Shield structure for helmet

Abstract: An object of the present invention is to provide a shield for a helmet in which an inner shield (1) and an outer shield (2) are fixed and held while their mutual sealing characteristics are being positively assured and the inner shield (1) and the outer shield (2) can be separated from each other. The present invention is constituted such that another shield (2) is removably attached to an outer side of a shield (1) attached in such a way that it can be freely turned in an upward or downward direction in respect to a helmet main body (B) through a seal member (11) having a resiliency installed along a substantial outer circumference of a visual field range and concurrently a tension force for generating a force for press adhering the aforesaid seal member (11) is applied to the shield (2) outside of it and then it is supported at the inner shield (1).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a shield structure for a helmet, and more particularly a shield installed outside a forward opening formed in a helmet. 2. Description of the Prior Art Commonly, a helmet may have a shield comprising one sheet or plate of synthetic resin (for example, a plate member of polycarbonate resin) . This shield, when closed, is used for protecting the user's face against rain, wind, dust, insects and small stones or the like. However, in the case that the helmet is used under a state in which the shield is closed, there occurs a problem that the shield is fogged with breath discharged by a user or sweat caused by an increased temperature within the helmet or the like. This shield misting condition is produced by a temperature difference across the shield, wherein due to this fact, as means for reducing the temperature difference across the shield, there is employed a ventilation means for taking surrounding atmosphere into the inside part of the helmet so as to feed the air along the inner surface of the shield, thereby attenuating this misting condition . However, as this system provides a device for taking in the surrounding atmosphere into the helmet itself, the productivity or design of the helmet may be influenced. Due to this fact, it has been required to provide a shield capable of accomplishing a complete anti-misting situation only with the shield, without influencing the productivity or design of the helmet. One example of such an anti-misting construction is the provision of an integral shield having dual-structure. The configuration is such that a seal member is adhered and fixed along a substantial outer circumference of a visual range between an inner plate and an outer plate so as to form a closed space becoming a heat insulated layer between the inner plate and the outer plate, wherein a temperature difference across the plates is reduced and an anti-misting against the inner plate of the shield structure is performed. Examples can be found in the prior art. US 5671483 to Reuber describes a similar structure, but as the outermost shield is not under tension. US 4101980 to Stepan et al. also has a similar structure, but has the disadvantage that the field of vision is impaired by the edges of the external shield. SUMMARY OF THE INVENTION However, since the aforesaid anti-misting structure for the shield is made such that an inner plate and an outer plate are adhered to each other and assembled integrally to form a closed space, it is hard to keep its durability while assuring an air-tightness by holding a desired curve and its manufacturing cost is also high due to the aforesaid form. In addition, in the case that a seal member for use in forming a closed space between the inner plate and the outer plate is deteriorated to cause the air-tightness to be damaged due to damage or the like, it is impossible to perform a partial replacement of the member to recover function and there may be provided a disadvantage that the entire assembly must be broken to replace the broken assembly with a new shield. Further, in order to improve the anti-misting effect in response to the surrounding circumstances, it is also impossible for a user by himself or herself to apply an anti-misting processing such as a coating of surface active agent or the like at the inside part of the outer plate or the outside part of the inner plate. The present invention has been invented in view of the aforesaid problems found in the prior art and it is an object of the present invention to provide a shield structure for a helmet in which an inner shield and an outer shield can be fixed and held with assured mutual sealing characteristics and can also be separated from each other. The technical means provided by the present invention to solve the aforesaid problems is characterized in that a dual structure is comprised of an inner shield for fixing to a helmet in such a way that it may be pivoted in an upward or downward direction and an outer shield detachably mounted in a specified space outside the inner shield, a seal member is arranged and fixed between the inner shield and the outer shield along a substantial outer circumference of a visual field range so as to form a heat insulated air layer inside the seal member, and a supporting means is provided for applying a tension force for generating a force to press the seal member to the inner shield . The aforesaid visual field range has a maximum range in which forward visual confirmation is not prohibited. For example, it is substantially the same range as that of a front surface opening formed at a full-face type helmet . In case of an open-face type helmet, it is defined as the same range as that of the shield structure used in the aforesaid full-face type helmet. The inner shield and the outer shield each comprise a plate member made of polycarbonate resin, and the seal member arranged between the inner shield and the outer shield is formed from foam rubber or the like. Then, although the seal member may be fixed to either the outer surface of the inner shield or the inner surface of the outer shield, in the case that application of the single inner shield after separating the outer shield is considered, it may be satisfactory to fix it to the inner surface of the outer shield. In addition, the supporting means for the outer shield is arranged at arms fixed to or removed from the helmet and connected and fixed to both right and left sides of the inner shield or arranged at the outer surfaces of the right and left sides of the inner shield which is removably mounted on the helmet. The supporting means arranged at the arms comprises engaging protrusions projected and formed at the inner surface of the arms. An outer shield insertion space is defined between the inner surface of the arms and the outer surface of the right and left sides of the inner shield. The engaging holes formed in the outer shield are removably engageable with the engaging protrusions. The engaging protrusion are tapered , riding over the outer shield in the outer shield inserting direction and engaging with the outer shield in the outer shield ejecting direction. Further, the inner shield is heated and bent to be closely contacted with an edge forming rubber fixed to an eye port trim of a front opening (a window hole) of the helmet. In contrast, the outer shield is heated and bent to have a shape in which its rate of curvature is set to be at most equal to or less than that of the inner shield, or flat.Either shield can also be created by injection molding techniques. Accordingly, since the outer shield is bent along the inner shield, it is convenient to create an outer shield of which wall thickness is thinner than that of the inner shield. In addition, the shield structure to which the present invention belongs is not limited to the seal installed at a full-face type helmet, but includes a shield structure to be installed in an open face type helmet. In accordance with the aforesaid means, since the shield structure is formed with a tight-closed space of heat-insulated air layered between the inner shield and the outer shield, the shield structure is prevented from being misted under an action of the tight-closed space. Since the shield structure is constructed such that the outer shield can be separated from the inner shield, when either one of the inner shield or the outer shield is scratched or damaged or when the seal material fixed to any one of the inner shield or the outer shield is deteriorated or damaged, it is possible to recover to the initial state only with replacement of the corresponding member. Additionally, it is also facilitated to apply an anti-misting processing such as coating of a surface active agent at an inner side surface of the outer shield and an outer side surface of the inner shield in order to improve an anti-misting effect as required. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an exploded perspective view for showing one preferred embodiment of a shield structure of the present invention. Fig. 2 is a perspective view with a part of the shield structure being broken away. Fig. 3 is a sectional view taken along a line Ill-Ill of Fig. 2 with a part of the shield structure being broken away. Fig. 4 is an enlarged sectional view taken along a line IV-IV of Fig. 3. Fig. 5 is a front elevational view for showing a hook mechanism for engaging and supporting the shield structure to a helmet. Fig. 6 is an enlarged sectional view taken along a line VI-VI of Fig. 5. DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, one preferred embodiment of the present invention will be described. Fig. 1 is a perspective view for showing the shield structure of the present invention and a helmet to which the shield structure is installed. In this figure, A denotes a shield structure which is comprised of an inner shield 1 and an outer shield 2, wherein the shield structure A is attached in front of a forward opening (a window hole) 3 formed at a full-face type helmet B in such a way that it may be rotated in an upward or downward direction and it can be removably installed. Although the outer shield 2 constituting the shield structure A is a linear flat plate before it is assembled to the inner shield 1, the figure shows a state in which it is supported outside the inner shield 1. The inner shield 1 constituting the shield structure A is made such that a plate member of polycarbonate resin is "heated and bent" and arms 4, 4' having engagement members 6 to be engaged to or removed from hook members fixed to the right and left side surfaces of the helmet B are connected to and fixed to both right and left sides of it with a screw 5. As shown in Figs. 3 and 4, connecting and fixing of the inner shield 1 with the arms 4, 4' are carried out such that stepped shafts 7 are integrally projected at the upper part and the lower part of the inner surface of each of the arms 4, 4', fixing holes 8 formed at an upper part and a lower part of the right side end and the left side end of the inner shield 1 are fitted to the stepped shaft 7 and concurrently the screw 5 is threadably fitted to the stepped shaft 7 through a washer 9 and fixed there. Engaging protrusions 10 constituting the supporting means for engaging with and holding the outer shield 2 are projected and formed around the stepped shafts 7 at the upper part and the lower part in the inner surface of each of the arms 4, 4' and in front of a fixing and inserting direction of the outer shield 2 to be described later and at the same time the engaging protrusions 10 are formed into tapered protrusions (having a triangle sectional surface) which the outer shield 2 rides over when it is inserted and engages with it when the outer shield 2 is pulled out. The stepped shafts 7 formed at the arms 4, 4' may act as position setting members not only for fixing the inner shield 1 while assuring the inner surfaces of the arms 4, 4' and a space into which the outer shield 2 to be described later is inserted, but also for engaging and holding the outer shield 2 to be inserted at a predetermined position. The outer shield 2 curved along an outside part of the aforesaid inner shield 1 , is cut and formed to follow the outer shape of the inner shield 1 by applying a thinner plate member of polycarbonate resin than that of the inner shield in the same manner as that of the inner shield 1, wherein to one side surface of the plate member is adhered and fixed a belt-like resilient seal member 11 in such a shape as one substantially coinciding with the shape of the front opening (a window hole) 3 opened at the helmet B. Then, each of the upper part and the lower part of the right side and the left side of the outer shield 2 is formed with an engaging hole 12 removably engageable with the engaging protrusions 10 of the supporting means formed at the arms 4, 4' connected to and fixed to the right side and the left side of the aforesaid inner shield 1 and with hook recesses 13 engaged with the stepped shafts 7, respectively. In addition, to the right and left sides of the surface having the resilient member 11 of the outer shield 2 adhered and fixed thereto are fixed spacers 14 made of relative hard resilient material positioned outside the seal member 11 and having a substantial same height as that of the seal member 11. Additionally, to the rear position from the fixing part of the inner shield 1 at the inner surfaces of the aforesaid arms 4, 4' are the engaging members 6, fixed with screws and engaged with or disengaged from the hook members 15 constituting hook mechanisms fixed to the right and left side surfaces of the helmet B. The hook mechanism will be described in reference to Figs. 5 and 6, wherein each of the hook members 15 fixed to the right and left side surfaces of the helmet B is constituted by a supporting shaft 15a made of synthetic resin material and a hook ring 15b formed outside the supporting shaft 15a, and the hook ring 15b is formed with a deformation part 15c at its part of outer circumference for realizing a spring action for generating a fixing and deformation. In turn, each of the engaging members 6 fixed to the inner surfaces of the arms 4, 4' of the shield structure A is made of synthetic resin and formed into an ellipse shape plate, the supporting shaft 15a of the hook member 15 is fitted to its central part and at the same time it is formed with an ellipse hole 6a enabling a pulling-out motion of it for engaging or disengaging of the shield structure A, engaging protrusions 6b, 6c engaged with the aforesaid hook ring 15b are formed at an outer circumferential edge on a long diameter line extending along an outer shield pulling-out direction, and a stopper 6d for preventing the shield structure A from being disengaged from the helmet B under a closed state is formed at an outer circumferential edge at a substantial intermediate position between the aforesaid engaging protrusions 6b, 6c. In the case that the shield structure A constructed as described above is to be installed at the helmet B, the engaging members 6 for the arms 4, 4' are aligned on the hook member 15 and pushed against the helmet B, resulting in that the hook ring 15b is pushed wide in a radial direction and the engaging protrusions 6b, 6c enter below the hook ring 15b so as to accomplish its hooked state. In turn, in the case that the shield structure A is to be removed from the helmet B, the shield structure A is turned upwardly from its full-closed state, the stopper 6d of the engaging member 6 is removed from the hook ring 15b of the hook member 15, wherein at this position, the arm is pulled in its drawing direction, the engaging protrusion 6c engaged with the hook ring 15b is removed and then the arm is pushed into an inserting direction to cause the engaging protrusion 6b to be removed from the hook ring 15b, resulting in that the arm of the shield structure A is removed from the helmet B. Then, engaging or disengaging between the inner shield 1 and the outer shield 2 constituting the shield structure A will be described, wherein when the outer shield 2 is fixed to the outside part of the inner shield 1, at first one end of the outer shield 2 is inserted into either the arm 4 or the arm 4' connected to the side part of the inner shield 1, the hook recess 13 is engaged with the stepped shaft 7 and concurrently the engaging hole 12 is fitted and engaged with each of the engaging protrusions 10 and hooked and fixed. Then, the other end of the outer shield 2 is inserted into another arm while the outer shield 2 is being pushed against the surface of the inner shield 1, each of the hook recess 13 and the engaging hole 12 is engaged from each other and fixed to complete the shield structure A. Under this completed state, the seal member 11 adhered to the inner surface of the outer shield 2 is closely contacted with the outer surface of the inner shield 1, thereby a closed space 16 acting as a thermal insulated air layer is defined and formed between the inner shield 1 and the outer shield 2. The shield structure A is prevented from being fogged under an action of the thermal insulated air layer in the closed space 16. In addition, in the case that the outer shield 2 is to be separated from the inner shield 1, the upper part and the lower part near the arm rather than the spacer 14 at the outer shield 2 are pushed down to the inner shield 1, resulting in that the engaging hole 12 is moved away from the inner surface of the arm, thereby the engaging hole 12 is removed from each of the engaging protrusions 10 and can be pulled out of the arm. The aforesaid operation is also carried out for the other side to enable the outer shield 2 to be easily separated from the inner shield 1. Accordingly, in the case that the seal member fixed to the outer shield is deteriorated or damaged, only the outer shield is replaced with a new one to enable it to be recovered to its original state. In addition, in the case that it is not necessary to perform an anti-misting operation with the aforesaid thermal insulated air layer, the outer shield 2 is removed by the aforesaid operation and the helmet may be used only with the inner shield. The shield structure of the present invention can assure durability while keeping an air-tightness between the inner shield and the outer shield and at the same time the shield of dual structure having the thermal insulated air layer can be easily manufactured under the configuration described in the claims. Since the outer shield can be separated from the inner shield, such as in the case that the seal member is deteriorated to cause air-tightness to be damaged, only the shield having the aforesaid seal member fixed thereto is replaced with a new one to enable it to become its initial state and this system is quite convenient in use. In this case, a troublesome handling in manufacturing step can be saved when compared with an integral type of the existing outer shield and inner shield as it is not necessary for the outer shield to fulfill the same degree of condition as that of the inner shield, resulting in that its corresponding manufacturing cost can be restricted. In addition, it is also facilitated to perform an anti-misting processing such as coating of surface active agent or the like against the inside surface of the outer shield and the outside surface of the inner shield in order to improve an anti-misting effect as required. Further, it is also possible to use as the outer shield an item colored in light color or raw material for preventing ultra-violet ray and in this case, it is possible to eliminate necessity to put on a sun-glass within the helmet during a day time in summer season. Having described specific preferred embodiments of the invention with reference to the accompanying drawings, it will be appreciated that the present invention is not limited to those precise embodiments, and that various changes and modifications can be effected therein by one of ordinary skill in the art without departing from the scope of the invention as defined by the appended claims.

Claims: A shield structure (A) for a helmet (B), comprising an inner shield (1) adapted to be attached to the helmet (B) such that it may be rotated in an upward or downward direction in respect to the helmet main body, an outer shield (2) removably attached to the helmet (B) , with a resilient seal member (11) arranged between the inner and outer shields (1, 2) and along a substantial outer circumference of a visual field range, the inner and outer shields (1, 2) being connected to the helmet (B) by a first and second arm (4, 4'), characterised in that a first space is defined between the inner shield (1) and the first arm (4) and a second space is defined between the inner shield (1) and the second arm (4'), said first and second spaces each allowing reception of an end of the outer shield (2), the arms (4, 4') including protrusions (10) which inter-engage with holes (12) formed in ends of the outer shield (2), the inter-engagement of which results in the application of a tension force which generates a force to press fit said seal member (11) to the inner shield (1). A shield structure (A) for a helmet (B) according to Claim 1, characterised in that said protrusions (10) are tapered such that the outer surface of the outer shield (2) rides over the same when the ends of the outer shield (2) are inserted into said spaces, and inter-engage with the holes (12) of the outer shield (2) when the outer shield (2) is moved in an outwardly direction with respect to the inner shield (1).

Inventors: ARAI MICHIO, ARAI, MICHIO, Arai, Michio c/o Arai Helmet Ltd
Applicants: ARAI HELMET LTD, ARAI HELMET LIMITED
Application year: 1999
Main classification: A42B3
IPC codes: A42B3