US3377508A - Arrangement for varying the luminosity of at least two electric discharge tubes - Google Patents

Description

A ril 9, 1968 E.

ARRANGEMENT FOR VARYING THELUMINOSITY OF A LEAST TWO ELECTRIC DISCHARGE'TUBES FiledMay 6, 1965 5 heets-Sheet l GOMONET 19,377,508

April 68 E GOMONET 3,377,508

ARRANGEMENT FOR VARYING THE LUMINOSITY OF AT LEAST TWO ELECTRIC DISCHARGE TUBES Filed May 6, 1965 3 Sheets-Sheet Fig.3

April 9, 1968 E. GOMONET 3,377,508 ARRANGEMENT FOR VARYING THE LUMINOSITY UP AT LEAST TWO ELECTRIC DISCHARGE TUBES Filed May 6, 1965 3 Sheets-Sheet 5 150.00Qa/m1:

Unite ABSTRACT OF THE DISCLOSURE The device comprises a high leakage transformer 16 with an intermediate tap 18 on its secondary winding. Said tap is connected through an impedance 2t) to a connection 22 between electrically adjacent serially connected discharge tubes. When the value of the impedance is varied, the lighting powers of the tubes on either side of the connection 22 charge in opposite directions.

The luminous effects may be still more varied when switching means are provided.

This invention relates to an arrangement for varying the luminosity of at least two electric discharge tubes enclosing an ionisable atmosphere and fed in series through those terminals of two secondary coils of a transformer which are not directly interconnected, said secondary coils having a terminal in common while their mutual coupling is not loose and the coupling of said secondary coils considered at a whole with the primary coil is loose, as provided for instance through the incorporation of a magnetic shunt.

This invention is characterized by the fact that the common terminal for the two secondary coils is connected with at least one connecting wire interconnecting two electrically adjacent tubes through a variable impedance, the ratio between the discharge voltages of the series of tubes inserted to either side of said connecting wire differing fram the ratio between the open circuit voltages of the two secondary coils.

Arangements have already been provided for gradually modifying the amount of light originating from electric discharge tubes, which arrangements act on the primary coil of each transformer so that they require as many transformers as there are series of tubes, whereas in the case of the arrangement according to the present invention, a single transformer feeds two series of tubes with currents the intensities of which vary in opposite directions. Furthermore, said prior arrangements which are fed with the entire electric power were bulky and costly and the most efiicient arrangements resorted to thyratron circuits of which the adjustments and upkeep are too intricate for use with apparatus adapted for use at different locations without the permanent presence of an operator skilled in electronics.

An arrangement has also been proposed including a single transformer wherein two tubes are connected respectively with the terminals of the resistance of a potentiometer, one of the terminals of the secondary coil of the transformer being connected with the potentiometer slider. A comparatively large power is dissipated in such a resistance. In the arrangement according to the invention, the power spent in the variable impedance is much less important, even in the case of a resistance forming the impedance, since said impedance is fed only with the vectorial difference between the currents passing through the tubes, which difference is at a maximum when the value of said impedance is zero. Furthermore, since the impedance is not inserted in series between the outer terminals of the transformer and those of the series of States Patent 0 3,377,568 Patented Apr. 9, 1968 tubes, it is possible to feed with a given transformer a longer series of tubes.

One object of the invention is to provide an arrangement for varying the luminosity of at least two electric discharge tubes or series of tubes, which arrangement is sturdy, does not entail heavy expenditures and consumes only a small electric power.

The accompanying drawing illustrates diagrammatically and by way of example four embodiments of the invention, wherein the variable impedance is constituted by a slider-carrying rheostat; the elements playing the same part and of which the features are the same or very similar carry the same reference numbers in said figures.

In the drawing:

FIG. 1 is a simple wiring diagram.

FIG. 2 shows a circuit with two rheostats so as to allow a more complete adjustment of the luminosity of the tubes.

FIG. 3 shows a circuit in which a greater range of variations is obtained through a switch.

FIG. 4 shows a circuit including several switches which allow a larger variety of luminous effects.

FIG. 5 is a graph of the modifications of the electric data in a given circuit similar to that shown in FIG. 3.

The circuit according to FIG. 1 includes five tubes 2, 4, 6, 8 and 10 inserted in series with reference to one another and to the terminals of the system of two secondary coils 12, 14 of a transformer 16. These secondary coils 12, 14 which have substantially the same characteristic data are inserted in series and their common point 18 is earthed as conventional in the art. Furthermore and in accordance with an important feature of said circuit, said point 18 is connected in series with a rheostat 20 with a wire 22 connectinng two electrically adjacent tubes 4 and 5.

The primary coil 24 of the transformer 16 is energized by a source .of current 26, 28. The magnetic coupling between the primary coil 24 and the secondary coils 12, 1-4 is loose so as to limit the current passing through the tubes, although the voltage across the terminals of 'the latter sinks when the current flowing through them increases. Moreover, the coupling between the secondary coils is comparatively tight for a purpose to be disclosed hereinafter. It has been found of advantage for these magnetic couplings to be such that r4-E'14 E12-E'12 E14 12 E and E being the voltages across the terminals of the secondary coils 12 and 14 when neither of the latter delivers any current,

E being the voltage across the secondary coil 12 when the tubes 2, 4 are ignited and the tubes 6, 8 and 10 are extinguished,

E' -being the voltage across the terminals of the secondary coil 14 when the tubes 6, 8 and 10 are extinguished and the tubes 2 and 4 are ignited.

For instance, the windings 12 and 14 may be juxtaposed or superposed and be wound over a fraction of the magnetic circuit of the transformer, which fraction is separated by a magnetic shunt showing a gap from the fraction of the magnetic circuit carrying the primary coil.

The operation of said circuit is as follows:

If the resistance of the rheostant 20 is infinite, for instance if it cuts off the connection between the point 18 and the connecting wire 22, all the tubes are fed by the same current supplied by the secondary coils 12 and 14 considered as a whole.

If in contradistinction, the resistance of the rheostat is zero, the tubes 2 and 4 are fed by the secondary coil 12 and the tubes 6, 8 and 10 by the secondary coil 14. The

system of tubes. 3 and 4 of which the re-ignition voltage is clearly lower than that of the system of tubes 6, 8 and 10 is first reignited during each half period. Once said tubes are reignited, there is a large leak flux between the primary coil 24 and the secondary coils, which reduces not only the voltage across the terminals of the secondary coil 12, but also across the terminals of the secondary coil 14. As a matter of fact, since the coupling between said secondary coils is tight, these secondary coils are traversed substantially by the same magnetic flux and consequently the electromotive forces produced remains substantially equal or proportional if the number of their turns is different.

The. voltage across the terminals of the secondary coil 14 may then be too weak and incapable of ensuring the re-ignition of the tubes 6, 8 and 10 which remain then dark or perhaps may show a slight luminosity by reason of the presence of capacitory currents or by reason of an insufficient insulation. It is sufficient for this purpose for the magnetic coupling between the two secondary coils to be sufficiently tight. More the magnetic coupling between the two secondary coils is tight and less the difference between the reignition voltages of the series of tubes 2, 4, on the one hand and 6, 8 and 10 on the other hand needs to be high for obtaining extinction.

For intermediate values of the rheostat 20, there appears across the terminals of the latter a voltage ascribable to the fact that it is fed with a current of an intensity equal to the difference between the intensities in the tubes 2 and 4, on the one hand and in the tubes 6, 8 and 10 on the other hand. Said voltage is added as a vector to that corresponding to the secondary coil 14, which allows igniting the tubes 6,- 8 and 10. Conversely, the voltage across the terminals of the rheostat 20 is subtracted from that of the secondary coil 12 and reduces the current in the tubes 2 and 4. These results are all the more noticeable when the resistance of the rheostat is higher and they lead to equality in the illumination of the various tubes when the said resistance is infinite, as already mentioned hereinabove. The power spent through Joule effect in the rheostat 20 .is all the weaker when the coupling between the two secondary coils is tighter.

If i designates the intensity in the tubes when the resistance at 20 is infinite, the following variations are obtained when the resistance provided by the rheostat increases gradually from zero to infinity: the current in the tubes 2 and 4 varies from slightly above 2i and i while the current in the tubes 6, 8 and 10 varies between and i The reverse movement of the rheostat slider provides the reverse succession of luminosities.

The circuit illustrated in FIG. 1 lends itself to numerous modifications: the discharge tubes may be of different types and their number may be different from the secondary coils may show different electric characteristics provided the quotient between their open circuit voltages is different from the quotient between the reignition voltages required for the corresponding series of tubes.

When selecting the cross-section of the wire forming the secondary coil 12 and the size of the tubes 2 and 4 and of their electrodes, it is necessary to take into account the fact that when the resistance at 20 is zero, the current i in the secondary coil 12 is higher than the normal current i corresponding to an infinite resistance at 20, the relationship between i and i being as a first approximation:

i number of turns of 12+ 14 11, number of turns of 12 The circuit illustrated in FIG. 1 does not allow lowering the luminosity of the tubes 2 and 4 to a low figure or to zero. The modified embodiments illustrated in FIGS. 2, 3 and 4 do not show said drawback.

The circuit illustrated in FIG. 2 includes two rheostats 20 and 30 which are controlled independently or not and which are connected with two different wires 22 and 32 each of which electrically connects adjacent tubes. The operation of said circuit is as follows:

Starting from the position illustrated for which the resistance of the rheostat 20 is zero and that of the rheostat 30 infinite, the luminosity of the tubes 2 and 4 is at a maximum while that of the tubes 6, 8 and 10 is weak or equal to zero.

If the resistance of the rheostat 20 increases, the luminosity of the tubes 2 and 4 is reduced, while that of the tubes 6, 8 and 10 increases. When the resistance of the rheostat 20 has become infinite, the same current passes through all the tubes. Said variations correspond to those described with reference to FIG. 1.

If thenafter, the rheostat being left in a position of infinite resistance, the resistance of the rheostat 20 is gradually reduced down to zero, the luminosity of the tubes 8 and 10 increases, while that of the tubes 2, 4 and 6 decreases and becomes finally equal to zero. In a manner similar to that disclosed for the tubes 6, 8 and 10 in the case of FIGFI, the voltage produced by the secondary coil 12 is not sufficient for the reignition of the tubes 2, 4 and 6 since the leak flux ascribable to the current in the secondary coil 14 lowers said voltage.

The luminosities of the tubes in the series of tubes 2, 4 and 8, 10 vary thus in opposite directions between zero and a maximum. The variation in luminosity for the tube 6 coincides with that of neither of said series. This difference may be beneficial and allows giving a further luminous effect, or again it is possible to conceal said tube, in which latter case, it is of advantage to reduce the bulk of said tube 6 by reducing considerably its length and increasing the pressure of the gas filling it.

The circuit illustrated in FIG. 3 provides the same luminous effects as those disclosed with reference to FIG. 2. It includes a single rheostat 20, but a change-over switch 34 allows connecting the latter selectively with the connecting wire 22 or with the connecting wire 32.

For the position of the switch illustrated in solid lines in FIG. 3, the circuit is equivalent to that illustrated in FIG. 2 in the case where the rheostat 30 has an infinite resistance. In the position of the switch illustrated in interrupted lines, the circuit is equivalent to that illustrated in FIG. 2 for the case where the rheostat 20:has an infinite value.

It is of advantage to operate the switch 34 only when the current passing through it is equal to zero or is very weak. This cuts out the production of radio-electric strays and prevents a speedy wear of the contact-pieces of the switch. It is possible, with a view to satisfying said condition to control the switch or a locking system for the latter through the means controlling the rheostat, so that the switch may be operated only when the rheostat resistance is at a maximum.

When the current flowing through a series of tubes is equal to zero, it is an easy matter to produce switching operation in said series, so as to prepare subsequent luminous effects.- FIG. 4 illustrates a circuit of such a type.

Said circuit differs from that illustrated in FIG. 3 through the incorporation of two further luminous tubes 36 and 38 and of two change-over switches 40 and 42.

The switch 40 allows inserting in the circuit either the tube 4 or the tube 36. The switch 42 plays the same part for the tubes 8 and 38. In order to cut out the strays and to reduce wear, said switches are actuated only when they are fed with a current which is weak or equal to zero; this is obtained when the resistance of the rheostat 20 is zero and furthermore, in the case of the switch 42,

' when the switch 34 is in the position illustrated in solid lines and, in the case of the switch 40, when the switch 34 is in the position illustrated in interrupted lines.

The circuit illustrated in 'FIG. 4 may be used for instance as an electric sign for a dealer in automobiles and motorcycles. The tubes 2 and 10 are formed so as to show respectively the words Autocars and Motorcycles, and the luminosities of said words vary in opposite directions between zero and a maximum. The tubes 4, 8, 36

and 38 produce lights of different colours and illuminate a translucent plate on which is written the dealers name,

this background shows thus a colour which varies constantly and gradually without ceasing being luminous.

Illuminating arrangements fed by circuits designed in accordance with the invention may serve for modifying in opposite directions the illuminations provided for two showcases or two electric signs of a same shop. It is also possible to resort to said illuminating arrangement for illumination of a same show-case or of a same electric sign with light of gradually varying colour, the two series of tubes producing then lights of two different colours.

For advertising arrangements to be seen from a long distance, for instance those erected on roofs, each tube of one series may be near enough a tube of the other series for an observer not to be capable of distinguishing them from each other. He will then be under the impression of a single tube the colour of which is changing gradually.

The curves in 'FIG. show modifications in the electric data in a circuit according to FIG. 3 when the resistance of the rheostat 20 varies between zero and 150,000 ohms. For this last value, the current passing through the rheostat is only a fraction of a milliampere. Said current does not modify practically the balance between the intensities flowing through the different tubes and produces no objectionable strays nor does it lead to any speedy wear upon operation of the switch. It is therefore unnecessary for the rheostat to be capable of assuming a still higher resistance. In said embodiment, each secondary coil is adapted to feed 0.025 amperes during continuous operation and to provide 3,000 volts under no-load conditions.

The tubes 2, 4, 8 and 10 are each 3 m. long, their inner diameters are equal to 14 mm. and they are filled with a mixture of mercury vapour under low pressure and argon.

The tube 6 is similar, but its length is reduced to 2 In.

The curve 46 illustrates the modifications in current intensity in the tubes 2 and 4 while the curve 48 illustrates the modifications in intensity in the tubes 6, 8 and 10 when the resistance of the rheostat varies between 0 and 150,000 ohms, the switch 34 being assumed to be in the position illustrated in solid lines in FIG. 4. For a rheostat value equal to 150,000 ohms, all the tubes are fed with a current of about 0.020 ampere. The curve 50 illustrates the power lost in the rheostat and which has to be dissipated by the latter, while the curve 52 illustrates the intensity of the current passing through said rheostat.

When the switch is in the position illustrated in interrupted lines, the intensity in the tubes 8 and 10 varies in the same manner as that disclosed hereinabove for the tubes 6, 8 and 10.

Experience shows that a pleasant effect is also obtained by substituting for the rheostat subjected to a substantially continuous modification a change-over switch and a system of resistances producing, in succession the following resistances: 0-7,000 ohms20,000 ohms 40,000 ohms70,000 ohmsl50,000 ohms.

In addition to the modifications already mentioned, the circuits described may be modified in various further manners without widening the scope of the present invention. It is possible for instance to replace the rheostat by a variable impedance of another type, such as an inductance coil in which a fraction of the magnetic circuit is adapted to move so as to adjust its impedance by modifying one or more air gaps.

The rheostat and switches, if any, may be controlled manually in order to modify the effect obtained as de-- sired by the operator; this may also be obtained by a machine ensuring a cyclic repetition of the different effects.

What I claim is:

1. A circuit arrangement for modifying the luminosity of electrical discharge tubes enclosing an ionizable atmosphere comprising a transformer having a primary Winding and a secondary winding, a plurality of tubes connected in series with each other and with the secondary winding of the transformer forming a closed electrical loop, a variable impedance connected at one end to an intermediate point of said secondary winding, switch means for selectively connecting the other end of said impedance to one of an opposite series of connections of one tube of the series, and switch means for selectivity connecting said one tube in series with other selected tubes of said series.

2. A circuit arrangement for modifying the luminosity of electric discharge tubes enclosing an ionizable atmosphere comprising a transformer having a primary winding and a secondary winding, a plurality of tubes connected in series with each other and with the secondary winding of the transformer forming a closed electrical loop, a variable impedance connected at one end to an intermediate point of said secondary winding, and switch means for selectively connecting the other end of said impedance to one of an opposite series of connections of a plurality of tubes of the series.

3. A circuit arrangement as defined in claim 2 further including switch means for selectivity connecting said plurality of tubes in series with other selected tubes of said series.

4. A circuit arrangement for modifying the luminosity of electric discharge tubes enclosing an ionizable atmosphere comprising a transformer having a primary winding and a secondary winding, a plurality of tubes connected in series with each other and the ends of the secondary winding of the transformer to form a closed electrical circuit, a variable impedance having one end connected to each end electrode of one tube of the series, and means for connecting each of the other ends of said impedances to an intermediate point of the secondary winding of the transformer.

5. A circuit arrangement for modifying the luminosity of electric discharge tube enclosing an ionizable atmosphere comprising a transformer having a primary Winding and a secondary winding, a branched circuit containing tubes in each branch connected to the ends of the secondary winding of the transformer, a main tube interposed between said branched circuit and the ends of the secondary winding, switch means for selectivity connecting said main tube in series with one of the selected branches of the branched circuits, a variable impedance having one end connected to an intermediate point of said secondary winding, and switch means for selectivity connecting the other end of said impedance to one of the opposite ends of the main tube.

6. A device for modifying the luminosity of electric discharge tubes enclosing an ionizable atmosphere, comprising, a source of alternating electric current, a high leakage transformer having a primary winding energized by said source and a secondary winding, a plurality of tubes each connected in series with each other and with the secondary winding of the transformer forming a closed electrical circuit, a variable impedance connected to an intermediate tap on said secondary winding and to a pair of adjacent tubes in the series, and means for varying said impedance when an electric discharge passes through said tubes, the no-load voltage of said secondary winding being greater than the starting voltage of the discharge in said plurality of tubes, and the ratio between the no-load voltages between said intermediate point and respectively the ends of the secondary winding differing substantially from the ratio between the total discharge voltage of the corresponding respective series of tubes on either side of the common point of said pair of adjacent tubes.

7. A circuit arrangement as defined in claim 6 wherein the impedance of connections between adjacent tubes in the series are practically equal to zero.

8. A circuit arrangement as defined in claim 6 wherein the variable impedance is a resistance.

9. A device for modifying the luminosity of electric discharge tubes enclosing an ionizable atmosphere, comprising, a source of alternating electric current, a high leakage transformer having a primary winding energized by said source and a secondary winding, a plurality of tubes each connected in series with each other and with the secondary winding of the transformer forming a closed electrical circuit, a variable impedance connected to an intermediate tap on said secondary Winding, means for varying said impedance when an electric discharge passes through said tubes, the no-load voltage of said secondary winding being greater than the starting voltage of the discharge in said plurality of tubes, and switch means for selectively connecting the other end of said impedance to one of an opposite series of connection of one tube of the series.

10. A device for modifying the luminosity of electric discharge tubes enclosing an ionizable atmosphere, comprising, a source of alternating electric current, a high leakage transformer having a primary Winding energized by said source and a secondary winding, a plurality of tubes each connected in series with each other and with the secondary windingof the transformer forming a closed electrical circuit, a variable impedance connected to an intermediate tap on said secondary winding, means for varying said impedance when an electric discharge passes through said tubes, the no-load voltage of said secondary winding being greater than the starting voltage of the discharge in said plurality of tubes, and switch means for selectively connecting the other end of said impedance to one of an opposite series of connection'of a plurality of tubes of the series.

11. A circuit arrangement as defined in claim 10 fur ther including a switch means for selectively connecting said plurality of tubes in series with other selected tubes of said series.

12. A device for modifying the luminosity of electric discharge tubes enclosing an ionizable atmosphere, comprising, a source of alternating electric current, a high leakage transformer having a primary winding energized by said source and a secondary winding, a plurality of tubes each connected in series with each other and with the secondary winding ,of the transformer forming a closed electrical circuit, a variable impedance having one end connected to each end electrode of one tube of the series, means for varying said impedance when an electric discharge passes through said tubes, the no-load voltage of said secondary winding being greater than the starting voltage of the discharge in said plurality of tubes, and means for selectively connecting each of the other ends of said impedances to anintermediate tap of the secondary winding of the transformer..

13. A device for modifying the luminosity of electric discharge tubes enclosing an ionizable atmosphere, comprising, a source of alternating current, a high leakage transformer having a primary Winding energized by said source and a secondary winding, a branched circuit containing tubes in each branch connected to the ends of said secondary winding, a main tube interposed between said branched circuit and the ends of said secondary winding, switch means for selectively connecting said main tube in series with one of the selected branches of the branched circuit, a variable impedance having one end connected to an intermediate tap of said secondary winding, means for varying said impedance when an electric discharge passes through at least one of said tubes, and switch means for selectively connecting the other end of said impedance to one of the opposite ends of the main tube.

References Cited UNITED STATES PATENTS 1,729,091 9/1929 Atherton 3l5-257 3,275,788 9/1966 Ferguson 3152S7 OTHER REFERENCES 640,334 12/1936 Germany.

JAMES D. KALLAM, Primary Examiner. JOHN W. HUCKERT, Examiner. J. D. CRAIG, Assistant Examiner.

Images