US2460160A

US2460160A - High-low impedance electron tube detector

Info

Publication number: US2460160A
Application number: US631723A
Authority: US
Inventors: Hubert H Wittenberg
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1945-11-29
Filing date: 1945-11-29
Publication date: 1949-01-25
Anticipated expiration: 1966-01-25

Description

Filed Nov. 29, 1945 Jan. 25, 1949. I H. H. WITTENBERG 2,460,160

HIGH-LOW IMPEDENCE ELECTRON TUBE DETECTOR 2 Sheets-Sheet 2 I r z c/ fiewrak I Z c I rm anew) INVENTOR ATTORNEY Patented Jan. 25, 1949 UNITED STAT HIGH-LOW IMPEDANCE ELECTRON TUBE DETECTOR Hubert H. Wittenberg, Lancaster, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application November 29, 1945, Serial No. 631,723

6 Claims. (Cl. 250-27) This invention relates to protective systems such as are useful in producing an effect in response either to a relatively low impedance or to a relatively high impedance between a pair of conductors which may be, for example, the two rails of a railway crossover or the like.

It is well known that there exists between the rails of any section of a railway an impedance which varies with the weather from a relatively low impedance in Wet weather to a, relatively high impedance in dry weather. Such variation in impedance is denoted herein as the normal range of variation in the impedance between the two rails or conductors. Any protective system associated with such conductors must of course be insensitive to this normal range of values of the impedance between the conductors.

The protective system, however, should be sensitive to impedances outsid the normal range. Thus in the case of a short circuitbetween the two conductors when the impedance is below the normal range, the protective system should produce an effect such as lighting a red signal. Likewise in the case of an open circuit when the impedance is above the normal range, the system should produce the same effect.

In accordance with the present invention, this result is achieved by'a protective system wherein (l) a unilateral impedance device such as 2. rectifier is connected between the conductors'at one of their ends, (2) an alternating potential input means and a resistor are connected in series between the conductors at the other of their ends, (3) a pair of electron discharge devices connected in push-pull relationship each having applied to its anode and shield grid alternating potentials which are arranged to be of opposite polarity for ensuring its deenergization when the potential of its control grid decreases to a predetermined posi-' tive value, and (4) alternating potential bias means are connected between the conductors and the controlgrid circuits of the two electron discharge devices so that one of the devices is deencrgized during the positive halt cycle of its anode potential in response to an. impedance lower than the normal range and the other of said devices is deenergized during the negative half cycle of its anode potential in response to an impedance higher than the normal range.

An important feature of one modification of the invention is the interconnection of the oathode heater and the shield grid of each device so that the device is d'eenergiz'ed in response to fail-' ure of the shield grid circuit.

Important objects of the invention are the provision of an improved protective system which is insensitive to a predetermined or normal range of impedance values but is sensitive to impedance values above or below such range, the provision of a protective system which always fails safef so that any defect in the system instantly produces a danger signal, and the provision of an improved protective system and method of operation whereby failure of the system or dangerous conditions of the circuit protected are immediately indicated by a danger signal. r The invention will be better understood from the following description considered in connection with the accompanyingdrawings and its scope is indicated by the appended claims.

Referring to the drawings: Figure 1 is a wiring diagram of one modification of the invention, 7 Figures 2A to 2B are explanatory curves relating to the operation of the system of Figure 1, and Figure 3 is a wiring diagram of a modified form of the invention. v

The system of Figure 1 includes a pair of con ductors Ill and II. Connected between these conductors at one of their ends is a unilateral imped-' ance device l2 illustrated as a copper oxide rectifier. At the other of their ends the two conductors are interconnected through a resistor l3 and alternating potential input means I4 illus trated as the secondary winding of a transformer. Dotted line resistors R1 and R2 are intended to denote the normal range of variation in the impedance between the conductors.

A pair of electron discharge devices l5 and IE connected in push-pull relationship have potential applied to their anodes and shield grids from the secondary windings Ts! to T85 of a transformer I I. It should be observed that (1) current also is supplied from the secondary Ts3 to the cathodeheaters of the devices I5 and I6, (2) a relay RL! shunted by an 8 microfarad capacitor is connected in the anode circuit of the device l5, and (3) a relay RLZ shunted by an 8 microfarad capacitor is connected in the anode circuit of the device I6. I

These relays RM and RL2 are series-connected in a control circuit in a well known manner so that deenergization of either of them actuates a controlled device such as a danger signal.

Bias potential for the control grids of the devices l5 and i5 is applied through a transformer winding T35 and a pair of 500 ohm resistors l8 and i9. Control potential is applied to" the con, trol grids from a 10 k.-resistor 20 which is connected between the conductors l0 and H at the "near end of the conductors. The control grid circuit of the device [5 is from the cathode through the resistor 20, the resistor I8 and a 100 k. resistor 2| (shunted by 0.1 microfarad capacitor) to the control grid. The control grid circuit of the device is from the cathode through resistors 20, i9 and 22 to the control grid. Eachof these control grid circuits is shuntedby a separate 0.002 microfarad capacitor,

Figures 2A to 215 show the relation between;

the various alternating potentials involved in the operation of the system. c

In Figure 2A, the critical voltage below which the device I5 is deenergized. is denoted by a dotted line curve and the anode and shield grid voltages of the device 15 are denoted respectively by the curves [es and leccz.

In Figure 2B, the bias voltage applied through as that of Figure 1 with the exception that failure of a shield grid circuit of Figure 3 deenergizes the defective device.

In the modification of Figure l, a danger signal is produced by interruption of the alternating potential supply; failure of the electron emission of either of the devices IE or IS, a break in any of the control grid resistors which permits the shield grid to deenergize the device, and failure the transformer secondary to the control grid. I

of the device I5 is indicated by the curve lecci.

In Figure 2C, the curveea denotes the potential applied by the secondary winding M, the curveet denotes the potential actually applied between the conductors when current flows through the normal impedance between the conductors, the curve leer (no train) denotes the resultant potential applied to the control grid of the device [5 when the impedance between the conductors is within its normal range and the curve leg (with train) denotes the potential applied to the control grid of the device l5 when the impedance between the conductors is below its normal range.

It will be noted that. in passing from the potential [e01 (no train) to the potential lecl (with train), the control grid of the device i5 assumes the critical grid voltage of this device.v This results in deenergization of the device I 5 and operation of the relay RLi as previously explained.

In Figures 2D to 2F, the various potentials involved in the operation of the tube 28 are shown. In these figures, 26b denotes anode voltage, 2cm denotes shield grid voltage, 2cm denotes control grid bias voltage, 2c1 (track 07c) denotes the resultant control grid voltage when the impedance between the conductors is within its normal range and Zen (track open) denotes the resultant control'grid voltage when the impedance between the conductors is above its normal range.

It will be noted that in passing between the potentials 2601 (track ck) and 2601 (track open) the control grid of thedevice l6 assumes the critical grid voltage of this device. This results indeenergization of the device I 6 and operation of the relay RL2 as previously explained.

The electron discharge devices I5 and I 6 of Figure 1 are gaseous electron discharge devices of the RCA 2050 type. In their stead may .be used gaseous electron discharge devices of the RCA 2D21 type which are provided with exe ternal leads to the opposite ends of their shield grids.

Figure 3 shows how the RCA 21321 device is connected into the circuit. Thus. the cathode heaters of the devices i5 and i 5' are connected in series with their shield grids to the transformer secondaries E93 and Ts l, and the cathodes of the two devices are-connected to the

adjustable contacts

24 and 25 of resistors 25 and 27 whichare connected respectively across the secondary T53 and. the secondary Tsd. With these connections, any break of the shield grid circuit deenergizes the device so that the. system. fails safe-(with a red light showing) v V V Figure3also shows a 1 k. resistor in serieswith of the rectifier which deenergizes the device l6. The modification of Fig. 3 affords the added protection that a danger signal is produced by interruption of the shield grid circuit which terminates electron emission and deenergizes the device.

. Important advantages of the present invention are that it'is insensitive to impedance changes within a normal range but is sensitive to impedance without such range and that it produces a danger signal (1) in response to any interconductor impedance without the normal range and (2) in response to failure of the protective system itself.

, I claim as my invention:

The combination of a pair of electron discharge devices connected in push-pull relation and each having a cathode, an anode and con trol and shield grids, means for applying alternating potentials of opposite polarities to the anode. and shield grid of each of said devices, a

40 pair of conductors, and means interconnecting said. conductors with each other and with said control grids for deenergizing one of said devices when the impedance between said conductors assumes a predetermined relatively low value and for deenergizing the other of said devices when said impedance assumes a relatively high value.

2. The combination ofv a pair of electron dischargedevices connected in push-pull relation and each havin a cathode, cathode-heater, an anode and control and shield grids, means for applying through the cathode heater to the shield grid of each of said devices an alternating potentialof a polarity opposite to that of its anode, a pair of conductors, and means interconnecting said conductors with one another and with said control grids for. deenergizing one of said devices when: the impedance between said conductors assumes a relatively low value and for deenergizlng the other of said devices when said impedance assumes a relatively high value.

3; The combination of a pair of electron discharge devices connected in push-pull relation and each having a cathode, an anode and control and shield grids, means for applying alternating potentials of opposite polarities to the anode and shield grid of each of said devices, a pair of con duct'or's, a rectifier connected between said corductors at one of their ends, a resistor and alter-- hating potential input means connected in series between said conductors at the other of their ends, and means interconnecting said conductors andsaid control gridsior deenergizing one of said devices when the impedance between said. conductors assumes-a relatively lowvalue and for 4. The combination of a pair of electron discharge devices connected in push-pull relation and each having a cathode, an anode and control and shield grids, means for applying alternating potentials of opposite polarities to the anode and shield rid of each of said devices, and means interconnecting said conductors with one another and with said control grids for deenergizing one of said devices during a positive half cycle of its anode potential in response to a relatively low irnpedance between said conductors and for deenergizing the other of said devices during a negative half cycle of its anode potential in response to a relatively high impedance between said conductors.

5. The combination of a pair of electron discharge devices connected in push-pull relation and each having a cathode, an anode and control and shield grids, means for applying alternating potentials of opposite polarities to the anode and shield grid of each of said devices, and means interconnecting said conductors with one another and with said control grids for deenergizing one of said devices during a positive half cycle of its anode potential in response to a relatively low impedance between said conductors and for deenergizing the other of said devices during a negative half cycle of its anode potential in response to a relatively high impedance between said conductors, and relay means for producing an effect in response to deenergization of either of said de- V1088.

6. The combination of a pair of electron discharge devices connected in push-pull relation and each having a cathode, an anode and control and shield grids, means for applying alternating potentials of opposite polarities to the anode and shield grid of each of said devices, a pair of conductors, a rectifier connected between said conductors at one of their ends, a resistor and alternating potential input means connected in series between said conductor at the other of their ends, means connecting one of said conductors to the cathodes of said devices, and alternating potential bias means connected between the other of said conductors and said control grids.

HUBERT H. WITTENBERG.

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

UNITED STATES PATENTS Boerner et a1 Dec. 10,