Visor and method of manufacture

Abstract

A visor for a helmet or the like has a curved, transparent shield with an inner surface and an outer surface. The shield is provided with attachment elements for connecting the visor to the helmet and further includes a viewing region having a photochromatic insert at its outer surface, capable of responding to incident light. The shield is formed of a first plastic material provided with an amount of UV stabilizing additives, the UV stabilizing additives protecting the first plastic material from degradation by UV radiation during use, and the insert includes a second plastic material without UV stabilizing additives or having substantially less UV stabilizing additives than the first plastic material. A manufacturing process for producing a visor with a functional insert region is also disclosed.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to visors, in particular to visors provided with photochromatic regions that can change colour or shade in reaction to incident light. The invention further relates to methods of manufacturing visors comprising active elements integrally moulded therewith. Such visors are particularly applicable to helmets such as motorcycle helmets and the like.[0003]2. Description of the Related Art[0004]It has long been desired to provide visors for helmets that can automatically change colour in response to incident light conditions. Driving in bright sunlight, especially when it has rained, or at sunrise or sunset can be hazardous but driving with a tinted visor at night is also dangerous and in many countries is illegal. Some helmets are provided with a secondary pull-down tinted visor or sun-strip that can partially overcome these inconveniences. Nevertheless, such arrangements are often bulky and co...

AI Technical Summary

Benefits of technology

[0012]Although various materials may be employed for the visor, preferably the first plastic material comprises polycarbonate. This is presently the most conventional material for helmet visors due to its excellent engineering properties and ease of manufacture and also for its optical properties and high impact resistance. Nevertheless, other alternatives to polycarbonate may be considered, including but not limited to acrylic based polymers, poly(methyl methacrylate) (PMMA), polystyrene, cyclic olefin polymers (COP), cyclic olefin copolymers (COC), polyurethane and cellulose acetate. In particular, where high impact resistance is less important, other materials may be preferred for the shield. An advantage of the invention is that the insert may still provide high impact resistance in the viewing region.

[0013]In one embodiment of the invention, the insert may be removably attached to the outer surface of the shield. By removably attached it is hereby intended that the insert may be attached and detached at will, allowing the visor to be used with or without the insert. To this end, mechanical attachment provisions may be provided on the shield and / or the insert. These can comprise clips, magnets, hook and eye fasteners, mushroom fasteners (3M Dual Lock™) and the like.

[0014]Most preferably, the insert and the shield are fused or melted or otherwise permanently joined to form an integral unit. This may be achieved by integrally injection moulding both elements to together. The resulting visor will preferably have a seamless join between the insert and shield, avoiding reflections, refraction, dirt and moisture ingress, sharp edges and the like. Although reference is made to injection moulding of both elements together, as will be explained further below, this does not necessarily require both elements to be injection moulded.

[0015]According to a preferred form of the invention, the insert has a thickness of between 0.3 mm and 0.7 mm, preferably around 0.5 mm. In general, increasing the thickness of a visor reduces light transmission and optical quality and should be avoided. For removable inserts, a greater thickness may be desirable to provide stability. For integral inserts, the insert may be relatively thinner and a material thickness of just 0.3 mm to 0.5 mm may be achievable. For general motorcycle use, the visor may have an overall thickness of between 2 mm and 3.5 mm. It may also be tapered from the edges to the middle in order to improve optical correctness. For an integrally formed visor, the insert thickness will determine the remaining space for flow of the injected shield material. A relatively thin insert may therefore be desirable. In this manner, it may even be possible to provide a visor with integral insert having an overall thickness no greater than a conventional visor. Also, such an integrally formed visor may have a stiffer structure and its impact resistance may be increased due to the laminate construction. According to an important aspect of the invention, a high impact insert may thus be combined with other lower impact materials for the shield which may be more beneficial from a moulding perspective, including materials that may be moulded at a lower temperature that would be less detrimental to a photochromatic pigment layer. In general, the insert will be curved to match the radius of the shield, having either a 2-D or a 3-D curvature. Preferably, the curves will match perfectly to avoid moulding material from entering a space in front of the insert. For removable inserts on 2D visors, the insert may be initially flat and may be curved to fit the visor on attachment. The insert may be provided with a functional coating on its outer surface, in particular, anti-scratch and anti-fog or hydrophobic coatings are desirable.

[0016]According to one preferred embodiment of the invention, the insert comprises a photochromatic layer between an inner and an outer protective layer, at least the outer protective layer comprising the second plastic material. Such a laminate sandwich construction has been found very effective in optimizing the properties of the photochromatic layer while adequately protecting and supporting it. The absence or reduction in UV stabilizers in the outer protective layer allows UV light to penetrate to activate the photochromatic layer.

[0017]The photochromatic layer may comprise a photochromatic pigment incorporated in a polymer matrix. A preferred form of pigment comprises molecules that break open when activated by UV radiation, causing them to refract the incident light. Exemplary compounds include oxazines and naphthopyrans. In order to operate effectively, such pigment molecules should be supported in a polymer matrix of relatively low molecular density compared to that of e.g. polycarbonate. A preferred matrix material comprises polyurethane although other similar polymers may be used. The matrix material may in particular act as an adhesive layer between inner and outer protective layers.

Problems solved by technology

Driving in bright sunlight, especially when it has rained, or at sunrise or sunset can be hazardous but driving with a tinted visor at night is also dangerous and in many countries is illegal.

Nevertheless, such arrangements are often bulky and complicated and may require costly helmet revisions to the shell and inner lining.

Nevertheless, the integration of such pigments into a visor is complicated.

Pigments introduced directly into the material forming the visor do not function adequately for various reasons.

UVB light in the range 280 nm to 315 nm is particularly damaging for many polymers and UV stabilizers are used to remove these wavelengths.

Even though the photochromatic pigments may be sensitive to other wavelengths outside this range, the overall effectiveness of the pigment is reduced.

Nevertheless, due to their position behind the visor such inserts only partially darken.

This allows an existing visor to be easily adapted but once applied, subsequent removal of the film is likely to leave the visor impaired.

Films applied in this manner are also often subject to peeling and may become unsightly.

Furthermore, many photochromatic pigments are adversely affected by moisture and such films do not always provide adequate protection in this sense, causing accelerated degradation of the pigments.

Although these solutions appear to provide a suitable way of attaching a photochromatic layer to a visor, they do not address the problems of ensuring adequate operation of the photochromatic pigments while avoiding photo-degradation of the visor material.

They also fail to address the problems of injection moulding the visor and the film in a single process.

The heat required during injection moulding can cause many photochromatic pigments to be irreparably damaged.

Manufacture of visors is a relatively costly exercise in that each visor must be injection moulded in an expensive, custom made two-part mould.

A major factor in the expense of the mould is the high quality finish on the inner mould surface.

Although once produced, a single mould may be used for many thousands of visors, each change in shape or detail will require manufacture of a new mould at considerable expense.

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