  51   b  in a predetermined degree. A plurality of cutout grooves  44  is formed at equal intervals in the circumferential direction on an outer circumferential plane of the large diameter portion  42 . The cutout groove  44  extends along the central longitudinal axis of the sliding rod  40 . The large diameter portion  42  having the cutout groove  44  of the sliding rod  40  is a switch pressing member capable of smoothly moving forward and backward in the large diameter hole  51   b  of the housing hole  51   h.  Reference numeral  43  denotes a contact plane. The contact plane  43  contacts the stepped plane  51   c.    
     The sliding rod  40  moves in the housing hole  51   h  and the movement stops when the contact plane  43  contacts the stepped plane  51   c.  The distal end plane  41   a  of the small diameter portion  41  contacts the movable contact  70   a  of the electric switch  70 . 
     The elastic force of the movable contact  70   a  causes the sliding rod  40  to be disposed at an initial position. 
     The contact plane  43  is spaced apart from the stepped plane  51   c  when the sliding rod  40  is in the initial position. The head  40   h  of the sliding rod  40  is spaced apart from a sliding rod contact plane  36  of the operation cover  30  by a predetermined distance. 
     The distal end plane  41   a  contacting the movable contact  70   a  moves the movable contact  70   a  against the elastic force in accordance with the movement of the sliding rod  40 . 
     The electric switch  70  is turned on when the contact plane  43  contacts the stepped plane  51   c.  The distal end plane  41   a  of the small diameter portion  41  is a pressing plane. 
     The operation cover  30  is an elastic operation member with a predetermined rubber hardness formed of an elastic member having elastic force, such as elastic rubber or elastic resin. The operation cover  30  is formed in a predetermined cylindrical shape. 
     The operation cover  30  mainly includes a dome portion  31  and a circumferential plane portion  32 . The dome portion  31  forms one end side of the operation cover  30 . The dome portion  31  is disposed on the outer plane opening  6   om  side of the disposing opening  6   h.  The circumferential plane portion  32  forms the other end side of the operation cover  30 . The circumferential plane portion  32  is provided in the inner plane opening  6   im  side connecting to the holding base inner space  6 S of the disposing opening  6   h.    
     Reference numeral  33  denotes a flange portion, and reference numeral  34  denotes a first inclined portion. 
     The dome portion  31  mainly has a dome portion outer surface  31   a  (dome outer surface) and a dome portion outer circumferential portion  31   b  (dome outer circumferential portion). The dome portion outer circumferential portion  31   b  is a portion having the largest outer diameter in the dome portion  31 . The dome portion outer surface  31   a  has a dome shape having a curved plane protruding outward from the one end side of the dome portion outer circumferential portion  31   b.    
     The region of the dome portion outer surface  31   a  indicated by the broken line is a pressing region  35  to be pressed by a finger when the power switch is operated. The pressing region  35  is positioned at a center of the dome portion  31 . 
     The inner plane of the dome portion  31  in the side opposite to the dome portion outer surface  31   a  is a switch contact plane that can contact the end plane of the central protrusion  51 . The switch contact plane is substantially similar to the dome portion outer surface in shape. The area of the inner plane of the dome portion  31  is larger than the area of the dome portion outer surface  31   a.  The region indicated by reference numeral  36  in the switch contact plane corresponds to the sliding rod contact plane  36 . The sliding rod contact plane  36  contacts the head  40   h  of the sliding rod  40 . 
     An outer diameter of the circumferential plane portion  32  is smaller than the outer diameter of the dome portion outer circumferential portion  31   b.  An inner plane  37  of the circumferential plane portion  32  surrounds the outer circumferential plane  51   o  of the central protrusion  51  of the switch main body  50 . The inner plane  37  is close to or in contact with the outer circumferential plane  51   o  of the central protrusion  51 . 
     The flange portion  33  (flange) is provided in an opening  30   m  side of the operation cover  30 . A flange opening side end plane is denoted as reference sign  33   a  and is positioned in the opening  30   m  side. The flange portion  33  is housed in the circumferential groove  52  of the switch main body  50 . The flange opening side end plane  33   a  is disposed on the bottom plane  52   b  of the circumferential groove  52 . 
     Reference numeral  33   b  denotes a flange other end plane. The flange other end plane  33   b  is a plane in the side opposite to the flange opening side end plane  33   a.    
     A first inclined portion  34  has an outer inclined plane  34   a  extending from the dome portion outer circumferential portion  31   b  to the circumferential plane portion  32  of the dome portion  31 . The first inclined portion pressing plane (first pressing plane, see reference numeral  66  in  FIG. 5 ) of the large diameter ring portion of the ring member  60  (reference numeral  63  in  FIG. 4 ,  FIG. 5  and the like), which will be described later, contacts the outer inclined plane  34   a  of the first inclined portion  34 . The outer inclined plane  34   a  is an inclined plane having a predetermined acute angle θ. 
     The ring member  60  is made of resin, for example, and has a through-opening for operation cover (hereinafter, referred to as opening for cover)  61 . The operation cover  30  is disposed in the opening for cover  61 . The ring member  60  has a small diameter ring portion  62  that is a first ring portion and a large diameter ring portion  63  that is a second ring portion. Reference numeral  60   f  denotes a stepped plane. The stepped plane  60   f  is disposed on the outward side end plane  53   c  of the circular plate portion  53 . 
     An inner plane  64  of the opening for cover  61  has a circumferential plane portion contact plane  65  and a first inclined portion pressing plane  66 . The circumferential plane portion contact plane  65  is positioned in the first opening  61   a  side of the small diameter ring portion  62 . The first inclined portion pressing plane  66  is positioned in the second opening  61   b  side of the large diameter ring portion  63 . 
     The first inclined portion pressing plane  66  is a first confining plane of the first pressing portion. The first confining plane is an inclined plane having a predetermined acute angle θ. 
     The small diameter ring portion  62  is housed in the circumferential groove  52  of the switch main body  50 . Specifically, the small diameter ring portion  62  is disposed inside the circumferential groove  52  after the flange portion  33  of the operation cover  30  is housed in the circumferential groove  52 . Thus, a first opening side end plane  62   a  of the small diameter ring portion  62  is disposed on the flange other end plane  33   b.    
     On the other hand, the large diameter ring portion  63  is disposed in the ring member disposing portion  6   c  of the disposing opening  6   h.  Then, the second opening side end plane  63   a  of the large diameter ring portion  63  is disposed in contact with the bottom plane for ring member disposition  6   g.    
     The assembling procedure of the power switch  20  will now be described. 
     An assembly worker places the switch main body  50  on the mounting plate  71  on which the electric switch  70  is fixed as illustrated in  FIG. 6A . The electric switch  70  is provided in a predetermined position in the recess for switch  54 . Thereafter, the assembly worker places the sliding rod  40  in the housing hole  51   h  of the switch main body  50  as illustrated in  FIG. 6B . 
     Next, the assembly worker attaches the ring member  60  to the operation cover  30  as illustrated in  FIG. 6C . At this time, the circumferential plane portion contact plane  65  faces a circumferential outer plane  32   a  of the circumferential plane portion  32 , and the outer inclined plane  34   a  of the first inclined portion  34  is disposed on the first inclined portion pressing plane  66 . 
     Next, as illustrated in  FIG. 6D , the flange portion  33  of the operation cover  30  to which the ring member  60  is attached is housed in the circumferential groove  52  of the switch main body  50 . At this time, the flange opening side end plane  33   a  is disposed on the bottom plane  52   b.  After that, the stepped plane  60   f  of the ring member  60  is disposed on the outward side end plane  53   c,  and the small diameter ring portion  62  is housed in the circumferential groove  52 . At this time, the first opening side end plane  62   a  is disposed on or faces the flange other end plane  33   b.    
     As a result, a switch set s 20  is formed in which the electric switch  70 , the operation cover  30 , the sliding rod  40 , and the ring member  60  are disposed in the switch main body  50 . 
     Next, the assembly worker introduces the switch set s 20  from the inner plane opening  6   im  of the disposing opening  6   h  of the holding base  6  toward the outer plane opening  6   om  as indicated by the arrow in  FIG. 6E . At this time, the assembly worker introduces the switch set s 20  toward the deeper side of the disposing opening  6   h  while observing the positional relationship between the outer plane opening  6   om  and the pressing region  35  of the dome portion  31 . The positional relationship is observed from the outer plane opening  6   om  side of the disposing opening  6   h  of the holding base  6 . 
     Then, the dome portion outer circumferential portion  31   b  side of the dome portion outer surface  31   a  contacts the boundary portion  6   k  between the pressing plane exposing portion  6   a  and the dome portion holding portion  6   b  over the entire circumference as illustrated in  FIG. 6F , and the introduction of the switch set s 20  into the disposing opening  6   h  is temporarily halted. 
     At this time, as illustrated in  FIG. 6G , the second opening side end plane  63   a  of the large diameter ring portion  63  is positioned close to the bottom plane for ring member disposition  6   g  of the ring member disposing portion  6   c.  In other words, the second opening side end plane  63   a  and the bottom plane for ring member disposition  6   g  face each other with a slight space s interposed therebetween. 
     Thereafter, the assembly worker further pushes the switch set s 20  against the elastic force of the operation cover  30  toward the deeper side of the disposing opening  6   h  indicated by arrow Y 6 G. Then, the first inclined portion  34  and the dome portion outer circumferential portion  31   b  positioned on the first inclined portion pressing plane  66  are also moved toward the deeper side. 
     Then, as illustrated in  FIG. 6H , the switch set s 20  reaches the predetermined position in the disposing opening  6   h  while the outer inclined plane  31   o  of the second inclined portion  31   c  positioned between the dome portion outer surface  31   a  and the dome portion outer circumferential portion  31   b  comes into contact with the second inclined plane  6   bs  of the dome portion holding portion  6   b.    
     When the switch set s 20  reaches the predetermined position while the outer inclined plane  31   o  comes into contact with the second inclined plane  6   bs,  the dome portion outer circumferential portion  31   b,  the first inclined portion  34 , and the circumferential plane portion  32  are elastically deformed from the natural state indicated by the broken line in  FIG. 6H . 
     As a result, the outer inclined plane  31   o  of the second inclined portion  31   c  comes into close contact with the second inclined plane  6   bs,  and the inner plane  37  of the circumferential plane portion  32  comes into contact with or comes into close contact with the outer circumferential plane  51   o  of the central protrusion  51 . 
     The outer inclined plane  31   o  of the second inclined portion  31   c  comes into contact with the second inclined plane  6   bs  and is pressed to change into a close contact state. When the change occurs, the second inclined portion  31   c  is compressed in the direction indicated by the broken line arrow and is deformed as illustrated by the solid line from the natural state illustrated by the broken line. 
     That is, the second inclined plane  6   bs  has a function as a second confining plane of the second pressing portion that compresses and deforms the second inclined portion  31   c.    
     When the switch set s 20  reaches the predetermined position, the pressing force to the outer inclined plane  34   a  of the first inclined portion  34  by the first inclined portion pressing plane  66  is maintained, and at the same time the compression of the second inclined portion  31   c  by the second inclined plane  6   bs  is maintained. 
     As illustrated in  FIG. 6G , when the second opening side end plane  63   a  closely faces the bottom plane for ring member disposition  6   g,  a V-shaped confining portion  21  is formed by the first inclined portion pressing plane  66  (first pressing plane) facing the first inclined portion  34  and the second inclined plane  6   bs  (second pressing plane). The ring member  60  having the first inclined portion pressing plane  66  (first pressing plane) and the holding base  6  having the second inclined plane  6   bs  (second pressing plane) are compression members. 
     When the switch set s 20  is pushed toward the deeper into the disposing opening  6   h,  the confining portion  21  causes the outer inclined plane  31   o  of the second inclined portion  31   c  of the dome portion outer surface  31   a  to contact the second inclined plane  6   bs.    
     Further, the confining portion  21  presses the outer inclined plane  31   o  of the second inclined portion  31   c  in contact therewith, and compresses the second inclined portion  31   c  in the direction of the pressing region  35  of the dome portion  31  (direction indicated by broken line arrow) from the outer circumferential end side. 
     With this, the dome portion  31  in the pressing plane exposing portion  6   a  is balanced with a predetermined tension (held in balanced state) and is elastically deformed to a dome shape protruding outward (held in dome shape protruding outward) different from the natural state. The compression member compresses the dome portion  31  toward the center of the dome portion  31  to make the balanced state. 
     After that, the mounting plate  71  is fixed to the inner plane  6   i  of the holding base  6  by a fixing screw (not illustrated). With this, the power switch  20  is disposed to the holding base  6  as illustrated in  FIG. 2  described above without the use of an adhesive agent. Thus, the rubber hardness of the operation cover  30  is maintained without change. That is, in the power switch  20 , the pressing force to the outer inclined plane  34   a  of the first inclined portion  34  by the first inclined portion pressing plane  66  continues to be maintained, and the compression of the second inclined portion  31   c  by the second inclined plane  6   bs  continues to be maintained. 
     Here, the operation of the power switch  20  will be described. 
     The dome portion  31  of the power switch  20  is curved outward in the balanced state with a predetermined tension different from the natural state. The dome portion  31  in the balanced state receives the outside air pressure on the entire surface of the dome portion outer surface  31   a  as illustrated in  FIG. 7  until the pressure difference between the outer air pressure and the pressure in the endoscope, which is the pressure in the dome portion  31 , after the completion of the autoclave sterilization reaches a predetermined pressure P. The outer air pressure is dispersed to p and the balanced state is maintained, and thus, the dome portion  31  maintains the curved shape protruding outward while elastically deforms as illustrated by the dashed-and-double-dotted line. 
     When the pressure difference exceeds P, the balance is broken and the dome portion  31  is retracted. 
     The pressure difference P is set in advance to be higher than the pressure difference Pa in which the switch cover of the press type switch device described in the above-described publication is retracted after the completion of the autoclave sterilization. In addition, the pressure difference P is set in advance to be higher than the pressure difference Pb in which a switch cover having a reduced flexibility is retracted. The reduced flexibility is aimed to avoid a problem that the switch cover is retracted. 
     Therefore, even when the pressure differences Pa and Pb are generated on the dome portion outer surface  31   a,  the dome portion  31  maintains the dome shape different from the natural state. 
     On the other hand, when the user performs observation by the endoscope  1 , the user operates the power switch  20 . The user presses the pressing region  35  of the operation cover  30  with a finger f as illustrated in  FIG. 8 . 
     At this time, the pressing region  35  of the dome portion outer surface  31   a  is pressed as indicated by arrow Y 7  by the pressing force of Pw as illustrated in  FIG. 7 . The dome portion  31  with the predetermined tension different from the natural state maintains the dome shape different from the natural state until the force amount of the pressing force reaches predetermined force amount Pp. 
     In other words, the dome portion  31  maintains curving outward until the force amount of the pressing force reaches Pp as illustrated in  FIG. 9 . 
     The force amount Pp is larger than the initial operation force amount p 1  of the press type switch device described in the above-described publication, and is larger than the initial operation force amount p 2  of the press type switch device avoiding a problem that the switch cover is retracted. 
     As indicated by the broken line in  FIG. 9 , in a press type switch device described in the publication, the electric switch is turned on when the operation force amount Pw reaches the standard value, for example. On the other hand, as indicated by the dashed-and-double-dotted line, in the press type switch device avoiding the problem that the switch cover is retracted, the electric switch is turned on when the operation force amount Pw exceeds the standard value by far. 
     The dome portion  31  is held in the curved shape without elastically deforming until the operation force amount Pw exceeds Pp as illustrated in  FIG. 9 . When the operation force amount Pw exceeds Pp, the balance in the vicinity of the pressing region  35  is broken and the dome portion  31  deforms as indicated by the broken line in  FIG. 7 . 
     When the balance is broken, the sliding rod contact plane  36  of the dome portion  31  is brought closer to the head  40   h  of the sliding rod  40  with a force amount smaller than Pp as indicated by the solid line in  FIG. 9 . After the sliding rod contact plane  36  reaching the head  40   h,  the pressing of the sliding rod  40  by the user begins as indicated by the solid line in  FIG. 9 . 
     As a result, the sliding rod  40  is moved, and the movement of the sliding rod  40  causes the movable contact  70   a  of the electric switch  70  to be deformed and the electric switch  70  is turned on. 
     As indicated by the oblong ellipse in  FIG. 9 , the operation force amount Pw when the electric switch  70  is turned on is set to be equal to or less than a predetermined value. Further, when the user moves the finger f away from the operation cover  30 , the operation cover  30  is restored to the original curved shape, and the movable contact  70   a  returns to the original position and the electric switch  70  is turned off. 
     As described above, the dome portion  31  of the power switch  20  is compressed and is formed into a dome shape curved outward with a predetermined tension different from the natural state so that the dome portion  31  is not retracted until a pressure difference reaches the pressure difference P higher than the pressure differences Pa and Pb. 
     As a result, it is possible to more reliably prevent a problem that the retraction of the dome portion  31  of the power switch  20  causes the power switch  20  to be turned on in the endoscope  1  after the completion of the autoclave sterilization. 
     Further, when the power switch  20  is operated, the initial operation force amount Pp to deform the dome portion  31  is larger than the initial operation force amount pl of the press type switch device described in the above-described publication, and the initial operation force amount p 2  of the press type switch device provided with an improved switch cover that enables to avoid the problem. However, when the power switch  20  is turned on, the initial operation force amount Pp is within the standard value in a similar way as the operation force amount of the press type switch device in the past. 
     As a result, it is possible to achieve a power switch having excellent operability while preventing the switch device from being turned on because of a pressure difference generated between the outer air and the inside of the endoscope during leaving the switch device in an atmosphere after the completion of the autoclave sterilization. 
     Further, in the power switch  20 , when the sliding rod  40  is in the initial position, the head  40   h  of the sliding rod  40  is separated from the sliding rod contact plane  36  of the operation cover  30  by a predetermined distance. The sliding rod  40  is slidably disposed in the housing hole  51   h.    
     With this, when the dome portion  31  of the operation cover  30  is deformed as set in advance, the sliding rod  40  is moved. Thus, the electric switch  70  may be uniformly operated by the operation of the power switch  20 . 
     The pressing force to the outer inclined plane  34   a  of the first inclined portion  34  by the first inclined portion pressing plane  66  continues to be maintained, and the compression of the second inclined portion  31   c  by the second inclined plane  6   bs  continues to be maintained in the power switch  20 . Accordingly, the outer inclined plane  31   o  of the second inclined portion  31   c  comes into close contact with the second inclined plane  6   bs  of the dome portion holding portion  6   b  during the operation of the power switch  20 , and thus, water tightness against the outside is reliably ensured. 
     Note that, in the press type switch device provided with the above-described improved switch cover, the operation force amount exceeds the standard value when the electric switch is turned on as indicated by the dashed-and-double-dotted line in  FIG. 9 . 
     In the present embodiment, the operation switch provided to the holding base  6  of the endoscope  1  serves as the power switch  20 . However, the operation switch is not limited to the power switch of the endoscope  1 , and may be a freeze switch for generating a freeze signal, a release switch for generating a release signal, and an electric switch for outputting an electric signal such as an observation mode changeover switch provided in the operation portion of an endoscope, for example. Further, the operation switch may be a power switch or an electric switch provided to the housing of a medical device other than an endoscope. 
     The present invention is not limited to the embodiments described above, and various changes and modifications can be made without departing from the spirit and scope of the present invention.