US2351440A - Electric discharge lamp starting device - Google Patents

Description

June 1944- H. J. M CARTHY I ELECTRIC DISCHARGE LAMP STARTING DEVICE Filed Oct. 9, 1941 Figvi 1 6 Insulaflon H121$JIMCC (ZJ'IkZy INVENTOR. m

ATTORNEY Patented June 13, 1944 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE LAMP STARTING DEVICE Henry J.

McCarthy, Danvers, Mass, assignor to Sylvanla Electric Products Inc., a corporation of Massachusetts Application October 9, 1941, Serial No. 414,318

7 Claims.

tecting the auxiliary apparatus used in conjunc-' tion with fluorescent lamps under failed lamp conditions.

Further objects, advantages and features will be apparent from the following specification taken in conjunction with the accompanying drawing in which:

Figure 1 is a side view of an embodiment of my relay;

Figure 2 is a side view showing the relay of Figure 1 under failed lamp conditions;

Figure 3 is a front view of a second embodiment of my relay;

Figure 4 is a side view of a third embodiment of my relay;

Figure 5 is a side view showing the relay of Figure 4 under failed lamp conditions;

Figure 6 is a schematic diagram of a fluorescent lamp circuit in which these relays may be used.

In the operation of electric gaseous discharge tubes and more particularly in the operation of fluorescent lamps, a relay is generally employed to permit the pre-heatingof the filamentary electrodes sumcient to bring about the striking of the lamp are. If the lamp arc fails to strike or maintain, the relay operates to provide a second electrode pre-heating period. In this regard, I have found the thermal relay shown in my copending application Serial Number 335,968 filed May 18, 1940, and issued June 9, 1942 as Patent No. 2,285,450 to be of distinct advantage for it provides an auxiliary starting means which operates when the lamp arc fails to strike or maintain in the first instance.

My present invention consists of a thermal relay of the general type shown in the co-pending application with a cut-out embodied therein to arrest the operation of the relay elements it the lamp is faulty. This is a highly desirable feature for it not only eliminates the unsightly appearance which a defective lamp presents when the arcfails to strike despite the successive cycles of electrode pre-heating periods but it also prevents any undue strain being placed upon the auxiliary equipment under said conditions.

In Figures 1 and 3 the resistance rod 1 is supported between the supporting wires 2 and 3 which are electrically connected to the metallic strips 4 and 5 on the relay support 6, which is formed of insulating material. The other end of these strips 4 and 5 ar connected to the lead-in wires 1 and 8 which extend through the base 9, which is formed of insulating material, and into the base pins l0 and I I.

mounted on the supporting arm 3| on the support 6 and is bent around the resistance rod l. A coating may be applied to the resistance rod such as the coating described in the above-identified application or in the co-pending application, Serial Number 321,946 filed March 2, 1940, and issued February 17, 1942 as Patent No. 2,273,056. I have found an alumina and shellac mixture satisfactory to insulate th resistor I from the bimetallic strip I2 and at the same time conduct heat from the resistor to the strip. A condenser may be placed across the resistance l to cut down radio interference due to the operation of the switch and lamp. A condenser of .006 microcontact 13 may be only about 1 to 5 ohms.

farad has proven to be advantageous.

A high resistance contact l3 such as carbon is supported on the outer end of the supportin arm I4, which is attached to bimetallic strip I1, and is normally closed with the bimetallic strip l2 at a point adjacent the free end thereof when the circuit therethrough is dead. The resistance of the high resistance contact I3 is small compared to the resistor l. The latter may be about 40,000 ohms, for example, while the resistance of the contact l5, such as nickel, may be located on the bimetallicstrip l2 so that th closing of the high resistance contact I3 with the bimetal l2 may be through the contact l5, thereby preventing excessive wear on the bimetal. A similar contact 15 may be located on the free end of the compensator ll for the same reason, in as much as the low resistance contact [8 on the bimetallic strip l2 will come in contact therewith when the auxiliary starting feature of the relay operates.

The cut-out feature of my relay may be embodied therein in any one of several different ways. -It may be accomplished by having the free end of the bimetal I! extend below the point at which it is closed with the high resistance contact l3 and curl inwardly in the direction of the compensator ll which is supported on the arm IS on the support 6 and locating an insulating tab 20 on the compensator ll at a point opposite the curled end of the strip l2 as shown in Figure 1.

It has been found that some advantages can be The bimetallic armature i2 is v gained by supporting the member which is to come in contact with the insulating tab from added assurance that the normal operating func-' tions of the relay elements will not be obstructed. Still a third manner in which the cut-out may operate is shown in Figure 4 and will be subsequently described.

In Figure 6, the electric gaseous discharge lamp consists of the glass envelope 2! with the fllamental- y electrodes 22 and 23 sealed therein at each end. The glass envelope may have a coating of fluorescent material 24 on its inner wall. The electrodes may be of the coiled-coiled type containing a filling of one or more of the alkaline earth oxides. A filling of an inert gas, such as argon, and mercury vapor may be sealed in the glass envelope. A lead-in wire 26 from one end of one electrode may be connected to one end of the power line from which the apparatus is operated. An end of the other electrode may be connected through a suitable ballast impedance, such as an inductance coil, 21, to the other end of the power line by the lead-in wire 28. The other leadin wires 29 and to'leading from the other end of each electrode may be connected together through the above described relay.

When the full line voltage is placed across the relay, the electrodes of the lamp will immediately start to heat. The heat conducted to the bimetallic strip l2 from the resistance 8 will heat it sumciently to cause it to break away from its position closed with the high resistance contact 83. This breaking away is so timed that it will normally take place at about the same moment that the electrodes have been sufllciently heated to support the discharge across the lamp. Since there is about one-halfline voltage across the resistance rod during the operation of the lamp, the heat, conducted to the bimetallic strip by the rod will cause the strip to take a position, during the actual operation of the lamp, at a point about half way between its normally closed position with the high resistance contact i3 and the low resistance contact l6. Thus there is no danger of the strip l2 cooling to a temperature 7 where it would re-establish its contact with, the

high resistance Contact and thus renew the starting operation.

If the current should be thrown off, and immediately thrown on again without sufficient time elapsing to allow the strip ii to cool, or ii, for any reason, the arc failed to strike when the strip. l2 broke away from the high resistance contact l3, the full line voltage would be across the resistance I and the strip I? would be heated and continue to be deflected further away from the high resistance contact l3 until it struck the low iesistance contact I 6, thus short-circuiting the resistance rod l and starting the pre-heating of the lamp electrodes. If the lamp arc fails to strike when the bimetallic strip I2, now cooling,

shown in Figure 1 so that after the relay has completed several cycles of operation in attempting to start the lamp, the relay will be cut out from the lamp and will no longer try to start it. This cut-out is accomplished byreason of the fact that with the combination of the heat from the full line voltage being conducted to the bimetallic armature l2 and a certain amount of heat being conducted to the compensator l1 strip 32 as shown in Figure 3 will strike the insulating tab 2d thus breaking the circuit through that part of the relay which brings about the preheating intervals to the lamp electrodes. Strip 82 is a uni-metal strip secured to bimetal i2.

This condition is illustrated in Figure 2. Once the circuit is broken, the full line voltage is across come this I have arranged the elements as the resistor l, thus keeping the bimetal l2 heated sufliciently to have its end or a contact attached thereto stay closed with the insulating member 2E5.

Figure 4 is another embodiment of this same principle of cutting out the lamp starter under failed lamp conditions. Instead of supporting the armature I2 at an end thereof as in Figure 1, it is supported at a point removed from, but adjacent to an end. The end adjacent the support is curled away from the support it and toward the freeend of the strip l2. tions described above are present and the lamp fails to start, the free end of the armature l2 and the compensator 7 ll will deflect towards the support 5 until the strip, in the process of defleeting, strikes the curled end thereof. In this embodiment the speed with which the cut-out operates is increased for the curled end and the free portion of the armature will be moving towards each other. It should be noted that the end of the bimetallic strip should not be curled too sharply when the relay is initially assembled. If it were it would interfere with the auxiliary or secondary starting apparatus, namely the low resistance contact is which participates in the preheating of the electrodes when the lamp fails-to start the first time. Figure 5 clearly shows the relative positions which the elements of the relay of Figure 4 assume under failed lamp conditions. Thus in either this embodiment or in the others described in conjunction with Figures 1 and 3 at least two pre-heating periods are provided for the lamp before the cut-out operates. It is desirable to provide at least two pre-heating periods as I have done in both embodiments of my relay because it is quite possible that the- -lamp arc would not strike the first time lamp be a good lamp.

What I claimis:

1. A relay for controlling the pre-heating oi the electrodes 0! an electric discharge lamp comprising: a resistance rod having a high resistance; an armature disposed in heat receiving relationship to said resistance; a. high resistance element closed with said armature under dead circuit condition; a compensator irom which said high resistance element is mounted; a low resistance element mounted on said compensator; and an insulating element mounted on said compensatgr at apoint opposite the free end'ot said arma ure.

2. In apparatus for pre-heating the filaments of When thecondiand yet the an electric discharge lamp, a thermally operated switch comprising: a high resistance rod; a bimetallic strip electrically connected to one end of said rod and having a portion thereof in heatreceiving relationship with said resistance rod; an electrical contact closed with said bimetallic strip under dead circuit conditions; a second electrical contact connected to the other end of said resistance rod and in position to have contact established therewith by said bimetallic strip when said strip is distorted by heat; and an insulating element disposed to automatically prevent the bimetallic strip from establishing contact with either of said electrical contacts under abnormal lamp conditions.

3. A relay for controlling the pre-heating of the electrodes of an electric gaseous discharge lamp, said relay comprising: a resistor; a bimetallic strip in position to be distorted by heat from said resistor and having one end electrically connected to one end of said resistor; a low resistance contact connected to the other end of said resistor and near but out of contact with the other end of the bimetallic strip when said resistor is unenergized; a second contact closed to said other end of said bimetallic strip when said resistor is unenergized, said second contact being connected to said other end of said resistor through a second resistor in proximity to said bimetallic strip; and an insulating member disposed to prevent the said other end ofsaid bimetallic strip from closing with said contacts when the line voltage is across the said resistor for an abnormally long time.

4. The combination of claim 3 in which the free end of the bimetallic strip has an extension below the point at which contact is established therewith by the said electrical contacts, the furthermost extremity of said extension being in register with said insulating member. I

5. In a starting unit for an electric gaseous discharge device, a switch assembly including: a heating element; a contact assembly including a supporting arm and a pair of contactsfi and a thermally responsive member lying within the efiective heating range of said element; said thermal member being mounted for movement between said contacts in repetitive starting action, with means for terminating said "repetitive action under failed lamp conditions; said terminating means being so arranged as to hold said thermal member between and out of engagement with said contacts upon the accomplishment of said repetitive action termination.

6. A starting unit for an electric gaseous discharge device, said unit comprising: a plate-like base of insulating material; a panel-like upright of insulating material mounted on said base; a pair of contact pins extending from one side of said base; a pair of lead wires, each connected to one of said contact pins and extending on the other side of said base to form a support for said upright; and a switch assembly connected with said lead wires and mounted on said upright;

said assembly comprising a heating element, a contact assembly including a supporting arm and a pair of contacts, a hook-like thermally responsive member with said heating element lying within the loop portion of said hook, said thermal member being mounted for movement between said contacts in repetitive starting action, and means for terminating said repetitive action under failed lamp conditions; said terminating means being so arranged as to hold said thermal member between and out oi! engagement with said contacts upon the accomplishment of said repetitive action termination.

7. In a starting arrangement for an electric gaseous discharge device; switching means automatically operable to open and close a circuit in repetitive starting attempts for said device; a thermally responsive member arranged for movement to operate said switching means; heater means operable to heat said thermal member to initiate said movement; and means for automatically terminating said repetitive action by maintaining said circuit open after a few .starting attempts; said switching means being formed and arranged for automatic resetting action, upon deenergization or said circuit, to again permit said repetitive starting attempts.

HENRY J. McCAR'I'HY.

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