US2163310A - Electron discharge tube and the like - Google Patents

Description

J1me 1939- c. F. MlLLER ELECTRON DISCHARGE TUBE AND THE LIKE Filed March 12, 1938 INVENTOR ay Patented June 20, 1939 Carl F. Miller, Emporium, Pa., assignor to Hygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts Application March 12, 1938, Serial No. 195,496

7 Claims.

Thisv invention relates to electron-discharge tubes and more especially to tubes of the evacuated type.

A principal object of the invention is to provide a novel method of supporting a getter within a radio tube. 1 Y

Another object is to provide a radio tube mount with a surrounding electrostatic shield and with a getter suspension which also functions to supplement the shield.

A feature of the invention relates to a getter carrier which may be located remotely from the press or stem of the tube, whereby the metal parts of the mount may be heated without flashing the getter.

A further feature relates to a novel getter suspension whereby selective heating of the tube parts and the getter is more easily controlled.

A further feature relates to the novel organization, arrangement and relative location of parts constituting an improved radio tube mount and getter.

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 disclosed herein, as

embodied in certain specific forms and as incorporated in one particular type of an electron discharge tube, it will be understood that this is done merely for explanatory purposes and not by way of limitation. Accordingly in the draw- Fig. 1 is a vertical elevational view of a shield electrode and getter suspension according to the invention.

Fig. 2 is a cross-sectional view of Fig. 1 taken along the line 2-2 thereof, as indicated by the arrows.

Fig. 3 is a modification of Fig. 1.

Fig. 4 is another modification of Fig. 1.

Fig 5 is a top plan view of Fig. 4.

Fig. 6 shows the assembly of Fig. 1 in a radio tube with its bombarding coil in position.

Fig. 7 shows the tube of Fig. 6 with the getter fiash coil in position.

. Fig. 8 shows the bombarding coil and a getter flash coil as used with a radio tube having the shield arrangement of Figs. 4 and 5.

In the manufacture of such devices as evacuated radio tubes and the like, it is the usual practice to subject the tube to a predetermined exhaust schedule and after the enclosing bulb has been evacuated to a certain extent, the various metal parts contained therein are raised to a sufficiently high temperature to drive out occluded gases therefrom. As a final step in the evacuation of the tube, it is the usual practice to flash or explode a substance for scavenging or gettering the residual gases within the tube. The material employed for this purpose is designated in the art as a getterfi. Consequently, it becomes important to provide some sort ,of selective heating of the mount per se as compared with the heating of the getter material, and various methods of effecting this selective heating have been proposed heretofore. In accordance with the present invention, the, getter material is .carried by a getter support which forms or supplements one of the electrodes of the mountpreferably, a shield electrode thereof. Consequently, the support or carrier for the getter material performs its ordinary function as a suspension and also as a supplement to the electrostatic shielding of the shield electrode. One typical arrangement that may be used is illustrated in Fig. 1 wherein the numeral I represents a metal cup-shaped electrode or shield such as is known in certain types of radio tubes and. as disclosed for example in detail in application Serial No. 189,295, filed February 8, 1938. As shown in cross section in Fig. 2, the electrode forms a single turn inductive loop and advantageis taken of this fact to heat the shield for driving out occluded gases and the like. The shield I is provided with a cut-out or window 2 which may be circular, rectangular or any desired shape. Positioned within the window 2 and in spaced relation to the border thereof, is a correspondingly shaped metal member 3 which may, although not necessarily, be of the same material as the shield I. The member 3 is suspended in spaced relation to the border of window 2, preferably by a relatively thin Wire 4 which may be welded to the shield l and t0 the member 3. The member 4 is preferablyof electrical conductive material but is chosen, either as to smallness of cross section or as to composition, to act as a comparatively poor conductor of heat with respect to the conditions under which the shield I is later heated. Attached in any convenient manner to the member 3 is a relatively small quantity of getter material 5 of any composition well known in the radio tube art. Preferably, although not necessarily, the member 3 is provided with a central recess to receive the getter 5, and if desired, a perforate or porous cover may be welded to the member 3 to prevent the getter material being accidentally dislodged, While permitting it to be flashed in the well known manner. As shown in Fig. 2, the member 3 may be curved to form to the peripheral curvature of the shield, so that, so far as electrostatic shielding action is concerned, the shield by reason of the member 3 is peripherally and vertically complete except for the relatively minor spacing which exists between member 3 and the window 2. However, this spacing is so small as to have inappreciable effect on the electrostatic shielding.

Fig. 6 shows in partial cross-section a typical radio tube embodying the composite shield and getter support of Figs. 1 and 2. This tube may comprise an enclosing glass envelope 6 provided with a base I and with the usual contact prongs 8. The mount is shielded by the shield I which is supplemented by the rim of base I as described in application Serial No. 189,295, filed February 8, 1938, it being understood that said rim is of metal and overlaps vertically the lower end of shield I. Supported within the envelope 6 is any well known form of radio tube mount comprising for example an electron-emitting cathode 9, at least one wire wound grid I and a plate or anode II. In the particular type of mount shown in Fig, 6, the control grid is provided with side rods I2, I3, which extend upwardly through the top of the shield I. The top of shield I may be provided with a window I4 to allow the grid side rods to pass through the shield without being shortcircuited, it being understood of course that a suitable mica disc spacer I5 is employed for this purpose in the manner well known in' the radio tube art. For a detailed description of a mount of this character, reference may be had to said application Serial No. 189,295. The side rods I2, I3 may be connected by a strap I6 and thence to the usual top cap II.

The tube is subjected to any predetermined exhaust schedule during which the various metal parts are heated, preferably by electromagnetic induction, to drive out occluded gases and the like. Thus as indicated in Fig. 6, a bombarding coil I8 is positioned around the tube, this coil being energized preferably by a high frequency alternating current so as to induce heating currents into shield I in the well known manner. Because of the poor heat conductivity of the member 4, the shield I can be raised to an outgassing temperature without raising the getter material 5 to flashing temperature. After the metal parts have been thus outgassed, the bombarding coil I8 is removed and a small flash coil I9 is positioned adjacent the member 3 as indicated in Fig. 7.'

The coil I9 is likewise energized by a high frequency alternating current so as to raise the member 3 to a sufficiently high temperature 'to flash the getter 5 after which the tube may be sealed ofi in the usual manner.

Instead of positioning the getter carrier 3 midway of the height of shield I, it may be positioned at the lower end thereof as indicated in Fig. 3. In tubes where no top cap, corresponding to cap I! is employed, the getter carrier may be positioned at the top of the shield, this arrangement being shown in Figs. 4, 5 and 8. With this arrangement, the bombarding coil land the flash coil I9 may be positioned coaxially instead of at right angles, as is necessary with the embodiments of Figs. 1 and 3. The arrangement of Fig. 8 also has the advantage that the getter carrier 3 closes off the opening I4 in the top of the shield thus further enhancing the electrostatic shield, and there is very little danger of the condensed flash material depositing on parts of the mount where' it will interfere with the proper operation of the tube. The manner of bombarding the metal parts of the tube of Fig. 8 by the coil I8 and the manner of flashing the getter 5 by the coil I9, are similar to those describedin connection with Fig. 6. While the invention has'been described with the carrier 3 forming a part of the shield I, it will be understood that it may form part of the plate electrode in any case where the shield I is omitted.

Various changes and modifications may be made in the particular embodiments disclosed without departing from the spirit and scope of the invention.

What I claim is:

l. A radio tube mount including a tubular metal electrode having an opening in the wall thereof, and a getter carrier mounted within said opening.

2. A radio tube mount. according to claim 1 in which the getter carrier is mounted in spaced relation to the border of said opening.

3. A radio tube mount according to claim 1 in which the getter carrier is mounted within the opening in electrical conductive relation with the electrode but in poor heat conductive relation.

4. A radio tube mount according to claim 1 in which said opening is intermediate the ends of said electrode.

5. A radio tube mount according to claim l-in which said opening is at the lower end of said electrode.

6. A radio tube mount according to claim 1 in which the electrode is in the form of a metal cup and the opening is in the transverse wall of the cup.

7. An electrostatic shield arrangement for a tube mount comprising. a tubular metal shield having a window in a wall thereof, a metal member mounted within said window in slightly spaced relation to the border thereof, said metal member carrying a quantity of getter material, and another member electrically connecting the firstmentioned member to said electrode, said other member having a relatively lowheat conductivity.

CARL F. MILLER.

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