Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SPORT SUNGhASSES RESISTANT TO FOGGING
Field of the Invention
a
The present invention relates generally to
protective eyeglasses or goggles which protect a wearer's
eyes, and more particularly to anti-fogging sunglasses
which incorporate a ventilation channel to promote air
circulation behind the lenses thereof, minimizing or
preventing fogging of the lenses.
Background of the Invention
Goggles, or protective eyewear or sunglasses having
tinted lenses, are advisable and commonly used in
connection with certain sports and other hazardous
activities to protect the participant's eyes. Eye
protection is especially called for when the sport or
other activity involves unshielded high-speed travel,
since traveling through the air increases the velocity of
impact on exposed surfaces of foreign matter that may be
encountered. A few examples of sporting activities where
eye protection is recommended include downhill skiing,
snowmobiling, and motorcycle racing, to keep snow, dust,
insects, rocks, etc., out of the wearer's eyes.
The problem of fogging or misting, i.e. the buildup
of condensation, on the inside surfaces of eyeglasses is
well known. The problem is particularly acute when the
wearer is warm and/or perspiring, and the environment is
cool and/or damp. The fogging of the lenses obviously
interferes with the wearer's vision, and as such is a
dangerous condition.
The prior art has long recognized the fogging
problem and proposed several solutions. For example,
the prior art has proposed thermal lenses, which consist
of a single lens of increased thickness operative to
isolate the cooler air on the outside from the warmer air
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on the inside of the glasses. The prior art has also
proposed double glass, which consists of dual lenses
separated by a layer of air, also operative to achieve
the effect of isolating the two sides of the glasses.
The thermal lenses and double glass, however, add to the
bulkiness and weight of the goggles, and thus they are
not desirable.
The prior art has also tried various coatings on the
inside surface of the glasses, either to immediately
condense or to absorb any misting on the lenses. The
water must go somewhere though, making the coatings only
effective for a limited duration, after which time the
inside of the glasses need to be emptied out or dried off
in some manner.
The most promising of solutions proposed by the
prior art include attempts to improve the air circulation
behind the goggles or eyeglasses, i.e., exhausting the
warm humid air and replacing it with cool drier air. The
prior art has proposed miniature fans powered by portable
batteries carried by the user, a needlessly complex and
costly way to resist fogging. Of greater interest, the
prior art has also proposed ventilation ports around the
perimeter of the glasses' frames, surrounding the lens.
Unless properly designed however, the ventilation ports
may provide too little air flow, resulting in
ineffectiveness or even worse in a suction effect. At
the other extreme, the ventilation ports may provide for
too great of an air flow, resulting in a pressure build
up or in uncomfortably high rewinds« across the wearer's
eyes. In addition, these ventilation ports may allow in
the foreign matter, e.g., dust, that the goggles or
eyeglasses are envisioned to guard against.
In view of the shortcomings of the prior art, it is
desirable to provide effective eyeglasses, that safely
protect a wearer's eyes and are not subject to fogging.
The eyeglasses should be low cost by being simple to
manufacture. Finally, -the eyeglasses must be lightweight
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so as not to interfere with the wearer's sporting
activities.
summary of the Invention
The present invention specifically addresses and
alleviates the above-mentioned deficiencies associated
with the prior art. Generally, the present invention
comprises eyeglasses which are resistant to fogging while
being worn during high-speed outdoor sports activities.
The resistance to fogging is accomplished by air
circulation behind the lenses, that air flow being
facilitated by venturi effects.
More particularly, the present invention comprises
eyeglasses having a frame front with middle portions over
the wearer's eyes, and endpiece portions near the
wearer's temples, the endpiece portions having an
outboard edge. Attached to the frame front are lenses
which cover the wearer's eyes. The eyeglasses, when
placed on the wearer's face, define a pair of chambers as
volumes of air between the wearer's face and the lenses,
and define gaps as the distance between the middle
portions of the frame front and the wearer's face. The
endpiece portions of the frame front each include an
aperture which defines the entrance into a ventilation
channel, for air flow through the frame and aftward
adjacent to the chamber. The air flow through the
ventilation channel undergoes acceleration of flow rate
due to the creation of a venturi configuration within the
ventilation channel.
In a preferred embodiment of the invention, the
eyeglasses include temples connected to the frame front
endpiece outboard edges. Preferably, the height of the
endpiece outboard edges of the frame are substantial, at
least half of the maximum height of the lenses.
Similarly, the butt portions of the temples, are
preferably as wide as the height of the endpiece outboard
edges to which they connect. The endpiece portions of
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the frame are preferably further enlarged to provide
space for an elongate aperture, that serves as the
entrance to the ventilation channel. The wide forward
ends of the temples help define the outboard boundary of
the ventilation channels. The shank portions of the
temples are preferably less wide, to provide for air flow
out of the ventilation channels.
The eyeglasses, resistant to fogging while being
worn, function as follows. The wearer is typically
traveling forward through relatively cool dry air at a
relatively high speed. The wearer's body, through
physical exertion, is generating heat, and the wearer's
breathing is dispelling warm humid air in the vicinity of
the goggles. In the chamber between the lenses and the
wearer's face, condensation typically begins to form on
the inside of the lenses. The cool outside air flows
through the entrances in the frame front endpiece
portions and is accelerated and flows through the
ventilation channels. The air flow through the
ventilation channels is immediately adjacent to the
volume of air in the chambers. Warm humid air in the
chambers is picked up and pulled along into the
ventilation channels, reducing the pressure in the
chambers. This pressure drop in the chambers causes cool
drier outside air to be pulled into the chambers through
the gaps. Improved ventilation, and the reduction or
elimination of fogging on the lenses, accomplished
through low cost and lightweight eyeglasses, is the
desired result.
These, as well as other advantages of the present
invention will become more apparent from the following
description and drawings. It is understood that changes
in the specific structure shown and described may be made
within the scope of the claims without departing from the
spirit of the invention.
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Brief Description of the Drawings
Figure ~ is a perspective view illustrating the
glasses of the present invention as placed on the
wearer's face;
Figure 2 is a side perspective view of the glasses
of the present invention;
Figure 3 is a side view of the ventilation channel
entrance of the glasses of the present invention; and
Figure 4 is a top section view of the ventilation
channel of the glasses of the present invention.
Detailed Description of the Preferred Embodiment
The detailed discussion set forth below in
connection with the appended drawings is intended as a
description of the presently preferred embodiments of the
invention, and is not intended to represent the only form
in which the present invention may be constructed or
utilized. The description sets forth the functions and
sequence of steps for constructing and operating the
invention in connection with the illustrated embodiments.
It is to be understood, however, that the same or
equivalent functions and sequences may be accomplished by
different embodiments that are also intended to be
encompassed within the spirit and scope of the invention.
Although the drawings show an embodiment of the
invention wherein the lenses are mounted in a spectacle-
type frame which does not seal against the user's face,
it will be appreciated that the lenses may alternatively
be mounted in a goggle-type frame which fits over the
wearer's face about the orbital regions of the skull.
The glasses of the present invention are illustrated
in Figures 1 through 4 which depict a presently preferred
embodiment of the invention. Figure 1 shows the glasses
10 as placed on the wearer's face, and the air flows
approaching toward and departing from the glasses 10.
Referring now to Figure 2, the glasses 10 may be
described in more detail. The glasses 10 are preferably
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symmetrical about a center line Y, running approximately
along the bridge of the wearer's nose. The glasses 10
are comprised of a frame front 20 having a forward side
22 and an aft side 24, and a bridge portion 26. Each
side of the frame front 10 has a middle portion 28 and an
endpiece portion 30. The glasses 10 have a pair of
lenses 35, or alternatively a single conventional lens
(not shown) could extend across the frame front 20 between
the end piece portion 30 of the frame front sides. Preferably
the frame front 20 and the lenses 35 are fabricated of a
lightweight and shatter-proof plastic material. The
lenses 35 may be transparent, darkly tinted, or of a tint
that adjusts to brightness. Specialized lenses 35 may be
used for specialized applications, e.g. night vision.
The lenses 35 are preferably held in a "sandwich"
construction between the forward and.aft sides 22 and 24
of the frame front 20 (see Figure 4). The inside edges
of the forward and aft sides 22 and 24 of the frame front
are preferably rounded, to promote a smooth air flow.
20 Alternatively, the lenses 35 could be supported only from
above or below the lenses (not shown), though such a
construction would be less structurally sound.
The endpiece portion 30 of the frame front 20 is
enlarged and has an outboard edge 32 of approximately 1
inch in height. The endpiece portion 30 of the frame 20
has material removed to form an aperture 34, more easily
seen in Figures 3 and 4. The general shape of the
glasses IO is preferably concave around the wearer's
face, providing the protection around the wearer's eyes
and promoting the smooth flow of air around the glasses
10. Importantly, note that the apertures 34 are
sufficiently outboard and aft that any debris entering
therein should pass away from the wearer's eyes.
The preferred embodiment of the glasses 10 of the
present invention further comprises a pair of temples 40,
each temple 40 having a butt portion 42, a shank portion
46, and a bent earpiece portion 44. The temples 40 are
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also preferably fabricated of a plastic material.
Alternatively, a conventional strap (not shown),
preferably fabricated of an elastic material, the strap
running around the back of the wearer's head, could be
used instead of the temples 40. The temples 40 are of
the greatest width at the butt portion 42, preferably
of
a gradually reduced width through the shank portion 46.
The temples 40 at the butt portion 42 are preferably
connected by a pivot 48 (see Figure 4) to the endpiece
outboard edge 32 of the frame front 20, allowing the
temples 40 to be folded when the glasses 10 are not in
use. The forward side 22 of the frame front 20 is
preferably substantially flush to the outboard side 41
of
the temple 40, to promote a smooth air flow around the
glasses 10. The aft side 24 of the frame front 20 is
also preferably substantially flush to the inboard side
43 of the temple 40, for reasons that will become clear
later in this discussion.
Now referring to Figures 3 and 4, the details of the
aperture 34 may be described. The aperture 34 is
operative to create a ventilation channel, the function
of which will be elaborated on in later paragraphs. The
aperture 34 is preferably of a rectangular or oval shape
approximately 3/4-inch long and 1/4-inch wide, running
vertically in the endpiece portion 30 of the frame front
20. The center line of the aperture 34 is preferably
substantially parallel to the straight-ahead line of
sight of the wearer of the glasses 10. Importantly, the
aperture 34 and each of the corners 36, on the forward
side 22 and the aft side 24 of the frame front .20, are
enlarged to define flared ends and create a venturi in
the air flow through the aperture 34. Also importantly,
the top and bottom of the endpiece portion 30 around the
aperture 34 is preferably a ramp 38, to capture a greater
quantity of air into the aperture 34 to promote the
venturi.
The term "venturi" is generally defined as a tube
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having a narrow region in the middle with flared or
widened ends. The venturi effect is the result of the
Bernoulli's Principle which says that the flow rate of
the fluid will increase and pressure will decrease in the
narrowed region of the venturi. This "venturi effect's
occurring within the narrowed region of the ventilation
channel facilitates circulation of air behind the lenses,
thereby mitigating or preventing condensation.
Now referring to Figures 1, 2, and 4, the preferred
mode of operation of the glasses 10, resistant to fogging
while being worn, may be described. The partially
enclosed volume bounded by the inboard side 43 of the
temple 40 and the side of the wearer's head defines a
ventilation channel, as was described above. Entering
air 50 flows through the aperture 34 that is the entrance
of the ventilation channel, and becomes ventilating air
52 that flows from the aperture 34 through the
ventilation channel. The smooth transition from the aft
side 24 of the frame front 20 to the inboard side 43 of
the temple 40 facilitates a smooth air flow. The
ventilating air 52 becomes the exiting air 54, egressing
from the ventilation channel both above and below the
temple 40.
The partially enclosed volume bounded by the lens 35
and the wearer's face around her eyes defines a chamber,
as was described above. The distance between the middle
portions 20 of the frame front 20 and the wearer's face
defines gaps, as was described above. Chamber air 56
adjacent to ventilating air 52 tends to get caught up in
the flow of the ventilating air 52. This lowers the
pressure in the chamber, drawing in outside air 58 around
the middle portion 28 of the frame front 20 of the
glasses 10. The exchange of the chamber air 56 for the
outside air 58 provides sufficient air circulation to
resist fogging of the inside of the lens 35.
It is understood that the glasses described herein
and shown in the drawings represents only a presently
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preferred embodiment of the invention. Indeed, various
modifications and additions may be made to the embodiment
without departing from the spirit and scope of the
invention. These modifications and additions may be
obvious to those skilled in the art and may be
implemented to adapt the present invention for use in a
variety of different applications.
