US1971943A - Gaseous electric discharge lamp - Google Patents

Description

Aug. 28, 1934. REGER 1,971,943

GASEOUS ELECTRIC DISCHARGE LAMP Filed June 8, 1932 INVENTOR mew/22m 'c/ I ATTORNEY i so;

Patented A... 28, 1934 UNITED STATES GASEOUS ELECTRIC DISCHARGE LAMP Martin Roger, Berlin, Germany, assignor to General Electric Company, a corporation of New York Application June 8, 1932, Serial No. 616,124 In Germany June 24, 1931 4 Claims.

The present invention relates to gaseous electric discharge lamps generally and more particularly the invention relates to such devices operating on alternating current in which the light emitted by the positive column discharge in said device is controlled by operating the lamps with successive discharges of short duration and timing the duration of the successive discharges similar to the lampdescribed in co-pending application, Serial Number 463,520, filed June 24, 1930, the inventors being Clifton G. Found, Albert W. Hull and James V. Smith.

In the application referred to the gaseous electric discharge device is provided with a thermionic cathode, two anodes and grids or control electrodes surrounding said anodes and means is provided to impress on the control electrode electric charges so varying with respect to the space in the environment of the anode that a desired luminosity is obtained. This is accomplished by displacing the phase of the alternating current supplied to said control electrode with respect to the phase of the alternating current supplied to said anodes. I have discovered that a lamp operating in the above described manneris selfregulating and therefore the usual ballast resistance is not needed under certain conditions, namely, when the phase of the alternating current supplied to the control electrode is in such relation to the phase of the alternating current supplied to the anodes that current flow between the main discharge supporting electrodes of the device starts first on the descending side of each half wave of the alternating current and shortly before said wave reaches zero. The current which builds up during this short period is thus not of suflicient duration to injurethe electric discharge lamp device.

A more complete understanding of the invention may be obtained from the following description taken in combination with the accompanying drawing in which Fig. 1 comprises a plan view of a lamp embodying the invention and a diagram of electrical connections; Fig. 2 illustrates ona larger scale the anode portion of the lamp shown in Fig. 1 with part of the envelope and grid electrode shown brokenaway; and Figs. 3 and 4 are graphs showing the relation of the voltage and current of the main circuit to the voltage of the control circuit when the lamp is operated in accordance with this invention.

Referring to Fig. 1, the lamp here illustrated comprises an elongated envelope 1, consisting of a glass or the like (part being broken away to save space on the drawing), the envelope'having outwardly extending arms 2, 3. The main portion of the envelope, which is shown broken,

. ed with alkaline earth oxides but may be coated with a rare metal, or any other material of high electron emissivity. Various'other forms of ther mionic cathodes may be employed. The heater 5 is connected at one end to a leading-in conductor 6 and at the other end to the shell 4 which is in turn connected to a lead 7. These conductors 6, '7 are connected to the secondary of a heater transformer 8 whereby electric energy is furnished to maintain the cathode at an operating temperature.

The primary of the transformer 8 is connected by the conductors 9, 10 to taps on the main auto transformer 11 whereby energy is delivered both to heat the cathode and to operate the lamp as a whole as will later be described. The anodes 2, 3 consist of one or more of the following materials, graphite, nickel, iron, tungsten, or other suitable conductive material. They are connected to said auto transformer 11 by conductors 13, 14.

As best .shown in Fig. 2, the anodes are surrounded by grids 17, 18, which consist either of a relatively fine mesh wire screen, or of sheet metal provided with numerous small openings, as shown in the drawing.

These grid electrodes are connected respectively by conductors 19,20 to the secondary oi the transformer 21, the primary of which is connected by conductors 22, 23 to the alternating current supply lines 24, 25, carrying currents of suitable frequency, say 25 or 60-cycle current. Included in circuit with the conductor 23 is a capacitor 26 shunted by an adjustable resistor 2'1. By varying the resistance connected across the capacitor the phase of the alternating current furnished to the primary of the transformer 21 may be shifted at will with respect to the phase of the alternating current which is supplied to the main electrodes of the lamp by the anode conductors 13, 14 and the cathode conductor 28.

Included in the cathode conductor 28 is a handoperated switch 29 and a mercury switch 30 which is tilted by a magnet having a coil 31, the armature 32 of said magnet is connected by suitable lever. 33 to the mercury switch 30. A circuit through the mercury switch from the main transformer 11 is completed by the conductor 34 containing a resistance 35 and conductor 13.

An auxiliary electrode 36.is provided near the anode end of the lamp, this electrode being connected to the midpoint of the secondary oi the lOO Sit

transformer 21 and by the conductor 3?, in circuit with a resistance 38 to the positive terminal of a direct current source (not shown) oi suitable voltage. The negative terminal of the direct current source is connected by the conductor 39 with the cathode. During operation of the device a discharge of low current value (for example, to 50 milliamperes) is constantly maintained through the lamp between the oathode and the auxiliary electrode 36.

When the switch 29 is closed a flow of current occurs through the circuit consisting of conductor 28, the magnet coil 31, the mercury switch 30, the conductor 34, the resistance and the conductor 13. By the consequent tilting of the mercury switch, this circuit is immediately broken, thereby impressing a high potential across the lamp. If the cathode has been previously brought to an operating temperature, a positive column discharge is thereby initiated. In a lamp having a column of 48 inches between electrodes and a diameter of about one inch, the operating voltage is about 250 volts, most of which is consumed in the positive column. Sometimes the make and break of the starting circuit by means of the mercury switch is repeated several times before the discharge is started, this starting operation being well understood.

Were it not for the presence of the grid electrodes around the respective main anodes 2 and 3, the lamp would then operate with current flow during opposite half wave intervals from the cathode alternately to the respective anodes 2 and 3, the current flowing through the entire half wave interval to one of the anodes and then shifting as the polarity reverses to the other anode. Due to the presence of the negatively charged grid the flow of 7 current does not occur to the active anode (that is, the anode which is positive at any particular moment) until the negative potential on the grid has fallen to a predetermined critical value. Thereupon thev flow of current is initiated through the lamp to the active anode and is continued until the potential upon the anode falls below the discharge-sustaining value.

The relation of the current and voltage in the active main anode circuit and the charge of the grid electrodes is illustrated by Figs- 3 and 4. In Fig. 3 the curve 40 indicates graphically the rise and fall of the alternating current voltage in the anode circuit. In Fig. 4 is shown the simultaneous variation of voltagein the circuit of the grid electrode surrounding the respective anode. At the moment the voltage in the anode circuit rises from zero, at the points 42 or 42', the negative voltage on the grid, as indicated by curve 41, is too high to permit the flow of current to the anode. This condition continues until a point is reached, as indicated by the dotted lines 46, 46', when the negative grid voltage has been reduced to a critical value, at

which current begins to flow from the cathode to the active anode, this current being indicated by the full line curve 44. In accordance with this atinas represented by curve 44, is thus of such short duration that it does not injure the lamp. Under these operating conditions the usual ballast resistance is not necessary and the lamp is selfregulating. The same cycle of current flow occurs at the opposite anode of the lamp illustrated when the polarity reverses. Due to the persistence of vision the lamp appears to be continually luminous.

The operation is facilitated by the presence at all times of a small amount of ionization produced by the flow of current to the auxiliary electrode 36. Without the presence of this auxiliary electrode, a relatively long current path between the cathode and the anodes and the consequent high fall of potential would not permit a control of the discharge current in the manner described by control of the starting of the discharge during each half wave interval. The relatively high potential drop in the positive column would either prevent or interfere with the starting of the discharges to the respective anodes. 2

What I claim as new and desire to secure by Letters Patent of the United States, is:-

1. In combination an electric lamp comprising a container, a gaseous filling therein, elec trodes and electrode inleads sealed therein, one

of said electrodes being a thermionic cathode, two of said electrodes being anodes, two grids sealed into said container and surrounding said anodes, an alternating current supply source connected to said electrodes free of ballast resistance in the leads thereof and phase shifting means connected to said grids, said means being adjusted to time the discharges between said electrodes to start on the decreasing side 01 each phase of the alternating current supply to said electrodes.

2. In combination, an electric discharge lamp device comprising a container, a gaseous filling therein, electrodes and electrode inleads sealed therein, said electrodes comprising a thermionic cathode and an anode cooperating with said cathode to support a luminous discharge in said device, a grid mounted in said container and surrounding said anode, an alternating current source connected to said electrodes free of ballast resistance in the leads thereof, and phase shifting means connected to said grid, said means being adjusted to time the discharges between will till

said electrodes to start on the decreasing side of each phase of the alternating current supply to said electrodes.

3. In combination, an electric discharge device adapted to operate on alternating current, an

the current supply.

4. The method of regulating the electrical characteristics 01' an alternating current electric discharge between electrodes free of ballast resistance in the leads thereof in a gas which consists in restraining the establishment of the discharge during each current wave by a negative field about the positive electrode to time the starting of the discharges on the decreasing side or each phase of the current supply of said elect od s.

. MARTIN REGER.

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