US2317845A - Luminescent tube lighting apparatus - Google Patents

Description

April 27, 1943. c. P. BOUCHER 2,317,845

LUMINESCENT TUBE LIGHTING APPARATUS Filed Aug. 21, 1940 2 Sheets-Sheet 1 69242-266 Pfioacar April 1943- c. P. BOUCHER 2,317,845

LUMINESCENT TUBE LIGHTING APPARATUS Filed Aug. 21, 1940 2 Sheets-Sheet 2 AM 4 7 A a 45 f u no-uuu 46 J Y Jg 419 fil J] L Q74 J9 J6 Jfi l'um v .0000. J7 6] Patented Apr. 27, 1943 LUMINESCENT TUBE LIGHTING APPARATUS Charles Philippe Boucher, Paterson, N. J., as-

signor to Boucher Inventions, Ltd., Washington, D. 0., a corporation of Delaware Application August 21, 1940, Serial No. 353,572 Claims. (CL 176-124) This invention relates to electrical transformers for energizing luminescent tube systems suitable for the illumination of signs or displays 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 luminescent tube lighting apparatus such that all the parts are assembled in a compact unit.

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

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

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

The invention accordingly consists in the combination 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 drawings illustrating certain features of my invention:

Figure 1 represents a sectional plan view of a luminescent tube lighting unit including the transformer and the luminescent tubes.

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

Figure 3 is an enlarged vertical section on the line 3-3 of Fig. 1, showing details of the transformer.

Figures 4, 5, 6 and 7 are diagrams of various circuits which may be employed.

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

As conducive to a clearer understanding of the nature of my invention, it may be noted at this point that, for example, in the illumination of a sign or display, employing for that purpose one or more luminescent tubes as a source of light, one or more high potential electrical transformers are required. These transformers have heretofore been mounted in a protected place either inside a building or in a casing separate from the luminescent tubes for lighting the sign or display structure, thus necessitating long high-tension cables and requiring several steps to be taken in fastening the parts in place and in making electrical connections. It is apparent that 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 objects of my invention.

In heretofore known luminescent systems for signs or 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 (SO-cycle source of electrical energy is used, the tubes become luminous 120 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 noticeable, particularly where the tubes are mounted in a group in front of the same reflector. This phenomenon is called a stroboscopic efiect and is especially noticeable when the operation of the tubes is affected by variations in the voltage impressed across their terminals and in the wave form factor of the current. 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 they are spaced apart in order to avoid dielectric discharges between them. This spacing is undesirable because it exaggerates the flickering effect described above. Moreover, it reduces the concentration of light from the tubes and thus makes them less satisfactory for illumination purposes.

In luminescent tube systems now in use, it is necessary to employ high voltage to initiate operation of the tubes. 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 and a correspondingly lower efficiency and a high maintenance cost.

Accordingly, another object of my inventionis the provision of a compact, rugged and efficient luminescent tube lighting unit of reduced stroboscopic effect, gOOd and uniform light intensity and, moreover, of good operating power factor ing.

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 haveshown illustratively a casing and reflector ill in which are mounted two luminescent tubes H and I2. These tubes are energized by a transformer i3 which is housed in transformer compartment Ila. of an enclosure l4, also having a condenser compartment Hlb, the enclosure being attached to the rear of the reflector [0, as by bolts I5. Lugs it are provided on the enclosure M for supporting the whole casing structure.

Tubes II and H are supported at their ends in porcelain housings l! by spring clamps it, which make firm electrical contacts with the tube terminals. The porcelain housings H are secured in place in the casing by screws It, further insulation of the tube terminals from the metal of the casing i ll being provided by spacers of insulating material. Porcelain cover plates 2i are placed over the front apertures of the housings ll when the tubes are in position. The

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 35, 3t, 32 and 33 are fitted over the shunt parts 28 and 29 to prevent their laminations from chattering. Shunt pieces 36 and are interposed between the shunt parts 28 and 29 and the core members 24 and 25 at their centers and insulating blocks 35, 37, 38 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 parts are held in place by clamps 4B and M which are tightened by the bolt and nut 42. The transformer is maintained in a proper position in its casing Ma by spacers c3 and 44 of non-magnetic material which fit over the core bands 26 and 21.

Referring now to 4, there is diagrammatically represented one circuit which may be used in the transformer and tube system of 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, coreand coils are mounted within the transformer compartoperation, here again it will be understood that 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 Ta 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 I 20 to 240 times per second. Thus the fiickering which is frequently noticeable in the ordinary 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 terminals are always at potentials of about the same value since they are connected to corresponding terminals of their secondary windings, any difference being due to phase displacement by the condenser. Thus the left-hand terminals of tubes Ta and T4 are shown at one instant as being connected to the positive terminals of the windings Sc and Sr and 'the right-hand terminals of the tubes are connected to the negative ends of the secondary windings. Being always at about 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.

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 54 are of the same voltage rating during the conductive periods of the tubes the tube T3 must be one operating at a lower voltage than tube Ta. Thus tube T3 may be of larger diameter than tube T4 or it may be one having electrodes of lower resistance. Tube Ta may also operate at a lower voltage than tube T4 because it contains a difierent 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 now another circuit embodying my invention, attention is directed to Fig. 5 in which I show a transformer comprising a core 53, a primary winding consisting of two coil sections P5 and P5 connected in series, and two secondary windings S5 and S6. The central points of the primary winding sections are connected thru a thermal circuit breaker 54 to an alternator or other source of alternating current supply 55. A condenser 56 is connected across the outer terminals of the primary coil sections. The function of this condenser is to improve the power ment of the lighting structure. Their outer terprimary winding exceeds a value corresponding to the maximum safe load of the primary wind- There are two secondary windings: and Si energizing the tubes T3 and T4, respectively, by way of leads 48, 49, 50 and St. A condenser 52 is connected in series with one of the tubes as by connecting it'in the lead 69 to the tube T3. In

*factor of the primary circuit. Inasmuch as the the right-hand terminal of tube Te by the lead.

59. Likewise, one terminal of winding S6 is connected to the left-hand terminal of tube Ts by the lead 68 and the other terminal of winding Se is connected to the right-hand terminal of tube S5 by lead 6i. Thus it will be seen that the tubes are connected in series with the secondary windings, this connection giving a circuit of somewhat higher eillciency than a parallel circuit. It will be observed that in this circuit, as in that of Fig. 4, adjacent tube terminals are always near theisame 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 T in series with condenser 58 must be one operating at a lower sustaining voltage than tube T0.

In the circuit of Fig. 6-the primary connections are the same as those in Fig. 5. The primary winding comprises the coil sections P1 and Pa connected in series and mounted on core 62 and energized by an alternator or other source of supply 63 connected through a thermal circuit breaker 64 to the center; 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 S1 and S3 in the transformer of Fig, 6. Winding S1 'is connected thru leads 66 and 61, respectively, to the left-hand ends of the luminescent tubes T1 and Ta, a condenser 68 being connected in series in the lead 6! to cause the current in tube T8 to lead that in tube T1. The terminals of windings S8 are connected by leads 69 and to the right hand terminals of tubes T1 and Ta 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 eificient than a parallel circuit. The tube To mustbe 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 the alternator or other source of supply "which is connected thru the thermal circuit breaker 13 to the centers of the coils. Condenser M 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 15. The other terminal of winding S9 is connected by lead 16 thru condenser 11 to one terminal of a luminescent tube T9, whose other end is grounded at 18, 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 Ta which is in series with condenser 11, 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 S10. A condenser 8| may be connected between lead 19 and aground 82 thru a switch 83. This condenser 8l 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 tube T10 to strike an arc in the tube when operation of the system is first started. Because ofthis starting device, the operating voltage of the tube can be reduced to a minimum, with consequent low power consumption and high eificiency.

Thus it will be seen that I have provided a 3 unitary luminescent tube lighting structure and I system in which the various objects set forth have been fully accomplished. The unit is compact and thereforacan 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 advant is 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 double. 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 efliciency.

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

I claim:

1. In a luminescent tube lighting system, the combination of a transformer having a plurality of secondary coil sections, a plurality of closely adjacent substantially parallel luminescent tube loads individually connected to individual secondary coil sections, condenser means included in the circuit of at least one of said tube loads and secondary coil sections for limiting current and for reducing stroboscopic effect, magnetic shunt means around at least one other of said secondary coil sections for limiting the current therein, and a reflector disposed adjacent said tubes.

2. In a luminescent tube lighting system, the combination of a. fixture having a reflector and a. housing mounted on the same, a transformer positioned within the housing and having a primary winding and a plurality of secondary coil sections, a plurality of luminescent tube loads mounted in the reflector and individually connected to individual secondary coil sections, condenser means positioned within the housing adjacent the transformer and included in the circuit of at least one of said tube loads and secondary coil sections for limiting current and for reducing stroboscopic effect, said transformer including magnetic shunt means to limit the current in at least one other. secondary coil section.

3. In luminescent tube lighting apparatus, the combination of a fixture including a reflector and a housing having transformer and condenser compartments, two luminescent tube loads mounted in the fixture in front of said reflector, a transformer housed in said transformer compartment and having two secondary coil sections individually connected with said tubes, and condenser means in said condenser compartment and included in the circuit of one of said tubes and secondary coil sect ions, said transform includind magnetic shunt means around at least the other secondary coil section for limiting the current therein.

4. In combination, a metallic housing including a. transformer compartment and a condenser compartment, a transformer housed within the transformer compartnnent and. having a core and a primary winding and a. plurality of secondary coil sections positioned ,o'n the core, a corresponding plurality of luminescent tube loads individually connected to individual secondary coil sections, condenser means housed within the condenser compartment of said housing and included in the circuit of at least one of said .tube

, loads and secondary coil sections, and magnetic core shunt means around-at least one other of said secondary coil sections for limiting thecurrent therein.

, 2,817,846 ,5. In combination, a metallic housing havin a transformer compartment and a condenser compartment, a metallic fixture on which said housing is mounted, said fixture including a re- CHARLES PHILIPPE BOUCHER

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