U.S. patent number 3,591,798 [Application Number 04/772,903] was granted by the patent office on 1971-07-06 for lighting fixture.
This patent grant is currently assigned to Lightolier Incorporated. Invention is credited to Noel S. Florence.
United States Patent |
3,591,798 |
Florence |
July 6, 1971 |
LIGHTING FIXTURE
Abstract
A lighting fixture comprising a pair of parallel vertically
aligned fluorescent lamps positioned midway between two elongated
specular reflecting surfaces each of which is substantially
parabolic in curvature. The reflecting surfaces are arranged with
respect to the lamps so that the major portion of the illumination
provided by the fixture will be projected therefrom at an angle
greater than 30.degree. with respect to the vertical so as to
minimize the veiling reflections effect to a viewer whose working
surface is illuminated by such fixture.
Inventors: |
Florence; Noel S. (Cranford,
NJ) |
Assignee: |
Lightolier Incorporated (Jersey
City, NJ)
|
Family
ID: |
25096580 |
Appl.
No.: |
04/772,903 |
Filed: |
November 4, 1968 |
Current U.S.
Class: |
362/225 |
Current CPC
Class: |
F21V
7/06 (20130101); F21V 11/02 (20130101); F21S
8/026 (20130101); F21S 2/00 (20130101); F21V
7/005 (20130101); F21Y 2103/00 (20130101); F21Y
2113/00 (20130101) |
Current International
Class: |
F21V
7/06 (20060101); F21V 7/00 (20060101); F21S
8/02 (20060101); F21V 11/00 (20060101); F21V
11/02 (20060101); H05b 033/02 () |
Field of
Search: |
;240/9,9A,51.11,41.35,41.37 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Horan; John M.
Assistant Examiner: Sheer; Richard M.
Claims
Having thus described my invention, what I claim as new and desire
to secure by Letters Patent of the United States is:
1. A lighting fixture comprising an elongated inverted
trough-shaped housing having two opposed elongated specular
reflecting surfaces, means in said housing for supporting a pair of
elongated fluorescent lamps to extend longitudinally of said
housing parallel to each other and in juxtaposed vertical
alignment, said lamps being positioned midway between said pair of
specular reflecting surfaces, each of said specular reflecting
surfaces being substantially parabolic in curvature, an arcuate
reflector positioned over the uppermost lamp and extending
substantially the length thereof midway between the two
substantially parabolic specular reflecting surfaces, the
longitudinal edges of the arcuate reflector being positioned with
respect to the curved surfaces of the parabolic reflectors to
permit impingement of light rays from the lamps against only that
portion of the curved surface of each of the parabolic reflectors
which will reflect light therefrom in convergent rays, whereby the
greater portion of the total illumination provided by said fixture
will be emitted within a 30.degree. to 60.degree. zone with respect
to the vertical.
2. The combination set forth in claim 1 in which each of said
opposed specular reflecting surfaces has an optical curve that lies
between two parabolic curves having axis of 25.degree. and
45.degree. respectively with respect to the vertical, each of said
parabolic curves having its focus at a point positioned
substantially midway between said lamps.
3. The combination set forth in claim 2 in which each focal point
is positioned substantially midway between a line tangent to the
outer surface of both of said vertically disposed lamps and a line
extending through the axes of said lamps.
4. The combination set forth in claim 1 in which said arcuate
reflector has as its focus the longitudinal axis of the lowermost
lamp of said pair.
5. The combination set forth in claim 1 in which each of said
opposed specular reflecting surfaces has an axis of substantially
35.degree. with respect to the vertical.
Description
As conducive to an understanding of the invention, it is noted that
the normal viewing angle of a person sitting at a desk, is from
0.degree. to 30.degree. from the vertical. As a result, where the
light from a source of illumination strikes the working surface at
an angle such that it will be reflected from the working surface at
an angle of from 0.degree. to 30.degree., it is apparent that such
reflected light will be within the normal viewing range and hence
may be reflected directly into the eyes of the viewer. As a result
of such reflection, known as "veiling reflection," contrast between
say black printed type on a paper and the white background will be
reduced, making the type more difficult to read and being tiring to
the eyes. This effect is more noticeable with glossy paper but also
exists with printing or pencil on matte paper.
It is possible to avoid such veiling reflections from one or two
luminaires by locating them with respect to the task so that no
rays due to specular reflections of the luminaires in the task will
emanate from the task in the direction of the eyes of the
worker.
However, since in most cases work is performed in rooms or chambers
with a multiplicity of regularly spaced lighting fixtures or
luminaires, it is likely that one or more of the luminaires will be
in a location which will cause veiling reflections.
It is accordingly among the objects of the invention to provide a
luminaire which may be readily fabricated at relatively low cost,
which will be of substantially standard size, using standard
available fluorescent lamps and which will control the light
emitted therefrom in such manner that only a relatively small
portion of the total available illumination therefrom will be
emitted at angles which could produce veiling reflections,
regardless of the position of the worker in the room in which the
luminaires are installed.
Another object of the invention is to provide a lighting fixture
with very low brightness at normal viewing angles and from which
more than 60.degree. of the total light output will be emitted at
angles of from 30.degree. to 60.degree. from the vertical.
Another object is to provide a lighting fixture which may form part
of an installation of a plurality of identical fixtures for use in
a room or chamber and which installation will provide an overall
illumination of desired intensity for office work in all areas of
the room with minimum veiling reflection effect being experienced
by the workers in any portion thereof.
According to the invention, these objects are accomplished by
providing a lighting fixture consisting of two elongated juxtaposed
fluorescent lamps extending parallel to each other in vertical
alignment, in association with specular reflectors so arranged that
the majority of the light emitted by said lamps will be reflected
by said reflectors at an angle greater than 30.degree.. More
particularly, the specular reflectors are positioned on each side
of the longitudinally extending lamps and extend parallel thereto,
each of said specular reflectors having substantially a parabolic
curved surface having its focus at a point substantially midway
between the two lamps and midway between a line tangent to the
outer surfaces of the juxtaposed lamps and a line extending through
the axes of said lamps with the axis of each of said parabolas
being at an angle of between 25.degree. and 45.degree..
In a preferred embodiment of the invention there is associated with
said fluorescent lamps and positioned above the uppermost lamp an
elongated reflector, arcuate in cross section having as its focus
the longitudinal axis of the lowermost lamp, whereby light rays
emitted by said lamps will be substantially directed back into said
lamps to reinforce the brightness thereof, particularly at the foci
of said parabolic reflectors.
In the accompanying drawings in which is shown one or more of
various possible embodiments of the several features of the
invention,
FIG. 1 is a longitudinal sectional view taken along line 1-1 of
FIG. 2;
FIG. 2 is a transverse sectional view taken along line 2-2 of FIG.
1;
FIG. 3 is a perspective view of a baffle member used in the
embodiment of FIGS. 1 and 2;
FIGS. 4, 5 and 6 are diagrammatic views illustrating the angles of
light rays from the lamps of the embodiment shown;
FIG. 7 is a diagrammatic view of an installation using a plurality
of lighting fixtures according to the invention, and
FIG. 8 is a diagrammatic view of another embodiment of the
invention.
Referring now to the drawings, as shown in FIGS. 1 and 2, the
lighting fixture, according to the invention, comprises an
elongated, inverted troughlike housing 11 having end walls 12 to
each of which is secured a pair of vertically aligned sockets 13 to
mount the ends of a pair of elongated fluorescent lamps 14 and 15,
said lamp thus extending longitudinally of the housing 11 parallel
to each other and in juxtaposed vertical alignment.
The longitudinal edges of the housing adjacent its mouth 16 are
bent outwardly as shown at 17 to permit mounting of the fixture in
conventional manner in a suitable rectangular opening provided by
ceiling members 18 in a ceiling 19.
Preferably, the housing 11 is designed to fit in a standard 1 foot
by 4 foot opening and the fixture is designed to carry two standard
40 watt fluorescent lamps.
The housing illustratively has secured to one of the end walls 12
thereof a container 21 in which a conventional ballast is
positioned.
As the electrical connections for the fixture are conventional,
they will not be further described.
As is shown in the drawings, and particularly FIG. 2 thereof, the
housing in cross section has a flat top wall 22 with two outwardly
inclined sidewalls 23, the lower ends of the latter having
outwardly extending flanges 24 from which depend sidewalls 25.
Positioned in the portion of the housing between the lower
sidewalls 25 thereof is a baffle member 26 which is designed to be
readily displaceable to permit relamping of the fixture.
As shown in FIG. 3, for example, the baffle member 26 comprises a
pair of parallel curved specular reflector sidewalls 27 between
which extend a plurality of spaced parallel louvers 28.
Each of the louvers 28, as is clearly shown in FIG. 1, has a wide
top surface 29 and a narrow bottom edge 31 with the opposed faces
32 of each louver formed as a substantially parabolic specular
reflector.
As shown in FIGS. 2 and 3, a hinge member 33 is provided at the end
of the lower edge of each of the sidewalls 27 of the baffle member
26. Each hinge illustratively comprises an L-shaped member having
one leg 33' slidably mounted in a suitable support 34 carried by
the sidewalls 27. To mount the baffle member in the housing, it is
merely necessary to position the baffle member between the
sidewalls 25 of the housing and move the hinge members outwardly so
that the slidable legs 33' thereof will enter the corresponding
opening in the end walls 12 of the housing. For purposes of
relamping, it is merely necessary to retract the legs 33' carried
by one of the sidewalls 27 of the baffle member, so that the latter
will pivot downwardly, being supported by the legs 33' on the other
sidewall 27.
According to the invention there is positioned between the
sidewalls 23 of the housing 11 a pair of elongated curved specular
reflector members 41. The reflector members 41 preferably extend
the entire length of the housing and are secured at their upper and
lower longitudinal edges as at 43, 44 to the top wall 22 and the
flanges 24 in any suitable manner such as by screwing, welding or
the like.
Positioned directly over the upper fluorescent lamp 14 is an
elongated specular reflector 45 which is secured to the top wall of
the housing as at 46 in any suitable manner.
The reflectors 41 which are symmetrically disposed on each side of
the lamps 14 and 15 are substantially parabolic in curvature, each
having its focus at point F which is substantially midway between
the lamps 14, 15 and midway between a line that is tangent to the
outer surface of the lamps and a line extending through the axes of
said lamps.
The axis of each parabolic reflector 41 is at an angle of between
25.degree. and 45.degree. from the vertical and preferably at an
angle of 35.degree.. Thus, each of the parabolic reflectors 41 will
reflect light originating at the focus F in a direction parallel to
the axis of each reflector and hence at an angle of 35.degree. in
the preferred embodiment herein described. However, it is within
the scope of the invention to utilize reflectors having optical
curves that lie between two parabolic curves having axes of
25.degree. and 45.degree. respectively with each of said parabolic
curves having its focus at a point positioned substantially midway
between said lamps.
The sidewalls 27 of the baffle 26 also have a curvature which is
substantially parabolic and forms a continuation of the parabolic
curve of the reflectors 41.
The reflector 45 is radially curved, having its origin or focus at
the longitudinal axis C of the lower lamp 15.
As the result of the provision of the curved reflector 45, since
the light from the lower lamp 14 tends to be reflected back by the
reflector 45, there is an increased surface brightness at the
region adjacent the focus F of each of the parabolic reflectors 41
which will be projected against the opposed reflectors 41 for
subsequent reflection thereby.
With the arrangement above described, and referring to FIGS. 4, 5
and 6, for example, it is apparent that the light emanating from
the focus F will be reflected from say the lower portion of the
parabolic reflector (FIG. 4) defined by the sidewall 27 at an angle
of 35.degree. as at I (since the axis of the parabola is at
35.degree.) and from the outer edges of the upper and lower lamps
14 and 15 at angles of say 30.degree. and at 50.degree. as at II
and III.
Referring to FIG. 5, the light emanating from the focus F will be
reflected from the lower portion of reflectors 41 at an angle of
35.degree. as at I' and from the outer edges of the lamps 14 and 15
at angles of say 24.degree. and 55.degree. as at II' and III'.
Referring to FIG. 6, the light emanating from the focus F will be
reflected from the upper portion of reflectors 41 at an angle of
35.degree. as at I" and the light emanating from the lower lamp 15
will be reflected first by reflector 41 to the lower reflector 27
and then reflected at an angle of say 51.degree. as at III". It is
apparent that the major portion of the light transmitted by the
parabolic reflectors 41 and 27 will be between the angles of
24.degree. and 55.degree. with most of the light being at an angle
greater than 30.degree. but less than 60.degree..
As a result of photometric distribution tests of a typical fixture
of the type above described, the following has been found.
In the 0.degree. to 30.degree. zone measured from the vertical
there is emitted approximately 37 percent of the total light
emitted by the fixture. In the 30.degree. to 60.degree. zone there
is emitted approximately 61 percent of the total light emitted by
the fixture and in the 60.degree. to 90.degree. zone there is
emitted approximately 2 percent of the total light emitted by the
fixture.
As previously noted, it has been found that conventionally a worker
sitting at desk views the work surface at angles between 0.degree.
and 30.degree. with respect to the vertical. Where the work surface
is illuminated by rays of light that are within this region of from
0.degree. to 30.degree., "veiling reflections" may be created,
i.e., there may be reflections of one or more luminaires in the
viewing task. This causes the contrast between the detail in the
task, a printed letter, for example, and the white background of
the paper to be reduced, making it much harder to read and tiring
the eyes of the viewer.
It is apparent from the foregoing description of the lighting
fixture herein, that with respect to each fixture the maximum
portion of the light produced by the fixture will be emitted at an
angle from vertical of between 30.degree. and 60.degree., i.e., at
an angle greater than the normal task viewing angle of from
0.degree. to 30.degree.. Hence, with respect to the total light
emitted from any one fixture, only a relatively small portion of
such light, i.e., approximately 37 percent thereof; as above
illustratively described, will be illuminating the task at angles
likely to cause veiling reflections.
The fixture according to the present invention, is designed for use
in a relatively large area in which a plurality of the fixtures
will be used. A typical installation is diagrammatically shown in
FIG. 7.
Thus, for example, a room or chamber may contain four fixtures 11a,
11b, 11c and 11d. Referring to the fixtures 11b and 11c, for
example, the regions R of light from each of such fixtures will
have approximately 37 percent of the total light emitted by the
associated fixture.
With respect to any work being performed at a desk in said room,
say one directly beneath the fixture 11b, it is apparent that there
will be illumination provided within the region R from fixture 11b
which will strike the desk at an angle of from 0.degree. to
30.degree.. Hence, such illumination may produce veiling
reflections. However, there will also be illumination from the
adjacent fixtures 11a and 11c which will strike the desk beneath
fixture 11b at an angle greater than 30.degree. so that there will
be no veiling reflections, caused by the light from the adjacent
fixtures, on such desk.
Due to the fact that a greater proportion of the illumination
falling on the desk of the viewer will be at angles which will not
cause veiling reflections, such reflections will be minimized, thus
increasing the task contrast ratios and thereby providing a much
more effective type of illumination.
It is further to be noted that since only a small portion of the
light emanating from each of the fixtures is at an angle greater
than 60.degree., a person standing or seated in the room will not
be subjected to direct glare when viewing the fixture in direction
at right angles to its length. By reason of the transverse louvers
28 carried by the baffle member, direct light from each fixture to
the viewer, longitudinally of the length thereof, will also be
minimized in manner common with transverse louvers.
With the relatively simple construction above described, a
relatively low cost lighting fixture is provided which may readily
form part of a complete installation for a room or chamber and
which will provide effective illumination for office viewing tasks
in substantially all portions of such chamber with a substantial
reduction of veiling reflections, thus increasing the contrast
ratio of the tasks and improving visual perception of such tasks
throughout the room.
By reason of the use of two elongated fluorescent lamps, the
stroboscopic effect caused when only one lamp is used is
eliminated. The use of the two vertically superimposed lamps
provides the desired overall light intensity required with a bright
zone at a desired location to produce the maximum efficiency.
It is within the scope of the invention where further reduction of
veiling reflection is desired to provide an arcuate baffle or
shield 50 directly beneath the lower lamp 15 as shown in FIG. 8.
This shield which illustratively is opaque will substantially
reduce direct downward rays and hence further reduce the amount of
light in the 0.degree. to 30.degree. zone.
Although such opaque baffle 50 will somewhat decrease the
efficiency of each fixture, where there are sufficient fixtures
available in a room, such decrease may not be critical and can be
balanced against the desirability of having a minimum percentage of
the illumination from each fixture within the undesirable range of
from 0.degree. to 30.degree..
As many changes could be made in the above constructions, and many
apparently widely different embodiments of this invention could be
made without departing from the scope of the claims, it is intended
that all matter contained in the above description or shown in the
accompanying drawings shall be interpreted as illustrative and not
in a limiting sense.
* * * * *