US2236039A - Starting and operating means for gaseous discharge devices - Google Patents

Description

J. G. SOLA March 25, 1941.

STARTING AND OPERATING MEANS FOR GASEQUS DISCHARGE DEVICES Filed Jan. 15, 1940 Patented -Mar. 25, 1941 UNITED STATES STARTING AND OPERATING MEANS FOR- GASEOUS DISCHARGE DEVICES Joseph G. Sola, Oak Park, Ill.

Application January 15, 1940, Serial No, 313,885

21 Claims.

My invention relates to electric gaseous discharge devices and in particular to an improved arrangement or system by means of which an electric gaseous discharge device may be started and operated satisfactorily.

One of the objects of my invention is to provide an improved arrangement of this type by means of which electric current will be supplied for heating at least one and preferably both or the electrodes of an electric gaseous discharge device to a temperature at which the free electron emission therefrom will support the normal discharge current and then the heating current will be interrupted-and discontinued automatically after discharge through the device has been started.

It is another object of my invention to provide an improved arrangement of this type by means of which a voltage surge will be applied to the discharge device between its electrodes for starting the device in operation after oneand preterably both of the electrodes have been heated to a temperature at which the free electron emission therefrom will support the normal discharge current.

It is a further object of my invention to provide a novel arrangement of this type which may be operated either from a source 01 alternating current or from a source of direct current.

My invention contemplates the provision of an magnetic core and biased in normal position away from the core, and make andbreak armature controlled switch means which are in closed relation when the armature is at the limit of its movement toward the core and which are con-' nected in series with and between the electrodes; and it is a further object of my invention to provide time delay means in parallel with the coil closed by movement of the armature whereby an increasing current will flow through the coil means thus weakening the residual magnetic field holding the armature at the limit of its movement toward the core and whereby the switch means will be opened, thus discontinuing the fiow of current for heating the electrodes of the discharge device. It is contemplated that the parts of my arrangement shall be so proportioned that the switch means will be opened when the electrodes have been heated to such an extent that the free electron emission therefrom will support the normal discharge current.

It is another object of my invention to provide an arrangement of this type in which the time delay means and the electromagnet with its coil means, armature, and switch means. form a unit which may be readily connected in or disconnected. from the heating circuit of any standard gaseous discharge tube.

It is a further object of my invention to provide an arrangement of this type which may be economically manufactured and assembled, which is positive and reliable in its action, and which with ordinary usage has a long service life.

The invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above stated objects and such other objects as will appear from the following description of certain preferred embodiments illustrated in the accompanying drawing, wherein:

Fig. l is a diagram showing an embodiment of my improved arrangement;

Fig. 2 is a diagram showing a second embodiment of my improved arrangement;

Fig. 3 is a diagram showing a third embodiment of my improved arrangement, part or the wiring-diagram being omitted for convenience of illustration; and

Fig. 4 is a magnetic hysteresis curve showing the relation between the magnetizing force and the flux density in the core bars of the electromagnets in the embodiments of my improved arrangement with the armatures of the electromagnets at the limit of their movement toward the respective core bars.

I Like characters of reference designate 'like parts in the several views.

Referring to Fig. l, the gaseous discharge tube In is provided with electrodes or cathodes II and II which are in the form of coiled filaments and which may be oxide coated for greater electron emission. The tube is filled, at least after the filaments are heated, with a gas such as neon, or a mixture of gases such as helium and neon or a source of vapor such as mercury. In starting a tube of this type it is first necessary to heat the electrodes to a temperature at which the electrons emitted therefrom are sumcient in number to support the normal discharge current between the electrodes, and then to apply a voltage surge to the tube between the electrodes for starting discharge. The voltage of the surge is greater than the normal operatingvoltage of the discharge device and may be of short duration.

Failure to heat properly the filaments in a tube of this type before initiating discharge causes the,

discharge to be confined to one spot on each electrode whereby the electrodes are injured.

Alternating current is applied to the discharge device ill for initially heatingthe filaments H and I2 and then for supporting discharge through the tube by means of supply lines i3 and I4. Supply line It is directly connected to the filament i2 at its end l2a. An inductance element or choke coil I5 is connected in the supply line I 3, the supply line |3 being connected to the filament H at its end Ila as shown.

An electromagnetic time delay switch or relay, indicated generally at I6, is connected by means of leads l1 and I8 with the ends Nb and |2b of the filaments I and I2, respectively and through the electrodes H and I2 with the supply lines l3 and M. The time delay switch comprises a magnetic core bar |9,, coil means in the form of a winding 20 on the core bar, an armature 2| carrying a contact 22, a stationary contact 23, a resistor 24, and a condenser 25. The core bar I9 is preferably of soft steel and'unlaminated or solid. The armature 2| is pivotally mounted on the core bar at 2m and is adapted to be drawn to the core bar by an electric current flowing in the winding 20. The armature s biased in its upper position by a spring 26 which is attached to the core bar and armature as shown. A holding member or stop 21 limits upward movement of the armature. The contact 22 is attached to the armature 2| by means of a flexible arm 28. The stationary contact 23 is supported by a flexible arm 29 fixed relative to the core bar by an insulator member 30. The arrangement is such that when the armature 2| is drawn toward and against the core bar on the flow of current in the winding 20, the contacts 22 and 23 come tightly into contact due to the action of the flexible arms 28 and 29, which are bent slightly apart.

The resistor 24 is of a material such as nickel which has a resistance that increases substantially with the temperature of the material and that is much less than the resistance or the winding 20. The resistor 24 is connected with the lead l8, and with the contact 23 by means of the arm 29 as shown. The winding 20 at one end is connected with the line i8 and at the other end is grounded to the core bar IS. The condenser 25 is also connected with the line l8 and grounded to the core bar. The resistor 24 and the make and break switch means comprising the contacts 22 and 23 are connected in series and form an electrical path which is connected in parallel with the winding 20 and in parallel with the condenser 25, as is shown. At the frequency 01' the alternating current used in the operation of the arrangement, the impedance of the winding 20 is greater than the impedance oi the choke coil I5. The condenser 25 is small and its impedance is so large that it reduces but little the impedance of the relay, with the contacts 22 and 23 open, relative to the impedance of the parallel winding 20 taken alone.

When a voltage is applied between the supply lines I3 and hi, it divides into two principal parts, namely the voltage across the choke coil l5 and the voltage across the time delay relay between the leads I! and I8. Since the winding 20 has a higher impedance than the choke coil l5 and since the condenser 25 is small, most of the voltage applied between the leads l2 and I4 is present across the relay. This voltage is slimaasaoao cient to produce such a current in the winding 2| as to cause the armature 2| to be drawn to the core bar I8 at a high current pl int in probably the flrst current cycle, after the application of voltage between the lines I3 and I4. When the armature moves to the corebar from its normally raised position, the contacts 22 and 23 are brought together from normally open relation thus allowing current for heating the electrodes II and I2 to flow in the lead I! and through the choke coil l5, through the electrode II, the lead I], the armature 2|, the arm 28, the contacts 22 and 23, the arm 29, the resistance 24, the lead la, the electrode l2, and through the lead |4. Since the winding 20 and condenser 25 have high impedances, a negligible current flows through these members after the switch means has been closed. Since the contacts 22 and 23 have been closed at or near a high current point in the current cycle at which the force tending to pull the armature toward the core bar is greatest there is a residual magnetic flux in the core bar l9, and this acts to keep the armature drawn toward the core bar with the contacts 22 and 23 in close relation.

In Fig. 4, H represents the magnetizing force in the core her due to the winding 20. This magnetizing force varies with the value of the current flowing through the winding. B represents the .flux density in the core bar resulting from the magnetizing force. The force tending to pull the armature toward the core bar varies with the flux density. At the high value 01 current in the current cycle flowing through the winding 21. the magnitude of ilux density in the core bar is represented by a as shown on the curve in the figure. This is the value of flux density at which the armature is drawn toward the core bar, and the magnetizing force at this flux density is at some value higher than 12. This value b is the value of the magnetizing force which would produce the flux density a. in the core bar with the armature at the limit or its movement toward the core bar. Upon the armature being drawn down and closing the switch contacts 22 and 23 the value of the current through the winding 20 drops to a negligible value, approximately zero, as described above. Thereupon the core bar loses part of its magnetism, the flux density in the core bar dropping from the value a to the value c. The value 0 represents the residual magnetism in the core bar with the armature drawn down against the core bar, the residual magnetism being that magnetism remaining in the core bar when the magnetizing force is substantially zero. This residual magnetism is suflicient to hold the armature drawn against the core bar.

The current for heating flows through the electrodes II and I2 and through the resistor 24 and those elements simultaneously and gradually become heated. The resistor upon its increase in temperature increases correspondingly in sistance thereby causing an increase in the current flowing through the parallel winding 20. When the electrodes of the discharge device are sufficiently heated that the free electron emission thereiromwill support the normal discharge current through the device the resistance 01' resistor 24 has become so great that a current of sufllcient value flows through the winding 20 to demagnetize the core bar thereby releasing the armature which causes a. separation 01' the contacts 22 and 22 thus cutting oil! the heating current. The resistor 24 thus acts as a time delay means. The time delay in any particular embodiment of my improved arrangement may be made greater by providing a resistor which heats up at a slower rate or one which upon heating up does not gain in resistance to a great extent with each degree rise of temperature.

In general a small alternating current through .the winding 20 acts to reduce the residual magnetism in the core bar fromthe point to some lower value. For example. a small alternating current which starts at zero and which causes the magnetizing force H in the core bar l9 to change in value from o to d and thereafter to vary between d and e will cause the magnetic flux density in the core bar to decrease along the main hysteresis curve from the point 0 to the point i and thereafter to vary along the small hysteresis loop g between the points I and I. As the magnetizing force H varies from d to e the instantaneous values of the magnetic flux density will be as indicated on the lower part of the loop 9, and as the magnetizing force varies from e to d the magnetic flux density is as indicated on the upper part of the loop g. It will be noted that the net effect of passing the small alternating current through the winding 28 is to lower the magnetic flux density B from its original residual value c to an average which is approximately midway between the low point I and the high point J" of the small hysteresis loop The effect would be the same no matter at what point in its cycle the small alternating current was started.

The initial current which flows through the winding 20 when the switch contacts 22--23 are closed is very small and produces only a small variation of magnetizing force H in the core bar I9, a variation much less than is indicated by the points d and e. This initial current has a small hysteresis loop indicating the instantaneous values of B, which is similar to the loop g but is much smaller than the loop 9, and the average value of B on this small loop is only slightly below the point 0. Each succeeding cycle of alternating current is of larger amplitude ceding cycle and which has a lower average value than the loop of the preceding cycle. After a plurality of successive cycles of alternating current have passed through the winding 20 and a corresponding length of time has elapsed, the magnetizing force H has increased and varies between d and e and the instantaneous values of the flux density B in the core bar I9 is represented by the loop g. After a further length of time has elapsed and a corresponding number of cycles of gradually increasing alternating current have passed through the winding 20, whereby H varies between i and a, the small hysteresis loop indicating the instantaneous values of B (similar to the loop 9) touches the main hystersis curve at the point h; and said small loop, corresponding to the magnetizing force varying between i and j, is larger than the loop g and has a lower average value of 13 than has the loop 9. At this decreased average value of B the force which varies with B and which has been holding the armature 2| down against the core bar I9 is no longer strong enough to hold the armature down, and the armature moves upward breaking the contacts 22-23.

Upon the opening of the switch contacts 22 and 23, the current for heating the electrodes passing through the choke coil I is very suddenly decreased to a value of approximately zero as described above, and this causes a sudden collapse of the magnetic flux in the choke coil. This sudden flux collapse causes a high voltage surge to be generated across the choke coil. This voltage surge adds to the voltage applied across lines i3 and H and the resultant voltage, applied across the electrodes II and I2, causes discharge to commence through the tube; The discharge current flows through the supply lines l3 and i4 and the inductance IS. The voltage drop in the inductance is such that the voltage across the tube and across the relay is materially less than the line voltage between lines l3 and 14. When the tube is thus operating the choke coil l5 acts as a ballast inductance to limit current flow through the tube.

The electromagnetic switch is so constructed that the armature will be drawn down only at or above a certain .voltage, let us say 121 for example. The discharge tube arrangement is such that when the supply voltage is first applied to the supply lines l3 and I, the voltage across the switch between the leads I1 and I8, 122 for example, is greater than the voltage vi. The voltage between leads I! and I8 when the tube is in operation, 123101 example, due to the voltage drop in the choke coil l5 carrying the tube operating current, is less than 01. The armature 2|, therefore, is not drawn down toward the core bar when the tube is in operation.

The condenser 25 is connected across or in parallel with the switch means comprising the contacts 22 and 23, as shown, in order to reduce radio interference from the operation of the arrangement. v

When the operating current to the tube is switched off, the electromagnetic switch makes no operative stroke but remains in the same condition as when the tube is in operation. The same cycle of operations as described above is repeated when voltage is again applied to lines I3 and H.

The embodiment shown in-Fig. 2 is similar in many respects to the embodiment shown in Fig. 1. Both embodiments are adapted to be operated from a source of alternating current. The Fig. 2 embodiment diiiers from the Fig. 1 embodiment in that there is no external resistor 24 used and the contact 23 and arm 23 are connected directly with lead 3|, which lead is connected" to the electrode l2 at its end 12b. Lead 32 is connected with the electrode H at its end lib and with the armature 2| as shown. Winding 20 instead of being connected with the supply lines 13 and I4 through the electrodes I I and I2 is connected directly with they supply lines by means of leads 33 and 34 as shown. It will be noted that the winding 20 in this embodiment is connected in parallel with an 1 to flow through the parallel winding 20 which current, upon the electrodes H and I2 being heated so that they will support discharge, is of suflicient strength to destroy the residual magnetism in the core bar whereby the armature moves back to dnii'mal position and opens the contacts 22 an The Fig. 3 embodiment is like the Fig. 1 embodiment except that a second winding 35 is provided on the core bar it. The winding 35 is connected in parallel with the resistor 24 as shown and has a greater resistance than the resistor 24 but has a smaller resistance than winding 20. The winding 35 is wound on the core bar I! in such manner that when a direct current is flowing through lead I] through the winding 20 to lead l3, and also through contacts 22 and 23 and winding 35 to lead 18, winding 35 acts to magnetize the bar I! in a direction opposite to the direction in which winding 20 magnetizes the core bar. This magnetizing effect is indicated by the arrows adjacent each of the windings 20 and 35.

When the Fig. 3 embodiment is used with a source of alternating current it operates similarly to the Fig. l embodiment except that the demagnetizing eflect is a result principally of an increasing alternating current flowing through the winding 35 as the resistor 24 heats up. Little of the increasing alternating current flows, through winding 20 since winding 23 has a resistance which is considerably higher than the resistance of winding 35, As will be readily understood, however, when the switch contacts 22 and 23 are initially open, the winding 2!! acts, as in the Fig. l embodiment, to pull the armature to the core bar on the first application of voltage to the leads l3 and H.

The Fig. 3 embodiment in addition to functioning with a source oi! alternating current between the leads l3 and l 4, also operates in a similar manner with a source of direct current. On the first application of unidirectional voltage between the leads l3 and Il, most of the voltage is present across winding 20, since it has a greater resistance than the inductance element l5, and a momentary current flows through winding 20. The armature is thereby drawn down whereby the contacts 22 and 23 are closed; the flux density being a, as shown in Fig. 4, at which density the armature moves down. The winding 20 magnetizes the core bar in one direction, in the +H direction'in Fig. 4 or as indicated by the arrow adjacent the winding, and the armature is held down by the residual magnetism designated as c in Fig.4. Heating current then flows through the resistor 24, and little current flows through either winding 35 or 20 since they have higher resistances than the resistor. The flow of current in the resistor causes the resistor to become heated and an increasing current flows through winding 35, but little flows through winding 20, since winding 20 has a higher resistance than winding 35. When the current in winding 35 has increased such as to produce a magnetizing force of i on the H axis of Fig. 4 with the resultant flux of h, the armature moves upwardly and opens the contacts 22 and 23, stops the flow of heating current, and produces a voltage surge as described in connection with the other embodiments of my arrangement. The value i produced by the current through winding 35 is minus on the H axis and opposite the magnetizing iorce b corresponding to the flux density aproduced by the initial momentary current flow through winding 20 as is shown in Fig, 4 and indicated by the arrow adjacent winding 35. The arrangement as with the other embodiments is such that the armature moves upwardly when the electrodes II and I2 are sufliciently heated to support discharge. As with the use of any of the embodiments of my arrangement with a source of alternating current,

aaaaoso the armature is not drawn down while the tube I 0 is in operation.

As will be noted from Figs. 1 and 3, the relays comprising the core bars II, the windings thereon, the resistors 24 and the switch means are connected only by two leads l'l and II with the discharge tubes IO. With such an arrangement the relay may be positioned in a housing and may be provided with :two shanks which detachably fit into sockets with which a standard discharge tube mounting base may be provided. A minimum number of shanks and sockets are thus required for detachably connecting the discharge tubes and relay units together.

It is apparent that with my improved arrangements discharge through the tubes III will not start until the entire cycles of operations of the relays are completed, as the tubes require a voltage surge or higher value than that or the line voltage, applied between the electrodes for start-' ing, and thus there is no likelihood that the electrodes will be damaged due to premature discharge through the tubes.

It will be apparent from the foregoing descri tion that my improved arrangements are of simple construction and may be economically assembled and manufactured. They are positive and entirely automatic in operation. When the discharge tubes are in operation the armatures are held away from the core, and there is thus no chattering 01' the armatures. The arrangements comprise no parts which wear unduly and long service, therefore, may be expected.

I do not intend to limit the invention to the details shown and described, except only in so far as certain of the appended claims are specifically so limited, as it-wili be obvious that modifications may be made without departing from the principles of the invention.

I claim:

1. In a system 0! the class described, the combination of an electric discharge device connected between opposite supply lines of a source or current and having an electrode which is electron emitting when heated, a core bar 01- magnetic material, coil means on said core bar having connection in parallel with said discharge device to receive current from said supply lines for magnetizing said core bar, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its .movement toward the core bar by residual magnetism in the core bar, and switch means closed by movement oi! said armature toward said core bar for completing a heating circuit between said supply lines and including said electrode, the arrangement being such that while current initially flows in the heating circuit the current flow through said coil means is negligible but uponsaid electrode being heated sufliciently to support discharge current of suflicient magnitude flows through said coil means to demagnetize sufliciently said core bar thereby opening said switch means.

2. In a system of the class described, the combination of an electric discharge device connected between opposite supply lines of a source of current and having an electrode which is electron emitting when heated, a core bar of magnetic material, coil means on said core her having connection in parallel with said discharge device to receive current from said supply lines for magnetizing said core bar, an armature movable toward and from said core bar and biased away aasaose therefrom but adapted to be held at the mint of its movement toward the core bar by residual magnetism in the core bar, switch means closed by movement of said armature toward said core bar for completing a heating circuit between said supply lines and including said electrode, and an electrical impedance member in said heating circuit in parallel with said cell means which increases in impedance on the passage of heating current, the arrangement being such that while current initially flows in the heating circuit the current flow through said coil means is negligible but upon said electrode being heated sufliciently to support discharge the increased impedance of said impedance member causes current of sumcient magnitude to flow through said coil means to demagnetize sufliciently said core bar thereby opening said switch means.

3. In a system of the class described. the combination oi an electric discharge device having two electrodes connected with opposite supply lines a source 0! current and being electron emitting when heated, a core bar of magnetic material, coil means on said core bar having connection in parallel with said discharge device to receive current from said supply lines for magnetizing said core bar, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means closed by movement of said armature toward said core bar for completing a heating circuit between said supply lines and including said electrodes, the arrangement being such that while current initially flows in the heating circuit the current flow through said coil means is negligible but upon said electrodes being heated sufliciently to support discharge current of sufficient magnitude ilows through said coil means to demagnetize suiiiciently said core bar thereby opening said switch means.

4. In a system of the class described, the combination of an electric discharge device connected between opposite supply lines of a source of current and having an electrode which is electron emitting when heated, a core bar of magnetic material, coil means on said core bar having connection in parallel with said discharge device to receive current from said supply lines tor magnetizing said core bar, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means closed by movement of said armaturetoward said core bar for completing a heating circuit between said supply lines and including said electrode, and a condenser connected in parallel with said switch means, the arrangement being such that while current initially flows in the heating circuit the current flow through said coil means is negli- .glble but upon-said electrode being heated suflicientlyto support discharge current of sumcient magnitude flows through said coil means to demagnetize sufliciently said core bar thereby opening said switch means.

5. In a system 01 the class described, the combination of an electric discharge device connected between opposite supply lines of a source of current and having an electrode which is electron emitting when heated, a core bar of magnetic material, coil means on said core bar having connection in parallel" with said discharge device to receive current from said supply lines for magnetizing said core bar, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core barby residual magnetism in the core bar, switch means closed by movement oi! said armature toward said core bar for completing a heating circuit between said supply lines and including said electrode, and an inductance element in one of said supply lines, the arrangement being such that while current initiallyflows in the heating circuit the current flow through said coil means is negligible but upon said electrode being heated sufllciently to support discharge current of sumcient magnitude flows through said coil means to demagnetize sufliciently said core bar thereby opening said switch means.

6. In a system of the class described, the combination of an electric discharge device having two electrodes connected with opposite supply lines of a source of current, one of said electrodes being electron emitting when heated, a core bar of magnetic material, coil means on said core bar having connection in parallel with said discharge device to receive current from said supply lines for magnetizing said core bar, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means closed by movement of said armature toward said core bar for completing a heating circuit between said supply lines and including said electron emitting electrode, and a resistor in said heating circuit in parallel with said coil means which increases in resistance on the passage of heating current, the arrangement being such that when current initially flows in the heating circuit the current flow through said coil means is negligible but upon said electron emitting electrode being heated sufliciently to support discharge the increased resistance of said resistor causes current of suiiicient magnitude to flow through said coil means to demagnetize sufliciently said core bar thereby opening said switch means.

'7. In a system of the class described, the com bination of an electric discharge device having two electron emitting electrodes connected with opposite supply lines of a source oi. current, a core bar or magnetic material, coil means on said core bar having connection in parallel with said discharge device to receive current from said supply lines for magnetizing said core bar, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means connected in series with and between said electrodes and closed by movement of said armature toward said core bar, and a resistor in series with said switch means and in parallel with said coil means, said resistor increasing in resistance'on passage of current therethrough for heating said electrodes and causing suflicient current to flow through said coil means to demagnetize sufficiently said core bar and open said switch means when said electrodes are heated sufliciently to support discharge.

8. In a system of the class described, the combination of an electric discharge device having two electrodes connected with opposite supply lines oi. a source of current, one of said electrodes being electron emitting when heated, a core bar of magnetic material, a winding on said core bar and connected between said supply lines for magnetizing said core bar, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, and switch means closed by movement of said armature toward said core bar for completing a heating circuit between said supply lines and including said electron emitting electrode, at least a portion of said heating circuit being in parallel with said winding which circuit portion increases in resistance on the passage of current therethrough for heating said electron emitting electrode and causes suflicient current to flow through said winding to demagnetize sufllciently said core bar and open said switch means when said electron emitting electrode is heated sufficiently to sup-' port discharge.

9. In a system of the class described, the combination of an electric discharge device having two electron emitting electrodes connected withresidual magnetism in the core bar, switch means closed by movement of said armature toward said core bar for completing a heating circuit between said supply lines and including said electrodes, at least a portion of said heating circuit including said switch means being in parallel with said winding which circuit portion increases in resistance on the passage of current therethrough for heating said electron emitting electrodes and causes sufllcient current to flow through said winding to demagnetize sufllciently said core bar and open said switch means when said electrodes are heated suftlciently to support discharge.

10. In a system of the class described, the combination of an electric discharge device having two electrodes connected with opposite supply lines of a source of current, one of said electrodes being electron emitting when heated, a core bar of magnetic material, a winding on said core bar connected between said electrodes and in series with said electron emitting electrode for magnetizing said core bar, an armature movable to ward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means closed by movement of said armature toward said core bar, and an impedance element forming with said switch means an electrical path connected in parallel with said winding, said impedance element increasing in impedance on the passage of current therethrough and eventually causing suflicient current to flow through said winding to demagnetize sufliciently said core bar to release said armature.

11. In a system of the class described; the com bination of an electric discharge device having two electrodes connected with opposite supply lines of a source of current; one of said electrodes being electron emitting when heated; a core bar of magnetic material; a winding on saidcore bar connected between said electrodes by means of two leads, one to each electrode, and in series with than said winding and increasing in impedanceon the passage of current therethrough.

12. In a system of the class described, the combination of an electric discharge device-having two electron emitting electrodes connected with opposite supply lines of a source of current, a core bar of magnetic material, a winding on said core bar connected in series with and between said electrodes for magnetizing said core bar, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means closed by movement of said armature to ward said core bar, and a resistor forming with said switch means an electrical path connected in parallel with said winding, said resistor having a lower resistance than said winding and increasing in resistance on the passage of current therethrough and eventually causing sufficient current to flow through said winding to demagnetize suihciently said core bar to release said armature.

13. In a system of the class described, the combination of an electric discharge device having two electrodes connected with opposite supply lines of a source of current, one of said electrodes being electron emitting when heated, a core bar of magnetic material, a winding on said core bar connected between said supply lines, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, and switch means closed by movement of said armature toward said core bar and connected between said electrodes and in series with said electron emitting electrode, said switch means and said electron emitting electrode forming a heating circuit which is in parallel with said winding and which increases in resistance as saidelectrom emitting electrode becomes heated.

14. In a system of the class described, the combination of an electric discharge device having two electrodes connected with opposite supply lines of a source of current, one of said electrodes being electron emitting when heated, a core bar of magnetic material, a winding on said core bar connected between said-supply lines, an armature movable toward and from said core bar and biased away therefrom but adapted to be held, at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means closed by movement of said armature toward said core bar, an impedance element forming with said switch means an electrical path connected between said electrodes and in series with said electron emitting electrode, said impedance element increasing in impedance on the passage of current therethrough, and a'second winding on said core bar connected in parallel with said impedance element todemagnetize sufliciently said core bar to release said armature.

15. In a system of the class described, the comazsaoao bination of an electric discharge device havin two electron emitting electrodes connected with opposite supply lines of a source of current, a core bar of magnetic material, a winding on said core bar connected between said electrodes, an armature movable toward and from said core bar and biased away therefrom but adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means closed by movement of said armature toward said core bar, a resistor forming with said switch means an electrical path connected between and in series with said electrodes, said resistor having a lower resistance than said winding and increasing in resistance on the passage of current therethrough, and a second winding on said core bar in magnetic opposition to said first winding and connected in parallel with said rcsistor.

16. In a system of the class described, the combination of a core bar of magnetic material having a winding thereon, an armature movable toward and from said core bar and biased away therefrom but being adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means connected in parallel with said winding and adapted to be opened and closed by movement of said armature, an electric impedance member adapted to increase in impedance on passage of current therethrough and connected in parallel with said winding, and a second winding on said core bar connected in parallel with said impedance member and in magnetic opposition to said first winding.

17. In a system of the class described, the combination of a core bar of magnetic material having a winding thereon, an armature movable toward and from said core bar and biased away therefrom but being adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means adapted to be closed by movement of said armature toward said core bar, a resistor adapted to increase in resistance upon passage of electric current therethrough and connected in series with said switch means, said resistor and switch means being connected in parallel with said winding, and a second winding on said core bar of less resistance than said first winding and connected in parallel with said resistor and in magnetic opposition to said first winding,

18. In a system of the class described, the combination of a core bar 01' magnetic material having a winding thereon, an armature movable toward and from said core bar and biased away therefrom but being adapted to be held at the limit of its movement toward the core bar by residual magnetism in the core bar, switch means adapted to be closed by movement of said armature toward said core bar, a resistor connected in series with said switch means and forming with the switch means an electrical path which is connected in parallel with said winding, said resistor having a smaller resistance than said winding and being adapted on the passage of current therethrough to increase in resistancaand a second winding on said core bar connected in parallel with said resistor and'in magnetic opposition to said first winding and having a smaller resistance than said first winding.

l9. Ina system of the class described, the combination of an electric discharge device connected between opposite supply lines of a source of current and having an electrode which is electron emitting when heated, an electromagnetic device having connection with said lines and in parallel with said discharge device, switch means under the control of said electromagnetic device, means for magnetizing said device to close said switch means, and means complete a heating circuit for said electrode and for demagnetizing said device sufficiently to open said switch means and break said circuit.

20. In a system of the class described, the combination of an electric discharge device connected between opposite supply lines or a source of current and having an electrode which is electron emitting when heated, an electromagnetic device having connection with said lines and in parallel with said discharge device, switch means under the control of said electromagnetic device, means for magnetizing said device to close said switch means and complete a heating circuit for said electrode, the residual magnetism in said device acting to maintain said switch means closed, and means for reducing the residual magnetism in said device sufilciently to open said switch means and break said circuit.

21. In a system of the class described, the combination of an electric discharge device connected between opposite supply lines of a source of current and having an electrode which is electron emitting when heated, an electromagnetic device having connection with said lines and in parallel with said discharge device and including an outwardly biased armature, switch means under the control of said armature, means for magnetizing said electromagnetic device to attract said armature and close said switch means to complete a heating circuit for said electrode, and means for demagneitzing said device sufilciently to open said switch means to break said circuit.

JOSEPH G. SOLA.

CERTIFICATE OF COPREC'IION; Patent 'No. 2,236,059. March 2 19in.

5 JOSEPH G. SOLA.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follbws: Page 7', second column, line 214., claim 19, for the words "means, and means" read --means and--;-line 25, same claiin, for "electrode and" read--electrode, and meansand that the said Letters Patent should be readwith this correction therein that the. same may conform to the record of the case in the Patent Office. 4

Signed and sealed this 29th day of April, A. D. lghl.

Henry Ven Airedale, (Seal) Acting Commissioner of Patents.

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