US2050059A

US2050059A - Relay system

Info

Publication number: US2050059A
Application number: US713621A
Authority: US
Inventors: Winfield R Koch
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1934-03-01
Filing date: 1934-03-01
Publication date: 1936-08-04
Anticipated expiration: 1953-08-04
Also published as: GB452927A

Description

Aug; 4, 1936. y w. R. KOCH 2,050,059

RELAY SYSTEM Filed March 1, 1934 OJYIC 15 L 1:5: j jig: j! 7 4T we F933 INVENTO/Ef Patented Aug. 4, 1936 UNITE-D STATES RELAY SYSTEM Winfield R. Koch, Camden, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application March 1,

7 Claims.

My invention relates to thermionic or electric discharge tube utilization networks analogous to the one shown on page 167 et seq., volume 2, textbook on Wireless Telegraphy, (British) by Rupert Stanley, 1923 edition.

More particularly, the invention relates to relay systems wherein thermionic or electricdischarge tubes are utilized-as triggered controlling elements for operating current responsive and other electrical devices connected in circuit therewith. In aspeciflc form of the invention, a multi-vibrator type of circuit is employed for the purpose of providing a-relay circuit having the characteristics of an amplifier and certain characteristics of a multi-vibrator.

Heretofore, the multi-vibrator, so called as exemplied by the publication referred to, has been utilized principally for the production of oscillations rich in harmonics. Insofar as I am aware,

however, the multi-vibrator or an equivalent cir- 'affected by changes in atmospheric conditions.

It is, accordingly, an object of my invention to provide an amplifier of the direct-connected type that shall not require a high potential plate supply source, and coupling condensers between inter-connected anodes and grids While maintaining a high degree of stability.

Another object of my invention is to provide an amplifier or relay of the trigger-action type, the output current from which need not necessarily be proportional in amplitude to the input potential applied thereto. l

Another object of my invention'is to provide a relay of the type referred to wherein the duration of the output current is independent of th duration of the input potential.

Another object of my invention isl to provide, in a relay of the type referred to immediately above, means whereby the said relay automatically returns to normal condition upon removal of input potential.

Another object of my invention is to provide a trigger rel-ay of the type referred to that shall have an voutput current which goes through a definite cycle in response to a change in input 1934, Serial No. 713,621

(Cl. Z50-36) potential and automatically returns to normal value.

Another object of my invention is to provide a trigger relay that shall ybe responsive only to input potentials having a predetermined duration.

Another object of my invention is to provide an oscillator of the multi-vibrator type, characterized by the fact that from the output circuits of the several tubes included therein wave-forms having differing frequency characteristics may be l0 obtained.

A still further object of my invention is to provide an oscillator of the type referred to that shall be capable of oscillating more strongly than oscillators of conventional multi-vibrator types, and l5 with greater stability. p

The foregoing objects and other objects ancillary thereto I accomplish in preferred embodiments of my invention through the use of electric discharge devices or tubes of the so-called screen grid pentode type known commercially as RCA-57, RCA-58 and the like.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organizalni and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a speciflc embodiment, when read in connection with the accompanying drawing, in which:

Figure 1 is a schematic circuit diagramof a direct connected electric discharge amplifier for direct current and audio frequency signals down to relatively low frequency values, althouglhigher frequency signals such as radio frequency slg nals may be amplified thereby;

Fig. 2 is a similar` schematic circuit diagram of a relay circuit embodying two direct connected electric discharge devices arranged for trigger" control;

Fig. 3ds/also a similar diagram of a. trigger relay provided with means whereby it is self restoring; and

Figs. 4, 5, and 6 are schematic circuit diagrams exemplifying the application of the invention to oscillators of the multi-vibrator type.

Referring to Fig. 1 of the drawing, which is fundamental to the remaining figures, an amplifier constructed according to my invention preferably comprises a plurality of electric discharge devices or tubes i and 3 of the so-called screengrid pentode type. The first tube I ls provided with an anode 5, a suppressor grid 1, a screen grid 9, a control grid Il, and a cathode 55 I3. The second tube 3 is identical in construction and is also provided with an anode I5, a. suppressor grid |1, a screen grid I9, a control grid 2|, and a cathode 23.

The anodes of the severalltubes are connected to the positive terminal of `a plate potential source over resistors and 21 respectively, the last-named resistor providing the output impedance of the system and being provided with output terminals E2. The green grid of the rst tube, I, is also connected to the positive lead of the plate potential source and a direct connection 26 extends from the plate of that tube to the screen grid of the second tube, 3.

The cathodes of the several tubes are connectc together and to' the negative terminal of the plate potential source. The control grid of the rst tube is connected to the cathode through a grid leak I2 and is provided'with input terminals E1 across said resistor. The control grid 2| of the second tube. may be connected to its cathode directly or through a grid leak 22, as shown in the drawing.v

It will be noted from an inspection of Figure l of the drawing that there is no cross-connection from the plate of the second tube back to the screen -grid of the rst tube. Such being the case, the-operating condition of the first tube is not appreciably influenced by the condition of the second tube, and the system may be utilized as a direct current amplifier, or an amplifier for alternating current at any frequency from zero up to a limiting frequency determined by the input capacity of the tube.

The' operation of the system shown in Fig. l is as follows:

Direct current potentials or alternating current signal potentials applied to the input terminals designated at E1 are applied to the screen grid I9 of the second amplifier stage through the coupling impedance 25 in circuit with the anode 5 of the first amplifier stage.

Signals applied to the screen grid i9 are amplied and may be derived from the anode circuit connected with the anode i5 and, in the present example, are taken in parallel with the output impedance 21 from the terminals E2.

This system has the advantage that since the screen grid I 9 and the anode 5 may operate at the same potentials they may be directly connected as shown, whereby the coupling system is reduced to a. single impedance device 25 and the usual coupling condenser is eliminated, thereby improving the frequency response. Furthermore, the usual high voltage source of anode potentials or the separate battery source of anode potentials and separate filament supply circuits ordinarilyy required by the usual D. C. amplier are not .required in the present amplifier' system.

In the case that an additional stage of amplification is desired, a second amplifier may be connected with the device 3 through the output terminals E2 in the same manner as the device 3 is coupled to the device I, through a coupling imped-ance or resistor in the anode circuit of one device and a direct connection from the anode end thereof to the screen grid ofthe amplifier device in the succeeding amplifier stage.

Referring now to Fig. 2, a pair of electric discharge amplifier devices 30 and 3| of the screen grid pentode type are shown connected in a balanced amplifier circuit similar to that of a multivibrator. In this circuit, however, the devices 30 and '3L do not operate as oscillators but as relays of the trigger type. In this type of re' lay, a change in control grid voltage sets\the relay in action to cause a change in anode current from one predetermined value to another.

In the present example, the anode 32 of the device 30 is provided with a coupling impedance 33 by which it is coupled through a connection' 34 with the screen grid 35 of the second device 3|.. In a similar manner the anode 36 of the device 3| is coupled back through the impedance 31 and connection 38 with the screen grid 39 of the first device 30. The anodes and screen grids of the pair of amplifiers are thus cross connected. Grid leak connections to the cathode are provided for the control grids 40 through

grid leak resistors

42 and 43. Likewise, the suppressor grids 4I are connected to the cathodes whereby the same operating potentials may advantageously bev used on both anodes and screen grids, thereby permitting a direct connection between amplifiers and common coupling imped- 20 The latter terminals are short-circuited but may be open-circuited for applying signal potentials to the grid 40.

The output circuits of the devices 30 and 3| may be connected to any suitable utilization means and in the present example, the. output circuit for the device 3| is connected with a current responsive device such as a relay 46 which is connected in series with the coupling impedance 31 adjacent to the anode 36. A series output circuit is thereby provided for the device 3|.

However, itis desirable under certain circumstances, to utilize a shunt output connection, whichvis shown in connection withthe device 30, an output circuit therefor being indicated by the leads 4'|. It will be noted that these leads are connected between the anode and the cathode of the device 30 and that the arrangement is such that the coupling device 33 is utilized as an output impedance for the leads 41.

The operation of the relay is as follows:

A small negative signal potential on the input terminals 44 causes a reduction in the anode current of the first amplifier device 30 through the coupling impedance 33. This causes a reduction in the I. R. drop through the impedance and a corresponding increase in the potential on the anode 32 of the iirst amplifier device 30 and on the screen grid 35 of the second amplifier device 3|. The increased screen grid potential causes an increase in the anode current of the device 3| and a corresponding increase in the I. R. drop through the coupling impedance 31.

The latter action results in a reduction of the potential on theanode 36 and on the screen grid 39 and this in turn further decreases the anode current through the impedance 33. This action slightly negative to start the operation of the relay from the condition above described.

To restore the relay to its normal condition or to reverse the operation above described, a positive potential may be applied to the grid 40 at the terminals 44 or, preferably, a slightly negative potential is applied to they grid 40 of the device 3| whereupon the relay operates to reduce the anode current of the device 3| to substantially zero and to restore it to normal through the device 30.

For the purpose of triggering the relay in either direction to actuate the current responsive device 46 in circuit therewith or to restore the relay system to a normal condition of operation, a source of negative or positive potential 48 may be provided in connection with the grids 4|), and this potential may be applied selectively to either of said grids, that is. between grid and cathode of either tube, through a suitable selective switching means 49 and grid potential supply leads 50. From an inspection of the circuit, it will be seen that the switch 49 may be closed in either one of two directions to apply a potential from the source 38 through the leads 50 to a selected one of the grids 4D.

The controlling potential for the relay may be applied to the input terminals 45 for the device 3| by removing the short circuit therefrom and the signal output from the relay system may be taken from the output impedance 33 through the output leads 41.

'I'he use of a separate input circuit for each of the devices 3U and 3| has the advantage that the system may be utilized to respond to two different control voltages if applied thereto in proper sequence.

'Ihe anode current in one of the devices 30 or 3| is always substantially zero and at a maximum in the other. A small negative potential on the grid of the device taking anode current will cause the anode current to suddenly and completely drop to substantially zero and the anode current of the other device to as suddenly and completely increase to a maximum. The relay is therefore of the trigger type, but is somewhat different from the usual type in that the change from zero to maximum plate current has no intermediate stopping point and is substantially instantaneous.

Relatively low positive potential on the other grid, that is the grid of the device not taking plate current will cause the same result. It has been found that a control potential of less than 1.5 volts, with suitable amplifier devices such as the RCA- 57 and RCA-58 tubes will provide a Wide change of voltage in the plate resistors, which may be in the order of a hundred or more volts.

By way of example, the coupling resistors or impedances 33 and 3'! may have a value of substantially twenty to thirty thousand ohms, while the input coupling impedance or

grid leak resistors

42 and 43 may have any desired value, depending upon the impedance of the input circuit and the voltages to be applied to the control grids. The anode potential supply leads indicated at 5| and 52 may be supplied direct current potentials of substantially 250 volts for tubes of the type hereinbefore designated.

With the circuit arrangement as above described, it will be seen that the application of a positive potential to the grid of the device in which the plate current is maximum will have no affect upon the equilibrium of the system, whereas the application of even a slightly negative potential thereto will cause the relay to be actuated.

The application of vcontrolling or triggering potentials alternately to the control grid circuits for actuating the relay circuit inalternate directions must therefore occur in a predetermined sequence.

In this circuit also, advantage is taken of the 5 fact that the screen grids of screen grid pentode' devices may be connected withfthe same potential source as the anodes, whereby the anodes and screen grids ofthe relay device may be interconnected directly without coupling condensers or 10 the like as in the preceding amplifier circuit of Fig. 1. 'Ihe use of the suppressor grid permits plate voltage to be the same as the screen voltage Without a loss of efficiency.

. Referring now to Fig. 3, /a trigger relay similar 15 to that shown in Fig. 2 is further provided with means whereby it is automatically restored to a normal operating condition upon completion of the operating cycle. In this figure, the circuit connections and circuit elements are sub- 20 stantially the same as in Fig. 2 and bear the same reference numerals.

It will be noted that the amplifier device 3| is provided with signal or control voltage input terminals, connected across the grid circuit re- 25 sistor 43 of the device 3| for applying controlling potentials to the control grid 4Il of said device. 'I'he device 3| is, therefore, the first amplifier in this circuit.

Having selected the device as a first amplifier 30 for receiving ,the controlling potentials, the second control grid, that is the control grid of the second amplifier device 3|! is coupled with the screen grid of the same device, through a coupling condenser. 'I'his condenser is shown at 53, connected between the screen grid 39 and the adjacent control grid 40 of the device 30. The specific circuit arrangement is such that the condenser 53 and the grid impedance 42 provide a time delay filter or network in connection with the said second control grid, the first control grid being considered as that selected to receive controlling potentials directly as above indicated.

It will be noted that there is also provided in connection with each of the control grid circuits a source of biasing potential arranged to provide a higher negative bias on one grid than upon the other. In the present example the device 3U is provided with a higher biasing potential from a source, 55 than the corresponding biasing potential obtained from a source 54, for the device 3|.

The operation of the system described is as follows:

A short signal impulse applied to the input terminals 56 is *applied to the grid of the first amplifier device or tube 3| and causes the relay system to pass through a complete cycle, the length of which depends upon the capacity and impedance vvalues in the time delay network 60 53-42 provided in connection with the second amplifier device 30.

When a negative impulse is applied to the control grid 40 of the device 3| from the signal input terminals 56, the plate current of said device decreases to zero while the plate current of the device 30 increases to a maximum substantially in the same manner as described in connection with Fig. 2. Following this operation, the plate current in the device 3| increases and 70 the plate current in the device 30 decreases, the former becoming maximum and the latter becoming substantially zero whereupon the relay system is restored to normal and is ready for a second control impulse.

The delay in the cycle results from the control effect of the delay network comprising the cou- "lay circuit may operate to control a device connected in circuit therewith such as the current responsive device 56.

If the time delay network is connected with the control grid having a less negative bias, then, instead of a relay which may be operated to pass through a predetermined cycle in response to a signal controlling impulse of any duration, an oscillatory circuit is provided, the frequency of oscillation being determined by the impedance of the time delay network.

Such a circuit is shown in Fig. 4i to which attention is now directed, and in which the same reference numerals are applied to like parts as in Fig. 3.

In Fig. 4, the screen grid pentode tubes dil and 3l are directly interconnected through anode coupling impedances 33 and Tl and grid leads 36 and 38. A relatively higher negative bias is provided by the source 55 for the control grid dll of the device 3@ than is provided by the source 54 for the corresponding control grid of the device 3l.

Grid impedances 42 and 43 are provided in the control grid circuits, and the impedance d3 is connected with a coupling condenser 53 to the screen grid lead 34 so that the filter network is provided in connection with the control grid to which the lower negative bias is supplied.

Output terminals are provided as indicated at 53, 59, 60 and 6l. The output terminals 5B are in series with the anode 36 of the device 3l, adjacent thereto, and between the anode and the coupling impedance 31. The short circuit across the terminals 58 is removed when taking the output therefrom, and one of the terminals 58 and the terminal 59 may be employed for taking the output from the coupling impedance 3l in shunt therewith. If desired, the output energy from the oscillator may be taken from other points in the anode circuit such as from the cathode return lead through the terminals til, in short circuit being removed for this purpose.

In a similar manner, energy may be taken from the oscillator device 30 as indicated by the terminals 6I provided in the cathode return lead and corresponding to the terminals 63.

It has been found that in operation, in an oscillator device having a time delay network and the lower negative bias source of potential, as in this case for example, the oscillations are substantially rectangular in shape or square topped, while the wave shape oi' the oscillations in the other device is more generally saw-toothed in form. Therefore, in this type of cross-connected oscillator, wherein the coupling is direct and the control grids are biased at differing potentials, a time delay network may be applied, which permits two diiering wave forms to be provided in the generated oscillations.

It has been found that the time delay network may be provided in series with the screen grid circuit as shown in Fig. 5, t0 which attention is now directed. The time delay network is provided in the screen grid lead 38 in the form of a variable impedance or resistor 62 and a condenser 63 connected in shunt therewith'. This time delay network is connected between the coupling impedance 31 of one amplifier device at the anode end thereof, and the screen grid 39 of the other amplifier device.

The control grids 40 are provided with

series impedance elements

42 and 43, and it will be noted that the device 30, with which the time delay network is connected, is provided with a lower negative bias on the control grid. In this case, the bias potential is that of the cathode, while the device 3l is provided with a source 54 oi low negative potential for the control grid 40.

It has been found that the output from this type of oscillator is steady and its operation is stable over long periods of operation. The output is taken from the output of the anode circuits by any suitable connection such as hereinbefore described and as indicated by the series anode circuit output terminals 58. The use of the suppressor grid in the oscillator and amplifier circuits, as hereinbefore shown and described, materially aids in causing the circuits to operate without setting up undesired oscillations.

It will be seen that in the circuit shown, the suppressor grids are connected with the cathodes. Likewise, the control grids are also connected with cathode through an impedance device to which signals or control potentials may be applied. The signals or potentials are derived either from an external source or from the screen grid circuit. The screen grids are directly connected with the anodes of the balanced pair of ampliilers or oscillator devices for the reason the circuit connections are simplied and the suppressor grids tend to maintain the amplier devices in stable operation. The control grids are unbalanced by the initial biasing means therefore, in order that the balanced pair of devices may be arranged to operate as a relay or as an oscillator.

The external source of bias potential may be eliminated by utilizing the potential drop in anode circuit impedance devices, such as cathode resistors 64 and 65, as shown in Fig. 6. In this circuit, the control grid of each amplifier or` oscillator device is connected through leads 66 and 6l with' the cathode end of the bias resistor for the other device.

A time delay network is provided in connection with each of the control grids by means of a condenser 68 connected from each control grid to the cathode and a variable series impedance or resistor 69 in each of the control grid leads 66 and 61.

With this arrangement, the varying control potentials, existing across the impedances or cathode resistors 64 and 65, are applied to the control grids through the impedances 69 under control of condensers 6B, so that the potential changes on the control grids are relatively slow and maybe adjusted by adjusting the value of the impedances 69. The operation is otherwise the same as that for the oscillators shown and described in Figs. 4 and 5 and the same vreference numerals are applied to the same parts. The voltage output from each oscillator device is the same, both being rectangular type waves.

An oscillator as shown and described, has the advantage that vigorous oscillations are produced and the signal output is relatively strong. The circuit has the further advantage that cathode lead impedances provide the source of biasing potential for the oscillator.

The voltage or signal output may be taken from the anode circuit of either device, substantially in the same manner as described in connection with the preceding circuits, as from the

terminals

58 and 59.

I claim as my invention:

1. In a relay system, the combination of a pair of electric discharge devices each comprisingan anode, a cathode, a suppressor grid adjacent to the anode and connected to the cathode, a control grid adjacent to the cathode, and a screen grid between said suppressor and control grids, an anode coupling impedance in circuit with each of said anodes, means providing a connection between each control grid and the cathode, means providing a direct connection between the anode of one device and the screen grid of the other device, a condenser coupling the screen grid of one device to its control grid, a resistor connecting said control grid with the cathode of said device, and means for applying a more negative biasing potential to one of said control grids than to the other.

2. A balanced electric discharge delay circuit, including a pair of screen grid electric discharge amplifier devices conductively interconnected between the cathode of one device and the control grid of the other device and between the anode of each device and the screen grid of each other device, means for stabilizing said circuit including a suppressor grid in each of said devices connected to its cathode, means for applying a differing biasing potential on the control grids of said devices, and a time delay circuit network interconnecting the cathode and two of the grid electrodes including the suppressor grid of one of said devices and the anode of the other device.

3. A relay circuit including two electric discharge devices of the pentode type, a common coupling voltage drop producing impedance connected in circuit with the screen grid of one device and the anode of the other device, said circuit connection with said impedance providing a direct conductive connection between the last named screen grid and anode, the suppressor grids of said devices being connected to their respective cathodes for stabilizing said circuit, means for applying differing biasing potentials to the control grids of said devices, and a time delay circuit network interconnecting the cathode and two of the grid electrodes of said other device and the anode of said one device.

4. An oscillator circuit comprising a pair of electric discharge devices of the pentode type, each having a screen grid interconnected directly with the anode of the other device, a filter net- Work connected between the cathode and control grid of one tube and the cathode and control grid of the other tube, a connection between each suppressor grid and its cathode, a source of potential, and a potential drop producing impedance element in circuit with each cathode through said source to said anodes.

5; A multi-vibrator oscillator comprising in combination a pair of electric discharge devices of the pentode type, means for applying differing negative biasing potentials to the control grids of said device, a potential drop producing impedance element, the screen grid of one device and the anode of the other device being directly coupled through said impedance element, the anode of said one device providing an output connection for said oscillator, a time delay filter comprising a condenser and a resistor connected between the anode of said one device and the control grid of said other device, the resistor being in circuit between the cathode and the control grid of said other device.

6. A trigger amplifier comprising in combination, a pair of electric discharge devices of the pentode type each having a cathode, an anode, a suppressor grid adjacent to the anode and connected to the cathode, a control grid adjacent to the cathode and a screen grid interposed between said suppressor and control grids, means providing a direct connection between each screen grid and the anode of the other device, anode output coupling impedances connected one with each anode, means including an impedance device providing a connection between the control grid and the cathode of eachdevice, means for applying a controlling potential to one of said control grids, means for biasing said grid at a lower negative potential than the control grid of the other device, and a lter network connected with the screen and control grids of said other device and between the cathode thereof and the anode of said onedevice, said lter network including a variable impedance device.

7. In an electric relay system, the combination of a pair of electric discharge devices of the pentode type, having the anode of one device directly connected with the screen grid of the other device, and each having a suppressor grid and control grid connection with the cathode thereof, means for applying differing negative biasing potentials on the control grids of said devices, means for applying controlling potential impulses selectively to the control grids of said de-. vices, and a time delay circuit network interconsaid devices and the anode of said other device.

W'INFIELD R. KOCH.