US2501308A - Vapor electric device - Google Patents

Description

March 21, 1950 J, BOYER 2,501,308

VAPOR ELECTRIC DEVICE Filed May '7, 1949 lNVENTOR John L.Boyer.

ATTORN EY WITNESSES:

Patented Mar. 21, 1950 vAroR ELECTRIC DEVICE John L. Boyer, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania I Application May 7, 1949, Serial No. 92,057

My invention relates to a vapor electric device and particularly to a construction of a vapor electric device for reducing the tendency to arcback.

It has been found that the most important cause of the arc-back in gaseous rectifier tubesutilization of anodes and shields that there is a concentration or focusing of positive ion bombardment at the surface of the anode at the focal point of the passages through the shield openings. It has also been demonstrated that the performance of a vapor electric device is improved if the number of positive ions arriving in a given time or a given area on the anode surface is reduced, or if the voltage gradient at the critical spots on the anode is reduced.

I propose to reduce the density of positive ion bombardment by drilling small holes in the anode surface substantially coaxial with the openings in the anode shield. This not only greatly reduces the ion density under the focus point of the grid openings but in addition the electric field inside the anode hole is practically zero, and any electrical discharges across any insulating patches are so well shielded and deionized that a stable cathode spot cannot be formed involving the external power circuit.

A further method of improving the arc-back performance of a vapor electric device is to reduce the number of positive ions focused on a single unit of cathode area. I propose to do this by providing a large number of relatively small passages in the anode shield, and these passages being as small in area as is consistent with a large total grid hole area for each square inch of grid surface and by spacing the grid as close as possible to the surface of the anode; It is particularly desirable to use strong material with small holes and thin sections between the holes. Preferably,-the length of the openings is considerably greater than the diameter of the opening so it is possible to form a positive ion sheath of sufficient thickness to substantially close the holes; even at rather high ion densities.

It is accordingly an object of my invention to '3 Claims. (01. 250-275) provide a vapor electric device having a low incident of arc-back.

It is a further object of my invention to provide an anode grid structure producing relatively low ion density bombardment per unit area of the anode surface.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing, in which the figure is a sectional elevation of a vapor electric device embodying my invention.

The exemplary embodiment of my invention comprises a metallic container I which may be evacuated by means of a passage 2 normally connected to a vapor vacuum pump (not shown). A pool 3 of vaporizable cathode material, such as mercury, gallium, caesium, potassium, etc., is placed in the bottom of the container I and 00-- operating with this cathode pool 3 is an anode 4 of solid material, either metal, or if mercury is the cathode material, preferably graphite. The anode 4 is supported in spaced insulated relation by means of an anode stem 5 attached to an insulating bushing'G rigidly clamped in vacuum tight relation to the top header I of the container I. A suitable cathode spot initiating device, herein shown as a make-alive type or so-called ignitron electrode 8, is placed in conjunction with the cathode pool 3, and usually a cathode shield 9 is spaced directly over the point of incident of the cathode spoti The anode 4 is surrounded by an anode shield I 0 closely spaced from the anode surface and constructed either of metal or of such materials as graphite and has a large number of relatively small passages II with relatively thin walls I2 of separating material between the passages l I so that a large portion of the shield area is cut away to provide the maximum ratio of passage area to shield area. The passages II produce a concentration of ion bombardment from the space between the anode 4 and cathode 3 to the anode surface. A small opening I5 is drilled in the anode surface directly under each shield passage I I, preferably coaxial with the shield passage I I so that the focal point of the positive ions passing through the openings II fall within the hole I5 drilled in the anode surface. The utilization of the holes I5 inthe-ahode surface has two apparent effects. First, it increases the area subject to bombardment so that the density of ion bombardment per unit area is decreased, and the point of bombardment is then put in a field of zero stren th so that there is much less chance only and that changes and modifications may be.

made therein without departing from the true pended claims.

I claim as my invention: 1. In a vapor electric device, an anode assembly spirit of my invention or the scope of the apcomprising a graphite anode, a shield of conducting material substantially enclosing said anode,

said shield being of material thickness, a pin-- rality of passages in shield opposite the end and sides of said anode, said "passages being of less diameter than the thickness of said shield, and depressions in the anode surface coaxial with said passages.

2. In a vapor electric device having a vaporizable cathode, a solid anode, an anode shield substantially enclosing said anode, a plurality of arc passages in said shield and depressions in said anode in positions corresponding to the focal points of said are passages.

3. A stable arc discharge device comprising a vapor evolving cathode, a solid anode spaced from said cathode, a shield of conducting material ,about said anode, a plurality of substantially tubular passages in said shield, and means for 1 increasing the surface area of the anode at a point corresponding to the axis of said passages. JOHN L. BOYER.

REFERENCES CETED The following references are of record in the file of this patent:

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