US2916648A - Electron tube - Google Patents

Description

Dec. 8, 1959 K. M. STOLL 2,916,648

ELECTRON TUBE Filed Dec. 5, 1957 U K 4? Fig.2

INVENTOR KENNETH M. STOLL Mam) ATTORNEY United States Pa 4 Claims. (or. 313-. -178) This invention relates to electron tubes and more particularly to high voltage tubes of the type employing electron shields.

Generally, high voltage tubes such as diode rectifiers which are used in television circuits require the application of electron shields to protect the envelope from electron bombardment during the non-conducting portion of the tube operative cycle. When the anode potential becomes negative, the electrons emitted from the cathode tend to bombard the tube envelope, thereby causing suflicient gas to be generated within the tube to make it inoperable. When the electrons involved in the bombardment become focused due to the tube electrode potentials and configurations, the envelope may become punctured.

In high voltage tubes of the type described above, the stem area of the envelope is very often that portion which is subjected to electron bombardment. Accordingly, a shield is generally positioned intermediate the cathode and stem. In addition, it has been found necessary to mount the getter or clean-up agent between the shield and the stern due to space'requirements and so that the vaporized getter material would not interfere with any of the tube electrical characteristics. Due to this array of electrodes, the tube has a longer overall length than is desirable for many applications, it is relatively expensive to fabricate, and the position of the getter near the stem makes it difiicult to heat the getter sufiiciently to provide vaporization of the getter material.

Accordingly, it is an object of the invention to reduce the aforementioned disadvantages and to fabricate a more compact, less expensive electron tube.

A further object is to position a getter in an electron tube at a location which will facilitate elfective vaporization of the getter material.

The foregoing objects are achieved in one aspect of the invention by the provision of an electron tube employing an envelope having a stern portion formed to receive stem leads, an anode, and a cathode disposed within the envelope relative to the anode and spaced from the stem. An electron shield is positioned intermediate the cathode and stem and formed with getter material chambers which are directed toward the stem. The getter material, when vaporized, produces a pattern on the stem which substantially lies within the boundary defined by the stern lead positions.

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

Fig. 1 shows a plan view of a stem portion of an electron discharge device;

Fig. 2 is a partially sectioned plan view of an electron discharge device; and

Fig. 3 is a section taken along line 3--3 of Fig. 2.

Referring to the drawings, a high voltage type rectifier tube is shown comprising a glass envelope 11 formed with a wafer type glass stem 13 hermetically sealed to bulb 15. A base 16 having connector pins 18 afiixed thereto is positioned upon the lower portion of the envelope. An

anode 17 is mounted envelope 11 by means of the seal between anode top cap 19 and the dome of bulb 15. The anode iscup-shaped, with the opening 21 provided therein directed toward stem 13. Positioned within. the anode is a cathode 23, which may be of .the indirectly or directly heated type as shown. The cathode is supported relative to the anode by means of connector rods 25, which are welded or otherwise attached to stem leads 27. An electrostatic shield 24 is afiixed to the shorter support rod 25 to minimize the electrostatic forces exerted on the cathode during tube operation. 1

Positioned upon leads 27 beneath the opening 21 in anode 17 is a metallic shield 29'having an aperture 31 formed therein to allow passage of rods 25 therethrough. If desired, a strip of mica (not shown) having holes formed to cooperate with the rods may be mounted upon the shield. over aperture 31 to aid in the support and posi tioning of rods 25. Spaced intermediate the outside edge of shield 29 and aperture 31 are a plurality of chambers 33 formed'to hold getter material. The chambers are provided on the bottom of the shield with openings or tabs 35 which direct the passage of vaporized getter material toward stem 13.

Referring particularly to Figs. 1 and 3, it can be seen that stem 13 is formed with internal spaced upstanding glass beads 37 located near the peripheral portions of the stern. Leads 27 emerge from the upper portion of the glass beads to provide a longer electrical leakage path between the spaced leads by virtue of the longer surface distance between these leads. The lower surface of stem 13 has lead supporting nubbins 28 and exhaust tubulation 30, which, after tip-off, is housed within lug 32. The ends of leads 27 are soldered or otherwise connected to pins 18.

Shield 29 has a diameter suflicient to substantially cover opening 21 to prevent electron bombardment of stem 13 during the non-conductive portion of the tube operative cycle while getter chambers 33 are arranged to lie within the circle defined by beads 37. The exact positioning of chambers 33 are dependent upon the distance of shield 29 from wafer 13 since the pattern of vaporized getter material on the stem should preferably be substantially confined within an area excluding the upper portions of the beads 37 from which electrical leads 27 emerge. Since the getter material is generally an alloy of active metals such as barium, magnesium, or aluminum, a conductive getter material coating of any appreciable thickness connecting the heater leads may produce a short circuit or sufficient leakage to reduce the prescribed heater power.

An electron tube constructed in accordance with the above described invention may be economically and efliciently fabricated and the overall length of the tubes may be reduced. In addition, the utilization of a combination getter and shield provides the shielding needed and allows positioning of the getter to facilitate easy access by an external heating device such as a radio frequency coil which is used to flash or vaporize the getter material.

Although one embodiment of the invention has been shown and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. An electron discharge device comprising an evacuated, hermetically sealed envelope having a stem, an anode, a cathode spaced from the anode, and an electron shield positioned intermediate said cathode and said stem formed with getter material chambers having vaporizable getter material disposed therein, said chambers being formed to direct said getter material toward said stem.

2. An electron discharge device comprising an evacuated, hermetically sealed envelope having a stem, a cupshaped anode having the opening therein directed toward said stem, a cathode positioned within said anode, and an electron shield positioned intermediate said anode opening and said stem formed with getter material chambers having vaporizable getter material disposed therein, said chambers being formed to direct said getter material t0- ward said stem. 1

3. An electron discharge device comprising an evacuated, hermetically sealed envelope having a stern formed with internal upstanding spaced insulating beads arrayed about the periphery thereof, a plurality of stem leads emerging from the upper portions of said beads, an anode disposed within said envelope spaced from said stern, a cathode mounted upon said leads relative to the anode, an electron shield having getter material chambers, and vaporizable getter material disposed within said chambers for direction toward said stem, said shield being positioned intermediate said cathode and said stem and spaced from said stem a prescribed distance to provide a vaporized getter material pattern substantially located within the peripheral array of said beads.

4. An electron discharge device comprising an evacuated, hermetically sealed envelope having a stem formed 4 I with internal upstanding spaced insulating beads arrayed about the periphery thereof, a plurality of stem leads emerging from the upper portions of said heads, a cupshaped anode spaced from the stem having the opening therein directed toward said stem, a cathode mounted upon said leads within the anode, an electron shield having getter material chambers, and vapon'zable getter material disposed within said chambers for direction toward said stem, said shield beingpositioned intermediate said cathode and stem and spaced from said stem a prescribed distance to provide a vaporized getter material pattern substantially locatedtwithin the peripheral array of said beads.

References Cited in the file of this patent UNITED STATES PATENTS

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