Abstract:
A helmet includes a common unlocking member for commonly unlocking a pair of right and left locking mechanisms that lock a subsidiary cap portion at a lower position where it covers the chin of a helmet wearer. A common tractive flexible wire transmits forward unlocking movement of the unlocking member commonly to movable locking members of the pair of right and left locking mechanisms. The intermediate portion of the common tractive flexible wire is engaged by the wire engaging portion of the unlocking member. With this helmet, in spite that the mechanism for unlocking the locked subsidiary cap portion is comparatively simple, the unlocking mechanisms can be operated quickly and smoothly.

Description:
TECHNICAL FIELD 
     The present invention relates to a helmet which has a cap-shaped head protecting body, worn by the helmet wearer such as the rider of a motor cycle to protect his/her head, and having a cap-shaped main cap portion and a subsidiary cap portion attached to the main cap portion to be substantially vertically movable so as to selectively cover the chin of the helmet wearer. 
     BACKGROUND OF THE INVENTION 
     As vehicle helmets worn by the rider of a motor cycle or the like, a full-face-type helmet and a jet-type helmet are conventionally known. In the full-face-type helmet, a chin cover for covering the chin of the helmet wearer is integrally formed with the head protecting body. In the jet-type helmet, no chin cover is formed on the head protecting body so as to expose the face of the helmet wearer almost entirely. Another full-face-type helmet (to be referred to as a “full-face-type helmet serving also as a jet-type helmet” hereinafter) is also conventionally known. In this full-face-type helmet, the head protecting body is formed of a main cap portion having almost the same shape as that of the head protecting body of a jet-type helmet, and a subsidiary cap portion attached to the main cap portion to be substantially vertically pivotal so as to selectively cover the chin of the helmet wearer, so that the helmet can have the functions of both a full-face-type helmet and a jet-type helmet. 
     In the conventional full-face-type helmet serving also as the jet-type helmet, when the subsidiary cap portion is at the lower position, it serves as a chin covering means. When the subsidiary cap portion is at the upper position, a large window formed in the main cap portion is opened, and the head protecting body accordingly has no chin covering means, in the same manner as in the jet-type helmet. When the wearer wearing the full-face-type helmet serving also as the jet-type helmet is driving a motor cycle at high speed, the helmet is worn with its subsidiary cap portion being lowered to the lower position, in order to prevent a large wind pressure from acting on the wearer&#39;s chin and its vicinity. The helmet is provided with a subsidiary cap portion locking mechanism for locking the subsidiary cap portion at the lower position with respect to the main cap portion, so that the subsidiary cap portion does not undesirably move upward by a large impact or wind pressure during high-speed driving. The subsidiary cap portion is provided with an unlocking means or member in order to unlock the subsidiary cap portion locked at the lower position by the subsidiary cap portion locking mechanism. 
     Such a conventional full-face-type helmet serving also as the jet-type helmet is disclosed in European Patent No. 518,178 as well. In the helmet disclosed in this reference (to be referred to as “the first known helmet” hereinafter), when a release lever serving as the unlocking member is pressed for unlocking, a force which moves the subsidiary cap portion from the lower position to the upper position automatically acts on the subsidiary cap portion. In other words, when the release lever is pressed upward, the subsidiary cap portion locked at the lower position is unlocked. Therefore, when the release lever is pressed upward to unlock the locked subsidiary cap portion, the subsidiary cap portion locked by the locking mechanism is unlocked. Also, the subsidiary cap portion can be started to move from the lower position to the upper position by only successively pressing the release lever. Hence, the wearer can unlock the locked subsidiary cap portion and move the unlocked subsidiary cap portion upward quickly and continuously by only pressing the release lever. 
     In the first known helmet as described above, assume that, while the wearer drives the motor cycle at high speed, for example, he erroneously presses the release lever upward so as to slightly move a shield plate (attached to the subsidiary cap portion to be able to open/close the window opening formed in the front surface of the head protecting body of the helmet), so that the window opening closed by the shield plate may be slightly opened. Alternatively, assume that a foreign matter accidentally abuts against the release lever from below. Then, the subsidiary cap portion locked at the lower position is unlocked, and undesirably moves upward from the lower position for a certain degree. A large wind pressure then can directly act on the wearer&#39;s chin, causing inconveniences for the wearer in driving the motor cycle. 
     In the first known helmet as described above, when an operation lever connected to the release lever through a wire causes a movable locking member made of a spring member to move forward against the spring force, the locking mechanism is unlocked. In spite that the structure of the mechanism for unlocking the subsidiary cap portion locked by the locking mechanism is not very simple, the subsidiary cap portion might not be unlocked or inversely locked by the locking mechanism quickly and smoothly. 
     The conventional full-face-type helmet serving also as the jet-type helmet, as described above, is disclosed in German Patent Laid-Open No. 19,612,724 as well. In the helmet (to be referred to as “the second known helmet” hereinafter) disclosed in this reference, when the release tap serving as the unlocking means is pressed for unlocking, a force opposite to a force that moves the subsidiary cap portion from the lower position to the upper position acts on the subsidiary cap portion. In other words, when the release tap is pressed downward, the subsidiary cap portion locked at the lower position is unlocked. Even when the release tap is continuously pressed, it is not sufficient to move the subsidiary cap portion from the lower position to the upper position. Therefore, when the wearer is driving the motor cycle at high speed, the subsidiary cap portion does not move upward from the lower position erroneously or accidentally, and accordingly large wind pressure will not substantially, directly act on the helmet wearer&#39;s chin. 
     In the second known helmet as described above, the movable locking member is constituted by an arcuated operation lever formed with the release tap at its central portion. The operation lever is pivotally, axially supported on the auxiliary cap portion at the right and left portions. Also, a pair of right and left engaging recesses are formed in the right and left end portions of the operation lever. When a pair of right and left lock pins provided to the main cap portion relatively engage with these engaging recesses, the subsidiary cap portion is locked on the main cap portion. When the helmet wearer holds the release tap with his fingers and moves it downward, the operation lever pivots forward to disengage the lock pins relatively from the engaging recesses, thereby unlocking the locked subsidiary cap portion. Therefore, in the second known helmet as well, in spite that the structure of the mechanism for unlocking the subsidiary cap portion locked by the locking mechanism is not very simple, the subsidiary cap portion might not be unlocked or inversely locked by the locking mechanism quickly and smoothly. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to correcting the drawbacks described above of the conventional full-face-type helmet serving also as the jet-type helmet with a very simple arrangement very effectively. 
     It is, therefore, the main object of the present invention to provide a helmet in which, in spite that the mechanism for unlocking the subsidiary cap portion locked on the main cap portion with the locking mechanism is comparatively simple, the unlocking operation and the opposite locking operation can be performed quickly and smoothly. 
     It is another object of the present invention to provide a helmet with which when the wearer is driving a motor cycle at high speed, the subsidiary cap portion will not move upward from the lower position erroneously or accidentally, and large wind pressure will not substantially, directly act on the helmet wearer&#39;s chin. 
     Therefore, the present invention relates to a helmet including a cap-shaped head protecting body to be worn by a helmet wearer on his/her head, the head protecting body having a main cap portion and a subsidiary cap portion attached to the main cap portion to be substantially vertically movable so as to selectively cover a chin of the helmet wearer, the head protecting body being provided with first and second locking mechanisms for respectively locking left and right sides of the subsidiary cap portion with respect to the main cap portion when the subsidiary cap portion is at a lower position to cover the chin, and the head protecting body being also provided with a common unlocking member which is operated forward to commonly unlock the subsidiary cap portion locked by the first and second locking mechanisms. This helmet is provided with a common tractive flexible wire for commonly transmitting forward movement of the unlocking member to first and second movable locking members of the first and second locking mechanisms. One end portion of the wire is connected to the first movable locking member, and the other end portion of the wire is connected to the second movable locking member. The unlocking member is provided with a wire engaging portion, and an intermediate portion of the wire is engaged by the wire engaging portion. 
     The above and other objects, features and advantages of this invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the entire portion of a helmet in an ordinary worn state in the first embodiment in which the present invention is applied to a full-face-type helmet serving also as a jet-type helmet; 
     FIG. 2 is a right side view of the entire portion of the helmet shown in FIG. 1 in an ordinary worn state; 
     FIG. 3 is a right side view of the entire portion of the helmet shown in FIG. 1 with the subsidiary cap portion raised; 
     FIG. 4 is a longitudinal sectional partial view, taken along the center, of the helmet shown in FIG. 2, which explains the subsidiary cap portion locking mechanism and from which the backing member and rim member for the subsidiary cap portion are omitted; 
     FIG. 5 is a view similar to FIG. 4, showing a state the release button is depressed; 
     FIG. 6 is a view similar to FIG. 4, showing a state wherein the subsidiary cap portion is slightly raised from the state shown in FIG. 5; 
     FIG. 7 is a perspective view of the release button and a holding mechanism for it shown in FIG. 4; 
     FIG. 8 is an exploded perspective view of the release button and the holding mechanism for it shown in FIG. 7; 
     FIG. 9 is a longitudinal sectional view, taken along the center, of the release button and the holding mechanism for it shown in FIG. 7; 
     FIG. 10 is a perspective view of the entire portion of a helmet in an ordinary worn state in the second embodiment in which the present invention is applied to a full-face-type helmet serving also as a jet-type helmet; 
     FIG. 11 is a right side view of the entire portion of the helmet shown in FIG. 10 in an ordinary worn state; 
     FIG. 12 is a right side view of the entire portion of the helmet shown in FIG. 10 with the subsidiary cap portion raised; 
     FIG. 13 is a longitudinal sectional partial view, taken along the center, of the helmet shown in FIG. 11, which explains the subsidiary cap portion locking mechanism and from which the backing member and rim member for the subsidiary cap portion are omitted; 
     FIG. 14 is a view similar to FIG. 13, showing a state wherein the release button is depressed; 
     FIG. 15 is a view similar to FIG. 13, showing a state wherein the subsidiary cap portion is slightly raised from the state shown in FIG. 14; 
     FIG. 16 is a sectional view taken along a line XVI—XVI in FIG. 13; 
     FIG. 17 is a perspective exploded view of the main part of the right subsidiary cap portion locking mechanism shown in FIG. 13; 
     FIG. 18 is a perspective view of the release button and a holding mechanism for it shown in FIG. 13; 
     FIG. 19 is an exploded perspective view of the release button and the holding mechanism for it shown in FIG. 18; 
     FIG. 20 is a longitudinal sectional view, taken along the center, of the release button and the holding mechanism for it shown in FIG. 18; 
     FIG. 21 is a sectional view taken along a line XXI—XXI in FIG. 11; and 
     FIG. 22 is a sectional view taken along a line XXII—XXII in FIG.  12 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiments in which the present invention is applied to a full-face-type helmet serving also as a jet-type helmet will be described with reference to the accompanying drawings. 
     First Embodiment 
     The first embodiment in which the present invention is applied to a full-face-type helmet serving also as a jet-type helmet will be described first with reference to FIGS. 1 to  9 . 
     As shown in FIGS. 1 to  3 , a full-face-type helmet  1  serving also as a jet-type helmet is made up of a full-face-type cap-shaped head protecting body  2 , a shield plate  4 , and a pair of right and left chin straps (not shown). Note that the full-face-type cap-shaped head protecting body  2  is to be worn on the head of a helmet wearer, e.g., the rider of a motor cycle, and serves as a jet-type head protecting body as well. The shield plate  4  can open/close a window opening  3  formed in the front surface of the full-face-type head protecting body  2  to oppose the portion between the forehead and chin of the wearer (i.e., almost the central portion of the face). The chin straps are attached to the inner surface portions of the full-face-type head protecting body  2 . 
     As is conventionally known, the head protecting body  2  has a main cap portion  5  and a subsidiary cap portion  6 . The main cap portion  5  can have almost the same shape as that of the cap portion of a jet-type helmet. The subsidiary cap portion  6  is attached to the main cap portion  5  on the right and left sides with a pair of right and left attaching screws  7  serving as axial support means, so as to be reciprocally pivotal. Accordingly, a large window  8  is formed in the main cap portion  5  to be defined by a large notch extending upward from the lower end of the front surface of the main cap portion  5 . As is conventionally known, the subsidiary cap portion  6  has a chin cover  6   a  and a pair of right and left ears  6   b .The chin cover  6   a  is arcuated to expand forward. The ears  6   b  extend from the right and left ends of the chin cover  6   a  and are axially supported on the right and left sides of the main cap portion  5  with a pair of right and left attaching screws  7  to be reciprocally movable. The subsidiary cap portion  6  is formed with a large window  15  defined by a large notch extending downward from the upper end of its front surface. When the subsidiary cap portion  6  pivots downward with respect to the main cap portion  5  to be located at the lower position (the state shown in FIGS.  1  and  2 ), it serves as a chin covering means for covering the wearer&#39;s chin to close the lower portion of the window  8 . Hence, the upper portion of the window  8  defines the window opening  3 . The window opening  3  is formed of a region surrounded by the rim of the window  8  of the main cap portion  5  and the rim of the window  15  of the subsidiary cap portion  6 . 
     As is conventionally known, the shield plate  4  can be made of a transparent or translucent hard material such as polycarbonate or another type of hard synthetic resin. The shield plate  4  is reciprocally pivotally attached to the subsidiary cap portion  6  at the right and left sides with a pair of right and left attaching screws  9  serving as axial support means. When the subsidiary cap portion  6  is at the lower position to serve as the chin covering means (the state shown in FIGS.  1  and  2 ), the shield plate  4  closes the window opening  3  at the backward position (i.e., the lower position); and opens the window opening  3  at the forward position (i.e., the upper position). 
     As is conventionally known, the main cap portion  5  can be made up of a jet-type outer shell  11 , a rim member  12  having a substantially U-shaped section, and a backing member (not shown) for the main cap portion. The outer shell  11  forms the outer wall of the main cap portion  5 . Note that the rim member  12  has a substantially E-shaped section at the upper end portion of the window  8 . The rim member  12  has a substantially U-shaped section at the reminding portion of the window  8  except the upper end portion and is fixed to the outer shell  11  throughout the end portion of the outer shell  11  with an adhesive or the like. The backing member is brought into contact with the outer shell  11  to be fixed to it in contact with the inner surface of the outer shell  11  with an adhesive or the like. As is conventionally known, the outer shell  11  can be made of a composite material. More specifically, the outer shell  11  can be formed by lining the inner surface of a strong shell body made of a hard synthetic resin, e.g., FRP, with a flexible sheet such as an unwoven fabric. As is conventionally known, a portion of the rim member  12  having the substantially U-shaped section can be made of a soft synthetic resin such as foamed vinyl chloride or synthetic rubber. A portion of the rim member  12  having the substantially E-shaped section can be made of an elastic material with high flexibility such as synthetic rubber. 
     As is conventionally known, the backing member for the main cap portion can be constituted by an impact absorbing liner for the main cap portion, attached to the inner surface of the outer shell  11  for the main cap portion with an adhesive or the like, and a blockish inside pad for the main cap portion and a backing cover for the main cap portion which are sequentially attached to cover substantially the inner surface of the impact absorbing liner. The impact absorbing liner for the main cap portion can be made of a material with appropriate rigidity and plasticity such as foamed polystyrene or another synthetic resin. The blockish inside pad for the main cap portion can be made of one or a plurality of elastic materials with high flexibility such as urethane foam or another synthetic resin, and a porous unwoven fabric covering the inner and outer surfaces of the elastic material(s) to form a bag. The backing cover for the main cap portion can be made of a porous unwoven fabric formed by laminating layers, consisting of an elastic material with high flexibility such as urethane foam or another synthetic resin, on the surface opposing the impact absorbing liner for the main cap portion. 
     As is conventionally known, the subsidiary cap portion  6  can be made up of an outer shell  14 , a rim member  16  having a substantially E-shaped section, and a backing member (not shown) for the subsidiary cap portion. The outer shell  14  forms the outer wall of the subsidiary cap portion  6 . The rim member  16  is fixed to part (i.e., the end portion of the window  15 ) of the end portion of the outer shell  14  with an adhesive or the like. The backing member for the subsidiary cap portion is brought into contact with the outer shell  14  to be fixed to it in contact with the inner surface of the outer shell  14  with an adhesive or the like. As is conventionally known, the outer shell  14  and the rim member  16  having the substantially E-shaped section can be made of the same materials as those described above concerning the outer shell  11  for the main cap portion and the rim member  12  having substantially the E-shaped section. A pair of right and left cover members  17  for externally covering the pair of right and left attaching screws  7  are attached to the outer shell  14  to be reciprocally pivotal about their front edge portions as the fulcrums. When the cover members  17  are outwardly pivoted forward through about 90°, the heads of the attaching screws  7  are exposed. Inversely, when the cover members  17  are pivoted backward, the heads of the attaching screws  7  are covered by the cover members  17 , as shown in FIGS. 1 to  3 . 
     As is conventionally known, the backing member for the subsidiary cap portion can be constituted by an impact absorbing liner for the subsidiary cap portion, and a backing cover for the subsidiary cap portion, attached to the inner surface of the impact absorbing liner to substantially cover it. The impact absorbing liner for the subsidiary cap portion is attached to the inner surface of the outer shell  14  for the subsidiary cap portion with an adhesive or the like, and can be made of a material with appropriate rigidity and plasticity such as foamed polyurethane rubber or another synthetic resin. The backing cover for the subsidiary cap portion can be made of synthetic leather or another cloth made of a synthetic resin such as vinyl chloride resin, or another fabric. 
     A pair of right and left subsidiary cap portion locking mechanisms  21  are incorporated in the head protecting body  2 . Each of the pair of subsidiary cap portion locking mechanisms  21  has a function of locking the subsidiary cap portion  6  at the lower position with the head protecting body  2 , as is clearly shown in FIG.  4 . The pair of subsidiary cap portion locking mechanisms  21  are unlocked by a common release button  22  serving as an unlocking means or member. 
     As shown in FIGS. 7 to  9 , the release button  22  is held by a button holding mechanism  20  serving as an unlocking member holding mechanism at substantially the central portion of the subsidiary cap portion  6  (i.e., a portion opposing the distal end of the wearer&#39;s chin) to be linearly, reciprocally slidable. The button holding mechanism  20  is constituted by the outer shell  14  for the subsidiary cap portion, and a button holding member  23 . The button holding member  23  is made of an appropriate material such as a synthetic resin, e.g., polyacetal resin or ABS resin. The button holding member  23  has a member main body  25 . The member main body  25  has an elongated hole  24  extending at substantially the central portion of its upper surface in the back-and-forth direction, and forms a substantially box-like lid. A pair of left and right substantially V-shaped attached pieces  26   a  and  26   b  are formed on the left and right sides of the member main body  25  by, e.g., monolithic molding. The attached pieces  26   a  and  26   b  respectively have screw engaging holes  27 . A guide  30  is formed near the front end of the upper surface of the member main body  25  by, e.g., monolithic molding. The guide  30  has a pair of left and right arcuated pieces  29   a  and  29   b  extending outwardly to the left and right, respectively. A pair of left and right subsidiary guide plates  31   a  and  31   b  are formed on the front end face of the member main body  25  by, e.g., monolithic molding. A pair of left and right attaching bosses  33   a  and  33   b  for attaching the button holding member  23  are formed at substantially the central portion of the outer shell  14  for the subsidiary cap portion (i.e., a portion opposing the distal end of the wearer&#39;s chin) by, e.g., monolithic molding. A finger-inserting aperture  34  is formed between the pair of attaching bosses  33   a  and  33   b.    
     As shown in FIGS. 7 and 8, the release button  22  is formed of an appropriate material such as a synthetic resin, e.g., nylon 6 or ABS resin, to have a substantially blockish shape. A finger-inserting notched portion  28  is formed in one half of the lower surface of the release button  22 . The notched portion  28  forms, in the release button  22 , a press surface  28   a  (i.e., a surface substantially perpendicularly intersecting the aperture  34 ) used for pressing the release button  22  with a finger. A columnar portion  35  having a screw hole  36  is formed on substantially the central portion of the upper surface of the release button  22  by, e.g., monolithic molding. A pair of left and right substantially L-shaped arms  37   a  and  37   b , and a protrusion  38 , all of which extend from the columnar portion  35 , are formed on the upper surface of the release button  22  by, e.g., monolithic molding. 
     As shown in FIGS. 7 and 8, a wire attaching member  39  serving as a wire body attaching member attached and fixed to the release button  22  is formed of an appropriate material such as a synthetic resin, e.g., nylon 6 or ABS resin, to have a substantially platelike shape. An elongated hole  40  extending in the back-and-forth direction is formed at substantially the central portion of the attaching member  39 . A substantially semicircular wire engaging portion  71  is formed on a surface of the attaching member  39  opposite to the outer shell  14  by, e.g., monolithic molding, to be near the rear end of the elongated hole  40 . A pair of left and right projecting ridges  72   a  and  72   b  are formed on the left and right sides of the wire engaging portion  71  by, e.g., monolithic molding. 
     The release button  22  is accommodated in the button holding mechanism  20 , constituted by the outer shell  14  for the subsidiary cap portion and the button holding member  23 , to be linearly reciprocally slidable. To accommodate the release button  22 , first, the release button  22  is fitted in the button holding member  23  to be linearly reciprocally slidable. When fitting the release button  22 , the columnar portion  35 , the pair of left and right arms  37   a  and  37   b , and the protrusion  38  of the release button  22  are inserted in the elongated hole  24  of the button holding member  23 . In this case, the pair of arms  37   a  and  37   b  are held to be linearly reciprocally slidable along the left and right rims of the elongated hole  24 . The right and left side surfaces and upper surface of the release button  22  are also held to be linearly reciprocally slidable along the left and right inner surfaces and lower surface of the member main body  25  of the button holding member  23 . 
     Subsequently, the button holding member  23  fitted with the release button  22  is attached and fixed to the outer shell  14  for the subsidiary cap portion. A pair of left and right attaching screws  73   a  and  73   b  inserted in the screw engaging holes  27  of the attached pieces  26   a  and  26   b  are screwed and fixed in the pair of left and right attaching bosses  33   a  and  33   b  of the outer shell  14  for the subsidiary cap portion, attaching and fixing the member  23 . Accordingly, the release button  22  is reciprocally slidable with respect to the button holding member  23  in directions indicated by arrows A and B in FIGS. 4 and 7. 
     The wire attaching member  39  is attached and fixed to the release button  22 . An attaching screw  75  is inserted in a washer  74  and the elongated hole  40  of the wire attaching member  39 , and the attaching screw  75  is then screwed and fixed in the screw hole  36  of the columnar portion  35  of the release button  22 , thereby attaching and fixing the member  39 . In this case, the washer  74  is placed on the wire engaging portion  71  and the pair of left and right projecting ridges  72   a  and  72   b  of the wire attaching member  39 . The wire attaching member  39  is placed on the pair of left and right arms  37   a  and  37   b  and the protrusion  38  of the release button  22 . 
     When the attaching screw  75  is slightly screwed into the screw hole  36 , an intermediate portion (in this case, substantially the central portion)  32   c  of a tractive wire  32 , serving as a tractive flexible wire and made of a metal or the like, is hooked on the substantially arcuated portion of the wire engaging portion  71  of the wire attaching member  39  to form substantially a U-letter shape, and thereafter the attaching screw  75  is screwed into the screw hole  36  to fix the wire attaching member  39 . In this case, before screwing and fixing, the wire attaching member  39  is linearly moved back and forth by utilizing the elongated hole  40 , so that the attaching position in the back-and-forth direction of the wire attaching member  39  with respect to the release button  22  can be adjusted. This adjusts the tautness of the tractive wire  32  to remove the unnecessary slack of the tractive wire  32 . The left and right portions of the tractive wire  32  that are directly continuous to the substantially U-shaped intermediate portion  32   c  are wound on the pair of left and right arcuated pieces  29   a  and  29   b . The tractive wire  32  is used commonly by the pair of right and left subsidiary cap portion locking mechanisms  21 . More specifically, the tractive wire  32  has a pair of left and right wire portions  32   a  and  32   b  continuous to the two ends of the U-shaped intermediate portion  32   c . The wire portion  32   a  (to be referred to as the “tractive wire  32   a ” hereinafter) on the right side (i.e., on right side of the front surface of the helmet  1 ; this applies to the following description) is used by the right subsidiary cap portion locking mechanism  21 . The wire portion  32   b  (to be referred to as the “tractive wire  32   b ” hereinafter) on the left side (i.e., on left side of the front surface of the helmet  1 ; this applies to the following description) is used by the left subsidiary cap portion locking mechanism  21 . Since the right and left subsidiary cap portion locking mechanisms  21  are symmetric, a description will be made concerning the right subsidiary cap portion locking mechanism  21  hereinafter with reference to FIGS. 4 to  6 , and a description on the left subsidiary cap portion locking mechanism  21  will be omitted. 
     Referring to FIGS. 4 to  6 , an attaching base  41  made of an appropriate material such as a metal like stainless steel, or a synthetic resin like ABS resin, is attached and fixed to the inner surface of the right ear  6   b  of the subsidiary cap portion  6  with an attaching screw  42 . A lock lever  43  serving as a movable locking means or member is axially supported on the attaching base  41  with an attaching screw  44  to be reciprocally pivotal. A stopped portion  45  made of a flat-plate-like upright portion is integrally formed on one end portion of the lock lever  43 . A wire attached portion  46  formed of an L-shaped upright portion is integrally formed on the other end portion of the lock lever  43 . Since the stopped portion  45  is inserted in an incision  47  formed in the attaching base  41 , the forward and backward pivot positions of the lock lever  43  are regulated by the attaching base  41 . The wire attached portion  46  fixes the distal end portion of an attaching rod  48 , the proximal end portion of which extends from the lock lever  43 . The free end portion of the tractive wire  32   a  is fixed to the attaching rod  48 . 
     A spring retainer  49  which can have a substantially cup-like shape is formed on the attaching base  41  by monolithic molding or with an adhesive. The tractive wire  32   a  is inserted in a wire inserting hole  50  of the spring retainer  49 . The tractive wire  32   a  extends through a flexible tube  52  made of an appropriate elastic material such as synthetic rubber. One end portion of the tube  52  is held in position by the arcuated piece  29   a  and subsidiary guide plate  31   a  of the button holding member  23 , and abuts against a front end face  63  of the member main body  25 . The other end portion of the tube  52  abuts against the spring retainer  49 . One end portion of a tube  52  identical to the above tube  52  and used by the left subsidiary cap portion locking mechanism  21  is also held in position by the arcuated piece  29   b  and subsidiary guide plate  31   b  of the button holding member  23 , and abuts against the front end face  63  of the member main body  25 . 
     A compression coil spring  51  through which the tractive wire  32   a  extends is interposed between the spring retainer  49  and the wire attached portion  46  of the lock lever  43 . For this reason, the lock lever  43  is biased by the coil spring  51  to pivot counterclockwise in FIG. 4 about the attaching screw  44  as the center. Since the lock lever  43  is biased to pivot counterclockwise in FIG. 4, the release button  22  is tractively biased by the tractive wire  32   a  to move backward in the direction indicated by the arrow B in FIGS. 4 and 7. 
     The release button  22  can move forward in the direction indicated by the arrow A in FIGS. 4 and 7 against the tractive biasing force of the tractive wire  32   a . The forward moving direction A of the release button  22  forms an acute angle θ with respect to a downward moving direction (i.e., a backward pivot direction about the attaching screws  7  as the fulcrum) C of the subsidiary cap portion  6 , as shown in FIG.  4 . In the embodiment shown in FIG. 4, the acute angle θ is about 25°. However, from the viewpoint of practicability, this angle is preferably 0° to 60°, and more preferably 0° to 45°. The forward moving direction A of the release button  22  is inward (i.e., backward in FIG. 4) of the downward moving direction C of the subsidiary cap portion  6 . However, this direction A need not be inward but can be outward. In order to operate the release button  22  forward and move the subsidiary cap portion  6  upward very smoothly, the forward moving direction A of the release button  22  is preferably inward of the downward moving direction C of the subsidiary cap portion  6 . In this case, the acute angle θ is particularly preferably 5° to 45°. 
     A pair of right and left lock pins  54  serving as a stationary locking means or member project near the lower end of the outer surface of the outer shell  11  of the main cap portion  5 . The lock levers  43  of the right and left subsidiary cap portion locking mechanisms  21  selectively engage with the lock pins  54  depending on their pivot positions. Each lock lever  43  is formed with an abutting portion  43   a  against which the corresponding lock pin  54  abuts. A locking recess  62  to engage with the lock pin  54  is formed adjacent to the abutting portion  43   a.    
     The respective portions (i.e., the attaching bases  41 , coil springs  51 , lock levers  43 , attaching rods  48 , attaching screws  42  and  44 , and the like) of the locking mechanisms  21 , the release button  22 , the button holding mechanism  20  (i.e., the button holding member  23 , attaching bosses  33   a  and  33   b , and the like), the wire attaching member  39 , the washer  74 , the attaching screws  73   a ,  73   b , and  75 , the tubes  52 , the tractive wires  32   a  and  32   b , and the like are arranged along the inner surface of the outer shell  14  for the subsidiary cap portion. Hence, recesses and ridge grooves for accommodating these portions are formed in the surface of the impact absorbing liner for the subsidiary cap portion that opposes the outer shell  14 . 
     As shown in FIGS. 1 to  3 , a ventilation aperture forming member  55  for the forehead is attached to the outer surface of the forehead portion of the main cap portion  5 . A stopper  56  for regulating the backward position of the shield plate  4  is provided to the right portion of the outer surface of the subsidiary cap portion  6 . Various types of ventilation apertures  57 ,  58 , and  59  are formed in the chin cover  6   a  of the subsidiary cap portion  6 . As shown in FIGS. 4 to  6 , an air guide plate  60  is attached to the inner surface of the chin cover  6   a  with attaching screws  61  so as to oppose the ventilation apertures  57 . Therefore, air flowing into the head protecting body  2  through the ventilation apertures  57  is guided by the front surface of the air guide plate  60  to move upward in the head protecting body  2  along the inner surface of the shield plate  4 . 
     How to use the full-face-type helmet serving also as the jet-type helmet having the above arrangement will be described. 
     Assume that the wearer wishes to use the helmet  1  as a full-face-type helmet. If the subsidiary cap portion  6  is at the upper position, as shown in FIG. 3, the wearer pivots it downward about the attaching screws  7  as the center, thereby bringing it to the lower position shown in FIGS. 1 and 2. 
     In this case, the abutting portions  43   a  of the lock levers  43  provided to the subsidiary cap portion  6  as shown in FIG. 6 abut against the lock pins  54 . The lock levers  43  are accordingly pressed by the lock pins  54 , and pivot slightly forward clockwise in FIG. 6 about the attaching screws  44  as the fulcrum against the biasing force of the coil springs  51 . The lock pins  54  thus ride over the abutting portions  43   a  of the lock levers  43 , as shown in FIG. 4, to engage with the corresponding locking recesses  62 . The subsidiary cap portion  6  is securely locked by the main cap portion  5  with the pair of right and left subsidiary cap portion locking mechanisms  21 , so that the head protecting body  2  serves as the full-face-type. 
     Assume that the wearer wishes to use the helmet  1  shown in FIGS. 1 and 2, currently serving as the full-face-type helmet, as a jet-type helmet shown in FIG.  3 . In the state shown in FIG. 4, the wearer inserts his finger (e.g., index finger and/or middle finger) in the notched portion  28  of the release button  22  through the aperture  34  located at substantially the central portion of the outer surface of the chin cover  6   a  of the subsidiary cap portion  6 . The wearer presses the press surface  28   a  of the release button  22  with this finger downward in the forward direction, indicated by the arrow A in FIG. 4, against the biasing force of the coil springs  51 . In this case, since the press surface  28   a  substantially perpendicularly intersects the forward direction A of the release button  22 , the direction of the force applied by the finger onto the release button  22  substantially coincides with this forward direction A. 
     Since the release button  22  moves forward in the direction indicated by the arrow A against the biasing force of the coil springs  51 , the tractive wire  32   a  is pulled by the release button  22  to slide along the arcuated piece  29   a  of the button holding member  23 . Therefore, the lock levers  43  in the state shown in FIG. 4 pivot forward clockwise about the attaching screws  44  as the fulcrum to be set in the state shown in FIG.  5 . This unlocks the subsidiary cap portion  6  locked on the main cap portion  5  by the subsidiary cap portion locking mechanisms  21 . Accordingly, if the wearer simultaneously places his finger (e.g., the thumb) on substantially the central portion of the lower end of the subsidiary cap portion  6  (e.g., grabs the subsidiary cap portion  6  from the upper and lower sides with his index finger and/or middle finger inserted in the notched portion  28  and his thumb placed on substantially the central portion of the lower end of the subsidiary cap portion  6 ), and raises the subsidiary cap portion  6 , the subsidiary cap portion  6  pivots upward about the attaching screws  7  as the fulcrum. The subsidiary cap portion  6  is set in the state shown in FIG.  3  through the state shown in FIG.  6 . Thus, the head protecting body  2  serves as the jet-type. 
     In the first embodiment, the tractive wires  32   a  and  32   b  are inserted in the tubes  52 . The tractive wires  32   a  and  32   b  can be easily set not to come into substantial contact with any foreign matter other than the tubes  52 . As a result, the tractive wires  32   a  and  32   b  can always move comparatively smoothly. These tubes  52  can be omitted if necessary. If the tubes  52  are omitted, the tractive wires  32   a  and  32   b  are preferably selected to have such a length that they extend substantially linearly between the arcuated pieces  29   a  and  29   b  of the guide plate  30  of the button holding member  23  and the spring retainers  49  of the attaching bases  41 . 
     Second Embodiment 
     The second embodiment in which the present invention is applied to a full-face-type helmet serving also as a jet-type helmet will be described with reference to FIGS. 10 to  22 . 
     The helmet of the second embodiment shown in FIGS. 10 to  22  has substantially the same arrangement, function, and effect as those of the helmet according to the first embodiment described above shown in FIGS. 1 to  9 , except for the differences and respects concerning them described in the following items (1) to (7). Accordingly, in the following description, only the differences and respects concerning them described in these items (1) to (7) will be described. Portions that are common between the helmet according to the second embodiment shown in FIGS. 10 and 22 and the helmet according to the first embodiment described above shown in FIGS. 1 to  9  are denoted by the same reference numerals, and a description other than the differences and respects concerning them will be omitted. 
     (1) A pair of right and left support plates  81  for supporting a subsidiary cap portion  6  onto a main cap portion  5  are provided to the main cap portion  5 . 
     (2) Cover members corresponding to the cover members  17  for covering attaching screws  7  used to attach the subsidiary cap portion  6  to the main cap portion  5  are omitted. 
     (3) A finger putting plate  83  serving as a finger putting portion is provided to a button holding member  23  of a button holding mechanism  20 . 
     (4) A subsidiary attaching base  82  is provided to an attaching base  41  of each subsidiary cap portion locking mechanism  21 . 
     (5) A pair of left and right flexible tubes, corresponding to the tubes  52  through which a pair of left and right tractive wires  32   a  and  32   b  are inserted, are omitted. 
     (6) A wire attaching member  39  of the button holding mechanism  20  is arranged upside down. 
     (7) The arrangement of ventilation apertures  59  formed in a chin cover  6   a  of the subsidiary cap portion  6  is altered. 
     Items (1) and (2) 
     Each of the pair of right and left support plates  81  is an elongated platelike member extending in substantially the back-and-forth direction, as shown in FIGS. 11 and 12, and can be made of a material similar to that described above concerning the button holding member  23 . The support plates  81  are fixed to an outer shell  11  for a main cap portion with attaching screws  84  at their portions near the front end portions. The portions of the support plates  81  near the rear end portions are also fixed, together with ears  6   b  of the subsidiary cap portion  6 , to the outer shell  11  for the main cap portion with attaching screws (i.e., axial support means)  7 . The cover members  17  provided in the first embodiment for the attaching screws  7  are omitted in the second embodiment. 
     As shown in FIGS. 21 and 22, a projection  86  to fit in a coil portion  85   a  provided at the central portion of a spring  85  serving as a biasing means is formed on each support plate  81  by monolithic molding or the like. The spring  85  serves as a torsion coil spring, and further has first and second wire portions  85   b  and  85   c  extending from the coil portion  85   a  in substantially the opposite directions. The support plate  81  is formed with a pair of spring catching projections  87  and  88  by monolithic molding or the like to engage with the first coil portion  85   b . The first wire portion  85   b  is inserted between the pair of projections  87  and  88 . 
     As shown in FIGS. 21 and 22, a pair of right and left projections  89  serving as positioning means project from the inner surface of an outer shell  14  at each of the pair of right and left ears  6   b  of the subsidiary cap portion  6 . The second wire portion  85   c  of the spring  85  is bent almost arcuatedly. When the subsidiary cap portion  6  is at the lower position, as shown in FIGS. 11 and 21, the positioning projection  89  serving also as the spring hook means presses against the arcuated second wire portion  85   c.    
     The support plates  81  are formed with a pair of right and left recesses  90  serving as positioning means. When the subsidiary cap portion  6  is at the lower position, as shown in FIG. 11, the positioning projections  89  lightly engage or fit with the recesses  90 , as shown in FIG. 21, to prohibit the subsidiary cap portion  6  from moving with a comparatively small action force. When the projections  89  engage or fit with the recesses  90 , the upward biasing force for the subsidiary cap portion  6  generated by the springs  85  can be entirely or partially reduced by this engagement or fitting. The subsidiary cap portion  6  located at the lower position is not only locked at the lower position by the pair of right and left subsidiary cap portion locking mechanisms  21 , but is lightly held in position at the lower position by the recess-projection engagement of the positioning means  89  and  90 ,  50  that its forward movement is prohibited by a comparatively small action force. The springs  85  bias the subsidiary cap portion  6  upward (i.e., in the forward direction) through the positioning projections  89 , so that the subsidiary cap portion  6  is raised smoothly when the recess-projection engagement is canceled. Furthermore, since the springs  85  bias the subsidiary cap portion  6  clockwise in FIGS. 11 and 13 with respect to the main cap portion  5  about the attaching screws (i.e., axial support means)  7  as the fulcrum, they prevent lock pins  54  from removing accidentally from locking recesses  62  of lock levers  43  upon vibration or the like of the helmet  1 . 
     Each support plate  81  is formed with a substantially semicylindrical stopper projection  91  by monolithic molding or the like. When the subsidiary cap portion  6  is at the upper position, as shown in FIG. 12, the positioning projection  89  engages with the stopper projection  91 , as shown in FIG.  22 . The support plate  81  is also formed with a stopper projection  92 , having an inclined surface, adjacent to the stopper projection  91  by monolithic molding or the like. While the subsidiary cap portion  6  moves from the lower position to immediately before the upper position, the positioning projection  89  gradually rides over the inclined surface of the stopper projection  92 . Accordingly, while the subsidiary cap portion  6  moves from the lower position to immediately before the upper position, the positioning projection  89  rides over the inclined surface of the stopper projection  92  and thereafter passes it. As a result, as shown in FIG. 22, the positioning projection  89  (and also the subsidiary cap portion  6 ) is completely prohibited by the stopper projection  91  from moving further forward and by the stopper projection  92  from moving backward, with a comparatively small action force. 
     Item (3) 
     The finger putting plate  83  having a substantially vertical finger putting surface  83   a  is formed on the rear end face of a member main body  25  of the button holding member  23  of the button holding mechanism  20  by monolithic molding or the like. The finger putting surface  83   a  has projecting ridges  93   a ,  93   b , and  94  at its left and right side end portions and lower end portion, respectively. The projecting ridges  93   a ,  93   b , and  94  form a substantially U-letter shape as a whole. Accordingly, when raising the subsidiary cap portion  6 , if the wearer places his finger (e.g., thumb) on the finger putting surface  83   a  of the finger putting plate  83 , in place of placing his finger at substantially the central portion of the lower end of the subsidiary cap portion  6  as in the first embodiment, and thereafter raises the subsidiary cap portion  6  upward, this raising operation can be performed smoothly. 
     The outer shell  14  is formed with an expansion  95  at substantially the central portion of the lower end of the chin cover  6   a  of the subsidiary cap portion  6  to slightly expand forward to conform to the shape of the finger putting plate  83 . 
     Item (4) 
     In the second embodiment, the attaching base  41  corresponding to the attaching base  41  of the first embodiment is constituted by the main attaching base  41  and the subsidiary attaching base  82 , as shown in FIGS. 13 and 17. In this case, the subsidiary attaching base  82  may be made of the same material as that described above concerning the attaching base  41 . Note that the main attaching base  41  is preferably made of a metal and the subsidiary attaching base  82  is preferably made of a synthetic resin. 
     As shown in FIG. 17, the main attaching base  41  can have a flat platelike shape. The main attaching base  41  is formed with a pair of boss inserting holes  101   a  and bib, a rivet inserting hole  102 , a boss inserting hole  103 , and a screw inserting hole  104 . In the first embodiment, the spring retainer  49  is formed on the attaching base  41 . In the second embodiment, a spring retainer  49  is formed on the subsidiary attaching base  82  by monolithic molding or the like. The subsidiary attaching base  82  has a step  82   a  at substantially its central portion, and a front plate  82   b  and a rear plate  82   c  on the two sides of the step  82   a . The rear plate  82   c  is formed with a pair of screw inserting bosses  105   a  and  105   b  and the spring retainer  49  by monolithic molding or the like. 
     Spherical bodies  106  made of a metal or the like are fixed to the free ends of the pair of right and left tractive wires  32   a  and  32   b , as shown in FIGS. 13 and 17. A substantially semicircular engaging notch  107  is formed on the free end of a wire attached portion  46  of each lock lever  43 . A substantially circular engaging aperture  108  is formed in a lever main body  109  of the lock lever  43 , on a side of the engaging notch  107  opposite to the outer shell  14 .Portions near the free ends of the tractive wires  32   a  and  32   b  are inserted between the lever main bodies  109  of the lock levers  43  and the wire attached portions  46  from above, and the spherical bodies  106  are fitted in the engaging notches  107  and engaging apertures  108 , thereby fixing the free ends of the tractive wires  32   a  and  32   b  to the lock levers  43 . 
     On the inner surface of the outer shell  14 , a pair of upper and lower projecting ridges  111   a  and  111   b  extending substantially horizontally are formed on each of the left and right sides of the chin cover  6   a  of the subsidiary cap portion  6 , as shown in FIGS. 13 and 17, by monolithic molding or the like. On the inner surface of the outer shell  14 , a pair of upper and lower screwing bosses  112   a  and  112   b , a positioning boss  113 , and a screwing boss  114  are formed on each of the left and right sides of the chin cover  6   a  of the subsidiary cap portion  6  by monolithic molding or the like, to be adjacent to the projecting ridges  111   a  and  111   b . The substantially intermediate portion of each of the tractive wires  32   a  and  32   b  is interposed between the corresponding pair of projecting ridges  111   a  and  111   b  so that it is positioned to a certain degree. A rivet  116  inserted in a rivet engaging hole  115 , formed in the lever main body  109  of the lock lever  43 , and the rivet engaging hole  102  in the main attaching base  41  pivotally fixes the lock lever  43  to the attaching base  41 . The positioning boss  113  is fitted in the boss inserting hole  103  of the attaching base  41 , and the front surface of the attaching base  41  is abutted against the distal end face of the screwing boss  114 . After that, a screw  117  is inserted in the screw inserting hole  104  of the attaching base  41  and screwed into the screwing boss  114 , thereby fixing the attaching base  41  to the inner surface of the outer shell  14 . 
     As shown in FIGS. 13 and 17, the pair of screwing bosses  112   a  and  112   b  are inserted in the boss inserting holes  101   a  and  101   b  of the attaching base  41 . The distal end faces of the bosses  112   a  and  112   b  abut against a surface, on the outer shell  14  side, of the front plate  82   b  of the subsidiary attaching base  82 . A pair of upper and lower screws  118   a  and  118   b  are inserted in the screw inserting bosses  105   a  and  105   b , and screwed into the screwing bosses  112   a  and  112   b , thereby fixing the subsidiary attaching base  82  and main attaching base  41  to the inner surface of the outer shell  14 . 
     According to the above arrangement, as shown in FIG. 16, a gap  121  is defined by the main attaching base  41 , the lock lever  43 , and the rear plate  82   c  of the subsidiary attaching base  82 . Accordingly, the subsidiary attaching base  82  serves as a gap defining member as well. When the subsidiary cap portion  6  is at the lower position shown in FIGS. 13 and 14 and at the intermediate position shown in FIG. 15 which is slightly above the lower position, portions of the outer shell  11  of the main cap portion  5  near its lower end are inserted in the corresponding gaps  121 . Therefore, portions of the outer shell  11  near its lower end (also the lock pins  54 ) and the lock levers  43  of the subsidiary cap portion  6  are positioned relative to each other to a certain degree in the direction of thickness of the outer shell  11 . This can prevent the lock pins  54  from accidentally, relatively removing from the locking recesses  62  of the lock levers  43 , or from abutting portions  43   a  of the lock levers  43 , to a certain degree. A cover member (not shown) for covering the outer surface and, if necessary, the inner surface as well, of a portion of the outer shell  11  near its lower end may be provided, and the lock pins  54  may be fixed to the cover member. This cover member can be made of the same material as that described above concerning the button holding member  23 . 
     As shown in FIG. 16, on the inner surface of the outer shell  14 , the pair of right and left subsidiary attaching bases  82  are formed on the right and left sides of the chin cover  6   a  of the subsidiary cap portion  6 . Accordingly, the gap  121  is formed on each of the right and left sides to form a pair. A pair of right and left portions of the outer shell  11 , near the lower end, of the main cap portion  5  are inserted in the pair of right and left gaps  121 , respectively. This insertion amount is the maximum when the subsidiary cap portion  6  is at the lower position shown in FIGS. 13 and 14, and decreases gradually as the subsidiary cap portion  6  moves forward from the lower position shown in FIGS. 13 and 14 to the intermediate position shown in FIG. 15 which is slightly above the lower position. When the subsidiary cap portion  6  further moves upward from the intermediate position shown in FIG. 15, the pair of right and left portions of the outer shell  11  near its lower end completely disengage from the pair of right and left gaps  121 . When the subsidiary cap portion  6  moves downward, an operation precisely opposite to that described above is performed. 
     Item (5) 
     In the first embodiment, the pair of left and right tubes  52  are provided to extend the pair of left and right tractive wires  32   a  and  32   b  therethrough. In the second embodiment, such tubes  52  are omitted. Therefore, the tractive wires  32   a  and  32   b  extend substantially linearly between arcuated pieces  29   a  and  29   b  of a guide  30  of the button holding member  23  and the spring retainers  49  of the subsidiary attaching bases  41 . 
     Item (6) 
     In the second embodiment, the wire attaching member  39  of the button holding mechanism  20  is arranged upside down from the state of the first embodiment, as shown in FIGS. 18 and 19. Accordingly, a wire engaging portion  71  and a pair of left and right projecting ridges  72   a  and  72   b  are formed on the surface of the wire attaching member  39  on the outer shell  14  side. 
     In the post-assembly state shown in FIGS. 18 and 20, a pair of left and right arms  37   a  and  37   b  of a release button (i.e., unlocking member)  22  are fitted between the pair of left and right projecting ridges  72   a  and  72   b  of the wire attaching member  39 . In other words, a projection formed by the pair of left and right arms  37   a  and  37   b  (the intermediate portion of this projection, i.e., the portion between the pair of arms  37   a  and  37   b , forms a notch) is fitted in a recess formed between the pair of left and right projecting ridges  72   a  and  72   b  through recess-projection fitting, to be linearly, reciprocally slidable. 
     The wire engaging portion  71  of the wire attaching member  39  is inserted between the pair of left and right arms  37   a  and  37   b . A U-shaped intermediate portion  32   c  of the tractive wire  32  is hooked on the wire engaging portion  71 , and abuts against the right and left sides of a columnar portion  35  of the release button  22 . Accordingly, the intermediate portion  32   c  is securely sandwiched from the two sides by the proximal end portions of the pair of left and right arms  37   a  and  37   b  of the release button  22  and a surface of the wire attaching member  39  on the outer shell  14  side. 
     In the first embodiment, the pair of arms  37   a  and  37   b  of the release button  22  linearly, reciprocally slide along the rim of the elongated hole  24  of the button holding member  23 . In contrast to this, in the second embodiment, the pair of projecting ridges  72   a  and  72   b  of the wire attaching member  39  linearly, reciprocally slide along the rim of an elongated hole  24  corresponding to their counterpart of the first embodiment. 
     Item (7) 
     In the first embodiment, the chin cover  6   a  of the subsidiary cap portion  6  is formed with the pair of right and left comparatively large ventilation apertures  59 . In contrast to this, in the second embodiment, the right and left ventilation aperture pairs  59 , each consisting of comparatively small two, front and rear ventilation apertures, are formed. 
     Having described two specific preferred embodiments of this invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to that precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. 
     For example, in the first and second embodiments, the direction perpendicularly intersecting the press surface  28   a  of the release button  22  substantially coincides with the forward moving direction A of the release button  22 . However, if these two directions more or less do not coincide with each other, no problem arises. In this case as well, an acute angle θ′ formed by the direction perpendicularly intersecting the press surface  28   a  of the release button  22  with respect to the downward moving direction C of the subsidiary cap portion may have the same angular range as that described concerning the acute angle θ.