GB2154055A - Getter mounting arrangements - Google Patents

Abstract

A getter device for use with incandescent and high intensity discharge lamps comprising nickel tubing sufficiently porous to allow gases to pass therethrough has getter material situated therein. The nickel tubing can be used in place of support leads in high intensity discharge lamps or in place of lead-in wires in incandescent lamps. Alternatively the porous nickel tubing containing the getter material can be coiled around the support rods of the high intensity arc tube or the lead-in wires of an incandescent lamp adjacent the lamp filament. <IMAGE>

Description

SPECIFICATION Getter mounting arrangements Background of the Invention This invention relates to bulk getter mounting arrangements for high intensity discharge (HID) lamps and incandescent lamps.

In lamp assembles 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 and hereby incorporated by reference, a bulk getter is used in the region 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,u (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 50y or 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 envelope which contains a high efficiency arc discharge tube and filamentary resistance elements, is an alloy of 88% zirconium and 14% aluminum sold by SAES Getters, Colorado Springs, Colorado under the designation ST101. The powdered getter material is attached to a nickel-coated iron ribbon and cut into smail 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 400"C. The getter tab cannot be mounted in a position where the operating temperature is optimum without reducing light output. The getter presently used is adequate for base-down operating lamps. Future universal operating position lamps will probably operate at a lower temperature, reducing the efficacy of the presentlyused 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 slurry 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 aluminum attached to the filament support leads. Painting getter material directly on the filament support leads is satisfactory for lamps which do not require large amounts of gettering. Increasing the quantity of getter powder attached to the filament support leads is difficult because thicker coatings tend to crack and fall off.

The quantity of getter powder 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 off, resulting in a high hydrocarbon atmosphere which reduces filament life. The zirconium plus aluminium powder requires a temperature near or above 5002C for significant gettering of hydrogen.

In one embodiment of the present invention an evacuable envelope containing a light-emitting element is provided. Nickel 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 current to the discharge tube.

Nickel tubing, sufficiently porous to allow gases to pass therethrough, and with getter material situated therein, is wrapped around at least one of 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.

The getter mount and getter materials are inexpensive and will exhibit satisfactory gettering at temperatures below 400"C. Moreover, the getter can be mounted in a position where the operating temperature is optimum without reducing the lamp light output.

In the accompanying drawings, by way of example only: Figure 1 is a partially cut away side view of a multi-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 multi-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.

Referring now to the drawings wherein like numerals indicate like elements throughout, there is shown in Figure 1, a high intensity discharge lamp assembly comprising a glass enclosure, which contains a high efficiency arc 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 metal 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 and hereby incorporated by reference.

The arc discharge tube 5 is suspended between a long support rod 11 and short support rod 1 3 which are both electrically connected by spot welding, for example, to lead-in wires 1 5 of the arc discharge tube.

The arc discharge tube is surrounded by a glass shield 14. The support rods 11 and 1 3 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 40 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 arrang ing the fibers to form a fiber mat. Nickel fiber mats are available from National-Standard of Niles, Michigan under the trademark "Fibrex- SCUM". 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 85% zirconium, 10% titanium, and 5% nickel or 85% zirconium, 7% iron and 8% aluminum. The percent of titanium, nickel, iron and aluminum may be adjusted by increasing or decreasing the amounts of any of the constituents. individually or in combination, by between 1 and 14%. The filled tubing can then be sintered in a vacuum at about 7505C. 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 discharge lamp 5 and serving as supplemental light sources. A power supply unit includes a rigid case 1 9 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 United States patent no. 4,350,930 assigned to the instant assignee and hereby incorporated by reference.

The bulk getter powder is preferably heated to 250 C-450 > C 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 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 11 a and 1 3a are not porous nickel tubes but support rods of the type conventionally used.

Porous nickel tubing 1 6 filled with getter powder, as described in connection with Figure 1, is coiled around support rod 11 a near the end of the arc discharge tube where it is heated to 250"-450"C 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 resistance 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 nickel tubing 1 6 filled with getter material is coiled around the support leads adjacent the filament where they are heated to 250-450"C during lamp operation by conduction, convection and radiation from the filament to provide gettering.

The foregoing describes a getter device which allows operation below 400"C and which can be mounted in a position where the operating temperature is optimum without reducing the lamp output.

While the invention has been particuiarly shown and described with reference to several preferred embodiments 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.

Claims (14)

1. A lamp comprising: an evacuable envelope; nickel tubing sufficiently porous to allow gases to pass therethrough; getter material situated inside said tubing; a light emitting element situated in said evacuable envelope; lead-in wires electrically coupled to said light-emitting element, said nickel tubing electrically coupled to at least one of said lead-in wires for providing support and capable of providing electrical current to the light emitting element as well as providing a getter mounting arrangement.

2. The lamp of claim 1 wherein said getter material comprises an alloy of 85% zirconium, 10% titanium and 5% nickel.

3. The lamp of claim 1 wherein said getter material comprises an alloy of 85% zirconium, 7% iron and 8% aluminum.

4. The lamp of claim 1 wherein said lamp is a high intensity discharge lamp and said light emitting element is an arc discharge tube.

5. The lamp of claim 4 wherein said getter material comprises an alloy of 85% zirconium, 10% titanium and 5% nickel.

6. The lamp of claim 4 wherein said getter material comprises an alloy of 85% zirconium, 7% iron and 8% aluminum.

7. The lamp of claim 1 wherein said lamp is an incandescent lamp and said light emitting element comprises a filament.

8. The lamp of claim 7 wherein said getter material comprises an alloy of 85% zirconium, 10% titanium and 5% nickel.

9. The lamp of claim 7 wherein said getter material comprises an alloy of 85% zirconium, 7% iron and 8% aluminum.

10. A high intensity discharge lamp comprising: an evacuable envelope; support rods; nickel tubing sufficiently porous to allow gases to pass therethrough; getter material situated inside said tubing; an arc discharge tube situated in said evacuable envelope; and lead-in wires electrically coupled to said arc discharge tube, said support rods affixed to said lead-in wires and extending outside the evacuable envelope said nickel tubing wrapped around at least one of said support rods adjacent to said arc discharge tube.

11. The high intensity discharge lamp of claim 10 wherein said getter material comprises an alloy of 85% zirconium, 10% titanium and 5% nickel.

1 2. The high intensity discharge lamp of claim 10 wherein said getter material comprises an alloy of 85% zirconium, 7% iron and 8% aluminum.

1 3. A incandescent lamp comprising: an evacuable envelope; nickel tubing sufficiently porous to allow gases to pass therethrough; getter material situated inside said tubing; a filament; and support wires electrically coupled to said filament for providing support and capable of providing electrical current to said filament, said nickel tubing wrapped around at least one of said support wires adjacent said filament.

14. The lamp of claim 1 2 wherein said getter material comprises an alloy of 85% zirconium, 10% titanium and 5% nickel.

1 5. The lamp of claim 1 3 wherein said getter material comprises an alloy of 85% zirconium, 7% iron and 8% aluminum.

1 6. A lamp substantially as herein described with reference to any one of Figs. 1 to 4 of the accompanying drawings.