US1747050A - Electric ionization device - Google Patents

Description

1930. E. E. CHARLTON ELECTRIC IONIZATION DEVICE Filed Jan. 28, 1926 Inventor: Ernest ECharlton,

b H His Attorney.

Patented Feb. 11, 1930 UNITED STATES PATENT OFFICE miter I. CHARLTON, OI SCHENECTADY, NEW YORK, ASSIGNOB '10 GENERAL ELECTRIC COMPANY, A. CORPORATION 01' NEW YORK ELECTRIC IONIZATION DEVICE Application filed January 28, 1926. Serial 170. 84,468.

The present invention relates to the construction of gas ionization devices havin unheated electrodes, in articular to rectlfiers having electrodes of issimilar area, and it 5 is the object of my invention to improve the efficiency of operation of these devices.

In gas-filled glow tubes having electrodes of unequal size or area, the conductivity in opposite directions at a given voltage is materially different and therefore these devices are used for the rectification of alternating current. There is, however, some leakage current during the alternate half waves of reverse polarity, or in other words the rectification is not complete.

It is the object of my invention to reduce the inverse or leakage current in rectifiers of the glow discharge type, which for convenience will be referred to herein as selfsustaining discharge devices.-

In accordance with my invention the positive ionization of the gaseous fillin of these devices is reduced during reverse 'scharges by limiting the travel of the electrons to a path shorter than the normal distance, the electrode from which the inverse or leakage discharge emanates being surrounded by a shield which during the period of leakage current is positively charged and which pref- 3 erably forms a part of the cathode of the device. My invention also includes a means for reducing the starting voltage.

My invention may be better understood by reference to the accompanying drawing-taken in connection with the following description.

The drawing shows in Fig. 1 my improved device in perspective and in Fig. 2 in vertical section.

Referring to the drawing, the device illustrated comprises a bulb 1, consisting of glass, or the like, and containing a cylindrical electrode 2 consisting of nickel, iron or other suitable metal and being supported upon the stem 3 by the wires 4, 5, 6 and 7, the latter being connected to a conductor 8 passing through the stem to one of the exterior contact members 9, 10. Located within the electrode 2 is a rod-shaped electrode 11, which is connected to a wire 12 sealed into the stem 3, and is surrounded for the greater the alumina sleeve 14 to shield the glass sleeve 13 from electron and ion bombardment. Th s feature of my improved. device is claimed in my copending application Serial No. 84,465, filed January 28, 1926.

Closely surrounding the electrode 11 is a cylinder 15, consisting of nickel or the like, which is connected to the cylinder 2 by the Wires 5 and 6 and hence is at the same potential as the cylinder 2, and in fact with the cylinder 2 constitutes a single electrode. 05

A small spur or Wire 16 preferably is mounted upon the cylindrical cathode 2 and extends closely adjacent to but out of actual contact with the anode 11. This extension of the cathode assists in the starting of the discharge, ordinarily reducing the required starting potential about ten volts. V The bulb is charged with a suitable gas," preferably neon, helium or argon or a mixture of helium and argon, at a pressure of about 5 to 20 m. m. Before the gas filling is introduced into the bulb, the bulb itself and the metal parts, should be deprived of water vapor and other absorbing gases and after the bulb is sealed a gas-absorbing agent 8 preferably should be volatilized within the bulb. For example, as illustrated, a metal capsule 17 charged with a. gas-absorbing agentmay be supported at some convenient place Within a bulb. A charge of metallic calcium or magnesium may be placed Within the capsule and volatilized by heating the capsule with high frequency current. To reduce the starting potential for the operation of the device, it is desirable also to intro duce a small amount of alkalimetal, such as caesium, rubidium, or potassium within the bulb. This alkali metal may also be heating the capsule, a chemical reaction occurs resulting in the volatilization both of evolved from the capsule, for example, by

reduced tuna M4 and m or a. V of alkaline earth metal.

During the operation or the described (16'- vioe, a substantial ionization current is conducted through the gas when the cylindrical electrode 2 is negat ve, accomBanied by the well-known glow phenomena. uring the opposite half wave periods when the rod-shaped electrode 11 is negative, only a very small leakage current flows. Dur' the useful half cycle of current flow, the travel of the electrons when passing from the outer cylinder 2 to the rod 11 produces a larger amount of cumulative ionization in the gas than is produced durin the half cycle when the electrons travel om the rod 11 to the inner cylinder 15. During this period of leakage current when the electrode 11 is negative, the

field between the electrode 11 and t e inner cylinder 15 /is so strong that, the e ectrons starting from the electrode 11 are largely drawn to the inner cylinder 15 and hence roduce only a small amount of cumulative ionization. When the inner cylinder or shield 15 is absent, the leakage current is of the order of magnitude of about 15 to 20 per cent of the useful currentdepending onthe voltage, and other conditions. In the structure which constitutes my invention, this inder s said non-filamentary electrode.

4. A rectifier comprising a central-electrode leakage current has been reduced to about twenty-five per cent of its former value, namely to about five per cent of the useful current.

' What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A rectifier comprising a bulb, a charge of ionizable gas therein, and electrodes of materially diflerent size, the electrode of greater size comprising two concentric members spaced apart from each other, one of said members closely surrounding the electrode of lesser size and a spur connected to one of said electrodes and extending into close proximity to the other electrode.

2. A rectifier comprising a container, 9.

. charge of gas therein at a pressure of about rounding said first electrode, the latter electrode being constituted of two cylinders of materially unlike diameter, the smaller cylinder closely surrounding said first electrode, and a spur electrically connected to said cyland into also proximity to

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