US2436951A - Luminescent tube system and apparatus - Google Patents

Description

March 2, 1948. J. H. BRIDGES 2,436,951

LUMINESCENT TUBE .SYSTEM AND APPARATUS Filed Aug. 12, 1943 2 Sheets-Sheet 1 M r 1948. J. H. BRIDGES LUMINESCENT TUBE SYSTEM AND APPARATUS Filed Aug. 12, 1943 I 2 Sheets-Sheet 2 wue/wtom Patented Mar. 2, 1948 LUMINESCEN'I TUBE SYSTEM AND APPARATUS I John Herold Bridges, Paterson, N. J., assignor, by mesne assignments, to National Inventions Corporation, a corporation of New Jersey Application August 12, 1943, Serial No. 498,344

3 Claims. (Cl. 315-257) My application is a continuation in part of my copending application Serial No. 469,365 of December 17, 1942, entitled Luminescent tube system and apparatus, which issued January 7, 1947, as United States Patent No. 2,413,681, and the invention relates in general to electric lighting systems and more especially concerns luminescent tube systems of illumination and apparatus therein.

The object of my invention is the provision of a safe, reliable and highly practical gaseous electric discharge tube lighting system including a transformer source of electrical energy and a plurality of tubes, which system is characterized .by. thoroughly satisfactory distribution of current to the tubes, by prompt and substantially simultaneous energization of the tubes, in which there is displayed'but little stroboscopic effect, and which during operation has an exceedingly good power factor.

Another object of my invention is the provision of a gaseous electric discharge tube lighting'system including a single-transformer source of electrical supply, which system is especially adapted for operatingfour up to as many as ten or more included light tubes, which achieves highly effective control over the tube-energizing current, and which is capable of continued operation in a safe and efficient manner despite failure of one or more of the plurality of included tubes.

Other objects will in part be obvious and in part pointed out hereinafter in connection with the following description taken in the light of the accompanying drawing.

In the accompanying drawing Figure 1 represents a gaseous electric discharge tube lighting system including certain features of my invention, while Figure 2 is a diagram of the circuit employed in Figure 1 and additionally illustrates an advantageous grouping of tubes, and;

Figure 3 depicts a modified form of system in accordance with my invention.

As conducive to a clearer understanding of certain features of my invention, it may be noted at this point that gaseous electric discharge tube lighting systems are today in wide acceptance in various fields of illumination where incandescent lighting systems formerly were employed. There are numerous advantages which more than justify the employment of such lighting systems, among these being characteristically low power .consumption, coolness of operation, simplicity, sturdiness, improved dissemination of light, and

wide choice in the physical form of tube or tubes employed. A number of difierent physical dispositions or arrangements, moreover are possible in obtaining desiredlighting effects as in factories, stores, and private homesiand the use of a variety of fillings such as fluorescent salts on phosphorus as active ingredients of the tubes enables the provision of a number of different colors of light.

Although, as pointed out, there has been wide acceptance of gaseous electric discharge tube lighting, many of the systems present features which for practical reasons are not wholly desirable: Certain of the systems essentially operate at low voltages and the tubes require preheating before initial starting is successfully achieved. These systems usually include a heater circuit and switchover mechanism which, as appurtenances, represent items of expense and a source of possible trouble in operation. A further objection exists in that the tubes flicker during the preheating period and considerable delay occurs before steady operation is achieved. Hot cathode tube systems also are found to be unstable in operation at low temperatures, such as under temperature conditions frequently encountered in outdoor use.

In certain heretofore known gaseous electric 'discharge tube systems of the multi-tube type.

failure of one or more of the included tubes disrupts further operation until full and proper replacement of the worn out tubes is made. This latter objection is notable particularly in lighting systems which include a single transformer source of power and a plurality of tubes connected in series with each other and with the source of power. Such systems also require an increase in operating potential where the number, size, or length of tubes is increased. On the other hand an upper limit on voltages is imposed by the fire underwriters and thus the number of tubes employed as well as the dimensions thereof are sharply curtailed.

There too, are multi-tube systems wherein the tubes are connected in parallel across a source, of

electrical supply. In these systems lower operating potentials are made possible than should series connection of tubes be employed. There is, however, a tendency in such systems for an included tube of low starting potential or of high conductance to draw such a large part of the load current available that other included tubes either fail to start, or when they do start,'draw such low currents that the current densities are wholof the transformer.

step-up transformer portion ll flanked on opposite sides byC-shaped stepped-up output voltage.

1y insufficient to produce the desired brilliant glow.

Still another objectionable feature, commonly termed stroboscopic effect, is encountered in gaseous electric discharge tube lighting. Stroboscopic effect is a rapid, pulsating effect of the light emitted and gives the impression of unsteady illumination. It is quite tiring to the eyes, very discomforting, and in all is wholly undesirable.

One of the outstanding objects of my invention, accordingly, is the provision of a system of;

illumination including a plurality of gaseous electric discharge tubes and a single transformer source of electrical supply, in which system continuous operation of the tubes is not disrupted by failure of one or several of the tubes, in which all tubes promptly reach substantially momentary flow of primary current through full conductance and brilliance and give a stable quality of illumination in and after starting, and in which a maximum length of tubing is safely and eificiently operated.

Referring now to the general practice of my invention, I provide an electrical illuminating system which comprises a step-up transformer,

and a plurality of gaseous electric discharge tubes, advantageously eight to ten or more, or

even as few as four tubes individually connected in parallel circuits with a single output source Each tube circuit includes an inductive reactance, and a gaseous electric discharge tube connected in series. .One or more of the tube circuits, such as alternate circuits additionally include a condenser connected in series with the tube and inductive reactance. The

inductive reactances preferably are of such type as is more fully pointed out hereinafter.

As illustrative of the practice of my invention in Figure 1 of the drawing there is shown an electric lighting system comprising a shell-type it having an inner core outer core portions l2 and i3. The transformer core ismade of paramagnetic material such as of laminated iron. The inner portion of the core preferably has a cross-sectional area substantially twice as large as either of the outer core portions.

In assembled condition the transformer core provides two main magnetic circuits on flux paths mutually including inner core portion l l and respectively including outer core portions i2 and pl'y leads it and ii extend from an alternating current source of electrical supply it, conveniently of 110 or 220 volt rating, to opposite ends of the transformer primary coil. A secondary coil [5 also disposed about inner core portion ii adjacent the primary coil preferably is wound of small gauge wire and possesses such number of turns as to have induced therein a desired At times I mount the primary and secondary coils on the transformer core in superimposed relationship so as '=to gain maximum advantage of compactness and savings in materials.

While it is within the province of my invention to employ the transformer it as an ordinary transformer with the primary and secondary drawing. primary winding to the right along inner core winding is from left to right in Figure 1 of the The flux induced courses from the portion 5-! linking secondary coil l5 and returning through outer core portions l2 and l3 to netically and-an .electromotive force of opposite direction to that resulting from the first half cycle of primary current builds up .across th transformer secondary winding.

In .the illustrative embodiment of my invention shown in Figure 1, I employ some eight to ten or'more, or asfew as four fluorescent gas discharge tubes; such astubes Tl, T2, T3, T t, etc; connected in parallel across the autotransformer windings of transformer I0. .Oneofthe parallel tube circuits conveniently is traced from the righthand side of secondary coil it over lead 22 to terminalfis; thence over leads Z5 and 26, through tube Ti; along lead 21, winding WI of .reactor'Ptl, and lead 28; over lead 2| to terminal 28; and thence along lead It, across coil l4, lead it and coil I5 back to the point .of beginning.

A secondtube circuit is traced beginning at the righthand side ofsecondarycoil it over lead 22 to terminal 2%; lead 24, condenser C and lead 2cm tube T2, through tube T2, over lead 3i], and across winding W2 ofreactor R2; over leads 3| and .2! to terminal Zil; andthence along lead It, across coil is, lead it, and con 15 back tothe point of beginning.

Tube T3 is energized ina circuit traced from the righthand side of coil. lfiover lead 22 to terminal .23; thence over leads 25 and-32, through tube T3; across lead 33, winding W3 of reactor R3, and leadtii along lead H to terminal-2B; and across lead vi 6, coil M, lead it and coil lE-back to the point of beginning.

Another tube circuit; beginning at the righthand end of coil it, extends over lead 22, through terminal 23 across lead Z Rcondenser-C, and lead tdto tube T l; thence across tube Ti, lead 36 and winding Wd of reactor R4; along leads -3'| and 2i to terminal '29; and over lead it through coil it, lead l9, and coil backto the point of beginning.

Still other serially-connected tubes and reactors may be connected across leads 2*] and24 so as to form parallel condensive circuits with the transformer output'winding, and/or in parallel across leads -2I and 25-so as not to include-the condenser C. The tubes of'the entire system provided advantageously are grouped or banked such as in pairs of adjacent or contiguous tubes with one tube only of each pair being in a condensive circuit. Other groupings may be used in which at least one tube in condensive circuit is present, even to the extent of all the tubes of the system being in one bank. Each tube circuit may be closed by a separate switch (not shown) or each bank may be controlled through a separate switch, as pointed out more particularly hereinafter with respect to the embodiment illustrated in Figure 3.

Where the tubes of the entire system form but one bank, I find advantage in placing alternate tubes in condensive circuits and controlling pairs of adjacent tubes with corresponding switches.

Through the use of a reactor in each of the tube circuits, any tendency for one circuit to draw such high currents that the current density in the remaining circuits is insufficient to produce light at full brilliance, is substantially dispelled.

The additional use of a condenser in several of the tube circuits lends an improved power factor to the entire lighting sytem. Tube in the condensive circuits, moreover, operate in out of phase relationship with the tubes in the remaining circuits so as to maintain stroboscopic effect of light emitted from the system as a whole at a minimum.

The lighting system is highly efficient in operation and has particular utility where some eight or ten or more gaseous electric discharge tubes, or even as few as four of such tubes, of substantial length, are to be energized. The tubes employed are found to have long life due at least partially to the excellent control over energizing current maintained in the system. With an increased number of tubes in the system, initial installation costs are readily justified, especially when account is given tothe cost of installing and maintaining a like number of tubes in accordance with the prior art. By operating on increased number of tubes with a single transformer, as for example, up to 70 inches or more of 25 millimeter tubing, core losses in the system decrease, and operational efiiciency increases all the more. The characteristic reduction in stroboscopic effect achieved is enjoyed at full maximum by grouping the tubes so as to obtain blended light from the tubes operating in different phase relationship. One advantageous grouping of tubes is shown diagrammatically in Figure 2 of the drawing where paired tubes in adjacent side by side relationship are connected as in Figure 1 for out of phase operation.

I prefer to use reactors in my lighting system which display little, if any, current controlling action when no-load conditions prevail, but which instantly interpose high reactances when the tube loads are energized and high currents begin to 110W. 1

A reactor, illustrative of the type just mentioned, is indicated generally in Figure 1 by inference character RI. The embodiment shown includes a shell-type core comprising a longitudinal inner core portion 38 having a reactor winding WI thereon and terminating at one end in oppositely extending transverse portions El, E2. Outercore portions 39 and 40 extend from the other end of inner core portion 38 around windin'g WI to vpointsjust short of the ends of extensions El, E2, respectively. The outer core portions thus form magnetic paths through and around the winding WI, which paths respectively ir clude air-gaps GI, G2, of calibrated high,-

reluctance. I prefer to make core portions 33 and of like cross-section and the inner core and equal calibration of air-gaps so as to obtain balanced magnetic conditions in the several magnetic paths of the reactor. 7

Similarly, reactors R2, R3 and R4 comprise inner core portions 38a, 38b and 380, respectively, and corresponding laterally extending'end portions E3, E4; E5, E6; and E1, E8. Reactor windings W2, W3, W4 are mounted on respective inner core portions of the reactors. Outer core portions 39a, 40a; 39b, 42b; 39c, 40c extending from opposite sides of the lefthand ends of the inner core portions, form air-gaps G3, G4; G5, G6, G1, G8 of calibrated reluctance with the laterally extending end portions. I v

In the present embodiment the reactors RIR4 are designed for the same or similar tube loads, and one substantially alike in construction. It will be understood, however, that the reactors may possess-different current limiting qualities depending, for example, upon the tube loads to be energized in-the individual parallel circuits.

The reactors also may to good advantage be of the core-type having single magnetic circuits interrupted by an included air-gap of calibrated reluctance. I r When the primary circuit of transformer Ill, including alternating current source of supply I8, lead I6, primary winding I4 and lead I1, is closed by means of a suitable switch (not shown) an induced voltage is impressed across the transformer output terminals 20, 23. This voltage rises and falls at the same rate as does the curage tending to oppose the provision of the included air-gaps GI-G8 in the reactorcores the decrease in secondary voltage could reach important values and could appreciably retard the initial energization of the tubes. It is to nullify the effect of the self-induced voltage that th air-gaps GIG8 are provided. The tubes thus are energized readily, and high current tends to flow through the system while the tubes remain energized. As soon as this high current fiow is established the reactor coils WI, W2, W3 and W4, however, the conditions in the magnetic circuits of the corresponding reactor cores undergo material change. A high flux is set up in the magnetic core circuits, this flux crossing air-gaps GIG8 in considerable quantity. A voltage, proportionate to the increased current, is induced in coils WI-W4 to oppose further increase in current through the coils and to limit current flow through the tubes TIT4.

It will, therefore, be seen that the reactors not only permit substantially full terminal voltage to be impressed across the corresponding tube loads at the time of starting, but seem to counteract the tendency for increase in current flow due to negative resistance characteristics of the tube loads or due .to short-circuiting. The air-gaps in the reactor magnetic circuits, I being of such calibrated reluctance as to prevent a substantial amountof no-load flux from passing thereacross and yet not being of such 7 high reluctance as to prevent an appreciable amount of flux from crossing while the tubes are energized, are instr mental in maintaining the tube-energizing current within safe and properly controlled limits without impairment of the rapid starting characteristics of the tubes.

In Figure 3 of the drawing a somewhat modified lighting system in accordance with any invention is illustrated. The system is particularly useful where a plurality of light sources controlled by separate switches are needed asin auditorium or stage li hting or in illuminatin a number of rooms of a building. A.v step-up transformer id, such as autotransformer having a primary windin 45 and a s condary W n ing including coilsq45 and 46, is employed for energizing some eight to ten or more or even as few as four gaseous electric discharge tubes, illustratively tubes It-T10, connected in parallel with the transformer secondary winding. The tubes preferably are arranged in remotely spaced or contiguous banks, each bank comprising two or more tubes, such as tubes T5'I?t, Tl-T8 and T9Tit. At least one tube of each bank, as one of tubes T5, T8 and T! U, is provided with an energizing circuit which includes condenser and reactor means; and at least one other tube, as one of tubes T5, T1, and T9 is controlled by reactor means without the aid of a condenser. The tubes in each bank advantageously are grouped together as in side by side relationship illustratively in a fixture having a. suitable reflector, and are controlled by switch means, asfor example one of the switches, 52 or 5t, independently of tubes in the other banks.

In the embodimental system illustrated in Figure 3, a secondary circuit may be traced from the righthand side of coil it over leads 61 and 48 including switch 45a; lead 49 through reactor R5, lead lsa, tube T5 and leads 5|, 44

to junction 13, and thence along lead 43 through :autotransformer coils 5 and 45 back to the point of beginning. A parallel circuit is traced from the righthand side of coil 46 across leads 4'! and it including switch 48a, lead 50}, reactor R6 lead 56a, through tube T55 and over lead tub, through condenser cc, leads 560, El and l i to junction 33, and along lead 4| and through coils 45 and it back to the point of beginning.

Likewise, parallel circuits are closed across the transformer output line 44, 41 through lead 52 including switch 52a, first along lead 53,, through reactor Rl, lead 53a, across tube T1 and through lead 532) and lead 55; and, secondly, along lead 5% through condenser 08 and across leads 56c and 55.

Similarly, two other parallel circuits are closed across the transformer output leads 54, 41, first through lead 56, including switch 56a, across lead ii"! and reactor R3, thence over lead 51a and through tube T9, and over leads 5??) and 59; and, secondly, by way of lead 55 including switch 56a, lead 58 and reactor RIB, thence across lead 53a and tube TH], along lead 581) through condenser Cid, and leads 58c .and 59,

respectively.

While the tubes in the several parallel circuits may be energized from the transformer secondary winding through individual switches in each energizing circuit, particular advantage is gained by energizing the tubes in banks including out of phase tubes through a switch corresponding to each bank as a whole. Thus when a particular switch is closed, out of phase operation, is insured and light emitted from the employ in my li hting syst ms prefer bly ar cold-cathode tubes such as hot-cathode tubes adapted for cold-cathode operation. In this connection it, should be noted that ordinary hot-cathode tubes are readily available on the market, while at this stage of the art standard Cold-cathode tubes are available only on special order. I, therefore, find advantage in shunting the terminals of hot-cathode tubes so as to adapt the tubes for cold-cathode operation. So employed, the tubes display long life and throughly satisfactory light-emissive qualities. I also prefer to employ tubes lined with a fluorescent coating or phosphor and filled with a gas such as neon, argon, helium, or the like, with or without mercury vapor.

In my lighting system the particular parallel network distributes higher operating voltages .limits permitted by the fire underwriters for autotransfoimer equipment, a maximum length of tubing is quite successfully energized.

1 Thus it will be seen that with my invention there is provided .a system of illumination in which the objects hereinbeiore noted, together "with many thoroughly practical advantages, are

successfully achieved. It will be seen that a single transformer output source is used in supplying energizing current to a plurality of gaseous electric discharge tubes in several parallel circuits, and that the voltage in the several circuits is not only high but of substantially uniform value.

It will further be seen that the particular chokecondehser principles employed lend to prompt energization of the tubes, at steady character of illumination substantially free of stroboscopic effect where the tubes are closely grouped as hereinbefore described, and a highly satisfactory power factor; and that the system is adapted for operating a maximum length of included tubing and capable of safe, continued operation despite the failure of one. or more of the several tubes.

As many possible embodiments may be made of my invention -and'as many changes may be made in the embodiments hereinbeflore set forth, it willbe understo-od'that all matter described herein or shown in the accompanying drawing is to be interpreted as illustrative, and not in a limiting sense.

I claim:

i. A gaseous electric discharge tube lighting system, comprisin 7 in combination, a transformer; at least four gaseous electric discharge tubes; a connection from one side of said transformer to the one ends of said tubes; two connections from the other side of said transformer, one being connected to the other ends of one half of said number :of tubes and the other being connected to the other ends of the other one half of said number of tubes; current-limiting self-inductances corresponding in number to said number of tubes, each of said inductances having a magnetic core with included air-gap, individually connected in series with said tubes; and. a

condenser connected in series with one of said two output leads for effecting a phase shift with respect to the other of said output leads.

2. A gaseous electric discharge tube lighting system, comprising in combination; a transfiormer having a primary winding and a secondary winding; at least two pair of closely disposed gaseous electric discharge tubes; and a corresponding number of pairs of parallel circuits interconnecting said pairs of tubes with said transformer secondary winding; each of said pairs of parallel circuits including a pair of reactors hav- =ing magnetic cores with included air-gaps with inductive windings respectively connected in series with the corresponding pair of tubes, and one of each pair of parallel circuits additionally including a condenser in common for effecting a phase displacement with respect to the remaining two circuits.

3. Apparatus for operating at least four gaseous electric discharge tubes, comprising in combination; a transformer having a primary winding 10 and a secondary winding: at least four individual parallel circuits connected with said transformer secondary winding, each of said parallel circuits including an individual current-limiting self-inductance having a magnetic core and an included air-gap; and a condenser in common with one half the number of said individual parallel circuits and in series therewith for efiecting a phase shift with respect to the other one half.

JOHN HEROLD BRIDGES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,298,935 Freeman Oct. 13, 1942 Re. 20,142 Boucher Oct. 27, 1936 0 1,926,423 Barclay Sept. 12, 1933 2,050,135 Tour Aug. 4, 1936 2,025,471 Osborne Dec. 24, 1935

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