US2039156A - Thermionic valve apparatus - Google Patents

Description

April 28, 1936., H A. EWEN THERMIONIC VALVE APPARATUS Filed July 5, 1933 INVENTOR HARRY ALEXANDER EWEN AQRNEY Patented Apr. 28, 1936 PATENT, OFFICE THERMIONIC VALVE APPARATUS Harry Alexander Ewen, Shenfield, England, assignor to Radio Corporation of America, a corporation of Delaware Application July 5, 1

933, Serial No. 679,052

In Great Britain July 8, 1932 2 Claims.

This invention relates to thermionic Valve apparatus and. more particularly to radio and similar transmitter installations employing thermionic valves of high power.

In order that radio transmitters and the like employing thermionic valves of high power may be operated efficiently, it is very desirable to provide means whereby the voltages applied to the filaments of the various valves may be adjusted fairly closely to particular values, it being common practice to require to be able to adjust filament voltage in steps of the order of one quarter of a volt per step. It is usual at the present time to provide for such adjustments by means of rheostats, but it will readily be appreciated that such rheostats are not easy or economical to design and manufacture when they are required to control the filaments of valves of high power where the filament current is of the order of 250 ampers or even more.

The present invention has for its object to meet this difiiculty, and according to the said invention filament heating for a high power valve in an installation of .the general character above described is obtained by means of an electrical generator machine, and the required filament voltage control is obtained by controlling the excitation of the generator. Accordingly in a high power multi-valve installation in accordance with this invention there will be provided a plurality of valves and a plurality of generators for energization of the filaments of said valves, there being a separate rheostat for the control of the field excitation of each generator. Preferably the field excitation for all the generators is obtained from a further generator machine, and preferably also a reversing switch is associated with the supply lines leading from the last mentioned generator to" the field systems of the filament heating generators so that by reversing the said reversing switch the polarity in the filament heating generators may be reversed and thus the polarity applied to the various filaments reversed. The object of this provision is to reduce filament wear, it being intended that the polarity of the filament supply potential shall be reversed at suitable intervals for the purpose of minimizing filament wear.

Preferably the generators are designed to have falling characteristics of suitable shape, so that in the event of short circuit or overload the output voltages therefrom will be reduced rapidly and automatically, thus obviating the necessity for providing fuses to guard against short circuits.

The invention is illustrated in the accompanying drawing which shows diagrammatically the invention as applied to a radio transmitter.

Referring to the drawing there is provided a pair of motor driven shunt wound generators ElEZ each of say volts 4 k. w. output, and either being adapted at will to be connected by means of a switch TS through a reversing switch RS to feed energy to a pair of bus-bars EBB to be hereinafter referred to as the excitation busbars. The shunt field ESFI or ESFZ of each exciter includes in its circuit a rheostat VCI or V02 for voltage control. The filament F of each valve V in the transmitter is heated by current supplied from the armature of a separate heating generator I-IG and these generators, may, for example, be each of 35 volts 8.5 k. w. output. All the heating generators are separately excited and each has a control rheostat GR connected in its field circuit. Vt are voltmeters. The field circuits and individual control rheostats for the heating generators are connected in parallel to theexcitation bus-bars EBB and preferably a further rheostat GCR is included in the common field excitation or bus-bar circuit so that by operation of this further rheostat the field excitation of all the heating generators may be controlled together, individual control being of course obtained by the individual rheostats CR in the separate field circuits. The heating generators are driven in any convenient way, for example, by electric motors, a practically convenient arrangement being to provide one electric motor for two heating generators as indicated. One of the two exciter units acts as a spare. Similarly if desired other spare generator and. motor units may be provided in association with change-over switches, whereby they may be connected in circuit for operation when desired.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

l. A radio transmitter comprising a plurality of high powered thermionic valves, separate cathode heating generators for each of said valves, separate rheostats connected in the field circuit of the respective generators for controlling the field excitation of each generator and a generator power supply source, comprising two generators for exciting the fields of each of said separate cathode heating generators, a reversing switch connected to the power supply of the field systems of the cathode heating generators and the power supply source, said reversing switch connected to each power supply generator so that the polarity of said cathode heating generators may be reversed.

2. A radio transmitter comprising a plurality of high-powered thermionic valves, a separate cathode heating generator for heating each of said separate valves, a rheostat connected in series with the field circuit of each separate cathode heating generator, a plurality of power supply generators for exciting the field circuit of each cathode heating generator, means for reversing the polarity applied to each separate cathode heating generator, said means comprising a reversing switch connecting the field circuit of the separate cathode heating generators and the power supply generator, and a separate rheostat for controlling the excitation of each separate power supply generator.

HARRY ALEXANDER EWEN.

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