US2075611A

US2075611A - Electron discharge tube and the like

Info

Publication number: US2075611A
Application number: US95981A
Authority: US
Inventors: Eugene J Hoffman
Original assignee: Hygrade Sylvania Corp
Current assignee: Hygrade Sylvania Corp
Priority date: 1936-08-14
Filing date: 1936-08-14
Publication date: 1937-03-30
Anticipated expiration: 1954-03-30

Description

March 30, 1937.

E. J. HOFFMAN I ELECTRON DISCHARGE TUBE AND THE LIKE Filed Aug 14, 1936 INVENTOR ATTORNEY Patented Mar. 30,1937

UNITED STATES PATENT OFFICE Eugene J. Hoffman, St. Marys, Pa., assignor to Hygrade Sylvania Corporation, Salem, Mass., a. corporation of Massachusetts Application August 14, 1936, Serial No. 95,981

Claims.

This invention relates to electron discharge tubes and more particularly to such devices as thermionic valves employing a filamentary cathode.

5 An object of the invention is to provide an improved manner of supporting and anchoring a filament in a thermionic tube.

One of the chief causes of so-called microphonic noises during the operation of a filament type tube or valve, is the loose connection that usually exists between the bight of the filament and its resilient supporting hook. I have found that by employing special materials to bond. the

filament bight rigidly to its supporting hook, these microphonic noises are materially reduced. Preferably the bonding material is such that it may be applied in liquid or semi-liquid form after the assembly of the mount so that the subsequent heat treatment of the assembled tube will cause a hardening of the bonding material.

Accordingly a feature of the present invention relates to a thermionic valve or the like, having a filament with a bight which is supported by a resilient hook, the bight being integrally and rigidly bonded to the hook by specially chosen materials which will not interfere with the proper operation of the valve as for example releasing undesirable gases, causing chemical corrosion between the bight and the hook, and the like.

A further feature relates to the novel organization, arrangement and relative location of parts which go to make up a thermionic valve mount of the filamentary cathode type which is singularly free from microphonic noises during operation.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

While the invention will be described as embodied in one particular type of thermionic valve or tube it will be understood that this is done merely for purposes of explanation and not by way of limitation. Accordingly in the-drawing,

Fig. l is a view, partly sectional, of a triode mount embodying features of the invention.

Fig. 2 is an enlarged View of the manner of bonding the filament bight to its supporting hook.

Referring to Fig. 1 there is shown a typical mount for a three element tube or triode. The mount comprises a base or stem 1 into which are sealed the various lead-in and support wires 2 to 8 inclusive. The'support wires are preferably spaced apart at their upper ends by a suitable insulator disc such as a mica disc 9 which may be attached as for example by the metal tabs or straps It! to the tubular plate or anode II, the latter being carried by the wires '2 and 8. Likewise the wire-wound grid 12 is carried by the

wires

3 and 1. The cathode I3 is in the form of a wire or ribbon filament provided with a coat-' ing of a suitable electron emissive material or materials as is well understood in the art. The free ends of the filament l3 are welded or otherwise conductively attached to the wires 4 and 6, while the bight of the filament is supported by a fine spring wire hook M. For this purpose there is provided the wire arbor 5 which preferably extends upwardly outside the plate H and projects upwardly beyond the mica disc 9. The fine spring wire hook I4 may be welded or otherwise fastened to the upper end of arbor 5 as shown more clearly in Fig. 2. The center of disc 9 is provided with an opening IE to allow the hook I4 to extend therethrough to engage the bight of the filament l3. In the usual tube, reliance is placed upon the natural springiness of the hook to maintain the filament taut and to maintain the hook in contact with the bight. I have found however that this loose contact between the filament hook and the bight of the filament is the cause of very much microphonic disturbance when the tube is in operation. I have also found that this microphonism can be very materially reduced by rigidly bonding the filament hook to the filament bight. However because of the limitations of temperature, gas-release and the like the usual materials employed for bonding are not suitable as applied to thermionic valves or tubes. Furthermore because of the delicate nature of the filament and its hook, and also because of the necessity of maintaining the spacing of the electrodes undisturbed once they are properly assembled I have found it necessary to employ as the bonding material a substance that can be applied in the liquid or semi-liquid state but which upon suitable drying or heat treatment hardens to form a solid rigid bond. As examples of such materials I may mention a powdered refractory metal oxide or mixture of such oxides carried in a liquid vehicle or binder which can be volatilized during the heat treatment of the tube without danger of contaminating or otherwise interfering with the desired characteristics of the tube. For example beryllium oxide may be mixed with a suitable binder preferably, although not necessarily, an inorganic binder such as a water or alcohol solution of a hydrolyzed nitrate, to form a liquid or semi-liquid paste.

When the mount has been completely assembled and the parts adjusted to their proper spaced. relation, and with the filament bight in engagement with the hook, a small quantity of the above-described material is applied as for example by means of a small brush to the hook as shown in Fig. 2. The material is then allowed to dry either naturally or by heating it to drive off the liquid vehicle whereupon the refractory oxide solidifies to form a rigid bond l6 between the filament bight and the hook, thus preventing relative movement therebetween.

The following is one particular method of preparing the binder or liquid vehicle for the refractory metal oxide which has been found. satisfactory. Beryllium or aluminum preferably in powdered form is added to an acid such for example as nitric acid, the metal and acid being present preferably in respective molar proportions in excess of those necessary to produce a normal orneutral nitrate. The resultant solution has the apparent characteristics of a hydrolyzed nitrate of aluminum or of beryllium depending upon which metal is used. This nitrate is then dried in any suitable manner preferably over a water bath to produce a clear non-crystallized solid substance. This solid is then dissolved in water or in an alcohol to produce the viscous liquid vehicle to which the powdered refractory metal oxide such as beryllium oxide, aluminum oxide may be added. This mixture is then applied to the filament hook as above-described.

The above-described procedure produces a solid rigid insulating bond between the filament bight and its hook. In certain cases however it may be desirable to have this solid bond conductive. In such cases the bonding material may be applied in the form of a solution of Aquadag diluted with ammonia and water or alcohol.

While specific materials and methods of preparation have been described herein various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What I claim is:

1. In a radio tube mount the combination of, a filament having a bight portion, a filament tensioning member having a hook engaging said bight, and a solid mass of refractory material rigidly bonding said bight to said hook.

2. In a radio tube mount the combination of,

a filament having a bight portion, a filament tensioning member having a hook engaging said bight, and a solid mass of a refractory metal oxide rigidly bonding said bight to said hook.

3. In a radio tube mount the combination of, a filament having a bight portion, a filament tensioning member having a hook engaging said bight, and a quantity of a refractory material capable of being applied to the bight and hook in a semi-liquid condition and capable of being dried to form a solid rigid bond between the bight and hook.

4. In a radio tube mount the combination of, a filament having a bight portion, a filament tensioning member having a portion engaging said bight; and a mass of refractory powdered material having a hydrolyzed metallic salt binder to form a solid rigid bond between said bight and tensioning member.

5. In a radio tube mount the combination of, a filament having a bight portion, a filament tensioning member having a portion engaging said bight, and a solid mass of refractory material forming a rigid bond between the bight and tensioning member and consisting of a dried solution of Aquadag.

EUGENE J. HOFFMAN.