US2386914A - Fluorescent tube circuit - Google Patents

Description

Oct, 16, 1, A. sLEPlAN` FLUORESCENT TUBE CIRCUIT Original Filed June 15, 1940 m5 um NF O wu m W Am Q J. x,

Patented Oct. 1,6, 1945 Arthur Slepian, Trumbull, Conn., assignor, by mesne assignments, to The Wheeler Insulated Wire Company, Incorporated, Bridgeport, Conn., al corporation of Delaware .f

Original application June 15, 19.40, Serial No. '340.701, nowPatent No. 2,340,348, dated February 1, 1944. Divided and this application March 4, 1943, Serial No. 477,932

claims. (cl. 315-400) The present invention relates to fluorescent tube circuits, and, more particularly, to a control means for opening the circuit upon failure of the starter to cause the tube to arc over.

'I'his application is a division of my copending application, Serial No. 340,701, filed June 15, 1940,

now Patent No. 2,340,348, granted February 1, 1944. f

In fluorescent tube circuits, especially of the type wherein an automatic starter is employed to close the filament circuit during the heating period thereof to cause said heated filaments to produce an ionized condition in the tube which will arc over upon a proper potential being impressed thereon, diiculty had been encountered because of the automatic switch failing to open the heating circuit for the tube'after the heating period which results in a prolonged :flow of high current in the filaments, which current causes the filaments to burn out readily.

Also, when the starter fails to open the heating circuit, the abnormal current demand places an additional load on the transformer or other energy supply means which results in a large amount of heat being generated in said transformer or supply means causing the potting compound or other filling material therein to'be softened and the unit otherwise damaged.

In some circuits having capacitance therein, the tube will arc over even though the switch has not opened.

it is practically impossible, after the tubes have arced over, to determine from the appearance of the tube whether or not the automatic switch* means has opened the heater circuit and thus the damaging effects of such a condition will not be apparent until l after the damage has been done.

According to the present invention, I have provided in the lighting circuit a means for opening said circuit, should the automatic switch fail to properly operate or should some other portion of the circuit fail. This may take the form of a current-responsive circuit opener or a'heatresponsive circuit opener, or both of said circuity openers may be included in the same circuit.

In one form of the invention, I have illustrated a plurality of tube circuits and have provided a current-responsive switch'in each of these tube circuits. Each circuit is connected to a secondary of the operating transformer. With this arrangement, only that circuit need be cut out which is in trouble, since the current-responsive switch in the circuit which is in trouble will be caused to open and cut off a supply of energy to the tube` placed it within the can or adjacent thereto to be It is to be understood that preferably these current-responsive means shall have sumcient time delay so that they will not be operatedby the starting current in the tube but whichwill operate on a prolonged high current demand.

` During the ldeactvating process of the tube, at which time the tube will fail to arc over, the automatic starter will be periodically operated.

,While the current therein is not excessive to cause heater operated by the current i the starting circuit for destroying the fusible element upon predetermined overheating due to 'the operation of the starter circuit. In this connection, it must be pointed out that a suflicient time lag should be present in these circuit breakers to prevent normal use of Fig. 3 shows another form 'of control for the starter can.

Fig. 4 is a sectional view of the thermo-responn sive switch.

Fig. 5 is a detail of the contact structure of the thermal switch.

The drawing shows the present invention asa plied to a lighting system having two fluoresce t tubes I0 and iI-therein operated by apower supply i2 connected across lines i3.

In the illustrated form of the invention, the

power supply comprises an autotransformer having a primary I4 and a pair of secondaries I5 and I6 spaced atf opposite ends thereof supported by the core of the transformer. The iiuorescent tube I0 has its filament I0a connected to the secondary l5 and its filament i0b connectedto one side of the power line and a starter lmatically illustrated at Hic and llc do not form a part of the present invention. 'I'hese switches may be of the type sold as can switches FS-2 or IPS-4, or of the typ'e disclosed in Patent No. 2,200,443l to Dench, granted May 14, 1940, and ,which function to open the-heating circuit for the filaments after they have been heated suliciently torender said tubes conductive. If the EPS-2 or FS-4 are used, thecondenser l1 need not bej 'included inthe circuit as a condenser is incorporated in the unit.

Many difficulties .have arisen in fluorescent tube circuits. One of the chief sources of trouble resides' in the operation of the starter switch which is closed to heat the laments and cause ionization of the gas in the tube to permit an 'arcing over or discharge between the -filaments upon proper voltage being applied to the filaments where the heating circuit is' open. It will be apparent. therefore, that the heating circuit must be automatically opened as soon as the filaments have been heated to reduce the current demand in said circuits. However, in many instances, especially where automatic starter switches have been employed, the start- I ing circuit has failed to open and has caused a "heavy current to continue to pass through the filaments of the tube,\which quickly causes these filaments to burn out and the tube to become useless.

' Also, 'the heavy load caused by this abnormal demand for current causes the transformer or choke coil or other energy-supply'means to become overheated to such an extent that the pot- .ting or lling material for the transformer o'r circuits;fail to operate properly, the current demand will be sufilcientto heat the bimetallic arms 42l or 25 and cause the arms to flex and move contacts 24, and open the circuit to either Aone or the other of the tubes. Heater coils for heating the arms 2l and 25 may be used if desired.

While current-responsive switches of various types may be used in the circuit, I prefer that type employing the bimetallic arm inasmuch as the heating of the bimetallic arm provides a sufficient time lag in the circuit to permit the flow of the high starting current present in the normal operation of the tube. i

During the deactivating process of the tube, at which time the tube fails to arc over between thejilaments thereof-upon the openingof the starter circuit, the starter switch is caused to repeatedly operate in an effort to start the the like becomes melted and runs therefrom.

causing damage to the transformer or the. like and causing disagreeable eil'ects as a result of the dripping of the` potting material from the transformer.

In some instances, where there is a condenser in the circuit, the tube has arched over even cient to cause the starter to become abnormally though the starter switch has not opened the Y heater circuit. When this occurs, the failure of the automatic switch to openthe heating circuit after the tube has arched over and become 'fluorescent is not apparent and the trouble is' not detected until damage to the equipment has occurred.

According to the present invention, I haveprovided current-responsive switch means in each of the, tube circuits which will open the circuit upon an abnormal current flowing in the circuit.

As shown in 1, acurrentresponsive switch I3 having a iiiied contact l! and a movable contact 20 carried by bimetallic arm 2| is connected vin the circuit for the fluorescent tube 1 0, whiler a similar switch 22 having affixed contact 23 and a movable contact 24 carried by a bimetallic arm 25 is connectedin the circuit for tube Il.y Shouldtthe starter means in either of the tu -eri'ergization of the tube. This continued opermeans.

One form of this invention is shown in Fig. 2. wherein a fusibleelement 30 is located within the can 35 and is connected in series with one of the contacts of the -starter switch and is provided with a heating coil 3| connected in the circuit.

When'the light circuit is closed, the starter switch will arc over betweenfcontacts 32 and 33 enclosed in tube 36 and thecurrent passing therethrough will cause a bimetallic arm 34 carrying contact 33 to flex and move the contacts and extinguish the arc, causing the starter circuit to be opened and the tube to arc over. However, upon the failure of the tube to arc'over. the voltage will still be impressed on the starter circuit' to cause it to again arc over and again ygo through the operation necessary to start the element in this form of the -invention is positioned closely adjacent the starter switch and the heating coil is so arranged with respect thereto as to insure destruction of the fusible element, only after a predetermined interval of time suiilheated and open the circuit. Care must be taken to prevent the material of the fusible elementlfrom snorting the turns of the heater coil.

In the form of the invention shown in Fig. 3. the'starter can 35 has mounted therein'a pair of spring contacts 40, 4I, connected in the heater circuit, which are normallybiased into .opencircuit position. The contacts, however, are' `held together bya fusible member 42 disposed adjacent the starter switch. Upon the heating of the fusible member, through increased operation f the starter switch, the fusible element will become destroyed and the contacts will separate and open the circuit.

Also, if the contacts 32, 33 of the switch means should become permanently shorted so that'. the

' ,heat-responsive member cannot return them to their .normal positions after extinguishing the arc, thenthe Starter means will also heat up and the increased temperature will operate the heatresponsive means.

It is to be understood that the heat-responsive switchmeans 'can be placed in various types of automatic starting lmeans to be operated by overheating of the same.

In the broader aspects of my invention, I have provided a means for protecting the tubes, which operate on critical voltages and currents, against abnormal currents which may be due to short circuits or the like in the lamp circuits.

Variations and modications may be made within the scope of this invention and prtions of the improvements may be used without others.

I claim: l l. In a uorescent tube circuit, a gaseous discharge uorescent tube having laments therein; automatically operated switch means in said circuit for periodically closing a heating circuit between said laments when the tube is nonconducting to heat the filaments to cause said tube to be operative; and heat-responsive means including .contacts in the heating circuit for opening the heating circuit upon`overheating of the starting means caused by repeated operations of said switch upon the tube failing to become operative.

2. A gaseous discharge lamp; a starting circuit for said lamp; starting means including contacts for closing and opening said starting circuit and adapted upon the application of voltage to said lamp to cause current iiow through the lamp electrodes to effect heating thereof when the contacts are engaged and upon separation of the contacts to cause the application of voltage across the electrodes suii'icient to light the lamp; and protective means having contacts in said starting circuit and operable to open said starting circuit in the event the lamp does not light in response to the operation of said starting means.

3. A iluorescent lamp; a starting circuit in parallel with said lamp; a starting switch in said starting circuit operable when the lamp is out and voltage is applied thereto to effect repeated opening and closing of said starting circuit until the I'lamp lights; a ballast in series with said lamp operable each time saidl starting circuit is broken to induce a relatively high voltage across said lamp for lighting the lamp; and a normally closed protective switch connected in said starting circuit operable to effect the opening of said starting circuit in the event the continued operation of said starting'switch fails to start said lamp in operation within a predetermined time interval after the initialoperation thereof.

` 4. A protected starter unit to be used in the iilament circuit of a fluorescent tube comprising a housing, an automatic starter switch means enclosed therein to be connected in the filament circuit of the fluorescent tube for temporarily closing said circuit to heat the filaments and cause said tube to become conductive and to repeat said operation until said tube becomes conductive, and a protective means connected in said circuit and mounted within the housing,

said protective means including a destructible y member and a heater resistor therefor connected in the said circuit to destroy said destructible member and permanently open the circuit upon repeated operations of the starter switch means or change from a normal condition in the starter means.

5. A protected starter unit to be used in the lament circuit of a fluorescent tube comprising a housing, an automatic starter switch means enclosed therein to be connected in the filament circuit of the iiuorescent tube for temporarily closing said circuit to heat the filaments and cause said tube to become conductive and to repeat said operation until said tube becomes conductive, and a protective switch mounted in the housing, said last-named switch including a pair of contacts connected in the filament heating circuit and normally urged to open-circuit position and heat-responsive means for holding said contacts in closed-circuit position and for releasing said contacts to permanently open the circuit upon repeated operations of the starter switch means or change from a normal condition in the starter means.

ARTHUR SLEPIAN.

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