US2391680A - Lock-out switch for fluorescent lamp starters - Google Patents

Description

Dec. 25, 1945. L.. w. COOK LOCK-OUT SWITCH FOR FLUQRESCENT LAMP STARTERS Filed Oct. 18, 1943 K, O 9 Mm O. @www nd t er WL/m s mw e L@ Patented Dec. 25, 1945 ,f LOCK-OUT SWITCH FOR FLUORESCENT LAMP STARTERS l Leonard W. Cook,v Stratford, Conn., assignor to General Electric New York Company, a corporation of Application October 18, 1943, Serial No. 506,640

(Cl. ZOU- 122) Claims.

My invention relates to lock-out switchesfor fluorescent lamp starters. Fluorescent lamps provided with starters such as are in common use at the present time sometimes fail to start for one cause or another and the starter continues to make successive efforts to start the lamp until ilnally it damages or destroys itself. The continued flickering of the lamp due to the unsuccessful eiforts of the starter to start it, moreover, is annoying to many people. Itis the object of my invention to provide delay lock-out switch to be starter. In the event that the Y after a reasonable number of starting efforts made by the starter, the switch will open the circuit of the starter and thereby prevent its making further starting eiorts.

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring to' the drawing, Fig. 1 is a cross sectional view of a complete starter and lock-out switch unit; Fig. 2 is a perspective view-of the lock-out switch; Fig. 3 is a detailed View drawn to a larger scale; and Fig. 4 is a circuit diagram. The arrangement of the lamp starter and the lock-out switch as shown on the drawing is similar to of William R. Young and Prescott K. Turner, Serial No. 493,004, led May 3, 1943, of which the present invention is a further development. As in that application the starter I and the lock-out an improved time used with a lamp switch 2 are enclosed in a common casing 3 yand' the two devices are mounted on opposite sides of the insulating plate 4 which is attached to the end or terminal plate 5 closing the lend of the casing.

The purpose of the lock-out switch as explained in the above-noted application is to render the starter inoperative in the event that the lamp will not start after the starter has made a reasonable number of successive unsuccessful attempts to start it. As shown by Fig. 4 the lock-out switch is connected in series with the starter so that after the switch trips open the starter is de-energized until the switch is re-set, as for example by pressing the resetting button 6 which projects from the end of the casing. Firmly secured at one end to the plate 4, as for example by the rivets 1, are the arcing strip 8 which may be of steel and the bimetallic strip 9. At its opposite end the arcing strip is also secured to the plate, being shown on the drawing as passing through the opening I0 and the slots Il in the plate 4 and lamp` fails to startv that shown in the copending application rapidly along on the 'the spring clinched at the other side. The bimetallic strip is bent at its free end to form the latch l2 and the strip is so tensioned that at ordinary room temperature it engages or stands very close to' the arcing strip, the two strips constituting the xed contact member of the switch.

The cooperating movable contact member of the switch is the wire spring i@ which is fixed at one end as by the rivet lli, and extends in a loop represented at l5 at the other side of the plate and has its free end when in closed circuit position between the arcing and the bimetallic strips. The spring is initially tensioned both to press against the arcing strip when in closed circuit position, that is when retained by the latch, and to take a position separated from the arcing strip as represented in Fig. 3 after being released by the latch. As a result of these two tensions the spring rests against the arcing strip when retained 'by the latch and remains in contact therewith notwithstanding the outward movement of the latch when the bimetallic strip is heated. After being released by the latch it slides arcing strip to the end thereof finally opening the circuit. Since the arcing strip extends somewhat beyond the latch any burning or pitting that takes place due to an arc between the spring and the arcing strip is localized and does not interfere with the contact surfaces of the spring and the bimetallic member which members must disengage freely.

The loop I5 in the spring in addition to giving a greater eiiective length serves as a part to be engaged by the resetting button. Burning and carbonizing of the plate 4 is avoided by the opening i0 in the plate near the end of the arcing strip where the arc occurs. As the spring,

after being released, moves along the surface ofv the plate for a short distance beyond the end of the arcing strip before coming to rest'the importance of avoiding any carbonizing of the plate in the path of the arc will be appreciated since should carbonizing be allowed to occur the arc would not be broken.

The bimetallic strip is heated during those successive intervals at which the starter closes the circuit by which the lamp electrodes are heated.

delay action shall be dependable even though the operating current is low due to low line voltage on a fibre glass core I9 the core projecting beyond the end of the coil. Heat is conveyed from the core to the bimetallic stripby the thin steel band 20, the ends of which are brought together and welded to the bimetallic strip and the intermediate part of which is passed around and iirmly clamped to the projecting part of the core. The band 20 also serves to electrically connect one end of the coil winding with the bimetallic strip. The heater coilis jacketed by the ceramic cylinder 2i which is secured in position by cement and the cement also is used to close the lower end of the cylinder.

Each time that the starter closes the circuit of the lamp electrodes to heat them in its efforts to start the lamp the heater coil is traversed by line current and receives an increment of heat. Because of the poor heat conductivity of the nbre glass core and the ceramic jacket of the heater the temperature ofthe heater coil soon rises to a high value which may be approximately 1000n F. and because of the specific heat of those parts an appreciable time is required for them to reach that temperature. The core'and jacket function as a heat reservoir which after attaining a high temperature from a number of successive energizations of the heater coil supplies heat at a restricted rate through the steel strip to the bimetallic strip. By selecting a resistance wire of suitable size, such for example as wire having a diameter of .008 of an inch for use with a 100 watt lamp, one may be certain that the parts constituting the heat reservoir will always getl hot even a'saneeo What I claim as new and desire to secure by Letters Patent of the United Statesl is:

1. A lock-out switch for a fluorescent lamp A starter comprising an insulating plate, a bimetalwith current of the lowest permissible value in the circuit. The bimetallic strip is constructed to warp enough to unlatch the contact spring after attaining a temperature of about 210 F. which is well above any ambient temperature which would be encountered in service. If the heat reservoir `always reaches a temperature of say 1000o F. regardless of voltage variations that may occur one can rely on there being a flow of heat through the steel band suiiicient to cause the bia' metallic strip to open the circuit. Inasmuch as the heat produced by the heating coil is for the most part stored since it is not lost to an appreciable amount by conduction through the ceramic jacket because of its poor conductivity and is not conducted to the bimetallic strip through the restricted path provided by the steel strip to an ap- 'preciable degree until a high temperature is reached, the time delay action of the switch is very dependable even over the wide range of operating conditions encountered in service. In other words, the variation in the time delay with the variations in the line voltage encountered in service is relatively small.

lic contact strip secured at one end thereto, a i

heater associated with said strip for causing the free end thereof to deect away from said plate,

said strip having a latch at itsfree end, a co-` operating contact wire mounted on said plate for engagement with said strip, said wire being biased to disengage said strip when released by said latch, and an arcing strip mounted on said plate in electrical connection with said bimetallic strip, said arcing strip extending beyond said latch and arranged to engage said contact wire on the side thereof opposite to that engaged by said bimetallic strip.

2. A lock-out switch for a fluorescent lamp starter comprising an insulating plate, a bimetallic contact strip secured at one end thereto and having a latch at its free end, a heater associated with said strip for causing the free end thereof to deflect away from said plate, an arcing strip secured to said plate beneath said bimetallic strip and in engagement therewith, a resilient contact wire secured to said plate and arranged to be retained by said latch in engagement with said arcing strip, said contact wire being tensioned to e core formed from low conductivity material posil tioned within said enclosing means adjacent to said resistance heater, and means having good heat conductivity connected to said core and forming a restricted path for conveying heat from said heater to said thermal member.

4. A time delay lock-out switch for a iiuorescent lamp starter comprising cooperating contacts, a thermal member for moving one of said contacts relative to the other, a resistance heater coil having a low heat conductivity core and a low heat conductivity enclosing member, and a member having good heat conductivity connected to said core and providing a restricted path for the transfer of heat from said core to said thermal member.

5. A time delay lock-out switch for a iluorescent lamp starter comprising a fixed contact, a bimetallic strip having a cooperating contact, a resistance heater coil, a ceramic jacket enclosing it, said coil having a fibre glass core constructed to project beyond the coil at one end thereof, and`

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