US3372300A - Sequential starting circuit for a pair of fluorescent lamps - Google Patents

Description

March 5, 1968 v SH'UNGO FURUI 3,372,300

SEQUBNTIALSTARTING CIRCUIT FOR A PAIR OF FLUORESCENT LAMPS Filed July 29, 1965 i r YNVENTOR.

My; 6% a /(/a// 520 304 I 64A, 91-4W 305 Arraz/z/zx s United States Patent Ofifice 3,372,300 SEQUENTIAL STARTENG CERCUHT FOR A PAIR SF FLUORESCENT LAMPS Shungo Furui, Yokohama, Japan, assignor of fifty percent to Grace Thunherg, Garden Grove, Calif. Filed July 29, 1965, Ser. No. 475,682 7 Claims. ($1. 315%) ABSTRACT OF THE DISCLOSURE To light tubes are connected in series with a current supply and are lit in sequence during the starting operation. A relatively high resistance is permanently connected across one of the tubes and a glow switch starter is connected across the other of the tubes such that the requirement of a conventional ballast is obviated.

The present invention relates to means and techniques useful in fluorescent tube lighting systems.

Briefly, the arrangements described herein involve two fluorescent light tubes which are lit in sequence during the starting operation using novel circuitry. Using this novel circuitry which involves generally the connection of a relatively high resistance across one of the tubes and the connection of a glow switch starter across the other of the tubes, certain advantages and improved results are obtained. These advantages and new results involve generally more economical operation, not only from the standpoint of cost of initial fabrication, but also in more efiicient use of electrical power during the time when the tubes are fully lit.

It is therefore a general object of the present invention to provide improved means and techniques whereby the above indicated advantages and results may be obtained.

A specific object of the present invention is to provide improved means and techniques whereby the magnitude of the starting voltage may be relatively small, thereby lessening the voltage requirements of the equipment and also lessening the voltage required to be attenuated during the lit condition of the tubes.

Another specific object of the present invention is to provide improved means and techniques of this character whereby relatively small amounts of power are required to be dissipated in a ballast element.

Another specific object of the present invention is to provide improved means and techniques of this character involving the use of two gaseous electric discharge lamps wherein during the starting operation essentially one of the lamps acts as a ballast for the other lamp, with the lamps being sequentially lit.

Another specific object of the present invention is to provide a system of this character using a glow switch star-ter, the malfunctioning of which does not result in flow of excessive currents when, for example, the contact point of the glow switch starter becomes stuck in a circuit closing position, in which case a maximum flow of current is limited to slightly below the normal lamp current.

Another specific object of the present invention is to provide a system of this character in which automatic voltage regulation is obtained by coaction of a series capacitor, characterstics of a transformer and the lamp inductance.

Another specific object of the present invention is to provide a system of this character wherein the components may be made relatively small, of relatively light weight, and with relatively small expense.

While the invention is described specifically in connection with fluorescent tube lights, it Will be understood that the invention in its broader aspect is applicable also 3,372,399 Patented Mar. 5,- 1968 to the control of other devices which exhibit a so-called negative resistance characteristic.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, maybe best understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 illustrates one form of the present invention, and

FIGS. 2, 3 and 4 illustrate other forms of the same invention.

Referring to FIG. 1, the same includes two fluorescent tubes 3 and 4, the tube 3 having cathode filaments 3A, 33 at opposite ends thereof; and likewise, cathode filaments 4A, 4B are at opposite ends of the other light tube 4-. The tube 3 may be provided with an electrostatic shield 9 at ground potential; and likewise, the other tube 4 may be provided with a grounded electrostatic shield 10.

The filament 3A is connected to opposite terminals of a transformer winding 1C. The filaments 3B and 4A are connected in series with a transformer secondary winding 1D; and the other filament 4B is connected across the terminals of transformer secondary winding 1E.

These windings 1C, 1D and 1B are wound on the same core with a tapped winding 1B, the tap 10 being connectable to one terminal of an AC. source 12 through one leg of switch 14. One terminal of coil 1B is connected to one terminal of coil 1C at a junction point 15, the other terminal 16 of coil 1C being connected through a second leg of switch 14 to the other terminal of voltage source 12 which may have one of its terminals grounded. The other outside terminal 18 of coil 1B is connected through a capacitor 2 to one terminal of filament 4B and also to one terminal of a glow starter switch 6, the aforesaid capacitor 2 being shunted by a resistance 7 and the glow starter switch 6 being shunted by a capacitor 8. The other terminal of starter switch 6 is connected to one interconnected terminal of filaments 38, 4A and also is connected through resistance 5 to the previously mentioned terminal 16.

It will be seen from this circuit arrangement that an autotransformer is provided in which the primary winding is essentially that winding 1A between the terminals 10 and i6 and the secondary winding is essentially that winding 1B between terminals 16, 18. All of the windings 1A, 1B, 1C, 1D and 1E are Wound on the same magnetic core.

The glow starter switch 6 is a normally open switch between the contacts of which a gaseous discharge may be produced with the resulting heating of one of the contacts, of bimetal material, causing it to warp and engage the other contact to thereby close the switch. When the switch is thus closed by the heat initially produced by the gaseous discharge between these contacts, the bimetal element is then allowed to cool and in so doing returns to its initial condition and in so doing opens the switch 6.

In the operation of the arrangement shown in FIG- URE 1, when the switch 14 is closed, the transformer 1 is energized and each of the filaments 3A, 3B, 4A and 4B are heated. Simultaneously, a gaseous discharge takes place between the contacts of the starter switch 6 and a bimetal element of the switch begins to warp so as to move towards circuit closing position. During this movement of the switch element of switch 6, neither one of the two tubes 3, 4 is lit. However, when the switch 6 closes, it eifectively short-circuits the tube 4, whereby it no longer acts as a voltage dropping element for tube 3 and the voltage then applied to the tube 3, between the filaments 3A and 3B, causes it to light and thereby decrease the resistance between the tube terminals 20 and 21; and when such resistance between terminals 20 and 21 is thus reduced, the voltage existing between the terminals 21, 22 of tube 4 is sufiiciently high to light the other tube 4. Thus, in this operation the tubes 3 and 4 are sequentially lit, the tube 3 being first lit and the tube 4 thereafter being lit. When the tube 4 is thus lit, its resistance is relatively small and the voltage developed across the same is insufficient to produce a gaseous discharge between the contacts of the glow starter switch 6. Once lit, the lamps 3 and 4 may be extinguished, of course, by opening the switch 14.

In the system shown in FIGURE 1, the starting voltage, ie., the voltage developed across the terminals 15 and 18 is relatively small and may be below 300 volts when the tubes 3 and 4 are of the 80 watt rapid start type fluorescent tube. Typical of circuit values are the following: Capacitors 2 and 8 may be respectively 7.2 microfarads and 0.006 microfarad, the latter capacitor being used essentially for noise suppression. The resistance 7 may have a value of 1 million ohms, i.e., 1 megohm, and the resistance 5 may be of 10,000 ohms. The glow switch starter 6 may be of the FG-4 P or FG-8 P type. The heater windings of the transformer provide approximately 3.6 volts per filament.

It will be seen that the foregoing described sequence of events occurs because of the resistance values in the circuit considerng the fact that in the unlit condition the tubes 3 and 4 have a high resistance or impedance. Thus, the resistance 5 of 10,000 ohms assures an initial discharge between the contacts of the starter switch 6 before any one of the tubes is lit, and when the contacts of switch 6 close, the high resistance offered by the unlit tube 4 is effectively short-circuited thereby allowing a starting voltage to be developed between the terminals 20, 21, and when the tube 3 is lit, its resistance effectively short-circuits the high resistance 5 and thereby transfers a higher starting voltage across the tube terminals 21, 22 ;)f sufiicient intensity to cause the tube 4 to then become In the modified forms of the same invention shown in FIGURES 2, 3 and 4, for purposes of convenience and comparison, corresponding elements are identified by identical reference numerals raised, however, by 100 in FIGURE 2, by 200 in FIGURE 3, and by 300 in FIG- URE 4.

It will be seen from FIGURE 2 that the heater winding corresponding to 1B in FIGURE 1 is omitted, and in this case the filaments 104A and 104B are heated in a different manner, i.e., by the current flowing through the glow starter switch 106. The heater windings 101C and 101D are connected respectively to the filaments 103A and 103B. The filaments 104A and 104B are now connected in a series circuit with the glow starter switch 106, such series circuit extending from the terminal 118, through capacitor 102, through filament 104B, through switch 106, through filament 104A, through resistance 105, to terminal 116 and through the transformer windings 101C and 101B.

The operation in FIGURE 2 is essentially as described above in connection with FIGURE 1. When the switch 114 is closed, the filaments 103A and 1033 are heated and a glow discharge appears in switch 106 causing a heating of a bimetal element which then moves towards circuit closing position, and when the switch 106 is thus closed, an increased voltage appears across tube 103 to cause it to ignite. The switch contacts 106 then cool and open, and when the switch 106 is then opened, a sufficiently high voltage appears across the tube 104 to then ignite it. As a result, both tubes 103 and 104 are ignited and there is insuflicient voltage developed across the switch 106 to produce a glow discharge therein.

The arrangement shown in FIGURE 3 is essentially the same as in FIGURE 2. In this case, the transformer secondary winding 201D supplies heating current to each 4. of the heaters 203B and 204A which are connected in parallel with each other, and Only the filament 2043 is heated by the discharge current flowing through glow starter switch 206.

In the arrangement shown in FIGURE 4, the secondary heater winding 301D has its opposite terminals connected to opposite terminals of the filament 30313. The filament 304B has its opposite terminals connected to opposite terminals of the secondary winding 361E. In this case, the discharge current which flows through the switch 306 flows through the filament 304A and also the filament 303B to supplement the heating efiect produced by the current from the secondary winding 301D.

The operation in each of the four disclosed embodiments are essentially the same, with closure of the line switch resulting in the sequence of operations described above which are in general: closure of such line switch results in heating of the filaments of the tube 3 and simultaneous production of a discharge current through the switch 6. When the switch 6 closes as a result of heating of one of its bimetal contacts, a relatively high voltage is applied to the tube 3 to cause it to ignite. After the switch 6 cools and reopens, a relatively high voltage then appears across tube 4 to cause it to ignite with the result that both tubes 3 and 4 are then ignited.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

I claim:

1. In a fiuorescent tube lighting system, a first fluorescent tube; a second fluorescent tube; each of said tubes having filamentary cathodes; means for heating said cathodes; a first impedance element permanently connected in parallel with said first tube; a glow starter switch connected in parallel with said second tube; said glow starter switch being a normally open switch and incorporating means whereby heat from a glow discharge in said starter switch causes said switch to close; a voltage souce; a second impedance element; said voltage source, second impedance element and said first and second tubes being connected in a series circuit; means for energizing said voltage source and said cathode heating means; said first impedance element being effective to prevent lighting of said first tube when said voltage source is initially energized by said energizing means with said first impedance element being effective to cause a glow discharge to appear in said starter switch; said starter switch being closed by the heat produced by said glow discharge therein to bypass said second tube and apply a higher voltage to said first tube to cause it to light; said first tube when thus lit being efiective to cause a higher voltage to be developed across said second tube to cause said second tube to light.

2. A system as set forth in claim 1, in which said first impedance element comprises a resistance.

3. A system as set forth in claim 1, in which said second impedance element comprises a capacitor shunted by a resistance.

4. A system as set forth in claim 1, in which said glow starte switch is shunted by a capacitor.

5. A system as set forth in claim 1, in which at least one of said cathodes is connected in series with said glow starter switch.

6. In a system of the character described, a first discharge device; a second discharge device; a first impedance element permanently connected in parallel with said first discharge device; a glow starter switch connected in parallel with said second discharge device; a second impedance element; a transformer winding; a series circuit which includes said transformer winding, said second impedance element and said first and second discharge devices; said first impedance element being of sufiicient magnitude such that when said transformer winding is initially energized said first impedance element prevents a discharge from appearing in said second discharge device and causes a glow discharge to appear in said starter switch; said starter switch incorporating means whereby the heat produced by said glow discharge therein causes said switch to close and thereby effectively short-circuit said second discharge device and cause a discharge in said first device; said first device, when a discharge appears therein, being of sufiiciently low resistance to then cause the production of a discharge in said second device.

7. In a system of the character described, a first discharge device; a second discharge device; a first impedanme element permanently connected in shunt with said first device; a glow starter switch connected in shunt with said second device; a second impedance element; a source of current; said source, first device, second device and second impedance element being connected in a series circuit; said source developing a voltage insufficient to initiate a discharge in said first and second devices simultaneously; said first impedance element being of sufiiciently large magnitude to produce a glow in said starter switch; said starter switch incorporating means whereby the heat produced by said glow causes the switch to close and eifectively short-circuit said second device in which case the voltage developed across said first device is sufiicient to initiate a discharge in said first device; said first device, when said discharge is developed therein, being effective to initiate a discharge in said second device and to prevent a glow discharge in said switch whereby said switch may remain in an open position with said effective shortcircuit removed from said second device whereby a discharge may be continued to be developed in said second device.

References Cited UNITED STATES PATENTS DAVID J. GALVIN, Primary Examiner.

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