US1920649A - High amperage rectifier - Google Patents

Description

1933- E. A. LEDERER 1,920,649

HIGH AMPERAGE RECTIFIER Filed NOV. 15, 1924 FIGJ F g.2

IUIIIO'IIII'IOIOOI INVENTOR ERNEST A. LEDERER ATTORNEY Patented Aug. 1, 1933 HIGH AIMPEBAGE RECTIFIER Ernest Anton Lederer, East Orange, N. 1., as

signer to Westinghouse Lamp Company, a Corporation of Pennsylvania 4 Application November 13, 1924 Serial No. 749,594

2 Claim.

This invention relates to a rectifier for electrical currents and more particularly to a rectifier for converting alternating currents into direct currents in which the discharge takes place 5 in a rarefied gaseous atmosphere.

In a copending application entitled, Rectifier, Serial No. 728,988, filed July 29, 1924, and. assigned to the Westinghouse Lamp 00., Patent Number 1,856,257, May 3, 1932, I have disclosed a rectifier, designed for operation on the ordinary commercial lighting circuit of 110 or 220 volts, which is particularly suitable for supplying current for the plate circuit of the radio tubes of radio receiving apparatus.

Briefly, the rectifier set forth in said copending application, comprises an envelope having a filling of gas at a relatively low pressure, preferably a rare gas, as neon or helium or a mixture of rare gases, a plurality of electrodes which may, 0 for convenience, be termed ionizing electrodes arranged relatively close together and adapted to have alternating current impressed thereon to produce a low potential discharge therebetween to ionize the gaseous medium within the envelope, and one or more additional electrodes cooperating with the ionizing electrodes to rectify the alternating current impressed thereon.

The filling of rare gas reduces the starting and operating potential of the rectifier. The cathode drop and consequently the potential drop between the electrodes from which direct current is obtained, may be further reduced by coating the cathode with an alkali metal such as potassium, sodium, rubidium, caesium, lithium or alloys thereof, preferably vaporized onto the cathode after it is sealed into the envelope.

A rectifier constructed in accordance with the application above referred to, using potassium metal on the cathode and having a filling of neon 4 gas, may be operated on potentials of 220 volts and direct current obtained therefrom at approximately 150 volts with a current flow of from 0.5 to 120 milliamperes. The output voltage,

however, may be varied by varying the alkali metal used on the cathode or by varying the character of the gas used in the rectifier. The current capacity of the rectifier 'is limited by the temperature at which the cathode may be operated,- and this in turn is limited by the vaporization temperature of the alkali metal used on the cathode.

One of the objects of the present invention is to produce a rectifier 01' the type described above,

operable at relatively high'amperage and adapted to supply the filament current for the vacuum tubes of radio receiving apparatus.

Another object is to produce a rectifier of the discharge type embodying means for preventing undue heating of the cathode.

Another object is to provide a rectifier having a cooled cathode.

Another object is to produce a rectifier of the discharge type in which the cathode forms a portionof the wall of the envelope.

Another object is to produce a cathode for a rectifier of the discharge type having heat radiating, means associated therewith.

Other objects and advantages will hereinafter appear.

In accordance with one embodiment of this.in--

vention, the cathode is made of relatively large area, in order to provide a large heat radiating surface and preferably is in the form of a metal cap or sleeve closed at one end and united at 7 the opposite end to the glass portion of the envelope so as to constitute a portion of the wall of the envelope.

It is desirable that the cap be composed of a metal having a high heat conductivity such as copper. Cooling means may also be provided which may take the form of heat radiating fins projecting from the exterior surface of the cathode. If desired, the cathode may be of corrugated construction to provide a large heat radiating surface or a water jacket or other suitable means may be provided for maintaining the temperature of the cathode relatively low.

In order that the invention may be more fully understood, reference is had to the accompanying drawing in which,

Fig. 1 is a sectional view of one form of rectifier embodying the invention;

Fig. 2 is a sectional view of ,a modified form of rectifier; and,

Fig. 3 is a sectional view of a still further modified form of rectifier, this view also showing diagrammatically, an arrangement for obtaining substantially uniform direct current from analternating current source.

The rectifier shown in Fig. 1 comprises 5. glow discharge device including an envelope 1 having a filling of rare gas such as'neon or helium or a mixture of rare gases, a pair of electrodes 2 and 3 'between which an alternating current discharge is adapted to take place and a cathode 4 cooperatdng with electrodes 2 and 3 to produce a direct current discharge. The electrodes 2 and 3 are of small area compared with the cathode 4 and are arranged relatively close together. The elecno r trodes 2 and 3 are connected to or form continuations of the leading-in wires 5 and 6, respectively, which are sealed through the stem '7 of the device. Preferably, they are composed of a non-sputtering metal such as tungsten, iron, aluminum, etc.

The cathode 4 is in the form of 'a metallic cup unitedto the glass portion 8 of the envelope in a gas tight manner as is well known in the art and preferably is composed of a metal having a high heat conductivity such as copper although iron or any other suitable metal may be employed. A plurality of heat radiating fins 9 are provided on the exterior surface of the cathode preferably integral therewith. A suitable terminal is pro-- vided'for the cathode which may be in the form of a cap screw 10 as shown in the drawing.

An alkali metal, as potassium or sodium, may be distilled into the tube and deposited upon the cathode after it is sealed to the glass portion of the envelope in the manner fully set forth in the Lederer Patent No. 1,461,360, July 10, 1923, entitled, Electric gas lamp, and assigned to the Westinghouse Lamp Company. The alkali metals serve to lower the cathode drop and permit a relatively low potential discharge to take place between the electrode 4 and the electrodes 2 and 3.

A base 11 of any suitable form is secured to the envelope and is provided with a pair of terminal contact plugs 12 and 13 to which the leading-in wires 5 and 6 are connected, respectively. The alternating current is impressed upon the electrodes 2 and 3 in a manner which will hereinafter appear and a discharge obtained therebetween which serves to ionize the gas within the envelope and thus still further reduce the potential required to cause the main discharge to take place between these electrodes and the cathode 4.

The discharge takes place in one direction only, the electrode 4 serving as a cathode alternately for the electrodes 2 and 3. The electrode 4, because of its large surface and because of the coating of potassium metal, has a relatively small cathode drop as compared to the electrodes 2 and 3. It would, therefore, require a much higher voltage to produce a discharge between the electrode 4 and either the electrodes 2 and 3 when they are negative, than when they are positive. By suitably proportioning the size and shape of these electrodes and the gas pressure within the device,-the discharge in one direction may be entirely suppressed and a point to plate discharge reproduced alternately between the electrodes 2 and 4 and electrodes 3 and 4. It will thus be noted that full wave rectification is obtained and a continuous direct current produced.

Rectifiers made in accordance with this inventioncontaining a gas pressure of from to 15 mm. having the anodes spaced apart from ,4; to /2 inch and the minimum distance from the anode to cathode not over /2 inch, have been found to operate satisfactorily.

In Fig. 2 a modified form of a rectifier is shown in which the cathode 14 is formed of relatively thin corrugated metal whereby a large heat radiating surface is obtained. In order to prevent the atmospheric pressure from collapsing the corrugated cathode, a glass rod 15 is fused to the stem 7 and has its outer end 16 enlarged slightly and terminating adjacent the outer end of the cathode. In this modification, a standard screw threaded base 1'7 is employed.

In Fig. 3 a still further embodiment of the invention is shown in which the cathode is provided with means for permitting a. cooling fluid to be circulated therethrough. For this purpose. a cathode 18 is provided with a jacket or outer wall 19 which may be formed integrally with the cathode or separately therefrom and secured thereto in any suitable manner. The outer casing or jacket 19 is spaced from the inner wall of the cathode to form an annular chamber 20 through which water or other cooling fluid may be circulated by means of the conduits 21 and 22. The portion 23 of the envelope in this modification, is composed of porcelain and has the inner end 24 coated with silver or other metal, as

shown at 25, whereby it may be readily soldered to the cathode 18. The outer end of the porcelain container 23 is provided with a pair of hollow conical legs 26 and 27 through which the anodes 28 and 29 extend. Each of the anodes is formed with a conical portion 30 ground or fitted to the hollow legs 26 and 2'? and retained therein in a gas tight manner by means of a clamping nut 31. The outer end of the electrodes are threaded at 32 to form terminals therefor.

The arrangement for supplying direct current for a desired purpose as, for instance, supplying current to the filament of radio tubes or similar apparatus, charging storage batteries, etc., is shown in Fig. 3 in which an alternating current source 33, for instance, the ordinary commercial lighting circuit of 110 volts, is stepped up by a transformer 34. The opposite ends of the secondary winding 35 of the transformer are connected to the electrodes 28 and 29 of the rectifier through the terminals 32.

Direct current is obtained between the cathode 18 of the rectifier and the central portion 36 of the transformer 34 and the irregularities in such current are smoothed out in any desired manner, as by shunting a number of condensers 37 across the lines 38 and 39 and introducing suitable induction coils 40 in series in the lines. The voltage between the lines 38 and 39 may be controlled by a suitable rheostat 41.

Sliding contacts 42 and 43 or other desired resistance varying means may be associated with the resistance 41 and by suitably regulating the resistance, current of diiferent voltages may be obtained between the terminals 42 and 44 and the terminals 43 and 44. For instance, current for heating the filament of the radio tubes of a radio receiving set, may be obtained between the terminals 42 and 44 and the current for the plate circuit obtained between the terminals 43 and 44. In sets utilizing tubes of different sizes or operating at different filament voltages, one set of terminals may supply the current for one type of tube and the other terminals may supply the current for the other type of tube.

It will be noted that a rectifier has been produced in which the cathode is maintained at a relatively low temperature, thus permitting the rectifier to operate at relatively high currents without danger of vaporizing the alkali metal from a surface of the cathode. I have found that with a cooled cathode of this type and anodes having relatively large leading-in conductors whereby they maybe maintained at a temperature sufliciently low to prevent cracking of the glass parts, that currents of 10 or more amperes may be obtained with this rectifier.

While several embodiments of the invention have been shown and described, it is to be understood that the invention is not limited to the form shown, but many variations may be made therein without departing from the invention.

What is claimed is: r 1. An electrical discharge device comprisingan envelope, a gaseous filling, at least one anode and v a cathode adapted to iunctlon non-thermionlcally, said cathode being-corrugated and surfaced at least in part with alkali metal.

2. A-glow discharge device comprising an en- ERNEST ANTON LEDERER.

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