JPS5856937B2 - Grid type electron tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a grid-type electron tube, and more particularly, to an electron tube in which the cathode, one or more grids, and the anode electrodes are cylindrical and arranged about a common or tube axis. Regarding.

In the manufacture of electron tubes of this type of construction, particularly those found in shortwave transmitting triodes, the electron emitting portion of the cathode consists of a group of spaced wires.

This configuration is applied to a squirrel cage cathode, which is made of a cylindrical roll of metal mesh and is attached to a support.

The above arrangement also applies in the case of pin-type cathodes, in which case the wires take the form of pins stretched between the ends of the tubular body.

Whatever the exact shape, these cathodes
It is always a light and highly truncated structure due to its linear structure, making it susceptible to mechanical vibrations that affect its stability.

The magnitude of the problem posed by such stability is easily understood by considering the following.

That is, in some electron tubes, these cathodes have a considerable diameter, that is, a cylinder diameter of 120 mm or more;
With a height of 300 mm and the highest electron-emitting material, the operating temperature can reach 1650°C.

The grid may be a single grid in the case of a triode, or a cylinder coaxial to and surrounding the cathode.

Furthermore, the first of the grids has a diameter only slightly larger than the diameter of the cathode for electronic reasons.

This grid, like the cathode, also has a highly truncated structure and a small thickness.

These are essential requirements for the grid to exhibit adequate transparency to the electron beam.

The same is true for other grids for similar reasons.

These grids therefore end up being light and highly truncated parts, which are extremely susceptible to the effects of mechanical vibrations.

Furthermore, the grid, like the cathode, can be made of metal or, as in more advanced embodiments of the electron tube to which the invention relates, of graphite.

Regardless of the material from which the grid is constructed, the grid still faces mechanical stability problems.

This problem is even more serious for the following reasons.

So the reason is that the cathode and the first
The distance between the tube and the grid is usually very small, and the vibrations affecting these parts generate considerable vibrations at said distance, which impair the proper operation of the tube.

Furthermore, it must be added that when the cathode is operated at the temperatures mentioned, the temperature of the first grid increases to as much as 1250 DEG C. during operation.

It is an object of the present invention to provide a cylindrical electron tube with improved stability against vibrations of the cathode and grid compared to conventional electron tubes of the same type.

In the electron tube according to the invention, the cathode is divided into two or more parts in the direction of the tube axis.

However, unlike the structure adopted in the prior art, these parts have different diameters.

Furthermore, the first grid, or a single grid in the case of a triode, is configured to differ in diameter at the level of the separation area (split) between the different parts of the cathode.

In a multi-grid electron tube, the other grids can also be shaped similarly to the first grid according to the invention.

Further, the anode may also have a similar shape.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a cathode and grid assembly of a conventional electron tube, an example of which is a triode.

Other electrodes of the tube are not shown to simplify the illustration.

The cathode surface 1 is constituted by a metal wire mesh wound into a cylindrical shape, and emits an electron beam during operation.

The wire group consists of thorium-coated tungsten, for example.

The cathode is completed by a base in the form of a disk 2 and a ring 3.

Both the base and the ring are made of metal and have the aforementioned cylindrical electrodes attached at both ends.

The base and the ring are supported by two sets of rods, for example three of each set; only two rods, referenced 4 and 5, are shown in the drawing.

These rods have plate-shaped supports 6, 7 at their lower ends.
are installed on each.

These plate-shaped parts are made of metal and serve to provide a connection to a heating current generator, not shown.

The grid with reference numeral 8 is a metal mesh 1 as shown in the figure.
The cathode grid spacing is typically on the order of 1 mm for this type of tube.

The cylindrical body, made of graphite, for example, terminates at one end at the bottom 9 and is buttoned, and flares at the lower end.

At its lower end, the cylinder is welded to a third dish-shaped part 11.

This dish-shaped part 11 consists of an electrical conductor, through which a grid bias voltage is applied.

12 indicates an insulating spacer.

FIG. 2 illustrates a cathode and grid assembly similar to that shown in FIG.

However, in this case an embodiment according to the invention is shown.

The cathode surface is shown constituted by a metal mesh wound to form a cylinder 1 .

However, whereas in the case of FIG. 1 an integral cathode was shown constituted by a mesh 2 and attached to a base 2 and a ring 3, in the example of FIG.
A cathode consisting of two parts is shown.

The upper part of the cathode is numbered 1 as in FIG.

Note that, as can be seen from the figure, the same reference numerals as in FIG. 1 are also given to the support and plate-shaped parts related to the first part.

Here, however, the support has been reduced to a set of three rods and a dish 6 for reasons explained later.

The second part, the lower part, has a larger diameter than the first part, as shown, and is constituted by a mesh 10 terminating at each end in rings 20, 30.

These rings are carried by two sets of rods 5, 50, three in each set, terminating in dish-like parts 7 and 70, respectively.

In the illustrated example, the two parts of the cathode are joined together by metal spacers placed along the rings 3, 20 to which they are attached, two of these spacers being shown in cross-section. It is designated by the reference numeral 40.

These spacers provide electrical contact between the two parts of the cathode, so that the heating of the cathode is
This is done via 0.

As mentioned above, the grid 8 has the shape of a cylindrical body that widens at one end and terminates at the bottom 9 at the other end.

However, whereas in the conventional example shown in FIG. 1 the cylinder had a constant diameter over its entire height, in the case of the cathode-grid assembly according to the embodiment of the present invention shown in FIG. The cylinder consists of two parts with different diameters, and these two parts have a non-cylindrical surface 13 at the split level between the two cathode parts.
In this example, they are joined by a truncated conical surface section.

This type of bonding structure reinforces the mechanical stability of the grid due to the rigidity it provides.

In addition, splitting the cathode into two sections with a lower height than a conventional monolithic structure increases the mechanical stability of the wire network in each section, other things being equal. I will let you do it.

In the embodiment described above, the cathode was divided into two parts, but
In other variations, the number of these sections may be two or more and the diameters of the divided sections may be different from each other within the scope of the invention.

In this case, the grid cylinder 8 may comprise several connecting surfaces, such as the aforementioned surfaces 13, for example at each split level between each division.

The invention is applicable not only to triodes that include a cathode and a grid in addition to the anode, but also to multi-grid electron tubes that include other additional grids.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional electron tube cathode-grid assembly, and FIG. 2 is a cross-sectional view of a cathode-grid assembly according to a non-limiting embodiment of the present invention. 1... cathode, 2... base, 3... ring,
4゜5...Rod, 6,7,11,70...Dish shaped part, 8...Grid.

Claims (1)

Claims: 1. An electron tube in which a cathode, one or more grids, and an anode cylindrical electrode are arranged around a common axis, the cathode comprising at least two separate parts of different diameters. at least a first of said grids, i.e. the one closest to said cathode, consists of cylindrical parts having a diameter that expands corresponding to the diameter of said cathode part, these cylindrical parts comprising: Electron tube, characterized in that the separate parts are connected together by non-cylindrical surfaces at the level of the split.