U.S. patent number 3,786,248 [Application Number 05/253,591] was granted by the patent office on 1974-01-15 for luminaire.
This patent grant is currently assigned to Kim Lighting, Inc.. Invention is credited to Wayne W. Compton.
United States Patent |
3,786,248 |
Compton |
January 15, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
LUMINAIRE
Abstract
A luminaire comprising a lamp and a reflector. The lamp has an
axis of radiation and the property of emitting a disproportionately
large percentage of its luminous flux in an annulus which is
contained within a pair of imaginary divergent conical surfaces,
each at no more than about 50.degree. to the axis of radiation
(100.degree. included angle). The reflector includes reflective
cap, side and end surfaces which together form a cavity in which
the lamp is placed. The cavity has a plane of symmetry. A
longitudinal axis and the axis of radiation lie in the plane of
symmetry. The axis of radiation intersects the longitudinal axis at
an acute angle. The side and end surfaces are, in cross-section,
beaming-directing, and preferably are at least approximations to
parabolas, and the flux radiated from the lamp within said annulus
impinges upon each of these surfaces.
Inventors: |
Compton; Wayne W. (Irvine,
CA) |
Assignee: |
Kim Lighting, Inc. (City of
Industry, CA)
|
Family
ID: |
22960906 |
Appl.
No.: |
05/253,591 |
Filed: |
May 15, 1972 |
Current U.S.
Class: |
362/296.08;
362/296.07 |
Current CPC
Class: |
F21V
7/09 (20130101); F21S 8/086 (20130101); F21V
7/04 (20130101) |
Current International
Class: |
F21V
7/09 (20060101); F21V 7/04 (20060101); F21V
7/00 (20060101); F21S 8/00 (20060101); F21s
001/10 (); F21s 003/10 (); F21s 013/10 () |
Field of
Search: |
;240/25,41.37,73,103 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Wintercorn; Richard A.
Attorney, Agent or Firm: D. Gordon Angus et al.
Claims
I claim:
1. In combination: a lamp which emits visible light, said lamp
having an axis of radiation and the property of emitting a
disproportionately large percentage of its luminous flux in an
annulus bounded by a pair of surfaces of revolution generated
around the axis by generator lines which, in an axial plane,
diverge from the normal to the axis of radiation by no more than
about 50.degree.; and a reflector having a longitudinal axis, an
imaginary central plane which includes said longitudinal axis and
axis of radiation, and an open, inwardly concave cavity in which
the lamp is placed, said cavity opening at a base plane parallel to
the longitudinal axis, said cavity being bounded, at least in part,
by the following reflecting surfaces:
a. a cap surface which overlays the cavity, and extends generally
along and transverse to said longitudinal axis;
b. a pair of concave side surfaces, one on each side of the central
plane, intersecting the cap surface, and extending generally along
said longitudinal axis; and
c. a concave end surface intersecting and interconnecting both side
surfaces and the cap surface, said surfaces being specularly
reflective over the major portion of their areas, and having a
beam-forming property with respect to light emitted by the lamp,
the axis of radiation forming an acute angle with the longitudinal
axis, and the flux within said annulus impinging upon each of said
surfaces.
2. A combination according to claim 1 in which the cap surface is
substantially planar.
3. A combination according to claim 2 in which some portions of the
cap surface are modified by light-scattering facets.
4. A combination according to claim 1 in which the section-lines of
the side surfaces which are formed by intersection with said
surfaces by a plane normal both to the longitudinal axis and to
said side surfaces, and the section-lines formed by intersection of
the end surface and a plane which includes a line in said central
plane that is normal to the longitudinal axis, are at least
approximations to parabolas.
5. A combination according to claim 4 in which said section lines
comprise the arcs of at least two circles of different radius.
6. A combination according to claim 1 in which said side surfaces
are generated by a concave arcuate generator line lying in a plane
normal to the longitudinal axis and moved in a substantially
straight line parallel to said longitudinal axis, said generator
line being at least an approximation to a parabola.
7. A combination according to claim 6 in which said generator line
comprises the arcs of at least two circles of different radius.
8. A combination according to claim 1 in which the end surface is
generated by a concave arcuate generator line which lies in a plane
inclusive of a central axis in said central plane which is normal
to the longitudinal axis, and which generator line is moved through
a circular arc around said central axis, the generator line being
at least an approximation to a parabola.
9. A combination according to claim 8 in which said generator line
comprises the arcs of at least two circles of different radius.
10. A combination according to claim 6 in which the end surface is
generated by a concave arcuate generator line which lies in a plane
inclusive of a central axis in said central plane which is normal
to the longitudinal axis, and which generator line is moved through
a circular arc around said central axis, the generator line being
at least an approximation to a parabola.
11. A combination according to claim 10 in which each of said
generator lines comprises the arcs of at least two circles of
different radius.
12. A combination according to claim 11 in which the cap surface is
substantially planar.
13. A combination according to claim 12 in which some portions of
the cap surface are modified by light- and energy-scattering
facets.
14. A combination according to claim 1 which further includes
socket means for holding said lamp, said socket means being adapted
to hold the lamp at different axial locations along said lamp
axis.
15. A combination according to claim 11 which further includes
socket means for holding said lamp, said socket means being adapted
to hold the lamp at a plurality of different axial locations along
said lamp axis.
16. A combination according to claim 1 in which the end of the
cavity opposite the said end surface is substantially
nonreflective.
17. A combination according to claim 8 in which the end of the
cavity opposite the said end surface is substantially
reflective.
18. A combination according to claim 1 in which the boundaries of
the surfaces at the open edge of the cavity are coplanar.
19. A combination according to claim 11 in which the boundaries of
the surfaces at the open edge of the cavity are coplanar.
20. A combination according to claim 1 in which a support holds the
reflector above the ground, and the greater area of illumination
extends away from the projection of the support on the ground,
there further being provided a socket to receive and support the
lamp, there being a socket at the end of the reflector away from
the support, and the reflecting end section being the closer to the
support.
21. A combination according to claim 1 in which the socket end of
the lamp is deeper in the cavity of the reflector than the free end
of the lamp, and in which the socket end of the lamp is the end
farther removed from the said end surface.
22. A reflector for forming a field of radiated light from a lamp
of the type which emits visible light, said lamp having an axis of
radiation and the property of emitting a disproportionately large
percentage of its luminus flux in an annulus bounded by a pair of
surfaces of revolution generated around the axis by generator lines
which, in an axial plane, diverge from the normal to the lamp axis
by no more than about 50.degree., said reflector having a
longitudinal axis, a central plane which includes said longitudinal
axis and lamp axis, and an open, inwardly concave cavity in which
the lamp is placed, said cavity opening at a base plane parallel to
the longitudinal axis, said cavity being bounded, at least in part,
by the following reflecting surfaces:
a. a cap surface which overlays the cavity, and extends generally
along and transverse to said longitudinal axis;
b. a pair of concave side surfaces, one on each side of the central
plane, intersecting the cap surface, and extending generally along
said longitudinal axis;
c. a concave end surface intersecting and interconnecting both side
surfaces and the cap surface, said surfaces being specularly
reflective over the major portion of their areas; and means for
supporting said lamp in the cavity, the said surfaces having a
beam-forming property with respect to light emitted by the lamp,
the means being so disposed and arranged as to support the lamp so
that its axis of radiation forms an acute angle with the
longitudinal axis, and the flux within said annulus impinges upon
each of said surfaces.
23. A reflector according to claim 22 in which the cap surface is
substantially planar.
24. A reflector according to claim 23 in which some portions of the
cap surface are modified by light-scattering facets.
25. A reflector according to claim 22 in which the section-lines of
the side and end surfaces which are formed by intersection with
said surfaces by a plane normal both to the longitudinal axis and
to said side surfaces, and in which the section-line formed by
intersection of the end surfaces and a plane which includes a line
in said central plane which is normal to the longitudinal axis are
at least approximations to parabolas.
26. A reflector according to claim 25 in which said section lines
comprise the arcs of at least two circles of different radius.
27. A combination according to claim 22 in which said side surfaces
are generated by a concave arcuate generator line lying in a plane
normal to the longitudinal axis and moved in a substantially
straight line parallel to said longitudinal axis, said generator
line being at least an approximation to a parabola.
28. A combination according to claim 1 in which the central plane
is a plane of symmetry.
29. A combination according to claim 4 in which the central plane
is a plane of symmetry.
30. A combination according to claim 21 in which the central plane
is a plane of symmetry.
31. A reflector according to claim 22 in which the central plane is
a plane of symmetry.
32. A reflector according to claim 25 in which the central plane is
a plane of symmetry.
Description
This application relates to luminaires, and in particular to the
combination of a lamp and a reflector which have interrelated
physical properties.
As requirements for illumination of large areas have multiplied, so
too have the consequences of the shortcomings of existing devices
for this purpose, which depend heavily upon refracting bodies for
their control of the light. One objection which is heard with
increasing frequency concerns visual pollution of the environment
caused by glare light scattered by conventional luminaires. Not
only is the background glow brightened by this glare, but the stray
light in itself is unpleasant and even potentially harmful, such as
by causing windshield glare. Also, it reduces the contrast between
an illuminated object, such as a person walking along a sidewalk,
and the background. This endangers the person, because he is, in
effect, less visible. Such contrast should be made as pronounced as
possible. As still another objection, the stray light causes
pupillary constriction. Such constriction limits the ability of the
human vision system to identify illuminated objects.
The increased power consumption needed in order to provide a
specific light intensity at the surfaces to be illuminated, when
light is wasted by glare, raises energy bills.
Yet another disadvantage of the prior art resides in the tendency
of existing illumination means to form "hot spots", or areas of
excessive lighting, while leaving other areas poorly lighted, all
within the intended distribution region of the luminaire.
It is an object of this invention to provide a luminaire which can
illuminate substantial areas with much closer approximation to
uniformity of illumination than has been possible with prior art
reflectors or refractors.
It is another object of this invention to provide a luminaire which
has relatively sharp cut-offs of illumination, thereby
concentrating its light in a restricted, intended area.
Still another object of this invention is to accomplish the
foregoing objectives with the use of commercial lamps which are
readily available on the market, and which can be enclosed in
relatively small enclosures so the luminaire constitutes only a
minimum visual disruption to the surroundings.
Yet another object of the invention is to provide a luminaire whose
distribution of light can be asymmetrical--illuminating regions
farther to one side of the luminaire than to the other--while
utilizing a reflector whose bottom edge is horizontal. With the
reflector of this invention, asymmetric distribution does not
require tilting the reflector, or the use of a refractor, and
therefore the observer does not see a bright light source as he
views the luminaire from the side or front. This is one of the
major advantages of this invention. With it, one can illuminate an
area farther removed from the luminaire on one side than on the
other, and still the emitting region is not tilted so as to be
visible as a bright area in the sky.
This invention provides an elegantly simple luminaire which in
itself is inoffensive in appearance, which illuminates areas with
considerable consistency without appreciable stray glare, and which
is readily adjusted to provide for different configurations of
illumination of areas beneath it.
A luminaire according to this invention comprises in combination a
lamp which emits visible light, and a reflector. The lamp is of the
type which has an axis of radiation and the property of emitting a
disproportionately large percentage of its luminous flux in an
annulus bounded by a pair of imaginary surfaces of revolution
generated around the axis of radiation by generator lines which, in
an axial plane, diverge from the normal to the axis of radiation by
no more than about 50.degree.. The reflector has a longitudinal
axis and a plane of symmetry which includes both the longitudinal
axis and the axis of radiation. The reflector forms an open,
inwardly concave cavity in which the lamp is placed. The cavity is
bounded, at least in part, by the following reflecting surfaces: a)
a cap surface which overlays the cavity and extends generally along
and transverse to the said longitudinal axis; b) a pair of concave
side surfaces, one on each side of the plane of symmetry, each
intersecting the cap surface and extending generally along said
longitudinal axis; and c) a concave end surface which intersects
and interconnects both side surfaces and the cap surface. These
surfaces are specularly reflective over the major portion of their
areas. The axis of radiation forms an acute angle with the
longitudinal axis. The flux within the annulus impinges upon each
of the said surfaces.
According to a preferred but optional feature of the invention,
some portions of the cap surface are modified by light-diffusing
facets.
According to still another preferred but optional feature of the
invention, the section lines of the side and end surfaces are beam
controlling, and in gross are at least approximations to
parabolas.
According to still another preferred but optional feature of the
invention, the said section lines comprise the arcs of at least two
circles of different radius.
The above and other features of this invention will be fully
understood from the following detailed description and the
accompanying drawings in which:
FIG. 1 is a side view, principally in axial cross-section of the
presently preferred embodiment of the invention taken along its
plane of symmetry;
FIG. 2 is a bottom view of FIG. 1, looking upwardly into the
cavity;
FIG. 3 is a cross-section taken at line 3--3 of FIG. 2;
FIG. 4 is a fragmentary cross-section taken at line 4--4 of FIG.
1;
FIG. 5 is a cross-section taken at line 5--5 of FIG. 1; and
FIGS. 6-12, inclusive, are sketches that are explanatory of certain
features of the invention.
A luminaire 20 according to the invention is shown in FIG. 1. It is
fitted into a housing 21 which, because of the compactness of the
elements it contains, may be made as a rectangular parallelopiped.
This housing may readily be attached to a pole or some other kind
of support, such as a wall.
It is desirable, and in general will be the situation, that the
lower surface 22 of the housing will be parallel to the ground. It
is a particular advantage of this invention that such an
arrangement can be made. Conventional luminaires accomplish
asymmetrical distribution of light by tilting the luminare and/or
reflector, or by using refractors. In so doing, their refractors or
reflectors, or both, are directly exposed to and visible by the
observer, and become a prime source of nighttime visual pollution.
Such refractors, reflectors, or both are a common sight on the
night-time skyline. The term "asymmetrical distribution" means that
more light is directed to one side of a plane normal to the
longitudinal axis than to the other side of the axis.
The housing includes four sides 23, a top 24, and an open base 25.
The base has an aperture 26 in which a transparent pane 27 is
fitted. The pane is readily removable from its supporting frame 28.
The frame is attached to the housing.
Auxiliary control equipment 30 is fitted inside the housing. Such
equipment may include ballast, capacitors, circuit boards, switches
and leads. Connections are made to the auxiliary control equipment
and from this equipment to the lamp socket. The foregoing are all
conventional elements and require no detailed description here,
because they form no part of the invention.
A lamp 35 is supported inside a cavity 36 formed by a reflector 37.
The reflector is supported at its edge 38 by the housing. It fills
aperture 26, and flux from the lamp is emitted through the
aperture. The lamp and reflector will now be described in further
detail.
Lamp 35 is of a conventional type used in the illumination field.
The illustrated lamp is a 175 or 250 watt mercury vapor lamp. As
other examples, there may instead be used high pressure sodium
lamps or metallic halide lamps. All of these lamps have a socket
end 40 which is to be screwed into a socket 41, and a glass
envelope 42. They also have an axis of radiation 43 which is
linear. A feature of the class of lamp useful in this invention is
that, with respect to the axis of radiation and a theoretical
center 44 thereon, there is an annulus generated around the lamp
axis which contains a disproportionately large percentage of the
luminous flux emitted by the lamp compared to the percentage of the
flux emitted outside this annulus. For example, such an annulus is
imaginary generated by a pair of generator lines 46, 47 which
diverge from from the normal 48 (a normal plane) to the axis of
radiation by angles 49, 50 which are about 50.degree.. In most
lamps of the type described, about 75 percent of the luminous flux
is emitted in such an annulus in which the total of angles 49 and
50 is less than about 100.degree.. This means that relatively
little light is emitted rearwardly toward the socket end, or
forwardly toward the tip end of the lamp. The candlepower
distribution of this type of lamp is shown in FIG. 8. The distance
of the solid line 66 from the center 67 of the lamp graphically
illustrates the intensity of lumination at the respective angular
position around the center, the distance of line 66 from the center
indicating the relative intensity at the respective angle. A
greater distance from the center in this graph indicates a greater
intensity.
The term "axis of radiation" defines an axis which is related to
the pattern of light intensity emitted by the lamp. It is a central
axis around which the aforesaid annulus is generated. In a
conventional lamp wherein an arc tube is the light source, the
intersections of generator lines 46 and 47 with the axis are spaced
apart by an appreciable distance, perhaps an inch or more, and the
annulus will not have a point center on the axis, but rather a line
coincident with the axis. If the lamp were a theoretical point
source, then the two lines would intersect at the axis of
radiation. In either case, the axis would be the same, because it
is referred to the pattern of emission, and not to the shape or
nature of the light source itself.
For convenience, the theoretical center 44 is referred to. In a
practical arc tube lamp, the center 44 is located at the mid-point
of the envelope.
In order to provide different illumination patterns on the pavement
with a given reflector, means is provided for supporting the lamp
at predetermined locations along both the axis of radiation and the
longitudinal axis of the reflector. For example, socket 41 is
attached to nipple 51 and held to a mounting bracket 52 by lock
nuts 53. The bracket has an elongated slot 54a. The lock nuts can
be loosened to enable the nipple to be axially shifted to move the
lamp axially, and vertically shifted in the slot to move the lamp
vertically. The lamp can thereby be moved to various positions in
the reflector, and the lock nuts tightened to hold it in the
selected location. Two exemplary positions for the lamp are shown
in the drawings, which will provide two different patterns of
illumination. This adjustment feature also enables lamps of
different sizes to be received and placed in selected
locations.
The solid line socket position will hold the lamp in the location
shown by solid line, and retraction and downward movement of the
nipple will move the socket to the dashed line position where the
envelope will be held in the position as shown by the dashed line
with its center at 44a instead of at 44. It will thereby be seen
that the flux within the annulus can be made to impinge differently
on the reflector, depending on the location of the lamp in the
cavity. Other means for locating the lamp in different positions
may readily be devised, such as by stacking up adapter plugs
between the lamp and a stationary socket. The lamp is held so that
its axis of radiation remains in the plane of symmetry 54 of
reflector 37. The plane of symmetry is the plane of FIGS. 1 and 3.
The plane of symmetry shown is also a central plane. As will later
become clear, the plane of symmetry is, in every case, a central
plane. However, in every case, the central plane will not
necessarily be a plane of symmetry, because the side surfaces are
not necessarily identical, although they are identical in the
preferred embodiment. A given lamp is also preferably supported so
that its center 44 remains at a predetermined elevation when the
position of the lamp in the reflector is changed.
A shroud 55 covers the mounting bracket and much of the socket. It
serves to protect leads 56 from the heat of the lamp, and
constitutes an esthetically pleasing envelope.
With initial reference to FIG. 2, the reflector includes a cap
surface 60, a first side surface 61, a second side surface 62, and
an end surface 63. The side surfaces and end surface all intersect
and blend into the cap surface. As can be seen in FIGS. 1 and 2,
the cap surface overlays the cavity and extends transversely
relative to the longitudinal axis 64 of the reflector. The
longitudinal axis lies in the plane of symmetry and extends in a
direction which will ordinarily be parallel to the ground surface
or to whatever surface is being illuminated. It extends midway
between the two side surfaces. It forms an acute angle 65 with axis
of radiation 43. Ordinarily, this angle will be on the order of
about 20.degree.. The cap, side and end surfaces define an inwardly
concave cavity in which the lamp is placed. The cavity opens onto a
base plane, which may be defined as the plane of pane 27. The base
plane is parallel to the longitudinal axis, and in usual usage of
the reflector, it will be parallel to the ground. The reflector
need not be tilted to give an asymmetrical distribution.
To secure the desired asymmetrical distribution, it is necessary to
provide surfaces which will specifically reflect light to each part
of the illuminated area, and in a pattern wherein the intensity is
reasonably uniform over the total illuminated region. As with any
luminaire system, there is no abrupt fall-off from bright light to
total dark in the sense of blackness in immediate contiguity with
illumination. However, in contrast with conventional luminaires, a
sharp fall-off from an acceptable level of illumination to a level
of illumination which is not appreciably bright does occur within a
remarkably small space. In order to accomplish this objective,
reflecting surfaces with beam-forming properties.
The configurations of the foregoing surfaces will now be described.
First, it will be remarked again that the annulus of the lamp is
shown as though it originated at a central point 44, while in a
practical lamp the generator lines 46 and 47 will be separated from
each other by a substantial distance along the axis of radiation
because of the extended length of the arc tube of the lamp.
However, whether the lamp has a point source or a line source, the
geometry is substantially as shown. A point source is used for
convenience in disclosure.
The annulus shown relates to the position of the lamp illustrated
in solid line. In the illustration, if the lamp were about 8 inches
long from the end of the socket to the tip of the glass envelope,
the intersections of generator lines 46 and 47 with lamp axis 43
would be about 2 inches apart, thereby making the annulus longer
than shown, in which case light within the annulus would strike a
larger area of the surfaces. The luminous flux within the annulus,
whatever the axial length, will impinge upon each of the cap
surface, the side surfaces, and end surface 63. Those portions of
these surfaces which intersect the annulus will therefore determine
the distribution of the major proportion of the luminous flux of
the lamp. Some of the flux will, of course, pass directly from the
lamp through aperture 26 without reflection.
The cap surface overlays the lamp. It is advantageous, but not
necessary, to incorporate a plurality of down-light diffusing
facets 68 into this surface. These facets serve to scatter light
rather than to focus it, and perform two useful functions. One such
function is to reduce hot spots on the ground beneath the
reflector. Hot-spots are local regions which are appreciably
brighter than neighboring regions within the area being
illuminated. The scattered light tends to even out the
distribution. The other advantage in scattering some of the light
from the cap surface is that the amount of energy reflected back
into the arc tube is reduced. Energy reflected into the arc tube
shortens lamp life.
The preferred shape of the facets is, as shown, the convex polar
section of a sphere. However, concave polar sections, and other
concave and convex shapes may be used instead, to the same
advantage.
Facets 68 do not scatter the light beyond the field limited by the
reflector, because of the cut-off effect of the outer edge of the
aperture 26. They do, however, appreciably scatter the light
reflected from the cap surface so that there are no areas of
disproportionately great intensity derived from reflection on that
surface alone. The light from the reflector is therefore
"softened".
The side and end surfaces are beam-forming in nature. Preferably,
each forms at least a gross approximation to a parabola for the
purpose of throwing a directed beam sideward relative to the
perpendicular, while the cap surface serves more to illuminate the
area more directly under the luminaire. To form true parabolic
surfaces which are appropriate to the geometries involved not only
involves considerable computation, but also a considerable expense
in tooling. It has been found that optimum light distribution can
be derived from surfaces having areas formed by circularly arcuate
generators, there being more than one such generator for each
surface, their radii being different. Such a construction creates a
light distribution which is at least an approximation to that
created by a true parabolic surface, and in some respects appears
to be superior for the purposes of this invention.
Accordingly, and as can best be seen in FIG. 5, surface 61 is
formed by a first radius 70 and a second radius 71, while surface
62 is formed by a first radius 72 and a second radius 73. These
surfaces are mirror images of one another, and the dimensions of
one are the dimensions of the other. In both cases, the surface
portions formed by the first radii are of larger radius and closer
to the open end of the cavity, while the second radii are shorter
than the first radii and lie farther within the cavity. The
location of the centers of these radii are shown in the figure. A
fairing or transition radius 74 is formed between the cap surface
and the side surfaces. It has no necessary correlation to the
parabolic approximation, although it may have, if desired. It is
primarily intended to constitute a smooth transition between the
side surfaces and the cap surface.
Surfaces 61 and 62 preferably are in the form of "bent planes", and
accordingly, the cross-sections shown in FIG. 5 are generators
which generate the respective surfaces by being moved parallel to,
and at a constant distance from, the longitudinal axis. However, it
will occasionally be found that, instead of using shapes which lie
principally at constant distances from the longitudinal axis, some
curvatures may be advantageously introduced into surfaces 61 and
62, such as by bowing them outwardly. Such modifications remain
within the concept of the invention.
End section 63 is preferably formed as a surface of revolution
revolved around a central axis 80, which axis lies in the plane of
symmetry and normal to the longitudinal axis. Surface 63 has a
radius C from this central axis, details of which will be found in
the accompanying tables. The generator line 81 is shown in FIG. 3,
and in this surface, as well as in the other surfaces defined as
generator surfaces, the term is used in a geometric sense of a line
moved through space to generate a surface. The curvatures of
surfaces 40 and 63 as shown are identical at the plane of symmetry,
and the dimensions given for surface 40 are identical to those of
surface 63, and vice versa. Full details of only one are is shown
in order to simplify the drawings. If, instead of having the light
reflected identically by each of the side surfaces 61 and 62, it is
desired to have one throw its light farther than the other, then
the curvatures of the two side surfaces may not be identical, but
instead may be differently curved. Such a construction is still
within the concept of the invention. In such case, a plane of
symmetry will not exist between two mirror-image surfaces, but the
plane would more properly be described as a central plane, i.e. the
plane in which the axis of radiation lies, and the terms central
plane and plane of symmetry are used interchangeably herein, as
appropriate.
As will be seen in the drawings, the generator line 81, and
therefore the resulting surface 63 in vertical section, is an
approximation to a parabola and is formed by a first radius 82 and
a second radius 83, which radii are preferably, but not
necessarily, identical to radii 70-73, respectively, and located at
substantially the same elevations relative to the open end of the
cavity. Therefore, the end surface constitutes a substantial
continuation of side surfaces 61 and 62. Central region 85 of end
surface 40 is not necessarily a curve. Instead, it may constitute a
bent plane with the curvature shown in FIG. 3, and it is connected
to the side surfaces by transition regions 86, 87 which are formed
by radii and curves as shown in the drawings. Regions 85, 86 and 87
are not substantially important to the reflector's performance for
the reason that, with respect to the heavy dashed line identified
as "edge 88 of light-absorbing region", those portions toward the
socket end, to the left of that edge line 88, are painted flat
black as is the socket shroud. Accordingly, substantially no
reflection occurs from that end. Instead, substantially all
reflection occurs from the side, end and cap surfaces.
One reason that these regions 85-87 are relatively unimportant is
that little lamp flux impinges upon them due to the nature of the
distribution of the flux from the lamp itself. A reason for
painting these areas black is that otherwise they would reflect
light toward the house side, frustrating one objective of the
luminaire, which is to cast its light away from a pole or house,
and not toward it, from a horizontal aperture.
The detailed construction of the presently preferred embodiment of
reflector is shown in the following table. All dimensions are in
inches, and the identification of dimensions relate to those which
are shown in the accompanying drawings.
RADIUS DIMENSIONS
WL No. RAD. A RAD. B RAD. C RAD. D WL-0 5.62 16.34 6.00 2.00 WL-1
5.62 16.34 6.00 2.00 WL-2 5.59 16.28 5.96 1.96 WL-3 5.50 16.18 5.87
1.78 WL-4 5.34 16.03 5.71 1.71 WL-5 5.03 15.71 5.40 1.40 WL-6 4.56
15.25 4.93 0.93 WL-7 3.91 14.59 4.28 0.81 WL-8 2.97 13.65 3.34 0.62
WL-8.5 2.31 13.00 2.65 0.50
OTHER DIMENSIONS
WL No. RAD. A RAD. B RAD. C RAD. D AA 1.656 HH 2.375 QQ 7.68 XX
1.50 AF 0.62 BB 12.00 JJ 0.343 RR 7.87 YY 1.218 AG 9.375 CC 6.00 KK
4.68 SS 7.96 ZZ 2.375 AH 1.906 DD 6.312 LL 5.34 TT 7.515 AB 1.06
AJ1.50 EE 8.00 MM 6.28 UU 12.312 AC 0.375 AK 2.00 FF 4.312 NN 6.93
VV 7.515 AD 2.50 AL 1.25 GG 1.218 PP 7.40 WW 12.312 AE 2.00
the reflector disclosed above is designed to use all of the
following lamps:
175 Watt Mercury Vapor
250 Watt Mercury Vapor
250 Watt High Pressure Sodium
400 Watt Mercury Vapor
400 Watt Metallic Halide
400 Watt High Pressure Sodium
The location of the socket is moved as previously discussed, to
place the lamp's center at the location required for a respective
distribution of light.
Some considerations and features of this luminaire are shown in
FIGS. 6-12. For convenience, there has been set up a reference to a
house side and a street side. Of course, there need not be a house
or a street. Instead, the luminaire might be used to illuminate a
parking lot or other open area far from a building. What is shown
is a situation where the light distribution on one side of the
luminaire itself extends to a lesser horizontal distance than on
the other, and in which the shape of the illuminated region is
quite carefully controlled, with sharp cutoffs at the edges, there
being a substantially consistent and relatively constant
illumination throughout the illuminated area, and a relatively
sharp rate of decrease of brightness as one moves away from the
area intended to be illuminated. This is accomplished, while using
a horizontal aperture, and no refractors, thereby greadly reducing
stray glare.
As to the illumination caused by this luminaire, initial attention
is called to FIGS. 6 and 7. In these figures there are shown two
types of distributions which are defined as ANSI Type II and Type
III, respectively. The Type II illumination casts a lesser throw
onto the street side than the Type III illumination. In both cases,
the illumination on the house side is about the same. Other
patterns can be made by shifting the lamp along its axis, or by
varying the shape and/or size of the reflector. The luminaire 90 is
shown in both figures, and the illuminated area is shown in shaded
line with boundaries 91, 92 respectively. These boundaries indicate
the outer limit of substantial illumination from the luminaire as
cast upon the ground. A pole 93 is schematically shown holding the
luminaire above the ground.
The two different patterns were obtained by the use of the same
reflector and lamp. The pattern of FIG. 6 was changed to that of
FIG. 7 by shifting the lamp horizontally toward socket end 40. This
was done by moving the lamp socket toward the socket end, and
shifting the socket upwardly in slot 54a. The sideward throw was
not appreciably changed. To change the sideward throw, one would
move the lamp center of the vertically. Various combinations of
movement are made to form other illumination patterns.
FIG. 8 shows the candlepower distribution of the lamps disclosed
above. The heavy lines 66 indicate the candlepower intensity at the
respective angles. It will be observed that a disproportionately
small part of the radiation is radiated outside of the annulus.
FIG. 9 shows the interaction between the lamp and the reflector.
The candlepower curve 66 of the lamp by itself is shown in dashed
line, while the resulting candlepower curve of the lamp plus
reflector is shown by line 95. It will be seen that the reflector
has modified the flux distribution of the lamp so that a minimum of
light is projected toward the house side, while the major portion
of light is efficiently projected on the street side where it is
needed. This is one of the important consequences of the
combination of the particular lamp and reflector, and still can be
secured with a horizontal aperture.
FIGS. 10 and 11 show the effect of shifting the lamp along its axis
of radiation. In FIG. 10, the Type III distribution of FIG. 7 is
shown. In this condition, the lamp is in the solid line position of
FIG. 1, 1.e. closer to the pole end itself. In this case, it will
be found that the major proportion of the flux departs in a band
97, as shown in FIG. 10, and that this band will intersect the
ground in the manner shown in FIG. 7.
In FIG. 11, the center of the lamp 35 is in the dotted line
position shown in FIG. 1, and in this case, the major proportion of
the flux departs in band 98, whose intersection with the ground is
that shown in FIG. 6.
FIG. 12 shows a section similar to that of FIG. 5, the section
being taken in a plane normal to that of the longitudinal axis.
This figure illustrates the cut-off effect of the bottom edge 38 of
reflector 37. As will be seen, the lower edge acts as a cut-off for
direct light from the lamp, and reflected light from the various
surfaces will be substantially confined within the region defined
by edges such as the major cut-off edge 99. The scattering action
of the facets is shown by ray 100, whose reflected direction is
indeterminate, but which is limited by the cut-off edge 99.
The reflector shown surfaces which not a true parabola, but it is
an approximation to one. A true parabola could be used. It would
section-lines reflect a collimated beam of light toward the
pavement. The directed beam produced by the illustrated reflector
is not truly collimated, but is a projected beam, even though it is
not a bundle of parallel rays, and tends to spread the light
somewhat, as contrasted with a bundle of strictly parallel rays. In
this luminaire, the beam directing effect is used to project a beam
away from the surface. Beams are sent to both sides and away from
the house. The blackened surface prevents light from being
reflected to the house side. Light reflected from the surfaces and
direct radiation from the lamp illuminate the area directly beneath
the aperture and to either side and to the street side within the
range ermitted by the cut-off edges. Together these beams and the
direct radiation will form a reasonably uniform light pattern.
Some variation from the true collimation which would be produced by
a parabola with the lamp at its focus has been found useful,
because it does appear to give a more even distribution of light.
The effect of this arrangement is shown in FIG. 12, where two beams
110, 111 are shown emanating from the two circular portions 112,
113 of side surface 61, that are formed by radii 71 and 70,
respectively. Of course, these beams will not be strictly
collimated, because the cylindrical surfaces will tend to spread
the beam, but the center of the lamp is spaced from the respective
section between the center and the surface, so that at least some
beam directing of the radiation from the lamp is accomplished. The
term "beam-forming" or beam-directing is used to describe the
function of the reflecting surfaces in forming a beam of light. The
term "specular" is intended to define the function of reflection of
light, in contrast to the dull and diffuse illumination produced by
a matte surface.
To change the light distribution pattern, the lamp is shifted so as
to radiate more or less light on the different portions of the
reflector, and at different positions relative to the "quasi-focus"
of the reflector, i.e., the location of the focus of the parabola
which the sections approximate. It should be borne in mind that
these light sources are not true points or lines, but physical
structures of substantial length and width. Therefore, the
definition of location of the axis of radiation relative to the
quasi-focus must be somewhat approximate. It may be said in general
that a downward displacement of the lamp will tend to increase the
lateral throw. A displacement toward the end surface has a lesser
effect than downward displacement, but does cause a farther throw
onto the street side (see FIGS. 10 and 11). In most practical
applications, the axis of radiation will pass relatively near to
the quasi-focus of the approximated parabola, and in the preferred
form, will intersect this focus somewhere along the length of the
axis of radiation. The approximated parabola can best be drawn by
laying a french curve as close as possible to the cylindrical
sections.
The dimensional notations WL in the drawings relate to the term
"water line" frequently used in die-making operations, and the
dashed lines following them is the number of inches up from the
bottom edge 38. All dimensions are referred to this water line.
Thus, WL-1 means a horizontal section taken 1 inch above the lower
edge of the reflector.
The reflector shown is simple in shape, readily developed by a tool
and die man, and easily produced in common and practical
manufacturing operations. It is surprisingly effective in its
control of high angle glare light and of distribution patterns on
the ground. The distribution pattern may readily be varied by
shifting the location of the lamp along its axis, and by
manufacturing the reflector in variants of the example. The
intensity of light may be varied by substituting lamps of different
wattage. The construction is adapted to use with any suitable lamp
of the class described, and may readily be scaled up or down as to
size. The entire system may be placed in a rectangular enclosure of
elegant simplicity.
Attention is further called to the fact that the socket end of the
lamp is nearest the area being illuminated, and does not lie in the
path of useful light.
This invention is not to be limited by the embodiment shown in the
drawings and described in the description, which is given by way of
example and not of limitation, but only in accordance with the
scope of the appended claims.
* * * * *