US2521451A - Electrode for electric discharge tubes - Google Patents

Description

P 1950 1 R. F. CRONERT 2,521,451

ELECTRODE FOR ELECTRIC DISCHARGE TUBES Filed Oct. 7, 1948 Patented Sept. 5, 1950 Rickard Folke Cronert, Enskede, Sweden, assignor to Lumalampan Aktiebolag, Stockholm, Sweden, a corporation of Sweden Application October 7, 1948, Serial No. 53,345 In Sweden March 1, 1948 2 Claims.

This invention relates to an electrode for cold cathode electric discharge tubes.

The electrode referred to consists of a sleeve, preferably with closed bottom, the upper rim of which, facing the discharge, is covered by two thin superpositioned discs of mica or similar insulating material provided with centre openings for the discharge are and held in position by fastening means. The under disc is attached to the rim fasteners protruding from the rim and bent down over said disc, and these bentdown fasteners are covered by the upper disc, attached to the former disc by means of fasteners electrically separated from the first-mentioned ones. As no electrical conducting connection exists between the elements holding the discs together and the electrode sleeve a stabilized arc is effected and the discharge concentrated to the sleeve interior. Blackening of the tube end is avoided as no sputtering can occur from the rim of the sleeve. The electrode sleeve is covered on the inside with a layer of emitting material.

The electrode according to this invention I is very simple to manufacture and offers special advantages in connection with degasification of the electrode, which must be carried out during manufacture of the discharge tube. The insulating discs which cover the upper part of the electrode, can be made so wide that they practically extend to the wall of the discharge tube. When degasifying the electrode, which usually is done by heating with a high frequency coil, heating can be carried to a very high temperature. The insulating discs support the electrode sleeve so that the latter does not come into contact with the wall of the discharge tube and causes bursting of the envelope.

This invention will be described in connection with an example of construction as shown in the accompanying drawing forming a part hereof. Fig. 1 shows a longitudinal section through an electric discharge tube provided with an electrode arrangement made in accordance with this invention taken along the line of Fig. 3. Fig. 2 shows the upper part of the same electrode in a longitudinal section along line 22 of Fig. 3 and extending at a right angle to the section shown in Fig. 1. Fig. 3 is a cross section through the tube with the electrode arrangement seen from above.

The end of discharge tube 3 is closed in a known way by means of a lamp stem 4, in the compressed part 5 of which two lead-in wires 6, 6 are sealed. To the upper parts of these lead- 2 in wires 6, 6 an electrode sleeve is welded in the following way. The electrode sleeve 8, which consists of a piece cut from an iron tube of suitable dimensions, is provided at its lower end with a suitable cap 1. The respective lead-in wires 6 are attached to the inside of the cap collar 7 and to the adjacent part of sleeve 8 by spot welding. At the upper end of the sleeve, also by means of spot Welding, two pins '9, 9 are attached at two diametrically opposite points. The upper edge of sleeve 8 is covered by a mica disc l5 provided with holes [0, l0, so that the disc can be threaded on over the pins 9, 9. After putting on the disc, the top parts II, II of the pins are bent down over mica disc I5. On top of mica disc I5 is placed another mica disc M, which by means of two U-shaped clamps is secured to mica disc 15. These clamps I6, 16 are attached at two diametrically opposite points of the edge on the discs and are, as will be seen from Fig. 3, arranged along a line 22, which runs at a right angle to line l-|, along which pins H, I I are attached. These clamps l6, it, which are turned towards the discharge gap, are thus by safe insulation separated from the electrically conducting electrode parts, which are hidden by the mica discs. Mica discs 14 and I 5 are provided with centre openings, l3 and I2 respectively, which permit the discharge are to pass through to the interior of electrode sleeve 8. The inside of the electrode sleeve 8 is suitably covered with a layer of electron emitting material. The insulating discs i4 and I5 extend nearly to the wall of tube envelope 3, which permits the electrode to be supported in the above described way by these discs during degasification.

The construction shown is only to be regarded as an example. It is not always necessary to provide the electrode sleeve 8 with a bottom, or, if such a bottom is suitable, the sleeve may be pressedin one piece with such a bottom. To cut the electrode sleeves from a tube, as mentioned above, is, however, very advantageous from the viewpoint of manufacture. Instead of pins '9, 9, lugs can be punched out on the upper parts of the electrode sleeves; and instead of the clamps [6 shown, other fastening devices can be used, for instance fastening by means of wire clips as used for fastening paper together by means of a paper fastener, attaching by means of riveting, etc.

What I claim is:

1. In a cold cathode electric discharge tube having a tubular envelope, an electrode comprising a metal sleeve extending axially centrally of the envelope adjacent to one end thereof, metal fastening elements extending from the inner end of the sleeve, a thin disc of insulating material disposed across said end of said sleeve, said fastening elements comprising diametrically opposed pins extending through the disc to secure it in place, a masking disc of thin insulating material disposed inwardly of and. adjacent to the first mentioned disc and fastening means engaging said discs at their peripheries for securing them together, said fastening means comprising diametrically opposed clips peripherally 01T- set from the diametral plane passing through said pins and said discs extending to the vicinity of the wall of the envelope and being provided REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,984,482 Imamura Dec. 18, 1934 2,118,981 Muncheryan May 31, 1938 2,244,070 Kurz June 3, 1941 2,310,983 Miller Feb. 16, 1943 2,375,808 Miller May 15, 1945

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