Patent Publication Number: US-2011072563-A1

Title: Pin lock device and helmet including same

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to a pin lock device allowing detachable attachment of a film to a surface of a shield for use in a helmet and a helmet including same; and, more particularly, to a pin lock device enabling attachment of a shield protective film and an anti-moisture film to a shield while allowing an increase of the lifetime of the shield and comfortable use of a helmet, and also relates to a helmet including such a pin lock device. 
     BACKGROUND OF THE INVENTION 
     Wearing a helmet is required to drive a two-wheeled vehicle such as a motorcycle. An opening is provided in the front portion of a helmet main body to secure visibility ahead of a driver, and an openable/closable shield is positioned at the front opening of the helmet main body. 
     Since the helmet has a sealed structure lacking sufficient ventilation between the inside and the outside thereof, the driver may feel stuffy, and the inside of the helmet may get damp as the driver breathes, obstructing the driver&#39;s field of vision. To solve the problem of generation of moisture inside the shield, there has been provided a helmet having an anti-moisture film attached to an inner side of the shield. 
     Typically, the shield exposed to the outside of the helmet is generally made of plastic or the like to secure visibility and to allow easy opening/closing operation. In such a case, however, if a damage or a scratch is inflicted on the surface of the shield due to impurities from the outside, there has been known a technique to replace the shield or to attach a shield protective film to the outside of the shield to obtain visibility. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, the present disclosure provides an improved pin lock device secured to a shield and capable of allowing easy attachment of an anti-moisture film or a shield protective film to the inside or the outside of the shield while allowing easy replacement of the films. Further, the present disclosure also provides an improved helmet having such a pin lock device. 
     In accordance with one aspect of the present disclosure, there is provided a pin lock device of a shield secured to a helmet main body in an openable/closable manner, the pin lock device including: lock insertion holes, formed through both lateral surfaces of the shield; lock pins, each being inserted into each of the lock insertion holes from the inside of each lock insertion hole toward the outside thereof; and lock bases, each being engaged with each of the lock pins from the outside of each lock insertion hole. The each lock pin includes: a pin protrusion to be fitted into each of the lock bases through each of the lock insertion holes in an outward direction; a pin supporting plate to be brought into firm contact with each of the lock insertion holes at an inner side of the shield to stop an outward movement of each lock pin; and a pin handle inwardly extending from the pin supporting plate and serving as a head of each lock pin. 
     Further, each of the lock pins may further includes: each of pin grooves formed as a curved cut portion between the pin supporting plate and the pin handle and having a cross section smaller than cross sections of the pin supporting plate and the pin handle. An anti-moisture film may be detachably fitted between the pin grooves along both inner lateral surfaces of the shield. 
     Further, each lock base may includes: a base protrusion to be accommodated in each of the lock insertion holes while allowing each lock pin to be inserted into a cavity formed within the base protrusion; a base supporting plate to be brought into firm contact with each of the lock insertion holes at an outer side of the shield to stop an inward movement of each lock base; and a base handle outwardly extending from the base supporting plate and serving as a head of each lock base. 
     Moreover, each of the lock bases may further includes: each of base grooves formed as a curved cut portion between the base supporting plate and the base handle and having a cross section smaller than cross sections of the base supporting plate and the base handle. A shield protective film may be detachably fitted between the base grooves along both outer lateral surfaces of the shield. 
     In addition, each lock base may further includes: a protrusion accommodating part formed within each of the lock bases to be positioned around the cavity to prevent separation of each lock pin from each lock base. The cavity may be formed in a shape corresponding to a shape of the pin protrusion. If the pin protrusion inserted in the cavity rotates within each of the lock bases in a secured state, the pin protrusion may come out of the cavity and may be positioned on the protrusion accommodation part, and, thus, each lock pin is fixed in place. 
     Further, both the cavity and the pin protrusion may have straight line shapes. 
     Furthermore, the base protrusion may be formed to be located at an eccentric position of each of the lock bases, and a distance between the lock bases at both lateral surfaces of the shield is varied when each of the lock bases rotates while engaged with each lock pin. 
     In accordance with another aspect of the present disclosure, there is provided a helmet including a shield secured to a helmet main body in an openable/closable manner and pin lock devices fastened to both lateral surfaces of the shield, the helmet including: lock insertion holes, formed through both lateral surfaces of the shield; lock pins, each being inserted into each of the lock insertion holes from the inside of each lock insertion hole toward the outside thereof; and lock bases, each being engaged with each of the lock pins from the outside of each lock insertion hole. Each lock pin includes: a pin protrusion to be fitted into each of the lock bases through each of the lock insertion holes in an outward direction; a pin supporting plate to be brought into firm contact with each of the lock insertion holes at an inner side of the shield to stop an outward movement of each lock pin; and a pin handle inwardly extending from the pin supporting plate and serving as a head of each lock pin. Each lock base includes: a base protrusion to be accommodated in each of the lock insertion holes while allowing each lock pin to be inserted into a cavity formed within the base protrusion; a base supporting plate to be brought into firm contact with each of the lock insertion holes at an outer side of the shield to stop an inward movement of each lock base; and a base handle outwardly extending from the base supporting plate and serving as a head of each lock base. 
     Further, each of the lock pins may further includes each of pin grooves formed as a curved cut portion between the pin supporting plate and the pin handle and having a cross section smaller than cross sections of the pin supporting plate and the pin handle. An anti-moisture film may be detachably fitted between the pin grooves along both inner lateral surfaces of the shield. Each of the lock bases may further includes each of base grooves formed as a curved cut portion between the base supporting plate and the base handle and having a cross section smaller than cross sections of the base supporting plate and the base handle. A shield protective film may be detachably fitted between the base grooves along both outer lateral surfaces of the shield. 
     Furthermore, each lock base may further includes a protrusion accommodating part formed within each of the lock bases to be positioned around the cavity to prevent separation of each lock pin from each lock base. The cavity may be formed in a shape corresponding to a shape of the pin protrusion. If the pin protrusion inserted in the cavity rotates within each of the lock bases in a secured state, the pin protrusion may come out of the cavity and may be positioned on the protrusion accommodation part, and, thus, each lock pin is fixed in place. 
     Moreover, both the cavity and the pin protrusion may have straight line shapes. 
     Furthermore, the base protrusion may be formed to be located at an eccentric position of each of the lock bases. A distance between the lock bases at both lateral surfaces of the shield may be varied when each of the lock bases rotates while engaged with each lock pin. 
     In accordance with the present disclosure as described above, it is possible to provide an improved pin lock device secured to a shield and capable of allowing easy attachment of an anti-moisture film or a shield protective film to the inside or the outside of the shield while allowing easy replacement thereof. Further, an improved helmet having the pin lock device can also be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments will be described in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be intended to limit its scope, the disclosure will be described with specificity and detail through use of the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a helmet in accordance with an embodiment of the present disclosure; 
         FIG. 2  is an exploded perspective view of a shield, a pin lock device, an anti-moisture film and a shield protective film in accordance with the embodiment of the present disclosure; 
         FIGS. 3A and 3B  illustrate a state in which a lock pin is engaged with a lock base with the shield positioned therebetween:  FIG. 3A  shows a state in which the lock pin is fitted into a center position of the lock base while  FIG. 3B  shows a state in which the lock pin is fitted into an eccentric position of the lock base; 
         FIG. 4  illustrates a state in which the lock base is engaged with the lock pin with the shield positioned therebetween; 
         FIGS. 5A and 5B  illustrate a state in which the lock base engaged with the lock base through a lock insertion hole rotates about a base protrusion provided at an eccentric position of the lock base:  FIG. 5A  shows a state in which a center of the base protrusion is positioned outside a center of the lock base while  FIG. 5B  shows a state in which the center of the base protrusion is positioned inside the center of the lock base; 
         FIGS. 6A and 6B  are cross sectional views illustrating a state before the lock pin is engaged with the lock base:  FIG. 6A  shows a state in which the lock pin is fitted into a center position of the lock base while  FIG. 6B  shows a state in which the lock pin is fitted into an eccentric position of the lock base; 
         FIG. 7  provides a cross sectional view showing a state immediately after the lock pin is inserted into the lock base and also provides a partial enlarged view of an inserted part; and 
         FIG. 8  provides a cross sectional view showing a state in which the lock pin inserted into the lock base is firmly engaged with the lock base through rotation and also provides a partial enlarged view showing an engaged part. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the present invention may be readily implemented by those skilled in the art. However, it is to be noted that the present invention is not limited to the embodiments but can be realized in various other ways. In the drawings, parts irrelevant to the description are omitted for the simplicity of explanation, and like reference numerals denote like parts through the whole document. 
     Further, the term “comprises or includes” and/or “comprising or including” used in the document does not mean that existence or addition of one or more other components or elements is excluded in addition to the described components or elements unless otherwise specified. 
     Hereinafter, a pin lock device and a helmet having the pin lock device in accordance with an embodiment of the present disclosure will be explained with reference to  FIGS. 1 to 8 . 
       FIG. 1  is a perspective view of a helmet  10  in accordance with the embodiment of the present disclosure. 
     As illustrated in  FIG. 1 , the helmet  10  in accordance with the present embodiment includes a helmet main body  11 , an opening  12  and a shield  20  secured to the helmet main body  11  to be opened or closed. 
     The helmet main body  11  serves as a main body of the helmet  10 , and it has an inner space in which a user&#39;s head is accommodated. To firmly fit the users&#39; head, the helmet main body  10  is designed to have a sealed structure. The helmet main body  11  is provided with the opening  12  at its front surface to secure visibility ahead of it. 
     The shield  20  is a transparent window capable of selectively opening and closing the opening  12  lest the field of vision should be obstructed by wind, rain, snow or the like blown from ahead when a vehicle travels. Inner engagement members  21  capable of being engaged with the helmet main body  11  are formed at both lateral end surfaces of the shield  20 . The shield  20  is secured to the helmet main body  11  as shield engagement members  13  formed along both lateral surfaces of the helmet main body  11  are engaged with the inner engagement members  21 . 
     The shield  20  may include lock insertion holes  22  formed through both lateral surfaces thereof (see  FIG. 2 ). Pin lock devices  200  can be secured to the shield  20  as they are fitted into the lock insertion holes  22 . Further, at the inner side of the shield  20 , an anti-moisture film  220  can be insertion-fitted between the pin lock devices  200  secured to both lateral surfaces of the shield  20 . Furthermore, at the outer side of the shield  20 , a shield protective film  240  can be fitted between the pin lock devices  200  secured to both lateral surfaces of the shield  20 . The shield  20 , the pin lock devices  200  and the films  220  and  240  will be described in further detail with reference to  FIGS. 2 to 4 . 
       FIG. 2  is an exploded perspective view illustrating the shield  20 , the pin lock devices  200 , the anti-moisture film  220  and the shield protective film  240 .  FIG. 3  shows a state in which a lock pin  210  is engaged with a lock base  230  with the shield  20  positioned therebetween, and the anti-moisture film  220  can be detachably insertion-fitted between them. Here, as illustrated in  FIGS. 3A and 3B , the lock base  230  may have various shapes as long as it can be engaged with the lock pin  210  while accommodated on the shield  20 .  FIG. 4  illustrates a state in which the lock base  230  is engaged with the lock pin  210  with the shield  20  interposed therebetween, and the shield protective film  240  can be detachably fitted to the lock base  230 . 
     As shown in  FIG. 2 , the shield  20  is provided with the lock insertion holes  22  formed through its both lateral surfaces. The pin lock devices  200  are fitted in these lock insertion holes  22 . 
     Each lock insertion hole  22  has a diameter capable of accommodating therein a pin protrusion  211  of the pin lock device  200  inserted therethrough while allowing the pin protrusion  211  accommodated in a base protrusion  231  to be rotated in clockwise direction or counterclockwise direction. The lock insertion hole  22  is formed in each of both lateral surfaces of the shield  20 , and it may be provided with a bearing  22   a  (see  FIGS. 3A and 3B ). 
     The bearing  22   a  is a ring-shaped member formed at the inside of the pin insertion hole  22  to conform to the outline of the pin insertion hole  22 . When the pin lock device  200  is rotated after it is secured to the shield  20 , the bearing  22   a  may absorb friction, facilitating smooth rotation. 
     Furthermore, the shield  20  may include an elastic member  29  that may absorb impact applied to the shield  20  from the collision with the helmet main body  11  when the shield  20  is inserted into the inside of the helmet  10 . The elastic member  29  may be made of an elastic material such as rubber and can be insertion-fitted in an upper portion of the shield  20 . 
     The pin lock devices  200  are coupling members that are secured to the shield  20  by being fitted in the lock insertion holes  22  provided in both lateral surfaces of the shield  20 . The pin lock devices  200  support the films  220  and  240  to be described later in detachable manner. For the purpose, each pin lock device  200  may include the lock pin  210  and the lock base  230 . 
     The lock pin  210  is a coupling member inserted from the inside of the lock insertion hole  22  to the outside thereof. The lock pin  210  may include a pin protrusion  211 , a pin supporting plate  213  and a pin handle  215 . 
     The pin protrusion  211  is a protrusion outwardly fitted into the lock base  230  through the lock insertion hole  22 . 
     The pin supporting plate  213  is a protruding member firmly in contact with the lock insertion hole  22  at the inner side of the shield  20  to stop further outward movement of the lock pin  210 . 
     The pin handle  215  is a handle of the lock pin  210 , and it is extended inward from the pin supporting plate  213  and is configured as a head of the lock pin  210 . 
     Further, the lock pin  210  may further include a pin groove  217 . 
     The pin groove  217  is a curved cut portion formed between the pin supporting plate  213  and the pin handle  215  and having a cross section smaller than cross sections of the pin supporting plate  213  and the pin handle  215 . 
     As illustrated in  FIGS. 3A and 3B , the lock pin  210  is engaged with the lock base  230  with the shield  20  positioned therebetween. The anti-moisture film  220  can be detachably fitted to the lock pin  210 . 
     The anti-moisture film  220  is secured to the inner side of the shield  20  and prevents the shield  20  to become foggy due to moisture generated when the user of the helmet  10  breathes. The anti-moisture film  220  may be provided with engagement grooves  227  along both end portions thereof. 
     As shown in  FIGS. 3A and 3B , each engagement groove  227  may be formed in a wave shape and is fitted to the pin groove  217  formed on the lock pin  210 . 
     The anti-moisture film  220  is secured to the shield  20  by engaging the engagement grooves  227  formed at both ends of the anti-moisture film  220  with the pin grooves  217  of the lock pins  210  inserted in both lateral surfaces of the shield  20 . At this time, since the anti-moisture film  220  is bent or deformed, it can be secured to or separated from the inner side of the shield  20  without having to separate the lock pins  210  or the like. Here,  FIGS. 3A and 3B  only shows an example of the engagement grooves  227 , and the engagement grooves  227  may have various other shapes and cross sections as long as they can be engaged with the pin grooves  217 . Furthermore, the anti-moisture film  220  may be made of such a material as plastic having a light shielding effect so as to protect the driver&#39;s eyes by blocking sun light during day time, thus allowing sufficient field of vision even under strong sun light or reflection light. 
     As shown in  FIG. 3A , the lock base  230  is a coupling member engaged with the lock pin  210  from the outside of the lock insertion hole  22 . The lock base  230  may include a base protrusion  231  formed at a center (center position, see  FIG. 6A  for more detail) of the lock base  230 ; a cavity  231   a ; a protrusion accommodating part  231   b ; and a base supporting plate  233 . 
     The base protrusion  231  is a protrusion to be accommodated in the lock insertion hole  22  and having therein the cavity  231   a  into which the lock pin  210  is inserted. The cavity  231   a  may be formed in a straight line shape, and the pin protrusion  211  inserted into the cavity  231   a  may have a straight line shape corresponding thereto. That is, the cavity  231   a  and the pin protrusion  211  are formed in mutually corresponding shapes. Accordingly, when the pin protrusion  211  inserted in the cavity  231   a  is rotated within the lock base  230  in a secured state, the pin protrusion  211  comes out of the cavity  231   a  and becomes positioned on the protrusion accommodating part  231   b , allowing the lock pin  210  to be fixed in place (see  FIG. 8  for more detail). 
     The cavity  231   a  extending from the inside of the base protrusion  231  may be formed through the lock base  230 . Further, the protrusion accommodating part  231   b  may be formed around the cavity  231   a  (see  FIG. 8  for more detail). 
     The protrusion accommodating part  231   b  is an inner region of the lock base  230  formed around the cavity  231   a  and blocked in an inward direction of the shield  20  so as to prevent unintended separation of the lock pin  210  which is inserted into and engaged with the lock base  230 . Accordingly, if the lock pin  210  inserted into the lock base  230  comes out of the cavity  231   a  by rotation and is positioned on the protrusion accommodating part  231   b  (see  FIG. 8  for more detail), unintended separation of the lock pin  210  from the lock base  230  can be avoided. Thus, in the state that lock pin  210  or the lock base  230  are secured to the shield  20 , the user of the helmet  10  can still rotate the lock pin  210  or the lock base  230  freely in clockwise direction or counterclockwise direction. Meanwhile, to separate the lock pin  210  from the lock base  230 , the user of the helmet  10  may pull the lock pin  21  toward the inner side of the shield  20 , thus allowing the lock pin  210  to be separated and removed from the lock base  230 . 
     The base supporting plate  233  is a protruding member firmly in contact with the lock insertion hole  22  from the outer side of the shield  20  to stop inward movement of the lock base  230 . 
     Further, the lock base  230  may include, as illustrated in  FIG. 3B , a base protrusion  231  protrudently formed at an eccentric position (see  FIG. 6B  for more detail), a base supporting plate  233  and a base handle  235 . The base protrusion  231  protrudently formed at the eccentric position is a protrusion protrudently formed in a direction toward the shield  20  at a position deviated from a center of the lock base  230 . 
     The base handle  235  is a handle of the lock base  230 , and it is extended outward from the base supporting plate  233  and is configured as a head of the lock base  230 . The base handle  235  may be useful when the user of the helmet  10  rotates the lock base  230  secured to the shield  20  in clockwise direction or counterclockwise direction. 
     Furthermore, the lock base  230  may further include a base groove  237 . 
     The base groove  237  is a curved cut portion formed between the base supporting plate  233  and the base handle  235  and having a cross section smaller than cross sections of the base supporting plate  233  and the base handle  235 . 
     As illustrated in  FIG. 4 , the lock base  230  is engaged with the lock pin  210  with the shield  20  positioned therebetween. The shield protective film  240  can be detachably fitted to the lock base  230 . 
     The shield protective film  240  is secured to the outer side of the shield  20  and protects the shield  20  so as to prevent generation of, e.g., scratch on the shield  20  even in case an impact is applied to the shield  20  from the outside of the helmet  10  or the shield  20  collides with an external object. Further, the shield protective film  240  can prevent contamination of the shield  20  with dirt or the like. By replacing the shied protective film  240 , clean field of vision can be secured continuously. Further, the shield protective film  240  may have engagement grooves  247  at both end portions thereof. 
     As illustrated in  FIG. 4 , the engagement grooves  247  may be formed at both end portions of the shield protective film  240 . As the engagement groove  247  is engaged with the base groove  237  formed at the lock base  230 , the shield protective film  240  can be secured to the lock base  230 . 
     Below, a principle for adjusting a distance between the lock bases  230  by the rotation of the lock bases  230  will be described with reference to  FIGS. 5A and 5B , wherein the lock bases  230  are secured to the shield  20  with eccentric structure (eccentric position). 
       FIGS. 5A and 5B  show a state in which the lock base  230  engaged with the lock pin  210  through the lock insertion hole  22  rotates about the base protrusion  231  located at an eccentric position.  FIG. 5A  shows a state in which a center of the base protrusion  231  is positioned outside a center of the lock base  230 , and  FIG. 5B  shows a state in which the center of the base protrusion  231  is positioned inside the center of the lock base  230 . 
     As illustrated in  FIGS. 5A and 5B , the center of the lock base  230  varies depending on the rotation of the lock base  230 , whereas the center of the base protrusion  231  is fixed since the base protrusion  231  is rotated while it is secured to the lock pin  210 . Accordingly, in case that the base protrusion  231  is located at the eccentric position of the lock base  230 , the distance between the lock bases  230  secured to both lateral surfaces of the shield  20  is varied as the lock base  230  rotates. 
     In case that the centers of the base protrusions  231  located at both lateral sides of the shield  20  are positioned outside the centers of the lock base  230  ( FIG. 5 ), a distance X between the lock bases  230  may be shortened as compared to a case in which the base protrusions  231  are located at the centers of the lock bases  230 . Further, in case that the centers of the base protrusions  231  are positioned inside the centers of the lock bases  230  ( FIG. 5B ), a distance between the lock bases  230  may be increased as compared to a case in which the base protrusions  231  are located at the centers of the lock bases  230 . Accordingly, Y is larger than X. That is, the distance between the lock bases  230  increases if the base protrusions  231  in the eccentric positions are located inside the centers of the lock bases  230 , while the distance between the lock bases  230  decreases if the base protrusions  231  in the eccentric positions are located outside the centers of the lock bases  230 . 
     Accordingly, the shield protective film  240  fitted to the base groove  237  as the curved cut portion of the lock base  230  can be tightened or loosened so as to be separated from the base groove  237  depending on the variable distance between the lock bases  230  secured to both lateral surfaces of the shield  20 . Accordingly, when the shield protective film  240  needs to be replaced, the shield protective film  230  can be easily removed from the shield  20  by rotating the lock bases  230  so that the distance between the lock bases  230  is shortened. Further, the shield protective film  240  can be made to come into firm contact with the shield  20  by rotating the lock bases  230  such that the distance between them increases. For the purpose, the shield protective film  240  may be formed of a transparent elastic member. 
     Hereinafter, engagement of the lock pin  210  with the lock base  230  will be described with reference to  FIGS. 6A to 8 . 
       FIGS. 6A and 6B  are cross sectional views illustrating the lock pin  210  and the lock base  230  before they are engaged with each other.  FIG. 6A  shows a state in which the lock pin  210  is fitted into a center position of the lock base  230 , and  FIG. 6B  shows a state in which the lock pin  210  is fitted into an eccentric position of the lock base  230 . 
     As shown in  FIGS. 6A and 6B , the lock pin  210  has the pin protrusion  211  capable of being fitted into the lock base  230 . Further, the lock pin  210  may include the pin supporting plate  213 , the pin handle  215  and the pin groove  217 . 
     The lock base  230  is a coupling member into which the lock pin  210  can be inserted through the cavity  231   a  formed at the inside of the lock base  230 . The lock base  230  may include the base protrusion  231 , the base supporting plate  233 , the base handle  235  and the base groove  237 . The base protrusion  231  may be protrudently formed at the center position of the lock base  230 , as illustrated in  FIG. 6A , or it can be protrudently formed at the eccentric position deviated from the center of the lock base  230 , as illustrated in  FIG. 6   b . Further, the base protrusion  231  is formed so as to be accommodated in the lock insertion hole  22  while allowing the pin protrusion  211  to be inserted therein. The lock base  230  may have the protrusion accommodating part  231   b  formed around the cavity  231   a  within the lock base  230  so as to prevent unintended separation of the lock pin  210 . 
     As depicted in  FIGS. 6A and 6B , the protrusion accommodating part  231   b  is an inner blocked region of the lock base  230  formed to prevent unintended separation of the inserted and rotated pin protrusion  211  from the lock base  230 . 
       FIG. 7  provides a cross sectional view showing a state immediately after the lock pin  210  is inserted into the lock base  230 .  FIG. 7  also provides a partial enlarged view of an inserted part. 
     As illustrated in  FIG. 7 , the lock pin  210  can be engaged with the lock base  230  as the pin protrusion  211  is inserted into the cavity  231   a  of the lock base  230 . The shield  20  is positioned between the lock pin  210  and the lock base  230  (indicated by an arrow A). Further, the anti-moisture film  210  may be insertion-fitted between the pin supporting plate  213  and the pin handle  215  of the lock pin  210  (indicated by an arrow B). Furthermore, the shield protective film  240  may be fitted between the base supporting plate  233  and the base handle  235  (indicated by an arrow C). As can be seen in  FIG. 7 , the lock pin  210  and the lock base  230  can be secured to the anti-moisture film  220  and the shield protective film  240 , respectively. Thus, either one of the films may be secured to the shield  20  or both of them may be secured to the shield  20 . In this way, the anti-moisture film and the shield protective film can be fastened to the inner side and the outer side of the shield  20  and removed therefrom easily when replacement thereof is required. 
     Further, as shown in the partial enlarged view of  FIG. 7  (solid line indicates portions shown in the cross section of  FIG. 7 , and dotted line indicates the rest lock base and lock pin portions not shown in the cross section of  FIG. 7 ). Immediately after inserted into the lock base  230 , the pin protrusion  211  is located on the cavity  231   a  formed through the base protrusion  231 . Accordingly, when the lock pin  210  is moved in an inward direction of the shield  20  (in a direction in which the lock pin is separated from the lock base), the lock pin  210  can be easily separated from the lock base  230  without being interfered by the lock base  230 . That is, the lock pin  210  can be easily separated and removed from the lock base  230  just by pulling the lock pin  210  inserted in the lock base  230  in the inward direction again. 
       FIG. 8  provides a cross sectional view illustrating engagement of the lock pin  210  with the lock base  230  through rotation.  FIG. 8  also provides a partial enlarged view of an engaged part. 
     As shown in  FIG. 8 , if the lock pin  210  inserted in the lock base  230  is rotated, the pin protrusion  211  is also made to rotate within the lock base  230  in the same direction. 
     As can be seen from the partial enlarged view of  FIG. 8  (solid line indicates portions shown in the cross section of  FIG. 8 , and dotted line indicates the rest lock base and lock pin portions not shown in the cross section of  FIG. 8 ), the pin protrusion  211  rotated while inserted in the lock base  230  (secured rotation) is moved out of the position on the cavity  231   a  where insertion and separation is freely possible and then becomes to be positioned on the protrusion accommodating part  231   b  where separation (of the lock pin from the lock base) is restricted (secured state). As stated above, the protrusion accommodating part  231   b  is a region formed within the lock base  230  to be located around the cavity  231   a  of the lock base  230  so as to prevent the movement of the pin protrusion  211  in a direction in which it is separated from the lock base  230 . Accordingly, if the pin protrusion  211  comes out of the cavity  231   a  and is positioned on the protrusion accommodating part  231   b  (i.e., comes into secured state through secured rotation) as the lock pin  210  rotates while inserted in the lock base  230 , the lock pin  210  is engaged with the lock base  230  to be firmly secured thereto. That is, the lock pin  210  (pin protrusion  211 ) inserted into the lock base  230  is secured to the lock base  230  through secured rotation and can be prevented from being separated or removed from the lock base  230  in unintended manner. In this way, when the pin protrusion  211  of, e.g., the straight line shape is inserted in the cavity  231   a  having the mutually corresponding shape thereto is rotated within the lock base  230  in secured state, the pin protrusion  211  becomes to come out of the cavity  231   a  and be positioned on the protrusion accommodating part  231   b , thus allowing the lock pin  210  to be firmly fixed in place. 
     Meanwhile, the user of the helmet  10  may separate the lock pin  210  from the lock base  230  by rotating (unsecure rotating) the lock pin  210  secured to the lock base  230  and thus making the pin protrusion  211  positioned on the cavity  231   a  again (unsecured state). That is, the lock pin  210  in the secured state is turned into the unsecured state through unsecure rotation. Then, the user of the helmet  10  may pull the unsecured lock pin  210  in the inward direction of the shield  20  and separate the lock pin  210  from the lock base  230  and from the shield  20 . 
     The above description of the present invention is provided for the purpose of illustration, and it would be understood by those skilled in the art that various changes and modifications may be made without changing technical conception and essential features of the present invention. Thus, it is clear that the above-described embodiments are illustrative in all aspects and do not limit the present invention. 
     The scope of the present invention is defined by the following claims rather than by the detailed description of the embodiment. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.