US2918605A - Starting and operating fluorescent lamps in series - Google Patents

Description

Dec. 22, 1959 w. s. H. HAMILTON STARTING AND OPERATING FLUORESCENT LAMPS IN SERIES Filed May 3, 1956 3 Sheets-Sheet l INVENTOR WILLIAM s. H. HAMILTON "Pavia f /'61 ATTORNEYS Dec. 22, 1959 w. s. H. HAMILTON STARTING AND OPERATING FLUORESCENT LAMPS IN SERIES Filed May 5, 1956 3 Sheets-Sheet 2 max/ 1 ATTORNEYS INVENTOR WILLlAM S. H. HAMILTON Dec. 22, 1959 w. s. H. HAMILTON STARTING AND OPERATING FLUORESCENT LAMPS IN SERIES Filed May 3, 1956 3 Sheets-Sheet 3 INVENTOR WILLIAM H. HAMILTON HIS AT STARTING AND OPERATING FLUORESCENT LAMPS IN SERIES William S. H. Hamilton, Larchmont, N.Y.

Application May 3, 1956, Serial No. 582,399

20 Claims. (Cl. 315-97) This invention relates to the starting of gaseous electric discharge devices, such as fluorescent lamps, particularly of the type which start as cold cathode lamps and operate with hot cathodes and which are known as Slimline lamps, and the operation thereof in series from supply circuitsof various characters. Because of their rugged filament construction and freedom from end blackening, these lamps are preferred to other fluorescent lamps for certain kinds of service. Although the system of my present invention for starting and operating discharge devices may be used with alternating current supply circuits, it is intended especially for use with continuous or direct current supply circuits of fixed or reversible polarity. Thus my present system is well adapted for use on multiple unit railroad cars and on street cars and trolley buses where the operating voltage may vary over a wide range such, for example, as from 450 to 750 volts. Also in the case of trolley buses, the polarity of the supply is reversed whenever the bus has to operate from the pair of trolley feed wires on the opposite side of the street and normally used by buses traveling in the opposite direction.

Fluorescent lamps of the Slimline type are distinguished from the preheated or hot cathode starting type by having only one terminal pin at each end of the lamp, whereas the preheated or hot cathode starting type has two terminal pins at each end. The electrodes of Slimline lamps are heated by the operating current flowing through the lamp after it has been started, and these lamps are provided with filamentary electrodes, which are readily heated by the lamp current. Both terminals of each electrode are, however, connected to the single lamp terminal pin, thereby short circuiting the electrode. Such lamps require a comparatively high voltage surge or kick to fire them, and where the length of lamp is selected for proper ballasting and efiiciency of operation at the minimum line voltage of a given supply circuit, it would be impossible to fire all of the lamps if connected in series, when starting cold, unless recourse should be had to auxiliary devices such as high frequency generators or very highly inductive devices or reactor-transformers.

The major purpose or object of the present invention is, therefore, to provide a system for starting a plurality of fluorescent lamps of the Slimline type and for operating them in series connection from the supply line.

Another object of the invention is to provide a system of this kind which, because of its simplicity, requires a minimum of auxiliary equipment, such as relays, inductive devices, resistors, safety devices, etc.

Another object of the invention is to provide a system of the kind referred to which will operate from a supply source or line, the polarity of which may be reversed under certain operating conditions.

The hot cathode starting type of fluorescent lamp toward the end of its life shows a conspicuous yellow color which is an indication that the lamp filaments are becoming deactivated of their electron emitting compound United States Patent and that consequently the lamp may soon become inoperable. However, with the Slimline type of lamp there is no Way of detecting whether the filaments are deactivated or broken, either of which conditions would prevent the lamp from starting. An attempt to start such a lamp produces chattering of the starting relay which fires the lamp, and with the high peak voltages required to start the Slimline type of lamp, the relay .contacts can be damaged if the chattering is prolonged.

Accordingly, a further object of the invention is to provide protection against such relay damage in the case of a lamp, or lamps, which will not start.

In accordance with my present invention, a plurality of Slimline lamps, from two in number to any desired number, depending on the voltage of the supply line and the length of lamp it is desired to use, is divided into groups, sections or portions, each consisting of one, two, three or more lamps, depending upon the voltage available and the length of lamp chosen. Then each of these portions, groups or sections of lamps is connected in a starting circuit of its own in series with a suitable ballast lamp and resistor, to limit the starting current to the desired value, and including appropriate starting devices, such as an inductive device and a by-pass circuit around the lamp or lamps. Current is fed through all of these starting circuits in parallel from the supply line, and the by-pass circuit is opened to fire the lamp, or lamps, in each of these starting circuits. Thereupon the several lamp groups are reconnected in series between the opposite sides of the supply circuit, but, of course, in series with one of the ballast lamps.

The are voltage of the lamp, or lamps, in each of the starting circuits is low compared to the supply line voltage, and the lamps are started quickly and without difficulty; then they are placed all in series across the supply line for eflicient operation. The transfer of the operation from parallel to series connection takes place upon the completionof the firing of the lamps in each of the individual parallel starting circuits. All the lamps are held in series operation as long as the line circuit remains closed.

In accordance with the invention, any two of the parallel starting circuits may be considered to be arranged as an unbalanced Wheatstone bridge circuit, with the positions of the lamps reversed in the two arms of such circuit. That is to say, starting from one side of the supply line, the current flow in one of the arms of the Wheatstone bridge is first through a ballast lamp, then through one or more fluorescent lamps (in series connection in case there is more than one lamp), thence through a resistance or resistor, thence through an inductive device to the opposite side of the supply line. On the other hand, in the other arm of the Wheatstone bridge circuit, the current flows first through a second ballast lamp, thence through an inductive device and a resistor in series connection, thence through the one or more fluorescent lamps constituting the second group, and thence to the opposite side of the supply circuit.

The value of the resistances in the two arms, or starting circuits, while of the same order in both arms, may be somewhat greater or somewhat less in the second starting circuit, depending on the length and diameter of the fluorescent lamps used, so that, over the entire line voltage range through which the circuit has to operate there will be, after the lamps have fired, a voltage drop between the approximate mid points of each of the two arms suflicient to actuate a relay whose coil is connected between these mid points.

The invention will be further understood by considering the circuits shown in the accompanying drawings and the following detailed description thereof. In these drawlugs:

Fig. 1 shows .a circuit wherein four lamps are to be operated in series, and wherein each of the two starting circuits comprises a group of two lamps in series;

Fig. 1a is a-diagrammatic detail showing the electrode 'and terminal construction of one end of a lamp;

Fig. '2'shows a circuit similar to Fig. 1 where the lamp 'groups in the two starting circuits are unequal in number, two lamps being shown in the upper or first starting circuit and a single lamp in the second or lower starting circuit whereby an odd number of lamps may be operated" in series;

Fig. 3 shows the circuit connections for starting and for operating six lamps in series, these being divided into threeequal groups of two lamps each;

Fig. 4 shows a circuit which is similar to that of Fig. 1, hut in which an additional safety device is included; and

"Fig. shows a circuit which is also substantially like that of Fig. 1, but including a different form of additional safety device.

Referring first to Fig. 1a, the Slimline type of lamp comprises the usual tubular envelope ll of glass having a -re-entrant stem 2 through which the lead-in wires 3 extend. These wires support a filamentary electrode 4 bet-ween their inner ends and are both connected to a sineg'le pin or contact 5 which is appropriately mounted on =the end of the lamp. Lamps of this type are made in a variety of sizes to meet different situations and vary in diameter from A of an inch to 1 /2 inches, and in length from about 36 inches to about 96 inches. The voltage *drop across a 36 inch lamp 1 /2 inches in diameter is approximately 85 volts when the lamp is in operation. In "order to start such a lamp, however, a voltage in the neighborhood of 450 volts must be impressed across the electrodes. The operating and starting voltages of lamps 'Of the other sizes vary from these figures. With a given supply line voltage for a particular installation, lamps of appropriate length may be chosen, and the number of such lamps necessary for eflicient operation in series may 'also'be decided upon.

In Fig. 1, as well as in all of the remaining figures, the supply line conductors are indicated by B and W, inas- "much as the supply circuit may be either a direct current circuit of reversible or fixed polarity, or an alternating current circuit. It will be understood that the conductors 11B and W are connected with a control switch (not shown) for turning the lamps on and off.

Fig. 1 shows a representative circuit wherein four lamps, designated L1, L2, L3 and L4, can be operated in series from a direct current railroad or trolley bus cir- "cuit where the supply voltage may vary from about 450 to about 750 volts. Lamps L1 and L2 constitute the lamp group which is included in the starting circuit shown at the upper part of Fig. 1, and lamps L3 and L4 are in the starting circuit shown at the lower part of this figure.

Lamps L1 and L2 are mounted in a fixture which is provided with double spring contacts 6 and 7 adapted to resiliently engage opposite sides of the terminal pin 5 at'th'e right end of the lamp. At the center of the fixture 'thereare two spring contacts 8 and 9 which are electrically joined together as shown, and which engage, re-

spective'ly, the left contact pin of lamp Ll and the right contact of lamp L2. At the left of the fixture there are two more spring contact fingers l0 and 111 which engage the opposite sides of the left contact pin for lamp L2. The lams L3 and L4 are mounted in a fixture having "the same contact arrangement, the respective contacts being indicated by the same reference numerals using the subscript a. With this arrangement the lamps L1 and L2 are placed in series connection with each other, and the lamps L3 and L4 are similarly connected.

Referring particularly to the upper starting circuit of Fig. l, a ballast lamp BL1 is connected with supply line terminal B and through a conductor 12 feeds current to "contact 6 of lamp L1. Contact at the left of lamp L2 is connected to the operating coil of a starting relay 13, which also operates as a transfer initiating or partial bridging relay. This relay has two sets of contacts, a normally closed set of lamp starting contacts 14 and a normally open set 15 of bridging circuit connecting contacts, which will be referred to later.

As shown here and throughout the drawings, dotted lines are employed to join each relay operating coil with the set, or sets, of relay switch contacts that are operated by it. Also are suppressing condensers C are connected across all relay contacts in all figures.

To complete the upper-starting circuit, the operating coil of relay 13 is connected through a conductor 16 to a set of normally closed relay contacts 17 of a transfer, or transfer completing relay whose operating coil is indicated at 18, and which also has a escond set of normally closed contacts 19 in the lower starting circuit to be referred to later. The circuit from contacts 17 continues through a wire 20, a resistance 21, a wire 22 and a reactor or inductive device 23, to the opposite side W of the supply line.

A by-pass circuit is arranged around the lamps L1 and L2 comprising a wire 24 from spring connector 7 to a safety device 25 which advantageously may be in the form of a delayed action fuse, the operation of which will be referred to later on. The by-pass circuit continues from this fuse through a wire 26 to the set of relay contacts 14 and thence through a wire'27 to spring contact lll at the left end of lamp L2. This by-pass circuit is opened to start lamps L1 and L2 by the opening of contacts 14 as will be later described.

The lower starting circuit of Pig. 1 is fed by a conductor 28 which connects supply line terminal B with a second ballast lamp BL2. The general arrangement of the parts of this lower starting circuit from here on is reversed with respect to the upper starting circuit. That is to say, the lower circuit is to be traced first through the inductance and resistance and then through the lamps. Accordingly a wire 29 connects ballast lamp BL-2 with inductive device 23a and the circuit continues through a wire 22a to resistance 21a and thence through a wire 20a to the set of transfer relay contacts 19. The circuit continues through wire 39 to the operating coil of lower starting relay 13a, then by a wire 31 to spring contact 6a at the right end of lamp L3. The contact 10a at the left end of lamp L4 is connected to supply line terminal W by a. conductor 32.

A by-pass circuit, similar to the one previously described, is connected between the spring contact 711 at the right end of lamp L3 and contact 11a at the left end of lamp L4 so as to bypass these lamps for the starting operation. This circuit comprises a wire 33 to the set of starting relay contacts 14a and thence through wire 34 to a safety device 25a which as before may advantageously be in the form of a delayed action fuse. The circuit continues through wire 35 to spring contact 11a.

Starting relay 13a, like relay 13, is provided with two sets of contacts, the starting contacts 14a just referred to, and bridgin or reconnecting contacts 15a which will be referred to presently.

The transfer of the lamps Lil-L4 from parallel connection for starting to series connection for normal or continuous operation is accomplished by establishing a transfer or bridge circuit and then opening contacts 17 and 19 to complete the transfer. This bridge circuit extends from what may be considered as the mid-point of the upper starting circuit to a similar point in the lower starting circuit. The point in the upper starting circuit is designated as D in conductor 16 which joins the operating coil of starting relay 13 with the contact 17 of transfer relay 1%. In the lower'circuit this point is designated as E and is in conductor 30 which is between the transfer relay contacts .19 and the operating coil of starting ..relay 13a.

lamp, resistance and inductance.

This transfer or bridge circuit, starting at the point D comprises a wire 36 to relay contacts 15. Wire 37 joins these contacts with the operating coil of the transfer relay 18 and the circuit proceeds through a wire 38 to relay contacts a, these being the second set of contacts on the lower starting relay 13a. A wire 39 joins these contacts with the point E.

The two parallel starting circuits described may be considered as constituting a WheatstOne bridge circuit in which the upper starting circuit constitutes one arm and the lower starting circuit the other arm, the bridge circuit extending between the points D and E. The purpose of the resistances 21 and 21a is twofold. In the first place, they limit the starting current in their respective starting circuits. Their second function is to insure that, even with the supply line voltage dropping to as low as 450 volts or less, there will be an adequate potential difference, between the points D and E, to operate transfer relay 18. To carry out this function, although both resistances are of the same order, one or the other may have a higher value.

The operation of the circuit shown in Fig. 1 will now be described. Upon the closing of the line switch which energizes the supply line terminals B and W, current flows simultaneously through the upper and lower starting circuits, the current flowing through the bypass circuits described, namely, through the by-pass circuit including the starting relay contacts 14 for lamps L1 and L2 and the by-pass circuit including the starting relay contacts 14a of the starting relay 1312. These by-pass circuits cause theoperating coils of the two starting relays 13 and 13a to be energized.

Starting relay 13 thus opens the starting contacts 14 to produce an inductive voltage surge, impulse or kick across the-terminals of lamps L1 and L2 in series, such surge being produced by the presence of the inductive device 23 in this circuit.

In the lower starting circuit the simultaneous energization of relay coil 13:: causes the opening of starting contacts 14a and the starting of lamps L3 and L4 by an inductive voltage kick produced by inductive device 23a.

Should the lamps not start at the first opening of the by-pass circuits by contacts 14 and 14a, the current will be reestablished in the respective operating coils, and a rapid vibration of the contacts will be produced until the lamps fire, or the safety device (or 25a) operates, as will be referred to presently. Because of the rapid opening of the starting contacts 14, the inductance of each of the devices 23 and 23a is relatively small. This, of course, also applies to the corresponding inductive devices shown in the remaining figures of the drawings.

With the opening of starting contacts 14 and 14a, the second sets of relay contacts 15 and 15a actuated by the starting relays 13 and 13a are closed. Ordinarily these relays will close substantially simultaneously, butshould they not so operate, the circuits of both groups of lamps will operate temporarily in parallel connection across the supply line, each group being in series with its ballast However, as soon as both circuits are closed the bridge circuit is completed. This prepares for the transfer of the lamps from parallel to series operation and also energizes the operating coil of transfer relay 18 by which such transfer is completed. The energization of coil 18 of the transfer relay causes both sets of normally closed contacts 17 and 19 to open. The opening of contacts 17 breaks the upper lamp circuit between the operating coil of starting relay 13 and the resistance 21. Similarly the opening of contacts 19 breaks the lower lamp circuit between the operating coil of relay 13a and resistance 21a. Lamps L1-L4 now operate in series, ballast lamp BL-1 being retained in the circuit.

The operating coils of relays 13 and 13a as well as the operating coil of transfer relay 18 are held in series connection-with each other and with the lamps 1.1-1.4.

The operating current of the lamps maintains all three of these coils energized so long as the lamps are continued in operation. When, however, the lamp control switch is opened, all three relays return their contacts to the original positions, so that the lamps are ready to be started immediately by reclosing the control switch, if desired.

The circuit of Fig. 1 has been described in connection with the operation of four lamps in series as shown. However under different conditions, such for example, as a different direct current operating voltage or an alternating current supply, it might be desirable to operate only two lamps in series, instead of four. In that case, it will be understood that a single lamp of any suitable length may be substituted in plac: of the two lamps L1 and L2 in the circuit of Fig. 1, and a second single lamp substituted in place of the two lamps L3 and L4. Obviously this would require somewhat different fixtures.

The circuit arrangement as shown in Fig. 1 would remain the same, except for whatever changes might be required in the sizes of resistances 21 and 21a. With such a substitution of lamps, the single lamp in the upper starting circuit would be started by the opening of relay contacts 14, and the single lamp in the lower starting circuit by the opening of relay contacts 14a. The closing of relay contacts 15 and 15a would cause operation of relay 18 in the same manner as previously described.

Referring now to Fig. 2 this circuit shows the starting of an odd number of lamps, in this case two lamps L1 and L2, in the upper starting circuit and only a single lamp L3 in the lower. The starting and operating circuit connections are identical with those described in connection with Fig. 1 except for the fact that the value of resistance 21b in the lower starting circuit is higher than the value of resistance 21a in Fig. 1. This is necessary in order to limit the operating current through the single lamp L3 to a proper value during starting, or in case either of lamps L1 or L2 should become defective, which might require the operation of lamp L3 by itself for a considerable period of time.

In connection with this feature of my circuit arrangements, in the circuits of both Figs. 1 and 2,. and, for that matter, in the circuits of the remaining figures, should a lamp in one of the two starting circuits become defective and refuse to start it may be removed and the lamps in the remaining circuit retained in operation. Thus, for example, supposing the lamp L2 in either Figs. 1 or 2 should refuse to start, the removal of this lamp will break the upper starting circuit inasmuch as the connection pin 5 at its left end serves to interconnect the two contacts 10 and 11, and when this pin is removed, these contacts will not touch each other.

Should one of the lamps, for example lamp L1, be defective and inoperable at the time the lamps are turned on, the lamp will not fire, and relay contacts 14 .will open and close rapidly as previously explained with chattering and injurious arcing. If this continues for a few seconds, however, the delayed action fuse 25 (or 25 1 in the case of one of the lamps in the lower circuit) will blow. This .opens the by-pass circuit so that no current will flow through the particular starting circuit. The remaining lamp or lamps, however, will operate, so that light (in lesser amount) will be available until the defective lamp can be replaced.

The normal starting of a lamp takes place so quickly that many successive starts may be made without blowing a delayed action fuse. Should a lamp filament break in service, or should deactivation of a lamp filament take place and this condition has progressed far enough so that the starting relay has to make a considerable number of attempts to start the lamp, the delayed action fuse will blow.

It will be understood that although these fuses 25 and 25a have been shown only in Fig. 1, they can be in- Z? eluded in the circuits of any of the other figures. if des'ired.

It was mentioned above that the circuit of Fig. 1 may be utilized for operating two lamps in series instead of the four lamps shown. This circuit may also be used where it is desired to operate a larger number of lamps in series, for example, six lamps with three lamps in series in each of the starting circuits, or eight lamps in series, with four lamps in series in each of the starting circuits. However, whether or not it is feasible to operate six or more lamps in series using the two starting circuits of Fig. 1 will depend upon the ease with which the particular lamps will start, and the voltage of the supply circuit available.

In Fig. 3 there is shown a circuit for starting six lamps which includes three starting circuits instead of two, and such a circuit arrangement is desirable for lamps that have relatively hard starting characteristics and which might not properly respond to starting with three in series, as just mentioned.

Referring to Fig. 3, the top and bottom starting circuits are individually identical with the upper and lower starting circuits of Fig. l, but the middle starting circuit differs in several respects. Thus in the top starting circuit of Fig. 3 the two lamps L1 and L2 are connected in series with each other and are fed from ballast lamp BL-1. They are also in series with the operating coil of starting relay 13 and with contacts 17 of the transfer relay 18 and with resistance 21 and inductive device 23. The opening of contacts 14 starts lamps L1 and L2, and the simultaneous closing of contacts 15 partially closes the bridge circuit between point D in the top starting circuit and point B of the middle starting circuit.

Similar y the bottom starting circuit is fed through ballast lamp BL-2 through conductor 28 and a conductor 40. In this circuit, in series connection are the inductance device 23a, resistance 21c, the normally closed contacts 41 of a transfer relay 42 (which also has a normally closed set of contacts 43 to be referred to later), the operating coil of the starting relay 13a, and the lamps L and L6. This circuit continues to a conductor 44, conductor 32 and to the opposite side W of the supply line.

This bottom starting circuit operates in the same way as the top circuit so that when the lamps are turned on current flows through inductance 23a, resistance 21c, contacts 41, relay coil 13a, and the starting contacts 14a in the bypass circuit. Tie energization of coil 13a immediately opens contacts Ma and starts the two lamps L5 and L6, simultaneously closing contacts a which, like contacts 15, serve to initiate the transfer from parallel to series by partially closing a bridge circuit. The bridge circuit in this instance is from point F in the middle starting circuit to point G in the bottom starting circuit.

One of the differences between the middle starting circuit of Fig. 3 and the upper starting circuit of Fi l is that the combined starting and transfer initiating relay 13b, the coil of which is included in this middle circuit, is provided with three sets of contacts instead of two. These three sets of contacts are the normally closed starting contacts ll lb and the two sets of normally open contacts 1% and 4-5, contacts 45 therefore being an extra set of contacts. A second diiierence in the middle starting circuit is the division of the resistance into two sections, namely, resistance :5 between the ballast lamp BL 3 and relay contacts 1 .9, and resistance 21d. The purpose of this division will appear presently. Resistance 21d and inductive device 23.5 are between lamps L3 and L4 and conductor 32.

The starting circuit through these two lamps is therefore from the ballast lamp BL3, through resistance 46, relay contacts 19, wire 47, the bypass circuit including starting contacts 14b, the operating coil of relay 13b, relay contacts 43, resistance Z-lld, and inductive device 232, back to the supply line terminal W through wire 52. The energization of relay l-ZSb-opens' the s'tartinglconltacts 14b and starts the lamps L3 and L4.

Simultaneously the contacts 151) and 45 of this relay are closed and this completes the two bridge circuits, namely, the upper bridge circuit from point D in the top starting circuit to point E in the middle starting circuit, and the lower bridge circuit from point F in the middle starting circuit to point G in the bottom starting circuit. The operating coils of both of the transfer relays 18 and 4:. are now energized, inasmuch as contacts 15 and 15a are also closed.

The energization of relay 18 opens contacts 17 in the top starting circuit and contacts 19 in the middle circuit. This disconnects the resistance 21 and inductive device 23 from the upper circuit, and the additional resistance 46 from the middle circuit. It thus serves to complete the transfer to series connection of lamps L1, L2, and L3, L4.

The cnergization of transfer relay 42 opens its contacts 43 and 41. The opening of contacts 43 isolates or disconnects resistance 21d and inductive device 23b from the middle starting circuit and the opening of contacts 41 disconnects resistance 21c and inductive device 23:: in the bottom starting circuit. Also the opening of those two sets of contacts completes the transfer to series connection of the lamps L1L i with lamps L5, L6 so that all six of the lamps Li -L6 are now connected in series beitween the supply line terminals B and W, with the one ballast lamp ISL-1 in series with them.

in the circuit of Fig. 3, the resistance in the middle starting circuit is divided into two sections 21d and 46 in order to insure proper voltage differentialv between the points D and E for the operation of relay 18, and the points F and G for the operation of relay 42. The three ballast lamps are substantially alike as also are the inductive devices.

As in the circuits of Figs. 1 and 2 the transfer from the operation of three lamp groups operating in parallel to operation of the lamps all in series takes place upon the completion of the firing of the lamps in the three individual starting circuits.

As in the circuit arrangements of Figs. 1 and 2, the removal of one lamp from any of the three startingcircuits while the line current is flowing stops any undesired chattering of the relays by interrupting the circuit of the relay coil for that particular starting circuit. Furthermore, should any of the ballast lamps fail, the fluorescent lamps in series with that ballast lamp will cease to operate, but the fluorescent lamps in the remaining circuits will continue to operate. While such operation will not be efficient because of the parallel connection of their circuits, approximately two-thirds of the light will be maintained until such time as a new ba'llast lamp can be installed.

The circuit arrangement of Fig. 3 can be used instead of the circuit of Fig. 2 for operating three lamps in series if desired. This is accomplished by substituting a single lamp in place of the two lamps in each of the three starting circuits of Fig. 3. Also, if desired, and provided the supply line voltage is adequate, the circuitv arrangement of Fig. 3 can be used for operation of. nine lamps in series. To do this three lamps are substituted in place of the two lamps in each of the starting circuits.

The circuit arrangement shown in Fig. 4 is for the purpose of obtaining protection against the occurrence of an extremely low supply line voltage condition. This: is especially likely to occur on lamp circuits operated from a trolley or third rail because the voltage variations from such a supply tend to become extreme;

There is a definite voltage below which. the arc in a fluorescent lamp will not be maintained, and ifan attempt is made to start or operate any of th'e circuitfarrangementsof Figs. 1, 2, or 3 at voltages: belovw'sflth value, undesirable chattering. and burning: of

predetermined minimum value.

r 9 contacts will occur. In Fig. 4 there is shown a protective device for preventing the transfer of the individual lamp starting circuits to series operation where the line voltage is. too low, and until it has been restored to a Also such device interrupts the series connection in case the line voltage is lowcred below a safe operatingfvalue with all lamps in series. Fig. 4 shows alamp circuit which is identical with that ofFig. l but with the addition thereto of a potential or :low voltage relay 48. This relay has two sets of switchcontacts. Normally open contacts 49 are connected in the bridge or transfer circuit between the points D. and E, and normally closed contacts 50 are employed to short circuit a portion 51 of a resistance which is connected in series with relay coil 48. The remainder ofsuch resistance is indicated by 52. This circuit including in series connection the resistance 52, relay coil 48, and resistance 51 is connected between conductors 28 and 32 and consequently across the supply line terminals B and W. i i i When thelamps are in operation and the operating voltage is within the normal range the current through the operating coil of relay 48 maintains contacts 49 closed, which is necessary for the lamps to operate in series, and holds the second set of contacts 50 open. Should however the line potential drop to, for example, 425 volts, in the case of a railroad or trolley circuit, relay 48 will drop out,that is, its contacts 49 will open and its con tactsSO close.

The opening of contacts 49 breaks the bridge circuit de-energizing the coil of transfer relay 18 and causing its contacts "and 19 to reclose. This reconverts the upper and lower lamp circuits toparallel operation across the supplyline, so that the lamps will operate properly and relay chattering will be prevented. When the supply line voltage rises again, for example. toaround 500 volts, the relay 48 will again pick up, inasmuch as the section 51 of resisatnce has been short circuited up to this point. This closes contacts 49, and the lamps will again be placed in series operation.

It will be understood that should the supply line voltage be below a predetermined value, for examp e about 425 volts, and an attempt should be made to turn on the lamps L1-L4, the contacts 49 and 50 of relay 48 will not be actuated because of the low voltage, and the cir-, cuit arrangement therefore cannot progress from two parallel circuits of two lamps in series each, to four lamps in series, until the supply line voltage rises to the 500 volt range.

It is not particularly important, so far as concerns the operating etficiency of this circuit, if the fluorescent lamps are not connected four in series until approximately 500 volts is reached. All of the lamps will light, and

thelosses in the resistors, reactors, and ballast lamps are relatively small at voltages of around 500 and below.

, In Fig. there is illustrated a modified protective circu it wherein an additional relay is employed in place of the delayed action fuse 25 previously described. The

lamp circuit of Fig. 5 is identical with that of Fig. 1, with upper and lower parallel starting circuits for the lamps L1 and L2 in one case and the lamps L3 and L4 in the other.

A protective relay is indicated at 53 in the upper starting circuit and at 53a in the lower. These relays have each a single set of normally closed contacts 54 and 54a. Contacts 54 are in the by-pass circuit for lamps L1 and L2 and are connected between conductors 24 and 26 in place of the delayed action fuse 25. Similarly, contacts 54a are connected between conductors 34 and'35 in the by-pass circuit for lamps L3 and L4.

In serieswith the operating coils of re ays 53 and 53a thereare respectively resistances 55 and 55a. Each coil, with its resistance, is connected across the starting contacts and its own contacts which are connected in series in one of the by-pass circuits. For example, referring to 10 the upper starting circuit, coil 53 and resistance 55 are! connectedin series. Coil 53 is connected by a wire56 with wire 24 at one side of contacts 54. The free end of resistance 55 is connected through wire 57 with wire 27 on the opposite side of contacts 14.

The electrical resistance of coil 53 and resistance 55 together are high in comparison to the resistance of the other relay coils and hence take a negligible amount of current. Relays 53 and 53a and their resistances are so adjusted that even if they should pick up during the fir ing of a normal lamp they will not remain in the pickedup position, that is, with their contacts 54 and 54a open, during operation of the lamps.

However, should a lamp filament become broken or the lamp become deactivated to anextent where it will not continue tooperate, the starting relay 13 or 13a, in its starting circuit will commence to chatter, that is, its contacts will vibrate rapidly. For example, if this happens to one of the lamps, L1 or L2, the starting contacts 14 will vibrate in this manner and a voltage or potential difference will be built up across them which will cause relay 53 to operate and open its contacts 54. This opens the. bypass circuit around lamps L1 and L2 and stops the current flow throughthe coil of relay 13 thus stopping the chattering of contacts 14 and possible damage to them from burning. This, of course, also leaves only the other two lamps L3 and L4 operating.

Once relay 53 has picked up and opened its contacts 54 it will remain in that position due to fiow of current from the ballast lamp BL-l through coil 53 and resistance 55 and thence through the connections shown at the upper part of Fig. .5 and previously described in connection with Fig. 1. to the W side of the supply line. The amount of this current will not be sufficient to keep relay coil 13 energized so that it will drop out, thus closing con acts 14 and opening contacts 15 until such time as the lamp control switch is opened. Lamps L3 and L4 then continue to operate independently of lamps L1 and L2 which are extinguished.

It will be understood that the potential or voltage relay 53 and its res stance 55 are so arranged that the normal voltage drop across an operating lamp or lamps will not energize the relay sufficiently to make it pick up or operate. but the relay will operate and remain in the picked-up position in case one or both of the lamps become abnormal. that is, in the event of their becoming dea tivated or having a broken filament.

In thefollow ng claims which set forth the scope of the invention it will be understood that the term group" is intended to designate one lamp or any number of lamps.

across the supply line, means for firing the group of discharge lam s in each of said starting circuits substantially simultaneously. and switch mechanism connecting said lamp groups in series connection for normal operation.

2. A system for starting and operating gaseous discharge lamps as set forth in claim l wherein the switch mechanism for connecting the groups in series is actuatedby the joint acti n of the firing means in each starting circuit so that said connection takes place upon the firing of the discharge lamps in all of the starting circuits.

3. A system for starting a plurality of discharge lamps and for operatingthem in series comprising the combination of a supply line, at least two groups of discharge lamps, at least two starting circuits each including in 3 said groups of discharge lamps, means for connecting said 1.1 starting'circuitsinparallel across the supply line; means fririfiring the discharge lamp sectionofzcach of said starting circuits'substantially simultaneously; switch mechanism for connecting said lamp sections 'in series. con nection, and means for opening the reactance device sections of said-starting circuits.

4. Asystem for starting and operating discharge lamps as claimed in claim 3, wherein a ballast lamp is included in each of the parallel-connected starting circuits, and one: of said lamps is connected between one side of the supply line and one of said dischargelamp sectionsso thatwhen said sections are reconnected said ballast lamp is retained in series connection: therewith.

5. A system for starting a plurality of dischargelamps and Y for operating them inseries'comprising the com binationof asupply line, a group of said discharge lamps, at" least two starting circuits, each including. in series connectiona group of discharge lamps and an inductive device, means for connecting said starting circuits-across the. supply line with said circuits in parallel connection with one another, a by-pass circuit around the lamps in 'each of said starting circuits, means-for opening'said by-pass circuits to fire said lamps by an inductive voltage impulse, and switch mechanism for connecting said lamp groups in series connection including means'for opening the circuit of the inductive device in each of the parallel starting circuits.

61 A system for starting'and operating 'discha'rgelamps as claimed in claim 5, wherein each of said by-pass circuits includes in series connectiona set of relay contacts and a'delayed action fuse, the relay-operatingcoil being included in the starting circuit so that the energization of-thiscoil will open the relay contacts to start the'discharge lamp group and, in case a lamp should not fire, the contacts will repeatedly open and close, said delayed action fuse operating when such opening and closing is" prolonged to open the by-pass circuit to-prevent further attempts to start the lamp.

7. A system for starting a plurality of discharge lamps and operating them in series as set forth in claim wherein the group of discharge lamps in each of the starting circuits includes two lamps, and wherein the by-pass circuit' of each starting circuit includes one of the supporting pins of each of said lamps so that when either lamp in either starting circuit is removed the by-p'a'ss circuit of'said starting circuit will be openedthus leaving the two lamps in the remaining starting circuit in operation.

8'. A system for starting and operating in seriesa plurality of' discharge lamps comprising the combinationo'f a supply line, a plurality of discharge lamps of the cold starting cathode type, a discharge lamp circuit connecting said lamps in series connection across said line and including an inductive device, a by-pass circuit connected around said discharge lamps, and a relay having: a set 'ofnormally closed contacts included in said by-passcirc'uit and an operating coil included in said discharge lamp circuit so that when said lamp circuit is closed, said relay coil is energized through said by-pass circuit and causes a quick opening of said circuit thereby causing a high inductive voltage surge across said discharge lamps tonfire them.

9. A system for starting a plurality'of discharge lamps and for operating them. in series'co'mprising the combination o-fa supply line, two groups of said lamps, two starting circuits each including a lamp section, and an inductive device section, and a bypass circuit connected around the said lamp section, said lamp section including a group of discharge'lamps,,means for connecting said starting circuits in parallel across the supply line, a" bridge circuitinterconnecting the two starting circuits at points between the lamp section and the inductive devicesection o'f each of said starting, circuits,,and two relays having their respective operating coils in said respective" starting circuits, each of said relays, having a normally closed set of contacts included in said by-pass circuit and a set 12 of. normally opencontacts in said bridge circuit so that when. the starting circuits are closed said operating coils are energized resulting in the opening of the respective by-pass circuits to start the lamp groups andth'e closing of said bridge circuit to place the saidlamp groups in series.

10. A system for starting discharge lamps and for'operating them in series as set forth in claim 9 wherein a transfer relay is provided having an operating coil included in said bridge circuit, said relay having'two sets of normally closed contacts, one of said sets being included in the inductive device section of each of said starting circuits respectively, the opening of said contacts serving to disconnect said inductive devices.

11. A system for starting discharge lamps and for operating them in series as set forth in claim 10 whereina potential relay is provided having an operating coil and a set of normally closed contacts, said coil being connected to respond to changes in the voltage of the supply line, and said contacts being connected in the bridge circuit so that shouldthe supply line voltage drop below a predetermined value, the potential relay contacts will open thereby deenergizing the coil of the transfer relay whose contacts open and reconnect the discharge lamp groups inparallel. j

12. A system for starting a plurality of discharge lamps and for operating them in series comprising the combination of a supply line, two groups of discharge'lamps; two starting circuits, each including in series connectiona'discharge lamp section and an inductive device section, said discharge lamp section including one of'said groups of discharge lamps, means for connecting said starting circuits in parallel across the supply line, a bridge circuit interconnecting the two startingcircuits at points between'the discharge lamp section and the inductive device section of each of said starting circuits, means for firing the discharge lamps in each of said starting circuits, and a relay for each of said starting circuits having an operating coil connected in the starting circuit thereof; each of said relays having a set of normally open contacts in said bridge circuit so that when the starting circuits are closed said operating coils are energized resulting in the closing of said bridge circuit to place the said lamp groups in series for normal operation.

13. A system for starting and operating in series connection a plurality of. discharge lamps comprising the combination of. a supply line, a plurality ofdis'charge lamps of the cold starting cathode type, a discharge lamp circuit connecting said lamps in series connectionacross said line and including an inductive device, a by-pass circuit connected around said discharge lamps, and'a'starting relay having a set of normally closed contacts included in said by-pass circuit and an operating coil included in said discharge lampicircuit so that when said lamp. circuit is closed said relay coil is energized'through said'by-pass circuit and causes a quick opening of said circuit thereby causing a-high inductive voltage surge across said lamps to fire them, and a potential relay-having an operating coiland set of contacts, said contacts being included in saidby-pass circuit inseries connection with said starting relay contacts and said coil being connectedacross said starting and potential relay contacts in series connection so that should a'discharge lamp become inoperative said starting contacts will open andclose repeatedly in an attempt to-start the lamp and thereby cause the potential reiay coil to be energized and open the by-pass circuit so as -to prevent further attempts tostart the lamp:

14. A system forstartinga plurality of dischargelamps and for operating them in-series-c0mprising the combinationof a supply line, a pluralityof groups-of discharge lamps of the cold starting tcatho'de type, at least two starting circuits arranged in parallel connection across said line',' each of said circuits comprising in series connection a discharge lamp'se'ction and" a current-limiting devicesection, said lamp section including a group of discharge lamps and the operating coil of a starting relay, and said current-limiting device section including a resistance, an inductance and a set of normally closed contacts of a transfer-completing relay, said several devices in each of said parallel circuits being arranged in series connection, one of said starting circuits having its discharge lamp section connected adjacent one terminal of the supply line, and the other of said circuits having its discharge lamp section connected adjacent the opposite terminal of the supply line, a by-pass circuit connected around the discharge lamp group of each of said starting circuits, said starting relays having sets of normally closed contacts in said respective by-pass circuits, and said starting relays having normally open sets of contacts connected between the respective terminals of the operating coil of said transfer-completing relay and points in said respective starting circuits between the operating coil of said starting relay and the current-limiting section of said circuit, the energization of the operating coils of said starting relays causing the opening of their normally closed by-pass circuit contacts and the consequent starting of said discharge lamps, and the closing of the normally open contacts of said starting relays causing the energization of said transfer relay and the resulting opening of its two sets of normally closed contacts so as to place the two discharge lamp groups in series with each other through the operating coils of all three of said relays connected in series relation.

15. A system for starting and operating a plurality of discharge lamps as set forth in claim 14 wherein the resistance in one of said starting circuits is greater than in the other so as to insure a potential diiference across the operating coil of the transfer relay adequate to operate said relay when said strating circuits are connected in parallel across the supply line.

16. A system for starting and operating a plurality of discharge lamps comprising the combination of a supply line, at least two discharge lamps of the cold starting cathode type, means for connecting at least two individual starting circuits in parallel across said supply line, each of said circuits including in series connection at least one of said lamps, means for firing the lamp in each of said starting circuits, switch mechanism for thereafter continuing the operation of said lamps in series connection, and switch mechanism for discontinuing the flow of current through said individual starting circuits.

17. A system for starting and operating discharge lamps comprising the combination of a supply line, a plurality of discharge lamps of the cold starting cathode type, means for connecting at least two individual starting circuits in parallel across said line, each of said circuits including in series connection a group of at least one of said lamps, means for firing the lamp group in each of said circuits, and switch mechanism operative upon the completion of the firing of the lamp group in said individual circuits for continuing the operation of said lamps in series connection, said switch mechanism including means for discontinuing the flow of current through said individual starting circuits.

18. A system for starting and operating a plurality of discharge lamps of the cold cathode starting type comprising the combination of a supply line, means for connecting two starting circuits in parallel across said line, each of said circuits including in series connection a reactance device and a group of at least two of said lamps, a bypass circuit around the lamp group in each of said starting circuits, means for opening said by-pass circuits to start said discharge lamps by inductive voltage surge, switch mechanism for thereafter continuing the operation of said lamps in series connection, and switch mechanism for discontinuing the flow of current in each of said parallel starting circuits.

19. A system for starting and operating a plurality of discharge lamps comprising the combination of a supply line, a first branch circuit containing in series connection and in sequence a ballast lamp, a group of discharge lamps, the operating coil of a starting relay, a set of normally closed transfer relay contacts and an inductance, a second branch circuit containing in series connection and in sequence a ballast lamp, an inductance, a second set of contacts of said transfer relay, the operating coil of a second starting relay and a second group of discharge lamps, each of said branch circuits including a shunt circuit around the group of lamps therein and including the contacts of one of said starting relays, means including said transfer relay for connecting said branch circuits in parallel for starting the two groups of lamps, and means including said transfer relay for connecting in series the two groups of lamps and one of said ballast lamps for operation.

20. A system for starting and operating a plurality of discharge lamps comprising the combination of a supply line, three groups of said discharge lamps, a first circuit containing in series connection and in sequence a ballast lamp, one of said groups of discharge lamps, the operating coil of a starting relay, and an inductance, a second branch circuit containing in series connection and in sequence a ballast lamp, the second of said groups of lamps, the operating coil of a second starting relay, a resistance and an inductance, a third branch circuit containing in series connection and in sequence a ballast lamp, an inductance, a resistance, the operating coil of a third. starting relay, and the third of said groups of lamps, each of branch circuits including a shunt circuit around the group of lamps therein and including the normally closed contacts of the respective starting relays, means for connecting said branch circuits in parallel for starting the three groups of lamps, and switch mechanism for connecting in series the three groups of lamps and one of said ballast lamps for operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,930,086 Forney Oct. 10, 1933 2,020,731 Lederer Nov. 12, 1935 2,363,868 Karash Nov. 28, 1944 2,558,293 Feinberg June 26, 1951 2,659,035 Ranney Nov. 10, 1953 2,682,014 Feinberg June 22, 1954 2,683,243 Feinberg July 6, 1954

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