Reflective sheeting material

The invention provides a reflective sheeting material having a structured reflective surface having a linear ray of isosceles prism reflecting elements, each element including a pair of reflective surfaces at an angle of about 120.degree. therebetween. The invention also provides a reflective sheeting material having a structured reflective surface comprising an array of reflecting elements, each comprising a polyhedron having three paralellogram faces. The invention also provides an apparatus such as a light pole for transporting light and reflecting the light in a broad, uniform pattern. The apparatus comprises (a) a columnar light conduit, for transporting light therealong, the conduit having a proximate end and a distal end; (b) a light source provided at the proximate end of the light conduit,and (c) a light distributing reflective member, such as the reflective sheeting material described above, comprising a multiplicity of repeating reflecting elements. The reflective member is positioned at the distal end of the light conduit so that the light exiting the distal end of the conduit is reflected in a broad, uniformly distributed pattern.

TECHNICAL FIELD 
The present invention is directed to an apparatus for transporting and 
reflecting light, particularly to a light pole adapted to reflect light in 
a broad, uniformly distributed pattern. The present invention is also 
directed to a reflective sheeting material for use in an apparatus for 
transporting and reflecting light. 
BACKGROUND OF THE INVENTION 
The illumination of roadways, parking lots, outdoor sports facilities, and 
the like, is typically accomplished by means of directed light sources 
suspended at the top of tall poles. For example, light poles are commonly 
found uniformly positioned along city streets and highways. 
A light pole typically includes a light source suspended at the top of a 
tall pole, typically 15 to 18 meters above the ground. A light is 
typically encased in a fixture having reflective and/or refractive 
portions used to direct the light to the ground below in a desired 
pattern. The fixture may also include a transformer or ballast, wiring, 
and other components necessary to provide a bright directed source of 
light at the top of a pole. The light and fixture typically are very 
heavy. Accordingly, to suspend the light and the light fixture, a heavy 
pole, typically made of a heavy gauge metal, is required. 
Light poles are positioned at uniform intervals, for example, along a 
highway or other roadway. The brightness of the light source, the 
characteristics of the reflectors and/or refractors contained in the 
fixture, the height that the light source is positioned above the ground, 
and the distance between adjacent light poles, all contribute to the 
intensity and pattern of the light illuminating the ground or other 
surface surrounding the pole. The uniformity of the light illuminating the 
ground is quantified by the ratio of illumination, defined as the ratio 
between the brightest spot and the darkest spot. A 7:1 ratio of 
illumination is considered fairly uniform, while ratios of 100-1000:1 are 
not uncommon. A ratio of illumination of less than 3:1 would be highly 
desirable. 
Standard light poles, having a directed light source suspended a the 
ground, present problems involving cost, maintenance, and safety. Because 
of the materials required to suspend the heavy light and fixture above the 
ground, the cost of such light poles can be significant. Maintenance of 
such light poles is also costly and time consuming. To change a light bulb 
in a suspended light fixture, it is necessary to use a lifting device, 
such as a telescoping man lift or hoist, attached to a highway maintenance 
vehicle. In addition to the cost of the two or three persons necessary to 
operate the lift truck, the presence of such a vehicle on the side of a 
roadway can be dangerous, both to the maintenance personnel and to the 
motorist. The presence of the poles themselves along a roadway also 
presents the danger of the pole being struck by a motorist. Because such 
poles are typically heavy gauge metal, the impact with such a pole can 
have severe consequences. In addition, the heavy light fixture and the 
heavy metal pole, present a significant danger in falling subsequent to 
impact by a vehicle. 
In a different technical field, light conduits capable of transmitting 
large quantities of light energy from one place to another are known. Such 
light transmitting conduits are useful in a wide variety of applications, 
for example, in transmitting sunlight from outdoors into the interior of a 
room. Such light conduits typically operate on the principle of total 
internal reflection, having a plurality of 45.degree. angle prisms 
extending the length of the conduit to totally internally reflect the 
light as it travels along the length of the conduit. See, for example, 
U.S. Pat. Nos. 4,260,220; 4,805,984; 4,750,789; and 4,615,579. 
In view of the disadvantages inherent in the presently known light poles, 
there is a need for an apparatus that transports light from a light source 
that can be located at or near ground level upward to a reflecting member, 
that distributes the light uniformly to the ground below. There is also a 
need for a reflective sheeting material that may, for example, be provided 
in a reflection chamber adapted to be provided at the top of a light 
conduit to reflect an area source of light emitted from the light conduit 
in a broad, uniformly distributed pattern. 
SUMMARY OF THE INVENTION 
The present invention provides a reflective sheeting material having a 
structured, reflective surface comprising a linear array of isosceles 
prism reflecting elements, the elements including a pair of reflective 
surfaces having an angle of about 120.degree. therebetween. Each 
reflecting surface also forms a reflective groove with an adjacent 
reflective surface, the surfaces of the groove having an angle of about 
120.degree. therebetween. 
The present invention also provides a reflective sheeting material having a 
structured reflective surface comprising an array of reflecting elements 
comprising a polyhedron having three parallelogram faces. The elements are 
shaped and arranged so that the following conditions exist: (a) the faces 
intersect at three external lines of intersection and at an element apex 
(b) each face also intersects with adjacent faces on two adjacent 
elements; (c) the three faces on three adjacent elements intersect along 
three internal lines of intersection forming a reflection valley; and (d) 
in use, a ray of incident light entering a valley strikes a face at an 
angle of about 33.degree.-37.degree. and reflects from the face 
approximately parallel to the other two faces and at an angle of about 
67.degree.-74.degree. from the incident light. 
The present invention also provides an apparatus, such as a light pole, for 
transporting light and reflecting the light in a broad, uniform pattern. 
The apparatus comprises (a) a columnar light conduit, for transporting 
light therealong, the conduit having a proximate end and a distal end; (b) 
a light source provided at the proximate end of the light conduit; and (c) 
a light distributing reflective member, such as the reflective sheeting 
material described above, comprising an array of repeating reflecting 
elements. The reflective member is positioned at the distal end of the 
light conduit so that the light exiting the distal end of the conduit is 
reflected in a broad, uniformly distributed pattern. 
The present invention also provides a reflection chamber adapted to reflect 
an area source of light, such as from a light conduit, in a broad, 
uniformly distributed pattern. The reflection chamber comprises (a) a 
light inlet; (b) a reflecting member including a reflective sheeting 
material, such as those described above; and (c) at least one transparent 
wall portion to allow the reflected light to exit the reflection chamber.

DETAILED DESCRIPTION OF THE PRESENT INVENTION 
Referring to FIG. 1, a reflective sheeting material 10 is shown having a 
linear array of reflecting elements 12. The elements 12 each include a 
pair of reflective surfaces 14, each reflective surface 14 forming a 
reflective groove 16 with an adjacent reflective surface 14. 
Referring to FIG. 2, a cross-section of a reflective sheeting material 20 
is shown. The sheeting material 20 includes reflective elements 22 each 
having reflective surfaces 24. The reflective surfaces 24 form a 
reflective groove 26 therebetween. The angle between reflective surfaces 
24 is "A." An incident ray 27 normal to the plane of the sheet material 20 
strikes a reflective surface 24 and is reflected along reflected ray 28 
parallel to the adjacent surface 24, at an angle "B" with the incident ray 
27, and at an angle "C" with the plane of the sheet material 20'. 
Referring to FIG. 3A, a reflective member 30 is shown having reflective 
sheeting portions 32, 34, 36, and 38. The reflective sheeting portions 
each contain a plurality of reflective grooves 40. 
Referring to FIG. 3B, a reflective member 45 is shown having reflective 
sheeting portions 46, 48, 50, and 52. The reflective sheeting portions 46, 
48, 50, and 52 include a plurality of reflective grooves 54. 
Referring to FIG. 4, a reflective member 60 is shown. The footprint 
portions 62 represent light reflected from the reflective member 60. 
Referring to FIG. 5, a reflective member 70 is shown. The footprint 72 
represents the light reflected from the reflective member 70 with the 
light passing through a diffuser. 
Referring to FIG. 6, a reflective sheeting material 80 is shown. The 
sheeting material 80 includes a plurality of reflecting elements 82, each 
comprising faces 84, 84' and 84". Faces 84, 84', 84" intersect along 
external lines of intersection 86, 86', 86", the lines of intersection 
intersecting at an element apex 88. Faces 84, 84', 84" of three adjacent 
reflecting elements intersect each other along three internal lines of 
intersection 90, 90', 90", forming reflection valleys 92. 
Referring to FIGS. 7 and 8, in use, a ray of incident light 100 strikes a 
reflective face 84, 84', or 84" and is reflected along a reflected ray 
102. The face 84 is at an angle .alpha. with the plane of the reflective 
sheeting material 104. The reflected ray 102 is reflected at an angle 
.beta. with the plane of reflective sheeting material 104. 
Referring to FIG. 9, a pole light 120 is shown. The light pole 120 includes 
a columnar light conduit 122, a light source 124, and a reflection chamber 
126. The reflection chamber 126 includes a light inlet 128, a reflecting 
member 130, sidewall portions 132, and bottom wall portions 134. The 
reflecting member 130 includes a plurality of reflecting elements 136. The 
columnar light conduit 122 includes a distal end 138, a proximate end 140, 
and a light transporting sheeting material 142. The light source 124 
includes a light bulb 144. The light source 124 and the proximate end 140 
of the conduit 122 is provided in a base portion 150. The base portion 150 
includes an access box 152, having a door 153 and an access opening 154. 
Reflective Sheeting Material 
The reflective sheeting materials of the present invention are configured 
to reflect light in a broad, uniform pattern. The present invention 
provides two types of reflective sheeting material, one including a linear 
array of isosceles prism reflecting elements, and the second including an 
array of reflecting polyhedron elements, each having three parallelogram 
faces. 
The isosceles prism reflecting elements form an angle of about 30.degree. 
with the plane of the sheeting material. Thus, a ray of light will be 
reflected at an angle of 30.degree. to the horizontal, and parallel to the 
adjacent face of an adjacent element. 
The reflective sheeting material having polyhedron reflecting elements 
includes an array of reflection valleys formed by three faces of adjacent 
elements. A ray of incident light strikes a face of a reflection valley at 
an angle of about 33.degree.-37.degree., and reflects from the face 
approximately parallel to the other two faces, and at an angle of about 
67.degree.-74.degree. from the incident light. Thus, the reflected ray is 
reflected at an angle of about 16.degree.-23.degree. below the horizontal. 
The polyhedron sheeting material preferably comprises elements each having 
three rhombus faces and being shaped and arranged so that the following 
conditions exist: 
(a) the faces intersect at three external lines of intersection and at an 
element apex; 
(b) the external lines of intersection each intersect at the apex at equal 
angles; 
(c) each rhombus face also intersects with adjacent faces on two adjacent 
elements; 
(d) the three rhombus faces of three adjacent elements intersect along 
three internal lines of intersection forming a reflection valley; 
(e) each rhombus face forms an angle, alpha, with the plane of the sheet 
material, alpha being about 33.degree.-37.degree.; 
(f) in use, a ray of incident light normal to the plane of the sheet 
material reflects from one of the three faces of a valley approximately 
parallel to the other two faces of the valley; and 
(g) the angle, beta, between a ray of reflected normal incident light and 
the plane of the sheet material is about 16.degree.-23.degree.. 
It is preferred that the angle o be about 35.degree.-36.degree., and that 
.beta. be about 19.degree.-20.degree.. It is also preferred that the 
sheeting material have an effective aperture of about 100%. When 
.alpha.=35.3.degree. and .beta.=19.5.degree. the reflective sheeting 
material exhibits 100.0% aperture to normal rays. Typically in use, the 
angle .beta. is the angle below the horizontal at which the light is 
reflected. A typical light pole will transport light in a path 
perpendicular to the ground. The plane of the reflective sheeting material 
is thus positioned so as to be approximately parallel to the ground. Light 
is reflected from the sheeting material back towards the ground at an 
angle .beta. below the horizontal plane of the sheeting material. The 
smaller the angle (.beta.) below the horizontal at which the light is 
reflected, the further the light can be spread from the pole. 
The reflective sheeting material of the present invention may be made from 
any suitable material. The structured reflective surface of the sheeting 
material is made from a suitable reflective material. Thus, the entire 
reflective material can be formed from aluminum or steel, that can be 
polished to provide a structured reflective surface. However, it is 
preferred that the reflective material be formed from a plastic material 
having a structured surface of the desired shape, with the structured 
surface metalized, such as vapor coated aluminum, to provide the 
reflective surface. 
A suitable plastic material for forming the reflective sheeting material is 
preferably dimensionally stable, durable, weatherable, and readily 
formable into the desired configuration. Examples of suitable materials 
include acrylics, such as Plexiglass resin from Rohm and Haas; 
polycarbonates; polyethylene based ionomers, commercially available as 
"Surlyn", from E.I. DuPont de Nemours & Co.; polyesters; and cellulose 
acetate butyrates. The polymer may be clear or opaque as light is not 
transmitted therethrough, but is reflected from the reflectorized 
structured surface. 
The reflective sheeting material may be prepared in a variety of ways 
including embossing, casting, stamping, or by other means of forming 
materials, in or with a transparent plastic material. After the structured 
surface has been formed in one planar surface of a plastic or other 
material, the surface can be metalized utilizing, a number of suitable 
metals, such as aluminum. 
Reflection Chamber 
The reflective sheeting material of the present invention is preferably 
provided in a reflection chamber adapted to be placed at the top of a 
light conduit to reflect an area source of light, emitted from the top of 
the light conduit, into a broad, uniformly distributed pattern. The 
reflection chamber may be designed in a wide variety of configurations to 
provide the desired footprint or pattern of light reflected onto the 
ground or other surface below the light pole. The reflective sheeting 
material is placed opposite the distal end of the light conduit with the 
structured reflective surface facing the light conduit so that the light 
exiting the light conduit is reflected in a broad, uniformly distributed 
pattern. 
The reflecting member includes one or more portions of a reflective 
sheeting material arranged so as to reflect light into a desired 
footprint. For example, as shown in FIGS. 3A and 3B, the reflecting member 
may include four portions with the grooves of each portion aligned in a 
non-linear relation. 
The reflection chamber also includes a light inlet adapted to engage the 
distal end of the light conduit and provide an opening into the reflection 
chamber to allow the area source of light being emitted from the distal 
end of the light conduit to radiate into the reflection chamber. The 
reflection chamber includes at least one transparent wall portion to allow 
the reflected light to exit the reflection chamber. The reflection chamber 
may be circular, square, triangular, hexagonal, octagonal, or any of a 
number of other shapes as desired. Thus, a wall portion may be a sidewall 
portion, a bottom wall portion, or other portion of the reflection 
chamber. For example, a wall portion may be a portion of the circumference 
of a circle or other shape. For example, if the light pole were designed 
to be used in a parking lot where g was to be reflected in all directions, 
the reflection chamber could be designed to have transparent walls on all 
sides. 
The reflection chamber may also include one or more planar reflector wall 
portions for directing light in a desired direction. For example, for use 
along a roadway it is desirable to reflect the light being reflected from 
the reflecting member towards the roadway and not behind the light pole or 
along the side of the roadway. Thus, planar reflection surfaces may be 
provided so as to reflect light in a given direction. 
In addition, diffusing wall panels may be provided to diffuse the light 
reflected from the reflective member into a more uniformly distributed 
pattern on the ground below (FIG. 5). These and other methods of 
reflecting and refracting light into desired patterns may be utilized in 
the reflection chamber to provide the desired footprint of light reflected 
from the reflective member. 
Light Conduit 
Totally internally reflecting conduits for transporting light from one 
place to another are known in the art. U.S. Pat. No. 4,805,984 (the '984 
patent) describes such a light conduit and is incorporated herein by 
reference. See also, U.S. Pat. Nos. 4,615,579 and 4,750,798. 
In use, a light conduit transports light from a light source, including 
both artificial or solar energy, and transports the light from one end of 
the conduit to the other. Light conduits, such as those described in the 
'984 patent, can transport light with very little loss of light. In 
addition, the light provided at the distal end of a conduit, such as that 
described in the '984 patent, is a linearly directed (semicolumnated) area 
source of light. An area source of light is made up of a large number of 
point sources of light. Thus, a single light bulb or multiple light bulbs 
at the proximate end of the light conduit will provide an integrated area 
source of light at the distal end of the conduit. The integrated area 
source is then reflected by the array of reflecting elements into a broad, 
uniformly distributed pattern. 
Although there are a number of configurations of light conduits known in 
the art, light conduits such as those described in the '984 patent are 
preferred. A preferred light conduit will comprise a wall member of a 
transparent material, including a structured surface on one side and a 
smooth surface opposite the structured surface. At least a portion of the 
cross-section of the wall member lying in a smooth arcuate curve. For 
example, the wall member may have a substantially circular cross-section 
with the smooth surface disposed on the inner side of the wall member and 
the structured surface on the outside of the wall member. The structured 
surface includes a linear array of substantially right angled isosceles 
prisms arranged side-by-side, with the perpendicular sides of the prisms 
making an angle of approximately 45.degree. with the tangent to the smooth 
surface opposite the structured surface. The prisms typically run parallel 
to the axis of the wall member extending continuously from one end to the 
other. In use, a predetermined portion of the light entering the light 
conduit within an acceptable angular range, is contained by total internal 
reflection as it travels along from the proximate end to the distal end of 
the light conduit. 
Light Pole 
The present invention also provides an apparatus for transporting light and 
reflecting the light in a broad, uniform pattern. Such an apparatus may be 
used as, for example, a light pole positioned along a roadway, highway, or 
a parking lot. A light pole will include a light source typically provided 
in a base portion. The base portion is adapted to be positioned either 
submerged in, or on top of, the ground. A columnar light conduit, such as 
that described in the '984 patent, extends from the base portion, 
typically positioned so as to extend vertically from the ground. It is 
preferable that the base portion include an accessible box portion for 
ease of access to the light source. The light source may include one or 
more light bulbs or other sources of light. Thus, the light bulb or bulbs 
may be easily replaced by one person, without the need for ladders, 
hoists, or other apparatus typically required to change a bulb positioned 
on top of a light pole. 
The light emitted from the light source at the base or proximate end of the 
light conduit is transported through the light conduit and is provided as 
an area source of light at the distal end of the light conduit. The light 
could also be located elsewhere in the light conduit, as desired, and 
proximate end, as used herein, will refer to the end of that portion of 
light conduit where the light source is located. 
A light distributing reflective member comprising an array of repeating 
reflective elements is positioned at the distal end of the light conduit 
so that the light exiting the distal end of the conduit is reflected in a 
broad, uniformly distributed pattern. Examples of light distributing 
reflective members include the reflective sheet materials described 
herein. The reflective member may comprise two or more linear arrays of 
reflecting elements disposed in different linear relation to reflect the 
light into a particular uniformly distributed pattern. (For example, see 
FIGS. 3A and 3B.) 
The reflective member is typically provided in a reflection chamber which 
further aids in the reflection and refraction of the reflected light into 
a desired footprint. By selecting suitable combinations of reflecting 
elements, planar reflectors, and defusing panels, a wide variety of broad, 
uniformly distributed patterns of light or footprints may be provided. 
Footprint refers to the pattern of light that is projected on the ground 
or other surface surrounding the pole. 
By use of the apparatus of the present invention and positioning such 
apparatus, or light poles, in groups or clusters, the ratio of illumina 
that can be obtained is superior to that previously known. Ratios of 
illumination of 7:1 have previously been considered quite uniform. Ratios 
of illumination of 100-1000:1 are not uncommon. A group of light poles of 
the present invention can be designed so as to provide a ratio of 
illumination of less than about 3:1, and can be made to provide a ratio of 
illumination of less than about 2:1. 
In addition to providing superior ratios of illumination to known light 
poles, pole lights of the present invention are able to be made of plastic 
materials, instead of metal, thereby providing savings of cost, and 
providing increased safety to, for example, the motorist. In addition, 
light poles of the present invention can be made to be approximately 6 
meters tall compared to previous light poles typically 15-18 meters in 
height, and produce comparable footprints. 
An added feature that can be provided as part of the apparatus of the 
invention is a light emitting opening provided in the wall member of the 
light conduit. The light emitting opening or openings can be provided in 
the shape of letters, words, or other shapes. For example, "EXIT" can be 
illuminated in the side wall of a pole positioned at an exit ramp on a 
highway. The loss of light from such an opening can be minimal, with a 
sufficient quantity of light remaining to be reflected by the reflecting 
element.