US2200939A - Gaseous electric discharge lamp device - Google Patents

Description

Patented May 14, 1940 PATENT OFFICE 2,200,939 .GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Georg Trebbln, Berlin-Spandau, Willy Ledig, Berlin-Lichtenrade, and Hans-Joachim Helwlg,

Berlln-Schoneberg,

Germany,

assignors to General Electric Company, a corporation of New York Application August 12, 1938, Serial No. 224,614

' In Germany August 14, 1937 Claims. (01.176-126) The present invention relates to gaseous elec tric discharge lamp devices generally and more particularly the invention relates to such devices of the high pressure type having solid electrodes at least one of which is an auxiliary electrode which facilitates the starting of the device.

The object of the invention is to improve and simplify the structure and the manufacture of discharge devices of the above type. Another object of the invention is to provide an electrically conducting, hermetic seal structure useful in gaseous electric discharge devices of the above type. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

The invention attains its object by making the auxiliary electrode and the current lead for said electrode in the form of a continuous, electrically conducting metal coating on the surface of a vitreous rod or tube and by fusing the rod or tube into a tubular end part of the vitreous container of the discharge device in such manner that the inner end of the coated rod or tube extends into the container to serve as an auxiliary electrode. The part of the metal coating which is in the tubular extension of the container constitutes the current lead for the auxiliary electrode. Thus in the manufacture of the discharge lamp device it is only necessary in order to seal an auxiliary electrode therein to first mount the coated rod or tube in the opening of the tubular extension of the container in such manner that the inner end of the rod or tube extends into the space defined by the container of the discharge lamp device and then to fuse all the elements together at their adjoining surfaces. The comparatively large area of the auxiliary electrode facilitates the formation of a glow discharge for starting the main arc discharge between the main discharge supporting electrodes of the gaseous electric discharge lamp device.

In the drawing accompanying and forming part of this specification three embodiments of the invention are shown, in which Fig. 1 is a front elevational, partly sectional view of a gaseous electric discharge lamp device embodying the invention,

Fig. 2 is a front elevational, partly sectional view of one end of a gaseous electric discharge lamp device similar to that shown in Fig. 1,

Fig. 3 is a sectional view along the line 3-3 of Fig. 2, and

Fig. 4 is a front elevational, partly sectional view of another discharge lamp device embodying the invention.

Like numbers denote like parts in all the figures. Referring to Fig. 1 the gaseous electric discharge lamp device comprises an elongated, tubular containe I consisting of a difficulty fusible, vitreous material, such as quartz. Said container I has at each end thereof a tubular extension 2. A quartz rod 4, having a metal coating 3 thereon over the entire length thereof, is fused into the lower tubular extension 2 of the container I and extends beyond the external end of the extension 2. A hollow, main discharge supporting electrode 5 consisting of a wire wound helically is mounted in the lower end of the container I. Several turns 5 of said wire are interposed between the metal coating 3 and the tubular extension 2 so that the electrode 5 is securely fastened in the container I and is electrically connected to the metal coating 3 on the quartz rod 4. The coated end of the quartz rod 4 which protrudes from the end of the tubular extension 2 has a wire helix wrapped therearound. Several turns of the wire helix 6 are interposed between the metal coating 3 and the tubular extension 2 to fasten said helix 6 securely and to make a good electric contact with said coating 3. A contact I in the form of a metal band surrounds the end of the rod 4 projecting beyond the extension 2 and said contact I is clamped on the helix 6. The coating 3 thus serves as a current lead for the lower main electrode 5. Said electrodes 5 are coated or impregnated with a material having a high electron emissivity, such as barium oxide, strontium oxide or mixtures of said oxides.

The upper tubular extension 2 of the container I surrounds a quartz tube 9 which in turn surso I rounds a quartz rod 8, all of these members being concentric. The quartz rod 8 and the tube 9 have a metal coating III and II, respectively, thereon and all these members are fused together. The inner end of the quartz tube 9 terminates adjacent the inner end of the extension 2 and the inner end portion of the quartz rod 8 extends beyond the respective end of the tube 9 an appreciable distance into the space enclosed by the container I. The portion ID of the metal coating III covering the inner end portion of the rod 8 serves as an auxiliary starting electrode and the other part of the coating I0 constitutes the current lead for the auxiliary electrode. The main discharge supporting electrode 5, which has the same structure as the electrode 5 mounted in the opposite end of the container I, is mounted in such position in said container I that it surrounds Several turns 5' of the upper electrode 5 are interposed between the coating I I and the exten sion 2 for the same purposes as the turns 5', on the opposite end of the tube.. The part of the tube 9 which extends beyond the outer end of the extension 2 and the part of the rod 3 which extends beyond the outer end of the tube 9 have wire helices I2 and I3, respectively, wrapped therearound. The inner turns of the helix l2 are fused between the extension 2 and the metal coating II on' tube 3 and the inner turns of the helix I3 are fused betweenthe tube 3 and the metal coating I 0 on'the quartz rod 8. Both these helices I2 and I3 like the helix 6 on the opposite end of the tube serve to facilitate the clampingof two current connections I4 and I5 thereto, respectively. The metal coating II on the tube 9 serves as the current lead for the main discharge supporting electrode 5. The container I has an exhaust tip I6 thereon which is formed when the exhaust tubeis sealed.

The container I has therein a starting gas, such as argon, or neon at a pressure of about 1 to 20 mm. and a quantity of mercury the vaporof which is at an elevated pressure, such as a pressure of 5 atmospheres and higher, during the operation of the device. The device starts as a gas discharge lamp and. operates as a vapor discharge lamp and is an efficient source of visible and ultra-violet light. When desired, the quantity of mercury is limited to an amount such that it is wholly vaporized during the operation of the device. When desired, the quartz rod 8 is replaced by a quartz tube and said tube serves not only to support the auxiliary electrode l0 and the current lead I 0 therefor but also as an exhaust tube which, after the steps of evacuation and filling with a desired gas are completed, is sealed.

The gaseous electric discharge lamp device one end of which is illustrated in Figs. 2 and 3 of the drawing is similar in all respects to the lamp device illustrated in Fig. 1 except that in this embodiment the current lead for the main electrode 5 consists of a thin metal strip ll, such as a molybdenum strip, which is fused into the quartz body 4. soldered to said strip H at the inner end thereof and a current lead I8 is fastened to the opposite end of the said strip II. The outer surface of the quartz body 4 has a metal coating 3 thereon and projects an appreciable distance into the space defined by the container I. The part 3' of the metal coating 3 starting electrode and the other part of said coating 3 serves as a current lead for said electrode. The coated quartz body 4 is fused into.

the tubular elongation 2 of the container I and a current lead 6 is interposed between and fused into the elongation 2 and the metal coating 3 on the quartz body 4.

In the manufacture of the lamp the strip I1 is first mounted in the tubular quartz body 4 and the quartz body 4 is then heated and pinched down on the strip II. The main electrode 5 is then fastened to one end of the strip I1 and then the coating 3 is applied to the surface of the quartz body 4. The element thus made is inserted in the extension 2 together with the coil current lead 6 and then all these elements are fused together to make an electrically conducting, mechanically strong, hermetically tight seal capable of withstanding elevated tempera tures.

The electrode 5 is welded or serves as an auxiliary.

2,200,939 'and extends beyond the end I0 of the coating In;

When desired, the other end of the lamp is o! a similar structure with the omission of the metal coating 3 and the current lead 8, or when desired, a structure similar to that illustrated in the lower end of Fig. 1 of the drawing, is used v as a current lead for the lower main discharge supporting electrode 5 and the part 3' of the coating constituting the auxiliary electrode extends a substantial distance along the discharge path between the main electrodes 5. In this embodiment the two quartz bodies 4, electrodes 5, current leads 6 and the coating 3 are made into a unitary structure before being mounted in the container I.

In the manufacture of the lamp the two quartz rods 4 are first joined by a smaller quartz rod I9. The metal coatings 3 together with the strip extension 3 are then applied to the rods 4 and the rod l9, respectively. The electrodes 5 and the current leads 6 are then mounted on the element thus produced and this element is inserted in the proper position in the quartz container I having the tubular extensions 2. The tubular extensions 2 of the container I are then fused to the quartz rods 4 and after the lamp has been evacuated and filled with the desired gaseous atmosphere it is sealed off at I6.

'I'he'lower coating 3 serves asa current lead for both the lower main electrode 5 and the auxiliary electrode 3. Since the auxiliary electrode 3' has a very small cross-section it has a correspondingly high resistance so that it serves as its own series resistance for the auxiliary starting discharge which takes place between the upper main electrode 5 and the end of the strip 3'. When the resistance of the strip 3' is not suflicient it is oxidized with the exception of the end portion thereof. I

In all the embodiments of the invention described above the metal coatings are very thin, continuous films and consist of a difllcultly fusible metal, such as tungsten, molybdenum, platinum or rhodium and the coatings are applied to the supporting bodies therefor .by methods now known in the art, such as by burning in a paste or a powder, or by coating said bodies with a colloidal solution of the metal oxide and heating in a reducing atmosphere. When desired, the supporting bodies for the metal coatings consist of hard glass having an extremely low coefllcient of expansion, almost that of quartz, and when desired, the container I consists of a hard glass of this kind.

While our invention is particularly useful in conjunction with gaseous electric discharge devices of the high pressure, positive column, are discharge type it will be understood, of course, that we contemplate that the invention may be used in other types of discharge devices, such as cathode glow discharge devices. In such devices the part of the metal coating inside the space defined by the container is used as one of the main electrodes for the cathode glow discharge and the part of the current lead outside of said space is used as the series resistance and the current lead connecting said main electrode to the base of the lamp. The coating is applied either to the inner surface of the container and a tubular extension on said container to which the base is fastened or to a cylindrical member fused into said container and said extension. When the coating is applied to such a cylindrical member another electrode is mounted on said member, as in Fig. 2 of the drawing, or the coating is in two parts separated a slight distance on said member to form two main electrodes and two current leads.

While we have shown .and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and scope of the invention, for example, the metal coating electrodes comprise a material having high electron emissivity, when desired, and, when desired, the lamp devices illustrated in the drawing are mounted in a sealed envelope which is either evacuated or filled with an inert gas to conserve the heat generated by the discharge in the device.

What we claim as new and desire to secure by Letters Patent of the United States, is:-

1. A gaseous electric discharge device comprising a vitreous container, solid electrodes sealed therein, a gaseous atmosphere therein, said container having a tubular extension thereon, a vitreous seal member in said tubular extension, said seal member projecting into the space defined by said container and a layer of metal interposed between said extension and said seal member and covering the end portion of said seal member projecting into said container, said extension, said seal member and said metal layer being fused together to form an hermetic joint, the part of said layer in the space defined by said container being an auxiliary electrode to facilitate the starting of the main arc discharge in said device, the part of said layer interposed between said extension and said seal member being a current lead for said auxiliary electrode.

2. A gaseous electric discharge device comprising a vitreous container, solid electrodes sealed therein, a gaseous atmosphere therein, said container having a tubular extension thereon, a vitreous seal member in said tubular extension. said seal member projecting beyond the external end of said extension, a layer of metal interposed between said extension and said seal member and covering the exposed end of said seal member and a metal wire helix wrapped around the exposed part of said metal layer and extending into said extension a distance less than the distance said coating extends therein, said extension, said helix, said metal layer and said seal member being fused together to form an hermetic joint, said helix and said coating being a current lead for one of said electrodes.

- 3. A gaseous electric discharge device comprising a vitreous container, solid electrodes sealed therein, a gaseous atmosphere therein, said container having a tubular extension thereon, a vit reous tube in said extension, a vitreous body having a cylindrical surface in said vitreous tube, said vitreous tube extending beyond the external end of said extension. one end portion of said vitreous body extending beyond the external end of said vitreous tube and the opposite end portion of said vitreous body extending into the space defined by said container, a metal coating on the outer surface of said tube and extending the full length thereof, another metal coating on the cylindrical surface of said vitreous body and extending the full length thereof, a hollow, cylindrical, main discharge supporting electrode mounted in said container concentric with the end portion of said vitreous body extending into said container and having a larger diameter than said end portion, support wires for said main electrode interposed between said container extension and the metal coating on said vitreous tube, a wire helix wrapped around the external part of the metal coating on saidvitreous tube and extending a short distance into said extension, another wire helix wrapped around the cxternal part of the coating on said vitreous body and extending a short distance into said vitreous tube, said extension and the elements surrounded thereby being fused together to form an hermetic joint, the part of the metal coating on the end portion of said vitreous body in said container being an auxiliary electrode to facilitate the starting of the main discharge in said device, the other part of said coating being a current lead for said auxiliaryelectrode, the metal coating on said vitreous tube being a current lead for said main electrode.

4. A gaseous electric discharge device comprising a vitreous container, solid electrodes sealed therein, a gaseous atmosphere therein, said container having a tubular extension thereon, a vitreous seal member in said tubular extension and a metal coating on said seal member, said seal member and the metal coating thereon extending into the space defined by said container, a current lead surrounded by said seal member and a main discharge supporting electrode connected to said current lead, said current lead, said seal member, said metal coating and said extension being fused together to form an hermetic joint, the part of said metal coating in said container being an auxiliary electrode to facilitate the starting of the main discharge in said device, the other part of said coating being a, current lead for said auxiliary electrode.

5. A gaseous electric discharge device comprising an elongated, tubular, vitreous container, solid electrodes sealed therein, a gaseous atmosphere therein, said container having an extension at each end thereof, a vitreous seal member in each of said extensions, a metal layer interposed between each of said seal members and said extensions, a vitreous rod joining said seal members and supports for said electrodes interposed between said layer and said extensions, one of said layers extending along said rod and terminating adjacent the electrode at the opposite end of said container, said extensions, said supports, said layers and said seal members being fused together t form an hermetic joint, the part of the metal layer on said rod being an auxiliary electrode to facilitate the starting of the main discharge in said device, the other part of said layer being a current lead for said auxiliary electrode and one of said main electrodes, the other of said layers being a current lead for the other of said main electrodes.

GEORG TREBBI'N. WILLY LEDIG. HANS-JOACHIM HELWIG.

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