US2503908A - Fluorescent lamp starting apparatus - Google Patents

Description

Apnl 11, 1950 J. H. HILDERINK FLUORESCENT LAMP STARTING APPARATUS Filed Jan. 15, 1949 Invehtor: Johannes Hild er-ink,

logldfi His Attorney- Patented Apr. 11, 1950 UNITED STATES PATENT OFFICE FLUORESCENT LAMP STARTING APPARATUS Johannes Hendrikus Hilderinlr, Eindhoven, Netherlands, assignor to General Electric Company, a corporation of New York Application January 15, 1949, Serial No. 71,068 In the Netherlands February 7, 1948 pressed across the lamp from a ballast device to start the arc in the lamp.- In other prior art starting devices, the starting switch unit includes not only the starting switch, but also a lock-out switch by which the starting switch is rendered inoperative after it has made a number of unsuccessful attempts to start the lamp. In some cases, the lockout switch is manually reset, but

i 3 Claims. (Cl. 200122) by a condenser 6, and are further shunted by a circuit including a starting switch 1 and a thermal switch 8. The starting switch 1 consists of an interrupter which is able to open and close its contacts repeatedly in an automatic manner. The switch I may, for example, be a glow discharge, bi-metallic switch as indicated more perticularly in Fig. 2.

According to the present invention, the thermal switch 8 is of improved construction, making possible an improved starting device assembly.

In general, the thermal switch comprises a therin others it is automatically reset. The lockout switch mechanism usually comprises a thermal switch which includes a thermal element such as a bi-metallic strip carrying a contact which cooperates with a fixed contact, these contacts being normally closed when the device is cold. If the lamp fails to start, the two contacts are separated by the bi-metallic strip which is heated by locally supplied heat produced by the flow of current through a resistor.

It is an object of this invention to provide an improved automatic reset starting device for fluorescent lamps which is inexpensive to manufacture and is accurate and reliable in operation. A further object of this invention is to provide an improved thermal switch element which may form a part of such a starting device or may be used for other purposes.

The above and other objects of my invention as well as the manner of carrying out the same will best be understood from the following description taken in connection with the accompanying drawing in which Fig.1 is a schematic diagram of a fluorescent lamp starting circuit including a partial longitudinal sectional view of an improved thermal switch in accordance with the invention and Fig. 2 is an'expanded perspecmal responsive contact element and two heating resistances therefor, one resistance being connected in series with the contacts and the other being connected effectively in parallel with them. The purpose of the series resistance is to heat the thermal element so that it will open the switch contacts, thereby breaking a circuit ineluding these contacts when the circuit is traversed by 'a continuous or intermittent current which exceeds a given value and persists for too long a time. The purpose of the parallel resistance is to maintain the contacts open after they have been so opened.

As illustrated in the drawing, an improved thermal switch comprises a hollow cylindrical supporting element 9 which is preferably made of a ceramic material. A resistance element l0, heretofore referred to as a series resistance, is mounted within the tube 9 in any suitable manner. It may, for example, comprise a resistance wire supported within the tube by end closures ll. One end of the resistance l0 may terminate in a wire l2, the end of which may serve as one of the contacts of the switch.

On the outside of the tube 9 there is mounted a resistance element l3, heretofore referred to as the parallel resistance. The resistance I3 is preferably in the form of a coating of resistance material suitably formed on the exterior surface of the tube 9. Connections to the resistance l3 may be made-by conductive rings l4 and I5.

A thermal element such as a heat responsive bimetallic strip I6 is also mounted on the outside of the tube 9 and sufficiently close to the latter so that the thermal element may be affected by heat from the resistors. For this purpose, one end of. the bi-metallic strip may be secured to the ring I4 as by welding, the strip extending substantially parallel to the exterior of' the tube 9 over substantially the portion covered by the resistance l3, the other end of the strip [6 being formed into or having mounted thereon. a contact l'l.

3 In the circuit of Fig. 1 the free end of the series resistance I is connected to the starting switch 1; the other end, terminating in the wire I2, makes contact with the bi-metallic strip I6 which in turn is connected to the ring I4 and thereby to the parallel resistance I3. The resistance I3,

by its connecting rings I4 and I5, is further connected in shunt across the lamp electrodes 2 and 3 and is thereby similarly connected across the power source when the switch 6 is closed.

The lamp starting circuit of Fig. 1 can now be traced from the right power terminal through the main switch 4. the electrode 2, ring I4, thermal element I8, through the contacts to the wire I 2, series resistance I0, starting switch I, electrode 3, ballast 5, and thence to the left power terminal. In addition, as previously mentioned, the resistance I3 is connected in shunt across the electrodes 2 and 3.

The starting switch I may be a manually operated switch, but preferably is an automatically operated switch of the glow tube type, as better illustrated in Fig. 2. Such a glow switch may comprise a sealed glass tube containing a gaseous atmosphere at reduced pressure and two electrodes I8 and I9 normally spaced 2. short distance apart. The electrode I9 is preferably constituted by an end of a thermal responsive element such as a bi-metallic strip whose other end is suitably mounted within the tube. suitable magnitude is impressed across the electrodes I8. and I9, which are normally open, a glow discharge takes place between them and generates sufiicient heat to cause the thermal responsive element to deflect and thereby to bring the electrode I9 into contact with electrode I8 and close the circuit between them. As soon as the contacts close, the glow discharge disappears, and the thermal element cools, separating the electrodes I8 and I9.

The operation of the starting circuit is then as follows: When the main switch t is closed, the switch I is closed as just described, completing a series circuit through ballast 5, the thermionic electrodes 2 and 3 and series resistance I0. After a predetermined period of time, which is designed to provide an adequate heating time for the electrodes 2 and 3 to bring them to a suitable electron emitting temperature, the switch I is opened, whereby a high voltage produced by the ballast is impressed across the lamp electrodes thereby starting the lamp. Should the lamp fail to start, the operation must be repeated, that is,

closing and reopening the switch I.

After a predetermined number of starting attempts, the current which flows through resistance It produces sufiicient heat which, after passing through the walls of tube 9, causes the bi-metallic element I6 to deflect and to open contacts I1 and I2, thereby opening the lamp starting circuit. The resistance l3, being effectively connected in parallel with the contacts I! and I2, is then connected across the power source and rapidly supplies sufficient heat to keep the bi-metallic element IS in deflected condition and the contacts I2 and I! open. The resistance I3 will be deenergized when the switch 4 is opened or-when the lamp I is replaced. In either case. when the resistance I3 has cooled sufficiently, thermal element I6 will again close contact I I and I2, restoring the switch to its initial condi tion.

It will be observed that by the unique construction of the thermal switch described above, a number of advantages are secured. The bi- When a voltage of metallic element It is shielded by the ceramic tube 9 from heat produced by the resistance I 0 for the necessary period of time to produce the required time delay to permit only a desired number of starting operations before the operation of the thermal lockout switch, that is, the opening of contacts l1 and I2. Simultaneously with the heating of the thermal element I6 by the heat produced by the resistance I0, the resistance I3 will also be warmed. whereby when the contacts I2 and I? open and the resistance I3 is placed across the power source, the heat which it supplies is immediately available to hold the bimetallic element I6 deflected with the contacts in opened condition. It is possible with this arrangement to provide the desired sensitivity; that is, to prevent reclosing of the contacts once they have been opened, while at the same time keeping the current consumption of resistance I3 at a minimum.

A further advantage of the thermal switch construction is that it makes possible an improved design of starter assembly. As best illustrated in Fig. 2, all the starting elements, namely condenser 6, starting switch i, and lockout switch 8 are easily mounted on a base 20 of conventional size and provided with conventional terminals 2i and 22. All the elements can be mounted and supported by their respective leads without the necessity of using speciai supporting plates or partitions for the various lockout switch elements as has heretofore been the case. Manufacture and assembly of the complete starting device is hereby greatly simplified and its cost reduced.

It will be understood that the various elements shown in Fig. 2 are shown in expanded relation to each other and that in practice they are assembled close together so that they can all be enclosed by a cylindrical cover 23 just fitting over the circular base 29.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. A thermal switch comprising a hollow tubular supporting means of insulating material, end

' closures for said member, a heating resistance element supported within said member by said end closures, a coating of relatively high resistance material covering a portion of the outer surface of said member, a pair of conducting ring terminal members surrounding said supporting member and in electric contact with said high resistance coating substantially at the respective ends thereof, a bi-metallic strip having one end secured to one of said ring terminal members and conducting means extending from one end of said first mentioned resistance element into contacting relation with the free end of said bi-rnetallic strip.

2. A thermal switch comprising a hollow tubular supporting member of insulating material, a heating resistance element supported within said member, a second resistance element 'of relatively high resistance material disposed over a portion of the outer surface of said member, a bi-rnetallic strip having one end mounted on said member and electrically connected to one end of said second resistance element and disposed close to the outer surface of said member for actuation by heat emanating from said member and the resistance element on the outer surface of said member, and conducting means extending from one end of said first mentioned resistance element into contacting relation with the free end of said bi-metallic strip.

3. A thermal switch comprising a hollow tubular supporting member of insulating material, a

heating resistance element supported within said member, terminal means on said member at opposite ends thereof for making electrical connection to said element, a second resistance element of relatively high resistance material disposed over a portion of the outer surface of said member, additional terminal means on said member for making electrical connection to said second resistance element, a bi-metaliic strip having one end mounted on said member and electrically connected to one end of said second resistance element and disposed close to the outer surface of said member for actuation by heat emanating from said member and the resistance element on the outer surface of said member, and conducting means extending from the terminal means con- 6 nected to one end of said first mentioned resistance element into contacting relation with the free end of said bi-metallic strip.

JOHANNES HENDRIKUS HILDERINK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number

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