US2428646A - Luminescent tube system - Google Patents

Description

Oct. 7, 1947. c. P. BOUCHER LUMINESCENT TUBE SYSTEM Original Filed Aug. 21, 1940 2 Sheets-Sheet 1 13 4/64701? acer m% wm l *5 mm Caz-Z96" 2250 19%; W Pa sy Oct: 7, 1947. c. P. BOUCHER 2,428,646

LUMINESQENT TUBE SYSTEM Original Filed Aug. 21, 1940 ,2 Sheets-Sheet 2 (9] $110 w 6 a v Ind Eyre? I ('arZea P3014026;-

Patented Oct. 7, 1947 2,428,64i6' LUMINESCENT TUBE SYSTEM Charles Philippe Boueher, Fostoria, Ohio, assignor, by mesne assignments, to National Inventions Corporation Jersey a corporation of New Original application August 21, 1940, Serial No. 353,572, now Patent No. 2,317,845, dated April 27, 1943. Divided and thisapplication March 18, 1943, Serial No. 479,663

This applicationfor patent is a division of my copending application Serial No. 353,572, filed August 21, 1940, which issued April 2'7, 1943, as United States Patent No. 2,317,845, entitled Luminescent tube lighting apparatus, and the invention relates to electrical transformers for energizing luminescent tubes and to a mounting for the transformers and luminescent tubes.

One of the objects of'my invention is to provide a mounting for the-' transformer and luminescent tubes of an illuminationunit such that all the parts are assembled'ina compact unit.

Another objectis to provide a luminescent tube system in which flickering or stroboscopic effect of the light from a group of tubes is substantiall eliminated.

Still another object-of the invention is to provide a luminescent tube system in which electrostatic stress between the tubes is reduced to a negligible value. p

A further object is to provide a luminescent tube system in which the tubes operate at low voltage and with high efliciency.

Other objects will be obvious in part or in part pointed out hereinafter.

The invention accordingly consists in the com bination of elements, features of construction and arrangement of parts aS described herein, the scope of the application of which is set forth in the claims.

In the accompanying drawing illustratingcertain features of my invention:

Figure 1 represents a; sectional plan view of an illumination unit including the transformer and the luminescent tubes. 7

'Figure 2 is an enlarged vertical side section-on the line 22 of Fig. 1." I

Figure 3 is an'enla-rged vertical section on the line 33 of Fig; 1, showing-details of the transformerr Figures 4, 5, 7 circuits which may be employed. I

Like reference characters refer to like parts in the several figures of the drawing.-

As conducive-tea clearer understanding of'the nature of my invention,- it may be noted at this. point-that, for example,-in the illumination of asign or display,- employing forthat purpose one or more luminescent tubes as a source-of light,- one'or morehigh potential electrical transformers 6fand-7 arediagrams of various 3 Claims. 01. sis-4.47)

are required. Thesetransformers have heretofore been mounted in a protected place either in side a building or in a casing separate from the luminescent tubes for lighting the sign or display structure,ythus necessitating long high-tension cables and requiring several steps to' be taken in fastening the parts inplace and in mak- It is apparent that ing electrical connections. such an arrangement is expensive, due to the cost of the high-tension cables; and of the casings where separate ones are used and also due to the separate labor charges for each step in the installation. To overcome these disadvantages is one of the ob ects-of my-invention.

In heretofore known luminescent systems for signsor displays, employing one or more luminous tubes, it has been'customary to operate these tubes from the same or separate transformers in such'a manner that they all become ionized and conductive at substantially the same instant. Where a -cycle source of electrical energy is used, the tubes become luminous times per second. Due to persistence of vision, the tubes appear to emit substantially a steady glow of light but even while being lighted as many as 120 times per second, some flickering is notice able, particularly where the tubes are mounted in agroup in front of the same reflector. This phenomenon is called'a stroboscopic effect and is especiallynoticeable whenthe operation of the tubes is aifectedwby variations in the voltage impressed across their, terminals and in the wave form factor of'thecurrent. Aging of the tubes and variations in their operating characteristics due to changing temperature conditions also cause this stroboscopic effect'to be particularly noticeable.

In the operation of luminescent tubes which are grouped closely together for illumination purposes, it is ordinarily necessary to mount the tubes so that theyare spaced, apart in order to avoid dielectric discharges between them. This spacing is undesirable because it exaggerates the flickering effect described above. Moreover, it re-' duces the concentration of light from the tubes and thus makes them' less satisfactory for.il'-' lumination-purposes- 1 In luminescent tube systems now in use, it is necessary to employ highvoltage to initiate operationof the -tubes;v This-high voltage is not needed. after the tubes have become started but is still impressed across their terminals. Complicated starting devices are used which require constant attention and frequent replacement. or repair. This situation makes for an increased power consumption, a correspondingly lower efficiency and a high maintenance cost.

Accordingly, another object of my invention is the provision of a compact, rugged and efficient illumination unit of reduced stroboscopic effect, good and uniform light intensity and, moreover, of good operating power factor all with a minimum of attention and a minimum of replacement or repair.

Referring now to the practice of my invention, attention is directed to Figs. 1 and 2 in which I have shown illustratively a' casing and reflector' In in which are mounted two luminescent tubes I I and I2. These tubes are energized by a transformer I3 which is housed in transformer compartment I4a of an enclosure I4, also having a ering which is frequently noticeable in the ordicondenser compartment M1), the enclosure being attached to the rear of the reflector ID, as by bolts I5. Lugs I6 are provided on the enclosure I4 for supporting the whole lighting structure.

. Tubes II and I2 are supported at their ends in porcelain housings I'I by-spring clamps I8, which make firm electrical contacts with the tube terminals. The porcelain housings I'i are secured in place in the casing by screws I9, further insulation of the tube terminals from the metal of the casing I0 being provided by spacers of insulating material. Poncelain cover plates 2I are placed over the front apertures of the housings I'I when the tubes are in position. The tubes I I and I2 are energized thru spring clamps I8 and leads 22 from thetransformer I3, which is shown in detail in Fig. 3.

The transformer I3 has a primary winding comprising two coil sections P1 and P2 connected in series and mounted'o-n thecore member 24. Two secondary windings S1 and S2 are mounted on the other core member 25. The core members 24. and 25 are held in albutting relationship by core bands .26 and 21. Magnetic shunt parts 28 and '29 are placed so as to form shunt paths around the primary and secondary windings, and thereby decrease the sustaining voltage of the tubes or the voltage applied to the tubes each half-cycle following the striking. Silencing clamps 30, 3|, 32 and 33 are fitted over the shunt parts 28 and 29 to prevent their laminations from chattering. Shunt pieces 34 and 35 are inter posed between the shunt parts 28 and 29 and the core members 24 and 25 at their centers and insulating blocks 3B, 3 1, 3B and 39 are fitted between the shunt parts and the core members at their ends to maintain the shunt parts firmly in position. The shunt partsare held in place by clamps 40 and 4| whichare tightened by the bolt and nut 42. .The transformer is maintained in a proper position in its casing I4a by spacers 43 and 44 of non-magnetic material which fit over the core bands 26 and 21.

Referring now to Fig. 4, there is diagrammatically represented one circuit which may be used. in the transformer and tube systemof my invention. The primary winding coil sections P3 and P4 are mounted on the core 45 and are connected in series at their inner terminals. It.

will be understood that in operation, core. and coils are mounted within the transformer compartment of the lighting structure. Their outer terminals are connected to a source of alternating'current electrical energy 46 thru a thermal 4 circuit breaker 4?. The purpose of the circuit breaker is to prevent overloading of the primary winding. It operates to open the primary circuit when the temperature of the primary winding exceeds a value corresponding to the maximum safe load of the primary. winding.

There are two secondary windings S3 and S4 energizing the tubes T3 and T4, respectively, by way of leads 4B, 49, 50 and 5|. A condenser 52is connected in series With one of the tubes as by connecting it in the lead 49 to the tube T3. In.

operation, here again it will be understoodthat the condenser is located within the condenser compartment provided in the casing of the lighting structure. The condenser 52 is of such capacitance as to cause the current in the tube .T3 to substantially lead the current in tube T4.

By this arrangement the number of periods of illumination from the group of tubes is doubled from 120 to 240 times per second. Thus the flicknary. installation is substantially eliminated. This is particularly true where the two tubes are mounted closely together, and where they are operated at high current densities. Such an arrangement is practical where the circuit of Fig. 4 is used because the adjacent tube terminalsv are always at potentials of about the same value, since they are connected to corresponding termi nals of their secondary windings, any difference being due to phase displacement by the condenser., Thus the left-hand terminals of tubes T3 and T4 are shown at oneinsta'nt as being connected to the positive terminals of the windings S3 and S4 and the right-hand terminals] of the same potential, there is no danger of dielectric discharge between adjacent portions of the, tubes,

even when the-tubes are .mounted in close proximity. 1

The presence of the condenser 52 in the circuit of the tube T3 increases the reactance of that circuit. Accordingly, where the secondary windings S3 and S4 are of the samevoltage rating during the conductive periods of the tubes the tube T3 must be one operating at a lower voltage than tu e T4. Thus tube T3 may be of larger diameter than tube T4 or it. may be one having electrodes of lower resistance. TubeTa' may also operate at a lower voltage than tube T4 because it contains a different gas or gas mixture. If it is desirable to have tubes which are'identical in rating, which ordinarily is the case, the winding S3 must be one which develops a higher tube sustaining voltage than winding S4.

Considering nowanother circuit embodying myinvention, attention is directed to Fig.5 inwhich I show a transformer comprising a core 53, a

primar winding consisting oftwo coil sections mary winding present a potentiallin excess of the potential of the source of supply, the. circuit has theadvantagethat the condenser maybe of less capacity, and of less expense," than otherwise would be required. 4 s

One terminal of thesecondary winding S5 is The function of this condenser is.

connected to the left-hand terminal of a luminescent tube T5 by the lead 51 thru the condenser 58. The other terminal of winding S5 is connected to the right-hand terminal of another lumines'cent tube Ts by the lead 59. Likewise, one terminal of winding Se is connected to the lefthand terminal of tube Ts by the lead 69 and the other terminal of winding Se is connected to the right-hand terminal of tube Ssby lead 6!. Thus it will be seen that the tubes are connected in series with the secondary windings, this connection giving a circuit of somewhat higher efiiciency than a parallel circuit. It will be observed that in this circuit, as in that of Fig. 4, adjacent tube terminals are always near the same polarity, being connected to corresponding terminals of the secondary windings. The condenser 58 serves the purpose of causing the current in one tube to be out of phase with the current in the other tube and thus to double the number of periods of illumination from the group of tubes in any given time. The tube T5 in series with condenser 58 must be one operating at a lower sustaining voltage than tube T6.

In the circuit of Fig, 6 the primary cormections are the same as those in Fig. 5. The primary winding comprises the coil sections P7 and P3 connected in series and mounted'on core 62 and energized by a source of supply 63 connected through a thermal circuit breaker 64 to the centers of the coil sections. A condenser 65 is connected across the ends of the primary coils to correct the power factor of the primary circuit current.

There are two secondary windings S7 and S8 in the transformer of Fig. 6. Winding S7 is connected thru leads 66 and 61, respectively, to the left-hand ends of the luminescent tubes T7 and T8, a condenser 68 being connected in series in the lead 67 to cause the current in tube T8 to lead that in tube T7. The terminals of windings Se are connected by leads 69 and to the right hand terminals of tubes T7 and T8 respectively. This circuit may be employed where there is little danger of dielectric discharge between the tubes,

' as where they are mounted with a substantial space between their walls or where the operating voltage is low. This series circuit is somewhat more efiicient than a parallel circuit. The tube Ts must be one operating at a lower tube sustaining voltage than tube T7.

Still another manner of connecting the transformer secondary winding is shown in Fig, 7, Mounted on the transformer core H are the primary coils P9 and P10 connected in series and energized from supply 12 which is connected thru the thermal circuit breaker 13 to the centers of the coils. Condenser 14 is connected across their ends to improve the power factor of the primary circuit current.

The one terminals of the secondary windings S9 and S10 are grounded at T5. The other terminal of winding S9 is connected by lead 15 thru condenser T! to one terminal of a luminescent tube T9, whose other end is grounded at 73, completing the circuit. The ungrounded end of winding S10 is likewise connected by lead 19 to one terminal of tube T10, whose other terminal is grounded at 80. The tube T9 which is in series with condenser l1, must be one operating at a lower tube sustaining voltage than tube T10 or secondary winding S9 must be one developing a higher tube sustaining voltage than winding $10. A condenser 8i may be connected between lead 19 and a ground 82 thru a switch 83. This condenser 8! may be used as a starting condenser,

that is, a charge may be built up in it to aid the electromotive force impressed by the winding S10 across the terminals of the tube T10 to strike an arc in the tube when operation of the system is first started. Because of this starting device, the operating voltage of the tube can be reduced to a minimum, with consequent low power consumption and high efficiency.

Thus it will be seen that I have provided a unitary illumination structure and system in which the various objects set forth have been fully accomplished. The unit is compact and therefore can be conveniently handled. Labor charges for installation are low since few steps are involved in setting up the apparatus. For outdoor use, full protection from rain, snow, sleet and the like is provided for the transformer and the high potential leads at a minimum of expense in cost of cables and casings. Many of these advantages also are had in the unit where employed for indoor use. My transformer systems are so designed that there is little objectionable stress between parts of adjacent tubes and hence no dielectric discharges take place between them.

Due to the use of a condenser in the circuit of one tube, that tube becomes illuminated before the other and thus the rate of light pulsations is doubled. Thus any visible flickering or stroboscopic effect is minimized or substantially eliminated, regardless of fluctuations in line voltage, ambient temperature, or current wave form factor.

Where a starting condenser is used, as in Fig. '7, the operating voltage of the circuit is reduced to a minimum, with consequent reduction in power consumption and increased efficiency,

As many possible embodiments may be made of my invention, and asmany changes may be made in the embodiments hereinbefore set forth, it will be nderstood that all matter described-herein or shown in the accompanying drawing is to be interpreted as illustrative and not as a limitation.

I claim:

1. In combination, a transformer having a core with a primary winding and a plurality of secondary windings mounted on the core said secondary windings being symmetrically positioned with respect to said primary winding, a corresponding plurality of gaseous discharge tube loads connected to said secondary windings, a condenser connected across said primary winding, and a source of alternating current supply connected symmetrically across an intermediate portion of said primary winding.

2. In combination, a transformer having a core and a primary and a plurality of secondary windings mounted on the core, a corresponding plurality of gaseous discharge tube loads connected to said secondary windings, a condenser connected in series with one of said secondary windings and its associated tube load for reducing stroboscopic effect of the tube loads, a source of alternating current supply symmetrically connected across a portion only of said primary winding, and a condenser for improving the power factor of transformer and loads connected across substantially the entire primary winding.

3. In combination, a transformer having a core and a primary and plurality of secondary windings mounted on the core, the secondary winding being positioned symmetrically of said primary winding, a plurality of gaseous discharge tube loads corresponding in number to said plurality of secondary windings and individually connected to the same, and a condenser for improving the power factor of the whole connected to outer terminals of the primary winding, said primary winding being provided with intermediate terminals symmetrically of said winding for connection to a source of supply.

CHARLES PHILIPPE BO-UCHER.

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

UNITED STATES PATENTS Name Date Mauerer Sept. 19, 1944 Number Number Number

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