U.S. patent number 3,836,767 [Application Number 05/335,538] was granted by the patent office on 1974-09-17 for lighting fixtures.
This patent grant is currently assigned to Moldcast Manufacturing Company. Invention is credited to Martin Lawrence Lasker.
United States Patent |
3,836,767 |
Lasker |
September 17, 1974 |
LIGHTING FIXTURES
Abstract
A compact lighting fixture, principally for outdoor use, employs
a pair of reflectors in conjunction with a lamp having an elongated
light source. One of the reflectors has a downwardly facing concave
internal reflecting surface which surrounds the light source. The
other reflector is located beneath the first reflector and has a
concave external reflecting surface which faces outwardly and
upwardly. The light source is aligned with the vertical axis of the
fixture, which is the common axis of both reflectors. Light emitted
from the source is reflected from the upper reflector to the lower
reflector and is then projected outwardly, some light being
projected outwardly directly from the source, without reflection. A
glare baffle extends inwardly from the bottom of the upper
reflector. As a result of this optical system, most of the light is
projected from the fixture at a high angle relative to downward
vertical, but light cut-off occurs at a selected angle less than
90.degree. relative to downward vertical. The light is evenly
distributed on the ground illuminated by the fixture. Glare is
minimized. The upper reflector can be modified to produce
asymmetrical horizontal light distribution patterns. The reflectors
are surrounded by an enclosure having an opaque upper section and a
light-transmitting lower section. Reflections from the inner
surface of the loser section may provide fill-in illumination near
the vertical axis of the fixture. A structural tube extends
upwardly through the lower reflector and supports the upper
reflector and the upper section of the enclosure upon radially
extending arms. The tube may contain a spring-biased, centered
receptacle for the lamp, which rests upon a seat at the top of the
tube. The upper reflector may be formed in two parts, one part
being fixed to a removable top wall of the upper section of the
enclosure to provide access to the lamp.
Inventors: |
Lasker; Martin Lawrence
(Metuchen, NJ) |
Assignee: |
Moldcast Manufacturing Company
(Newark, NJ)
|
Family
ID: |
23312197 |
Appl.
No.: |
05/335,538 |
Filed: |
February 26, 1973 |
Current U.S.
Class: |
362/217.07;
362/303; 362/217.14 |
Current CPC
Class: |
F21V
21/10 (20130101); F21S 8/083 (20130101); F21V
7/005 (20130101); F21Y 2103/00 (20130101) |
Current International
Class: |
F21V
7/00 (20060101); F21S 8/08 (20060101); F21V
21/10 (20060101); F21s 003/10 () |
Field of
Search: |
;240/25,11.4,41.1,51.11,84,64,41.35C,81A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
50,320 |
|
May 1935 |
|
DK |
|
763,317 |
|
Feb 1933 |
|
FR |
|
Primary Examiner: Greiner; Robert P.
Attorney, Agent or Firm: Shapiro and Shapiro
Claims
The invention claimed is:
1. A lighting fixture comprising upper and lower reflectors, and
lower reflector being positioned beneath said upper reflector and
having a common vertical axis therewith, an elongated light source
positioned vertically along said axis between said reflectors, and
means including a downwardly-facing, concave, internal reflecting
surface of said upper reflector and a cooperating
upwardly-outwardly-facing, concave, external reflecting surface of
said lower reflector for causing light rays emitted from the upper
end of said elongated source to be reflected from said surface of
said upper reflector to said surface of said lower reflector and
then to be reflected thereby outwardly and downwardly substantially
at a first predetermined angle relative to downward vertical and
for causing light rays emitted from the lower end of said source to
be reflected from said surface of said upper reflector to said
surface of said lower reflector and then to be reflected thereby
outwardly and downwardly substantially at a second predetermined
angle relative to downward vertical which is less than the first
angle.
2. A lighting fixture in accordance with claim 1, wherein said
means causes light rays emitted from the upper end of said source
and reflected from said surface of said upper reflector to said
surface of said lower reflector to cover substantially more of the
length of said surface of said lower reflector than light rays
emitted from the lower end of said source and reflected from said
surface of said upper reflector to said surface of said lower
reflector.
3. A lighting fixture in accordance with claim 2, wherein the
first-mentioned light rays cover substantially the entire length of
said surface of said lower reflector.
4. A lighting fixture in accordance with claim 2, wherein the light
intensity distribution of said fixture at one side of said axis in
a vertical plane containing said axis is substantially in
accordance with the distribution illustrated in FIG. 2.
5. A lighting fixture in accordance with claim 2, wherein said
source is surrounded by said upper reflector and wherein the top of
said lower reflector and the bottom of said upper reflector are
positioned relative to each other and said source to provide a
space through which light is emitted directly from said source
outwardly and downwardly between said reflectors without reflection
from said surfaces, the total amount of light emitted fro said
fixture being predominantly light reflected from said reflecting
surfaces rather than emitted directly from said source without
reflection from said surfaces.
6. A lighting fixture in accordance with claim 5, wherein the
intensity of light emitted directly from said source without
reflection from said surfaces decreases progressively above a third
predetermined angle relative to downward vertical up to said first
angle and wherein the intensity of light reflected from said
surfaces increases progressively above said third angle up to said
first angle.
7. A lighting fixture in accordance with claim 6, wherein said
first angle is about 67.degree. and wherein said third angle is
about 52.degree..
8. A lighting fixture in accordance with claim 1, wherein said
first angle is about 67.degree..
9. A lighting fixture in accordance with claim 8, wherein said
second angle is about 48.degree..
10. A lighting fixture in accordance with claim 1, wherein said
first angle is about 80.degree..
11. A lighting fixture in accordance with claim 1, wherein light
rays emitted from said upper end of said source at different angles
in a vertical plane and reflected from said surface of said upper
reflector cross over at points which in general are located
laterally outward of the cross over points of light rays emitted
from the lower end of said source at different angles in the
vertical plane and reflected from said surface of said upper
reflector.
12. A lighting fixture in accordance with claim 11, further
comprising a glare baffle extending laterally inward toward said
vertical axis from the vicinity of the lower end of said upper
reflector, said light source having an envelope surrounding it, and
said glare baffle intercepting rays emitted from said envelope and
reflected from said surface of said upper reflector to said surface
of said lower reflector along paths which would cause said rays to
be reflected from said surface of said lower reflector at a maximum
angle relative to downward vertical greater than said first
angle.
13. A lighting fixture in accordance with claim 12, wherein said
maximum angle is about 75.degree..
14. A lighting fixture in accordance with claim 12, wherein said
maximum angle is about 90.degree..
15. A lighting fixture in accordance with claim 1, wherein said
lower reflector is positioned with respect to said upper reflector
to provide paths for the emission of light downwardly at angles
less than said second angle without reflection from said reflecting
surface of said lower reflector.
16. A lighting fixture in accordance with claim 15, wherein said
source has an envelope and rays from said envelope extend along
said paths after reflection from said surface of said upper
reflector.
17. A lighting fixture in accordance with claim 1, wherein said
fixture has a light-transmitting enclosure section laterally
outward of said lower reflector and wherein said source is
positioned relative to said lower reflector and said enclosure to
provide paths from said source to said enclosure section at angles
of incidence upon said enclosure section which are low enough to
cause the light rays to be reflected downwardly from said enclosure
section.
18. A lighting fixture in accordance with claim 1, wherein said
upper reflector has a section of its reflecting surface angulated
in a horizontal plane with respect to other sections of that
reflecting surface for modifying the distribution in a horizontal
plane of light projected by said fixture.
19. A lighting fixture in accordance with claim 18, wherein the
first-mentioned section is diffusely reflecting and said other
sections are specularly reflecting.
20. A lighting fixture in accordance with claim 1, wherein said
upper reflector is supported upon the outer ends of arms extending
laterally outward from arm supporting means at the top of said
lower reflector.
21. A lighting fixture in accordance with claim 20, wherein said
fixture has an enclosure with an upper section surrounding said
upper reflector and supported upon the outer ends of said arms and
with a lower, light-transmitting section surrounding said lower
reflector and mounted upon means for supporting said fixture.
22. A lighting fixture in accordance with claim 1, further
comprising an additional reflecting surface portion near the open
bottom of said upper reflector for causing light rays emitted by
said lower end of the light source and striking said additional
reflecting surface portion to be reflected therefrom to said
surface of said lower reflector for thereby being reflected
outwardly and downwardly from the lighting fixture substantially at
said first angle.
23. A lighting fixture comprising an upper reflector and a lower
reflector, said upper reflector having a downwardly-facing
reflecting surface for reflecting light to said lower reflector,
said lower reflector being located beneath said upper reflector and
having an outwardly facing surface for reflecting outwardly light
reflected thereto by said surface of said upper reflector, a
plurality of arms extending outwardly from the upper end of said
lower reflector, means for supporting the inner ends of said arms,
and means for supporting said upper reflector upon the outer ends
of said arms.
24. A lighting fixture in accordance with claim 23, wherein said
arms are vertical fins.
25. A lighting fixture in accordance with claim 23, wherein said
lighting fixture has an enclosure with an upper section surrounding
said upper reflector and supported upon the outer ends of said arms
and with a lower section of light-transmitting material surrounding
said lower reflector and mounted upon base means independently of
said upper section.
26. A lighting fixture in accordance with claim 25, wherein said
means for supporting the inner ends of said arms and said lower
reflector are mounted on said base means, and wherein said lower
section of said enclosure is supported on said base means by
cushion means.
27. A lighting fixture in accordance with claim 23, wherein said
fixture has a receptacle for receiving a lamp and for positioning
said lamp between said reflectors.
28. A lighting fixture in accordance with claim 27, wherein said
receptacle is spring-biased downwardly, and further comprising an
annular seat above said lower reflector against which said lamp is
seated by the spring bias of said receptacle.
29. A lighting fixture in accordance with claim 28, wherein said
lower reflector is tubular and wherein said receptacle is supported
for vertical movement within said lower reflector and has means for
centering the receptacle therein.
30. A lighting fixture in accordance with claim 23, wherein said
fixture has means for mounting a lamp beneath said upper reflector
and has an enclosure with an upper section surrounding said upper
reflector and having a top wall which opens, said upper reflector
comprising two parts, one of which is supported upon said top wall
and moves therewith relative to the other part to provide access to
said lamp when the top wall is opened.
31. A lighting fixture in accordance with claim 23, wherein said
means for supporting the inner ends of said arms comprises a tube
extending vertically within said lower reflector and protruding
therefrom at the top of said lower reflector.
32. A lighting fixture having a vertical axis and having spaced
upper and lower reflectors, each of the reflectors having a
reflecting surface which is a surface of revolution about said
axis, and means including a light source cooperating with the
reflecting surface of said upper reflector and the reflecting
surface of said lower reflector for reflecting light emitted by
said source from said upper reflector and then from said lower
reflector in sequence and for projecting the light along different
paths downwardly and outwardly from said fixture upon a horizontal
plane below said fixture with intensities proportional to the
lengths of the paths so that an illumination pattern with
substantially even illumination is formed in said plane over a
generally circular illuminated area surrounding said axis.
33. A lighting fixture in accordance with claim 32, wherein said
surface of said upper reflector is a downwardly concave internal
surface surrounding said source and wherein said surface of said
lower reflector is an outwardly concave external surface with its
lower end farther from said axis than its upper end.
34. A lighting fixture in accordance with claim 33, wherein light
rays from said source are reflected by the reflecting surface of
said upper reflector at different angles and are redirected by the
reflecting surface of said lower reflector downwardly and outwardly
at substantially a predetermined angle.
35. A lighting fixture in accordance with claim 33, wherein said
source is an elongated source aligned with said axis, wherein light
rays from the upper end of said source reflected by the surface of
said upper reflector to the surface of said lower reflector are
redirected at substantially a first predetermined angle relative to
downward vertical, and wherein light rays from the lower end of
said source reflected by the surface of said upper reflector to the
surface of said lower reflector are redirected thereby downwardly
and outwardly at substantially a second predetermined angle
relative to downward vertical.
36. A lighting fixture in accordance with claim 35, wherein said
first angle is greater than said second angle and wherein the
amount of light projected at said first angle is greater than that
projected at said second angle.
37. A lighting fixture in accordance with claim 36, wherein the
spacing of said reflectors provides paths therebetween for direct
downward and outward emission of light from said fixture by said
source without reflection from said surfaces, the amount of such
light being less than the amount of light reflected from said
surfaces.
38. A lighting fixture in accordance with claim 32, wherein said
fixture comprises means for cutting off the projection of light
from said fixture at a predetermined angle relative to downward
vertical which is less than 90.degree..
39. A lighting fixture in accordance with claim 38, wherein the
last-mentioned means comprises a glare baffle protruding inwardly
from the reflecting surface of said upper reflector toward said
axis.
40. A lighting fixture comprising an upper reflector and a lower
reflector having a common vertical axis, each of said reflectors
having a reflecting surface which is a surface of revolution about
said axis, the upper reflector surface being shaped to reflect
light rays from a source to the lower reflector surface in axial
planes, the lower reflector surface being shaped to reflect
outwardly from said axis in axial planes light rays which are
directed thereto by the upper reflector surface in axial planes,
and said upper reflector having at least one reflecting surface
section which is not concentric with the first-mentioned surface
for directing light rays from said source to said lower reflector
surface in planes which are not axial, whereby the amount of light
directed by said lower reflector surface in some directions is
greater than in others.
41. A lighting fixture comprising an upper reflector and a lower
reflector having a common vertical axis, each of said reflectors
having a reflecting surface which is a surface of revolution about
said axis, the upper reflector surface being shaped to reflect
light rays from a source to the lower reflector surface in axial
planes, the lower reflector surface being shaped to reflect
outwardly from said axis in axial planes light rays which are
directed thereto by the upper reflector surface in axial planes,
and said upper reflector having at least one reflecting surface
section which is not concentric with the first-mentioned surface
for directing light rays from said source downwardly and outwardly
without reflection from said lower reflector.
42. A lighting fixture in accordance with claim 41, there being a
pair of said sections angulated oppositely in a horizontal plane to
project light rays outwardly at opposite sides of said fixture
without reflection from said lower reflector.
43. A lighting fixture in accordance with claim 41, wherein said
fixture has a glare baffle for limiting the maximum angle with
respect to downward vertical of light rays projected from the
fixture.
44. A lighting fixture comprising an upper reflector, a lower
reflector, and a light source, said upper reflector having a
reflecting surface shaped to direct upon progressively higher
elements of a reflecting surface of said lower reflector light rays
emitted from a point of said source and reflected by progressively
lower elements of the first-mentioned surface, said surface of the
lower reflector being shaped to reflect such rays downwardly along
substantially parallel paths.
Description
BACKGROUND OF THE INVENTION
This invention relates to lighting fixtures and is more
particularly concerned with outdoor lighting fixtures of the type
supported upon posts or poles.
My prior U.S. Pat. No. 3,651,320, granted Mar. 21, 1972, discloses
a lighting fixture which provides even illumination over a large
area of the ground and which provides complete glare cut-off above
a selected angle relative to downward vertical, such as an angle of
72.degree.. The intensity of the light emitted by the fixture is
relatively low directly below the fixture, and the intensity
increases smoothly as the angle of emitted light relative to
downward vertical increases up to a predetermined angle, so that
light which travels farther to reach the ground has greater
intensity. To achieve this result the lighting fixture of my prior
patent employs a pair of reflectors, one of which is substantially
tubular and surrounds a portion of the lamp and the other of which
is spaced above the first reflector and has a larger diameter. An
enclosure of light-transmitting material having a diameter not less
than the diameter of the upper reflector extends between and is
connected to the reflectors. The enclosure has a central opening on
its underside, and an annular support member is secured to the
enclosure and extends through the opening. The lower reflector is
mounted on the support member and extends therethrough into the
enclosure. The lamp, which is hidden from view, emits light to the
upper reflector directly, as well as by reflection from the lower
reflector. The upper reflector distributes the light in the desired
pattern.
While the lighting fixture of my prior patent is quite effective in
producing the desired illumination patterns (even asymmetrical
patterns in a horizontal plane -- by modification of the lower
reflector), a need has existed for a different type of lighting
fixture capable of producing the same or similar light distribution
patterns, with a wide variety of lamps, but without employing an
upper reflector having a diameter substantially larger than the
diameter of a lower reflector. It is desirable also that the
support of the upper portion of the fixture be independent of
light-transmitting material of the enclosure, so that if the
light-transmitting material is broken, the upper portion of the
fixture will not lack support.
The prior art is replete with post-mounted and other lighting
fixtures, many of which employ a pair of reflectors in conjunction
with a lamp, and many of which attempt to provide different types
if illumination patterns, low-glare illumination, and even
illumination which cuts off above certain vertical angles. See, for
example, U.S. Pat. Nos. 3,679,889; 3,609,340; 3,463,917; 3,089,024;
1,270,261; 2,017,716; 2,191,379; 2,066,631; British Pat. Nos.
1,032,070 (1966); 777,482 (1957); 770,518 (1957); 516,361 (1940);
and Danish Pat. No. 50,320 (1935). However, the prior art has
failed to teach simple, compact, and aesthetically pleasing
lighting fixtures which are capable of producing illumination
patterns and glare cut-off characteristics of the type produced by
the lighting fixture of my prior patent. The prior art is also
replete with different arrangements for supporting reflectors or
other portions of lighting fixtures, including arrangements using
radiating arms. See, for example, U.S. Pat. Nos. 3,363,093;
3,478,200; 3,339,065; and 3,666,934. Nevertheless, no satisfactory
arrangement is disclosed in which a lighting fixture having the
aforementioned attributes provides support for the upper portion of
the reflector independently of a light-transmitting lower portion
and in a manner that is aesthetically pleasing without detracting
from structural strength or optical performance. Nor does the prior
art teach such lighting fixtures which are capable of using a wide
variety of lamps or which provide easy lamp access and ensured lamp
alignment.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide
improved lighting fixtures, particularly lighting fixtures
employing an upper reflector which collects light from a lamp and
reflects the light to a lower reflector which projects and
distributes the light.
A further object of the invention is to provide lighting fixtures
of the aforesaid type which are compact, simple in construction,
sturdy, and aesthetically pleasing.
Another object of the invention is to provide lighting fixtures of
the aforesaid type which may be used with a wide variety of lamps,
but particularly lamps having elongated light sources, such as
filaments or arc tubes which may be positioned vertically.
A further object of the invention is to provide lighting fixtures
of the aforesaid type which produce large amounts of light at high
angles relative to downward vertical but in which the light is
substantially cut off at a selected angle less than 90.degree.
relative to downward vertical.
Still another object of the invention is to provide lighting
fixtures of the aforesaid type incorporating a simple but effective
glare cut-off baffle.
A still further object of the invention is to provide lighting
fixtures of the aforesaid type in which the intensity of the light
projected is greatest at a selected high angle relative to downward
vertical and decreases progressively at lower angles to provide
substantially even illumination over a large area beneath the
fixture.
Yet another object of the invention is to provide lighting fixtures
of the aforesaid type in which fill-in illumination adjacent to a
post is readily achieved.
A still further object of the invention is to provide unique
lighting fixtures having an upper reflector and a lower reflector,
in which the lower reflector, serving to distribute light, is
surrounded by a light-transmitting section of an enclosure, the
upper reflector and upper section of the enclosure being supported
securely, unobtrusively, and independently of the
light-transmitting section of the enclosure.
An additional object of the invention is to provide such lighting
fixtures in which the lamp is accurately positioned in a simple
manner and in which access to the lamp is easily obtained.
Briefly stated, preferred embodiments of the invention employ a
pair of reflectors in conjunction with a lamp having an elongated
light source that is oriented vertically. One of the reflectors is
disposed above the other reflector, surrounds the light source, and
reflects light from the source to the lower reflector, which
projects and distributes the light. The upper reflector has a
downwardly-facing concave internal reflecting surface which is a
surface of revolution about a vertical axis aligned with the light
source. The lower reflector has a concave external reflecting
surface which faces upwardly and outwardly and which is also a
surface of revolution about the vertical axis. Light emitted from
the upper end of the light source is reflected from the upper
reflector to the lower reflector and is projected by the lower
reflector at a high angle relative to downward vertical, such as
67.degree.. Light emitted from the lower end of the light source is
reflected from the upper reflector to the lower reflector and is
projected by the lower reflector at a somewhat lower angle, such as
48.degree.. Moreover, light emitted from the upper end of the light
source covers much more of the height of the lower reflector than
light emitted from the lower end of the light source. Light is also
emitted directly from the lamp, without reflection. The intensity
of this light is greatest at an angle relative to the downward
vertical such as 52.degree., decreasing at higher and lower angles.
Above a certain angle, such as 52.degree., the intensity curves of
light projected by the lower reflector and light emitted directly
from the lamp are oppositely directed, the former increasing with
increase in vertical angle and the latter decreasing. An inwardly
directing glare baffle at the bottom of the upper reflector ensures
light cut-off at a predetermined maximum angle, such as 75.degree.
relative to downward vertical. Fill-in illumination immediately
below the fixture may be provided by stray light from the upper
reflector, which may be emitted from the lamp envelope, and/or by
light reflected from the inner surface of a light-transmitting
enclosure section which surrounds the lower reflector. By virtue of
the invention an even light distribution is produced over a large
area of the ground below the lighting fixture, yet glare is
minimized. By modification of the upper reflector, illumination may
be increased in certain azimuthal directions and decreased in
others. In a particular mechanical embodiment of the invention the
upper reflector and the upper section of the enclosure are
supported upon arms which radiate from a structural tube extending
through the lower reflector, and the support is independent of the
light-transmitting section of the enclosure which surrounds the
lower reflector. The lamp is received in a centered receptacle
within the tube and is seated at the upper end of the tube. Access
to the lamp is provided by forming the upper reflector in two
parts, one part being movable with a top wall of the enclosure to
expose the lamp.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be further described in conjunction with the
accompanying drawings, which illustrate preferred and exemplary
embodiments and wherein:
FIG. 1 is a perspective view of a first embodiment of the invention
illustrating the mounting of the lighting fixture upon a pole and
showing the lower reflector surrounded by the light-transmitting
section of the enclosure, the glare baffle, and the support arms
for the upper section of the enclosure;
FIG. 2 is a polar coordinate diagram illustrating the intensity of
the light projected by the invention at different angles relative
to downward vertical;
FIG. 3 is a perspective view of another embodiment of the
invention, in which the fixture is supported upon a short post;
FIG. 4 is a diagrammatic vertical sectional view illustrating the
operation of the embodiment of FIG. 3;
FIGS. 5, 6, and 7 are diagrammatic vertical sectional views
illustrating the operation of the embodiment of FIG. 1 and to a
large extent the operation of the embodiment of FIG. 3 also;
FIG. 8 is a vertical sectional view illustrating the embodiment of
FIG. 1 as seen along line 8--8 of FIG. 9 in the direction of the
arrows, most of the structure illustrated being applicable to the
embodiment of FIG. 3 also;
FIG. 9 is a bottom plan view of the embodiment of FIG. 1 as seen in
the direction of the arrows 9--9 of FIG. 8;
FIG. 10 is a diagrammatic vertical sectional view illustrating an
alternative mode of mounting the lamp;
FIG. 11 is a diagrammatic vertical sectional view employed in
conjunction with FIG. 12 to illustrate the manner in which the
horizontal light distribution may be modified;
FIG. 12 is a diagrammatic horizontal sectional view taken along
line 12--12 of FIG. 11;
FIGS. 13 and 14 are diagrammatic plan views illustrating
asymmetrical light distribution which may be obtained in accordance
with the invention;
FIG. 15 is a diagrammatic horizontal sectional view illustrating a
different manner in which the horizontal light distribution may be
modified;
FIG. 16 is a diagrammatic vertical sectional view illustrating the
manner in which light is reflected from an altered reflector
section; and
FIGS. 17 and 18 are diagrammatic plan views illustrating
symmetrical and asymmetrical light distribution, respectively, in
accordance with the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, FIGS. 1 and 3 illustrate embodiments of
the invention which differ somewhat in appearance but which operate
similarly (with certain exceptions which will be described later).
In the embodiment of FIG. 1 the lighting fixture 10 comprises an
enclosure 12 with an upper section 14, which may be entirely
opaque, and a lower section 16, which may be light-transmitting on
all sides and on the outer portions of the bottom which extend
beyond a base plate 18 on which the fixture is mounted. The base
plate has a tubular depending neck 20 by which the lighting fixture
is supported at the top of a post or pole in a conventional manner.
Although a single lighting fixture is illustrated in FIG. 1, it
will be apparent that a plurality of such fixtures may be supported
upon arms on a single post as disclosed, for example, in my
aforesaid patent. Although a rectangular enclosure is shown, other
configurations, such as circular, may be employed. Suitable
materials for the construction of the lighting fixtures disclosed
herein are well known in the prior art and are set forth, for
example, in my aforesaid prior patent. In the embodiment of FIG. 3
(wherein primed reference characters designate parts corresponding
to those of the embodiment of FIG. 1) the lighting fixture 10' has
an enclosure 12' with an opaque upper section 14' and a
light-transmitting lower section 16'. In this instance, however,
the light-transmitting section of the enclosure does not extend
into the bottom wall of the enclosure, and the enclosure is
supported upon the top of a short post 22' as an extension of the
post, so that the lighting fixture appears to be incorporated into
the post. The post of FIG. 3, including the fixture, may be
approximately 42 inches high, for example, while the post 22 of
FIG. 1 may range in length from approximately 8 feet to
approximately 25 feet, for example.
Turning now to FIG. 5, a lighting fixture 10 is illustrated which,
for purposes of explanation, may be assumed to be the fixture of
FIG. 1, although the basic configuration is applicable to the
fixture of FIG. 3 also. The lighting fixture comprises a first or
upper reflector 24 and a second or lower reflector 26. The lower
reflector 26 is clearly visible in FIG. 1 and its counterpart 26'
is clearly visible in FIG. 3. The upper reflector 24 has a
downwardly facing concave internal reflecting surface 28 which is a
surface of revolution about the vertical axis V--V of the lighting
fixture. In the form shown, the upper reflector has a slight step
30 near its uppermost portion and the lower extremity is flared
outwardly somewhat as shown at 32. The upper reflector may be
termed a collecting reflector, while the lower reflector may be
termed a distributing reflector. The lower reflector has a concave
external reflecting surface 34 which faces upwardly somewhat and
laterally outward. The reflecting surface 34 is also a surface of
revolution about vertical axis V--V. Both reflecting surfaces have
a specular (mirror polish) finish. While the upper reflector has
the general shape of an inverted dish, the lower reflector is
tapered, the upper end of the reflecting surface being closer to
the axis V--V than the lower end. In the form shown, the lower
reflector is tubular and contains a receptacle or socket 36 which
receives a lamp 38.
The lamp, which has its base engaged within the receptacle 36, has
an elongated light source 40, such as an arc tube or an elongated
filament, and has an envelope 42 which may be a passive envelope or
which may itself be light-emitting, as in certain phosphor coated
mercury vapor lamps. As shown in FIG. 5, the elongated light source
40 is aligned with the vertical axis V--V and is surrounded by the
collecting reflector 24. The lighting fixtures of the invention may
be used with almost all lamps commonly employed for outdoor
lighting, such as the "BT" and "E" shaped mercury vapor lamps, "BT"
and "E" shaped metal halide lamps, and "T" shaped high pressure
sodium lamps, "T" shaped quartz lamps and "A" and "PS" shaped
incandescent lamps. These lamps have differing desirable qualities,
such as long life, good lumen maintenance, etc., and it is a
distinct advantage of the invention that the lighting fixtures of
the invention may be employed with all of them.
In general, the lighting fixtures of the invention are designed to
project the greatest amount of light at a high angle relative to
downward vertical and to produce a symmetrical or controlled
asymmetrical light distribution pattern on the ground, with even
illumination over a wide area. The amount of light projected
increases progressively (up to a predetermined angle) as the angle
increases relative to downward vertical. This increase of light
tends to balance the diminution of light reaching the ground caused
by the greater distance traveled at high angles.
As shown in FIG. 5, light from point A at the upper end of the
light source 40 is reflected from the collecting reflector 24 to
the distributing reflector 26, which redirects the light outwardly
and downwardly toward the ground at a predetermined high angle,
such as approximately 67.degree. above downward vertical, as shown
by rays a. The amount of "flash," that is, the length of the image
of the arc tube on the distributing reflector, has good correlation
with the intensity of light projected from the lighting fixture. It
is apparent that at 67.degree. the image of the arc tube, indicated
by the heavy line b is substantially the full length of the
distributing reflector 26, and hence the light from this reflector
at this angle is at its maximum intensity.
Light emitted from point B at the lower end of the light source 40
is also reflected by the collecting reflector 24 to the
distributing reflector 36 and is projected outwardly at a lower
angle, such as approximately 48.degree. relative to downward
vertical, as indicated by rays c. As shown, the image of the arc
tube on the distributing reflector at 48.degree., indicated by the
heavy line d, covers much less than the full length of the
distributing reflector, and hence the light intensity at this angle
is not a maximum. Light emitted from the light source 40 between
points A and B is reflected from collecting reflector 24 to the
distributing reflector 26 and is redirected outwardly by the
distributing reflector at angles which fill in the angles between
67.degree. and 48.degree.. The reduction of image length on the
distributing reflector is progressive as the beam moves from
67.degree. to lower angles, and therefore the intensity of light
projected is reduced in a like manner.
It will be noted that some light coming from point B and striking
the collecting reflector 24 near the open bottom thereof is
directed to the distributing reflector 26 by the flared portion 32
at an angle such that it joins light from point A in being
projected outwardly at 67.degree.. This is characteristic of the
particular construction shown, which may be employed in FIG. 1, but
which need not be employed in all embodiments, as is apparent from
the embodiment of FIGS. 3 and 4. Neglecting the flared portion 32,
it will be noted in FIG. 5 that surface 28 is shaped so that rays
originating at a point of source 40 and reflected by progressively
lower elements of surface 28 impinge upon progressively higher
elements of surface 34, and by virtue of the shape of surface 34
such rays are reflected therefrom outwardly and downwardly along
parallel paths.
Some light is emitted directly from the light source 40 without
striking reflectors. This light has been indicated in FIG. 5 by
rays e and f at 67.degree. and 52.degree., respectively, relative
to downward vertical. More such light is emitted at low angles,
toward 52.degree., than at higher angles, toward 67.degree.. The
amount of light increases as the angle decreases from 67.degree.
until at approximately 52.degree. the amount of light begins to
decrease progressively. If two intensity curves were plotted in a
vertical plane containing the axis V--V, one for reflected light
and the other for light emitted directly from the light source 40,
the two curves would be oppositely directed above 52.degree., the
intensity of the light emitted from the reflectors increasing
progressively above 52.degree. and the intensity of the directly
emitted light decreasing progressively above 52.degree.. Total
intensity of the light emitted at each angle is the sum of the two.
If the number 1.0 represents the full intensity of light per inch
emitted directly from the arc tube and if this number is multiplied
by the length of the arc tube visible between the reflectors at its
maximum (52.degree.), which may be 1.25 inches, the resulting
intensity figure is 1.25. Assuming 80 percent reflector efficiency,
the number 0.64 then indicates the intensity of light per inch
reflected from the collecting and distributing reflectors in
sequence (0.8 .times. 0.8). At its maximum (67.degree.) the image
of the arc tube covers the full length of the distributing
reflector, as noted above, which may be 9 inches long. The
resulting intensity is thus 5.76 (0.64 .times. 9). This confirms
that the light projected by the reflector system contributes much
more intensity than the light emitted directly from the light
source.
The results of the optical system of the invention can be seen in
FIG. 2, which is a candlepower distribution curve, 0.degree. being
downward vertical and 90.degree. being horizontal. Although the
curve is shown only for the quadrant between 0.degree. and
90.degree., the same curve would be obtained in the quadrant
between 0.degree. and -90.degree. (and in any plane containing the
axis of the lighting fixture) due to the symmetrical construction.
The intensity of light is low at 0.degree., toward the bottom of
the pole or post on which the lighting fixture is mounted. From
0.degree. to about 45.degree. most of the light is in fact stray
light, which will be explained later. The intensity climbs steadily
to a maximum at approximately 60.degree. and remains near maximum
until 67.degree., where it rapidly falls off, disappearing
completely at angles which exceed the angle of greatest intensity
by approximately 10.degree. to 15.degree.. Since these higher
angles are the ones at which the fixture will usually be observed,
the result is the total elimination of glare, with only a soft glow
remaining at the fixture for aesthetic purposes. Moreover, the
light distribution on the ground is unusually constant over a wide
area.
If light is emitted only from the elongated light source 40, such
as an arc tube or a filament of the lamp, the reflector system
will, in itself, eliminate glare. Since light emitted from points
low on the arc tube or filament (point B) is distributed at low
angles by the invention and since light emitted from high on the
arc tube or filament (point A) is distributed at high angles by the
invention, the arc tube or filament need only be positioned so that
its upper end is located at the exact point where beam cut-off is
desired. Lamps which emit light only from the arc tube or filament
are the high pressure sodium, metal halide and clear mercury lamps
(arc tube types), and the single end quartz and clear incandescent
lamps (filament types).
The most popular outdoor lamps, however, are the phosphor coated
mercury vapor lamps. While the major position of the light comes
from the arc tube of these lamps as well, the phosphor coating
which covers the entire lamp envelope radiates enough light to
cause considerable glare. It is possible to make the reflector
system large enough so that the arc tube would be in position to
emit maximum intensity at 60.degree. and still have the top of the
lamp envelope occur at the point where beam cut-off is desired.
However, since the compactness of the invention is a major
advantage, this would be undesirable. To eliminate glare without
requiring a larger reflector system the invention employs a glare
baffle 44 (FIG. 5), which may be a horizontal rectangular plate
with a large circular opening centered on the vertical axis V--V
and with the plate material which surrounds the opening
constituting an annulus which protrudes inwardly toward the axis
V--V from the bottom of the collecting reflector 24. The operation
of the glare baffle is illustrated in FIG. 6. The reflector system
is so designed that light rays which are ultimately projected
outwardly at low angles travel between the collecting and
distributing relectors in such a way that they cross at points
relatively close to the vertical axis near the open end of the
collecting reflector, in comparison to rays which are ultimately
projected at higher angles and which cross at points farther from
the vertical axis. Thus, as shown in FIG. 6, rays c1 and c2,
emitted from point B and ultimately projected from the lighting
fixture at low angles, cross over at point D, which is closer to
the axis V--V than the cross-over point E of rays a1 and a2 emitted
from point A. It is a simple matter, therefore, to provide a glare
baffle around the periphery of the collecting reflector 24 which
intrudes just the proper amount to cut off the undesirable highest
angle rays which produce glare (such as light rays g which would be
projected at an angle bove 75.degree. in the embodiment illustrated
in FIG. 6) without in any way diminishing the remaining rays which
produce desirable illumination. It will be noted, of course, that
the construction of the invention is such that no portion of the
lamp is visible at angles above 75.degree..
The manner in which fill-in illumination at angles close to
downward vertical is achieved will now be described with reference
to FIGS. 4 and 7. Referring first to FIG. 7, which represents the
embodiment of FIG. 1, that is, a lighting fixture mounted high on a
pole, it will be recalled that the light-transmitting section 16 of
the enclosure extends into the bottom wall beneath the fixture.
Light coming directly from the lamp 38, either from the envelope 42
or the light source 40, is intercepted by the side wall of the
light-transmitting enclosure section 16 at a low angle,
approximately 18.degree. with a phosphor coated lamp and
approximately 28.degree. with a clear lamp, as indicated by the
rays h and i, respectively. Stray light from the upper reflector 24
extends down at an angle of approximately 8.degree. with respect to
downward vertical, as indicated by ray j. Light rays such as ray j
pass directly through the light-transmitting section at the bottom
of the enclosure, while light rays such as rays i and h strike the
inner surface of the enclosure at such a low angle of incidence
that the inner surface of the enclosure acts as a reflector and
redirects some of this light toward and even beyond the vertical
axis, as indicated by dashed portions of the rays, thereby
providing fill-in illumination for the area beneath the lighting
fixture. Since the inner surface of the enclosure receives light
rays at many different angles, it is not necessary that the sides
of the enclosure be vertical for proper operation, and the side
walls may be flared, for example.
In the smaller embodiment of FIGS. 3 and 4, where, for aesthetic
reasons, the light-transmitting section of the enclosure does not
extend inwardly beneath the fixture, rays such as rays h and i in
FIG. 7 cannot be directed inwardly toward the vertical axis.
However, there is still some fill-in illumination as indicated by
rays k and l in FIG. 4 emitted directly from the lamp envelope 42
and by reflection from the collecting reflector 24, for example.
Since the lighting fixture of FIGS. 3 and 4 is supported quite
close to the ground, the dark circle extends only about seven
inches beyond the base of the post and is not objectionable. Also,
in the smaller embodiment greatest beam intensity occurs at about
80.degree. relative to downward vertical, and the beam disappears
at slightly below 90.degree..
Since the reflector system is circular in its horizontal
cross-section, the pattern of light projected on the ground will
ordinarily be symmetrical about the vertical axis. Although
asymmetrical patterns could be achieved by blocking out light from
various portions of the collecting reflector, either by extending
areas of the glare baffle inwardly or by simply painting sections
of the collecting reflector black, for example, such methods would
create asymmetry by diminishing illumination in certain areas
without increasing it in other areas. Light would thus be wasted.
Asymmetry could also be achieved by changing the contour angle of
selected sections of the distributing reflector, but since this
reflector is visible to the observer, an obvious change of this
sort has aesthetic disadvantages. Also, such a change would leave
the amount of light emitted toward the distributing reflector in
radial planes the same in all directions, rather than increasing
the amount of light in the direction of the longest throw. FIG. 12
illustrates a better solution to this problem, the figure being a
horizontal cross-section taken through the lamp and collecting
reflector as indicated in FIG. 11. Light striking the concentric
surface of the collecting reflector is reflected directly back to
the distributing reflector in a radial plane and from there is
projected outward in the same plane. This is indicated
diagrammatically by ray m. If, however, a section of the collecting
reflector is altered, so that it is not concentric with the lamp
and the distributing reflector, as indicated by section 46, light
rays striking this surface will be reflected in non-radial planes
toward the distributing reflector and from the distributing
reflector will be projected outwardly in non-radial planes. This is
indicated by the rays n and o. As shown in FIG. 12, this will
increase the amount of light thrown in some directions and decrease
it in others. Arc G designates the area of unaffected illumination,
arc H the area of reinforced illumination, arc I the area of
reduced illumination, and arc J the area of relatively unaffected
illumination. Ray p designates the distribution from the unaltered
reflector, which may be compared with ray n. The proper placement
of the altered (non-concentric) reflector sections will create
asymmetrical distribution patterns as indicated in FIGS. 13 and 14,
for example. Since the vertical contour of the collecting reflector
is not changed in any way, the glare cut-off characteristics and
vertical distribution angles will not be affected. Only the amount
of light thrown outward will vary from one direction to
another.
If light were coming only from the arc tube and if the altered
reflector section were a perfectly specular mirror, it is apparent
that the outside area which is designated by arc I in FIG. 12 would
in fact receive no illumination at all. This could be undesirable.
When phosphor coated mercury vapor lamps are used, this problem
does not exist, since enough light is radiated from the coating on
the lamp to produce the necessary fill light in the affected area.
When a non-coated lamp (such as metal halide, high pressure sodium,
etc.) is used, the non-concentric reflector sections can be given a
semi-diffuse reflector finish, so that the major portion of the
light will follow the direction imparted by a specular finish, but
enough stray (diffused) light will be created to fill in the
affected area.
A further technique for achieving asymmetric light distribution in
a horizontal plane will now be explained with reference to FIGS. 15
- 18. In this embodiment non-concentric sections of the collecting
reflector are also employed. However, these sections are so
angulated that light rays reflected from them bypass the
distributing reflector and are sent directly toward the gound. The
technique will be described in its application to a pole-mounted
street illumination fixture, but it will be apparent that there are
many other applications also.
FIG. 17 illustrates the usual symmetrical light distribution
produced on the ground surrounding a pole K when the concentric
reflector arrangement of the invention is not modified. FIG. 18
illustrates an asymmetrical light distribution (shown superimposed
on a symmetrical distribution for comparison) which may be produced
in a manner described hereinafter. It will be noted that FIGS. 17
and 18 are divided by orthogonal lines L and M radiating from the
pole K, line L being parallel to a typical roadway (so-labeled) at
one side of the line, and line M being perpendicular to the
roadway. Lines L and M are also indicated in FIG. 15.
Referring now to FIG. 15, it will be noted that there are two
non-concentric sections 46' and 46" of the collecting reflector.
Sections 46' and 46" are oppositely angulated in a horizontal plane
with respect to line M, and since the sections and their
orientation are identical, except for the opposite angulation, a
description of the operation of section 46' will suffice for both.
The non-concentric orientation of section 46' in a horizontal plane
causes rays such as q and r emanating from the arc tube 40 and
reflected from section 46' to be reflected past the distributing
reflector 26 at one side thereof. Rays will be similarly reflected
from section 46" at the opposite side of the distributing
reflector, so that two beams of light are projected toward the
street side of line L at opposite sides of line M. Each beam
extends from approximately 13.degree. to approximately 40.degree.
from line L and diminishes fairly rapidly beyond these angles.
FIG. 16 illustrates light rays of one of the beams in a vertical
plane. With the non-concentric reflector section 46' of the height
shown, the beam extends from approximately 50.degree. up to
approximately 75.degree. from downward vertical. It is apparent
that if the reflector section 46' were taller, the beam would
extend to an angle lower than 50.degree..
From FIGS. 15 and 16 it is apparent that glare cut-off is still
produced by the glare baffle, the leading and following edges of
which are indicated at 44A and 44B. Also, the top edge 26A of the
distributing reflector assists in producing glare cut-off as
indicated in FIG. 16. For ray q of FIG. 15 cut-off occurs at
approximately 75.degree. from downward vertical. For ray r of FIG.
15, cut-off occurs at slightly over 75.degree.. Rays q and r are
also illustrated on the isolux curve of FIG. 18.
As shown in FIG. 18, the basic symmetrical distribution is altered
to create a relatively long rectangular pattern on the street side.
Since light was taken from the house side to create the additional
beams referred to above, the distribution is reduced at the house
side.
FIG. 18 also illustrates a 75.degree. cut-off line. This line is
established by determining the point at which a ray at 75.degree.
with respect to downward vertical would strike the ground along
line L. From this point the 75.degree. cut-off line is drawn
perpendicular to the roadway. Glare cut-off angle is determined by
this line (rather than a radial one) for roadway luminaires.
Although cut-off occurs at slightly over 75.degree. for ray r, the
ray will still strike the ground within the 75.degree. cut-off
line.
The mechanical construction of a practical form of the invention,
corresponding to FIG. 1 but largely applicable to FIG. 3 also, is
illustrated in FIG. 8, the view being taken along line 8--8 of the
bottom view of FIG. 9. The outer configuration is only one of many
possible configurations, which may range from contemporary to
traditional lantern shapes, for example, all of which may employ
the same optical system. The tubular neck 20 of the base plate 18
supports the entire fixture. An inverted cup-shaped base 48 has a
skirt 50 which may be secured to the base plate 18 by screws 52,
the periphery of the skirt 50 being flared upwardly and outwardly
to engage and support the bottom of the distributing reflector 26.
A structural tube 54 is supported upon the top of base 48, being
secured thereto by screws 56, and has an open upper end which
projects from the top of the distributing reflector 26. A lamp
receptable or socket 58 is mounted on a sleeve 60 which has a
reduced diameter portion extending downwardly through openings in
the bottom of tube 54 and the top of base 48. A helical compression
spring 62 surrounds the lower portion of sleeve 60 and is held
captive between washers 64 and 66, washer 64 abutting the top of
base 48 and washer 66 being supported on a nut 68 threaded onto the
bottom of sleeve 60. The spring biases receptacle 58 downwardly.
When the lamp 38 is engaged with the receptacle 58, as by being
threaded therein, the socket 58 is drawn upwardly, spring 62 being
compressed, and the shoulder of the lamp envelope is drawn
downwardly upon a circular ring seat 70 provided at the top of tube
54. This centering ring seat and a further centering ring 72, which
surrounds the receptacle 58 and guides the reciprocative movement
of the receptacle within the tube 54, ensure that the lamp 38 is
properly positioned relative to the reflector system. Although the
lamp is shown base down in FIG. 8, it may be supported base up as
indicated in FIG. 10. In this embodiment the socket 58' is again
spring-loaded in a downward direction, by springs 62', and the top
of the lamp is held against the seat 70, which centers the lamp and
holds it vertical. In this case the seat presses the spring-loaded
lamp up into position when the hinged or removable top wall of the
enclosure is closed. In all other respects the construction is the
same as FIG. 8.
Four horizontal supporting arms 74 (see FIGS. 1 and 8) have their
inner ends attached to a ring 75 fixed about the upper end of tube
54. The arms radiate from the tube, and their outer ends support
the upper portion of the fixture, including the glare baffle 44,
the collecting reflector 24, and the upper section 14 of the
enclosure 12. The portions of the arms spanning the space between
tube 54 and glare baffle 44 have small thickness relative to
height, so that the arms have the appearance of vertical fins,
which have adequate structural strength without significantly
interrupting optical paths. The outer ends of the arms fit into
notches in the glare baffle and have portions bent horizontally to
receive screws 75a which fix the glare baffle to the arms. Screws
75b and 75c fix the collecting reflector to the glare baffle and
the upper enclosure section 14 to the glare baffle, respectively.
When the lighting fixture is to be mounted upon a high pole, the
arms preferably have a highly specular finish similar to the
collecting reflector 24, so that they are almost invisible when
viewed at normal angles (from below). When the fixture is mounted
on a short post, below eye level, the arms may simply be painted
black. Since the upper portion of the lighting fixture is supported
upon and connected to the neck 20 by the structural tube and arm
assembly, the light-transmitting enclosure section 16 may simply
float, without structural strain, between upper and lower cushions
76 and 78, the bottom wall being positioned by screws 75d passing
therethrough and threaded into base 48. This is highly
advantageous, because the light-transmitting enclosure section is
normally the weakest part of the lighting fixture. If this section
is shattered, the upper portion of the lighting fixture will still
be supported.
The collecting reflector 24 is preferably constructed in two
sections, with an upper section 80 being removable from the
remaining lower section of the reflector and spring-biased toward
it by means of compression springs 82, so that the upper section
rests firmly against the lower section when in place. The upper
section 80 may have a cupped portion 84 depending from a plate 86,
screws 88 passing loosely through plate 86 and being threaded into
bosses of the top wall 90 of the enclosure 12. The top wall 90 is
removably attached to the side walls of the upper section 14 of the
enclosure by means of conventional fasteners 92. To gain access to
the lamp, the top wall is removed or opened, lifting with it the
upper section 80 of the collecting reflector, so that the lamp 38
is exposed through the hole at the top of the collecting reflector
resulting from the removal of upper section 80. Weatherproofing
and/or cushioning gaskets may be provided as indicated at 94, 96,
98, 100 and 102, for example, in addition to those mentioned
previously.
While preferred embodiments of the invention have been shown and
described, it will be apparent to those skilled in the art that
changes can be made in these embodiments without departing from the
principles and spirit of the invention, the scope of which is
defined in the appended claims.
* * * * *