Note: Descriptions are shown in the official language in which they were submitted.
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HELMET FACE SHIELD
TECHNTCAL FIELD
The present invention relates generally to shields for
protective helmets used for snowmobiling, motorcycle riding
and the like. More particularly, the present invention
relates to a protective face shield having a removable lens
portion.
BACKGROUND OF THE INVENTION
Protective helmets such as, for example, those used for
snowmobiling and motorcycle riding, are well known. They
typically include a generally transparent face shield or
lens. Two distinct types of helmet face shields are
typically employed. Shields having a single pane lens are
generally used in warmer environmental conditions. Face
shields having a dual lens construction comprising an inner
lens and an outer lens, are most often used in colder and
more humid conditions. In cold weather, single pane lenses
tend to fog up, consequently impairing the rider's vision.
However, single pane lenses generally provide better visual
properties in comparison with double pane lenses, the
thinner single lens causing less optical distortion.
Nonetheless, double pane lenses are almost universally used
in colder climatic conditions, in order to help keep the
face shield substantially free of condensation.
Many kinds of face shields employ additional techniques to
further attempt to prevent fogging. These include lenses
having an electrical heating system, wherein an inner lens
surface is coated with an electrically conductive film and
two electrodes, on opposite edges of the lens, permit an
electrical current to flow across the film covering the
lens, thereby inhibiting condensation build up thereon.
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Other anti-condensation methods are also well known, such
as those providing directed ventilation along an inner
surface of the lens or employing a hydrophilic anti-
condensation layer, in the form of a sheet, film or other
covering, that is fitted within an outer lens. These
additional anti-condensation devices are typically used in
combination with a double-paned lens.
Most face shields having such a double pane construction
comprise two lenses that are contained within a separately
constructed perimeter frame, which provides support for the
double-paned lens and permits pivotable attachment thereof
to the helmet. Double pane lens assemblies are
significantly thicker than single paned lenses, and their
attachment to some helmets which are not specifically
designed to accommodate them can accordingly be difficult
without the rather bulky perimeter frame. These face
shield perimeter frames can significantly add to the
manufacturing cost of the face shield assembly, unduly add
bulk and weight to the helmet, and contribute to
aerodynamic inefficiencies and increased wind noise.
Most known face shields that do not comprise perimeter
frames, and have double pane lenses or have a hydrophilic
layer superimposed on a single lens, do not permit removal
of one of the lens panes or the anti-condensation layer.
However, it has been known to provide such a frame-free
face shield for a protective helmet having a detachably
engaged inner lens. US Patent 5,765,235 issued June 16,
1998 to Derek Leslie Arnold, for example, discloses an
anti-condensation visor comprising an outer visor for
attachment to a helmet and an inner visor, made of
hydrophilic material, detachably fitted against the inside
wall of the outer visor and held there against by at least
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one mechanical retaining element. The inner visor must
rest against the inside wall of the outer visor in such a
way that no space is left between them. US Patent
4,584,721 issued April 29, 1986 to Tamenobu Yamamoto,
discloses a helmet face shield having an electric heating
device for preventing fogging. The device comprises a
removable inner lens piece attached behind the outer helmet
lens. The inner lens piece is generally engaged to the
outer lens by a mechanical engagement element such as a
snap fastener.
SUN~iARY OF THE INVENTION
It is an object of the present invention to provide an
improved face shield for a protective helmet.
It is another object of the present invention to provide a
face shield having a frameless main lens capable of
receiving a second lens portion that can be sealed to the
main lens with an air gap therebetween to create a double
pane lens.
The present invention permits an inner lens to be engaged
to an outer lens such that it is offset therefrom but
sealed thereto. The present invention further permits the
single pane .lens to be converted into a double pane lens
having improved anti-condensation properties provided by an
air gap trapped between the inner and outer lenses of the
sealed double pane lens.
Therefore, in accordance with the present invention, there
is provided a face shield for headgear comprising: a
generally transparent main lens adapted for engagement to
the headgear; the main lens comprising curved inner and
outer main lens surfaces and having a central recessed
portion, the recessed portion having a recessed curved
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inner lens surface and a recessed curved outer lens
surface, the recessed inner lens surface and the recessed
outer lens surface being respectively offset from the
curved inner and outer main lens surfaces; and the recessed
portion being adapted to receive a secondary lens therein
such that a sealed air gap is formed between the secondary
lens and the main lens, thereby forming a sealed double
pane lens having anti-condensation properties.
There is also provided, in accordance with the present
invention, a face shield for headgear comprising: a
generally transparent main lens adapted for engagement to
the headgear; the main lens comprising curved inner and
outer main lens surfaces and having a central recessed
portion, the recessed portion having a recessed curved
inner lens surface and a recessed curved outer lens
surface, the recessed inner lens surface and the recessed
outer lens surface being respectively offset from the
curved inner and outer main lens surfaces; and a secondary
lens, selectively engageable within the recessed portion of
the main lens such that a sealed air gap is formed between
the secondary lens and the main lens, thereby selectively
forming a sealed double pane lens having anti-condensation
properties.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the present invention
will become apparent from the following detailed
description, taken in combination with the appended
drawings, in which:
Fig. 1 is a perspective view of a face shield according to
the present invention engaged to a protective helmet;
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Fig. 2 is an exploded perspective view of the helmet face
shield of Fig. 1, showing a main lens and a secondary lens;
Fig. 3 is a front elevation view of the helmet face shield
of Fig. l;
Fig. 4 is a horizontal cross-sectional view taken along
line 4-4 of Fig. 3; and
Fig. 5 is a perspective view of an alternate embodiment of
the secondary lens for engagement with the main lens of
Fig. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Fig. l, the face shield 10 is adapted to be
engaged to, and used with, headgear such as a protective
helmet 13 as conventionally used for motorcycle riding,
snowmobiling, flying and the like. The face shield 10 is
also adapted for use with other protective headgear
comprising a transparent face shield, such as paintball
masks for example. The face shield 10 comprises primarily
a generally transparent main lens 12, thereby providing a
single pane lens that does not require a perimeter frame
for support or engagement to the protective helmet 13. The
main lens 12 is preferably a moulded plastic one-piece
element, having a thickness of approximately 2 mm (about
0.07874 inches). The main lens 12 is preferably injection
moulded, however other manufacturing techniques could also
be used, such as drape or vacuum moulding for example. One
skilled in the art will also appreciate that the main lens
12 can have a non-uniform thickness throughout.
Particularly, as is known in the art, the lens can be
formed such that it is thickest at a center point thereof
and becomes gradually thinner towards each edge of the
lens. This causes the least distortion of light passing
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through the lens, enabling the single paned main lens 12 to
provide substantially distortion free optical
characteristics. The main lens 12 is preferably formed
having a curvature about a substantially vertical axis that
substantially corresponds to that of the protective helmet
13 to which it is to be engaged, however it generally
comprises a substantially semi-circular shape. The main
lens 12 can also be outwardly convex throughout the semi-
circular length thereof, having a second curvature about a
substantially horizontal axis, creating a complex lens
curvature. The curved main lens 12 comprises a curved
inner main lens surface 14 and a curved outer main lens
surface 16.
The main lens 12 comprises a central recessed portion 18,
having a recessed curved inner surface 20 and a recessed
curved outer surface 22, the recessed portion 18 being
preferably outwardly offset from the main lens 12. The
recessed portion 18 preferably comprises most of the main
lens 12, such that the recessed portion 18 substantially
covers the entire visual field of the user. The offset
edges 24 of the recessed portion 18 are therefore located
just at the edge or just outside the viewing field of the
user looking through the face shield 10 when it is disposed
in a normal operating position on the protective helmet 13.
The size and shape of the recessed portion 18 preferably
corresponds to a forward opening 15 in the protective
helmet 13, such that the offset edges 24 of the recessed
portion 18 are near the perimeter of the opening 15 in the
helmet 13.
As seen in Fig.l, helmet engaging members 28 are fixed to
the main lens 12 at remote mounting ends 16 thereof . The
helmet engaging members 28 are fixed to the remote ends 26
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of the main lens 12, and are preferably pivotally
engageable to the sides of the protective helmet 13, such
that the entire face shield 10 can be pivoted to open or
close the opening 15 in the helmet 13. The main lens 12
can thus be used alone as a single pane helmet visor when
required. This may be most desirable in warm environmental
operating conditions, and for particular applications, such
as for motorcycle riding for example.
However, in colder conditions and applications, such as for
snowmobiling for example, a single pane helmet lens tends
to fog up. As such, the main lens 12 of the face shield 10
can be modified to provide a double pane lens 19, as seen
in Figs. 3 and 4, if desired. A generally transparent
secondary lens 30, best seen in Fig. 2, is receivable into
the recessed portion 18 of the main lens 12, such that a
sealed double pane helmet lens 19 is formed. The secondary
lens 30 comprises an inner curved lens surface 32 and an
outer curved lens surface 34. The secondary lens 30 is
generally formed with a radius of curvature somewhat
similar to that of the main lens 12, however the secondary
lens 30 is preferably provided with a radius of curvature
that is slightly larger than that of the main lens 12.
This requires a slight deflection of the secondary lens 30
for it to fit within the recessed portion 18, providing a
slight pre-tension in the secondary lens 30, and thereby
helping it to remain engaged within the recessed portion
18. The secondary lens 30 is positioned within the
recessed portion 18 such that an air gap 40 remains between
the outer curved lens surface 34 of the secondary lens 30
and the curved inner main lens surface 14 of the main lens
12. The secondary lens 30 preferably has a lens thickness
that is less than the offset distance of the recessed
portion 18 from the curved lens surfaces 14,16 of the main
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lens 12. The common distance that the recessed curved
inner lens surface 20 and the recessed curved outer lens
surface 22 are respectively offset from the inner main lens
surface 14 and outer main lens surface 16 is preferably
approximately 3 mm (about 0.11811 inch). If a secondary
lens 30 having a 2 mm (about 0.07874 inch) thickness is
used, for example, the air gap 40 will be approximately 1
mm (about 0.03937 inch) wide. It will be understood,
however, that other air gap widths and secondary lens
thicknesses can be similarly used to achieve the same
effect.
Unlike many double paned lens assemblies of the prior art,
the present double pane lens 19 does not require a
separately constructed perimeter frame which provides
support for the double paned lens assembly, as the
secondary lens 30 is retained within the recessed portion
18 of the main lens 12. The elimination of the perimeter
frame results in reduced manufacturing, and subsequently
retail, costs, a reduction in the overall weight and size
of the face shield 10 having the double pane lens 19, and
improved aerodynamics. By smoothly integrating the
frameless main lens 12 into the helmet 13 such that the
outer main lens surface 16 is substantially flush with an
outer surface of the helmet 13, reduced aerodynamic drag
and noise is provided.
The secondary lens 30 preferably has a gasket seal 36
disposed around the perimeter thereof. The gasket seal 36
is preferably disposed on one of the outer curved lens
surface, and a peripheral edge defined between the inner
curved lens surface 32 and the outer curved lens surface
34. When disposed on the outer curved lens surface, the
perimeter gasket seal 36 helps to space the secondary lens
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30 away from the main lens 12 when positioned within the
recessed portion 18, ensuring that a fairly constantly
spaced air gap 40 is maintained therebetween. The gasket
36 also seals the air gap 40, ensuring that a sealed double
pane lens 19 is maintained. While the gasket seal 36 is
preferably disposed on the secondary lens 30 before
insertion of the secondary lens 30 into the recessed
portion 18 of the main lens 12, it can similarly be
inserted independently into the recessed portion 18 before
the secondary lens 30 is positioned therein. The gasket
seal 36 is preferably made of generally transparent
material, such that vision at the offset edges 24 between
the secondary lens 30 and the main lens 12 is not obscured.
The gasket seal 36 is preferably as transparent as
possible, but materials that are merely translucent can
also be employed. A generally transparent silicone bead,
for example, can be used as the gasket seal 36. Such a
silicone bead is preferably sufficiently compressible when
the secondary lens 30 is engaged within the recessed
portion 18, such that a slight vacuum is created between
the secondary lens 30 and the main lens 12, thereby holding
the secondary lens 30 in place therein. The slightly
larger radius of curvature of the secondary lens 30
relative to the main lens 12 further provides frictional
retention of the secondary lens 30 within the recessed
portion 18 of the main lens 12. Other substantially
permanent retention means, such as adhesives or sealing
tape for example, can be used to fix the secondary lens 30
within the recessed portion 18 and to seal the air gap 40
therebetween.
Alternately, other temporary retention means can be used
which permit the user to add and/or remove the secondary
lens 30 from the main lens 12 whenever required. This may
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be desirable, for example, if a protective helmet 13 having
the face shield 10 is to be used both for motorcycle riding
in warm weather and snowmobile riding in cold weather. In
such a case, the main lens 12 is preferably used by itself
in the warmer conditions to provide improved visibility.
The secondary lens 30 may be subsequently inserted within
the recessed portion 18 of the main lens 12 to farm the
double pane lens assembly 19 in colder conditions, to
provide improved anti-condensation properties. In such a
case, the secondary lens 30 is therefore engaged within the
recessed portion 18, using removably fastenable members
such as temporary adhesives, removable two-sided tape, or
hook and loop fasteners for example. With such temporary
fastening means, the secondary lens 30 nonetheless
preferably forms a seal with the main lens 12 such that the
sealed air gap 40 is provided therebetween in the recessed
portion 18. The temporary fastening means may provide the
sealing themselves, or an additional seal may be provided
in addition to the temporary fastening means.
The addition of the secondary lens 30 to the main lens 12
can be done either by the user as an after-market upgrade,
or by the manufacturer, permitting a more cost effective
way of producing different face shields for various
applications. Particularly, rather than producing two
distinct product lines, a common main lens 12 can be used
alone or in combination with a secondary lens 30 to create
a double pane lens 19. For example, the main lenses 12 can
be either sold alone as a single pane face shield, or be
permanently assembled with the secondary lens 30 in the
factory for sale as a sealed double pane lens I9
particularly adapted for cold climatic applications. The
secondary lenses 30 could also be sold independently, for
selected assembly by the user for converting a single pane
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lens into a cold weather, sealed double pane lens 19. The
secondary lens 30 can either be as transparent as the main
lens 12, or can comprise a tint, such that a shaded double
pane lens 19 is created.
The seal formed between the secondary lens 30 and the main
lens 12, ensuring the sealed air gap 40 therebetween,
maintains thermal properties of the double pane lens 19
formed by the assembly of the main lens 12 and the
secondary lens 30. Such a sealed, dual plane lens 19 is
much more effective at preventing condensation at low
temperatures than single paned lenses or double lenses that
do not form a sealed air gap therebetween.
A secondary lens 50 of an alternate embodiment, shown in
Fig. 5, is alternately used in place of the secondary lens
30 for engagement with the main lens 12 to form the sealed
dual plane lens 19. The alternate secondary lens 50 is
similarly shaped to the secondary lens 30, and is
equivalently receivable into the recessed portion 18 of the
main lens 12. The secondary lens 50 is generally
transparent, although can comprise a tint if desired, and
comprises a curved inner lens surface 52 and a curved outer
lens surface 54. The secondary lens 50 preferably includes
a perimeter seal 56 thereon, disposed either about a
perimeter of the curved outer lens surface 54 or on the
perimeter edge between the inner curved lens surface 52 and
the curved outer lens surface 54. The secondary lens 50
differs from the secondary lens 30 in that it comprises an
electrical heating system 60 which provides additional
anti-fogging capabilities. The electrical heating system
60 generally includes at least two elongated electrodes,
normally an upper electrode 62 extending along an upper
margin of the secondary lens 50 and a lower electrode 64
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extending along a lower margin of the secondary lens 50.
While the upper and lower electrodes 62,64 are preferably
located on the outer lens surface 54, they can be
alternately disposed on the inner lens surface 52 without
significantly altering their anti-condensation effect.
Between the upper and lower electrodes 62,64 is provided a
transparent electro-conductive film 68 substantially
covering the entire outer lens surface 54. The transparent
electro-conductive film 68 is preferably a thin layer of
indium tin oxide (ITO), applied by sputter coating on the
outer curved lens surface 54. Such an ITO coating provides
high visible light transmission, low reflectivity and
substantially uniform electrical conductivity. Insulated
electrode contacts 66 are in electrical contact with the
upper and lower electrodes 62,64 and extend through the
secondary lens 50 to the inner lens surface 52. Conductors
(not shown) linked to a power supply can then be engaged to
the electrode contacts 66, such that power is supplied
across the upper and lower electrodes 62,64, resulting in
an electrical flow across the electro-conductive film 68.
The conductors can comprise wires or another electro-
conductive film, such as an electrically conductive silk
screen ink, for example, formed on the inner lens surface
52. Another transparent electro-conductive film on the
inner lens surface 52 may be used as the conductor linking
the power supply to the electrode contacts 66. This
eliminates any possible vision impeding elements being
located on the lens surfaces. Such a strip of transparent
ITO film extends along the inner main lens surface 14 of
the main lens 12 and inner lens surface 52 of the secondary
lens 50, linking a connection to the power supply within
the helmet attachment members 28 to the electrode contacts
66 on the secondary lens 50. Resistance to the flow of
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electricity across the electro-conductive film 68, between
the upper and lower electrodes 62,64 on the outer lens
surface 54, causes heat. This heating of the secondary
lens 50 thereby further helps to prevent or reduce the
formation of fog, frost and ice on the sealed double pane
lens assembly 19, comprising the main lens 12 and the
secondary lens 50. Much as the secondary lens 30, the
alternate secondary lens 50 having the electrical heating
system 60 can be either permanently fixed within the
20 recessed portion 18 of the main lens 12, or can be
selectively removable therefrom as described above.
Although the electrical heating system 60 is described
herein as being preferably engaged on the secondary lens
50, it is to be understood that it can also be disposed on
the main lens 12, and particularly on the recessed curved
inner surface 20.
The frame-less face shield 10 according to the present
invention has great versatility. The main lens 12 can be
used alone as a single pane, warm weather shield. When
required, this can be converted into a cold weather, sealed
double pane lens 19 with the addition of one of the
secondary lenses 30 or 50 into the central recessed portion
18 of the main lens 12, providing a sealed air gap 40
therebetween. This provides a face shield having a thermal
barrier, the double pane lens 19 providing improved anti-
condensation properties at low temperatures. The best
anti-condensation abilities of the face shield 10 are
provided when using the alternate secondary lens 50 having
the electrical heating system 60 therein, which may be
suited for very cold environmental conditions. The face
shield 10 can therefore be selectively adapted for
different uses and different environmental conditions as
required, whether before consumer sale or after-market.
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It is understood that numerous modifications to the face
shield according to the present invention will be evident
to those skilled in the art. Accordingly, the above
description and accompanying drawings should be taken as
illustrative of the preferred embodiments of the invention
and not in a limiting sense. It will be further understood
that the present invention is intended to cover any
variation, use or adaptation of the invention following, in
general, the principles of the invention and including such
departures from the present disclosure as come within known
or customary practice within the art to which the invention
pertains, and as may be applied to the essential features
herein set forth and as follow in the scope of the appended
claims.
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