US2356369A - Gaseous discharge tube circuit - Google Patents

Description

1944- D. w. ABERNATHY 2,356,369

GASEOUS DISCHARGE TUBE CIRCUIT Filed Dec. 8, 1941 SELF OPERATING SwlTcH L INE INVEN OR.

ATTORNEyX.

Patented Aug. 22, 1944 GASEOUS DISCHARGE TUBE CIRCUIT David W. Abernathy, Chicago, Ill., assignor to Products Development, Inc., Chicago, Ill., a corporation of Illinois Application December 8, 1941, Serial No. 422,060

3 Claims.

This invention relates to an improved and simplified circuit for striking an arc and maintaining a constant operating voltage in a tube containing conductive gases.

The object of this invention is to provide a simple and fool-proof circuit for starting and operating gaseous discharge tubes, such as, for example, those known as fluorescent tubes.

Another object of the invention is to provide a simple circuit for starting and operating such gaseous discharge tubes as described which will utilize economical and compact impedance elements capable of being easily constructed and assembled and associated with the gaseous discharge tube.

A further object of this invention is to provide a new and improved method of initiating and maintaining the arc in a gaseous discharge tube.

A further object of this invention is to provide a novel and improved circuit for initiating and maintaining the arc in a gaseous discharge tube whereby when the tube is normally operating the power factor of the circuit will be as close as practicable unity.

Still a further object of the invention is to provide a novel and improved circuit for initiating and maintaining the arc in a gaseous discharge tube in which no reactive elements are efiective in the circuit when the tube is normally operat- Still a further object of the present invention is to provide a novel and improved circuit for initiating and maintaining the arc in a gaseous mode of practicing same, and many of its advantages and features should be readily understood and appreciated.

Referring to the drawing, the figure is a diagrammatic representation of an electrical circuit used in connection with a fluorescent lighting tube and embodying my new invention.

Thenumeral it represents a gaseous discharge tube such as the type filled with conducting gas and having the walls thereof coated with materials which fluoresce when an arc in the tube causes emissions of electrons and the consequent production of rays of certain wavelengths, in a well-known manner.

The tube 36 is connected with a source of alternating current, such as an A. C. line by the leads H and 12, whereby an appropriate A. C. voltage may be impressed across the tube. The tube I0 is provided with filaments I3 at opposite ends thereof and between which the path 01' are or discharge of the tube is adapted to be established. Said filaments are part of a branch circuit l4 arranged parallel to the discharge path, having a self-operating switch, and serving to shortcircuit the arc or discharge path of the tube when the switch l5 isclosed. The switch 65 is of a well-known type and includes aibi-metal member enclosed within a glow tube and adapted to be moved against a fixed electrical contact to close the circuit M.

The lead H is provided with a resistor l1 and a condenser E8 in series with a switch l9, said condenser and switch l9 being connected across the resistor H. The lead H is also provided with a line switch I6.

The device operates in the following manner.

Upon the switches l6 and [9 being closed, there will be impresed line voltage across the glow tube of the automatically operating switch l5. This will cause the bi-metal element of the tube to heat up and will thus bring about its engagement with the electrical contact therein to thereby close the circuit 14. The operation of the switch 15 is well -known and as the construction thereof per se forms no part of the present invention, it is not believed necessary to describe it in greater detail.

ments of the various elements of the apparatus I The closing of the circuit M will cause a flow of current through the entire circuit which will be limited merely by the resistance of the filaments i3 and that of the relatively high resistance l1. During this period clouds of electrons will be emitted by the heated filaments [3, thus causing the tube conductivity to be increased and thereby making it possible to ignite said tube at a comparatively low ignition voltage. During the time that the switch [5 is closed the voltage appearing across the resistor l1 will be a substantial portion of line voltage, since the voltage drop across both of the filaments I3 is comparatively sistor l1.

small. For example, in a 115 volt line circuit, utilizing a 20 watt tube, the voltage across the filaments will be about 25 volts.

The establishment of contact in the glow tube of switch It extinguishes the glow therein and consequently there is no heat to keep the bi-metal element in its engaged position.

The switch I will be opened as soon as the bimetal element thereof has coold'and moved from engagement with its contact. Upon the opening of said switch the tube will be ignited by the combined voltages of the line plus the discharge voltage of the condenser I8, as will be now more fully explained.

The condenser l8 has a rather large capacity in order that it will require somewhat more than a half cycle of the line frequency to discharge. During the time that the switch l5 was closed, the condenser I8 was, of course, charged by the voltage existing across the resistor 11. When the switch l5 opens, the condenser I 8 will begin to discharge at a constant polarity through the re- While this is occurring, the alternating line voltage is appearing across the tube l0. Since it requires more than a half cycle for the condenser i8 to discharge, during one of the half .cycles of the full cycleimmediately following the assaaso 1. In combination in a fluorescent lighting circult, a fluorescent lighting tube having independent thermionic filament means at opposite ends 'operative when electrically heated to provide opening of the switch IS, the polarity of line volt- M age existing across the tube III will be the same as the polarity of the voltage set up across the resistor I! by the discharging condenser IS. The effect will be that during this half cycle of common polarity the voltage across the tube will be equal to line voltage plus that portion of discharge voltage of the condenser l8 which has not as yet leaked off.

The combined voltages reach and exceed the ignition voltage of the tube, and therefore cause the arc to be struck. Since the conductivity of the tube when the arc has been struck is considerably greater than the conductivity of the resistor H, the condenser l8 will.discharge through the tube sustaining the ignition voltage a suflicient time to establish the arc inthe tube.

The increased conductivity of the tube 10 will thereafter permit flow of current therethrough and cause the operation of the tube at the normal voltage. The condenser l8 and resistor IT in parallel now serve as a current-limiting impedance.

The condenser it may now be removed from the circuit by opening the switch l9, and eliminating reactive influence upon the line. Thus with only the resistive element I! in the circuit, the same will have a power factor of one. This is an important feature of my invention since it reduces operating costs of maintaining such a circuit.

It will be noted that by means of my invention I have eliminated from circuits of this nature the so-called ballast or inductive reactance which has heretofore been used. The economy in production effected thereby is obvious.

It is believed that my invention, its mode of construction, arrangement, assembly, association of parts, the mode of practicing the method thereof, and many of the advantages and features should be readily understood from the foregoing without further description, and it should also be manifest that while a preferred embodiment of the invention has been shown and described for illustrative purposes, the details are nevertheless capable of wide variation within the purview of my invention as defined in the appended claims.

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

localized ionization of the gas filling the tube, an alternating current source having one lead connected to the filament means at one end of the tube alone and the other lead connected to the filament means at the other end of the tube alone soas to enable A. C. line voltage to be impressed through the tube for activating the fluorescent coating within the tube, a branch circuit in parallel to the discharge path of the tube and connecting said filament means, an automatically operating switch device in said branch circuit responsive to energization by said source to break the branch circuit after a predetermined interval of operation long enough to permit pre-ignition heating of the filament means, a resistor in one of said leads capable per se of serving as the entire overload-preventing device for running operation of the lighting circuit without the use of a conventional reactance ballast, and a condenser connected in parallel to said resistor in said one lead and of such capacity that it requires more than one half cycle to discharge following automatic opening of said switch device so that in the second half cycle following such opening the discharge voltage of the condenser will be additiveto the line voltage as a result of coincidence of polarity and the combined voltages will temporarily attain to the ignition voltage of the tube to cause the arc to be struck therein between the filament means, the relationship of elements being such that after being struck as aforesaid the arc is maintained by the line voltage through said lighting circuit as limited by the resistor.

2. A fluorescent lighting circuit as defined in claim 1 in which a condenser-disabling switch is connected in series with the condenser for the purpose of removing the condenser from service after the arc has been struck in the fluorescent tube, leaving the resistor thereafter as the sole current limiting device in the circuit during normal operation of the fluorescent tube and attaining as nearly as practicable unity power factor in the lighting circuit.

3. A gaseous discharge tube circuit comprising, in combination, a gaseous arc discharge lighting tube having individual thermionic filaments at each opposite end providing a discharge path therebetween and capable of operating on A. C. line voltage modified only by appropriate resistance to prevent overloading, an alternating current source having separate leads respectively connected to said filaments, means short circuiting said, discharge path and including a device automatically operative to open the short circuit after an interval of operation ample for heating the filaments to adequate-thermionic condition, a resistor in one of said leads to limit the current in the circuit, a shunt across said resistor including a condenser of such capacity that as a result of opening of said short circuit at least the major proportion of the voltage discharge by the condenser is superimposed upon the line voltage for striking the lighting arc between the heated filaments, and a switch in said shunt for disconnecting the shunt from the tube circuit and rendering the condenser inactive during running operation of the tube circuit following lighting of the tube, whereby the normal operating power factor of the tube circuit will be as close as practicable unity.

DAVID W. ABERNATHY.

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