US1601075A - System of space-discharge devices - Google Patents

Description

Sept. 28, 1926.

A. W. KISHPAUGH SYSTEM OF SPACE DISCHARGE DEVICE Filed April 10 1924 atented Sept. 28, 1926.

NITED sr ARTHUR W. KISHPAUGH, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED,

NEW YORK.

OF NEW YORK, N. Y., A CORPORATION OF SYSTEM OF SPACE-DISCHARGE DEVICES.

Application filed April 10, 1924. Serial No. 105,456.

This invention relates to systems of space discharge devices and more particularly to method of and means for sequentially controlling the supply of energy from a common power unit to the electrodes of three electrode space discharge devices.

According to present practice in carrier transmitting systems, high frequency oscillations are produced, controlled or modified in accordance with signals or impulses to be sent, and transmitted to a distant station. Systems of this type now generally used include, as amplifiers, modulators and oscillators, three electrode space discharge devices.

The ordinary three element space dis charge device having a cathode, an anode and an impedance control electrode requires a source of heating current for the cathode and a source of space current. If the full working voltage of the space current source be applied to the electrodes of the device before the cathode is heated and if the magnitude of the space current is large it may result in damage to or destruction of the discharge device.

It has been heretofore proposed to provide means, whereby such devices may be safeguarded against high space voltages and excessive space current, by applying heating current to the cathodes of the devices included in the apparatus and delaying the application of the operating voltage to'space path electrodes of the devices until after their cathodes have been heated to substantially operating temperature.

In such apparatus the full operating voltage of the space current source. is applied to the space paths of the device at t e instant the relay control device completes the circuit of the source.

One disadvantage of this method of operation resides in the fact that, for high quality transmission, the circuits associated with the devices include reactances of different characteristics having appreciable values, with the result that there occurs in these circuits surges which may damage, or even destroy, the discharge devices.

The present invention provides an arrangement, whereby the energy is applied to the electrodes of the discharge devices in proper sequence and. its application is controlled to prevent the production of surges 1n the circuits of the system.

In accordance with this invention current is supplied by a low voltage generator to heat the cathodes of the devices and space current is supplied by a relatively high voltage generator. These generators are s multaneously driven by a motor. A time limit relay energized from the cathode heatmg circuit serves to delay, until the cathodes havehad time to become fully heated, the application of energizing current to the field winding and completion of the armature circuit of the'high voltage generator. 7

A primary object of this invention is to control the application of energizing current to a space discharge device so that sur es do not occur in the circuits associated W1th the device.

Another object is to control the application of energizing current to a discharge deyice, so that current is initially supplied to its space path at low voltage and gradually increased to normal value after the path is rendered conductive.

A further object is to control the application of energizing current from a common supply unit to a space discharge system without injury to the discharge devices of the system.

The invention itself, both as to its organization and method of operation will best be understood by reference to the following description taken in connection with the accompanying drawing in which the single figure shows diagrammatically a circuit arrangement which may be employed in carry- 90 in the invention into effect.

he figure illustrates a radio telephone transmitting system in which speech currents supplied by the circuit 1, which may be a telephone line, are transmitted by the transformer 2 to the amplifier 3.

Amplified speech currents are supplied to the input circuit of a variable impedance device, comprising two parallel connected space discharge tubes 4. The common output circuit of the tube 4 is associated with the space current circuit of two parallelconnected'space discharge devices 5 having their input and output circuits coupled in feedback relation by the antenna circuit 6 1 5 to constitute a high frequency oscillator.

Energizing current is supplied to the amplifier, variable impedance device and the oscillator by the generators 10 and 11 directconnected by a shaft 9 to a driving motor 8. A direct current motor is shown but an alternating current motor may also be used. The low voltage generator 10 supplies heating current to the filaments and the high voltage generator 11 supplies curent to the space paths of the discharge devices 3, 4 and 5.

The overload circuit breaker 12 serves to control the space current supply circuit for the discharge devices.

The radio transmitter is provided with a starting control circuit which includes the switch 13, battery 14 and electromagnetic switch or relay 15. a

The low voltage generator 10 supplies current to a circuit 16, including its field winding 17 in series with control resistances 18 and 19.

The circuit 16 is connected to the circuit 20 which includes the winding of a relay 21, the stationary contacts of a time-delay switch 22 and the armature of the relay 15. The winding of the time-delay switch 22 is connected to the circuit 16 by the conductors 23.

Switch 24 serves to connect the low voltage generator 10 to the filament heating circuit 25 for the devices 3, "4 and 5. Switch 26 is adapted to connect the high voltage generator 11 to the space paths of the devices 3, 4 and 5. Switch 27 is provided for connecting the field winding 28 of the generator 11 to the circuit 16.

The space current circuit of the speech amplifier 3 extends from the positive terminal of the generator 11, through the right hand blade of switch 26 which would be closed, circuit breaker 12, resistance 29, choke coil 30' to the anode, across the space path within the device to its cathode, conductor 31, resistance 32, conductor 33 and left hand blade of switch 26 to the negative terminal of the generator 11.

The alternating current output circuit of the amplifier is coupled to the grid-cathode circuitof the tubes 4 by the condenser 35. The coil 30, through which space current is supplied to the amplifier 3, is of high impedance for speech frequency currents.

Space current is supplied to the variable impedance device, comprising the arallelconnected discharge tubes 4, an oscil ator, including the tubes 5, from the positive terminal of source 11, through right hand-contact of switch 26, circuit breaker 12, choke coils 37 and 38, coils 39 and 44, anodes of 4 and 5 across the space paths within them to their cathodes, .heating circuit 25, conductor 31, resistance 32, conductor 33 and left hand contact of switch 26 to the negative terminal of the source 26.

The alternating output current circuit for the variable impedance device, consistin of tubes 4, may be traced from the are lelconnected anodes, anti-singing cho re coils 39, coils 38 and 37 condenser 40, resistance 32, conductor 31, heating circuit 25, cathodes of the tubes and across the space paths within them to their anodes. The high imdedance of coils 37 and 38 at speech frequencies forces the alternating current of these frequencies to traverse the tubes 5.

Space current for the amplifier 3 as well as the variable impedance tubes 4 and tubes 5, and the alternating output current of the tubes 4 flow through the resistance 32. The

potential drop due to the fiow of space current through 32 is impressed upon the impedance control electrodes of the devices 3 and 4 to polarize them for a purpose now well understood.

The alternating output current flowing through res stance 32 sets up an alternating potential drop thereacross which would be impressed upon the input circuit of amplifier 3 and tend to interfere with its proper operation. To prevent this the polarizing potential is suppl ed through a resistance 41 which cooperate. with the condensers 36 to constitute a filter adapted to substantially absorb or suppress the interferin alternating potential developed in the resistance 32.

' Space current is supplied to the oscillating tubes 5 by generator 11 over a path similar to that for tubes 4 to the upper terminal of coil 38. From this point it is transmitted through the radio frequency choke 42, coil 43, anttsinging choke coils 44, anodes of tubes 5, across the space paths within them to their cathodes and thence by the same path as for tubes 4 to the negative terminal of source 11.

The input circuit of the tubes 5 extends from their cathodes across the space within them to their grids, coil 45 and leak path 46, including a condenser shunted by a resistance, to their cathodes.

The output coil 43 is coupled to the input coil 45 by the antenna circuit 6, which includes a variometer, whereby energy is fed back to cause the production of high frequency oscillations. The variometer is provided to permit the constants of the antenna circuit to be adjusted, whereby the frequency of the oscillations generated may be adjusted.

A variable condenser 47, included in the output circuit of the oscillator is used to efl'ect reactance adjustments of this circuit. The alternating output current circuit of the oscillating tubes is completed through the condenser 48.

The operation of the transmitter described above may be described as follows. S eech current supplied by the circuit 1, after eing amplified, is impressed upon the common input circuit of the tubes 4 to control the armatures.

eonora tlow of space current within them and thereby control the space current flow within the oscillating tubes 5. with the result that the high frequency oscillations produced by the latter have their amplitudes modulated in accordance with the speech currents.

This arrangement utilizes the principles of the constant current modulation system described in Patent No. 1,442,147, January 16, 1923, to Heisinq. to which reference may be made for a complete description of its method of operation.

The operation of the control mechanism in starting up the transmitter may now be explained. With the motor 8 operating, the switch 13 will be closed to energize the relay 15 which pulls up its armature to close one break in the circuit 20. However this circuit is not completed, because the contacts of switch 22 are not in engagement.

The switches 24, 26. 27 and circuit breaker 12 are then closed. The field circuit 17 of the generator 10, including the resistance 18 and 19, will be completed, but the field circuit 0. the generator 11 will be open at the right hand contact of relay 21. Current will be supplied from generator 10 through switch 24 to the filaments of the devices 3. 4t and 5, to heat them, and through circuit 23 to energize the winding of the time-relay switch 22.

When the switch 22 operates to close its contacts, circuit 20 will be completed to energize the relay 21 and pull up both of its The left hand armature will short circuit the resistance is in the field circuit of the generator 10, whereby the current supplied by this generator is increased. The right hand armature completes the field circuit of the generator 11, which is supplied with exciting current from the generator 10 through the circuit 16 and switch 27.

By providing the resistance 18, and controlling it in the manner described above, the generator 10 may be regulated to supply heating current of the proper amplitude to the filaments ot the discharge devices at all times, whet-her the generator 11 is active or not. In this manner overheating of'the filaments or unstable operation of the dis charge devices is prevented.

In accordance with the operation of this control arrangement. heating current supplied to the filaments of the devices is held within safe limits at all times, and the switch 22 is used to maintain the field winding circuit of the high voltage generator open until the filaments are heated to a temperature at which space current may be safely supplied to the devices. However, when the field winding of the generator 11 is completed the volta e developed across its armature is inerel that due to the residual magnetism of its field. As the current supplied to the winding 28 increases, the field builds up and the amplitude of the space current and voltage gradually increase from substantially zero to full value. Thus an appreciable interval of time elapses between the time when the generator 11 becomes active and the time full voltage and current are applied to the space paths of the discharge devices.

This arrangement therefore provides means for sequentially controlling the application of energizing currents to space discharge devices, so that the liability of in juring or destroying them is substantially eliminated, and is especially; desirable for use with systems in which surges may develop due to the presence of reactance of relatively large magnitude in the circuits' A- radio telephone transmitter of the type described above has been used for broadcasting entertainments. The output circuit, of the low frequency or speech amplifier included a choke coil the inductance of which at speech frequencies was 40 henries and a by-pass condenser having acapacity of 2 microfarads. The output circuit of the 'ariable impedance device included two choke coils, connected in series the inductance of each of which at speech frequencies was approximately 4 henries, and a bypass con= denser of 2 microfarads capacity. Space current was supplied to the discharge devices at approximately 1600 volts. Starting this transmitter by supplying space current to the discharge devices at full voltage of the source, 1600 volts, resulted in the production of severe surges which at times damaged certain of the space discharge devices.

When the control method of the present invention was used to start the transmitter described in the preceding paragraph. no troublesome surge voltages were produced in the circuits.

While a particular arrangement and certain details have been described with the object of clearly and completely disclosing the nature of the invention. it is to be understood that- .this invention is not limited thereto, but only by the scope of the attached claims.

What is claimed is:

, 1. The method of operating a space discharge device having a cathode and an anode, which comprises supplying heating current to the cathode and, after a definite time interval controlled by the heating current, applying space current at substantially zero voltage to the device and gradually increasing the voltage to normal value.

2. The method of operating a system including space discharge devices having a cathode and an anode, which comprises supplying heating current to the cathodes and thereby initiating, after the cathodes are fully heated, the supply to the devices of increases cathode and an anode, which comprises sup' plying heating current from one generator to the cathodes and thereby initiating. after" a definite interval, the operation of the other generator, whereby current gradually increasin from a log to normal amplitude is supplied to the anodes of said devices.

4:. In combination a space discharge device including a cathode and an anode, a source for supplying heating current to said cathode, a source for supplying space current to-said device and means associated with said heating source for controlling, at a definite interval of time after heating current is supplied to said cathode, said other source to supply to said device space current gradually increasing to normal amplitude.

5. An electrical system comprising a space discharge device having a cathode and an anode, generators for supplying energy thereto, a control station having means for controlling said generators sequentially, whereby one of said generators supplies energizing current to one of the electrodes of said'device for a definite interval before the other generator becomes operative to supply gradually increasing current to the electrodes of said device.

6. A space discharge system comprising a plurality of discharge devices each having a cathode and an anode, generators for supplying energizing current to said devices, means for supplying current from one of said generators to said cathodes and means for, after a definite interval, completing the field circuit of said other generator whereby gradually increasing current is supplied to the space paths of said devices.

7. A space discharge system comprising a plurality of discharge devices each having a. cathode and an anode, generators for supplyin energizing current to said devices, one 0% said generators supplying current to said cathodes a time-delay switch also supplied with current by said cathode supply generator and means controlled by said switch for completing the field circuit of said other generator which supplies current to the space paths of said devices.

8. A space discharge system comprising a plurality of discharge devices each having a cathode and an anode, generators for supplying energizing current to said devices, one of said generators supplying current to said cathodes a time-dela switch also supplied with current by said cathode supply generator and a relay controlled by said switch for controlling the supply of field current to said other generator which supplies current to the space paths of said devices.

In witness whereof, I hereunto subscribe my name this 9th day of April A. D., 192%.

ARTHUR W. KISHPAUGH.

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