US1997787A - Control for gaseous discharge lamps - Google Patents

Description

April 1935. E. o. ER7CKSON 1,997,787

CONTROL FOR GASEOUS DISCHARGE LAMPS Filed Feb. 13, 1953 L N L2 L1 cs 75 OTHER 7kAA/5FMMER5 Tm,

Patented A r. 16, 1935 UNITED STATES PATENT OFFICE CONTROL FOR GASEOUS DISCHARGE LAMPS Delaware Application February 13, 1933, Serial No. 656,570

14 Claims.

My invention relates to gaseous discharge lamps and has particular reference to lamps of the type employing heated cathodes, and a control system for automatically timing the applica- 5 tion of power to the cathodes and starting devices for the tubes to insure the proper starting of the tubes. In connection with gaseous discharge lamps, and, particularly tubes of the type 'now used for illumination purposes, and for signs, it is common practice to employ a relatively great number of tubes connected to a control circuit which requires that all of the tubes be started substantially simultaneously.

However, when tubes of the heated cathode type are employed, it is undesirable to have the discharge between the electrodes start until the electrodes of the tube have been brought upto an operating temperature, and, for this purpose, it is desirable to prevent the application of power between the electrodes for a predetermined length of time during which the cathodes may become heated.

In the operation of heated types of cathodes, the starting of the discharge between the electrodes prior to the time at which the cathodes are heated to the proper heating temperature, causes severe disintegration of the cathodes and consequently destroys the tube. In commercial use, such occurrence would shorten the effective 1) life of the tube to such degree as to make it necessary to constantly replace the tubes. It

is, therefore, an object of this invention to provide a control circuit and control system for tubes of the hot cathode type in which the application of high potential across the electrodes is prevented until after the cathodes are heated to the proper operating temperature.

Another object of the invention is to provide a system of control in which a time-delay is interposed between the time power is applied to the filaments or cathodes of the tube for the purpose of heating the same and the time at which the high potential is applied between the two electrodes to start the luminous discharge between them.

Another object of the invention is to provide a starting device for tubes of the hot cathode type in which the starting device is rendered inoperative a predetermined length of time after it has been started into action.

Another object of the invention is to provide a simple control system in which a pair of timedelay elements are employed one for the purpose of delaying the application of high potential between the electrodes until after the oathconnection to a plurality of gaseous discharge tubes of the heated cathode type.

Referring to the drawing, I have illustrated a circuit particularly adapted for what is known as the three-wire system of distribution, this circuit including a main source of power supply indicated by three power lines Ll, L-2 and N, the conductor N constituting the neutral return of the three-wire system. The system is arranged to be employed with either one or a plurality of gaseous discharge tubes, though I have illustrated in the drawing the' adaptation of my circuit to a plurality of discharge tubes connected to the three-wire power system in balanced load combination.

The gaseous discharge tubes are designated by the reference characters T-l and T2, the tube T-I being connected through a transformer TRI on one side of a three-wire supply system, while the tube T--2 is illustrated as being connected through a separate transformer to the other side of the three-wire system of supply.

To more readily understand the control system, it should be understood that each of the tubes is provided with a pair of electrodes l and 2, each of these cathodes constituting a filament of considerable construction to permit its becoming heated upon passage of current therethrough or upon the application of heat from a separate heating device. The particular type of cathode illustrated herein is that which is heated by the passage of electric current through a filament forming the cathode and it is essential, therefore, to provide a source of relatively low potential for the purpose of heating the same, and this source of heating potential for the cathode I is illustrated as constituting a relatively small coil .3 on the time transformer TR-I which is employed for the purpose of supplying power to the tube. Similarly, the cathode 2 is provided with heating current from a relatively small secondary winding 4 on the transformer TR I, so

that when current is supplied to the primary 5 of this transformer, low potential will be applied to both of the cathodes for the purpose of heating the same.

The transformer TRI is illustrated as being provided with a main secondary winding 6 for the purpose of supplying relatively high potential between the two electrodes I and 2, but it is a characteristic of this type of tube that even though high potential is impressed across the electrodes, the discharge between the electrodes does not readily start, and it is necessary to provide a starting device 1 which will initially start the discharge. The starting device I, which is most commonly employed, is a spark coil in which the output circuit is connected to ground as at 8 and to a coil or other conductor 9 disposed closely adjacent the exterior of the glass envelope which forms the tube, while the input circuit of the spark coil may be connected to any suitable source of power.

As stated above, the desired sequence of operations for the proper starting of tubes of this type is first to apply heating potential to the heating filaments or heating devices for the electrodes and to allow them to become heated or brought up to the proper operating temperature, and then to apply the operating high potential between the two electrodes across the starting of the discharge. Then, in order to insure the starting of the tube, power should be applied to the starting device I to initially start the tubes and then power should be removed from the starting device 1, since it is undesirable to continue the operation of the starting device after the tubes have had an opportunity to start.

To accomplish these successive operations in proper timed relations, I have illustrated the main power supply as being connected to a control switch Cs which, when closed, will supply power directly to the primary winding 5 of the TR-I. This will cause the power to be supplied from the small secondaries 3 and 4 to the respective filament or cathode I and 2 to cause them to be heated. However, the circuit for the secondary B of the transformer is not completed at this time since this circuit is interrupted by the contacts a of relay R-I The circuit for the primary winding transformer TR-I extends from line conductor L I through the left-hand pole of Cs and thence extends as conductor III to a junction point II whence a branch conductor I2 connects to one terminal of the primary winding 5 of the transformer TR-I, the other terminal of which connects by way of conductor I3 to a junction point I4 upon the neutral conductor I 5 which is in turn connected through the middle pole Cs to the neutral conductor N of the power supply.

- It will be observed that the conductor I0 extends beyond the junction point II to permit the connection thereto of any number of transformers which it may be desired to connect to and be controlled by the same circuit.

At this time, however, the circuit to the secondary winding 6 of the transformer TR-l is not completed since the coils of the relay R-I are connected in series with a thermostat THI, the resistance of which is sufficient to prevent the coil of the relay from operating its contact to closed position until after the armature I6 is brought into contact with its contact member I! to short-circuit the resistance or heating coil I8 of the thermostat. Thus, depending upon the time delay imposed by the thermostat THI, the contact a of relay RI will close only at a predetermined time after the closure of the switch Cs, and this time should be selected as sufficient to permit the cathodes to be brought up to desired operating temperature. For example, the arrangement may be such that a 5-second delay will be sufiicient to permit the electrodes to be heated to the desired operating temperature, in which case, for safety and for satisfactory commercial operation, the thermostat THI should be selected and adjusted to provide a lO-second delay, thus providing ample time for the electrodes to become heated with a considerable margin of safety.

Upon the operation of the relay R-I to close its contacts a, the secondary circuit for the transformer TRI will be completed and it will be noted that this circuit extends from line conductor LI through conductors I0 and I2 to one terminal of the secondary 6 of the transformer 'IR-I, the other terminal connecting at I9 to one of the conductors 20 which is employed for the heating circuit for electrode I of the tube T-I. Thence the circuit continues through the space of the tube to the opposite electrode 2 of the tube, and thence by way of conductors 22 and 23 to a conductor 24 which extends through the contact a on relay R-I, and thence the circuit continues by way of conductors 25 and 26 to neutral conductor I5 which connects to the neutral power line N. Thus approximately 10- seconds after the power is supplied to the primary winding 5 of the transformer, the secondary circuit is completed to supply high potential across the electrodes and across the tube to prepare them for starting. However, as hereinbefore set forth, tubes of this type are not readily self-starting and it is desirable to connect the spark coil or other starting device I to supply the starting impulse after the high potential has been applied between the electrodes.

The starting device "I should be started at about the same time that the secondary circuit is completed to the tubes and to insure this operation at the proper time the circuit for the starting device l is arranged to extend through contacts a on a relay R-2, the coil of which is connected in the same circuit as the coil of the relay R-I and which controls the delayed action of the relay RI.

It will be observed that the coils of the relay R-I and R-2 are connected in parallel relation with each other and are connected in series with the thermostat TH-I so that when the thermostat 'I'H--I operates, both of these relays will operate simultaneously.

The circuit of the starting device 1 extends from line conductor L-2 through the right-hand pole of the switch Cs, and thence by way of conductor 21 to a junction point 28, thence by way of conductor 29 to normally closed contacts a for relay R3, (the purpose of which will be set forth hereinafter), thence by way of conductor 30 to contacts a on relay R-Z, conductor 3| to a junction point 32, thence by way of conductor 33 to the spark coil 1, whence the circuit returns by way of conductor 34 to the neutral conductor I5. Hence the tube, having its cathode heated to the proper temperature and having high potential supplied between the two electrodes, will now start its luminous discharge.

As soon, however, as the tube has started its discharge, it is no longer necessary to maintain current upon the spark coil or other starting device and I have arranged to disconnect the spark coil after a predetermined length of time by extending the circuit to the spark coil through -the normally closed contacts a of the cutoff re other, and in series with the thermostat TH-l, so .that the amount of current which is drawn through the heating coil 3 of this thermostat is considerably greater than the amount of current which is drawn through the thermostat TH--2 and such thermostat has only the load of the coil of relay R3 imposed upon it. Thus the relays Rl and R.-2 and 'R3 may be selected of the same type and the same size, and, more particularly, having the same electrical characteristics; the only difference between these relays is that relay R-3 must have one normally open contact and one normally closed contact, instead of two normally open contacts, as are employed upon the remaining relay. Thus these relays may be readily interchangeableand readily replaced from a single stock of relays by merely changing the contacts when necessary.

Moreover, the thermostats TH--I and TH--2 may be selected also having the same electrical characteristics, and, in fact, these thermostats may be identical in construction, if desired, thus requiring only that a single type of thermostat be carried in stock and that all these thermostats may be initially adjusted with the same contact spacing and yet, when installed in the system, the relays and thermostats will operate to produce two distinct timed relays. This is accomplished by reason of the fact that thermostat TH-l will be heated by twice the current supplied to thermostat TH-2 since thermostat TH--I is in series with two relays which are in parallel relation with each other, while thermostat TH--l has but a single relay coil in series with it. For example, the relay 'IHI was assumed to operate at the end of lO-seconds after the current was supplied to it, and it follows that thermostats TH-2, having but one-half of the current load passing through it, would operate at a later time; for example, 5 seconds after the operation of thermostat TH--l, or a total of seconds after the closure of the switch Cs. Thus the spark coil is connected in efiective operation for a period not exceeding 5 seconds. By selecting the thermostats of the proper type, such as those which are provided with ambient temperature compensation, the two thermostats may still be identical with each other and the compensation of each of the thermostats will insure substantially constant time differences in their operation under changing ambient temperature conditions.

After the relays R-l, R.--2 and R-3 have once been operated, it is desirable to' keep these relays in energized condition unaffected by the thermo-;

stats TH--i and TH--2, and for this purpose I have illustrated the relay R,2 ashaving a second,

set of contacts I) which, when closed by the operation of the relay R-2, completes an auxiliaryor holding circuit for supplying both relays R-2 and R-l with power direct from the neutral conductor l5 independently of the thermostat 'I'H-l. Thus when the relay R.-2 is operated, a circuit is completed from line conductor L-l, through the switch Cs, conductor I0 and junction point 36,

whence one branch extends through conductor tl I to the :oil of relay R.2 and the conductor 38 to a junction point 39, while the other branch extends from conductor l0 through conductor 40,

the coil of relay R-l and conductor 42 to junction 39, whence both circuits extend through conductor 43, contact b on relay R--2, conductor 44 to junction 45 on neutral conductor l5.

In like manner the relay R3, once actuated,

should be maintained energized independent of the thermostat TH-2 and relay R3 is therefor provided with an additional set of contacts b to complete a holding circuit for relay R3, which circuits extend from line conductor L2 through the switch Cs, conductor 21 to junction point 46 and thence by way of conductor 41 to the relay R,2, conductor 48 and contact b on relay R-3 and conductor 49 to junction point 45 on the neutral conductor l5. Thus once the relays have been actuated they will remain in actuated condition to hold the secondary circuit from the tubes in effective operation and also to hold the starting devices I out of effective operation.

One of the advantages of my system lies in the fact that the control Cs may be located at any convenient point and the power supplied to all of the tubes may be led through this control point so that the relays and thermostats may also be located at this convenient point ready for access for replacement, adjustment and repair and all that is necessary is to lead the six conductors from the control location to any remote point at which the tubes and their respective transfers may be located.

I have illustrated my system as embodying the adaptation for a three-wire power supply and have illustrated the two outside power conductors l0 and 21 as extending throughout the system to permit the connection of certain of the transformers between the conductors H] and the neutrals l5, while the other transformers will be connected between the conductor 21 and the -neutral conductor IS, in order to balance the load on both sides of the circuit. With this arrangement for a three-wire power supply, I prefer to connect ,the secondary return 23 for all of the transformers which are connected on one side of the circuit mon neutral return wire 24, while all of the secondary returns 23 have the transformer connected on the other side of the three-wire system (namely'between conductors 21 and 15) to an independentneutral return conductor 50 which is independently controlled by the relay R-l by passing this circuit through a second set of contacts b on the relay R-I, while the starting device for all of the tubes may be connected to the common conductor 3|.

Again, while I have illustrated the system as being particularly adapted for a three-wire system distribution, it will be apparent that the control device isequally adapted to a two-wire system by connecting the coils of all the relays Rl, Rr-2, R3 across the two conductors forming a twowire power supply and connecting all of the transformers TRI, TR-2 across these two power It will, therefore, be observed that the control system herein set forth permits the installation of the system to be controlled by a single power switch Cs which, when closed, sets into operation all of the necessary apparatus for properly starting the discharge lamps which may be connected to this circuit, and it is, therefore, unnecesary for the person who is operating the system to perform any other operation than that of merely closing the switch Cs when it is desired to illuminate the lamp.

By delaying the closing of the secondary circuit until after the filament has had an opportunity to become heated, accidental starting of the tubes before the filaments are in proper condition is effectively prevented, as might occur where the installation employed transformers having a relatively high voltage output, or in the case of certain types of tube, for example those containing mercury, or, as might occur if the tubular lamps are located in proximity to sources of electrical discharges.

The control system hereinbefore described also provides a protective system for the lamps in the event of abnormal conditions existing in the circuit, for example:

1. In the event that there is a momentary cessation of power supply with the current cutoff a sufiicient length of time to allow relays Rl, R2, and R3 to drop, but the restoration of power to the circuit will cause the relays to operate again in their regular sequence and with the imposed time delays so that the tubes will be prevented from restarting until after the cathodes have had a chance to again warm up to the proper operating temperature.

2. In the event that a fuse was blown in either of the outside lines of the three-wire system, the closure of the switch Cs would not result in the starting of the tubes, since either the relays RI, R-2 would fail to operate or the relay R-3 would fail to operate.

It may be desirable to include a manually actuated push button PB in the circuit for the spark coils so that if one of the tubes is slow to start, but is still operative, a momentary operation of the spark coils may be accomplished manually after the relays R-l, R2 and R, 3 have performed their cycles of operations for the normal automatic starting of the tubes.

It will be observed, therefore, that I have provided an automatic starting system for gaseous discharge tubes which insures the proper timing of the various operations of the starting cycle and which constitutes a protective system for the tubes in the event of abnormal or emergency conditions arising in the system.

While I have shown and described the preferred embodiment of my invention, I do not wish to be limited to the details of construction shown herein, except as defined in the appended claims.

I claim:

l. A gaseous discharge tube of the heated electrode types, a source of current for supplying heating potential to the electrodes and operating potential between the electrodes, heater circuits for the electrodes, an operating potential circuit including said electrodes, means for controlling the supply of current from said source to said heater circuits and said operating potential circuit for delaying the closure of said operating potential circuit for a predetermined length of time after the heater circuits are energized.

2. A gaseous discharge tube of the heated electrode type, a source of current, a transformer,

ing potential circuit including said electrodes and a winding on said transformer, power circuit means for supplying current from said source of supply to said transformer, means in said operating potential circuit for delaying the completion thereof for a predetermined time after the completion of said power circuit, a starting device for the tube, and means for actuating said starting device at a predetermined time after the completion of said power circuit.

4. In a control system for a gaseous discharge tube of the heated electrode type, a transformer having a primary winding, heater circuits for said electrodes including secondary windings on said transformer, an operating potential circuit including the electrodes and a secondary winding on said transformer, a power circuit for supplying current from said source to the primary winding of said transformer to energize said heater circuits, and means in said operating potential circuit for completing said operating potential circuit only at a predetermined time after the completion of said power circuit.

5. In a control system for a gaseous discharge tube of the heated electrode type, a transformer having a primary winding, heater circuits for said electrodes including secondary windings on said transformer, an operating potential circuit including the electrodes and a secondary winding on said transformer, a power circuit for supplying current from said source to the primary winding of said transformer to energize said heater circuits, means in said operating potential circuit for completing said operating potential circuit only at a predetermined time after the completion of said power circuit, a starting device for the tube, and means for actuating said starting device at a predetermined time after the completion of said power circuit.

6. A gaseous discharge tube of the heated electrode type, a source of current for supplying heating potential to the electrodes and operating potential between the electrodes, heater circuits for the electrodes, an operating potential circuit including said electrodes, means for controlling the supply of current from said source to said heater circuits and said operating potential circuit for delaying the closure of said operating potential circuit for a predetermined length of time after the heater circuits are energized, a starting device for the tube, and means for actuating said starting device at a predetermined time after said heater circuits are energized.

7. In a control system for a gaseous discharge tube of the heated electrode type, a transformer having a primary winding, heater circuits for said .electrodes including secondary windings on said transformer, an operating potential circuit including the electrodes and a secondary winding on said transformer, a power circuit for supplying current from said source to the primary winding of said transformer to energize said completion of said power circuit, a starting device for the tube, means for actuating said starting device at a predetermined time after the completion of said power circuit, and means for rendering said starting device inoperative at a predetermined time after the closure of said operating potential circuit.

8. In a control system for a gaseous discharge tube of the heated electrode type, heater circuits for said electrodes, means for energizing said heater circuits, an operating potential circuit for supplying operating potential between said electrodes, switch means for controlling the energization of said heating circuits, an additional switch means in said operating potential circuit operably responsive to the closure of said firstnamed switch means for completing said operating potential circuit only at a predetermined time after the closure of said first-named switch means.

9. In a control system for a gaseous discharge tube of the heated electrode type, heater circuits for said electrodes, means for energizing said heater circuits, an operating potential circuit for supplying operating potential between said electrodes, switch means for controlling the energization of said heating circuits, an additional switch means in said operating potential circuit operably responsive to the closure of said firstnamed switch means for completing said operating potential circuit only at a predetermined time after the closure of said first-named switch means, a starting device for the tube, and means for energizing said starting device at a predetermined time after the closure of said first-named switch means.

10. In a control system for a gaseous discharge tube of the heated electrode type, heater circuits I for said electrodes, means for energizing said heater circuits, an operating potential circuit for supplying operating potential between said electrodes, switch means for controlling the energization of said heating circuits, an additional switch means in said operating potential circuit operably responsive to the closure of said first-named switch means for completing said operating potential circuit only at a predetermined time after the closure of said first-named switch means, a starting device for the tube, means for energizing said starting device at a predetermined time after the closure of said first-named switch means, and means for rendering said starting device inoperative at a predetermined time after the completion of said operating potential circuit.

11. In a control system for a gaseous discharge tube of the heated electrode type, heater circuits for supplying heating potential to said electrodes, operating potential circuits for supplying operating potential between said electrodes, a power circuit for energizing said heater circuits and said operating potential circuits, "a relay connected across the said power circuit and operably re sponsive to the completion of said power circuit for completing said operating potential circuit,

and means in circuit with said relay for delaying the operation of said relay for a predetermined length of time after the closure of said power circuit.

12. In a control system for a gaseous discharge tube of the heated electrode type, heater circuits for supplying heating potential to said electrodes,

operating potential circuits for supplying operating potential between said electrodes, a power circuit for energizing said heater circuits and said operating potential circuits, a starting device for the tube and relay means connected across said power circuit and operably responsive to the completion of said power circuit for completing said operating potential circuit and actuating said starting device, and means in circuit with said relay means for delaying the operation of said relay means for a predetermined length of time after the completion of said power circuit.

13. In a control system for a gaseous discharge tube of the heated electrode type, heater circuits for supplying heating potential to said electrodes, operating potential circuits for supplying operating potential between said electrodes, a power circuit for energizing said heater circuits and said operating potential circuits, a starting device for the tube, a pair of relays connected across said power circuit for energization upon completion of said power circuit, means controlled by one of said relays for completing the operating potential circuit, means controlled by the other of said relays-for actuating said starting device, means in circuit with said relays for delaying the action of said relays for a predetermined length of time after the completion of said power circuit, said delaying means comprising a thermostat connected in series with both of said relays and having a heating resistance suificient to prevent actuation of said relays until said thermostat has been heated to operate its contacts.

14. In a control system for a gaseous discharge tube of the heated electrode type, heater circuits for supplying heating potential to said electrodes, operating potential circuits for supplying operating potential between said electrodes, a power circuit for energizing said heater circuits and said operating potential circuits, a starting device for the tube, a pair of relays connected across said power circuit for energization upon completion of said power circuit, means controlled by one of said relays for completing the operating potential circuit, means controlled by the other of said relays for actuating said starting device, means in circuit with said relays for delaying the action of said relays for a predetermined length of time after the completion of said power circuit, said delaying means comprising a thermostat connected in series with both of said relays and having a heating resistance sufiicient to prevent actuation of said relays until said thermostat has been heated to operate its contacts, a third relay connected across said power circuit Mr deenergizing said starting device, and means in circuit with said third relay for delaying the action of said relay for a predetermined length of time after the completion 'of said power circuit in excess of said first-named time.

ELLIS OSMON ERICKSON.

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