US3246195A

US3246195A - High-frequency electron tubes

Info

Publication number: US3246195A
Application number: US267015A
Authority: US
Inventors: Hoshino Fumio; Murata Yoshio
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1962-04-17
Filing date: 1963-03-21
Publication date: 1966-04-12
Anticipated expiration: 1983-04-12

Description

April 1966 FUMlO HOSHINO ETAL 3,246,195

HIGH-FREQUENCY ELECTRON TUBES Filed March 21, 1963 2 Sheets-Sheet 1 Fig.l

Fig. 3

INVENToRS Fumm Ho5H No YOSHIO mURHTH April 1966 FUMIO HOSHINO ETAL 3,246,195

HIGH-FREQUENCY ELECTRON TUBES Filed March 21, 1963 2 Sheets-Sheet 2 Fig. 2

INvENToRS Fumlo HOSHINO Yosmo muRnTH HTTaRNEY United States Patent 3,246,195 HIGH-FREQUENCY ELECTRON TUBES Fumio Hoshino and Yoshio Murata, Mohara-shi, Chiba, Japan, assignors to Hitachi, Ltd., Tokyo, Japan, a corporation of Japan Filed Mar. 21, 1963, Ser. No. 267,015 Claims priority, application Japan, Apr. 17, 1962, 37/ 18,727 Claims. (Cl. 313-240) The present invention relates to high-frequency electron tubes for use in grounded grid circuits.

In the 'past, miniature type receiving tubes have involved a deficiency that, in high-frequency operation, as the frequency increases the gain of such tubes is gradually reduced, therefore the tube operation becomes unstable and finally the tube itself becomes incapable of functioning as an amplifier. The reduction in gain in high-frequency operation is largely attributable to the following factors: (1) the increase in input and output conductances due to the self-inductance of lead-in wires for the electrodes; (2) the increase in ohmic loss in the leads due to the skin effect; and (3) the increase in high-frequency dielectric loss in the stem insulation. Also, the unstable operation is caused by the fact that the inductance of the grid lead makes the grounding of the grid incomplete and that the input and output circuits are coupled through the interelectrode capacitance so that part of the output is fed back to the input.

Previously, for the purpose of overcoming these diffi culties, various ways have been developed, for example, inner leads of minimized lengths or multiple leads have been used to reduce the self-inductance of the leads. Also, a shield element has been inserted between a cathode and an anode to reduce the interelectrode capacitance therebetween for the purpose of minimizing the capacity coupling between input and output. With miniature type receiving tubes, however, such measures as using shortened inner leads and increasing leads in number are subject to structural limitations and are naturally limited in their effect to reduce the inductance. A shield such as used in a conventional miniature tube is in fact effective only to shield the cathode and anode but does not shield the connectors and inner leads connected to such electrodes. Hence, the shielding effect between the input and the output have necessarily been incomplete.

Another way to avoid the above difficulties is the use of disc seal type tubes. This type of tube construction, however, involves a complicated manufacturing process not suitable for mass production and is very expensive beyond comparison with the miniature type tube construction.

The present invention has for its object to provide a high-frequency electron tube which is devoid of the above indicated deficiencies met with conventional miniature type receiving tubes and which is easy to fabricate just like the latter.

Another object of the invention is to provide a highfrequency electron tube of the character described which is easy to assemble and is rigid in structure.

According to the present invention, a high-frequency electron tube comprises a ceramic wafer, a grid lead plate extending through said ceramic Wafer centrally thereof and secured thereto, such as by brazing, and a shield plate secured to and electrically connected with said grid lead plate to shield between the cathode and cathode lead of the tube on the one hand and the anode and anode lead thereof on the other.

These and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, which illustrates one embodiment of the invention and in which:

FIG. 1 is a perspective view, partly cut away, of the inner structure of an electron tu-be embodying the invention;

FIG. 2 is an exploded view illustrating several components of the inner structure; and

FIG. 3 an exterior View, partly cut away, of the miniature type electron tube according to the present invention.

Referring to the drawings, particularly to FIGS. 1 and 2, reference numeral 1 designates a ceramic wafer having a slit centrally thereof and properly spaced-apart circular apertures '3, 4, 5 and 6. These

apertures

3, 5, and 6 are disposed on one side of the slit 2 and the aperture 4 is disposed on opposite sides of the slit 2, as clearly seen at the bottom portion of FIG. 2. A grid lead plate 7 is fitted through the slit 2 formed in the wafer 1 and secured thereto in the conventional manner, such as, by brazing. Cathode pin 8, anode pin 9 and

heater pins

10, 11 are fitted through

apertures

3, 4, 5 and 6 respectively and secured in place as by brazing to form a stem structure. Numeral 12 designates a shield plate; 13 a frame grid; 14 a cathode; 15 an anode; 16 grid wires, and 20 a heater.

Numerals

17, 17 designate respective mica sheets arranged opposite to each other and formed with elongated slots a, b and c for the purpose of supporting the electrodes, as shown in FIG. 2.

In assembling, the cathode 14, frame grid 13 and anode 15 are fitted for their support in the slots in the mica sheets 17, 17', which in turn are inserted into slits d formed in the shield plate 12. The frame grid 13 has on each side thereof spaced

lugs

18 and 19, which are welded to the shield plate so that the frame grid is firmly held in place.

The shield plate 12 is thereafter welded to the grid lead plate 7 and finally the cathode 14, anode 15 and heater 20 are connected to the

pins

8, 9, 10 and 11 by way of connectors to complete the mount assembly.

According to the present invention, the grid lead plate 7, which is obviously planar in contrast to the wire form conventionally used, is effective not only to minimize the self-inductance thereby ensuring that the grid is perfectly earthed but also markedly to reduce the high-frequency ohmic loss occurring in the leads due to the skin effect.

Further, the grid lead plate 7, frame grid 13 and shield plate 12 are connected to each other to form an electrically integral assembly which is highly effective to shield the cathode and the anode from each other while at the same time perfectly shielding the cathode and anode leads from each other. Consequently, the formation of any capacity coupling between the input and the output is effectively prevented, thus the operation of the electron tube is kept stable at high frequencies.

The ceramic wafer, having a characteristically small dielectric loss at high frequencies, has further advantageous features that it allows relatively thick leads to be fitted therewith and brazed thereto unlike conventional glass stems and that it can be hermetically sealed to glass as long as it has a coefiicient of expansion equal to that of the ceramic. This makes it possible to seal the wafer to a miniature bulb 22 of the conventional type to complete an electron tube as shown in FIG. 3.

It will be appreciated from the foregoing that the electron tube according to the present invention is not only free from the difiiculties met with conventional miniature type electron tubes but also easy to assemble and rigid in structure since all the electrodes are supported by a shield plate or by two mica sheets supported opposite each other by a shield plate, which in turn is supported by a grid lead plate.

Although one preferred embodiment has been described and shown herein, it is apparent to those skilled in the 3 art that many changes and modifications may be made" therein without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. A high-frequencyelectron tube'comprising a ceramic wafer, 21 grid lead plate sealed through. said wafer, a cathode pin and an anode pin sealed through said wafer respectively and shielded from each other by said grid lead plate, a cathode connected with said cathode pin by a cathode conductor, an anode connected with said anode pin by an anode conductor, and grid electrode means consisting of a frame grid secured to said grid lead plate and interposed between said cathode and said anode operable to shield said cathode and said cathode conductor and said anode and said anode conductor from each other. I I g 2. An electron tube comprising an insulator wafer, a cathode pin andan anode pin respectively sealed through said wafer, a grid lead plate sealed through said wafer and separating said cathode pin and said anode pin from each other, a cathode, an anode, connecting means connecting said cathode and anode with said cathode pin and said anode pin respectively, and a frame grid seured to said grid lead plate, interposed between said cathode and cathode connecting means and said anode and anode connecting means. I e g g 3. A high frequency electron tube comprising a ceramic wafer,

a cathode pin and an anode pin sealed through said wafer respectively,

a grid lead plate interposed between said cathode pin and said anode pin and sealed through said wafer,

a frame grid means secured to said grid lead plate and extending longitudinally of the tube,

and a cathode and an anode connected with said cathode pin and said anode pin respectively and provided on opposite sides of said frame grid means and mutually shielded therebetween by said frame grid means. 4. A high frequency electron tube according to claim 3 in which said frame grid means is composed of a frame grid and a shield plate having an opening therein for electron beam passing, operatively connecting said frame grid with said grid lead plate and supporting said cathode and said anode thereon in mutually insulated relationship. I

5. An electron tube comprising an insulator wafer, a cathode pin and an anode pin sealed through said wafer respectively, a cathode connected with said cathode pin by a cathode conductor, an anode connected with said anode pin by an anode conductor, a frame grid composed of a wire grid and a frame and a grid lead plate sealed through said wafer and supporting said frame grid thereon, said frame grid and said grid lead plate interposed between said cathode, said cathode conductor and said cathode pin onone hand and said anode, said anode conductor and said anode pin on the other in mutually shielded 1/1945 Bondley 3l3-249 3/1958 Dailey 313-249 J OHN W. HUCKERT, Primary Examiner.

DAVID J. GALVIN, Examiner.

Claims

2. AN ELECTRON TUBE COMPRISING AN INSULATOR WAFER, A CATHODE PIN AND AN ANODE PIN RESPECTIVELY SEALED THROUGH SAID WAFER, A GRID LEAD PLATE SEALED THROUGH SAID WAFER AND SEPARATING SAID CATHODE PIN AND SAID ANODE PIN FROM EACH OTHER, A CATHODE, AN ANODE, CONNECTING MEANS CONNECTING SAID CATHODE AND ANODE WITH SAID CATHODE PIN AND SAID ANODE PIN RESPECTIVELY, AND A FRAME GRID SECURED TO SAID GRID LEAD PLATE, INTERPOSED BETWEEN SAID CATHODE AND CATHODE CONNECTING MEANS AND SAID ANODE AND ANODE CONNECTING MEANS.