Patent Publication Number: US-9402434-B2

Title: Helmet shield attaching mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to JP 2013-116710, filed Jun. 3, 2013, the disclosure of which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a helmet shield attaching mechanism comprising a shield attaching base member attaching to a head protecting body, and a shield whose region including one of a left end and a right end and a vicinity thereof rotatably attaches to the shield attaching base member, the shield attaching base member comprising a stationary base member attaching to the head protecting body, and a movable base member attaching to the stationary base member so as to be movable forward and backward substantially in the back-and-forth direction with respect to the stationary base member, and the shield being substantially rotatably supportable by the movable base member. 
     BACKGROUND OF THE INVENTION 
     A full-face-type helmet including a pair of left and right shield attaching mechanisms having the above-described arrangement is disclosed in EP 1 856 999 A2. In the shield attaching mechanism of EP 1 856 999 A2, a cam face is provided on the shield, and a cam follower portion is provided on the stationary base member so as to be able to abut against the cam face. In addition, when a force in a substantially rising direction is applied to the shield in a fully-closed state, the cam follower portion relatively follows the cam face, and the shield can thus move forward substantially to a front side together with the movable base member. 
     Hence, according to the shield attaching mechanism of EP 1 856 999 A2, the shield can rise without being caught by the window opening rim member of the head protecting body or the like. Additionally, although the shield attaching mechanism has a relatively simple structure, the shield can be pulled forward and then raised only by performing an operation of pulling the shield in the fully-closed state upward. For this reason, the operation of pulling the shield in the fully-closed state upward is relatively easy and relatively reliable, and no operation error occurs substantially. 
     In the shield attaching mechanism of EP 1 856 999 A2, however, it is cumbersome to do an adjustment operation so as to satisfactorily bring the inner surface of the shield into close contact with the window opening rim member attaching to the window opening of the head protecting body in the fully-closed state of the shield. More specifically, in this adjustment operation, it is necessary to remove the shield from the shield attaching mechanisms in advance, loosen two male screw members that attach the stationary base member to the head protecting body, and then adjust the attachment position of the stationary base member with respect to the head protecting body in the back-and-forth direction. It is relatively difficult to satisfactorily bring the inner surface of the shield into close contact with the window opening rim member only by performing the adjustment operation once. 
     SUMMARY OF THE INVENTION 
     The present invention is aimed at effectively correcting the above drawbacks of the helmet shield attaching mechanism disclosed in EP 1 856 999 A2 with a relatively simple arrangement. 
     According to the present invention, there is provided a helmet shield attaching mechanism comprising a shield attaching base member attaching to a head protecting body, and a shield whose region including one of a left end and a right end and a vicinity thereof rotatably attaches to the shield attaching base member, the shield attaching base member comprising a stationary base member attaching to the head protecting body, and a movable base member attaching to the stationary base member so as to be movable forward and backward substantially in a back-and-forth direction with respect to the stationary base member, and the shield being substantially rotatably supportable by the movable base member, wherein the stationary base member comprises stopper means, the movable base member comprises stopped means whose position can be held by the stopper means in an at least substantially fully-closed state of the shield, and when a holding position of the stopped means whose position is held by the stopper means in the at least substantially fully-closed state of the shield is selected from one of a plurality of portions of the movable base member substantially in the back-and-forth direction, the holding position substantially in the back-and-forth direction of the shield with respect to the head protecting body in the at least substantially fully-closed state can be selected. With this arrangement, an adjustment operation for satisfactorily bringing the inner surface of the shield in the substantially fully-closed state into close contact with the window opening rim portion of the head protecting body is relatively easy. In addition, the adjustment operation can be performed relatively accurately. 
     In the present invention, the movable base member can be configured to be substantially linearly movable forward and backward substantially in the back-and-forth direction with respect to the stationary base member. With this arrangement, an operation of moving the shield upward and downward can be performed relatively easily and relatively reliably. 
     In the present invention, the mechanism can further comprise elastic biasing means capable of elastically biasing the movable base member substantially backward to the stationary base member, and in the at least substantially fully-closed state, the stationary base member may be configured to elastically biased by the elastic biasing means and held at a backward moving position so as to make the stopped means abut against the stopper means. With this arrangement, the movable base member can relatively reliably be held at the backward moving position with respect to the stationary base member by a relatively simple structure. In this case, the stopped means preferably comprises a plurality of stopped means. The number of stopped means is more preferably 3 to 7 and most preferably 4 to 6. 
     In the present invention, the mechanism can further comprise a shield position adjustment pivotal manipulation member attaching to one of the movable base member and the stationary base member so as to be able to rotate, rotation preventing means provided on the one of the movable base member and the stationary base member, and back-and-forth positioning means provided on the other of the movable base member and the stationary base member, the pivotal manipulation member comprising a plurality of first recess/projection engaging means configured to selectively engage with the back-and-forth positioning means, and a plurality of second recess/projection engaging means configured to selectively engage with the rotation preventing means, wherein when the back-and-forth positioning means selectively engages with one of the plurality of first recess/projection engaging means, the holding position substantially in the back-and-forth direction of the shield can be selected, and when the rotation preventing means selectively engages with one of the plurality of second recess/projection engaging means, unwanted pivot of the pivotal manipulation member can be prevented. With this arrangement, the adjustment operation can be performed more accurately by a simpler structure. In this case, the number of the plurality of second recess/projection engaging means is preferably 3 to 7, and more preferably 4 to 6. 
     In the present invention, positions of the stopped means can be held by the stopper means only in the substantially fully-closed state and a substantially fully-open state of the shield. With this arrangement, an operation of setting the shield at the intermediate state between the substantially fully-closed state and the substantially fully-open state can be performed relatively easily. Hence, the mechanism for opening/closing the shield can have a relatively simple structure. 
     In the present invention, the shield can comprise a finger rest provided in a region including a lower end and a vicinity thereof of at least one of a left portion and a right portion of the shield, the finger rest being inclined downward substantially from a rear side substantially to a front side. With this arrangement, a force for moving the finger rest substantially forward is applied to the finger rest only by adding a force for substantially raising the shield to the finger rest. Hence, the operation of raising the shield is relatively easily. 
     In the present invention, a cam face is provided on one of the stationary base member and the shield, a cam follower portion is provided on the other of the stationary base member and the shield, and when a force that substantially raises the shield in the substantially fully-closed state is applied to the shield, the cam follower portion relatively follows the cam face so that the shield can also move substantially forward. With this arrangement, the shield can be pulled forward and then raised only by performing an operation of pulling the shield in the fully-closed state upward. For this reason, the operation of pulling the shield in the fully-closed state upward is relatively easy, and the shield can relatively reliably be moved upward and downward. In this case, the cam face can comprise a stopper recess configured to hold the shield at a substantially fully-closed position, an inclined surface configured to move the shield substantially forward, and a click tooth portion configured to hold the shield stepwise. With this arrangement, the operation of moving the shield in the fully-closed state upward is further reliable, and the operation of moving the shield downward is also reliable. 
     In the present invention, a shield attaching/removing manipulation member manipulated to remove the shield from the movable base member can be disposed on the movable base member so as to be movable forward and backward, and when the shield is rotated forward to the substantially fully-open state, and thereafter, the shield attaching/removing manipulation member is moved forward, a removable state of the shield can be obtained. With this arrangement, the shield removing operation can be performed relatively easily and relatively reliably. 
     The above, and other, objects, features and advantages of the present 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 schematic left side view of a helmet as a whole, in which a shield is in a fully-closed state, according to an embodiment in which the present invention is applied to a full-face-type helmet shield attaching mechanism. 
         FIG. 2  is an enlarged left side view of the main part of the helmet to show the shield attaching mechanism in  FIG. 1 . 
         FIG. 3  is an enlarged left side view similar to  FIG. 2 , in which the shield is in a stage-1 open state. 
         FIG. 4  is an enlarged left side view similar to  FIG. 2 , in which the shield is in a stage-2 open state. 
         FIG. 5  is an enlarged left side view similar to  FIG. 2 , in which the shield is in a fully-open state. 
         FIG. 6  is an enlarged left side view, similar to  FIG. 5 , of a state wherein a shield attaching/removing manipulation lever is pivoted forward. 
         FIG. 7  is an enlarged left side view, similar to  FIG. 4 , of a state wherein a shield position adjustment operation button is pivoted forward. 
         FIG. 8  is an enlarged left side view, similar to  FIG. 2 , of a state wherein the shield is changed for the state shown in  FIG. 7  to a fully-closed state. 
         FIG. 9  is an exploded front view of the shield attaching mechanism in  FIG. 1 . 
         FIG. 10  is an enlarged front view of a movable base member shown in  FIG. 9 . 
         FIG. 11  is an enlarged left side view, similar to  FIG. 2 , of the helmet before the shield attaching mechanism is built into the head protecting body. 
         FIG. 12  is an enlarged left side view, similar to  FIG. 11 , of the helmet with the stationary base member of the shield attaching mechanism being built into the head protecting body. 
         FIG. 13  is an enlarged left side view, similar to  FIG. 11 , of the helmet with the stationary base member and movable base member of the shield attaching mechanism being built into the head protecting body. 
         FIG. 14  is an enlarged left side view, similar to  FIG. 2 , of the helmet from which the shield has been removed. 
         FIG. 15  is an enlarged left side view of the shield attaching mechanism shown in  FIG. 2 . 
         FIG. 16  is an enlarged left side view of part of the shield attaching mechanism shown in  FIG. 15 . 
         FIG. 17  is an enlarged left side view of a part of the shield attaching mechanism shown in  FIG. 8 . 
         FIG. 18  is an enlarged left side view of a part of the shield attaching mechanism when a shield position adjustment pivotal manipulation button is set in an intermediate state between the state shown in  FIG. 16  and the state shown in  FIG. 17 . 
         FIG. 19  is an enlarged left side view of a part of the shield attaching mechanism when the stationary base member attachment position is changed in the state shown in  FIG. 16 . 
         FIG. 20  is a sectional view taken along a line A-A in  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment in which the present invention is applied to a shield attaching mechanism for a full-face-type helmet will be described in “1. Schematic Arrangement of Helmet as a Whole”, “2. Arrangement of Shield Attaching Mechanism” and “3. Operation of Shield Attaching Mechanism” with reference to  FIGS. 1 to 20 . 
     1. Schematic Arrangement of Helmet as a Whole 
     As shown in  FIG. 1 , a full-face-type helmet  1  comprises a full-face-type head protecting body  2  to be worn on the head of a helmet wearer such as a motorcycle rider, a shield  4  which can open/close a window opening  3  formed in the front surface of the head protecting body  2  so as to oppose a portion between the forehead and chin (that is, the central portion of the face) of the helmet wearer, and a pair of left and right chin straps (not shown) attaching to the inner side of the head protecting body  2 . Of the head protecting body  2 , each of those portions which oppose the chin, forehead and the like of the helmet wearer is provided with one or a plurality of ventilators (not shown), where necessary, to ventilate air in the head protecting body  2 . The shield  4  is provided to the helmet  1  to serve as a windshield. Where necessary, the shield  4  may be colored not to particularly interfere with the translucence so it can also serve as a sun visor (that is, a visor). The shield  4  can be made of a transparent or translucent hard material such as polycarbonate or another synthetic resin. A pair of left and right shield attaching mechanisms  6  pivotally attaches regions including the left and right side portions and vicinities thereof of the shield  4  to an outer shell  5  which constitutes the outer wall of the head protecting body  2 . 
     An anti-fogging auxiliary shield (not shown) which can be made of a transparent or translucent hard material such as polycarbonate or another synthetic resin can removably attach to the inner surface of the shield  4  shown in  FIGS. 1 and 2  to form a small gap with the shield  4 . To attach the anti-fogging auxiliary shield, a pair of left and right engaging pins (not shown) respectively having engaging ring-like grooves can attach and fix to those portions of the left and right sides of the inner surface of the shield  4 , which are slightly below the central portions, by screwing or the like. A pair of left and right tongue pieces can project from those portions of the left and right ends of the anti-fogging auxiliary shield which are slightly below the central portions in a substantially vertical direction. The pair of left and right tongue pieces can respectively have a pair of left and right engaging slits which are open backwardly. The pair of left and right engaging pins can respectively fit in the pair of left and right engaging slits to attach the anti-fogging auxiliary shield to the inner surface of the shield  4 . A packing projecting ridge (not shown) made of an elastic material such as silicone rubber can form a loop along the outer periphery of a region of the outer surface of the anti-fogging auxiliary shield except for the pair of left and right tongue pieces so that the anti-fogging auxiliary shield holds the small gap with the shield  4 , and holds the gap airtightly. 
     As is conventionally known, the outer shell  5  can be made of a strong hard material such as FRP or another synthetic resin. As shown in  FIG. 1 , a window opening rim member  8  having a substantially U- or E-shaped section attaches to substantially the entire periphery of a window opening  7 , which is formed in the outer shell  5  to form the window opening  3  of the full-face-type head protecting body  2 , by, for example, adhesion with an adhesive, double-sided adhesive tape, or the like, as has been conventionally known. As shown in  FIGS. 1 and 11 , the lower end of the shield  4  which is fully closed abuts against a projecting ridge  8   a  which substantially horizontally continues at the lower end of the window opening rim member  8  along the lower end of the window opening  7 . A lower end rim member  11  having a substantially U-shaped section or the like attaches to substantially the entire periphery of the lower end of the outer shell  5  by, for example, adhesion with an adhesive or double-sided adhesive tape, or the like. As is conventionally known, the window opening rim member  8  can be made of synthetic rubber or another flexible elastic material. As is conventionally known, the lower end rim member  11  can be made of a soft material such as foamed vinyl chloride, synthetic rubber, or another soft synthetic resin. In  FIG. 1 , reference numeral  12  denotes a finger rest which is integrally provided to the lower end of the left portion of the shield  4 . The helmet wearer places his fingers on the finger rest  12  when reciprocally pivoting the shield  4  upward and downward. Note that the finger rest  12  is gradually inclined downward substantially from the rear side substantially to the front side. For this reason, when the helmet wearer or the like presses the finger rest  12  substantially upward by his finger, the press force generates a component of force oriented forward. Hence, both a first force oriented substantially upward and a second force oriented substantially forward are applied to the shield  4 . 
     The right (the left side to the front surface of the helmet) shield attaching mechanism  6  is axi-symmetrical with the left shield attaching mechanism  6 . Hence, in the following description, a description on the right shield attaching mechanism  6  will not be repeated, and only the left shield attaching mechanism  6  will be described. 
     2. Arrangement of Shield Attaching Mechanism 
     As shown in  FIG. 9 , the left shield attaching mechanism  6  can include members described in the following items (a) to (d): 
     (a) a shield attaching base member  15  which includes a stationary base member  13  and movable base member  14  and is used to attach the shield  4  to the head protecting body  2 ; 
     (b) a shield attaching/removing manipulation lever  16  which is manipulated when removing the shield  4  from the movable base member  14  and, in some cases, when attaching the shield  4  to the movable base member  14 ; 
     (c) a shield position adjustment pivotal manipulation button  17  (in other words, a pivotal manipulation member such as a pivotal manipulation rotor or pivotal manipulation selector serving as a shield position adjustment operation member) which can have a substantially flat cylindrical shape or substantially button shape and is manipulated when finely adjusting the fully-closed position of the shield  4  substantially in the back-and-forth direction; and
 
(d) the shield  4  whose region including the left end and a vicinity thereof can removably attach to the movable base member  14 .
 
     Hence, the arrangement of the left shield attaching mechanism  6  will be described below in “(1) stationary base member”, “(2) movable base member”, “(3) shield attaching/removing manipulation lever”, “(4) pivotal manipulation button”, “(5) shield” and “(6) assembly of shield attaching mechanism” with reference to  FIGS. 1 to 20 . Note that each of the stationary base member  13 , movable base member  14 , shield attaching/removing manipulation lever  16  and pivotal manipulation button  17  can be made of an appropriate material, for example, a synthetic resin such as a polyacetal resin. 
     (1) Stationary Base Member 
     As shown in  FIGS. 9 and 12 , the stationary base member  13  of the shield attaching base member  15  forms an approximately or substantially triangular frame structure having a large central through hole  21 . The stationary base member  13  forms an approximately or substantially plate-like shape except that it has the large central through hole  21 . A pair of male screw members  23   a  and  23   b  inserted in upper and lower screw insertion holes  22   a  and  22   b  attach and fix the stationary base member  13 , as shown in  FIG. 12 , to the head protecting body  2  shown in  FIG. 11 . Note that as shown in  FIG. 11 , a pair of upper and lower female screw members  24   a  and  24   b  are fixed, in a buried state, to a portion of the outer shell  5  behind the window opening  7  (that is, the right side in  FIG. 11 ). To attach and fix the stationary base member  13 , the pair of male screw members  23   a  and  23   b  are screwed and fixed in screw holes  25   a  and  25   b  of the pair of upper and lower female screw members  24   a  and  24   b  from the outer surface of the stationary base member  13 . The inner surface of the stationary base member  13  preferably forms an arcuate shape which slightly rises toward the outer surface so as to substantially coincide with the arcuate shape of the outer surface of the outer shell  5 . The movable base member  14  also preferably forms such an arcuate shape. 
     As shown in  FIG. 9 , the stationary base member  13  includes a pair of upper and lower high-level portions  28   a  and  28   b  formed from thick portions so as to surround the pair of upper and lower male screw members  23   a  and  23   b  (in other words, the pair of upper and lower screw insertion holes  22   a  and  22   b  which receive the pair of upper and lower male screw members  23   a  and  23   b , respectively), respectively. The pair of high-level portions  28   a  and  28   b  have a pair of upper and lower guide grooves  26   a  and  26   b  and a pair of upper and lower guide grooves  27   a  and  27   b  substantially on the upper and lower sides of the pair of upper and lower screw insertion holes  22   a  and  22   b , respectively. In this case, the direction of depth of each of the upper guide grooves  26   a  and  27   a  can be substantially downward substantially from above. The direction of depth of each of the lower guide grooves  26   b  and  27   b  can be substantially upward substantially from below. The stationary base member  13  has a pair of upper and lower spring accommodating recesses  32   a  and  32   b , at portions on its outer surface substantially behind the pair of upper and lower male screw members  23   a  and  23   b , to accommodate a pair of upper and lower repulsive coil springs  31   a  and  31   b  serving as elastic biasing means. Spring engaging projections  33   a  and  33   b  are formed on the wall portions substantially on the front side of the pair of upper and lower recesses  32   a  and  32   b.    
     As shown in  FIG. 9 , a high-level portion  34  formed from a thick portion is formed in a region including the upper end and a vicinity thereof of the stationary base member  13 . A downward guide groove  35  extending from the rear end midway to the front end of the high-level portion  34  is formed in the lower end face of the high-level portion  34 . A high-level portion  36  formed from a thick portion is formed in a region including the intermediate portion and a vicinity thereof on the front side of the stationary base member  13  so as to be located between the central through hole  21  and the front end of the stationary base member  13 . A substantially wavy thin click tooth portion  37  having one or a plurality of teeth (six teeth in  FIG. 9 ), which can be substantially arcuate as a whole, projects from the front end of the high-level portion  36  to form an eaves structure concave on the inner surface side. A cam portion  38  having an inclined surface  38   b  is disposed at the lower front end of the high-level portion  36  so as to run below the click tooth portion  37  configured to hold the shield  4  stepwise. The end (in other words, the lower end) of the cam portion  38  on the side opposite to the click tooth portion  37  forms a stopper recess  38   a . A cam face  39  for the shield  4  (more specifically, a third guided portion  123  to be described later) is formed on the stationary base member  13  by the click tooth portion  37 , cam portion  38  and stopper recess  38   a . A recess  41  to relieve the pivotal manipulation member  17  is formed obliquely below in a region including the lower end and a vicinity thereof of the stationary base member  13  so as to obliquely face forward. In addition, a stopper portion  42  serving as a stopper means and back-and-forth positioning means facing the recess  41  is disposed in the region including the lower end and the vicinity thereof of the stationary base member  13  so as to project toward the recess  41 . 
     (2) Movable Base Member 
     As shown in  FIGS. 9, 10 and 13 , the movable base member  14  of the shield attaching base member  15  has a perimeter larger than that of the stationary base member  13  substantially by one level, and forms a substantially plate-like shape larger than the stationary base member  13 . The movable base member  14  has a pair of upper and lower through holes  51   a  and  51   b , as shown in  FIGS. 9 and 10 . As shown in  FIG. 13 , the high-level portion  28   a , where the pair of upper and lower guide grooves  26   a  and  26   b  substantially at the upper portion of the stationary base member  13  are formed, can be inserted in the upper through hole  51   a . A high-level portion  28   b , where the pair of upper and lower guide grooves  27   a  and  27   b  substantially at the lower portion of the stationary base member  13  are formed, can be inserted in the lower through hole  51   b . A pair of upper and lower guided projecting ridges  52   a  and  52   b  are formed on the front portions of the upper and lower side wall portions of the circumferential wall portion of the upper through hole  51   a , respectively. In addition, a spring engaging projection  50   a  configured to engage with the upper repulsive coil spring  31   a  is formed on the rear side wall portion of the circumferential wall portion. A pair of upper and lower guided projecting ridges  53   a  and  53   b  are formed on the front portions of the upper and lower side wall portions of the circumferential wall portion of the lower through hole  51   b , respectively. In addition, a spring engaging projection  50   b  configured to engage with the lower repulsive coil spring  31   b  is formed on the rear side wall portion of the circumferential wall portion. 
     As shown in  FIG. 10 , the movable base member  14  has a substantially arcuate first guide portion  54  to be adjacent to the front upper end of the movable base member  14 . Note that the first guide portion  54  is formed thin as its inner surface is recessed. The movable base member  14  has a substantially arcuate guide slit  55  to be adjacent to the inner surface of the lower end of the first guide portion  54 . Hence, the guide portion  54  projects in the planar direction of the movable base member  14  to form an eaves structure. The movable base member  14  also has a substantially arcuate second guide portion  56  at a portion on the upper side of the upper through hole  51   a . Note that the second guide portion  56  is formed thin as its inner surface is recessed. The movable base member  14  has a substantially arcuate guide slit  57  to be adjacent to the inner surface of the front end of the second guide portion  56 . Hence, the second guide portion  56  projects in the planar direction of the movable base member  14  to form an eaves structure. Furthermore, a guide projecting ridge  58  projects from the front upper end of the movable base member  14 . 
     As shown in  FIG. 10 , an intermediate through hole  61  is formed between the upper through hole  51   a  and lower through hole  51   b . A substantially arcuate third guide portion  62  is formed between the upper through hole  51   a  and the intermediate through hole  61 . Note that the third guide portion  62  is formed thin as its inner surface is recessed. The movable base member  14  has a substantially arcuate guide slit  63  to be adjacent to the inner surface of the end of the third guide portion  62  on the side of the through hole  51   a . Hence, the third guide portion  62  projects in the planar direction of the movable base member  14  to form an eaves structure. Preferably, each of the center of the virtual circle of the substantially arcuate second guide portion  56  and the center of the virtual circle of the substantially arcuate third guide portion  62  substantially coincides with a common central point C 1  shown in  FIG. 10 . Note that reference numeral  64  in  FIG. 10  denotes an inclined surface obliquely adjacent to the lower rear portion of the intermediate through hole  61 . The inclined surface  64  extends between the intermediate through hole  61  and a strip-shaped high-level portion  65  adjacent to the through hole  61  via the inclined surface  64  so as to incline in the widthwise direction obliquely upward from below. 
     As shown in  FIG. 10 , the movable base member  14  has a substantially arcuate fourth guide portion  66  formed substantially on the front side of the upper through hole  51   a . Preferably, each of the center of the virtual circle of the substantially arcuate fourth guide portion  66  and the center of the virtual circle of the substantially arcuate third guide portion  62  substantially coincides with the common center C 1  shown in  FIG. 10 . Also preferably, the radius (that is, each of the inner diameter and outer diameter) of the virtual circle of the fourth guide portion  66  substantially coincides with the radius (that is, each of the inner diameter and outer diameter) of the virtual circle of the third guide portion  62 . A gap  67  is formed between the free end of the fourth guide portion  66  and the free end of the third guide portion  62 . A first engaging portion  68  having an eaves structure, which can have a substantially triangular shape, is formed at the front corner of the distal end of the fourth guide portion  66 . Substantially arcuate first and second guide grooves  71  and  72  are formed in the third guide portion  62  and the fourth guide portion  66 , respectively, on the side of the central point C 1 . 
     As shown in  FIG. 10 , the movable base member  14  has a through hole (that is, attachment hole)  73  to attach the shield attaching/removing manipulation lever  16  at a portion adjacent to substantially the front side of first engaging portion  68 . The movable base member  14  has a second engaging portion  74  having an eaves structure, which can have a substantially fan shape, at a portion substantially obliquely adjacent to the upper front portion of the through hole  73 . The movable base member  14  also has a spring accommodating opening  76  configured to accommodate a repulsive coil spring  75  at a portion slightly below the through hole  73 . A spring engaging projection  77  is formed on the wall portion substantially on the front side of the spring accommodating opening  76 . A projecting wall portion  78  which can be elongated and have substantially linear shape is formed on the inner surface of the front end of the movable base member  14  so as to be located at a portion substantially in front of the lower through hole  51   b . An attachment hole  79  to attach the pivotal manipulation button  17  is formed in a region including the lower front end and a vicinity thereof of the movable base member  14 . Note that the attachment hole  79  will be described later in detail in “(4) pivotal manipulation button”. 
     (3) Shield Attaching/Removing Manipulation Lever 
     The shield attaching/removing manipulation lever  16  which serves as the shield attaching/removing manipulation member forms a substantially thin plate-like elongated shape, as shown in  FIGS. 9 and 14 . The shield attaching/removing manipulation lever  16  has a pivot axis portion  81  with a screw insertion hole at approximately its intermediate portion. The manipulation lever  16  can pivotally be attached to the movable base member  14  by inserting the pivot axis portion  81  in the through hole  73  of the movable base member  14  from the outer surface of the movable base member  14  and thereafter screwing and fixing a male screw member (not shown) into the screw insertion hole via a safety lock member (not shown) from the inner surface of the movable base member  14 . 
     The shield attaching/removing manipulation lever  16  has a first engaging pawl (in other words, a first lock pawl)  83  at a portion above the pivot axis portion  81  and a second engaging pawl (in other words, a second lock pawl)  84  at a portion below the pivot axis portion  81 , as shown in  FIGS. 9 and 14 . Note that preferably, the first and second engaging pawls  83  and  84  have recessed inner surfaces so they become thin, and their outer surfaces are inclined to their inner surfaces from their proximal ends toward their distal ends so their thicknesses gradually decrease. Hence, each of the first and second engaging pawls  83  and  84  projects in the planar direction of the manipulation lever  16  to form an eaves structure. The manipulation lever  16  has a third engaging pawl (in other words, a third lock pawl)  85  in a region including a portion (and a vicinity thereof) below the second engaging pawl  84 . Note that the third engaging pawl  85  lacks the outer surface side and is formed thin only from the inner surface side. As shown in  FIG. 14 , the substantially arcuate guide  62  of the movable base member  14  engages with the third engaging pawl  85  to prevent the manipulation lever  16  from suspending upward from the movable base member  14 . Also, as shown in  FIGS. 9 and 14 , the shield attaching/removing manipulation lever  16  has a substantially arcuate guided portion  91 , substantially at its upper end, which is thin as its outer surface is recessed. 
     As shown in  FIG. 9 , a ring-like finger rest  92 , where the helmet wearer can place his fingers when pivoting the manipulation lever  16  forward, is integrated with the shield attaching/removing manipulation lever  16  at its lower end. A spring accommodating recess  93 , which is open not only to the inner surface but also to the front side, is formed in the inner surface of the shield attaching/removing manipulation lever  16 , between the pivot axis portion  81  and the finger rest  92 , so as to oppose the spring accommodating opening  76  of the movable base member  14 . A spring engaging projection  94  is formed on the rear side wall portion of the spring accommodating recess  93 . The spring accommodating opening  76  of the movable base member  14  and the spring accommodating recess  93  of the shield attaching/removing manipulation lever  16  accommodate the repulsive coil spring  75  such that its two ends engage with the spring engaging projections  77  and  94 , as shown in  FIG. 14 . 
     As shown in  FIG. 9 , a fourth engaging pawl (in other words, a fourth lock pawl)  95  is integrated with the shield attaching/removing manipulation lever  16  on its front side between the first engaging pawl  83  and the pivot axis portion  81 . Note that the fourth engaging pawl  95  lacks the outer surface side and is formed thin only from the inner surface side. Additionally, a fifth engaging pawl (in other words, a fifth lock pawl)  96  is integrated with the shield attaching/removing manipulation lever  16  on its rear side surface between the pivot axis portion  81  and the second engaging pawl  84 . Note that the fifth engaging pawl  96  also lacks the outer surface side and is formed thin only from the inner surface side. As shown in  FIG. 14 , the first engaging portion  68  and the lower end of the third guide portion  62  of the movable base member  14  engage the fourth and fifth engaging pawls  95  and  96  to prevent the manipulation lever  16  from suspending upward from the movable base member  14 . 
     (4) Pivotal Manipulation Button 
     As shown in  FIGS. 9, 10 and 15 to 20 , the pivotal manipulation button  17  functioning as a shield position adjustment operation member such as a shield position adjustment pivotal manipulation member includes a head portion  97  having a substantially disk-like shape, an intermediate portion  98  having a substantially disk-like shape and concentrically and integrally connected with the lower side of the head portion  97 , and a pair of left and right legs  99   a  and  99   b  integrally connected with the lower side of the intermediate portion  98  and extending substantially downward from the intermediate portion  98 . The upper surface of the head portion  97  has a groove  101  passing through the center portion of the upper surface while substantially extending through the head portion  97 , and a pair of projecting ridges  102   a  and  102   b  extending along both sides of the groove  101 . The intermediate portion  98  has a diameter smaller than that of the head portion  97 . A plurality of (preferably three to seven, more preferably four to six, and in the illustrated embodiment, five) positioning recesses  103  are formed in a circumferential half of the outer periphery of the intermediate portion  98 . A plurality of (preferably three to seven, more preferably four to six, and in the illustrated embodiment, five) stopper engaging recesses  104   a  to  104   e  are formed in the other circumferential half of the outer periphery of the intermediate portion  98 . Note that the number of the positioning recesses  103  is preferably equal to the number of stopper engaging recesses  104   a  to  104   e  serving as stopped means or first recess/projection engaging means. The plurality of positioning recesses  103  serving as second recess/projection engaging means can have the same shape each other and are therefore located substantially equidistantly from a pivot center C 3  of the pivotal manipulation button  17 . The plurality of stopper engaging recesses  104   a  to  104   e  are preferably located at different distances from the pivot center C 3 . In the illustrated embodiment, starting from the stopper engaging recess  104   a  out of the stopper engaging recesses  104   a  to  104   e , the distance sequentially increases in the order of the stopper engaging recesses  104   b ,  104   c ,  104   d  and  104   e.    
     As shown in  FIGS. 18, 20 , and the like, the intermediate portion  98  of the pivotal manipulation button  17  has first and second stopped portions  105   a  and  105   b  integrated with the intermediate portion  98  between the plurality of positioning recesses  103  and the plurality of stopper engaging recesses  104   a  to  104   e . Note that the first stopped portion  105   a  and the second stopped portion  105   b  are limited by a first positioning projection  114  and a second positioning projection  117  not to pivot more than necessary. Each of the pair of left and right legs  99   a  and  99   b  includes a leg main body  106  extending substantially downward from the intermediate portion  98 , and an engaging projection  107  projecting substantially outward substantially in the transverse direction from the lower end of the leg main body  106 . As shown in  FIG. 20 , the intermediate portion  98  of the pivotal manipulation button  17  is fitted in the hole  79  formed in a region including the lower end and a vicinity thereof of the movable base member  14 . In the fitted state, the pair of left and right legs  99   a  and  99   b  of the pivotal manipulation button  17  engages with the inner surface of a substantially circular engaging projecting ridge  108  of the movable base member  14  on the outer periphery of the hole  79 . Note that the hole  79  can have a large diameter on an outer side  109   a , a small diameter at an intermediate portion  109   b , and an intermediate diameter on an inner side  109   c . The projections  107  of the pair of legs  99   a  and  99   b  abut against the intermediate portion  109   b  from the inner side  109   c  and are locked. 
     As shown in  FIGS. 10, 20 , and the like, the movable base member  14  has, on the outer periphery of the outer surface of the hole  79 , a plurality of (preferably three to seven, and in the illustrated embodiment, five) markings  111   a  to  111   e  which partially surround the outer periphery and indicate the pivotal state of the pivotal manipulation button  17 . Note that a pointer  116  capable of facing the markings  111   a  to  111   e  is formed from the groove  101  and the pair of left and right projecting ridges  102   a  and  102   b  provided on the left and right sides of the groove  101 . The markings  111   b  to  111   e  are formed from substantially trapezoidal projecting ridges which sequentially increase the width in the illustrated embodiment. In the illustrated embodiment, the marking  111   a  is formed from a substantially triangular projecting ridge  112  and a projecting ridge  113  extending on the substantially triangular projecting ridge  112  while extending through it substantially in the vertical direction. In the hole  79  of the movable base member  14 , the positioning projection  114  serving as a pivot or rotation preventing means is integrated with the movable base member  14 . A slit  115  is formed in the movable base member  14  on the proximal end side of the positioning projection  114  such that the positioning projection  114  can elastically move substantially forward and backward with respect to the pivot center of the pivotal manipulation button  17 . As shown in  FIGS. 18, 20 , and the like, the stopper portion  42  disposed on the stationary base member  13  selectively engages with one of the stopper engaging recesses  104   a  to  104   e  of the pivotal manipulation button  17 . Note that this engagement is reliably done as the repulsive coil springs  31   a  and  31   b  elastically bias the movable base member  14  with respect to the stationary base member  13  from left to right in  FIGS. 18 and 20 . 
     (5) Shield 
     As shown in  FIG. 9 , a substantially arcuate first guided portion  121 , substantially arcuate second guided portion  122  and substantially arcuate third guided portion  123  are sequentially formed, in a region including the left end of the inner surface and a vicinity thereof of the shield  4  to locate from the left distal end substantially to the central portion side of the shield  4 . Note that preferably, the center of the virtual circle of the substantially arcuate first guided portion  121  and the center of the virtual circle of the substantially arcuate second guided portion  122  coincide with a substantially common central point C 2  shown in  FIG. 9 . As an end of the first guided portion  121  on a side opposite to the central point C 2  is recessed on its outer surface (that is, a surface on the outer surface side of the shield  4 ) side, the first guided portion  101  projects in a direction opposite to the central point C 2  to form an eaves structure. Hence, in the first guided portion  121 , a base wall portion  124  substantially vertically rising from the inner surface of the shield  4 , and an eaves portion  125  extending from the base wall portion  124  substantially parallel to the inner surface of the shield  4  are integrated with each other. As an end of the second guided portion  122  on a side opposite to the central point C 2  is recessed on its outer surface side, as shown in  FIG. 9 , the second guided portion  122  projects in a direction opposite to the central point C 2  to form an eaves structure. Hence, in the second guided portion  122  as well, a base wall portion  126  substantially vertically rising from the inner surface of the shield  4  and, an eaves portion  127  extending from the base wall portion  126  substantially parallel to the inner surface of the shield  4  are integrated with each other. Furthermore, as an end of the third guided portion  123  on the side of the central point C 2  is recessed on its outer surface side, the third guided portion  123  projects in the direction of the central point C 2  to form an eaves structure. Hence, in the third guided portion  123  as well, a base wall portion  128  substantially vertically rising from the inner surface of the shield  4 , and an eaves portion  129  extending from the base wall portion  128  substantially parallel to the inner surface of the shield  4  are integrated with each other. 
     As shown in  FIG. 9 , an arcuate guided wall portion  131  serving as a fourth guided portion is formed on the inner surface of the shield  4  at a small interval from the second guided portion  122 . Note that the center of the virtual circle of the arcuated guided wall portion  131  also preferably substantially coincides with the central point C 2 . The distance from the arcuated guided wall portion  131  to the central point C 2  is preferably substantially the same as the distance from the base portion  128  of the second guided portion  122  to the central point C 2 . The fourth guided portion  131  is preferably formed on the inner surface of the shield  4  at a position obliquely adjacent to the upper side of the base wall portion  126  of the second guided portion  122 . The base portion  128  of the third guided portion  123  is preferably formed into a columnar body having a substantially heart-shaped cross section. In the base portion  128 , two tooth portions  132  and  133  each capable of functioning as a stopper are arranged adjacently on a common arc with respect to the central point C 2  as the center so as to substantially face the central point C 2 . Note that the tooth portions  132  and  133  arranged on the common arc need not always be two tooth portions, and one or three or more tooth portions may be arranged. 
     (6) Assembly of Shield Attaching Mechanism 
     When assembling the shield attaching mechanism  6  shown in  FIG. 2 , operations described in the following items (a) to (e) can sequentially be performed: 
     (a) to attach the pivotal manipulation button  17  to the movable base member  14 , 
     (b) to attach the movable base member  14  to the stationary base member  13 , 
     (c) to attach the shield attaching/removing manipulation lever  16  to the movable base member  14 , 
     (d) to attach a pair of left and right combination structures each comprising the four members  13 ,  14 ,  16  and  17  to the left and right sides of the outer surface of the head protecting body  2 , and 
     (e) to attach regions including the left and right ends and vicinities thereof of the shield to the movable base members  14  on the left and right sides of the head protecting body  2 . 
     The assembling operation of the shield attaching mechanism  6  will be described below sequentially in the order described in the above items (a) to (e). Note that as the right shield attaching mechanism  6  can be assembled in the substantially same manner as that of the assembly of the left shield attaching mechanism  6 , only the assembling operation of the left shield attaching mechanism  6  will be described below. 
     When attaching the pivotal manipulation button  17  shown in  FIGS. 10 and 20  to the movable base member  14  shown in  FIG. 10 , as described in the above item (a), the inner surface of the pivotal manipulation button  17  is overlaid on the outer surface in a region including the attachment hole  79  and a vicinity thereof of the movable base member  14 , as shown in  FIG. 19 . The positioning projection  114  of the movable base member  14  is aligned with one of the plurality of positioning recesses  103  of the pivotal manipulation button  17 . After that, the pivotal manipulation button  17  is pressed into the hole  79 . At this time, engaging projections  107   a  and  107   b  of the pair of left and right legs  99   a  and  99   b  of the pivotal manipulation button  17  are engaged by the engaging projecting ridge  108 . The positioning projection  114  of the movable base member  14  engages with one of the positioning recesses  103  of the pivotal manipulation button  17 . 
     When attaching the movable base member  14  shown in  FIGS. 9 and 10  to the stationary base member  13  shown in  FIG. 9 , as described in the above item (b), the inner surface of the movable base member  14  is overlaid on the outer surface of the stationary base member  13 , as in the case shown in  FIG. 13 . The upper pair of upper and lower guided projecting ridges  52   a  and  52   b  and the lower pair of upper and lower guided projecting ridges  53   a  and  53   b  of the movable base member  14  are relatively fitted in the upper pair of upper and lower guide grooves  26   a  and  26   b  and the lower pair of upper and lower guide grooves  27   a  and  27   b  of the stationary base member  13 , respectively. At this time, the guide projecting ridge  58  of the movable base member  14  is fitted in the guide groove  35  of the stationary base member  13 . Subsequently, the pair of upper and lower repulsive coil springs  31   a  and  31   b  are respectively accommodated in the pair of upper and lower spring accommodating recesses  32   a  and  32   b  of the stationary base member  13 . At this time, the two ends of the upper repulsive coil spring  31   a  engage with the spring engaging projections  33   a  and  50   a , respectively. In addition, the two ends of the lower repulsive coil spring  31   b  engage with the spring engaging projections  33   b  and  50   b , respectively. In this state, as shown in  FIG. 13 , the pair of upper and lower repulsive coil springs  31   a  and  31   b  elastically bias the movable base member  14  substantially backward (that is, substantially to the right in  FIG. 13 ) to hold it at the backward position. More specifically, the movable base member  14  is held at the backward position when one of the plurality of stopper engaging recesses  104   a  to  104   e  of the pivotal manipulation button  17  abuts against the stopper portion  42  of the stationary base member  13 , as shown in  FIGS. 18, 20 , and the like. 
     When attaching the shield attaching/removing manipulation lever  16  shown in  FIG. 9  to the movable base member  14  shown in  FIGS. 9 and 10 , as described in the above item (c), the inner surface of the manipulation lever  16  is overlaid on the outer surface of the movable base member  14 , as shown in  FIG. 14 . At this time, the pivot axis portion  81  is inserted in the through hole  73  of the movable base member  14  from the outer surface of the movable base member  14 . A male screw member (not shown) is screwed and fixed in the screw insertion hole of the pivot axis portion  81  via a safety lock member (not shown) from the inner surface of the movable base member  14 . As a result, the manipulation lever  16  is pivotally axially supported by the movable base member  14 . The common repulsive coil spring  75  is accommodated in the spring accommodating opening  76  of the movable base member  14  and the spring accommodating recess  93  of the manipulation lever  16 . At this time, the two ends of the repulsive coil spring  75  engage with the spring engaging projections  77  and  94 , respectively. Simultaneously, the guided portion  91  of the manipulation lever  16  is inserted in the guide slit  55  of the guide portion  54  of the movable base member  14 . The third engaging pawl  85  of the manipulation lever  16  is inserted in the inner surface side of the third guide portion  62  of the movable base member  14 . Additionally, the fifth engaging pawl  96  of the manipulation lever  16  is inserted in the inner surface side of the first engaging portion  68  of the movable base member  14 . Furthermore, the fourth engaging pawl  95  of the manipulation lever  16  is inserted in the inner surface side of the second engaging portion  74  of the movable base member  14 . 
     In the state where the shield attaching/removing manipulation lever  16  is pivotally axially supported by the movable base member  14 , as described above, the repulsive coil spring  75  elastically biases the manipulation lever  16  counterclockwise in  FIG. 14  about the pivot axis portion  81  as the fulcrum, to dispose the manipulation lever  16  at the backward pivotal position, as shown in  FIG. 14 . A first predetermined portion of the manipulation lever  16  abuts against a second predetermined portion of the stationary base member  13 . In this case, the first predetermined portion can be the upper surface of the finger rest  92  of the shield manipulation lever  16  in  FIG. 9  or another abutting portion. The second predetermined portion can be the upper surface of the third guide  62  of the movable base member  14  in  FIG. 9  or another abutting portion (in other words, a portion against which the first predetermined portion can abut). Note that the manipulation lever  16  can pivot forward against the elastic biasing force of the repulsive coil spring  75  until the finger rest  92 , the end on the opposite side or another abutting portion abuts against the corresponding abutting portion of the movable base member  14 . When the manipulation lever  16  is at the backward pivotal position described above, its first engaging pawl  83  substantially closes a gap  134  between a region including the upper end of the high-level portion  36  and a vicinity thereof of the stationary base member  13  and a region including the front end and a vicinity thereof of the first guide  54  of the movable base member  14 , as shown in  FIG. 14 . The second engaging pawl  84  of the manipulation lever  16  substantially closes a gap  135  between the front end of the third guide  62  of the movable base member  14  and the lower end of the fourth guide  66 . 
     When attaching the assembly structure comprising the four members  13 ,  14 ,  16  and  17  shown in  FIG. 9  to the left side of the outer surface of the head protecting body  2 , as described in the above item (d), first, the pair of male screw members  23   a  and  23   b  shown in  FIG. 9  are inserted in the pair of upper and lower screw insertion holes  22   a  and  22   b  of the stationary base member  13 . Subsequently, the pair of male screw members  23   a  and  23   b  are screwed and fixed in the pair of screw holes  25   a  and  25   b  shown in  FIG. 11  for the pair of male screw members  23   a  and  23   b . In this case, the pair of upper and lower screw insertion holes  22   a  and  22   b  of the stationary base member  13  are formed long substantially in the horizontal direction. For this reason, the attachment position of the stationary base member  13  (in other words, the four members  13 ,  14 ,  16  and  17 ) with respect to the head protecting body  2  substantially in the horizontal direction (in other words, substantially in the back-and-forth direction) can be adjusted to some extent, as shown in  FIG. 19 . 
     When attaching the left end of the shield  4  to the movable base member  14 , as described in the above item (e), the shield attaching/removing manipulation lever  16  shown in  FIG. 14  may be pivoted forward clockwise in  FIG. 14  in advance about the pivot axis portion  81  as the fulcrum against the elastic biasing force of the repulsive coil spring  75  (see  FIG. 6 ). However, the manipulation lever  16  need not always be operated in this manner. In place of this operation, the first guided portion  121 , second guided portion  122  and third guided portion  123  of the shield  4  may be abutted against the second guide  56  of the movable base member  14  and the second lock pawl  84  and first lock pawl  83  of the shield attaching/removing manipulation lever  16 , respectively, and thereafter a region including the left end and a vicinity thereof of the shield  4  may be strongly urged against the movable base member  14 . In this case, the second and third guided portions  122  and  123  of the shield  4  strongly urge the second and first lock pawls  84  and  83  of the manipulation lever  16 . For this reason, the manipulation lever  16  pivots forward against the elastic biasing force of the repulsive coil spring  75 , in the substantially same manner as in the case of the forward pivot operation described above. Consequently, the first guided portion  121  of the shield  4  is inserted in an opening  56   a  of the second guide  56  of the movable base member  14 . Simultaneously, the second guided portion  122  of the shield  4  is positioned in the gap  67  of the movable base member  14 . In addition, the fourth guided portion  131  of the shield  4  is positioned in the second guide groove  72  of the movable base member  14 . Since the eaves portion  129  of the third guided portion  123  of the shield  4  presses the outer surface of the engaging pawl  83  of the manipulation lever  16 , the manipulation lever  16  pivots clockwise in  FIG. 14  about the pivot axis portion  81  as the fulcrum. For this reason, the third guided portion  123  is positioned in the gap  134 , and the elastic biasing force of the repulsive coil spring  75  pivots the manipulation lever  16  backward counterclockwise in  FIG. 6  about the pivot axis portion  81  as the fulcrum. Therefore, the first lock pawl  83  similarly pivots backward and returns to a position facing the eaves portion  129  of the third guided portion  123 . As a result, the second and first engaging pawls  84  and  83  of the manipulation lever  16  prevent the second and third guided portions  122  and  123  of the shield  4  from suspending (that is, separating from the movable base member  14 ). 
     In the above-described state, the shield  4  is in the fully-open state shown in  FIG. 5 . For this reason, the third guided portion  123  of the shield  4  exists in the gap  134  formed by the stationary base member  13  and the movable base member  14 . In this state, the common central point C 1  of the movable base member  14  and the common central point C 2  of the shield  4  substantially match except that they are shifted in the direction of the thickness of the movable base member  14  or stationary base member  13 . 
     The assembling operation described in the above items (a) to (e) can attach the shield attaching mechanism  6  to the head protecting body  2 . 
     3. Operation of Shield Attaching Mechanism 
     The shield  4  can employ at least the states described in the following items (a) to (g): 
     (a) fully-closed state shown in  FIGS. 1 and 2 , 
     (b) stage-1 open state shown in  FIG. 3 , 
     (c) stage-2 open state shown in  FIG. 4 , 
     (d) fully-open state shown in  FIG. 5 , 
     (e) removable state shown in  FIG. 6 , 
     (f) state shown in  FIG. 7  during adjustment, and 
     (g) state shown in  FIG. 8  after adjustment. 
     The operation of the shield attaching mechanism will be described below in “(1) fully-closed state”, “(2) stage-1 open state”, “(3) stage-2 open state”, “(4) fully-open state”, “(5) removable state”, “(6) state during adjustment” and “(7) state after adjustment” with reference to  FIGS. 1 to 20 . 
     (1) Fully-Closed State 
     The shield  4  is in the fully-open state shown in  FIG. 5  immediately after it attaches to the movable base member  14  as described in the above item 2(6). When sufficiently pivoting the shield  4  downward from above about the common central points C 2  at its left and right ends as the pivot center by, for example, placing the fingers on the finger rest  12  of the shield  4 , the shield  4  is set in the fully-closed state shown in  FIG. 2 . In the fully-closed state, the lower end of the shield  4  comes into contact with the projecting ridge  8   a  of the window opening rim member  8 . Also, each of the first and second guided portions  121  and  122  of the shield  4  abuts against one terminal end of the corresponding one of the second and third guides  56  and  62  of the movable base member  14 , or is set in a state immediately before abutting against it. The fourth guided portion  131  of the shield  4  is located in a region including the gap  135  (and a vicinity thereof) out of a moving path formed from the first and second guides  71  and  72  and the gap  135 . The third guided portion  123  is located at a corner  136  of the movable base member  14 . One tooth portion  132  out of the two tooth portions  132  and  133  of the base portion  128  of the third guided portion  123  engages with the stopper recess  38   a  of the stationary base member  13 . Hence, since the third guided portion  123  is sandwiched between the movable base member  14  and the stationary base member  13 , and its position is relatively firmly held, the left end of the shield  4  is attached to the head protecting body  2  in a substantially locked state by the shield attaching base member  15 . Note that the operation of the shield attaching mechanism  6  from the fully-open state to the fully-closed state is substantially opposite to the operation from the fully-closed state to the fully-open state, and a detailed description will not be repeated here. In the fully-closed state shown in  FIG. 2 , the tooth portion  132  of the third guided portion  123  of the shield  4  relatively abuts against the stopper recess  38   a  of the high-level portion  36  of the stationary base member  13 , or is located below the stopper recess  38   a  to be relatively close to it. 
     (2) Stage-1 Open State 
     In the fully-closed state shown in  FIG. 2 , when the shield  4  is slightly raised by, for example, placing fingers of the helmet wearer on the finger rest  12 , it is set in the stage-1 open state shown in  FIG. 3 . When attaining the stage-1 open state, the shield  4  slightly pivots forward clockwise in  FIG. 2  with respect to the movable base member  14  about the common central point C 2  as the pivot center. Hence, the first, second and fourth guided portions  121 ,  122  and  131  of the shield  4  are guided by the second, third and fourth guide portions  56 ,  62  and  66  of the movable base member  14 , respectively. At the same time, the third guided portion  123  of the shield  4  is also guided by the cam portion  38  and the click tooth portion  37  of the stationary base member  13 . For this reason, the first to fourth guided portions  121  to  123  and  131  of the shield  4  pivot forward clockwise in  FIG. 2  about the common central point C 2  as the pivot center. Hence, the tooth portion  132  of the third guided portion  123  engages with the lowermost recess of the click tooth portion  37 . In other words, the lowermost tooth portion of the click tooth portion  37  engages with the recess between the pair of tooth portions  132  and  133  of the third guided portion  123 . As a result, the shield  4  is accurately held in the stage-1 open state shown in  FIG. 3 . 
     When the shield  4  in the fully-closed state shown in  FIG. 2  changes to be set in the stage-1 open state shown in  FIG. 3 , the pair of tooth portions  132  and  133  of the third guided portion  123  of the shield  4  pivots clockwise, as it is pushed out substantially forward (that is, substantially to the left in  FIG. 2 ) by the cam portion  38  of the stationary base member  13 , to ride over the lowermost tooth portion of the click tooth portion  37 . Note that this ride-over takes place when the movable base member  14  substantially linearly moves forward substantially to the front side, together with the shield  4 , with respect to the stationary base member  13  against the elastic biasing forces of the repulsive coil springs  31   a  and  31   b . Therefore, when the shield  4  moves upward to the stage-1 open state, the shield  4  (and accordingly the anti-fogging auxiliary shield attaching to its inner surface as needed) is pushed out to the front side by, for example, 3 mm. Hence, when the shield  4  changes to be set in the stage-1 open state, the shield  4  and anti-fogging auxiliary shield  10  attached as needed do not catch on the window opening rim member  8  (particularly its upper rim portion) to be unable to move upward smoothly. Note that for the ride-over, the shield  4  is moved substantially upward by fingers of the helmet wearer or the like which are placed on the finger rest  12 . In this case, the second force oriented substantially forward is also applied to the shield  4 , as described in section 1. It is therefore possible to smoothly raise the shield  4  to the stage-1 open state. 
     (3) Stage-2 Open State 
     In the stage-1 open state shown in  FIG. 3 , when further pulling up the shield  4  a little, it is set in the stage-2 open state shown in  FIG. 4 . Note that when setting the shield  4  in the stage-2 open state, it further pivots a little clockwise in  FIG. 3  with respect to the movable base member  14  about the common central point C 2  as the pivot center. Hence, the first, second and fourth guided portions  121 ,  122  and  131  of the shield  4  are further guided by the second, third and fourth guide portions  56 ,  62  and  66  of the movable base member  14 , respectively. At the same time, the third guided portion  123  of the shield  4  is also further guided by the click tooth portion  37  of the stationary base member  13 . Hence, the first to fourth guided portions  121  to  123  and  131  of the shield  4  pivot forward clockwise in  FIG. 3  about the common central point C 2  as the pivot center. As a result, the pair of tooth portions  132  and  133  of the third guided portion  123  engages with the recess immediately above the lowermost recess and the lowermost recess of the click tooth portion  37 , respectively, as shown in  FIG. 4 . In other words, the tooth portion immediately above the lowermost tooth portion of the click tooth portion  37  engages with the recess between the pair of tooth portions  132  and  133  of the third guided portion  123 . For this reason, the shield  4  is accurately held in the stage-2 open state shown in  FIG. 4 . 
     (4) Fully-Open State 
     In the stage-2 open state shown in  FIG. 4 , when further pulling up the shield  4  largely, it is set in the fully-open state (that is, maximal open state) shown in  FIG. 5 . Note that when shifting to the fully-open state, the shield  4  further pivots forward largely clockwise in  FIG. 4  with respect to the movable base member  14  about the common central point C 2  as the pivot center. The fully-open state shown in  FIG. 5  is substantially the same as the state immediately after attaching the shield  4  to the head protecting body  2 , which has been explained in the above item 2(6) concerning the operation described in item (e), and a detailed description thereof will be omitted. Note that in the fully-open state shown in  FIG. 5 , the third guided portion  123  of the shield  4  passes the click tooth portion  37  of the stationary base member  13  and is located above the click tooth portion  37 . Hence, the common central point C 2  as the pivot center of the shield  4  and anti-fogging auxiliary shield attached as needed is held at a position which is retracted to the most rear side between the stage-1 open state and the fully-open state. In the fully-open state, one of the stopper engaging recesses  104   a  to  104   e  of the pivotal manipulation button  17  attached to the movable base member  14  abuts against the stopper portion  42  of the stationary base member  13 , thereby holding the position of the movable base member  14 . When the shield  4  is pulled up from the stage-1 open state to the fully-open state, as described above, the shield  4  and anti-fogging auxiliary shield attached as needed can be prevented from projecting forward more than necessary from the head protecting body  2 . It is therefore possible to prevent to some extent the shield  4  from flapping in wind during driving. Note that the position holding are done in the same way even in the fully-closed state described in the above item (1). 
     (5) Removable State 
     In the fully-open state shown in  FIG. 5 , when the shield attaching/removing manipulation lever  16  is pivoted forward clockwise in  FIG. 5  about the pivot axis portion  81  as the fulcrum against the elastic biasing force of the repulsive coil spring  75 , the shield  4  is set in the removable state shown in  FIG. 6 . Note that the removable state is substantially the same as the removable state at the time of a forward pivot operation of the shield attaching/removing manipulation lever  16  explained in the above item 2(6) concerning the operation described in item (e), and a detailed description thereof will be omitted. In the removable state shown in  FIG. 6 , by performing operation opposite to that explained in the above item 2(6) concerning the operation described in item (e), the left end of the shield  4  can be easily removed from the movable base member  14 . 
     In the removable state shown in  FIG. 6 , as described in the above item (4), one of the stopper engaging recesses  104   a  to  104   e  of the pivotal manipulation button  17  attached to the movable base member  14  abuts against the stopper portion  42  of the stationary base member  13 . For this reason, the movable base member  14  completely moves backward with respect to the stationary base member  13 . Hence, during a period between a timing before the shield  4  is removed from the movable base member  14  and a timing after the removal, the elastic biasing forces of the repulsive coil springs  31   a  and  31   b  will not further move the movable base member  14  backward with respect to the stationary base member  13 . This also applies during a period between a timing before the shield  4  is attached to the movable base member  14  and a timing after the attachment. Therefore, the shield  4  can be attached to and removed from the movable base member  14  easily and reliably. 
     (6) State during Adjustment 
     The position of the shield  4  with respect to the window opening rim member  8  substantially in the back-and-forth direction, in the fully-closed state shown in  FIGS. 1, 2 and 8 , can be adjusted by manipulating the pivotal manipulation button  17 . Note that when performing this adjustment, the shield  4  needs to be set in one of the stage-2 open state and the stage-3 and subsequent open states except the fully-open state (that is, one of the stage-2 to stage-6 open states) in advance such that the helmet wearer or the like can manipulate the pivotal manipulation button  17 . For example, the adjustment operation in the stage-2 open state shown in  FIG. 7  will be described. The stopper portion  42  of the stationary base member  13  is separated from all of the stopper engaging recesses  104   a  to  104   e  of the pivotal manipulation button  17 . Hence, when a screwdriver (not shown) or the like is engaged with the groove  101  of the pivotal manipulation button  17  and then pivoted, the positioning projection  114  changes its engaging state from one of the plurality of positioning recesses  103  to another. Note that the separate state also occurs in the stage-1 to stage-6 open states except the fully-closed state and the fully-open state. 
     (7) State after Adjustment 
     When the shield  4  is changed from the state during adjustment described in the above item (6) to the fully-closed state, the stopper portion  42  of the stationary base member  13  changes the engaging target from one of the stopper engaging recesses  104   a  to  104   e , which engaged before the adjustment, to another. In this case, as for the positions of the stopper engaging recesses  104   a  to  104   e , the distance from the pivot center C 3  of the pivotal manipulation button  17  sequentially decreases by, for example, 0.25 mm. For this reason, the position of the pivotal manipulation button  17  (accordingly the movable base member  14 ) with respect to the stationary base member  13  substantially in the back-and-forth direction in the fully-closed state moves substantially forward or substantially backward by 0.25X mm (X is the number representing how far one of the stopper engaging recesses  104   a  to  104   e , which engages after adjustment, is apart from another of the stopper engaging recesses  104   a  to  104   e , which engaged before adjustment). Hence, with the above adjustment, the position of the shield  4  with respect to the head protecting body  2  substantially in the back-and-forth direction in the fully-closed state can be adjusted to a desired position within the range of 0.25X mm. 
     Having described a specific preferred embodiment of the present invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment, 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 above-described embodiment, the present invention is applied to the full-face-type helmet  1 . However, the present invention can also be applied to a full-face-type helmet serving also as a jet-type helmet in which the chin cover can move upward, a jet-type helmet, a semi-jet-type helmet, and the like. 
     In the above-described embodiment, the shield position adjustment operation member is formed from the shield position adjustment pivotal manipulation member  17 . However, the shield position adjustment operation member  17  need not always be of a pivotal manipulation type. Various members such as a member to be manipulated substantially linearly forward and backward and a member to be manipulated forward and backward along an arbitrary curve may be used. 
     In the above-described embodiment, a stopper means having a single position holding portion (more specifically, stopper portion  42 ) that can comprise a plurality of position holding portions is provided on the stationary base member  13 . In addition, a stopped means having a plurality of position holding portions (more specifically, stopper engaging recesses  104   a  to  104   e ) is provided on the movable base member  14 . However, a stopped means having a single position holding portion that can comprise a plurality of position holding portions may be provided on the movable base member  14 , and a stopper means having a plurality of position holding portions may be provided on the stationary base member  13 . In this case as well, the stopper means  104   a  to  104   e  and the plurality of positioning recesses  103  can be provided on a common member such as the pivotal manipulation button  17 . 
     The above-described embodiment employs the repulsive coil springs  31   a ,  31   b  and  75  as elastic biasing means or elastic biasing members. Alternatively, of the three elastic biasing means  31   a ,  31   b  and  75 , one, two, or all three may comprise tension coil springs, or springs other than coil springs, for example, leaf springs. 
     In the above-described embodiment, the shield attaching/removing manipulation member  16  is formed from a manipulation lever capable of pivoting forward and backward. Alternatively, the manipulation member  16  can be formed from a member capable of linearly moving forward and backward, or a member capable of forward and backward movement other than forward and backward pivot or linear forward and backward movement.