US2863097A - Circuit arrangement for reducing the wear of gas discharge tubes - Google Patents

Description

Dec. 2, 1958 K. HAGENHAUS CIRCUIT ARRANGEMENT FOR REDUCING THE WEAR OF GAS DISCHARGE TUBES 3 SheetsSheet 1 Filed May 20, 1955 Fig.1

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Dec. 2, 1958. HAGENHA S. 2,863,097

K. CIRCUIT ARRANGEMENT FOR REDUCING THE WEAR 0F GAS DISCHARGE TUBES Filed May 20, 1955 5 Sheets-Sheet 2 Fig.3

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CIRCUIT ARRANGEMENT FOR REDUCING THE WEAR 0F GAS DISCHARGE TUBES Filed May 20, 1955 3 Sheets-Sheet 3 Fig.5

United States Patent Ofiice Patented Dec. 2, 1958 CIRCUIT ARRANGEMENT FOR REDUCING THE WEAR OF GASDISCHARGE TUBES Application May 20, 1955, Serial N 509,965

4 Claims. (Cl. $15-$45 This invention is concerned with circuit arrangements for reducing the wear of gas discharge tubes.

In the electronic transmission art and the electrical calculating machine field there are frequently employed counting circuits for counting electric pulses. For these counting circuits, there aregenerally used gaseous discharge tubes having a special control electrode, since their ability to remain conductive after firing independently of the voltage at the control electrode can be advantageous- 1y used. o Such counting circuits comprise individual stages each of which contains a gaseous discharge tube, and they 'operate in accordance with the following principle: In series with the cathode of each gaseous discharge tube there is connected a cathode resistance which is bridged by a capacitor. The control electrodes are connected in parallel with respect to the pulse-voltage source, that is, the pulses which are to be counted are fed simultaneously to all control electrodes. A gaseous discharge tube burning in the counting circuit permits a certain voltage drop to take place at its cathode resistor which voltage drop discharges the parallel-connected capacitor. By this voltage drop, the potential of the cathode of the corresponding gas discharge tube is raised. This increase in potential is'cornmunicated over a connection to the control electrode of the following tube, as a result of which the firing thereof upon the next pulse is prepared. This measure assures that at all times only the tube following a burning gaseous discharge tube can be fired by the next pulse. When such pulse takes place, the next tube therefore is fired. Since the capacitor which is connect-.

ed in parallel to the cathode resistor corresponding to this tube is uncharged at the moment that the tube is fired, a short circuit takes place at this moment so that momentarily the operating potential which thus is brought about exists between the plates of the tubes and the terminal points of the cathode resistors. This however means that the potential, on the preceding tube drops below the operating potential since a charged capacitor lies in series with it. Accordingly this tube must extinguish.

The preceding gaseous discharge tube extinguishes only when the lowering of the potential available to it remains below the operating potential for longer than the duration of the de-ionization time. The time constant determined by the, cathode resistors. and the parallel connected capacitors must accordingly be so selected that this requirement is met. The time constant, however, is frequently subject to a further condition, namely the requirement of higher counting speed, that is, the requirement that the potential which prepares for the firing of the next following tube and which is obtained from the cathode resistor of the preceding tube must be available as rapidly as possible. This requirement can be met only when a small time constant is selected.

In order to satisfy both requirements, it is generally necessary to make the cathode resistor of such ohmic resistance that upon the firing of the next following tube, the voltage betweenthe plate and cathode of the preceding tube is shifted toward opposite values. It has been found that this process has a very detrimental effect on gaseous discharge tubes and results in a substantial decrease in their life. This applies, of course, in general not only for counting circuits, but also for all circuits in which a potential displacement toward opposite values takes pl ce.

This disadvantage can be counteracted in accordance with the invention by feeding a gaseous discharge tube over the tap of a voltage divider, one part. of which com: prises a rectifier which, when the tube has been fired, is acted on by the tube current in forward direction, and the other part of which tap during the extinction process has such a resistance value that the greatest part of the voltage effecting the displacement in potential decays at the rectifier. The action of such a circuit is accordingly to permit the voltage effecting the potential displacement to decay at another'load, rather than at the gaseous discharge tube, in which connection the said load however must notbe present when the gaseous discharge tube is in fired condition. For this purpose, a rectifier is particularly well suited, since it can assume a high or a low resistance value depending on the direction of flow.

The various features and objects of the invention will appear in the course of the description which is rendered below with reference to the accompanying drawings. In these drawings,

Fig. 1 shows an embodiment according to the invention;

Figs. 2a, 2b and 3 are curves to explain the operation;

Fig. 4 illustrates a detail that may be employed in the circuit according to the invention;

Fig. 5 shows .a modified embodiment; and

Fig. 6 is a curveto explain the operation of Pig. 5.

The voltage divider can be constructed in various manners. In Fig. 1 there is shown a circuit in which the voltage divider comprises two rectifiers, which are connected together with opposite polarity. One rectifier is in series with the plate-cathode path of the tube and is acted upon by the tube current in forward direction. The other rectifier is oppositely connected and. lies in parallel to the tube. Accordingly, this rectifier will be acted upon in reverse direction when the tube is fired. The embodiment shown in this figure is a counting circuit which comprises three gaseous discharge tubes; therefore it can be used only for the counting of three pulses. The counting capacity of a counting circuit is however without importance in this connection. The gaseous discharge tubes R1, R2 and R3 each have two control electrodes S1 and S2. The pulse voltage taken from the generator G is fed to the control electrodes S1 over separate decoupling resistors W1, W2 and W3. The control electrodes S2 are connected over decoupling resistors W4, W5 and W6 to the cathodes of the respective preceding tubes so that the increase in potential at the control electrodes S2 which prepares for the firing of the respective tube is effected over this path. In quiescent or rest condition, there is present on all control electrodes a bias Ug which is fed to the control electrodes S2 over the series resistances W7, W8 and W9 and to the control electrodes S1 over a common series resistor W10 and via each of the three decoupling resistors W1, W2 and W3. The tubes R1, R2 and R3 receive their plate volt,- age over a common series resistor W11 from the common feed voltage source Usp, In the path from the cathode of tube R3, over the resistor W6 to the grid S2 of the tube R1 there is provided a key T upon the closing of which the counting circuit operates as cyclic counter. When the key is open, the circuit can count only up to tube R3,

The electric building-up operations taking place in the counting circuit will be described with reference to the diagrams shown in Figs. 2a and 2b, in which connection the rectifiers provided in the circuit will, for the time being, he left out of consideration. Let us assume that the counting circuit is in a condition in which tube R1 is burning. If a pulse is now supplied by the generator G, it passes also to the grid S1 of the tube R2, the grid S2 of which, as a result of the rise in potential derived from the cathode of tube R1, has such a bias that pulse fed the grid S1 of tube R2 at the moment Z1 is sutficient to fire this tube. The tube therefore operates and thus lowers the potential applied between the plate and ground to the operating potential for the time of the firing. This is shown in Fig. 2a by the solid line curve, which represents the course of the plate voltage between the plates and ground. At the time II of the diagram shown in Fig. 2a, there takes place a sudden drop of the plate voltage Ua to the operating voltage Ub. Thereupon' the capacitor C2 connected in parallel to the cathode resistance W13 starts to charge itself as a result of the potential drop at the cathode resistance W13. The plate voltage Ua thus increases in accordance with a natural logarithmic function back to the old value. The dotdash curve shows the course of the cathode voltage Ukl, which occurs as voltage drop at the cathode resistance W12 between the cathode of the preceding tube R1 and ground. The capacitor C1 is completely charged at the moment 21 (firing of tube R2). Its voltage is determined by the voltage drop in the cathode resistance W12. Starting at point t1, the capacitor C1 begins to discharge in accordance with the dot-dash curve.

The tube voltage Ur prevailing between plate and cathode of tube R1 is now determined by the difference of the plate voltage Ua and the cathode voltage Ukl, that is,

Ur=UaUk1. A correspondingly effected subtraction of the curves shown in Fig. 2a gives the curve shown in Fig. 212. From this curve it can be seen that at the moment t1 the tube voltage Ur changes to negative value and thereupon again tends toward the value originally prevailing on the plates, corresponding to the charging or discharging of capacitors C2 and C1. The time interval necessary for the de-ionization is designated te. As can be seen, the tube voltage Ur does not yet reach the firing potention Uz during this period of time. Thus the tube R1 is extinguished. I

The reversal of the tube voltage Ur which can be noted from Fig. 2b is avoided by the rectifiers G1 to G6 provided in the circuit shown in Fig. l. The rectifiers G1 to G3 lying in parallel to the tubes short-circuit all voltages which have reverse polarity as compared with the operating voltage. When the tube is burning they are accordingly locked so that in this operating condition they do not influence the function of the circuit. The action of these rectifiers is shown in the diagram given in Fig. 3 which reproduces the course of the tube voltage Ur prevailing between plate and cathode of the tubes. As can be seen, the curve first of all follows the corresponding curve in Fig. 2b until the voltage U=0. Here the action of the rectifiers G1 to G3 sets in, which prevent a further displacement of the tube voltage Ur toward negative values. In order that the capacitors C1 to C3 connected in parallel to the cathode resistances cannot discharge suddenly over rectifiers G1 to G3, there are provided the rectifiers G4 to G6 which in each case lie in series to the plate-cathode path of the tubes. Such a discharging of the capacitors C1 to C3 must be prevented in order to lower the tube voltage Ur of the tube to be extinguished far below the operating voltage for a .sufiicient period of time, namely at least for the period of de-ionization. Otherwise the tube voltage Ur would too rapidly again reach values above the operating voltage so that the tube to be extinguished could retain its burning condition due to de-ionization not yet having been completely effected. The polarity of rectifiers G4 to G6 is accordingly so selected that they block a current in opposite direction to the plate current, that is, a discharge current of the capacitors C1 to C3.

It has been found that with such a connection of rectifiers which prevent the aforementioned voltage reversal, the life of gaseous discharge tubes can be substantially increased. This is of decisive importance, particularly for electronic transmission devices in which there are used counting circuits operating in accordance with the principle mentioned at the beginning hereof, since such counting circuits belong in general to central members the failure of which can lead to extensive disturbances if not to the placing out of operation of the transmission device in question.

For reasons of economy, it will be attempted to use rectifiers which are as small as possible. This can have the result that their forward direction resistance makes itself noticeable, which can be of importance particularly in the case of the parallel connected rectifiers G1 to G3. In this case, during the period of time in which these rectifiers are acted on in forward direction, a certain residual voltage will remain on them which, due to the aforedescribed voltage conditions in the time interval in question would be of opposite polarity to the operating voltage. The higher the forward direction resistance, the more unpleasantly the residual voltage remaining as a result thereof can make itself felt. In order to remedy this, there may be provided in series with each of the rectifiers G1 to G3 a separate RC-member which consists' of the parallel connection of a resistance and a rectifier. Y

A corresponding circuit is shown in Fig. 4 in which, for reasons of simplicity, only one stage of a counting circuit has been shown. The construction of this stage may correspond to that of any of the stages of the circuit shown in Fig. 1. While the tube is operating, the capaci tor C4 is charged to a given voltage. This voltage is determined by the voltage divider comprising the resistor W15 and the rectifier G1. The rectifier G1 is operated upon in reverse direction during this period of time. If, therefore, for instance the resistor W15 has the value of the reverse direction resistance of the rectifier G1, the capacitor becomes charged to one-half the operating voltage. At the moment of the firing of the next tube, this capacitor voltage must then be present on the tube to be extinguished with the same polarity as the operating voltage since the rectifier G1 has now become conductive. Since, however, as already stated, the capacitor voltage is only equal to one-half the operating voltage, the tube begins to become de-ionized. By a suitable dimensioning of the RC-member, the result can be obtained that a voltage supplied by the capacitor C4 remains on the corresponding tube until, as a consequence of the change of the charge of the capacitors connected in parallel to the cathodes, the cathode potential of the tube to be extinguished has dropped to such an extent and the anode potential, due to the firing of the next tube, has risen to such an extent that the region of possible voltage reversal is already exceeded. It has been found that a dimensioning of the RC-member in accordance with which one-half the operating voltage remains on the tube to be extinguished upon the firing of the next tube has a very favorable efifect for the life of the tubes.

Another construction of the voltage divider contemplated in the circuit of the invention is shown in Fig.5. In this case the voltage divider comprises a rectifier G4 or G5 or G6 which, as in the previously discussed example, when the tube is lit, is acted upon by the tube current in forward direction, and of a resistor W15 or W16 or W17 respectively which is of low ohmic value as compared with the reverse direction resistor of the rectifier and accordingly takes away the voltage which effects the displacement of the potential. Fig. 5 is also operative as a counting circuit. This counting circuit corresponds in its functioning entirely to the counting circuit shown in Fig. 1. Accordingly, the same references as in Fig. 1

have been used for corresponding structural parts. The purpose of the voltage divider in this case is to decrease the voltage at the cathode upon the beginning of the extinguishing operation at least to such an extent that the potential occurring at the plates upon the firing of the next tube is still higher than the cathode potential of the tube to be extinguished. A reversal of voltage at the tube to be extinguished is then no longer possible. With.

the commencement of the extinguishing process, the rectifier G4 or G5 or G6 respectively is acted on in reverse direction since the corresponding capacitor C1. or C2 or C3 respectively strives to discharge itself on the one hand over its parallel resistor and on the other hand over the connected voltage divider. The capacitor voltage drops in this connection at the voltage divider, the greatest part of the voltage being on the rectifier since the corresponding resistor W15, W16 or W17 respectively is of low ohmic value as compared with the reverse direction resistor of the rectifier. In this case also, the voltage divider can be so dimensioned that upon the commencement of the extinguishing operation, the voltage on the tube has come close to the value of half the operating potential. The building-up operations which take place in a circuit such as shown in Fig. 5 are indicated in Fig. 6. The curves of this figure correspond essentially to those of Fig. 2a. Up to the moment :1, namely the beginning of the extinguishing operation, the dot-dash curve shows the voltage Ukl at the cathode of the corresponding tube and the voltage Uc at the corresponding capacitor connected in series with the cathode, since in burning condition the rectifier present between the cathode and the capacitor is open and accordingly for all practical purposes is not present. From the time t1 on, as already stated, the rectifier is blocked, and the capacitor begins to discharge. Its voltage is shown by the dot-dash curve marked Uc. This voltage curve corresponds completely to that shown in Fig. 2a. The voltage at the cathode Ukl is reduced by the voltage divider ratio starting at the time 11. The dot-dash curve Ukl shows the corresponding voltage course. As can be seen, the potential of the cathode is substantially lower than the potential on the corresponding capacitor. In the embodiments selected, the cathode of the corresponding tube takes on at the time t1 a potential which corresponds approximately to one-half the operating potential. Accordingly there also remains for the corresponding tube a voltage amounting to one-half the operating voltage, since at the time t1 the potential at the plates will drop to just the operating voltage.

Changes may be made within the scope and spirit of the appended claims.

I claim:

1. A circuit arrangement for reducing the wear of gaseous discharge tubes incident to extinguishing as a result of coincident potential displacement to opposite values at the plate-cathode path, comprising a gaseous discharge tube having a plurality of operating electrodes.

including an anode element and a cathode element between which current flows during conductance of said tube, a circuit including a resistor and capacitor in parallel having a common terminal connected to said cathode element, a tapped voltage divider having an intermediate point to which one of said elements is operatively connected and from which its operating potential is derived, one leg of said voltage divider including rectifier means operative to pass current during tube conductance and restrict current in the opposite direction, another leg of said voltage divider including an operative resistance means of such value that during the extinguishing of said tube, part of the voltage causing potential displacement will decay at said rectifier means, one of said means being connected in parallel with said anode and cathode elements.

2. A circuit arrangement according to claim 1, wherein said other leg of said voltage divider, comprises further rectifier means connected in parallel with said anode and cathode elements, the polarity of said further rectifier means being such as to block passage of current when the tube is operating.

3. A circuit arrangement according to claim 2, comprising an RC-element including a resistor and a capacitor, and means for connecting said element in series with said further rectifier means.

4. A circuit arrangement according to claim 2, comprising an RC-element including a resistor and capacitor, and means for connecting said element in series with said further rectifier means, wherein the components of said RC-element having such values that the voltage on the capacitor corresponds at the beginning of the extinguishing operation approximately to one'half of the firing voltage.

References Cited in the file of this patent UNITED STATES PATENTS 1,610,837 White Dec. 14, 1926 2,062,960 Barclay Dec. 1, 1936 2,469,913 Basham May 10, 1949 2,628,331 Rockafellow Feb. 10, 1953 2,697,802 Decker Dec. 21, 1954

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