Note: Descriptions are shown in the official language in which they were submitted.
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POROUS NICKEL TUBING ~VING GETTER MATERIAL
THE~EIN FO~ INCANDESCENT AND DISCHARGE LAMPS
Backqround of the Invention
This invention relates to bulk getter mounting
arrangements for high intensity discharge (HID) lamps
and incandescent lamps.
In lamp assemblies having a glass envelope which
contains a high efficiency arc discharge tube and
filamentary resistance elements, such as the lamp
shown and described in U.S. Patent 3,248,590 assigned
to the instant assignee, a bulk getter is used in the
reyion between the arc tube and the outer envelope.
This getter is needed in order to reduce the hydrogen
pressure to a level near or below 1~ (10-3 Torr).
This low hydrogen partial pressure is necessary to
prevent early burn out of the tungsten filamentary
resistance elements, and to reduce hard starting of
the arc discharge tube.
Lamp assemblies having a high efficiency arc
discharge tube and filamentary resistance elements
require more gettering than most incandescent or
discharge lamps due to a glass shield around the arc
discharge tube that operates at a very high
temperature and thus evolves water continuously and
the inner wall of the outer glass envelope cannot be
completely degassed during the short bake cycles
occurring during manufacture.
During lamp operation the tungsten filament is
heated to a high temperature in order to provide light
instantly when the lamp is first turned on. Later
when the lamp warms up, the tungsten filament current
decreases but the filament remains hot enough to react
with any residual hydrogen or water present which
could result in early burnout. Also, hydrogen
diffuses readily through the hot quartz of the arc
lamp. If the hydrogen partial pressure is near 50~ or
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above, the arc lamp starting voltage increases and the lamp
becomes hard to start. If this increased starting voltage
exceeds the ballast voltage capability, the lamp will fail.
Presently-used getter material in lamps having a glass
S envelope which contains a high efficiency arc discharge tube
and filamentary resistance elements, is an alloy of 86%
zirconium and 14% aluminum sold by SAES Getters, Colorado
Springs, Colorado under the designation STlO1. The powdered
getter material is attached to a nic~el-coated iron ribbon
and cut into small tabs about 0.5 cm2 in area. A getter tab
is spot welded to an upper arc tube support on each lamp and
is heated during normal lamp operation, by conduction and
convection, to about 400C. The getter tab cannot be
mounted in a position where the operating temperature is
lS optimum without reducing light output. The getter presently
used is adequate for base-down operating lamps. Euture
universal operating position lamps will probably operate at
a lower temperature, reducing the efficacy of the presently-
used getter material.
Present incandescent lamps include a getter of powdered
zirconium and aluminum which is painted directly on the
filament support leads in slurry form. The slurrv comprises
the powdered getter and a hydrocarbon binder such as
nitrocellulose in a suitable solvent. The getter cleans up
or adsorbs hydrogen from the lamp which is generated by the
dissociation of water vapor by the heated filament. If the
water vapor level is not controlled, tungsten from the
filament is deposited on the glass envelope more rapidly
than occurs when water vapor is not present and a shortened
filament life results.
During the processing of the lamp, much of the
nitrocellulose and solvent are decomposed and pumped away,
leaving the powdered zirconium and alum~num attached to the
filament support leads. Painting getter material directly
on the filament support leads is satisfactory for lamps
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which do not require large amounts of gettering. Increasing
the quantity of getter powder attached to the filament
support leads is difficult because thic~er coatings tend to
crack and fall off.
The quantity of getter powder put on the leads is
difficult to control and reproducibility from lamp to lamp
is not good. Some of the binder remains in the getter and
is evolved after lamp seal of~, resulting in a high
hydrocarbon atmosphere which reduces filament life. The
zirconium plus aluminum powder requires a temperature near
or above 500C for significant gettering of hydrogen.
It is an object of the present invention to provide a
getter mount and getter materials which will exhibit satis-
factory gettering at temperature below 400C and have low
cost.
It is a further object of -the present invention to
provide a getter mount arrangement which can be mounted in a
position where the operating temperature is optimum without
reducing the lamp light output.
SummarY of the Invention
In one embodiment of the present invention an evacuable
envelope containing a light-emitting element is provided.
Nic~el tubing sufficiently porous to allow gases to pass
therethrough, and with getter material situated therein, is
electrically and mechanically coupled to lead-in wires of
the light-emitting element to provide support and
electrical current to the light-emitting element as well as
a getter mounting arrangement. In both the aforementioned
embodiments, the light-emitting element may comprise an arc
discharge tube or a filament.
In another embodiment of the present invention, a lamp
comprising an arc discharge tube having lead-in wires
situated in an evacuable envelope is provided. Support rods
affixed to the lead-in wires provide support and electrical
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current to the arc discharge tube. Nickel tubing, suffi-
ciently porous to allow gases to pass therethrough, and with
getter macerial situated therein, is wrapped around at least
one o~ the support rods adjacent to the arc tube.
In yet another embodiment of the present invention an
incandescent lamp comprising a filament supported by lead-in
wires within an evacuable envelope is provided. Nickel
tubing, sufficiently porous to allow gases to pass
therethrough, and with getter material situated therein, is
wrapped around at least one of the lead-in wires adjacent
the filament.
Description of the Drawing
While the specification concludes with claims particu-
larly pointing out and distinctly claiming the present
invention, the objects and advantages of the invention can
be more readily ascertained from the following description
of preferred embodiments when used in conjunction with the
accompanying drawing in which:
Figure 1 is a partially cut away side view of a mul-
ti-vapor lamp including filamentary resistance elements and
a bulk getter in accordance with the present invention;
Figure 2 is a partially cut away side view of a mul-
ti-vapor lamp including filamentary resistance elements and
a bulk getter in accordance with another embodiment of the
present invention;
Figure 3 is a side view of an incandescent lamp with a
bulk getter in accordance with the present invention; and
Figure 4 is a side view of an incandescent lamp with a
bulk getter in accordance with another embodiment of the
present invention.
Detailed Description of the Invention
~ eferring now to the drawing wherein like numerals
indicate liXe elements throughout, there is shown in Figure
1, a high intensity discharge lamp assembly comprising a
glass enclosure, which contains a high efficiency arc
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discharge lamp 5 and filamentary resistance elements 7 and
9. A suitable light source for use as the arc discharge
tube is a high pressure discharge lamp that operates by
vaporizing mercury and selected me-tal halides. A high
pressure discharge tube of this type is more fully described
in United States patent 4,161,672 assigned to the instant
assignee. - ~
The arc discharge tube 5 is suspended between a long
support rod 11 and short support rod 13 which are both elec-
trically connected by spot welding, for example, to lead-in
wires 15 of the arc discharge tube. The arc discharge tube
is surrounded by a glass shield la. The support rods 11 and
13 comprise nickel tubing sufficiently porous to allow gases
to pass therethrough, and have getter material situated
therein.
The nickel tubing can be formed, for example, by
powdered nickeL which is extruded in tube form having a ~0
mill outside diameter. The porosity of the nickel tubing
can be controlled by varying the pressure, temperature and
particle size in forming the tube. Alternatively, porous
nickel tubing can be extruded from nickel fiber mat material
which is made by extruding nickel oxides and reducing the
oxides to form fibers and arranging the fibers to form a
fiber mat. Nickel fiber mats are available from Nation-
al-Standard of Niles, Michigan under the trademark
"Fibrex-SCM". Raney nickel which comprises approximately
50% nickel and 50% aluminum can be used to make porous
nickel tubing by extruding the Raney nickel to form a tube
and then etching the aluminum away using a concentrated NaOH
solution. The porous nickel tubing has its interior portion
filled with getter powder such as an alloy of ~5% zirconium,
10% titanium, and 5% nickel or ~35% ~irconium, 7% iron and 8%
aluminum. The percent of titanium, nick-l, iron and alumi-
num may be adjusted by increasing or decreasing the amounts
of any of the constituents, individually or in combination,
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by between 1 and 14%. The filled tubing can then be
sintered in a vacuum at about 750C. After sintering,
the getter-filled porous nickel tubing can be handled and
formed much like wire or ribbon.
The resistance elements 7 and 9 are an electrical part
of the power supply, being used to ballast the arc dis-
charge lamp 5 and serving as supplemental light sources.
A power supply unit includes a rigid case 19 attached to
the glass enclosure 3 and a screw-in base 20. The unit
develops the required energization of the arc discharge
lamp during starting and operating conditions and produces
instant illumination by use of the supplemental light source
9. The supplemental illumination is relatively constant
during starting, tapering off as the arc lamp warms up.
The lighting unit is more fully described in the
United States Patent No. 4,350,930, issued September 21,
1982 to Peil et al and assigned to the instant assignee.
The bulk getter powder is preferably heated to
250C-450C for maximum gettering speed. The porous nickel
tube permits easy access of impurity gases, mainly hydrogen,
to the getter powder. Conduction heating from the arc
discharge tube lead-in wires provides most of the heat
during lamp operation. Depending on the orientation of the
lamp (base up, base down, or horizontal) the bulk getter in
2~ one or the other or both of the support rods will be heated
to the proper operating temperature. The bulk getter
getters mainly hydrogen during lamp operation to prevent
early burnout of the tungsten filament, and prevents hard
starting of the arc discharge tube.
Figure 2 shows another embodiment of the present
invention for use with a high intensity discharge tube in
an evacuated envelope. The lamp shown is the same type as
shown in Figure 1, except that the support rods lla and 13a
are not porous nickel tubes but support rods of the type
conventionally used. Porous nickel tubing 16 filled with
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getter powder, as described in connection with Figure 1, ls
coiled around support rod lla near the end of the arc
discharge tube where it is heated to 250-450C during lamp
operation. While the invention has been shown with high
intensity discharge lamps with filamentary resistance
elements between the outer envelope and the arc discharge
tube, the getter of the present invention can be used in
high intensity discharge lamps without filamentary resis-
tance elements.
Referring now to Figure 3 an incandescent lamp assembly
comprising a glass enclosure 21, lead-in wires 23 attached
to a filament 25, and a glass support stem 27 through which
the lead-in wires extend, is shown. The support stem seals
the bottom of the glass enclosure 21. Nonconductive cross
support member 26 maintains the spacing between lead-in
wires 23, and a support member 28 attached to the support
stem 27 restricts motion of the filament 25. A screw-in
base 29 is cemented to the base of the glass enclosure 21
and is electrically connected to the lead-in wires. The
lead-in wires comprise porous nickel tubing filled with
getter powder of the type described in connection with Fig.
1.
Referring now to Fig. 4 an incandescent lamp assembly
of the type shown in Fig. 3 is shown except that the lead-in
wires 23a are conventional lead-in wires. Porous nic~el
tubing 16 filled with getter material is coiled around the
support leads adjacent the filament where they are heated to
250-450C during lamp operation by conduction, convection
and radiation from the filament to provide ge-ttering.
The foregoing describes a getter device which allows
operation below 400C and which can be mounted in a position
where the operating temperature is optimum without reducing
the lamp output.
While the invention has been particularly shown and
described with reference to several preferred embodiments
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thereof, it will be understood by those skilled in the art
that various changes in form and detail may be made without
departing from the spirit and scope of the invention.
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