Mechanism for attaching a rotating plate in a helmet

Abstract: In accordance with one aspect of this invention, in a mechanism (9) for attaching a rotating plate in a helmet, a positioning member (23) which is of substantially tubular shape and relatively slidable along a guide groove (47) provided in the rotating plate such as a shield plate (5) and shaped into a nearly circular arc, has an easily bendable portion (38) provided between a first cut (35) and a second cut (37) which are formed in substantially opposed relation to each other at the upper end and the lower end of the positioning member (23), respectively. In accordance with another aspect of this invention, in a mechanism for attaching a rotating plate in a helmet, the three engaged openings (47a,47b,47c) provided in the guide groove (47) so as to keep in the fully closed condition, in the fully opened condition, and in the defrosted condition, respectively, can relatively hold the positioning member (23) to almost remain its original form, and the arcuated groove (47d) disposed in the guide groove (47) can relatively hold the positioning member (23) so as to deform it elastically.

Description: Technical Field The present invention relates to a helmet having a head protector for protecting the head of a person with a helmet on, such as a rider on a motor-bicycle, and particularly to a mechanism for attaching a rotating plate, such as a shield plate or a visor available for a windshield and/or a sunshade, to the head protector so as to be rotatable within a predetermined angular range. Background of the Invention Such a mechanism for attaching the rotating plate as described above is disclosed, for example, in Japanese Utility Model Registration Publication No. 57-13302. The mechanism for attaching the rotating plate to the head protector in the helmet, disclosed in Japanese Utility Model Registration Publication No. 57-13302 (hereinafter described as "the conventional mechanism for attaching the shield plate") has a narrow base plate attached to the front side of the head protector of the helmet. Rotatably attached to this base plate are the right and left sides of a shield plate with a pair of right and left attaching shafts, respectively. Further, an intermediate plate lies between the base plate and the shield plate, and a protrusion projecting from the outer side surface of the intermediate plate and serving as a stopper is fitted into an opening of the shield plate, so that the intermediate plate is rotatable together with the shield plate. Moreover, in the conventional mechanism for attaching the shield plate, a circular-arcuate guide groove whose center coincides with that of the attaching shaft is disposed in the base plate, and fitted into this guide groove is a resilient cylinder, projecting from and formed integral with the inner side of the intermediate plate. The circular-arcuate guide groove is shaped from a plurality of circular openings which are shifted a little in turn and partially overlapped, so that a narrow part is formed between the adjacent openings. In the conventional mechanism for attaching the shield plate constituted as described above, when the shield plate is moved to open or close the head protector, the resilient cylinder is moved along the circular-arcuate guide groove and fitted into one of the plurality of circular openings, so that it is possible to set the shield plate in its predetermined position that shows a one-to-one correspondence with each of the plurality of circular openings (that is, fully closed position, one-sixth opened position, one-third opened position, half-opened position, two-thirds-opened position, five-sixths opened position, or fully opened position). However, in the conventional mechanism for attaching the shield plate, the shield plate can be merely set in its predetermined position that corresponds with one of the plurality of circular openings of the circular-arcuated guide groove, so that the shield plate cannot be set in an arbitrarily opened position with respect to the head protector of the helmet. Further, when the shield plate is largely moved to open or close with respect to the head protector of the helmet, it is required to move the resilient cylinder wobblingly along the plurality of circular openings and the plurality of narrow parts, so that well clicking responses are not brought when the shield plate is thus moved. Such a circular-arcuate guide groove as mentioned above is described also in BP-A-0 292 677, EP-A-0 420 300, and JP-A-0 607 36 05. These three prior art documents also involve the same defects as those described above with respect to the above-described conventional mechanism for attaching the shield plate. Further, in each of the above-described Japanese Utility Model Registration No. 57-13302 and JP-A-0 607 36 05, the positioning member made of the resilient cylinder is a circular cylinder which is uniform in thickness and is uniform along a circumferential direction in length of axial direction. Therefore, it is required for the positioning member as a whole to be relatively deformable in order that the positioning member can move smoothly without a hitch in the circular-arcuate guide groove. By this reason, when a great shock is applied onto a helmet, there is much fear that the positioning member unnecessarily moves in the circular-arcuate guide groove. Also, in each of EP-A-0 294 677 and EP-A-0 420 300, the positioning member is formed of a semi-cylindrical portion which is easily deformable. Therefore, in the case of these two prior art documents, when a helmet is worn for a long time, the semi-cylindrical portion deteriorates its elastic property and cannot perform a preferred elastic deformation. As a result, it becomes impossible to surely position the positioning member relatively in the predetermined position within the circular-arcuate guide groove. Summary of the Invention Accordingly, it is an object of the present invention to provide a mechanism for attaching a rotating plate in a helmet, in which the operation of the positioning member sliding relatively along the guide groove is made sure enough, though its constitution is very simple. Another object of the present invention is to provide a mechanism for attaching a rotating plate in a helmet, in which the rotating plate can be set sure enough in its fully closed position, its defrosted position, and its fully opened position, and also can be set in arbitrarily opened positions intermediate between the defrosted position and the fully opened position. A further object of the present invention is to provide a mechanism for attaching a rotating plate in a helmet, in which the opening and the closing operations of the rotating plate from its defrosted position to its fully opened position and from its fully opened position to its defrosted position can be carried out very smoothly, and the clicking response is very well at the time of opening and closing the rotating plate. In accordance with the present invention, a mechanism for attaching a rotating plate in a helmet, comprising a rotating plate available for a windshield and/or a sunshade, which is attached to a head protector so as to be rotable about a predetermined pivot; an arcuated guide groove provided in the rotating plate, which is of nearly circular arc, the center of a circle partially marked out by the circular arc substantially coinciding with that of the predetermined pivot; and a substantially tubular positioning member attached to the head protector and inserted into the guide groove so as to be relatively slidable along the guide groove when the rotating plate is rotated, wherein the axis of the substantially tubular positioning member extends substantially perpendicularly to the rotating plate, is characterized in that a first cut and a second cut are formed in substantially opposed relation to each other at one end and the other end of the positioning member in its axial direction, respectively, to provide an easily bendable portion between the first cut and the second cut of the positioning member. According to the present invention made as described above, the substantially tubular positioning member relatively slidable along the guide groove, which is provided in the rotating plate and shaped into the nearly circular arc, has the easily bendable portion between the first cut and the second cut which are formed in substantially opposed relation to each other at one end and the other end of the substantially tubular positioning member in its axial direction, respectively, so that the operation of the substantially tubular positioning member, which slides relatively along the guide groove shaped into the nearly circular arc, can be carried out very simply and very surely. Further, in the mechanism comprising the rotating plate rotatably attached to the head protector, the guide groove provided in the rotating plate and shaped into the nearly circular arc, and the substantially tubular positioning member attached to the head protector and relatively sliding along the guide groove, which is shaped into the nearly circular arc, the easily bendable portion is provided between the first cut and the second cut which are formed in substantially opposed relation to each other at one end and the other end of the substantially tubular positioning member in its axial direction, respectively, so that the constitution of the mechanism is very simple. In accordance with another aspect of the present invention, a mechanism for attaching a rotating plate in a helmet, as described before is characterized in that the guide groove has a first engaged opening for keeping in the fully closed condition, which is provided at one end of the guide groove, a second engaged opening for keeping in the fully opened condition, which is provided at the other end of the guide groove, a third engaged opening for keeping in the defrosted condition, which is provided to be near to and partially overlap with the first engaged opening, and an arcuated groove, which is of substantially circular arc and is substantially uniform in width and by means of which the second engaged opening and the third engaged opening communicate with each other, the center of a circle partially marked out by the circular arc substantially coinciding with that of the predetermined pivot; the substantially tubular positioning member is held by the three engaged opening so as to almost remain its original form when it is fitted into each engaged openings and the substantially tubular positioning member is elastically deformed by the arcuated groove when it is fitted into the arcuated groove. According to the present invention made as described above, the substantially tubular positioning member can be held so as to almost remain it original form when fitted into the engaged openings for keeping in the fully closed condition, in the defrosted condition and in the fully opened condition, respectively, and can be elastically deformed in the guide groove, which has been shaped into the substantially circular arc, so that the rotating plate can be set sure enough in its fully closed position, its defrosted position, and its fully opened position, respectively, and also can be set in arbitrarily opened positions intermediate between the defrosted position and the fully opened position. Further, the opening and the closing operations of the rotating plate from its defrosted position to its fully opened position and from its fully opened position to its defrosted position can be carried out very smoothly, and the clicking response is very well at the time of opening and closing the rotating plate. 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 Figure 1 is a general perspective view of a helmet according to a first embodiment, in which the present invention is applied to a shield plate attaching mechanism of a full-face-type helmet; Figure 2 is an exploded, perspective view of the shield plate attaching mechanism on the left side of the helmet of Figure 1; Figure 3 is a front view of the shield plate attaching mechanism of Figure 2, illustrating the state of the shield plate opened a little at the defrosted position; Figure 4 is a front view, similar to Figure 3, of the principal part of the shield plate attaching mechanism of Figure 3, illustrating the state of the shield plate further opened at a position intermediate between the defrosted position and the fully opened position; Figure 5 is a front view similar to Figure 4, illustrating the fully opened state of the shield plate; Figure 6 is a front view similar to Figure 4, illustrating the fully closed state of the shield, plate; Figure 7 is a sectional view taken along the line A-A on Figure 3; Figure 8 is a sectional view of the shield plate attaching mechanism taken along the line A-A on the dot-dash line portion of Figure 3; Figure 9 is a sectional view taken along the line B-B on Figure 4; Figure 10 is a sectional view taken along the line C-C on Figure 6; and Figure 11 is a front view, similar to Figure 3, of a shield plate attaching mechanism according to a second embodiment, in which the present invention is applied to a shield plate attaching mechanism of a full-face-type helmet. Detailed Description of the Invention Referring to Figures 1-10, a first embodiment in which the present invention is applied to a shield plate attaching mechanism of a full-face-type helmet will be described hereinafter. As shown in Figure 1, the full-face-type helmet comprises a cap-like head protector 1 worn by a rider of a motorcycle or the like, a shield plate 5 capable of opening and closing a window opening 3 formed on the front side of the head protector 1 so as to face a portion lying between the fore head and the chin of the rider or the like with the helmet on (that is, the central portion of the face), and a pair of right and left chin straps (not shown) attached to the inner side of the head protector 1. A ventilator 6 for ventilating the inside of the head protector 1 is disposed in a portion of the head protector 1, facing the chin of the rider or the like with the helmet on. The shield plate 5 is attached to the helmet so as to be available for a windshield but, if necessary, it may be colored so as not to cut out light and used also as a sunshade (that is, a visor). The shield plate 5 may be made of transparent or translucent hard material such as polycarbonate or other hard resins. The right side and the left side of the shield plate 5 are rotatably attached to an outer shell 7, which forms the outer wall of the head protector 1, through a pair of right and left shield plate attaching mechanism 9. It is noted that the outer shell 7 may be made of high strength hard material such as FRP or other hard resins. The right shield plate attaching mechanism ("right" will be designated as "left" when the helmet is viewed from its front side) is fully symmetrical to the left shield plate attaching mechanism, except that a finger held portion 11, a female-screw member 12 (including a fitting opening provided in the outer shell 7), an engaging pin 13, an engaged aperture 15 and a guiding notch 17, which are described hereinafter, are not disposed in the right shield plate attaching mechanism, so that the explanation of the right shield plate attaching mechanism is omitted and only the explanation of the left shield plate attaching mechanism will be given. As shown in Figures 2 and 9, the left shield plate attaching mechanism 9 has an attaching member 19 which is attached to the outer shell 7 together with the shield plate 5. The attaching member 19 comprises a substantially annular base portion 21, a substantially cylindrical portion 23, which serves as the substantially tubular positioning member, a narrow strip-like connecting portion 25, which connects the base portion 21 with the cylindrical portion 23, and a pair of right and left reinforcing portions 27 that extend from the cylindrical portion 23 to the connecting portion 25 and laterally spread like gills on the right and left sides of their boundary and its vicinity. It is noted that the portions denoted by numerals 21, 23, 25 and 27 are made of a little elastic material such as polyacetal resin or other resins, and are formed integrally with one another. Provided in the surface of the base portion 21 are a pair of right and left engaging grooves 31 each having a bottom, which are arranged in opposed relation to each other and are connected to a central aperture 29 and, in the back surface of the base portion 21, many radial ridges (not shown) for preventing slips are formed integrally with the base portion 21. Provided at the upper end of the cylindrical portion 23 are a pair of right and left engaging slits 33 which are relatively narrow in width and, between the pair of engaging slits 33, a substantially rectangular cut 35 for causing resilience lies, which is relatively wide in width. Further, provided at the lower end of the cylindrical portion 23 is a substantially rectangular cut 37 for causing resilience, which lies in opposed relation to the cut 35 along the axial direction of the cylindrical portion 23, and is relatively wide in width. Thus, an easily bendable portion 38 is formed between the cuts 35 and 37. The easily bendable portion 38 is a little narrow in width and elastically deformable. Each of the upper cut 35 and the lower cut 37 is not necessarily of substantially rectangular shape and may be in the shape of the substantial letter U, a substantially half elongated-circle, a substantially half ellipse, a substantially half circle, or the like. Further, many radial ridges (not shown) for preventing slips are integrally formed in the back surface of the reinforcing portion 25 and a part of the cylindrical portion 23 corresponding to the reinforcing portion 25. The upper cut 35 and the lower cut 37 serve for giving good elasticity to the cylindrical portion 23 (particularly, the far end of the cylindrical portion 23 when viewed from the side nearer to the base portion 21, in other words, one side opposite to another side nearer to the rotating center of the shield plate 5). As shown in Figure 2, both the cuts 35, 37 are provided at the far end of the cylindrical portion 23. In the embodiment shown in Figure 5, the cut 35, 37 is provided in the cylindrical portion 23 at an angle  1 of about 90°, the angle  1 being formed by two radii of the cylindrical portion 23, passing through the respective ends of the cut 35, 37. The angle  1 is generally preferable to be within the range of 60°-120° and much preferable to be within the range of 70°-110°, so that the action of the attaching member 19 may be performed smoothly. As shown in Figure 5, it is preferable that the two angles, into which the angle  1 is divided by straight line L, which passes through the center of the base portion 21 and the center of the cylindrical portion 23, are substantially the same. In the embodiment, the right and the left angles, into which the angle  1 is divided, are each about 45°. Further, in the embodiment, the depth D 1 of the upper cut 35 is about 1/8 of the height H of the cylindrical portion 23 (that is, the vertically measured length in Figure 10) as shown in Figure 10. The depth D 1 is generally preferable to be within the range of 1/12 - 1/4 of the height H and much preferable to be within the range of 1/10 - 1/6 of the height H, so that the action of the attaching member 19 may be smoothly performed. In the embodiment, the depth D 2 of the lower cut 37 is about 3/8 of the height H as shown in Figure 10. The depth D 2 is generally preferable to be within the range of 1/4 -3/4 of the height H and much preferable to be within the range of 3/10 - 1/2 of the height H, so that the action of the attaching member 19 may be smoothly performed. Further, in the embodiment, the total (D 1 +D 2 ) of the depth D 1 of the upper cut 35 and the depth D 2 of the lower cut 37 is about 1/2 of the height H. The total (D 1 +D 2 ) is generally preferable to be within the range of 1/3 - 4/5 of the height H and much preferable to be within the range of 2/5 - 2/3, so that the action of the attaching member 19 may be smoothly performed. As shown in Figure 9, a pair of engaged apertures are provided in the outer shell 7 so as to correspond to both the base portion 21 and the cylindrical portion 23 of the attaching member 19, and a pair of female screw members 41, 42 made of hard material such as mild steel or the like are fitted into and fixed to the pair of engaged apertures, respectively. A pair of washers 44, 45 made of elastic material such as synthetic elastomer or the like are fixed, with an adhesive or the like, to the outer surface of the outer shell 7 so as to be capable of surrounding the respective female screw members (41, 42). As shown in Figure 7, another engaged aperture is provided in the outer shell 7 and, into this engaged aperture, another female-screw member 12 is fitted. An engaging pin 13 made of hard material such as aluminum or other metal is fitted into and fixed to the female-screw member 12. As shown in Figure 2, the shield plate 5 has a substantially circular attaching opening 39 corresponding to the base portion 21 of the attaching member 19; an arcuated guide groove 47 shaped into a nearly circular arc, whose center substantially coincides with that of the fitting opening 39, and corresponding thereby to the cylindrical portion 23 of the attaching member 19; an engaged aperture 15 shaped into a substantially elongated-circle and corresponding to the engaging pin 13 provided in the outer shell 7; and a guiding notch 17 disposed on the inside of the shield plate 5 so as to be adjacent to the engaged aperture 15. As shown in Figure 7, an engaging member 49 for engaging a tear-off shield film (that is, an expendable shield film, not shown), which is made of synthetic resin or the like, is secured and fixed to the shield plate 5 with a screw 51 and, also, a finger held portion 11 made of synthetic resin or the like is secured and fixed to the shield plate 5 with a screw (not shown). The finger held portion 11 is used when the person with the helmet on pushes up the shield plate 5 with his finger to move the shield plate 5. As shown in Figure 4, the arcuated guide groove 47 has an engaged opening 47a for keeping in the fully closed condition, and an engaged opening 47b for keeping in the fully opened condition at both the ends thereof, respectively, and also has an engaged opening 47c for keeping in the defrosted condition, which is provided to partially overlap and communicate with the engaged opening 47a. Further, an arcuated groove 47d shaped into a substantially circular arc form and being substantially uniform in width is provided between the engaged opening 47c for keeping in the defrosted condition and the engaged opening 47b for keeping the full opened condition, and the inner side edge of the arcuated guide groove 47 (that is, the edge nearer to the attaching opening 39) comprises a substantially smooth curve 62 (shaped into a substantially circular arc form), which extends from the engaged opening 47a to the engaged opening 47b. As shown in Figure 2, the outer side edge of the arcuated guide groove 47 (that is, the edge far from the attaching opening 39) has one pointed protrusion 53 forming the boundary between the engaged openings 47a and 47c, the other pointed protrusion 54 forming the boundary between the engaged opening 47c and the arcuated groove 47d, and a further pointed protrusion 55 forming the boundary between the arcuated groove 47d and the engaged opening 47b, and only the outer edge of the arcuated groove 47d makes a substantially smooth curve 63 (shaped into a substantially circular arc form as shown in Figure 2). In the embodiment shown in Figure 4, the angle  2 of between the center of the first engaged opening 47a and the center of the second engaged opening 47b, formed by an angular spread at the predetermined pivot is about 45°. The angle  2 is generally preferable to be within the range of 30°-60° and it is much preferable to be within the range of 35°-55°, so that the action of the attaching member 19 may be smoothly performed. Further, in the embodiment shown in Figure 4, the angle  3 of between the center of the first engaged opening 47a and the center of the third engaged opening 47c, formed by an angular spread at the predetermined pivot is about 10°. The angle  3 is generally preferable to be within the range of 6°-15° and it is much preferable to be within the range of 8°-13°, so that the shield plate 5 may be kept well in the defrosting position. In the embodiment shown in Figure 4, the ratio of angle  3 to angle  2 (that is,  3 / 2 ) is 2/9. The ratio is generally preferable to be within the range of 1/9 - 4/9 and the ratio is much preferable to be within the range of 3/18 - 3/9, so that the action of the attaching member 19 may be smoothly performed and the shield plate 5 may be kept well in the defrosting position. In the embodiment shown in Figure 6, the angle  4 of the arcuated groove 47d, formed by an angular spread at the predetermined pivot (in other words, formed by two radii of the attaching opening 39, passing through the pair of pointed protrusions 54, 55) is about 23°. The angle  4 is generally preferable to be within the range of 15°-35° and the angle  4 is much preferable to be within the range of 18°-30°, so that the action of the attaching member 19 may be smoothly performed and the shield plate 5 may be kept well in the defrosting position. The ratio of the width of the arcuated groove 47d to each diameter of the engaged opening 47a, 47b, 47c (it is nearly equal to the ratio of the width of the arcuated groove 47d to the diameter of the cylindrical portion 23 of the attaching member 19) is about 93/100. The ratio is generally preferable to be within the range of 80/100 - 97/100 and the ratio is much preferable to be within the range of 85/100 - 95/100, so that the action of the attaching member 19 may be smoothly performed. In the embodiment, the engaged opening 47a, 47b, 47c is of substantially circular shape and nearly equal to or a little larger than that of the cylindrical portion 23 of the attaching member 19. However, the form of the engaged opening 47a, 47b, 47c is not necessarily of substantially circular shape. The form may be of substantially elongated circular shape, substantially elliptical shape, substantially rectangular shape with cut-off corners, or the like as the cylindrical portion 23 is so. Particularly, it is preferable that the form of the engaged opening 47a, 47b, 47c varies in accordance with that of the cylindrical portion 23. There will be described hereinafter how to attach the shield plate 5 and the attaching member 19 to the outer shell 7. It is noted that a pair of screws 57, 58 and a pair of washers 60, 61 are used when the shield plate 5 and the attaching member 19 are attached. The screw 57, 58 and washer 60 may be made of synthetic resin such as polycarbonate resin or polyacetal resin, or metal such as aluminum or other metal, and the washer 61 is also made of synthetic resin such as polycarbonate resin, polyacetal resin or the like. Firstly, the tip of the screw 57 used as a supporting shaft is inserted, in turn, into the central aperture 64 of the washer 60, the attaching opening 39 of the shield plate 5, and the central aperture 29 of the base portion 21 of the attaching member 19, and screwed into the female screw member 41 until the screw 57 is fixed (see Figure 10). In that event, the upper end of the cylindrical portion 23 of the attaching member 19 is inserted into the arcuated guide groove 47 of the shield plate 5, and a pair of protrusion 60a projecting from the lower surface of the washer 60 is fitted into the pair of engaging grooves 31 of the base portion 21. Thus, the washer 60 and the base portion 21 of the attaching member 19 are pressed against the washer 44 of the outer shell 7 by the head of the screw 57 until they are fixed as shown in Figure 10, and the shield plate 5 is rotatably supported by the washer 60 (that is, the central axis of the washer 60 serves as the axis of rotation) between the surface of the base portion 21 of the attaching member 19 and the head portion of the washer 60. Secondly, the tip of the screw 58 used as a fixed axis is inserted, in turn, into the central aperture 65 of the washer 61 and the central aperture 66 of the cylindrical portion 23 of the attaching member 19 (fitted into the arcuated guide groove 47 of the shield plate 5), and the screw 58 is screwed into the female screw member 42 of the outer shell 7 until the screw 58 is fixed as shown in Figure 10. In that event, a pair of protrusions 61a projecting from the lower surface of the washer 61 are fitted into the pair of engaging slits 33 of the cylindrical portion 23. Thus, the washer 61 and the cylindrical portion 23 of the attaching member 19 are pressed against the washer 45 of the outer shell 7 by the head of the screw 58 until they are fixed as shown in Figure 10. In that event, the shield plate 5 is kept holding between the surface of the connecting portion 25 and the washer 61 so as to slide the outer periphery of the cylindrical portion 23 along the inner and outer side edges of the arcuated guide groove 47 whenever the shield plate 5 is moved and, in that state, the easily bendable portion 38 provided in the cylindrical portion 23 of the attaching member 19 is positioned at the distal end side of the attaching member 19. In the full-face-type helmet constituted as described above, if the shield plate 5 undergoes rotary motion on the central axes of the screw 57 and the washer 60 and the cylindrical portion 23 of the attaching member 19 relatively slides along the arcuated guide groove 47 of the shield plate 5, it becomes possible as described hereinafter to keep the shield plate 5 holding in its fully closed position, its defrosted position (that is, its blur preventing position, its blur removing position, its frost preventing position and/or its frost removing position), its arbitrarily opened position, and its fully opened position. It is to be noted in the above description that "the fully closed position" of the shield plate 5 does not necessarily mean that the window opening 3 is completely closed by the shield plate 5. It may be sufficient if the window opening 3 is practically closed. Further, it is to be noted that "the fully opened position" of the shield plate 5 does not necessarily mean that the window opening 3 is completely opened by the shield plate 5. It may be sufficient if the window opening 3 is practically opened. That is, when the cylindrical portion 23 is kept holding in the engaged opening 47a of the guide groove 47 to almost remain its original form as shown in Figures 6 and 10, the shield plate 5 is in its fully closed position. In that event, the engaging pin 13 of the outer shell 7 is fitted into the engaged aperture 15 of the shield plate 5 as indicated by dot-dash lines in Figure 3, so that the shield plate 5 can be held surely in its fully closed position. Since the guiding notch 17 disposed in the inner side surface of the shield plate 5 is slanted upward from the lower end of the shield plate 5 so that the depth of the guiding notch 17 may become gradually shallow as shown in Figure 7, the engaging pin 13 to be relatively moved on the notch 17 can be fitted easily and surely into the engaged aperture 15. In the fully closed state (indicated by dot-dash lines in Figures 1 and 3, and shown in Figures 8 and 10), when the person with the helmet on presses the finger held portion 11 of the shield plate 5 with his finger to rotate the shield plate 5 obliquely upward as indicated by continuous line in Figure 3 and shown in Figure 7, the engaging pin 13 relatively comes out of the engaged aperture 15, and the cylindrical portion 23 is fitted into the engaged opening 47c, so that the shield plate 5 lies in its defrosted position, where the window opening 3 of the head protector 1 is opened a little. When the shield plate 5 is further rotated, the cylindrical portion 23 fitted into the arcuated guide groove 47 relatively moves from engaged opening 47c to engaged opening 47b through the arcuated groove 47d. When the cylindrical portion 23 relatively passes through the protrusions 53, 54 and the arcuated groove 47d, in which the width is comparatively narrow, the diameter of the cylindrical portion 23 decreases in the direction of line L shown in Figure 5, so that the cylindrical portion 23 can pass through the above narrow width portions. In that event, the upper surface of the cylindrical portion 23 partially lacking for the upper cut 35 is pressed against the washer 61, and the lower surface of the cylindrical portion 23 partially lacking for the lower cut 37 is pressed against the washer 45. Further, the lower end of the cylindrical portion 23 is connected to the pair of reinforcing portions 27 and the connecting portion 25 on the side nearer to the fitting opening 39, whereby the side nearer to the fitting opening 39 is rigid enough. Accordingly, the above-described contraction, in diameter, of the cylindrical portion 23 mainly depends upon the bending deformation of the easily bendable portion 38. In addition, when the cylindrical portion 23 relatively passes through the arcuated groove 47d, the cylindrical portion 23 is smoothly moved without any uneasiness, because the arcuated groove 47d is shaped into a substantially circular arc. Thus, the shield plate 5 can be opened and closed with dulcet clicks. When the cylindrical portion 23 is set in an arbitrary position of the arcuated groove 47d, the cylindrical portion 23 can be kept holding there in a comparatively good condition, because the cylindrical portion 23 is elastically sandwiched due to its resilience (particularly, the resilience of the easily bendable portion 38). Thus, the shield plate 5 can be kept not only holding surely in its defrosted position, where the window opening 3 of the head protector 1 is opened a little, and its practically fully opened position, but also holding almost surely in an arbitrarily opened position that is intermediate between the defrosted position and the practically fully opened position. Referring to Figure 11, a second embodiment in which the present invention is applied to a shield plate attaching mechanism of a full-face-type helmet will be described hereinafter. In the shield plate attaching mechanism according to the second embodiment of the present invention, the constitution thereof is practically the same as the one according to the first embodiment shown in Figures 1-10, excepting the form of a nearly circular guide groove 47, so that the above-described explanation of the shield plate attaching mechanism shown in Figures 1-10 can be also applied to the explanation of the shield plate attaching mechanism shown in Figure 11, excepting an explanation described hereinafter in connection with the above different point. Further, in both the first and the second embodiments, the same numbers will be used to identify the members if there are common members between them, and their explanation will be omitted. In the shield plate attaching mechanism 9 according to the second embodiment, the shield plate 5 is kept not surely holding in a specific defrosted position, so that, in the second embodiment, no engaged opening 47c for keeping in the defrosted condition is provided in the arcuated guide groove 47. In other words, the arcuated guide groove 47 shaped into a nearly circular arc has the engaged opening 47a for keeping in the fully closed condition at one end thereof, and the engaged opening 47b for keeping in the fully opened condition at the other end and, between both the engaged openings 47a and 47b, an arcuated groove 47d shaped into a substantially circular arc and having a substantially uniform width is formed. The outer side edge of the arcuated guide groove 47 shaped into the nearly circular arc comprises a substantially smooth curve 63 (that is, a nearly circular arc) extending from the pointed protrusion 53 to the pointed protrusion 55. In the embodiment shown in Figure 11, the angle  5 of the arcuated groove 47d, formed by an angular spread at the predetermined pivot is about 30°. The angle  5 is generally preferable to be within the range of 20°-45° and it is much preferable to be within the range of 24°-40°, so that the action of the attaching member 19 may be smoothly performed. Thus, in the shield plate attaching mechanism 9 shown in Figure 11, the shield plate 5 can be surely kept holding in the fully closed position where the window opening 3 of the head protector 1 is practically fully closed and in the fully opened position where the window opening 3 is practically fully opened, like the shield plate attaching mechanism shown in Figures 1-10. Further, the shield plate 5 can be almost surely kept holding in an arbitrarily opened position (including the defrosted position), which lies between the fully closed position and the fully opened position. It is noted that how to set the shield plate 5 in its arbitrarily opened position will be easily understood by the explanation referring to Figure 4 in the first embodiment. In the shield plate attaching mechanism 9 shown in Figure 11, the defrosted position of the shield plate 5 is not specified but can be adjustably selected, so that the person with the helmet on can select very easily an arbitrarily defrosted position so as to fit the weather or other conditions. Having described specific preferred embodiments of the present invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to that precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims. For example, in the above embodiments, the present invention is applied to the shield plate attaching mechanism of the full-face-type helmet, but the present invention is also applied to a jet-type helmet, a semi-jet-type helmet or the like. Further, the present invention is applied to a mechanism for attaching a visor, too. In the above embodiments, the single easily bendable portion 38 is formed between the upper cut 35 and the lower cut 37, but a plurality of easily bendable portions may be provided by means of disposing laterally longer one or plural slits between those cuts 35 and 37. It is noted that the slits disposed between the cuts 35, 37 of the easily bendable portion 38 nearly correspond to each other in upper side and lower side relations. Further, in lieu of, or in addition to the above slit, a plurality of small apertures may be formed in the easily bendable portion.

Claims: A mechanism for attaching a rotating plate in a helmet comprising: a rotating plate (5) available for a windshield and/or a sunshade, which is attached to a head protector (1) so as to be rotable about a predetermined pivot; an arcuated guide groove (47) provided in the rotating plate (5), which is of nearly circular arc, the center of a circle partially marked out by the circular arc substantially coinciding with that of the predetermined pivot; and a substantially tubular positioning member (23) attached to the head protector (1) and inserted into the guide groove (47) so as to be relatively slidable along the guide groove (47) when the rotating plate (5) is rotated, wherein the axis of the substantially tubular positioning member (23) extends substantially perpendicularly to the rotating plate (5), characterized in that : a first cut (35) and a second cut (37) are formed in substantially opposed relation to each other at one end and the other end of the positioning member (23) in its axial direction, respectively, to provide an easily bendable portion (38) between the first cut (35) and the second cut (37) of the positioning member (23), so that the rotating plate (5) can be set sure enough in different arbitrarily opened positions within said arcuated guide groove (47). A mechanism for attaching a rotating plate in a helmet according to Claim 1, characterized in that : an attaching member (19) is disposed for locating the positioning member (23); the attaching member (19) has a base portion (21), the positioning member (23), and a connecting portion (25) that connects the base portion (21) with the positioning member (23); the base portion (21) is attached to the head protector (1) with a supporting shaft (57); and the easily bendable portion (38) is provided on one side of the positioning member (23), which is opposite to another side nearer to the predetermined pivot. A mechanism for attaching a rotating plate in a helmet according to Claim 2, characterized in that : the base portion (21) is attached to the head protector (1) with the supporting shaft (57) that rotatably supports the rotating plate (5) on the head protector (1), whereby the base portion (21) lies between the head protector (1) and the rotating plate (5). A mechanism for attaching a rotating plate in a helmet according to any one of Claims 1-3, characterized in that : the first cut (35) and the second cut (37) are provided in the positioning member (23) each at an angle ( 1 ) of 60°-120°, the angle ( 1 ) being formed by two radii of the positioning member (23), passing through the respective side ends of each cut (35, 37). A mechanism for attaching a rotating plate in a helmet according to Claim 4, characterized in that : the first cut (35) and the second cut (37) are provided in the positioning member (23) each at an angle ( 1 ) of 70°-110°, the angle ( 1 ) being formed by the two radii of the positioning member (23), passing through the respective side ends of each cut (35, 37). A mechanism for attaching a rotating plate in a helmet according to any one of Claims 1-5, characterized in that : the total (D 1 +D 2 ) of the depth (D 1 ) of the first cut (35) and the depth (D 2 ) of the second cut (37) is within the range of 1/3 to 4/5 of the height (H) of the positioning member (23). A mechanism for attaching a rotating plate in a helmet according to Claim 6, characterized in that : the total (D 1 +D 2 ) of the depth (D 1 ) of the first cut (35) and the depth (D 2 ) of the second cut (37) is within the range of 2/5 - 2/3 of the height (H) of the positioning member (23). A mechanism for attaching a rotating member in a helmet according to any one of Claims 2-7, characterized in that : the attaching member (19) further has a pair of right and left reinforcing portions (27) that extend from the positioning member (23) to the connecting portion (25) and laterally spread like gills on the right and left sides of their boundary and'its vicinity. A mechanism for attaching a rotating plate in a helmet according to any one of Claims 1-8, characterized in that : the guide groove (47) has one engaged opening (47a) for keeping in the fully closed condition, which is provided at one end of the guide groove (47), the other engaged opening (47b) for keeping in the fully opened condition, which is provided at the other end of the guide groove (47), and an arcuated groove (47d), which is of substantially circular arc and is substantially uniform in width and by means of which the two engaged openings (47a, 47b) communicate with each other, the center of a circle partially marked out by the circular arc substantially coinciding with that of the predetermined pivot; the substantially tubular positioning member (23) is held by the two engaged openings (47a, 47b) so as to almost remain its original form when it is fitted into each engaged opening (47a, 47b); and the substantially tubular positioning member (23) is elastically deformed by the arcuated groove (47d) when it is fitted into the arcuated groove (47d). A mechanism for attaching a rotating plate in a helmet according to Claim 9, characterized in that the engaged openings (47a, 47b) for keeping in the fully closed condition and in the fully opened condition, respectively, are each of substantially circular shape. A mechanism for attaching a rotating plate in a helmet according to Claim 9 or 10, characterized in that the inner side edge of the guide groove (47), which is nearer to the predetermined pivot, comprises a substantially nearer to the predetermined pivot, comprises a substantially smooth curve (62) which is shaped into a substantially circular arc and extends from the engaged opening (47a) for keeping in the fully closed condition to the engaged opening (47b) for keeping in the fully opened condition, the center of a circle partially marked out by the circular arc substantially coinciding with that of the predetermined pivot. A mechanism for attaching a rotating plate in a helmet according to any one of Claims 9-11, characterized in that the angle ( 5 ) of the arcuated groove (47d), formed by an angular spread at the predetermined pivot is within the range of 20°-45°. A mechanism for attaching a rotating plate in a helmet according to Claim 12, characterized in that the angle ( 5 ) of the arcuated groove (47d), formed by an angular spread at the predetermined pivot is within the range of 24°-40°. A mechanism for attaching a rotating plate in a helmet according to any one of Claims 10-13, characterized in that the ratio of the width of the arcuated groove (47d) to each diameter of the two engaged openings (47a, 47b) is within the range of 80/100 to 97/100. A mechanism for attaching a rotating plate in a helmet according to Claim 14, characterized in that the ratio of the width of the arcuated groove (47d) to each diameter of the two engaged openings (47a, 47b) is within the range of 85/100 - 95/100. A mechanism for attaching a rotating plate in a helmet according to anyone of claims 1-8 and 11, characterized in that : the guide groove (47) has a first engaged opening (47a) for keeping in the fully closed condition, which is provided at one end of the guide groove (47), a second engaged opening (47b) for keeping in the fully opened condition, which is provided at the other end of the guide groove (47), a third engaged opening (47c) for keeping in the defrosted condition, which is provided to be near to and partially overlap with the first engaged opening (47a), and an arcuated groove (47d), which is of substantially circular arc and is substantially uniform in width and by means of which the second engaged opening (47b) and the third engaged opening (47c) communicate with each other, the center of a circle partially marked out by the circular arc substantially coinciding with that of the predetermined pivot; the substantially tubular positioning member (23) is held by the three engaged openings (47a, 47b, 47c) so as to almost remain its original form when it is fitted into each engaged opening (47a, 47b, 47c); and the substantially tubular positioning member (23) is elastically deformed by the arcuated groove (47d) when it is fitted into the arcuated groove (47d). A mechanism for attaching a rotating plate in a helmet according to Claim 16, characterized in that the first, the second and the third engaged openings (47a, 47b, 47c) are each of substantially circular shape. A mechanism for attaching a rotating plate in a helmet according to Claim 16 or 17, characterized in that the angle ( 2 ) of between the center of the first engaged opening (47a) and the center of the second engaged opening (47b), formed by an angular spread at the predetermined pivot is within the range of 30°-60°. A mechanism for attaching a rotating plate in a helmet according to Claim 18, characterized in that the angle ( 2 ) of between the center of the first engaged opening (47a) and the center of the second engaged opening (47b), formed by an angular spread at the predetermined pivot is within the range of 35°-55°. A mechanism for attaching a rotating plate in a helmet according to any one of Claims 16-19, characterized in that the angle ( 3 ) of between the center of the first engaged opening (47a) and the center of the third engaged opening (47c), formed by an angular spread at the predetermined pivot is within the range of 6°-15°. A mechanism for attaching a rotating plate in a helmet according to Claim 20, characterized in that the angle ( 3 ) of between the center of the first engaged opening (47a) and the center of the third engaged opening (47c), formed by an angular spread at the predetermined pivot is within the range of 8°-13°. A mechanism for attaching a rotating plate in a helmet according to any one of Claims 16-21, characterized in that the angle ( 4 ) of the arcuated groove (47d), formed by an angular spread at the predetermined pivot is within the range of 15°-35°. A mechanism for attaching a rotating plate in a helmet according to Claim 22, characterized in that the angle ( 4 ) of the arcuated groove (47d), formed by an angular spread at the predetermined pivot is within the range of 18°-30°. A mechanism for attaching a rotating plate in a helmet according to anyone of claims 17-23, characterized in that the ratio of the width of the arcuated groove (47d) to each diameter of the three engaged openings (47a, 47b, 47c) is within the range of 80/100 - 97/100. A mechanism for attaching a rotating plate in a helmet according to claim 24, characterized in that the ratio of the width of the arcuated groove (47d) to each diameter of the three engaged openings (47a, 47b, 47c) is within the range of 85/100 - 95/100.

Inventors: TANAKA HARUO, TANAKA, HARUO
Applicants: SHOEI CO LTD, SHOEI CO., LTD.
Application year: 1997
Main classification: A42B3
IPC codes: A42B3