Note: Descriptions are shown in the official language in which they were submitted.
CA 02570725 2007-01-08
pRISaVJATYC )EtEFP,ECTORS 1X71TH A P)i.URALITY OF CURVEI) SURFACES
BACKGROUND
I. Field of the lnvention
This invention generally relates to li& fixture components for lighting
fixtures. In
specific embodiments, the invention relates to a reflector for usc with an
overhead light
source that includes a plurality of undulations or curves in the vertical
dimension on at least a
portion of its inner and outer surface. These undulations serve to diffuse
light that emanates
from the light source. The outer surface of the reflector also includes a
plurality of prisms
for intemal prismatic reflection.
2. Description of the Related Art
There are various reflectors available for use with overhead lighting
fixtures,
particularly for commercial, industrial, institutional and residential
lighting purposes. It is
often desirable for these reflectors to reflect light from a light source
located within the
reflector to produce even illumination of a plane. The term "reflector" has
traditionally been
used to refer to metal reflectors, which are reflectors in the true sense of
the term - in that
they reflect light incident to their exposed surface, are opaque, and are not
capable of
transmitting light. For example, some conventional reflectors provide the
desired light
distribution by featuring opaque reflective surfaces that do not transmit
rays.
in recent years, however, thc term "reflcctor" bas also been used to refer to
transparent devices that incorporate stn-ctures such as prisms, so that the
devices reflect as
well as refract light. Transparent devices without the modified surface
structures would only
refract light, and would not be useful as reflcctors_ The term "rcflector" or
"light fix#tire
CA 02570725 2007-01-08
component" is used in this patent to refer to this second type of reflector
and the
phenomenon of the reflecting that occurs, referred to as "total internal
reflection." The
principals of refraction and total internal reflection combine to mimic the
behavior of an
opaque reflector. For example, some transparent reflectors provide prismatic
reflection
through the use of 90-degree prisms or external prismatic surfaces that are a
combination of
90-degree and curved priszns. 'I'he reflection only occurs for light entering
from within a
small zone. This is illustrated by the schematic at Figure 11. As those of
ordinary skill in
the art will recognize, if a light source is larger than a particular size,
some light will pass
through the reflector because light will strike the inner surface -of the
reflector at an angle that
does not result in total internal reflection at both exterior prism faces. In
other words, outside
that zone, the light will be refracted and transm.itted rather than undergo
total internal
reflection; however, the transmitted light may be useful as uplight.
One challenge faced by designers of reflectors is that it is difficult to
create a design
that works well with many different sizes and types of lamps and lamp
positions. Such a
versatile design is typically preferred from the manufacturer's sta dpoint
because there is
less tooling involved and fewer inventory control issues. 1`his in turn may
allow the
manufacturer to offer the reilector at a reduced price, providing cost savings
to the end user.
The shape and size of a particular ref]cctor is often driven by the shapc and
size of the
light source with which it is to be used. For example, luniinaire housings
einploying linear
sources such as fluorescent lamps tend to be linear or square. Point sources
are often used in
connection witli reflectors that are surface of revolution or bell-shaped.
It lias also been found that the use of 90-degree prisms in connection with
transparent
reflectors is pdriicularly efficient for situations sueh as industrial
lighting applications.
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Ninety-degree prisms typically allow only a small percentage of light to pass
through the
reflector (although some light naturally passes through the reflector,
priniarily as a result of
originating too far off axis as described above).
Ninety degree prisms disposed on the outside surface of reflectors have been
used for
several decades. See e.g., U.S. Patent Nos. 365,974, 563,836, and 4,839,781.
The use of
such prisms is an effective optical control technique. Prisms have been
disposed vertically
on outer reflector surfaces, as well as horizontally. Additionally, in order
to enhance the
optical control, the interior surfaces of reflectors may be smooth, vertically
fluted, textured,
or stepped with interior contours to help direct light to the prism faces.
Prisms may be provided in various materials, such as glass, plastic, or
acrylic. An
acrylic prisrn approach is advantageous primarily because of its high
efficiency. The acrylic
absorbs very little light as it passes through. When light enters from within
the reflection
zone, it is reflected with significantly higher efficiency than a typical
aluminum anodized
reflector. The acrylic desiLzn naturally creates an uplight conlponent that is
often desirable as
well. Uplight reflects from the ceiling, thereby reducing the contrast between
the bright light
source and its background. This reduces the potential for glare, softens
shadows, and
generally makes for a better lighting condition. Another advantage of an
acrylic reflector is
that it glows all over. This effectively increases the size of the light
source from a glaxe
perspective.
Another factor that designers of reflectors must consider is that the size of
the light
source dictates the size of the zone into which light is reflected. In many
cases, the use of a
large light source creates a "hot spot." The light from the source is
reflected by the reflector
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CA 02570725 2007-01-08
due to total intemal prismatic reflection and dircctcd predominantly toward a
single narrow
zone below the light source, i.e., the zonc encompassing "nadir." (Similarly,
if the device
were inverted, the same phenomcnon could force the light to be directed
predominantly
toward a single, narrow zone above the light source, i.e., the zonc
encompassing "zenith.")
In both cases, this phenomenon creates an undesired "hot spot" directly below
or above the
light fixture. Even a small amount of light can result in a significant
candela spike at these
locations due to axial symmetry.
The uppermost portiozas of the reflector tends to contribute most to the hot
spot due to
that portion's proximity to the lamp and also because the uppermost portion is
curved or
"aimed inward. The result is that light that is internally reflected from
the upper portion of
the reflector is projected toward nadir.
Existing bell-shaped reflectors have a tendency to reflect or redirect light
toward the
axis of revolut7on, resulting in a disproportionately large contribution of
light at nadir relative
to directions outward and away from the axis of revolution. This causes a
spike in the
intensity distribution of the reflector, a "hot spot," which prevents even
illumination. A
reflector that creates a "hot spot" will present a light puddle, or an
undesirable bright area of
illunzination directly beneath the luminaire when compared with the entire
surface that is
being illuminated.
There have been numerous attempts to avoid the problem of hot spots, althougla
some
have been more effective than others. For example, efforts have been made to
texture the
inner surface of reflectors (for example, by sand blasting, acid etching, or
peening), but these
efforts often result in greater. manufacturing expense. They may also result
in a general
4
CA 02570725 2007-01-08
diffusion that causes a greater percentage of light to transmit through the
reflcctor body while
reducing the downlight efficiency of the luminairc.
Additional cfforts include providing "stepped" interior contours to alter the
direction
of the reflected light in the vertical dimcnsion only, bowever this method
requires more
plastic than other methods. Reflectors having such a "stepped" inner surface
were analyzed
and also found to change the direction of light, thereby increasing
sensitivity with respect to
lamp position. Designs that primarily diffuse light by sending it into a broad
vertical zone,
rather than additionally altering the direction are preferable because they
can accommodate
a broader range of lamp types and positions. Additionally, the stepped inner
surface of the
prior art reflectors includes steps only on the uppermost, inside portion of
the reflector
creating a discontinuity of appearance in the vertical direction. These steps
are not provided
over the entire interior surface of the reflector and are not present on the
outer surface,
thereby increasing the amount of plastic required to maintain a minixnum wall
thickness.
Accordingly, there remains a need in the art for a reflector that alleviates
the above-
described hot spots, while rnaxizxtizing the amount of reflected light and
mininnizing the
amount of plastic required. The improvements offered by the present inventors
help alleviate
the problems described in ways not addresscd by the prior art.
CA 02570725 2007-10-24
SUMMARY
In one aspect, the present invention provides a light fixture component
adapted
for use with an overhead lighting fixture, comprising: a curved reflector body
comprising: (a) an inner surface and an outer surface; (b) the inner surface
comprising a
plurality of concave undulating segments and the outer surface comprising a
plurality of
corresponding convex undulating segments, wherein the undulating segments on
the
inner and outer surfaces become less pronounced as they extend down the
reflector body;
and (c) the outer surface further comprising a plurality of vertically-
directed, curvilinear
prisms that define the plurality of convex undulating segments, the prisms
adapted to
provide internal prismatic reflection of light from the light source.
In another aspect, the present invention provides a light fixture component
adapted for use with an overhead lighting fixture, comprising: a curved
reflector body
comprising: (a) an inner surface; and (b) an outer surface comprising a series
of major
and minor curvilinear prisms, the curvilinear prisms defming undulating
valleys on the
outer surface between each prism; wherein the inner surface and the outer
surface of the
reflector body comprise a plurality of repeating, aligned, elliptically-curved
segments that
define the reflector body and maintain a minimum wall thickness between the
inner
surface and the undulating valleys of the outer surface.
A further aspect of the invention provides a light fixture component
comprising: a
curved body that defines a major bell-shaped contour of the light fixture
component,
wherein the major bell-shaped contour is defined by a plurality of directly
adjacent minor
contours that define elliptical segments over an inner and an outer surface of
the light
fixture component, wherein the elliptical segments lessen in pronunciation as
they extend
down the light fixture component and the outer surface comprises at least one
prism.
The reflectors of this invention are designed to receive upward-directed light
and
reflect it downward. Alternatively, other embodiments can receive downward-
directed
light and reflect it upward, or reverse the direction of light from any
direction, including
from the side. For the sake of convenience, the remainder of this patent will
focus on
embodiments
5a
CA 02570725 2007-01-08
designed to receive upward-directcd light, although it should bc understood
that the
invention is not so limited.
lt is necessary for the reflector to reflect (througb internal prismatic
reflection) and-
refract light in a maimer that distrabutes the liglit appropriately for the
intended lighting task.
Reflectors according to certain aspects of this invention include a reflector
body that is
shaped generally like an inverted, bottomless bowl with a series of 90 prisms
that are
disposed vertically forming the outside surface of the bowl. The multiple
prisms are
provided in order to limit the amount of ligbt that passes from the light
source directly
through the reflector and to reflect it appropriately through internal
prismatic reflection.
The prisms generally feature two flat sides that meet at the prism peak. The
more a
prism angle deviates from 90 , the more light is allowed to pass through the
reflector. Thus,
it is desirable that the prisms approximate, as close as possible in light of
manufacturiaag
considerations, a 90 valley and a 90 peak betwcen and for each prism with
respect to the
light source. Accordingly, the prisms are configured so that the majority of
light from the
light source undergoes total int.ernal reflection on each face of the exterior
prisms.
In order to efficiently provide uniform light distribution and diffusion below
the light
source and eliminate the "hot spot" described above, reflectors according to
certain aspects
of this invention are provided with at least an upper portion of the inner and
outer surface
comprising a plurality of undulations or curved portions in the vertical
dimension. 7fie
curved portions preferably run sequentially along, the surface (and intersect
one another) over
a substantial portion of the reflector body, with the curved portions having a
less pronounced
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CA 02570725 2007-01-08
curvature toward the lower portion of the reflector_ The curved portions are
adapted to help
diffuse light from the light source when the reflector is in use.
The curvcd portions may also be referred to as "undulations" or
"convex/concave
undulating segments." In a specific embodiment of the invention, the
undulations,
convex/concave undulating segments, or curved portions are repeating, aligned,
elliptically
curved segments that define the reflector body and maintain a minimum wall
thickness
between the inner surface of the reflector and the valleys of the major and
minor prisms.
Another way to conceptualize the invention is that the reflector body is a
curve that
defines a major bell-shaped contour of the rcflector; with the major bell-
shaped contour
defined by a series of minor contours that define elliptical segments in the
vertical dimension
over the inner and outer surface of the reflector, whcrein the elliptical
segments lessen in
depth as they extend down the reflector.
Throughout this patent and for ease of description, the curved portions,
undulations,
or convex/coneave undulating segments will simply be referred to as
"segments."
Additionally, "segments" refer to cu.rved segments or repeating, aligned,
curved segments.
These segments he]p prevent light from being reflected down and concentrated
at an area
directly beneath the fixture (the nadir) and forming a`mot spot," because they
work in
conjunction with the externally disposed prisms to diffuse the light in the
vertical dimension.
Thc segments allow thc light to be reflected downward in a variety of pitches,
depending
upon the direction and ]ocation of the incident lig.ht onto a particular
segment.
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BRTEF AESCRIPTTON OF T]3E DRAWINGS
Figure l is a top and side perspective view of one embodiment of a xeflector
of this
invention.
Figure 2 is a bottom and side pcrspective view of the reflector of Figure 1.
Figure 3 is a top plan view of the reflector of Figure 1.
Figure 4 is a side view of the reflector of Figure 1 partially in section
through a niinor
prism.
Figure 5 is a side view of the reflector of Figure 1 partially in section
through a major
prism.
Figure 6 is a top plan view of prisrns at the lower portion of the reflector
of Figure 1.
Figure 7 is a fragmentary top plan view in section taken at line 7-7 in Figure
1
through the prisms at the upper to middle portion of the reflector of Figure
1.
Figure 8 is an enlarged detail view of an undulated segment 8 from Figure 1.
Figure 9 is a side vertical section view of the lower lip of the refleetor of
Figure 1.
Figure 10 is a side verdcal section view of an enlarged detail taken at circle
10 in
Figure 2.
Figure 11 is a schematic view of light being xefracted and undergoing total
internal
reflection to effectively reflect the ligbt_
Figure 12 is a scheniatic view of light being dispersed by curved segmcnts
according
to certain aspects of this invention.
Figure 13 is a side schematic view of a reflector according to certain aspeets
of this
invention with X and Y axes and other points marked as further explained below
for review
in coiinection with Tables 1 and 2.
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Figure 14 is a schernatic view of a series of ellipses, portions of which make
up an
elliptically-shaped section in reflectors of this invention.
Figure 15 is a close-up view taken from the circle 4 in Figure 4.
Figure 16 is an enlarged detail view similar to Figure 8 of an alternate
segment.
Figure 17 is an enl.arged detail view sirnilar to Figure 8 of another
embodiment of a
segment.
DETAILED DESCRIPTION
Generally, the reflectors descnbed herein are particularly designed for use
with large
overhead light sources_ As shown in Figures 1-5, reflector 8 according to
certain aspeets of
this invention includes a reflector body 10 for use with a liglit source or
lamp (not shown).
The reflector body 10 is preferably bell-shaped and particularly resembles an
inverted
botton-Aess bowl. The reflector can be usefully described by reference to the
azimuthal
(horizontal) and vertical dimensions.
The reflector includes a series of external prisms extending down the
reflector in the
vertical dimension, the prisms resembling a saw-tooth configuration in the
azimuthal
direction. Each apex of each prism lies in the vertical direction, i.e., it
follows a line running
vertically on the reflector.
The reflector further includes curved segments or sections in the vertical
dimension,
the cuzves extending vertically down the reflector. 'Y'he inside and outer
surfaces of the
reflector undulate running vertically dovvn the reflector. Also in the
vertical direction, on the
outer surface, the prisms undulate corresponding to or aligned with the
undulations on the
inner surface. Additionally, cach individual curve or undulation establishes
an annular
trough that runs azimuthally around the iilterior of the reflector.
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CA 02570725 2007-01-08
The upper portion 12 of the reflector body 10 features an upper opening 26,
and its
lower poTtion 14 features a lower opening 28. Openings 26 and 28 are adapted
to receive a
light source and to provide an exit for the illumination in use, respectively.
The reflector
body 10 is preferably formed of a transparent material, such as plastic,
glass, or any other
material that is transparent or a transmissivc material with an index of
refraction that is
greater than that of air. In particular preferred embodiments, the reflector 8
is formed of
acrylic material.
The outer surface 18 reflects light that passes through the reflector body 10
by
including a plurality of curvilinear prisms 24 that extend vertically, along
outer surface 18
between upper opening 26 and lower opening 28. Specifically, as shown in
Figures.4-7, each
prism 24 has a substantially isosceles triangular cross section witb a peak 30
and a val]ey 32.
The angle at the peak 30 of the triangle is preferably about 90 degrees, but
may vary
between about 85 to about 95 degrees, and more specifically between about 87
to about 93
degrees. The prisrns may have small radii at peaks and valleys due to
manufacturing and
tooling liniitations. Each prism 24 also tapers in width from its valley 32 to
its peak 30_ The
majority of the light from the light source is reflected by the prisms 24 back
into reflector 8
and downwardly t}irough lower opening 28 by the principle of total internal
reflection, which
is well known to those of ordinary skill in the art. Any number and widt]t of
prisms 24 may
be provided on reflector body 10 that accommodate necessary manufacturing
considerations,
as long as outer surface 18 at least partially reflects light transmitted
through reflector body
10.
Due to The bell-shape of reflector body 8, the number of prisms 24 at the
smaller,
upper portion 12 may not equal the number of prisms at the wider, lower
portion 14. In order
CA 02570725 2007-01-08
to provide for a substantially unifontn prismatic outer surface 18, pre.ferred
embodiments of
the present inveiltion feature major and rninor prisms.
For example, as shown in Figure 4, major prisms 34 have substantially the same
depth
from lower portion 14 to upper portion 12. Interspersed between major prisms
34 are minor
prisms 36, preferably at a l_l ratio, with one minor prisz 36 between each
adjacent pair of
major prisms 34_ Minor prisms 36 start witb a depth that is comparable to that
of the major
prisms 34 at lower portion 14 that decreases as minor prisms 36 extends toward
upper
portion 12. In other words, the minor prisms 36 reduce in size untxl they
substantially
disappear prior to reaching the top of upper portion 12.
Althougb specific dimensions for certain embodiments of the prisms arc set
forth in
Tables 1 and 2 below, there is no requirement that the prisms be of a certain
depth or width.
In one embodiment, however, the minor prisms 36 have a deptli that is
substantially less than
the depth of the major prisms 34 at the upper portion 12, a depth that is
about half the depth
of the major prisms 34 toward the middle portion of the reflector, and a depth
that is about
equal to the depth of the major prisni.s 34 toward the lower portion 14 of the
reflector body
10.
In a specific cmbodiment, the number of prisms'24 on the reflector body 10 is
made
up of about half major prisms 34 and about half minor prisms 36. For example,
if there are
320 total prisms, there are about 160 major prisms 34 and about 160 minor
prisms 36.
Figure 4 is a side view of a reflector body 10 as well as a cross-sectional
view through
a nvnor prism 36. It shows that minor prism 36 enlarges in depth as it nears
the lower
portion 14_ Additionally, Figure 7 shows a top plan view of a portion taken
between about
the upper portion 12 to the middle portion of the reflector body 10 where the
depth of the
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CA 02570725 2007-01-08
minor prisms is less than the depth of the major pnsms 36. Figure 5 is a side
view of a
reflector body 10 with a cross-section view tluough a major prism 34, with the
adjacent
niinor priszxt 36 shown in dotted liDes. Figure 5 illustrates that major prism
34 can maintain
substantially the same depth throughout.
In certain embodiments, the design and shape of the contour is determined by
an
iterative method that is based upon an algorithm. The algorithm produces a
vertical contour
that yields the desired distribution for a true point light source within a
spun metal reflector.
However, the dimension of the light source is significant. Light sources used
in connection
with overhead lighting fixtures are often large and do not emit light the way
a single point
source does. Additionally, an acrylic ref7ector is optically different from a
spun metal
reflector and thus, the algozithm commonly used in the art in connection with
a spun metal
reflcctor will fail to produce the desired contour in an acrylic reflector.
Specifically, in order to account for the difference between point and arca
sources, an
iterative approach was used. A computer algorithm was developed to construct a
complete
3-dimensional geometric computer model based upon certain input parameters
relating to the
desired photometric distnbution while remaining within certain. fixed
limitations such as the
aperture size and overall reflector height. The resulting 3-dimensional
computer model was
then analyzed using a commercially available ray-tracing program and these
results were
compared to the desired distr.i.bution to establish the input paramctcrs for
each subsequent
run. Tluoug h iteration, the design was found to converge on the desired
distribution.
Genei-ally, because the critical angle for total internal reflection of
acrylic is
approximately 42-degrees in air, 90-degrcc prisms can be used on the outer
surface of
reflectors to reflect light rather than refract light, as long as the light
source is relatively small
12
CA 02570725 2007-01-08
in the lateral dimension. Note that although the vertical dimension of the
light source has
little impact on the percentage of light that undergoes total internal
reflection, it does
contribute to the creation of the hotspot deseribed previously. A source that
is larger in the
vertical dimension will have a greater probability of creating a hot spot at
nadir. Put another
way, when light is reflected to remote locations, only a small circumferential
segment of the
reflector reflectively images the souTce. However, as the light is reflected
toward nadir, the
whole circumference of the reflector reflectively images the source, and at
nadir, even a
small amount of ligbt can cause a large candela spike.
For example, the schematic shown at Figure 11 depicts total internal
reflection. The
light in the gray zone 73 will be reflected because the zone 73 defines the
boundary for total
intenial reflection. As the source grows in diameter, all light that
originates outside the zone,
e.g., at area 80, will be transmitted and all light that originates within the
zone 73 will be
reflected. Thus, the percentage of light that gets reflected vs. transmitted
is dictated by the
diameter of the source. When the light source is not a point source, but a
large ligbt source
with light emanating from an area broader than the reflecting zone, some of
the light will
contact the reflector at a less than desired angle, and light will transmit
through the reflector,
rather tlian be reflected downward.
For exarnple, the refleetor 70 is a section of circular glass or acrylic
reflector with 90-
degree prisms 72 on its exterior surface. The ligbt source 74 in the center of
the reflector 70
envts light. Specifically, light 76 enters the first surface 78, refracts a
small amount, reflects
off of the two 90-degree prism faces 72, and refracts once more when exiting
the interior
surface 78. As shown, the light is essentially reflected back in the direction
frorca which it
came in two dimensions. The behavior in the third.dimension is most similar to
that of a
i3
CA 02570725 2007-01-08
mirror. The result is that glass (which is a n.iaterial that alone, would act
as a refractor to
transmit light) behaves ]ike a inirror (within certain limits of course) by
providing internal
prismatic reflections. A. primary advantage compared to first surface
reflection using opaque
reflectors is that very little light is absorbed in the process.
However, light entering from outside the small point source zone 73, such as
]ight
originating at point 80, wi]l pass through the exterior prism 72 ratlier than
undergoing total
intemal reflection. This example illustrates the importance of properly
orienting and
precisely positioning the 90-degree prisms with respect to the light source.
As the sides of
the prism either diverge or converge relative to 90-degrees with respect to
the light source,
the gray zone 73 (the zone in which light undergoes total internal reflection)
shown in Figure
11 becomes smaller. At rouShly 84-degrees and 96-degrees, based on the
3refractive index of
acrylic, the zone diminishes and the utility of the prism is sacrificed.
Thus, in order to appropriately orient the prism to provide the most effective
dispersion of the ]igbt, reflectors S further include at least an upper
portion of the inner
suzface and outer surface that include a plurality of undulating segments 40.
One benefit of
providing the segments 40 of the present invention is that they permit only a
small amount of
the segment 40 to reflectively image light directly at nadir.
For exasnple, Figures 4 and 5 show a series of segments 40 that comprise
reflector
body 10 that are curved portions dcfining the inner surface 16 and the outer
surface 18 of the
reflcctor body 10. The concave undulating segments or curved portions will be
referred to
generally as segments 40. The sepients 40 preferably run consecutively and
vertically down
the reflector body 10. Each segrnent 40 is preferably adjacent to artother
segnient 40 over a
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CA 02570725 2007-01-08
substantial portion of the reflector body 10, with the segments 40 having a
lesser curvature
toward the lower portion of the reflector.
Segments 40 may be elliptical segments, curved segments, undulating segments,
concave un.dulating segments, arc segments, circular segments, line segments,
concave-
shaped segments, scallop-shaped segments, or partial annular undulations. The
purpose of
segments 40 is to help diffuse light in the vertical dimension from the light
source when the
reflector is in use_ Segments 40 help prevent light from being reflected
straight down and
concentrated at an area directly beneath the fixtuTe (the nadir) and formiirig
a "hot spot" by
diffusing the light in the vertical dimension. The segments 40 allow the light
to be reflected
downward in a variety of pitches, depending upon where the light hits the
particular segment.
This is illustrated schematically by Figure 12. Put another way, the segments
allow the light
to be dispersed over a broader zone for a more even, effective, and pleasing
light distnbution.
The use of segments 40 on the inner and outer surfaces is also economically
efficient because
they usc less material than other "hot spot" solutions explored to date.
Segments 40 are shown in Figures 4 and 5 and in enlarged detailed view in
Figure 8.
Segments 40 are located on the outer sur.face 18 and the inner surface 16 of
reflector body
10. They are also shown as substantially aligned with one another, to create a
substantially
unifonn wall thickness, i.e., each segment 40 on thc outer surface 18
corresponds to a
segment 40 on the iinner surface 16.
ln a particular embodiment, segments 40 are elliptical segments. ln other
words,
segments 40 define a portion of reflector body 10 that compnses a series of
small portions of
ellipses, small portions of which are manifcsted in scallop-type shaped curves
or segments 40
CA 02570725 2007-01-08
that are disposed on the reflector body 10. These elliptical or ellipsoidal
segmcnts 40 may be
described as repeatin.g, aligned, elliptically curved segments.
Figure 12 is an exaggerated schematic that shows the effect of elliptical
segments 40, and Figure 14 shows an exaggerated schematic showing elliptical
segments 40
as they are manifested on inner 16 and outer 18 surface of reflector body 10
(These
scbematics are greatly simplified versions shown for illustration only. The
prisms that are on
the outer surface of the reflector 10 are not shown for the sake of clarity,
but the prisms are
the features actually causing the light to be reflected through internal
prismatic reflection-
'1'he segments 40 are what allow the light to be diffused to various positions
below the light
source.) The segments 40 allow the light to be reflected downward in a variety
of pitches,
depending upon the location and associated angle of incidence at which the
light strikes the
particular segment 40.
In a specific embodiment of the invention, the segments 40 (whether they are
undulating segments, curved segments, elliptical segments, repeating, aligned,
elliptically
curved segments, concave undulating segments, arc segments, circular segments,
line
segments, concave-shaped seginents, scallop-shaped segments, or undulatio-os)
define the
reflector body and maintain a substantially constant wall thiclrness between
the inner surface
and each prism valley, as shown in Figures 6 and 7. This feature helps save
material costs by
reducing the amount of reflector material needed to form a reflector 8, while
maintaining a
substantially constant minimum wall thickness, which is necessary to the
integrity of the
reflector 8.
16
CA 02570725 2007-01-08
Another way to conceptualize the segments 40 of this invention is that the
reflcctor
body 10 is a curve that defines a major bel.l-shaped contour of the reflector,
with the major
bel'l-shaped contour defined by a series of minor contours or segments 40 that
define the
inner and outcr surface of the reflector, wherein the segments lessen in depth
as they extend
down the reflector. Again, however, it is preferred that the segments maintain
a
substantially constant wall thickness between inner surface and prism valleys.
As briefly mentioned, and as shown in Figures 4 and 5, it is preferable that
the
segments 40 have the highest degree of curvature or depth near the upper
portion 12 and fade
away completely or fade to almost no visible curvature toward the lower
portion 14. Figures
4 and 5 show that segments 40 appear to "flatten out" as they reach lower
portion 14.
Toward upper portion 12, scgments 40 curve outward from reflector body 10.
One theory behind the orientation of the segments 40 of this invention is that
the
upper portion 12 of inner surface 16 is a particular problem area in causing a
hot spot in a
bell-shaped style reflector. This is partially due to its proximity to the
light source and
partially because upper portion 12 is curved such that it aims toward nadir,
i.e., the light
reflected by this portion is predoniinately directed downward. Specifically,
more light is
reflected downwardly (by internal prismatic reflection) by the outer prismatic
surface 18 at
the upper portion 12 than at the lower portion 14, because the lower portion
14 is spaced
further from the light source and is generally aiming to a higher vertical
angle. Providing
curved segments 40 over at least a portion of the surface of the upper portion
12 allows light
from the light source to be dispersed more evenly, rather then being
conccntrated at the nadir
50 and forming a hot spot.
17
CA 02570725 2007-01-08
Additionally, providing segments 40 on both the inner surface 16 and the outer
surface 18 of the re#lector body 10 has been found to allow efficient light
dispersion while
requiring the least amount of material. Altematively, the segments 40 may be
included only
on the inner surface 16, as shown in Figure 16 or on the outer surface 18, as
shown in Figure
17. It is preferred, however, that the segments 40 be provided at least on the
outer surface 18
for maximum effect, although additional aligned curved segments 40 on the
inner surface 16
help save material.
The primary purpose of segments 40 is to direct the light coming fi'om the
light
source away from the nadir in a substantially conical shape around the nadir
to prevent the
light from being concentrated downwardly and creating a hot spot below the
fixture. In
addition, varying the location of the light source with respect to the
segments 40 should not
create a hot spot or a void ihat would disrupt even illumination because the
light is directed
into a much broader zone than it would ordinanly be if no segments were
present. Therefore,
precise location of the light source is not required in connection with
reflectors according to
certain embodiments of this invcntion, rninimizing sensitivity to lamp
position and
manufacturing tolerances. In fact, the present design is highly forgivin.g
with respect to lamp
positioning. Multiple light sources and multiple lamp positions can be used
while also
achieving a good distribution.
Segments 40 may extend over the entire inner surface 16 and the outer surfaee
18 as
shown by Figures 1-5, although the Figures also show that the segments 40
lessen in
curvature toward the lower portion 14. In other words, this means that the
segment 40 is
curved axaore, has a greater depth, or is a tighter curve at the upper portion
12 and is curved
less, has a shallower depth, or is a looser curve at lower portion 14. As
illustrated
18
CA 02570725 2007-01-08
schematically by Figure 14 iri connection with an elliptical segment 40, the
ellipses become
larger as they extend down the reflector body 10 so that there is a less
pronounced curve
toward lower portion 14.
Segments 40 also serve an aesthetic function in terms of obscuring the light
source
when it is viewed through the acrylic at high angles, thereby reducing the
potential for glare.
Incorporating segments 40 substantially down the reflector body 10 helps to
obscure the light
source, even as the segments lessen in curvature. The segments 40 additionally
provide a
way to compensate for shortconiangs in the distribution resulting frorn the
exterzaal prism
contours alone.
Alternatively, rather than providing segments 40 that extend over most of
reflector
body 10, segments 40 may only be included at upper portion 12 of reflector
body 10. This
embodiment will still provide many of the advantages described above because,
as
mentioned, the upper portion 12 is a particular problem area in causing a hot
spot due to its
proximity to the ligbt source and because it is curved to aim toward nadir.
Segments 40 may take on any dirxaensions.as long as they provide the effect of
light
dispersion. As shown in Figure 1, segments 40 may take the form of individual
curved bands
that encircle or form reflector body 10 in the lateral or azimuthal direction.
The segments 40
are vertical contours that are not frusto-conica] or frusto-toroidal segments.
ltather, on the
inner surface, they are single, continuous curved bands that extend around the
reflector body
10. On the outer surface, the segments 40 help define undulating prisms. In a
specific
embodiment, the diniensions of each curved band include a portion of an
ellipse.
Alternatively, the dimcnsions of each curved band rescmble a slight scallop.
19
CA 02570725 2007-01-08
Examples of elliptical segment 40 dimensions for very specific embodiments are
provided in Tables I and 2, altliough these dimensions are provided as
examples only and are
not intended to be limiting in any way. The Tables are provided in order to
show one way
that the size and shape of the ellipses can be calculated. The values provided
in Tables I and
2 below define full ellipses, although very small portions of each ellipse
make up each
segment 40. It is emphasized that the Tables are provided only as possi`ble
examples of
embodirnezlts and sets of dimensions that can be used to manufacture a
reflector with
elliptical segments 40. It sbould be understood that any dimensions defining
an arc, a curve,
an ellipse or any other segment are considered within the scope of this
invention.
The ellipse centers are defined in X and Y dimensions from the origin, as
shown on
Figure 13. The major and minor axis dimensions of the ellipses are provided
and the
arientation of the major axis is measured with respect to the positive X axis.
The angle 0 on
Figure 13 coixesponds to the angle between the X axis and the major ellipse
axis, measuring
eounterclockwise as positive. Each table defines either a major prism contour,
minor prism
contour, or inner surface contour. The point 0,0 is the drawing origin.
(Although Tables 1 and 2 include dimensions for Inl (inner surface) and In2,
they are
not shown on Figure 13 because they would extend off of the page because the
ellipses they
define are so large.)
TABLE I
Jnner Surface EAit+tieal Sections
Center
Segmcnt # x Y~ Major Axis Minor Axis Major Axis
l.ength (A) Length (B) Orientation 9
lnl -81.1532 -12.4951 188.4074 169.5667 8.8792
CA 02570725 2007-01-08
In2 -26.3581 -4.7243 77.7934 70.1041 ~~- 123888
In3 -9.6666 -0.8722 43.5372 39.1835 15.7585
1n4 -2.2862 1.7813 27.8707 25.0836 19.0276
In5 1.4877 3.8193 ' 19.3787 17.4408 222869
In6 ` 3.5402 ~ 5.4854 14.2845 12.8561 25.5337
In7 4.6588 6.8981 11.0142 9.9128 28.7602
In8 5.2220 8.1230 8.8136 7.9322 31.9720
In9 5.4314 9.2017 7.2814 6.5533 35.1716
1n10 5.4038 10.1632 6.1841 55657 38.3701
Inll 5.2088 11.0230 5.3866 4.8480 41.6592
InI2 5.0471 11.9403 4.3766 3.9389 44.7552
Main Prism Ridgc Elliptical Sections
Center
Segment # x Y Major Axis Minor Axis Major Axis
Lcngtb (A) l.ength (B) Orien#ation (O
Ma1 -82.2784 -12.5298 191.0852 171.9767 8.7961
Ma2 -26.7427 -4.7349 79.0069 71.1062 12.2811
Ma3 -9.8040 -0.8651 44.2524 39.8272 15.6373
Ma4 -2.3093 1.8010 28.3616 25.5255 18.9043
Ma5 1.5278 3.8506 19.7453 17.7708 22.1712
Ma6 3.6200 5.5281 14.5718 13.1146 25.4374
Ma7 4.7641 6.9518 11.2483 10.1234 28.6952
Ma8 5.3437 8.1871 9.0099 8.1089 31.9502
Ma9 5.5634 9.2756 7.4496 - 6.7046 35.2051
MalO 5.5398 10.2449 63346 5.7011 38.4694
Mall 5.3448 11.1107 5.5255 4.9730 41.8374
Ma12 4.9577 11.8388 5.0925 4.5833 45.2526
21
CA 02570725 2007-01-08
Minor Prism Ridge Flliptical Scctions
center
Scgment # X Y Major Axis Minor Axis Major Axis
Length (A) Length (B) Orientation O
Mi 1 -82.0874 -13.0688 190.8605 171.7744 9.1330
Mi2 -26.7301 -5.0460 79.0709 71.1638 12.7270
Mi3 .9.7695 -1.0682 44.2350 39.8115 16.1721
Mii4 -2.2760 1.6592 28.3032 25.4729 19.5026
Mi5 1.5513 3.7461 19.6663 17.6997 22.8097
Mi6 3.6307 5.4469 14.4818 13.0336 26.0901
Mi7 4.7612 6.8848 11.1524 10.0371 29.3347
Mi8 5.3276 8.3277 8.9122 8.0210 32.5491
Mi9 5.5354 9.2195 7.3525 6.6173 35.7336
Mi10 5.5025 10.1895 6.2385 5.6147 38.9004
Mill 5.3000 11.0543 5.4320 4.8888 42.1409
Mi12 4.9963 11.8622 4.7644 4.2879 45.2590
TABLE 2
Inner Surface Blliptical Sections
Center
Segment X X Major Axis Minor Axis Major Axk
Length (A) Length (B Oritntation 6
Inl -79.2400 -8.3328 180.7433 162,6690 6.6229
1n2 -25.7015 -3.0801 73.2500 65.9250 10.5653
In3 -9.3888 0.0598 40.0339 36.0305 14.3284
In4 .2.2400 2.3579 25.0265 22.5239 18.1037
In5 1.39Q5 -4.1898 16.9584 15.2625 21.8998
22
CA 02570725 2007-01-08
In6 3.3506 5.7122 12.1519 10.9367 25.7066
In7 4.4094 7.0082 9.0843 8.1759 29.5045
In8 4.9374 8.1263 7.0279 6.3252 33.2954
In9 5.1323 9.0997 5.5975 5.0377 37.0821
In 10 5.1078 9.9520 4.5734 4.1160 40.8726
Inll 4.9352 10.7040 3.8157 3.4342 44.6535
1n12 4.8169 11.5164 2.8131 2.5318 48.1923
Main Prism Ridge Elliptical Sections
Center
Segmcent ~t X Y Major Axis Minor Axis Major Axis
Length (A) Length (B) Orientation (
Mal -80.4929 -8.3786 183.6565 165.2909 6.5617
Ma2 -26.1075 -3.0954 74.4716 67.0244 10.4729
Ma3 -9.5457 0.0586 40.7611 36.6850 14.2160
Ma4 -2.2815 2.3684 25.5263 22.9737 17.9823
Ma5 1.4149 4.2121 17.3280 15.5952 21.7821
Ma6 3.4166 5.7470 12.4379 11.1941 25.6043
Ma7 4.5024 7.0553 9.3128 8.3815 29.4323
Ma8 5.0477 8.1854 7.2154 6.4939 33.2671
Ma9 5.2533 9.1702 5.7545 5.1790 37.1115
Ma10 5.2344 10.0332 4.7067 4.2360 40.9719
Mall 5.0611 10.7928 3.9365 3.5428 44.8310
Ma12 4.7383 11.4207 3.4717 3.1245 ~'- 48.8377
Minor Prism R.idge Elliptical Scctions
(:cntcr `= --=---- . ...~....~..._._
Scgmcnt # Y Major Axis Minor A~cis Major Axis
Length (A) Length (13) Orientation
23
CA 02570725 2007-01-08
Mil -80.3657 -8.7666 183.4841 165.1357 6.8108
Mi2 -26.1146 -3.3491 74.5521 67.0969 10.8536
Mi3 -9.5216 -0.1137 40.7517 36.6765 14.7056
Mi4 -2.2537 2.2459 25.4779 22.9301 18.5562
Mi5 1.4369 4.1224 17.2580 15.5322 22.4130
Mi6 3.4281 5.6783 12.3563 11.1206 26.2644
Mi7 4.5017 6.9997 9.2254 8.3029 30.0870
M18 5.0347 8.1366 7.1270 6.4143 33.8829
Mi9 5.2292 9.1235 5.6676 5.1009 37.6562
= MilO 5.2012 9.9853 4.6238 4.1614 41.4120
Mill 5.0216 10.7424 3.8573 3.4716 45.1340
1vi12 4.7690 11.4424 3.1896 2.8706 48.7496
Figures 4 and 5 also show that both niajor 34 and minor 36 prisms 'Mclude an
undulating, curved, or elliptical shape as they extend vertically down
reflector body 10. This
is also shown in inore detail by Figure 8.
Reflector 10 fw-ther includes a lower lip 20 at lower portion 14. Lower lip 20
is
disposed at lower portion end 14 and extends substantially around lower
portion and defines
lower opening 28. Lower lip 20 has planar upper and lower surfaces and a
curved annular
outer surface. At various portions, lower lip 20 features indentations 44 in
upper surface 21.
Indentations 44 are provided in order to receive a safety lens made of glass
or plastic or a
locking door for latching purposes. (For example, the door may enclose the
light source for
safety purposes.) As shown by Figure 3, there are preferably three sets of
indentations 44
located at approximately 120 degrees around lower lip 20.
24
CA 02570725 2007-01-08
In use, the reflector 8 and light source in combination create illumination
that extends
radially outward of the light source and axially downwardly. The illumination
that extends
downwardly from the lamp escapes tluough the reflector body's lower opening
28. The
illumination escaping from the ligltt source and extending radially outwardly
will be
intercepted by a prism 24 on the rcflector body 10 so that the majority of
light is reflected by
total intemal prismatic reflection back inside the reflector and downwardly,
although some
remaining light may be transrnitted outwardly. The majority of the light will
be scattered
inwardly by the segments 40. Light will pass througb the segments 40, be
intercepted by a
prism, and reflected. by internal prismatic reflection downwardly and
transmitted
downwardly by the prisms 24 on the outer surface 18 adjacent the segments 40.
In a specific preferred embodiment, the dimensions of the reflector inay be as
follows:
Possible Ranges More preferred Specific ranges Specific ranges
ranges for one for alternate
embodiment embodiment
Depth about ] 2 to 16 About 13 to 15 13.4 inches 14.89 inches
inches incbes
Upper Opening about 8 to 11 About 9 to 10 9.7 inches 9.7 inches
inches inches
Lower Opening about 21 to 26 About 22 to 25 22.8 inches 25.8 inches
inches inches
Yri a particular embodiment of reflector 8, the uppermost portion 46 is not
curved, but
is straight and sloped. Although uppermost port.ion 46 is shown as a
substanlially continuous
slope in Figure 1, the uppermost portion 46 of alternate reflector embodiments
may include a
collar that may include various altemate collar geometries or the upperrnost
portion itself
may comprise different gcometry, such as L-shaped, Z-sbaped, or an extended
collar shape.
CA 02570725 2007-01-08
Moreover, any number of collar configurations could be used to mount the
reflector.
As those of ord'uiary skill in the art would realize, collars, if provided,
could be any shape
and constructed of either specular (minor-like), diffuse (dispersing, similar
to the effect of
tissue paper) materials, or anywhere bctween, i.e. semi-spccular or serni-
diffuse. All
materials fall somewhere between the two extreznes.
Those skilled in the art will understand the advantages and disadvantages of
providing
collars with various reflector designs described herein. Briefly, in some
embodiments, a
collar is provided in order to gain a greater range in the positioning of the
lamp. However, it
is not required that the reflector 8 be used in connection with a collar. One
disadvantage of
providing a collar is that the upwardly-directed light is focused even more
precisely and
narrowly at nadir when it is directed downward. The segments 40 of the present
invention
help alleviate these problems, even when the reflector is used in con.nection -
with a collar.
As mentioned, the most versatile reflector solution is one that significantly
difuses all
light from the upper section of the optic. The diffusion created by the
segments 40 of the
present invention is prima.rily in the vertical dimension. Different segment
depths can alter
the degree of diffusion that results. It is preferable to provide more
diffusion near the upper
portion 12 of the reflector body 10 than at the lower portion 14.
Additionally, however, from
an aesthetic stan'dpoint, it is desirable to provide segments 40 the from the
upper portion 12
to the lower portion 14 in order to provide lamp obscuration. It is
particularly preferred to
provide a iarger or maximum segment 40 depth at the upper portion 12. Each
subsequent
segment 40 traversing down the reflector body, becomes increasingly less
pronounced untxl
the segment 40 depths reach essentially zero at lower opening 28.
nT1.13801 141637m 26
CA 02570725 2007-01-08
In order to determine segment 40 depths, the inventors applied a linear
function,
allowing them to enter a single maximum depth and calculate the remaining
segment 40
depths from this value. 1n ceriain embodiments, segments having too great a
depth can cause
more light to be reflected back onto the lamp, thereby reducing the efficiency
of the fixture,
whereas too little depth in the segments 40 results in the "hot spot" problem.
An optimally-
designed reflector 8 will strike a balance betwecn segnient 40 depths,
numbers, and sizes.
When the segments 40 are located only on the inside of the reflector, the
diffusion
effect is somewhat counterbalanced because the ligbt bas to pass tlarough the
segment 40
twice. The result is that the work that the first segment 40 did to diffuse
the light going in is
counteracted to some degree when the light exits. Accordingly, in particularly
preferred
embodiments, both the inside and the outside surface of the reflector include
segments 40.
The exterior segment 40 also helps to disperse light that passes through the
reflector
body 10 in the vextical dimension. This results in the brightness of the
lurninaire being well-
dispersed vertically over the optic when being viewed from the exterior. A
design with
segments 40 along the entire surface, and particularly, on the outside
surface, is more
forgiving in terms of providing a broader range of usable light distnbutions
through various
lamp types and positions. While not wishing to be bound to any theory, the
inventors believe
that the diffusing approach tends to be less specific than onc that also
changes the direction
of light travel. Providing segments on the inner surface as well as the outer
surface also uses
less material than the above-described stepped configuration designs currently
available.
Thus, the outwardly curved or undulatin.g segments of this invention achieve
optimal
light dispersion. With respect to the optical benefit, it is important to
understand that it is the
proportion of segment depth to length that is c.ritical. For instance, a
segment having the
27
CA 02570725 2007-01-08
same proportion will behave similarly independent of scale. The maximum
segment depth-
to-length ratio investigated ranged from about 0.02 to about 0.08, and
particularly 0.04.
Prcferably, segment 40 depth to length ratios are 0.05, and even more
preferably .06 or
slightly less than 0.06.
These are the depth to and length ratios that are provided at the deepest
curved
segment near the top. As discussed, the algorithm used can create
progressively shallower
curved segments as they extend toward the lower portion 14. However, these
examples are
provided for reference only. Optically, the segments can be scaled to any size
that is
appropriate for tbe size of the reflector. In general, shorter segments with
the same depth
will have greater dispersing potential than a segment of the same depth that
extends over a
greater area.
In summary, the degree to which the curved or undulating segments are
pronounced
can be subtle. It exists on both the i.nterior and eaterior surface, although
alternatively, it
may exist only on the outer surface of the reflector in some embodiments.
However,
applying curved segments to both sides of the reflector provides the above-
descnbed
advantages of reducing material required to construct the reflector.
While particular embodiments have been chosen to illustrate the invention, it
will be
understood by those skilled in the art that various changes and modifications
can be made
therein without departing from the scope of the invention as defined in the
claims_
28
