US2030361A

US2030361A - Electrode mounting

Info

Publication number: US2030361A
Application number: US685204A
Authority: US
Inventors: William W Eitel; Mccullough Jack
Original assignee: Heintz & Kaufman Ltd
Current assignee: Heintz & Kaufman Ltd
Priority date: 1933-08-15
Filing date: 1933-08-15
Publication date: 1936-02-11
Anticipated expiration: 1953-02-11

Description

Feb 11, 1936. w. w. EITEL ET AL.

ELECTRODE MOUNTING Filed Aug. 15, 1955 INVENTORSW WILL/AM n E/TEL.

JACK Mc CULLOUGH.

' ATTORNEY Patented Feb. 11, 1936 ELECTRODE MOUNTING William W. Eitel and Jack McCullough, San

Bruno, Calif., assignors to Heintz & Kaufman, Ltd., San Francisco, Calif., a corporation of Nevada Application August 15, 1933, Serial No. 685,204

3 Claims.

Our invention relates to means for and method of mounting an electrode, and more particularly to mounting electrodes in a thermionic tube.

Among the objects of our invention are: To provide a means and method of mounting electrodes in a thermionic tube whereby strength and rigidity of structure is obtained; to provide a three point support for electrodes mounted within a thermionic tube; to provide long leakage paths between electrodes in a thermionic tube; to provide a means for and method of mounting electrodes in a thermionic tube of cylindrical shape without materially changing the contour of the envelope; and to provide a thermionic tube of minimum size having long leakage paths between electrode supports.

Other objects of our invention will be apparent or will be specifically pointed out in the description forming a part of this specification, but we do not limit ourselves to the embodiment of our invention herein described, as various forms may be adopted within the scope of the claims.

Before the advent of extended use of the higher radio frequencies in radio communication, it was customary to mount all the electrodes of a multielectrode thermionic tube capable of self-oscillation or amplification, on .a single envelope extension or stem, usually reentrant, the supporting leads being sealed through a single pinch or fused portion of the stem. Of necessity these leads were close together and practically parallel while passing through the seal.

When, however, such devices were used for high frequency oscillation generation or amplification, electrolysis of envelope material and consequent shorting occurred at the pinch, necessitating complete separation of the anode, cathode and control electrode leads. This separation in turn has led to the mounting of such electrodes from the sides, top and bottom of the tube envelope in projecting arms, thus greatly enlarging the over-all space required to house the tube.

It is also important in modern tubes that the electrodes be firmly secured to the envelope and that they be so mounted as to prevent relative motion under the influence of heat, electrical fields or mechanical vibration. The present custom of mounting in side or end envelope arms places the electrode, which is usually quite heavy especially in the power tubes, at the end of a long support, and slight distortions of the envelope material cause large displacements of the electrode. As the electrode mounting points are widely spaced, motion of the electrodes relative to one another is difiicult to prevent. Insulators locking the electrodes against such movement are difficult, if not, impossible, to install in this type of tube, as the spaced mounting points necessitate individual insertion and sealing of the various electrodes.

Our invention attains, in broad terms, wide spacing of the electrode mounting points with minimum length of support within an envelope, by providing the electrodes, which are preferably cylindrical, with support members, preferably three peripherally attached wires. The ends of these wires are beaded with a material which will seal readily to the envelope material. If the envelope be of a certain type of glass, for example, the beads may be of the same type, or one so closely allied as to seal to the envelope without developing strain at the point of fusing. It is also desirable that the bead make good contact and stick tightly to the end of the support wire. If an envelope of the usual shape is used, having a hemispherical end and cylindrical side walls, the beads may be sealed either to the end portion, or by bending the support members outwardly, to the side walls. It is often desirable to seal one electrode to the end portion and one or more others to the side walls, leaving the remaining end for sup-porting other electrodes which do not require such wide spacing of leads or mounting supports, such as a cathode for example.

The broad aspects of our invention may be more fully appreciated by reference to the drawing in which:

Figure l is a view in elevation of a step in the mounting of an electrode within an envelope in accordance with our invention.

Figure 2 is a View partly in section and partly in elevation of the mounted electrode.

Figure 3 is a sectional View taken as indicated by the line 3-3 in Figure 2.

Figure 4 is a longitudinal view partly in section and partly in elevation of an envelope having two electrodes mounted therein.

In the preferred embodiment illustrated, an envelope l, preferably having a hemispherical end 2 and a cylindrical side wall 4, is provided with a tubulation 5. We have shown this tubulation as being in the center of the hemispherical portion, although it may be in other locations, or omitted as will be later explained. The envelope illustrated is of the size and shape hitherto used in the popular 50 watt three-electrode oscillator and amplifying tube, in which all electrodes have formerly been mounted on a reentrant stem sealed in the end opposite the hemispherical portion, and is customarily blown from borosilicate glass, known in the art under the trade-name "Pyrex, or a closely allied glass sold under the trade designation of G702P.

An electrode, in this example a cylindrical anode 6, provided with fins l to increase heat dissipation, has welded thereto anode support members 9 preferably peripherally arranged, equally spaced and three in number. These support members extend beyond the anode, and are preferably made from tungsten wire. As either of the above mentioned glasses seal readily to tungsten, the ends of the support members may be covered with small portions of such glass to form support beads I 0 which adhere firmly to the wires. As is well known in the art, G702P seals to tungsten better than Pyrex and as the latter glass is somewhat harder than the former, it is customary to make the portion of the envelope through which tungsten leads are sealed of G702P, the remainder of the envelope being Pyrex. Following that teaching we prefer therefore to bead the wires with G702P and make the main body of the envelope of Pyrex, the two glasses, however, being so closely allied that they will fuse without strain.

If it is desired that a lead separate from the support members he provided for the electrode,

an anode lead I l is provided with a lead bead E2,

and is connected to the anode by a flexible link M.

A step in the mounting of the electrode is shown in Figure 1. Here both the envelope and the beaded anode are chucked in a glass working lathe and rotated, a narrow fire I5 being used to heat the support beads l8 and a broader fire l6 employed to heat the hemispherical end portion. When the heated portions reach fusing temperature, the anode is moved inside the envelope until the beads touch the hemispherical portion and fuse thereto. The rotation is continued and the end annealed by gradual reduction of the temperature of the broad flame. The heat is then withdrawn and the anode mounting is complete. During the fusing the anode lead has entered the tubulation and the anode lead bead sealed to the envelope. The completed mount is shown in Figure 2.

The mount thus formed is exceptionally sturdy. It gives a short three-point support for the anode, and as the mounting operation may be performed on a lathe the spacing relations between the envelope and the anode can be made absolute and uniform in quantity production. There is no disturbance of the exterior surface of the envelope, its contour remaining unchanged. It is, however, possible to omit the special anode lead, tubulate off center and run one or more of the anode support members through the glass to obtain the electrical connections. We prefer, however, to utilize the separate lead.

The same general method may also be used to support electrodes from the cylindrical side wall 4. Figure 4 shows an example in which the anode has been mounted as above described, and in which an additional electrode, a grid I! was provided with grid support members I8 which were outwardly bent, and the ends beaded. In this case the grid and envelope were chucked and rotated with the grid in the final position, the support beads being located closely adjacent the side wall. Fires were then applied to the outside of the envelope opposite the beads. The force of the fires, after the envelope heats, causes the side wall to contract sufficiently to melt down on the beads, fuse thereto, a slight internal air pressure being sufficient to restore the side wall to its original shape, slightly elongating the bead seal. The envelope is then annealed and removed from the lathe.

We then have a concentrically mounted grid and anode, each supported at three points from the inner surface of the envelope. As they both were accurately positioned when mounted they are in definite spaced relationship and remain so during operation of the tube, the shortness of the support members and the three-point support resisting all warping tendencies.

The remaining end of the tube may be used to mount a cathode on a stern in the usual manner, a grid lead 19 passing through the envelope at any convenient point apart from the cathode leads, preferably through the stem seal.

It will be apparent also that additional concentric electrodes may be mounted inside of the grid I? in exactly the same manner as the grid was mounted, the leads from these other electrodes each made a little longer than the one before to place the bead seals of each on a lower level, or the bead seals may be staggered on the same level without lengthening the supports.

Apart from the sturdiness and absolute alignment, other advantages are apparent. The size of the original envelope is not enlarged and no side arms are used to increase the space needed to mount the tube. The anode supports are widely separated from those of the other electrodes and '75 to or more watt structures may be placed in the envelope of the usual 50 watt size and then used for high frequency work. High power tubes made as described are ideal for air- 3' craft transmitters where space is at a premium, and the rigid construction eliminates all trouble from vibration.

We claim:

1. In combination, an envelope having a hemispherical end and cylindrical side walls, an anode having spaced circumferentially attached leads extended from one end of said anode only, said leads being separately sealed to said hemispherical end, and a cylindrical grid concentrically poof said envelope above the level of said anode, and

a second tubular electrode positioned within said anode by electrode supports extending only from the end of said tubular electrode opposite to the support attachments of said anode and terrninat ing in the envelope side walls below the level of z said anode whereby the respective envelope terminations of said supports are separated by a distance at least equal to the length of said anode.

3. In combination, an envelope, a pair of concentric tubular electrodes therein, one of said electrodes being supported solely by a plurality of support wires extending from one end thereof and separately sealed to said envelope, and the other electrode being supported solely by support means extending from the other end thereof and terminating on the side walls of said envelope, the respective support terminations being separated by at least the length of said electrodes.

WILLIAM W. EITEL. JACK MCCULLOUGH.