DE1151877B - Cathode for a high pressure discharge lamp, preferably a noble gas high pressure lamp - Google Patents

Description

INTERNAT. KL. HOIj

GERMAN

PATENT OFFICE

P28309Vmc / 21f

REGISTRATION DATE: NOVEMBER 27, 1961

NOTICE THE REGISTRATION AND ISSUE OF EDITORIAL: JULY 25, 1963

The invention relates to the design of cathodes of high pressure discharge lamps, preferably of noble gas high-pressure lamps with discharge-heated electrodes from a tightly hammered activated tungsten bodies are equipped. This tungsten body is advantageous on a one-off basis Tungsten existing power supply rod in any way, for. B. by pressing, shrinking or weld on. It was known in noble gas high-pressure lamps that glow electrodes were made to produce a sintered tungsten body, which apart from a hole for fastening the Power supply on the end face to be turned towards the discharge, possessed a further recess, in which is a tightly hammered or melted compacted, plug-like tungsten body with over The dome which is outstanding for the sintered body and serves as an arc attachment, preferably by shrinking was attached. This division of the electrode body took place because it was previously special Difficulties made on the one hand to produce hammered tungsten bodies in the required size and on the other hand subsequently, z. B. for attachment to the power supply rod to edit. Under unfavorable circumstances, the sintered bodies can also be used after thorough annealing in a vacuum Release absorbed gases during operation, which then rapidly destroy the electrodes to lead. However, when one was able to manufacture the tungsten electrode bodies from one piece, it was found that a special shape of the cathodes is necessary in order to achieve a sufficient and to achieve rapid heating of the cathode and, on the other hand, an uneven burn-off to avoid the cathode tip.

These difficulties are caused by a high pressure discharge lamp according to the invention Corrected such a shape of the cathode that at a distance of less than half of their Length, calculated from the cathode tip, a temperature of at least 2000 ° C prevails by the conical tip of the cathode with an angle of less than 50 °, preferably 30 to 40 °, is formed and has a rounded tip with a tip radius of more than 0.2 mm. In the case of high-output discharge lamps, for the purpose of faster heating and heating to one higher temperature the cathode tip at least partially through an annular incision about perpendicular to the cathode axis separated from the rest of the cathode body. The Cathode-cathode usually made of tungsten for a high-pressure discharge lamp, preferably noble gas high pressure lamp

Applicant:

Patent -Treuhand- Gesellschaft

for electric light bulbs m. b. H., Munich 2, Windenmacherstr. 6th

Dipl.-Phys. Horst Schlegel, Berlin-Kladow, has been named as the inventor

body an addition of less than 6%, preferably about 3% thorium oxide.

Due to the acute-angled cone shape of the cathode and also due to the ring-shaped partial separation of the cathode tip, the front cathode mass heats up more strongly during discharge operation, whereby the thermal emission is improved. Above all, there is also faster heating which causes less damage to the cathode tip during start-up. By the flattening the cathode tip is achieved that no melting of the tip and thus no alternating there is a restless approach to the arc, but instead a plasma hood surrounds the rounded cathode tip forms that can only shift a little.

In the drawing, an exemplary embodiment of a cathode for a high-pressure discharge lamp is shown in FIG the invention illustrated partially in section.

Fig. 1 shows a high pressure lamp approximately natural size;

Fig. 2 shows a cathode on an enlarged scale.

The anode 2 and the cathode 3 are arranged in the discharge tube bulb 1 of a noble gas high-pressure lamp, which is preferably made of quartz. The cathode consists of a tightly hammered thoriated tungsten body, which is cylindrical in its rear part 4 and ends in its front part as a pointed cone 5. The surface lines in an axial section plane of the conical tip form an angle α of approximately 40 °. The front part of the cathode tip is partially separated from the rear part by an annular incision 6, so that the heating occurring as a result of the discharge is dammed up and the heating start-up

309 648/116

done faster. In the cathode shown here for a noble gas high-pressure lamp for a power consumption of around 2500 W, the front tip of the cathode has a rounded tip with a radius b of 0.6 mm, around which a plasma hood is formed when the lamp is burning. The length of the cathode body is about 15 mm; the approximately 0.5 mm wide annular incision is provided at a distance of approximately 6.5 mm from the cathode tip in such a way that a web of approximately 3 mm diameter connects the front part 5 of the cathode to the rear part 4.

The anode 2 also consists of a tightly hammered one Tungsten body, which in the exemplary embodiment has circular grooves on its circumference. The anode can of course also have a different design than the one shown. The power supply rods 8 and 15 are pressure-tight in the foot 16 for the cathode and the foot 17 for the anode melted down. The base 18 (only shown for the anode) are used to hold the lamp and the Connection of the power supply to the ignition and operating equipment of the high pressure lamp.

Claims (3)

PATENT CLAIMS: a5 1. Cathode for a high-pressure discharge lamp, preferably noble gas high-pressure lamp with solid discharge-heated electrodes made of a tightly hammered activated tungsten body, which is advantageously made of tungsten in any way, z. B. by pressing, shrinking or welding, is fixed, characterized by such a shape that at a distance of less than half its length, calculated from the cathode tip, a temperature of at least 2000 ° C prevails by the conical tip of the Cathode is formed with an angle of less than 50 °, preferably 30 to 40 °, and has a rounded tip with a tip radius of more than 0.2 mm. 2. Cathode according to claim 1, characterized in that the conical tip of the cathode to achieve a build-up of heat at least partially through an annular incision, for example is separated from the rest of the cathode body perpendicular to the cathode axis. 3. Cathode according to claim 1 or 2, characterized in that the cathode body is less contains more than 6%, preferably about 3%, thorium oxide. Considered publications:
Kino-Technik, No. 11/1960, p. 340, image 5. 1 sheet of drawings © 309 648/116 7.63