US2251568A - Gaseous relay tube - Google Patents

Description

A1g-5, 1941- D. s. GUSTIN ErAL 2,251,568

X 3 'I GASEOUS RELAY TUBE X Filed Feb. 25, 1939 ,K

' BY Mum ATTORNEY Patented ug. 5, 1941 UNITED STATES PATENT OFFICE GASEOUS RELAY TUBE Daniel S. Gustin and Robert Fred Hays, Jr., Bloomfield, N. J., assignors to Westinghouse Electric &

Manufacturing Company,

East

6 Claims.

The present invention relates to a gaseous electric discharge device and more particularly to what may be termed a no-power-loss relay for making and breaking an electric circuit.

A device of this type has many uses where it is desired to momentarily close a control circuit for initiating the operation of numerous electrically operated apparatus. One adaptation of a device forming the subject-matter of the present invention is in the starting of a gaseous discharge lamp as shown in the copending application of E. C. Dench, Serial No. 242,927, filed November 29, 1938, and assigned to the same assignee as the present invention. As shown in such copending application, a discharge lamp is provided with a pair of thermionic cathodes which are connected in series to a suitable source of electrical energy for the purpose of heating the electrodes to an electron emitting temperature and initiating a discharge therebetween, after which the series circuit is interrupted by a relay device which thereafter consumes no power.

In a discharge lamp circuit, as well as many other circuits, it is highly desirable that the relay which operates to open and close the circuit consume no power so that the efficiency of the entire system, whether supplying a lamp or other load, may be enhanced. Moreover, the relay must operate with fidelity and be positive in its function, otherwise the apparatus controlled by the relay tube may be materially damaged.

Although the relay tube as shown in the above mentioned copending application possesses such requisites, the fact that a glow discharge occurs has certain disadvantages in increasing the time required to cause operation of the device, as well as the fact that, since the current drawn is proportional to the area of the active surface of the cathode, the greater the current the lower the transient voltage available for the circuit for the controlled element.

Itis accordingly an object of the present invention to provide a gaseous electric discharge relay device wherein the discharge between the electrodes is an arc as distinguished from a glow discharge, and the device consumes no power from the circuit which it controls after initiation of its operation.

Another object of the present invention is the provision of a gaseous electric discharge relay tube wherein the current consumption thereof is maintained at a minimum during initiation of its operation, thus increasing the transient voltage of the circuit in which such device is incorporated,

and wherein such device consumes no power from the circuit after initiation of its operation.

A further object of the present invention is the provision of a gaseous electric discharge relay device wherein the electrodes are provided with portions permitting passage of the electrodes with respect to each other to prevent distortion during fabrication so that the spacing between the electrodes is not disturbed and remains fixed upon completion of the device.

Still further objects of the present invention will become obvious to those skilled in the art by reference to the accompanying drawing wherein:

Fig. 1 is a schematic illustration of a circuit for a discharge lamp employing a gaseous electric discharge relay device constructed in accordance with the present invention;

Fig. 2 is an elevational view of the gaseous electric discharge relay device of the present invention showing one side of the electrodes;

Fig. 3 is an elevational view in cross-section and looking in the direction indicated by the arrows III--III of Fig. 2 and showing the edge view of the electrodes;

Fig. 4 is a cross-sectional View on a slightly enlarged scale and taken on the line IV-IV of Fig. 2, and

Fig. 5 is a cross-sectional view taken on the line V-V of Fig. 2.

Referring now to the drawing in detail, a circuit is shown in Fig. 1 for starting a gaseous discharge lamp and illustrates one specic use for which the gaseous electric discharge relay device of the present invention may be employed. The gaseous discharge lamp 5 as shown in Fig. l is provided with oppositely disposed lamentary electrodes 6 and 'l of a refractory metal, such as tungsten or the like, which may be in the form of a coiled coil coated with an electron emissive material, such as an oxide of barium, strontium, or the like, to provide a copious flow of electrons when heated.

After evacuation, the lamp is filled with a rare gas at a few millimeters pressure to facilitate starting, to which is added a few drops of mercury, as is well known in the art. One terminal of the electrode 6 is connected by a conductor 8 through an inductance element 9 to one side of the source of supply of the customary domestic potential of 115 or 230 volts. Likewise, one terminal of the electrode 'I is connected by a conductor l0 and switch I2 to the opposite side of the domestic source of supply.

The remaining terminal of each electrode is connected together through the medium of a gaseous electric discharge relay device I3 so that upon closure of the relay contacts, the electrodes 6 and 'I are initially in series with each other and the source of supply, thus heating the electrodes to an electron emitting temperature. When the temperature of the electrodes reaches a value suflicient to cause a copious flow of electrons, the relay device I3 automatically operates to interrupt the series heating circuit for the electrodes. The attendant voltage increase, upon operation of the device I3, causes -a discharge between the electrodes 6 and 'I with the result that this discharge carries the current, and the voltage -across the electrodes of the device I3 is too low to start a discharge therebetween until extinguishment of the discharge between the electrodes 6 and 1.

Except for the construction of the gaseous electric relay device I3, the circuit of Fig. 1 in no way differs from that shown and described in the above identified copending application. Since the device of the present invention may be em- ;--`.cyed in conjunction with any circuit where a sequential operation of various elements of a given system is desired, Fig. 1 serves merely as illustrative, and further description thereof is believed unnecessary.

Referring now more particularly to Fig. 2, the gaseous electric relay device I3 as shown comprises an evacuated envelope I4 which, after evacuation, is filled with an ionizable medium, such as neon or the like, at a pressure of approximately 20 to 40 mm. and provided with a reentrant press portion I5. A suitable base, such for example as a threaded base I8 of the type customarily employed with incandescent lamps, is secured to the envelope I4, and a pair of leadingin and supporting conductors I l and I8 extend from the base I8 to the interior of the envelope I4, being sealed to the reentrant press portion I5.

The leading-in and supporting conductor Il has rigidly secured to the end thereof, such as by welding or the like, a bimetallic electrode 20, and in a similar manner the leading-in conductor I8 has a bimetallic electrode 22 secured to its end interiorly of the envelope. As can be noted more particularly from Figs. 2' and 3, the bimetallic electrode 2D has welded or otherwise secured thereto a wire or rod of refractory metal, such as tungsten 23, extending substantially transversely of the longitudinal axis of the envelope in the direction of the adjacent electrode 22 to form a contact terminal. The bimetallic electrode 22 likewise is provided with a similarly attached refractory metal contact terminal in the form of a loop 24 and these terminals 23 and 24 are adapted to establish contact with each other, as hereinafter mentioned.

The electrodes 20 and 22, which are of identical construction except for the refractory metal contacts as above mentioned, comprise a bimetallic strip 25, the flat surface of which is contacted for a portion of its length by a magnesium ribbon or the like 26 which gives off a copious flow of electrons. The magnesium ribbon 26 is held in place in any suitable manner, such as by crimping an end of the bimetallic element upon itself with the magnesium ribbon disposed therebetween, as can be more readily seen in Fig. 4.

Upon the application of a suitable potential to the electrodes 20 and 22 and depending upon the pressure of the gaseous medium, a glow discharge occurs due to the emission `of electrons from the electrode 20 when functioning as cathode. These electrons cause ionization of the gaseous medium, with the result that a glow discharge occurs between the electrode 2B and the electrode 22, functioning as anode during one half wave of the alternating current cycle. rIhis ensuing discharge accordingly heats the bimetallic electrode or cathode 2S, which at the moment functions as cathode, causing deflection of the latter until the refractory metal contact terminal 23 carried by one end thereof engages the looped contact terminal 24 of the electrode 22, thus short-circuiting the electrodes and extinguishing the discharge.

Initially, the flow of current in the heating circuit for the electrodes 6 and I is through the glow relay tube I3, due to the ensuing discharge. Upon extinguishment of the glow discharge, however, by short-circuiting of the electrodes, current will continue to ow in the circuit due to the positive engagement of the contact terminals 23 and 24 of the respective electrodes 20 and 2'2. Extinguishment of the discharge by short-circuiting of the bimetallic electrodes permits cooling and opposite deflection to normal position of each electrode, thus interrupting the positive engagement of their respective terminals and conditioning the gaseous electric relay device I3 for repetition of its cycle of operation.

In a circuit such as shown in Fig. l a discharge does not again occur in the gaseous electric relay device I3, since current in the circuit flows by virtue of the resulting discharge between the electrodes 6 and 'I of the lamp 5, and in a similar circuit wherein some load other than a discharge lamp is energized, the same electrical phenomena will follow. If the current flow in the circuit is not by-passed or shunted in a manner similar to that just mentioned with respect to the circuit of Fig. 1, such for example as where the gaseous electric relay device I 3 is employed to periodically energize a load, a discharge in the relay device I 3 will ensue following disengagement of the electrodes until the bimetallic electrode is again heated to cause engagement of the electrode terminals, which cycle of operation continues so long as a potential is applied to the electrodes 20 and 25.

In a gaseous electric relay device as above described there is naturally a time lapse before sufficient heat is generated by the resulting glow discharge to cause deflection and closure of the electrode contacts. In order to decrease the time required to heat the bimetallic electrodes with resulting closure of their respective contact terminals, the magnesium ribbon 25 is provided with a small crater 27 centrally located which concentrates a large portion of the discharge within the crater, causing the generation of a comparatively great amount of heat on the surface of the bimetallic electrodes 20 and 22, followed by rapid deflection thereof and closure of the respective contact terminals.

Moreover, the time period during which the contact terminals remain closed, to thus supply full current to the load, can be controlled by the location of the crater 21 and the closer the latter to the leading-in conductors, the less the time period during which the contact terminals remain closed. This time delay is due to the time necessary for the propagation of heat from the crater 21 through the bimetallic electrodes 2D and 22 andl because of the cooling eifect of the leading-in conductors I1 and I8.

Also, when the glow discharge is established, a current is drawn by the gaseous electric relay device I3 which is proportional to the area of the active cathode surface with the result that the greater the value of this current, the less the transient voltage available for starting the controlled element or lamp as shown in Fig. 1. To reduce this current at the instant of initiation of the discharge between electrodes and 22, the active portion of the electrode surface comprising the magnesium strip 26 is reduced so that its area approximates from One-half to twothirds the area of its respective adjacent bimetallic electrode. Reduction of this area thus increases the transient voltage available for initiating operation of the controlled element and, owing to the provision of the crater 21, rapid heating of the electrode with deflection thereof occurs with great rapidity, as above noted.

Although the gaseous electric relay device I3 has thus far been described as a glow discharge device, rapidity of the heating of the bimetallic electrodes can be still further increased by causing the initiation of an arc discharge as distinguished from a glow discharge. Accordingly, by using a proper emission material, such for example as a magnesium-barium alloy, instead of a magnesium ribbon, and by proper selection of the gaseous medium, such as a mixture of 99.5% neon and 0.5% argon, and employing a pressure of approximately 40 mm., an arc discharge will occur upon the application of a potential to the electrodes 2U and 22 which increases the rapidity of heating and closure of the contact terminals over that of a glow discharge so that the electrode terminals will close in approximately onetenth of a second.

Moreover, by causing an arc discharge as distinguished from a glow discharge, sufficient current can be passed by the arc during the interim of one-tenth of a second prior to actual closure of the electrode contacts as to produce a considerable current ow in the controlled element. Thus in the case of the lamp 5 of Fig. 1, a considerable amount of heat is produced at the electrodes 6 and `I even prior to closure of the electrode terminals of the gaseous electric relay device I3, resulting in a still further increase in the rapidity with which an arc can be initiated between the electrodes 6 and I of the lamp 5.

During fabrication of the gasepus electric relay device I3, it is naturally necessary to carefully set the contact clearance between the terminals of the bimetallic electrodes 2D and 22 since such spacing greatly affects the time period required for closure thereof upon heating of the electrodes. Consequently, such contact clearance having once been set, it must be carefully preserved during further steps in the fabrication of the device which, as is well known in the art, necessitates external heating for purposes of exhausting of the envelope.

Inasmuch as the bimetallic electrodes naturally tend to become distorted during external heating and exhaust, allowance in contact spacing must be made in order that the nal spacing will be that desired, which is exceedingly diicult. By providing the bimetallic electrodes 20 and 22 with the contact terminals having the above noted conguration, the contact terminal 23 contacts the looped terminals 24, as it does in normal operation, and as the temperature of the electrodes is further increased during exhaust heating, which incidentally is to a much higher temperature than that resulting during operation, the contact terminal 23 will ride over the looped terminal 24, and upon cooling it will return to its original position, thus eliminating any tendency toward permanent deformation which would otherwise alter the contact clearance therebetween. Thus, upon complete fabrication of the gaseous electric relay device I3, the spacing between the respective electrode contacts remains at that originally set for desired operation.

It will thus be apparent to those skilled in the art that a gaseous electric relay device is herein provided for controlling a circuit wherein the electrodes of the device are heated by either an arc or glow discharge so as to establish contact therebetween to short-circuit the discharge and extinguish the same. Moreover, by the provision of a small crater in the electron emissive material of the electrodes and making the area thereof less than that of the bimetallic electrode surface, not only are the electrodes heated with great rapidity, but the transient voltage is substantially increased by reducing the current drawn by the device. Also by providing the electrcdes with contact terminals of a conguration which will enable them to pass each other during exhaust heating, permanent deformation is pr'e-` cluded and the spacing of the contact terminals remains deiinitely set for desired operation.

Although one specific embodiment of the present invention has been shown and described, it is to be understood that other modications of the same may be made without departing from the spirit and' scope of the appended claims.

We claim:

1. A gaseous electric relay device for completing an electric circuit comprising an envelope provided with an ionizable medium therein and a pair of electrodes adapted to be included in said circuit, one of which is a bimetallic electrode, an electron emissive material carried by said bimetallic electrode adapted to emit a copious ow of electrons, said electrodes being operable to initiate a glow discharge therebetween upon the application of a suitable potential thereto, and means on the surface of said electron emissive material for concentrating the discharge thereat to cause rapid heating of said bimetallic electrode with attendant deflection thereof into contact with the other of said electrodes to complete said electric circuit and to short-circuit said electrodes and extinguish said discharge.

2. A gaseous electric relay device for completing an electric circuit comprising an envelope provided with an ionizable medium therein and a pair of electrodes adapted to be included in said circuit one of which is a bimetallic electrode, an electron emissive material in Contact with the surface of said bimetallic electrode adapted to emit a copious ow of electrons, said electrodes being operable to initiate a glow discharge therebetween upon the application of a suitable potential thereto, and a crater in the surface of said electron emissive material for concentrating the discharge therein to cause rapid heating of the adjacent bimetallic electrode with attendant deflection thereof into contact with the other of said electrodes to complete said electric circuit and to short-circuit said electrodes and extinguish said discharge.

3. A gaseous electric relay device for completing an electric circuit comprising an envelope provided with an ionizable medium therein and a pair of electrodes adapted to be included in said circuit, one of which is a bimetallic electrode, an electron emissive material in contact with the surface of said bimetallic electrode adapted to emit a copious flow of electrons, the surface area of said electron emissive material being less than the area of the adjacent surface of said bimetallic electrode to increase the transient voltage passed by said device by reducing the current drawn thereby during initiation of its operation, said electrodes being operable to initiate a glow discharge therebetween upon the application of a suitable potential thereto, and a crater in the surface of said electron emissive material for concentrating the discharge therein to cause rapid heating of the adjacent bimetallic electrode with attendant deflection thereof into contact with the other of said electrodes to complete said electric circuit and to short-circuit said electrodes and extinguish said discharge.

4. A gaseous electric relay device for completing an electric circuit comprising an envelope, a gaseous medium therein including approximately 99.5% neon and 0.5% argon at a pressure of approximately 40 mm., a pair of electrodes adapted to be included in said circuit, one of which is a bimetallic electrode, an electron emissive material contacting the surface of said bimetallic electrode and adapted to emit a copious flow of electrons, said electrodes being operable to initiate a glow discharge therebetween upon ionization of the gaseous medium therein when a suitable potential is applied to said electrodes, and a crater in the surface of said electron emissive material for concentrating the discharge therein to cause rapid heating of the juxtapositioned bimetallic electrode with attendant deiiection thereof into contact with the other of said electrodes to complete said electric circuit and to short-circuit said electrodes and extinguish the discharge.

5. A gaseous electric relay device for completing an electric circuit comprising an envelope provided with an ionizable medium therein and a pair of electrodes adapted to be included in said circuit, one of which is a bimetallic electrode, an electron emissive material carried by said bimetallic electrode adapted to emit a copious flow of electrons, said electrodes being operable to initiate a glow discharge therebetween upon the application of a suitable potential thereto to cause heating of said bimetallic electrode with attendant deiiection thereof, contact terminals carried by said electrodes engageable with each other upon deiiection of said bimetallic electrode to complete said electric circuit and to shortcircuit said electrodes and extinguish said discharge, and one of said contact terminals having a curved surface to cause the other of said contact terminals to ride thereover to the opposite side upon deflection of said bimetallic electrode during exhaust heating to a temperature higher than normal operation to prevent permanent deformation of said electrodes with a variation in the spacing between said contact terminals.

6. A gaseous electric relay device for completing an electric circuit comprising an envelope provided with an ionizable medium therein and a pair of .electrodes adapted to be included in said circuit, one of which is a bimetallic electrode, an electron emissive material carried by said bimetallic electrode adapted to emit a copious ow of electrons, said electrodes being operable to initiate a glow discharge therebetween upon the application of a suitable potential thereto to cause heating of said bimetallic electrode with attendant deiiection thereof, and contact terminals carried by said electrodes adapted to engage each other upon deflection of said bimetallic electrode during operation to complete said electric circuit and extinguish said discharge, and one of said contact terminals being in the form of a loop to cause the other of said contact terminals to ride thereover to the opposite side of said loop upon heating to a temperature higher than normal operation on exhaust heating during fabrication of said device to prevent permanent deformation of said electrodes with a variation in the spacing between said electrode terminals.

DANIEL S. GUSTIN. ROBERT FRED HAYS, JR.

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