US2782338A - Grid alignment in electron tubes - Google Patents

Description

Feb. 19, 1957 w. J. RHYNE GRID ALIGNMENT IN ELECTRON TUBES Filed D6 1953 D8 0 aouo v? Mum Feb. 19, 1957 I w. J. RHYNE 2,782,338

GRID ALIGNMENT IN ELECTRON TUBES Filed Dec. 9, 1953 GRID ALIGNMENT IN ELECTRON TUBES William LRhyne, Prospect Park, Pa., assignor to Sylvania Electric Products Inc., a corporation of Massachusetts Application December 9, 1953, Serial No. 397,131

4 Claims. (Cl. 313-299) This invention relates to means and methods-for mounting and aligning the grid elements of an electron discharge device and more particularly to meansand methods for mounting and aligning the grid elements of a beam. type electron discharge device.

In a conventional beam type tube such as the '6L6G, the electrode mount is assembled by threading the upper and lower extremities of support elements for the electrodes through upper and lower insulating spacers, said spacers having apertures therein for positioning and retaining the support elements, and therefore the electrodes with respect to each other. Upon completion of this mount assembly, weld connections are made between grid side-rods and their corresponding stern leads. Lateral wires of the grid are then visually aligned with one another. Since this assembly operation includes mounting and welding the anode in its final position, visual observation necessary for alignment of the grids is obstructed by the anode.

Heretofore, several procedures and means have been devised to accomplish and maintain correct grid alignment until the construction and processing of the tube has been completed. In each procedure the configuration of the anode was made so as to facilitate observation of at least several turns of the grid lateral wires by the mounting operator. One method utilizes an observation window cut into the central region of the anode. Another method relies on an anode which has a smaller axial length then the axial length of the grid lateral wire coverage so that several lateral wire turns can be observed either above or below the edges of the anode. Still another method uses anode half plates so that alignment of the grids can be made after one of the anode half plates has been mounted, and before the opposing half plate is welded in position.

These procedures have the disadvantages of not providing for sufficient grid coverage by the anode, or requiring additional steps in the fabrication of the anode,

or of limiting grid lateral wire area available for'observation during the alignment operation.

One object of this invention is to obviate the aforesaid difiiculties in the manufacture of a beam type electron discharge device.

Another object is to provide in a device of the aforesaid character, a better grid alignment, thereby providing for a more efficient beam type device.

A further object is to provide for improved means for firmly and accurately positioning the electrodes of an electron discharge device with respect to each other within the envelope.

A still further object is to provide for improved means for restricting the vibrational movement of the electrodes of an electron discharge device under operating conditions A still further object is to provide for an electron discharge device with a very low microphonic characteristic.

A still further object is to-provide an improved method nited States Patent 'ice for constructing a beam type electron discharge device, and more particularly for an improved method of mounting and laterally aligning the grids of a beam type electron discharge device.

A beam type electron discharge device according to the present invention relates to a tube comprising a cathode, an anode, beam confining plates, and a plurality of nested grids. These grids are all wound with the same number of lateral wire turns per inch so that each lateral wire turn of one grid shades the corresponding lateral wire turn of another grid from the cathode. The beam confining plates substantially limit the flow of electrons to the area. of the anode which faces the minor axis of the grids.

For a better understanding of the invention, reference is made to the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a partially sectionalized perspective view of an electron discharge device made in accordance with my invention.

Fig. 2 is an exploded view of an electron discharge device mount embodying the elements constituting my invention.

Fig. 3 is a view of the front of two grids which are not laterally aligned.

Fig. 4 is a similar view of the same two grids after they have been properly laterally aligned.

Fig. 5 is a plan view of an electrode mount made in accordance with my invention showing a top spacer parti ally cut away to expose a lower spacer.

The electron discharge device shown in Fig. 1 has a conventional vacuum tight enclosure or envelope 1t) and external circuit connecting pins 12. Mounted within the envelope are the conventional elements of a multi-grid tube, supported and positioned by the insulating spacers 14 and 16.

' In accordance with my invention the cathode 18, control grid 20, screen grid 22, and beam confining plates 24 are supported and correctly positioned withrespect to .each other at their lower extremities by an insulating spacer l4, and at their upper extremities by an aligning insulating spacer .26 in addition to the insulating spacer 16. The aligning spacer 26 is mounted between the lower surface of the spacer 16 and the upper lateral wire turns of the grids 20 and 22. In this construction it can be seen that spacer 26 is Within the confines of anode 28. The anode 28 is supported at its lower extremity by the spacer 14 and at its upper extremity solely by the spacer l6.

The method of mounting the electrode of the electron discharge device embodied in my invention is best shown in Fig. 2. The cathode 18 is first threaded through the central aperture of spacer 14. The control grid 20 and screen grid 22 are then dropped over the cathode 18 and the side-rods of these grids are threaded through corresponding apertures in spacer 14. The beam confining plates 24 are subsequently positioned by threading their mounting appendages 30 through the corresponding apertures inspacer 14. The aligning spacer 26 is then slipped over the electrodes by orientating and associating the apertures in the aligning spacer 26 with the cathode 1S, side-rods of the grids 2t) and 22, and mounting elongated appendages 31 of the beam confining plates 24. When this sub-assembly i completed, the side-rods of the grids 20 and 22 are welded attheir lower extremities to the leads 34 protruding from the stern.

Fig. 3 indicates the axial displacement of the leteral wires of the control grid 20 with relation to the lateral wires of the screen grid 22 which may occur after the aforementioned Welding operation has been completed. The grids 2t 22 are at this time supported against vertical movement at their lower extremities by the weld connections to the stern leads 34 and transversely supported at their lower and upper extremities by spacers 14 and 26. The next step in the process is to laterally align the grids. This is effected by bending such stem leads 34 as is requisite to raise and lower the grids 20 and 22 to effect the alignment. Fig. 4 shows such alignment of grids. These grids will retain this position through subsequent operations and processing of the tube.

To complete the assembly, the anode 28 is slipped over the anode support rods 32 and the spacer 16 is placed in position by orientating and associating the mounting support elements of the cathode 18, grids 20 and 22, beam confining plates 24, and anode 28 with the con responding apertures in spacer 16. The necessary remaining welds and electrical connections are then made to complete the electron discharge device mount assembly. It is possible to so position the anode on the rods 32 because of the spacer 26 being of a size to fit within the confines of anode 28 as shown in Figures 2 and 5.

Another notable feature present in an electron discharge device made in acordance with my invention means, namely spacers 16 and 26, provided at the upper extremities of the support rods for the cathode 18, grids 20 and 22, and beam confining plates 24. Since the upper part of the electrode mount is normally less secure than the lower part, this double retention means is very efficient. It is generally accepted in the tube making industry that vibrational movement of the grids and beam confining plates under tube operating conditions are the chief causes of microphonism. Since the spacer 26 is positioned very close to the top lateral turns of the grids 20 and 22 and abuts the upper edges of the beam confining plates 24, these elements are held in an unusually secure position. This holding of parts securely in position is enhanced by spacing the element 26 away from the spacer 16, thereby securing three level supports for the tube elements.

Another advantage of the method of mounting the electrodes for an electron discharge device is the simplified manner in which thi mounting operation is achieved. My method provides for an increase in manufacturing efiiciency due to the decrease in grid losses over those occurring in normal mounting operations, and to a decrease in the amount of tubes rejected for high screen current in a beam type tube. These losses are caused by a displacement of one or more of the grid lateral wires resulting from the anode being bumped against one or more of the grids during the anode dropping operation. Heretofore the cathode 18 and grids 20 and 22 were threaded into the apertures in spacer 14 and then the anode 28 was dropped over these and into position. Since the grids are retained only by the spacer 14 during the anode mounting operation, they often assume a position which is not perpendicular to the planar surface of the spacer and therefore cause difliculty in getting the anode over the grids without bumping them. The majority of the losses has been caused by displacement of the first few top turns of the grid 22.

Utilizing the electrode mounting method of the invention avoids afore-mentioned difiiculties since the spacer 26 is mounted prior to the anode dropping operation, thus supporting and positioning the grids before the operation. An important feature of this method is the physical protection of the grid lateral wires against damage by the spacer 26 While the anode is being placed in position. The importance of this novel process will be more fully appreciated with a realization of the small distances between the elements with which the mounting operator must contend.

I have found that the methods employed by me in the construction of electron discharge devices produces a more efficient tube with a correspondingly greater power output and lower screen current than heretofore, since it provides for visual observation of the entire axial length of the grids during the alignment operation and from both sides of the mount; furthermore, my method insures this alignment to remain intact during subsequent assembly and processing operations. In addition, I have found that the unique double retention means provided at the upper extremities of the mount electrodes greatly decreases vibrational movement of these electrodes, resulting in the production of an electron discharge device with an improved microphonic characteristic.

Obviously, the mount electrodes, according to the present invention, may have different configurations. In addition, the lateral alignment of the nested grid electrode wires is not intended to be restricted to the manner of aligning the grids as described in a beam type electron discharge device and shown by Fig. 4 of the accompanying drawing. It is obvious that a lateral grid wire alignment may be desirable wherein the lateral Wires of a grid do not shade the lateral wires of the remaining grids from the cathode. In either event the utilization of the spacer 26 permits facile proper positioning of the grid laterals with respect to one and other.

While I have indicated a single embodiment of my invention, it will be apparent to one skilled in the art that variations may be made in the described structure and process without departing from the scope of my invention as set forth in the appended claims.

. What I claim as new is:

1. In an electron discharge device including nested grids with the lateral wires of one grid aligned with the lateral wires of another grid, and an anode, each of said grids and anode having elongated support elements thereon, the combination comprising a first insulating spacer receiving and positioning the one ends of said support elements, a second insulating spacer within the confines of the anode receiving and positioning the opposite ends of the grid support elements, and a third insulating spacer receiving and positioning the opposite ends of both the anode support elements and at least one of the support elements for each grid.

2. In an electron discharge device including nested grids with the lateral wires of one grid aligned with the lateral wires of another grid, beam confining plates, and an anode, each having elongated support elements thereon, the combination comprising a first insulating spacer receiving and positioning the one ends of said support elements, a second insulating spacer within the confines of the anode receiving and positioning the opposite ends of the grid and beam confining plate support elements, and a third insulating spacer receiving and positioning the opposite ends of all of said support elements.

3. In the process of assemblying an electrode mount for an electron discharge device, the steps of mounting the one ends of elongated support elements forming part of nested grids on a first insulating spacer, mounting a second insulating spacer on the opposite ends of the support elements of the grids, laterally aligning the lateral wires of the grids with respect to each other, mounting the one end of elongated support elements forming part of an anode on said first spacer, and subsequently mounting a third insulating spacer on the opposite ends of the support elements of said anode and on the opposite end of at least one support element of each grid.

4. In the process of assemblying an electrode mount for an electron discharge device, the steps of mounting the one ends of elongated support elements forming part of nested grids and beam confining plates on a first insulating spacer, mounting a second insulating spacer on the opposite ends of the support elements of the grids and beam confining plates, laterally aligning the lateral wires of the grids with respect to each other, mounting one end of elongated support elements forming part of References Cited in the file of this patent UNITED STATES PATENTS 2,042,057 Hopping May 26, 1936 6 Schade Feb. 8, 1938 Parker Dec. 12, 1939 Peterson Oct. 8, 1940 Ronci June 1, 1948

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