Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to high-intensity discharge
lamps, and particularly, to high-intensity mercury and metal
halide lamps.
b) Problems in the Art
High-intensity discharge or arc lamps such as mercury lamps
and metal halide lamps represent an efficient, high-intensity
source of light, particularly for high-intensity, large quantity,
or large area of lighting. There are different types of arc
lamps in general, and mercury and metal halide arc lamps in
particular, such as are available from a wide variety of
manufacturers and distributors.
Conventional lamps of this type generally consist of a
mounting apparatus, such as a screw-end or threaded end, an arc
tube, electrical connections connected between the screw-end and
the arc tube, and a glass jacket, outer envelope, or bulb
surrounding the arc tube and at least some of the electrical
connections.
As can be appreciated, and as is known to those of. ordinary
skill in the art, the arc tube is generally an elongated envelope
made of quartz or some other high-temperature resistant yet
substantially transparent material. The arc tube thus generally
has a longitudinal axis which is generally aligned along the
longitudinal axis of the entire arc lamp, which in the case of an
arc lamp with a threaded end, extends between the screw-end and
the opposite end of the lamp.
The arc tube is generally evacuated of air and is loaded
with chemicals, including mercury or metal halides in mercury and
metal halide lamps, which facilitate creation of a high-intensity
light discharge arc between electrodes which extend into the arc
tube, when electricity is applied to the electrodes. The bulb is
also usually evacuated to provide temperature insulation and to
provide protection to the arc tube.
Because the arc tube of such conventional arc lamps is
aligned along the longitudinal axis of the arc lamp, the lighting
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characteristics of these conventional arc lamps are somewhat
uniform. Most of the light emanating from such an arc tube does
so laterally (perpendicularly from the longitudinal axis), with a
much less significant amount of light emanating from the arc
tube's opposite ends. The light pattern which is emitted from
these conventional arc lamps, while being somewhat consistent
between conventional arc lamps, does lack flexibility and can
present limitation as to the light pattern radiated from the
lamp.
In most lighting applications, reflectors or reflecting
elements are utilized to alter the light pattern emanating from
the lamp. Hemispherical reflectors which are symmetrical around
the longitudinal axis of the arc lamp are a conventional choice.
The arc lamp is screwed into a socket and seats within the
reflector so that its outer end points to the lighting target.
Therefore, a substantial amount of the light emanating from the
lamp and reflector combination is reflected light originally
emanating from the sides of the arc tube, gathered in the
reflector, and then redirected.
It is well known that direct light is more efficient than
reflected light. Any reflection results in some light loss. A
conventional arc lamp having the arc tube aligned along the
lamp's longitudinal axis, and positioned in a conventional
symmetrical reflector, results in a significant amount of light
loss.
Furthermore, there is an effect which is known as "tilt
factor" which can reduce the efficacy (lumens per watt) of metal
halide or mercury arc lamps. An arc lamp operates with the
highest efficacy when the arc tube is positioned vertically. The
next best positioning of an arc tube as far as efficacy is
concerned would be when the arc tube is horizontal. High
temperatures during operation of an arc lamp cause evaporation of
chemicals within the arc tube which in turn causes the gas
discharge which emits light. If there is uneven heating within
the arc tube, which renders some locations sufficiently cooler
from others, the efficacy of the lamp will decrease. Chemicals
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may condense out blocking light from emanating from the arc tube.
Precipitation of these essential chemicals also means that they
will not be discharging light.
Therefore, traditionally, these arc lamps have been desired
to be installed and operated in a directly vertical fashion.
Since the arc tube is aligned along the longitudinal axis of the
lamp, and the aiming axis of the lamp is vertical, optimal
~::i.cacy is achieved. U.S. Patent No. 4,341,975, by Phillipp, et
al., entitled "Jacketed Lamp Having Transversely Mounted Arc
Tube", issued July 27, 1982, discusses this phenomenum. In that
patent, it is recognized that arc lamps are not always desired to
be positioned in a directly vertical orientation. The Phillipp
patent therefore presents a method by which the bulb of the arc
lamp can be positioned horizontally, and yet the arc tube itself
is positioned vertically for optimal efficacy.
In many lighting applications, however, the aiming direction
of the arc lamp is other than completely vertical or completely
horizontal. In those conditions, a conventional mercury or metal
halide arc lamp with the arc tube aligned along the longitudinal
axis, loses efficacy. Because heat rises, tilting of the arc
tube between horizontal and vertical (in any direction), will
cause hotter areas to develop at the highest point of the arc
tube, generally along the top of the arc tube. In turn, cooler
areas will develop at the lowest points, generally along the
lower part of the arc tube. These temperature differences, even
though the overall temperature through and surrounding the arc
tube is quite high, can cause precipitation of some of the loaded
chemicals inside the arc tube. Such precipitation will cause
clouding and blockage of light, and of course, will also make
less chemical available for production of the arc stream, which
will also contribute to a reduction in the amount of light
possible from the arc lamp. Other detrimental results can be
drops in wattage of the lamp of, for example, three or four
percent, and pressure changes in the lamp; all of which can
~3dversely affect the consumption of power by the lamp, making it
less efficient and less economical.
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This problem is called the "tilt factor". If a conventional
mercury or metal halide arc lamp is tilted below horizontal,
generally between 0 and 45~ below horizontal, the tilt factor
results in light output loss of up to 20~.
Therefore, there is a lack of flexibility in such arc lamps
having the arc tube aligned directly along the longitudinal axis
of the arc lamp. Furthermore, conventional such arc lamps suffer
from the tilt factor, which can produce serious efficiency and
efficacy problems.
It is therefore a principal object of the present invention
to provide a tilted arc discharge lamp which can increase
efficacy or light output, efficiency, and flexibility of use of
an arc lamp to improve upon or solve deficiencies and problems in
the art.
A further object of the present invention is to provide a
lamp as above described with respect to mercury and metal halide
lamps which can be utilized to solve tilt factor problems, light
direction problems and other lighting deficiencies or
limitations.
A further object of the present invention is to provide a
lamp as above described which can be utilized in existing bulbs
or glass jackets and screw-in mounts.
Another object of the present invention is to provide a lamp
as above described which can be advantageously combined with
reflector assemblies to increase the amount of light and allow
improved flexibility in directing light.
A further object of the present invention is to provide a
lamp as above described which is efficient, and economical to
manufacture, install, and maintain.
These and other objects features and advantages of the
present invention will become more apparent with reference to the
accompanying drawings and specification.
SU1~MARY OF THE INVENTION
The present invention consists of a conventional glass
envelope, outer jacket, or bulb, with a conventional screw-in
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threaded mount. A conventional arc tube has connections adapted
for operative connection to electrical power, such as is known in
the art. The arc tube inside the bulb is, however, tilted or
offset from the longitudinal axis of the arc lamp. By moving the
arc tube off of the longitudinal axis, significant changes in the
light pattern emanating from the arc lamp are achieved. For
example, more direct light would emanate from the front of the
':,a1_u, than when the arc tube is aligned along the longitudinal
axis, if the arc lamp is angularly tilted from the longitudinal
axis of the arc lamp.
The tilt or offset from the longitudinal axis can be of any
degree. The amount can be selected to achieve various effects.
Furthermore, the tilting or offset can drastically change
the operation of the arc lamp when used in conjunction with a
reflector. because the emanating light pattern from either an
offset or a tilted arc tube is different from conventional lamps,
different composite light output from the tilted arc lamp and
reflector will be achieved. Depending on the position of the arc
tube and the type of reflector, a greater amount of light can be
directly sent to the target area. Additionally, a greater amount
of light may be able to be captured and reflected by the
reflector to the target area, rather than having it be
misdirected or spilled into areas out of the target area.
Still further, the tilt or offset of the arc lamp can be
matched with the angled orientation of the arc lamp so that the
arc tube can be horizontally or vertically positioned to reduce
any tilt factor in mercury or metal halide lamps, In other
words, if the longitudinal axis of the lamp, when installed, is
50~ up from vertical, the arc tube can be tilted fram that
longitudinal axis 40~ so that it is generally horizontal.
Although the aiming axis of the bulb would be angled downwardly,
the arc tube would be horizontal, more light would directly
emanate along the aiming axis of the bulb, and any tilt factor
would be greatly reduced. Alternatively, the arc tube could be
~i:ilted off the longitudinal axis of the arc lamp so that it is
operated in a vertical orientation, even though the arc lamp is
not vertically oriented.
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Brief Description of the Drawings
Figure 1 is a side view showing one embodiment of the
invention where the arc tube is tilted from the longitudinal axis
of the arc lamp.
Figures 2 and 3 are similar side views showing different
amounts of tilt of the arc tube from the longitudinal axis of the
arc lamp.
Figure 4 is a similar side view showing an arc tube offset
so that its longitudinal axis is generally parallel to the
longitudinal axis of the arc lamp.
Figure 5 is a similar side view showing an arc tube both
completely offset from and tilted with respect to the
longitudinal axis of the arc lamp.
Figure 6 is a partial sectional, partial cutaway side
elevational view of the tilted arc discharge lamp, according to
the invention, mounted in a conventional reflector assembly.
Figure 7 is a perspective view of an embodiment of the
invention additionally showing flexible mounting structure for
the are tube.
Detailed Descri tion of the Preferred Embodiment
With reference to the drawings, the preferred embodiment of
the invention will be described. In the drawings, parts or
elements will be referred to by reference numerals.
With particular reference to figure 1, an arc lamp 38 is
depicted. Arc lamp 38 has a conventional threaded mount 40, a
conventional glass envelope or bulb 42, and a tilted arc tube 44
enclosed within bulb 42. As can be seen, arc tube 44 is tilted
with respect to longitudinal axis 46 of arc lamp 38.
Figure 1 also depicts the electrical connections 47, 48
which support tilted arc tube 44 within bulb 42. Electrical
connection 47 has an angled portion 50 connected to one end of
arc tube 44, and electrical connection 48 has an angled portion
52 connected to the other end of arc tube 44. Line 54 depicts
the longitudinal axis of arc tube 44. Axis 54 is thus angularly
pivoted and tilted from, yet generally intersects, axis 46.
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In the preferred embodiment, arc lamp 38 is a metal halide
gas discharge lamp or HID lamp. Such lamps are available from a
wide variety of manufacturers including Philips Lighting, General
Electric, Sylvania, Venture Lighting International, etc. U.S.
Patent 4,341,975, previously mentioned, shows the specifics of
one way of mounting an arc tube within an arc lamp, including the
electrical connections. Such electrical connections are well
:chown in the art and will not be described in detail, other than
they can be made of sufficient materials to both supply electric
potential to opposite sides of the arc tube of quite high power
levels, and at the same time support the arc tube.
In the preferred embodiment of the invention, electrical
connection 47 provides the support of the arc tube 44 with the
assistance of an attached front spring-loaded clip 49 which seats
within the nose 51 of bulb 42. Another spring-loaded clip (not
shown) could be attached to electrical connection 48 to assist in
supporting that end of arc tube 44.
Figure 2 shows an arc lamp 55 with an arc tube 56 having a
longitudinal axis 58 offset in the sense it is tilted from arc
lamp axis 60. It can be seen that arc tube 56 is tilted at a
smaller angle than that which is shown in figure 1, and in an
opposite direction. By further example, figure 3 shows arc lamp
62 having arc tube 64 with longitudinal axis 66 tilted from axis
68 of lamp 62. In this embodiment, the tilt of arc tube 64 is
greater than that shown in figures 1 or 2.
Tt is to be understood that in the broadest sense, the arc
tubes can be offset from the longitudinal axis of the arc lamp in
any direction and orientation. In some applications it may be
desired that the arc tube be tilted upwardly or downwardly with
respect to the longitudinal axis and the front of the bulb to
obtain some sort of a directional orientation of the arc tube for
a specific lighting effect. Additionally, the arc tube does not
have to be centrally or otherwise pivoted on the longitudinal
axis of the arc lamp, but can be offset and/or tilted in other
orientations to the lamp's axis.
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For example, figure 4 shows an arc lamp 100 having a
longitudinal axis 108. Arc tube 102, having a longitudinal axis
109, is offset from lamp longitudinal axis 108 in such a manner
by connections 104 and 106 that arc tube axis 109 is generally
parallel to lamp axis 108. This differs from the embodiments of
1-3 in that arc tube 102 is not tilted with respect to axis 108,
but is offset. This offset would produce beam pattern from lamp
100 which differs from conventional lamp where the arc tube would
be aligned directly along axis 108.
As a further example, figure 5 shows an arc lamp 110 having
a longitudinal axis 118 where arc tube 112 is positioned by
mounts 114 and 116 so that it is both completely offset from
longitudinal axis 118, as well as tilted with respect to
longitudinal axis 118, as highlighted by line 120 which depicts
the longitudinal axis of arc tube 112. The arc lamp can be
mounted in any number of configurations where the arc tube is
offset from the longitudinal axis of the arc lamp. The
longitudinal axis of the arc tube may or may not intersect the
longitudinal axis of the arc lamp, and may or may not be tilted
with respect to the lamp's longitudinal axis. The embodiments of
figures 1-5 therefore give but a few examples of how the arc tube
can be offset from the longitudinal axis of the arc lamp.
If reduction of the tilt factor in mercury or metal halide
lamps is a primary goal, the arc tube can be pivoted and tilted
from the longitudinal axis of the arc lamp (if the arc lamp is
being operated in anything but a horizontal or vertical position)
so that the arc tube ends up in at least a generally horizontal
or vertical position even though the lamp itself is not
horizontal or vertical in orientation.
Figure 6 utilizes arc lamp 38 of figure 1, threadably
mounted into conventional socket 14 of conventional bulb cone 16.
Conventional symmetrical reflector 18 is also utilized. As can
be seen, longitudinal axis 54 of arc tube 44 is generally
horizontal. However, line 70, which represents both the
longitudinal axis of arc lamp 38, and the aiming direction or
reflector axis of the entire fixture, is angularly offset from
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axis 54 downwardly to a target area. It is to be understood that
line 70 and axis 54 are generally in the same vertical plane. It
can therefore be seen that the embodiment of figure 4 holds arc
tube 44 in a generally horizontal position to minimize tilt
factor, and yet utilizes a conventional mounting fixture and
reflector to direct light to the target area.
As can be easily understood, if it were desired to have arc
tube 44 of arc lamp 38 in figure 6 to be vertical to reduce tilt
factor, arc tube 44 could be prepared in that manner. It is to
be further understood that with arc lamps, such as shown, having
threaded mounts, the arc lamps can be rotated into socket 14
until the correct angular orientation of arc tube 44 is achieved.
Alternatively, means can be associated with socket 14, or
threaded mount 40 of lamp 38, to ensure that the correct desired
orientation of arc lamp 44 can be maintained during operation of
the lamp. It is to be also understood that if arc tube 44 is
angled with respect to the longitudinal axis of the lighting
fixture, rotation of the arc lamp within socket 14 allows fine
tuning of the position of arc tube 44 so that almost perfectly
horizontal or vertical positioning can be achieved. -
It is to be appreciated that bulbs 55 and 62 (or other bulbs
with arcs at desired offsets or tilts) could also be utilized in
fixture 10, depending on the desired composite light output from
the fixture. The configuration of the arc lamps of the present
invention allows easy retrofitting to existing fixtures. All
that would be required would be to replace conventional arc lamps
with the tilted arc discharge lamps.
Referring again to figure 6, it is to be understood that
because most of the light radiates laterally from the
longitudinal axis 54 of arc tube 44, a substantial amount of
light would pass directly through reflector lens 20 down to the
target area. A substantial amount of light would also be
captured and reflect off the top hemisphere 72 of the interior of
reflector 18 down to the target area.
A lesser amount of light would radiate directly from either
end of arc tube 44. A lesser amount of light would then be
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reflected from lower hemisphere 78 of the interior of reflector
18.
It can therefore be appreciated that the invention of figure
6 contributes to the advantages of increased light output to the
target area, increased efficiency, reduction in any tilt factor,
and can assist in glare control, all according to selection of
the degree of tilt of the arc tube, and its position within a
fixture.
The present invention therefore allows significant
flexibility in creating different light output patterns, and
enables ways to make the arc lamp more efficient with higher
efficacy. The invention can also contribute, in certain
circumstances to longer lamp life and better lumen maintenance
because of reducing hot spots and colder areas in the arc tube.
Figure 7 depicts a lamp 160 according to the present
invention having an arc tube 162 which is tilted from the
longitudinal axis of lamp 160. Figure 7 shows the structure for
mounting arc tube 162 in a tilted position, and yet allows it to
be inserted through the narrow neck opening 168 of bulb 170. In
this embodiment, electrical power would be connected to~arc tube
162 by conventional means (not shown) such as is known in the
art. Support for the tilted arc tube 162 would be accomplished
by first and second support rods 164 and 166 which extend from
threaded screw mount or base 172 through opening 168, parallelly
along apposite sides of arc tube 162 out to spring clip 182,
Which securely seats within nose 184 of bulb 170. Another spring
clip 183, attached to rod 166, could be positioned in the neck of
bulb 170 to assist in supporting the structure. The clips are
configured and mounted so as not to short out any electrical
connections to arc tube 162.
Rods 164 and 166 are bent so that when clip 182 is
positioned in nose 184, clip 183 is positioned in the neck of
bulb 170, and the opposite ends of rods 164 and 166 are secured
in base 172, arc tube 162 is held in the desired angular
position. As can easily be understood, the tilt or offset of arc
tube 162 can vary according to desire. In the preferred
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embodiment, the tilt from longitudinal axis of the bulb can be
between 20' and 45~.
To facilitate the insertion of arc tube 162 into arc lamp
160 during assembly, support rods 164 and 166 can have narrow
portions or flat springs 174, 176 and 178, 180 along their
lengths on opposite sides of arc lamp 162. These narrowed
portions assist the sections of support rods 164 and 166 to be
resiliently flexed to allow insertion of the entire assembly into
bulb 170. Once inserted and properly seated, the narrowed
sections are resilient and rigid enough to hold the arc tube 162
in its desired position.
Flat springs 174 and 176 have therefore been incorporated
into support rods 174 and 176 on one side of arc tube 162. Flat
springs 178 and 180 have likewise been so incorporated on the
other side of arc tube 162 directly adjacent the c-shaped spring
or clip 182 which allows mounting of the arc tube 162 in the
front of bulb 170.
The flat springs 174, 176, 178, and 180 allow flexing of
rods 164 and 166 so as to flatten out rods 164 and 166. This, in
turn, allows arc tube 162 and supporting structure to be inserted
through opening 168. Upon complete entry into bulb 170, the flat
springs return the arc tube 162 to its tilted attitude.
This arrangement allows insertion and assembly of those
types of arc lamps, utilizing bulbs with openings of fixed
diameters, such as are used in the art. This is particularly
useful if the amount of arc tilt is such that conventional
insertion methods will absolutely not work.
The arrangement of Figure 7 has further advantages. First,
the arrangement of rods 164 and 166 rigidly and adequately
supports arc tube 162 so that its precise location during use is
ensured. Secondly, springs 174, 176, 178 and 180 provide
sufficient rigidity, yet also have flexibility and shock
absorption to inhibit breakage or damage during shipment or use.
Third, this arrangement allows arc tube 162 to be tilted at
significant angles from the center longitudinal axis of lamp 160
which contributes to increased yield of light, as previously
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explained, diminution of tilt factor, as previously explained;
while still enabling flexible insertion into the bulb 170 during
manufacturing and assembly.
The embodiment of figure 7 therefore shows a method and
structure to allow significant tilting of arc tube 162 while at
the same time allowing flexion of the support rods 164 and 166
efficiently to allow insertion into bulb 170.
It will be appreciated that the present invention can take
many forms and embodiments. The true essence and spirit of this
invention are defined in the appended claims, and it is not
intended that the embodiment of the invention presented herein
should limit the scope thereof.
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