US2939987A - Electron discharge tube - Google Patents

Description

June 7, 1960 H. T. MORRIS ETAL 2,939,987

ELECTRON DISCHARGE TUBE 2 Sheets-Sheet 1 Filed March 25, 1957 III FIG-.1

INVENTORS HAROLD THOMAS MORRIS PETER OWEN CHADD AGE T June 7, 1960 H. T. MORRIS ETAL 2,939,987

ELECTRON DISCHARGE TUBE Filed March 25, 1957 2 Sheets-Sheet 2 INVENTORS AG NT ELECTRON DISCHARGE TUBE Harold Thomas Morris, Earlswood, and Peter Owen Chadd, Warlingham, England, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware I Filed Mar. 25, 1957, Ser. No. 648,161

3 Claims. (Cl. 313-250) This invention relates to electron discharge tubes and has more particular reference to arrangements for mounting electrodes so that adjacent electrodes of an electrode system are supported at a predetermined spacing from each other. The invention is particularly applicable to the manufacture of electron discharge tubes of the disc seal type.

In such tubes, the anode and the cathode are usually adjusted with respect to an intermediate electrode in that the anode and the cathode are each screwed or slid into a cylindrical part of the wall so as to be situated at the correct distance from the intermediate electrode and then definitely secured. Since the spacing between the cathode and the next-following electrode is very critical and must also be very small, adjustment in this I way is very dilficult, the intermediate electrode already being sealed into the wall of the tube.

An assembly which is much simpler and more accurate may be obtained, if according to the invention, the cathode and the next-following electrode are jointly arranged on the part of the wall in the relative correct positions and the assembly is subsequently introduced into a second cylindrical part of the Wall containing the anode until two abutment surfaces engage one another whereafter the parts of the wall are sealed together. In this case, the critical adjustment of the cathode and the next-following electrode is efiected wholly outside the tube.

According 'to the present invention one electrode is mounted at one end of a tubular member which preferably is cylindrical and thus can exhibit considerable rigidity in spite of being very thin-walled, and a second electrode which it is desired to mount at a predetermined distance from the first electrode is carried on a support which is secured to the exterior of the tubular member. The support for the second electrode may comprise a pair of strap-like members which together embrace the tubular member and the ends of which project radially from the tubular member. To provide resilience in the mounting of the tubular member on its support, the end remote from the first electrode and beyond the point of attachment of the support for the second electrode, is slit to provide a plurality of fingers which can be bent to provide a resilient means for mounting the assembly of the two electrodes. Preferably, the tags formed by slitting the end of the tubular member are bent outwardly and their free ends are secured to the member constituting the support for the electrode assembly.

A preferred form of the invention is applied to a disc seal value will now be described by way of example with reference to the accompanying drawings in which Figure 1 shows part of the value consisting of the grid, cathode and foot assembly and Figure 2 shows a second part of the tube comprising a tubular glass envelope, an anode and a locating disc, both anode and locating disc being sealed into the envelope at disc seals.

Referring first to Figure 1, the foot portion consists United States Patent 2,939,987. Patentedune 7, 1960 a of a metal cylinder 1 to which is sealed externally a heated and comprises a fiat emissive surface and on the opposite face a cylindrical housing for the heating element 8. The cathode 5 is mounted at one end of a thin-walled metal cylinder 6 which can be produced by winding a strip of metal foil into a cylinder. Thefoil is preferably of relatively. poor thermal conducting material such as a nickel-iron alloy and with such a material a thickness of 0.025 mm. gives sufiicient rigidity while minimising the heat losses by heat conduction through the foil. The end of the foil cylinder 6 remote from the cathode 5 is slit longitudinally to form a plurality-of tags which are bent to extend radially outwardly and the free ends of which are secured to a supporting ring 7 mounted on the foot assembly. These radial tags provide the resilient mounting enabling the thin-walled cylinder 6 and the cathode 5 to move bodily relative to the foot assembly. The heater 8 is connected at one end to the wire 4 and at the other end to a stirrup 9 which extends across the top of the foot assembly.

The grid assembly is supported from the lower part of the cylinder 6 by means of a pair of straps 10, each of which extends substantially half-way round the periphery of the cylinder and terminates in radial extensions. Each of the two straps is spot-welded to the cylinder. Secured between the ends of the straps are metal rods 11 which are mechanically united by glass beads 12 to further metal rods 13 positioned within sleeves 14. These sleeves are utilized in the manner hereinafter described for securing the assembly of Figure l to the assembly of Figure 2. Also carried by the rods 13 are grid supporting wires 15 which carry the actual grid structure 16. The grid assembly consisting of the components 11 to 16 is first assembled and then as a unit is mounted on the straps 10. At this stage the rods 11 are frictionally held between the ends of the straps 10. This enables the grid assembly to be adjusted to position the grid wires at the required spacing from the end surface of the cathode 5. When this adjustment has been made the straps 10 are permanently secured to the rods 11 by spot-welding.

Referring now to Figure 2 the cylindrical glass bulb 17 consists of three sections which are united with a locating plate 18 and an anode structure 19 at two disc seals. The assembly of Figure 1 is introduced at the lower end of Figure 2 so that the upper surface of the grid assembly abuts against the lower surface of the locating plate 18. The tubular sleeves 14 pass through holes in the locating plate 18 and are then bent over by means of a tool introduced through the holes shown in the anode structure 19. By bending over the upper ends of the tubes 14, the grid assembly is firmly clamped against the locating plate 18 and is thus secured in the desired relative position to the working face of the anode 19. in this position the glass annulus 2 for the foot seal lies within the lower end of the cylinder 17 and the seal can be produced by normal heating techniques. Thereafter the upper end of the glass cylinder 17 is provided with an exhaust stem and the valve is exhausted and sealed in the conventional way.

What is claimed is:

l. A method of assembling an electric discharge tube including anode, cathode and grid electrodes comprising the steps, mounting the cathode on a first tubular member, resiliently securing said first tubular member to a support, mounting the grid electrode on a support, adjustably securing the grid support to the tubular cathode mounting member, adjusting the spacing between the grid "electrode and 'the cathode, and thereafter permanently securing the grid support member to the tubular cathode mounting member; mounting said anode on a first section of a second tubular member adapted to serve as an envelope for said tube, inserting the first tublflar member supporting-the cathode and grid electrodes into a second sectiontof the second tubular member, positioning the grid and cathode assembly in accu- 'rately pro-determined spaced relationship with said anode electrode with said sections adjoining one another, and sealing the two sections ofthe tubular member together.

a 2. A method of assembling 'an' electric discharge prising the steps, mounting the cathode electrode on a thin-walled tubular metal cylinder, forming slits in the endof thecylinderfremote from the cathode to form a plurality of resilient metal strips, securing said resilient metal strips to a hollow metal cylindrical support surrounded by a glass ring, connecting a supply conductor u tube including anode, cathode and grid electrodes com.-

2,939,937 l Y J and the cathode electrode,-securing the grid-supporting members after adjustment of the grid-cathode spacing to the radial extensions, introducing the cathode-grid electrode assembly into a first portion of a tubular member adapted to serve as an envelope for the tube, mounting the anode within a second portion of said latter tubular member, adjusting the spacing between the grid electrode and anode electrode, and sealing the two portions of the tubular member together. 10 5 3. An electric discharge tube comprising an envelope, a cathode electrode, a tubularxsupport for said cathode, the end of said tubular support being slotted to form a plurality of strips which are bent to form a resilient supportingstructurefor saidicathode, aftubular' base to which said strips are secured, a plurality of supporting rods secured to radial extensions of said=tubular cathode support, ,a grid electrode secured to the ends of said support rods, and spaced from the cathode, and an anode elec'trodejsecur'ed' to said envelope and spaced 20 from said grid electrode and said cathode electrode.

References Cited in the file ofthis patent UNITED STATES PATENTS Haas a May 22, 1951 UNITED STATES PATENT oTTTcE CERTIFICATION OF CORRECTION Patent No. 2,939,987 June 7, 1960 Harold Thomas Morris et al,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed specification, between lines 7 and 8, insert Claims priority, application Great Britain March 29, 1956 Signed and sealed this 25th day of April 1961,,

(SEAL) Attest:

ERNEST W SWIDER DAVID L: LADD Attcsting Officer Commissioner of Patents

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