US2936403A

US2936403A - Automatic starter switch for the ignition and operation of fluorescent lamps

Info

Publication number: US2936403A
Application number: US749080A
Authority: US
Inventors: Knobel Fritz
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-07-19
Filing date: 1958-07-17
Publication date: 1960-05-10
Anticipated expiration: 1977-05-10

Description

May 10, 1960 F. KNOBEL 2,936,403

AUTOMATIC STARTER SWITCH FOR THE IGNITION AND OPERATION OF FLUORESCENT LAMPS Filed July 17, 1958 15 ummillll ll llllIfllllillllllllll United States Patent "ice AUTOMATIC STARTER SWITCH FOR THE ,IGNI- TION AND OPERATION OF FLUORESCENT LAMPS This invention relates to automatic starter switches for the ignition and operation of fluorescent lamps having at least one heated cathode.

Automatic starter switches are used for igniting fluorescent lamps having heated cathodes and have the function, to automatically raise upon manually switching on the light switch, the temperature of the cathodes to the optimum temperature, and to produce a sufficiently high induction voltage for ignition of the lamp upon interruption of the ignition circuit in combination with a choke connected in series-with the lamp.

The most common starter switch of this kind is the so-called glow discharge starter which is provided with normally open bimetal contacts which, when heated by a glow discharge, close after a period which is not accurately timed, and then open again. With short lamps it may occur that they are ignited when the power switch is turned on and before the starter contacts are closed. These so-called cold starts with unheated cathodes are very harmful to the lamps and they considerably shorten the life of said lamps. On the other hand, the glow discharge initiating immediately upon opening of the starter contacts causes an attenuation of induction peak voltages. This decreases the igniting reliability, especially when the ambient temperature is low. Further, after a certain operating time, the changes in the igniting potential limit the troublefree operation to some thousand operating hours. When the housing containing the glow discharge tube is made according to the international specification, the glow discharge starter occupies so much space that there remains not enough space to house a sufficiently rated condenser, i.e. a condenser according to specifications. The glow discharge starter now in use does therefore not meet the international specifications. Outside of these disadvantages the glow discharge starter has the advantage of being extremely simple and cheap. This is the reason why this starter in combination with a bayonet socket fitting thereto is in extensive use in illumination systems, despite of the disadvantages mentioned before.

Other automatic starter switches known in the prior art comprise four terminals and cannot be inserted to replace a starter switch in the socket having two terminals.

Other starter switches known inthe prior art comprise a two-terminal socket and a magnet relay which has a .very complicated and expensive design. This design often is subject to trouble. In most of the cases electromagnetic operating starter switches have the disadvantage that they are not fully noiseless and that they aretoo sensitive to voltage changes in the power line.

It is therefore an object of the invention to provide a save starter switch with bimetal contacts fitting into a housing dimensioned according to the international specifications.

It is another object of the invention to provide a starter switch which prevents cold starts which are detrimental to the life of the lamp. 7 7

It is another object of the invention to provide, a

2,936,403 Patented May 10, 1960 starterswitch operating independently of the ambient temperature.

It is another object of the invention to provide a starter switch having an ignition condenser of suflicient size housed in a housing dimensioned according to international specifications.

It is another object of the invention to provide a starter switch with only two terminals and which is exchangeable with glow discharge starter switches.

A still further object of the invention is to provide a starter switch which can be adjusted without opening the housing.

Another object of the invention is to provide a starter switch which requires only a fraction of the space in a housing which is dimensioned according to international specifications.

. It is another object of this invention to provide a method for adjusting a starter switch.

' Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing, in whichz' j Fig, 1 is a perspective diagrammatical view of the starter switch,

Fig. 2 a fragmentary view of another embodiment of the invention,

Fig. 3 an electrical diagram for the embodiment of F Fig. 4 an electrical diagram of antauxiliary power supply device, .and

.Fig. 5 a perspective fragmentary view of another embodiment.

From the power line 1, 2 the circuit leads over a power switch 3, a choke coil 4 and the cathodes 6, 7 of the fluorescent lamp 5 to the terminals 8, 9 of the connecting socket of the starter device. On the base plate 19 two resiliently mounted

bimetal strips

10 and 11 are so arranged that they co-operate with their normally closed contacts 12 and their normally open contacts 13. The deformation of these two bimetal springs occurs in the same sense. In the temperature range from -20 C. to C. the deformation is of the same magnitude. Therefore, in the rest position of these contacts, the adjusted contact pressure remains constant within this temperature range. 7

The bimetal strip 10 which according to Fig. 1 is designed as alow ohmic resistor is at one point so closely surrounding the high ohmic resistor 14, that heat from that resistor 14 will be easily transmitted to the bimetal strip 10. The high ohmic resistor is connected in series with the condenser 15 to the two terminals 8, 9. An ignition condenser 16 and an attenuation resistor 17 is connected to the two terminals 8, 9 parallel to the lamp 5. The

condensers

15, 16 and the resistor 17 are moulded into the housing by means of a plastic material. The housing 18 is of the same size as one of a usual glow discharge starten This size corresponds to the international specifications. Due to the horizontal disposition of the bimetal strips, only about one third of the space in the housing 18 is required for the location of these strips, the contacts and the heating resistors, even when the required spacings to prevent sneak currents are met; as can be easily seen from Fig. 1. Therefore, the remaining space will be large enough to locate there the

condensers

15, 16 and the resistor 17, these being of sufficient size to insure perfect operation and to meet the prescribed specifications. In conventional glow dis charge starters the glow discharge tube requires so much space, that no sufiiciently large condenser can be placed into the remaining space. These prior art glow discharge starters therefore do not correspond to the international specifications. a

The described starter switch operates as follows:

Immediately upon switching-on the power switch 3 a heating current is flowing through the choke coil 4, the lamp cathode 6 to the terminal 8 of the starter switch, which is electrically connected to one end of the bimetal strip 10 by means of a rivet, through the normally closed contact 12, the rearward end of the bimetal strip 11 to the terminal 9, and from there through the other lamp cathode 7 back to the power line. The heating current heats the two lamp cathodes 6 and 7 and also the bimetal strip 10, which, in order to increase its electrical resistance, is considerably smaller than the bimetal strip 11. Due to the heat the bimetal strip 10 will bend upwardly. The normally closed contact 12 is opened and the voltage induced into the choke coil 4 ignites the arc in the lamp 5, which is now used to keep the normally closed contact 12 open, the high ohmic resistor 14 now providing the heating of the movable bimetal strip 10. This resistor could, in principle, be connected parallel to the lamp 5, i.e. to the terminals 3 and 9. But in order to avoid an attenuation of the induction voltage, and to increase the reliability of ignition, especially when the ambient temperature is low, the resistor 14 shown in the diagram of Fig. l is not connected directly parallel to the lamp 5, but by the intermediary of a condenser 15. It is further important, that the thermal inertia of the high ohmic resistor 14 is very low so that the heating of this resistor 14 is effective on the bimetal strip 10 before the contacts 12 close again after being opened. The low thermal inertia of the high ohmic resistor 14 offers the additional advantage, that upon opening the ignition switch, i.e.

switching-oh the lamp, this resistor cools off very quickly, and, since the thermal inertia of the bimetal strip 10 is also very small, the switch elements return fast to their initial position and the starter switch is quickly ready again for operation.

The low thermal inertia of the resistor 14 of the starter switch shown in the drawing is obtained, because the resistor 14 consists only of a small mass weighing less than 0.1 gr., and because only a thin lacquer film provides the electrical insulation against the bimetal strip 10, so that a good heat transfer, e.g. by convection, is provided between the resistor 14 and the bimetal strip 10.

It may, however, occur, that the lamp does not fire upon the first opening of the contacts 12, when this opening occurs at an unfavorable moment with respect to the momentary value of the current. Then, the resistor 14 will not be heated by the arc voltage of the lamp 5, but by the considerably higher line voltage. In order to prevent this, an additional normally open contact 13 is provided, which connects the terminals 8 and 9 as soon as the voltage on these terminals exceeds considerably the arc voltage of the lamp. At this moment the heating current is flowing from the terminal 8 through the normally open contact 13, through the stationary bimetal strip 11 to the terminal 9. The parallel resistor 14 no longer receives a voltage and cools off so that the contact 13 opens again and causes the firing of the lamp, which firing had failed before, when the normally open contact 12 broke the circuit. The normally closed contact 12 is used only once for the ignition, whereas the normally open contact 13 repeats the operation of igniting until the lamp 5 is ignited. Because the lamp 5 is always first shunted by the normally closed contact 12 when the power switch is turned on and because the heating current which is limited by the choke coil 4 immediately heats up the two lamp cathodes 6 and 7, socalled cold starts are completely avoided. Cold starts would be harmful to the lamp 5 and reduce very considerably the life of it. The normally open contact 13 which is connected to the movable bimetal strip is of course electrically insulated from that strip and connected .bya flexible copper wire 21 to the terminal 8. A condenser 16 in series with the attenuation. resistor 17 is preferably connected parallel to the lamp 5, i.e. between the terminals 8 and 9. This condenser 16 serves additionally as a condenser to prevent radio interference and as an ignition condenser, the condenser 15 being strongly attenuated in this function by the high ohmic resistor 14. The resistor 17 serves only as attenuation resistor to prevent as well as possible the wear and the welding together of the

silver contacts

12 and 13. The effect provided by the condenser 16 to prevent radio interference can be substantially increased, if instead 'of a simple choke coil 4, as shown in the diagram of Fig. l, a choke with two symmetric windings is used, as shown in Fig. 3.

In an embodiment of an automatic starter switch according to Fig. l for the ignition and operation of a common 40 watt fluorescent lamp rated for 0.42 amperes operating current and about volts arc voltage, parts with substantially the following technical data have been successfully employed:

Resistor 14: R==l5,000 S2 to 20,000 9 Dimensions: Diameter 0.039

Length 0.236 Weight: less than 0.1 gram. Condenser 15: Capacity C=0.l3 ,uF Condenser 16: Capacity C=0.02 F Resistor 17: R=5 to 10 S2 Bimetal strip 10: 0.039"' 0.0047", weight: less than 0.05

gram Bimetal strip 11:-0.1l8l" 0.0047".

The

condensers

15 and 16 and the resistor 17 were directly moulded with a plastic material into the upper part of the housing 18 having the dimensions Dia. 0.8268" 1.3386" In order to make the dimensioning of the movable bimetal strip independent from the heating current, which is particularly of advantage for lamps of low wattage the heating of the movable bimetal strip can indirectly be effected by a helical heater placed near the stationary end of the bimetal strip 10. The helical heater is heated by the current flowing through it. This possibility is shown in Figures 2 and 3. There the heating current is flowing from the terminal 8 over the low ohmic heating resistor 20 which also heats by heat radiation the bimetal strip 10 at the bent portion, so as to cause the normally closed contact to be opened. The other function is again exactly the same as in the embodiment described before which employs direct heating for the bimetal strip 10.

The values of the

heating resistors

14 and 20 and of the condenser 15 can be adjusted for the different lamp wattages and types of lamps. The heating-up time which is required for a certain type of lamp can be regulated within a wide range by adjusting the distance between the heating resistor and the bimetal strip 10. It is important that the starter switch according to the invention enables to choose the thermal inertia of the switching system in such a way that this latter, in dependence of the ambient temperature, very closely corresponds to that of the lamp cathodes 6 and 7, to thus make sure that the preheating of the lamp cathodes to the favorable temperature takes place before the ignition and independently of the ambient temperature.

The combined function which consists in that the normally closed contact is opened with a delay depending on the heating current, and then is kept open in dependence of the arc voltage of the lamp, which is negative to the lamp current and the line voltage, insures a considerable independence of the safe operation, even from relatively wide fluctuations of the line voltage.

In the embodiments of Figs. 1 and 2 the high ohmic resistor 14 is a commercial miniature carbon metallic resistor. As experiments have proved, it is also possible to manufacture this resistor of a semi-conducting material so that the resistance will be dependent on temperature or voltage, and to solder the resistor with the one metallized end to the bimetal strip 10. Especially the type of resistor as it is .cornmerciallyxavailable from g Philips under the designation VDR, and which resistor consists of a voltagedependent material, could be employed in such manner that the deformation of the bimetal strip 10 will be substantially constant within a large voltage range as it may occur under extremely bad line conditions.

The auxiliary power supply device shown in Fig. 4 serves for the adjusting of the starter switch when it is manufactured. Connected to the power line 21 is a regulating transformer 22, the secondary voltage of which can be regulated at wish by moving a contact 23, whereby the adjusted voltage can be read from a volt meter 24. Connected into the secondary circuit of the transformer 23 is a regulating resistor 25, an incandescent lamp 26 and an ammeter 27. The starter switch which can be designed as shown in Figures 2 and 3 is connected to the

terminals

28, 29 to be adjusted and tested. By adjusting the regulating resistor 25, the current in the ammeter 27 is adjusted so as to be equal to the smallest possible preheating current of the fluorescent lamp for which the starter device is designated. For a 40 watt lamp as it is in common use and operating at 0.43 A. operating current and 103 v. rated are voltage, this smallest possible preheating current is 0.38 A. The voltage on the volt meter 24 is further adjusted such that it corresponds to the lowthis resistor 20 to the bimetal strip 10. In this way, the

heat transfer caused by radiation is altered until the de- 1 sired delay in switching is obtained. When, after this delay in switching, the normally closed contact 12 opens, the lowest possible arc voltage, as adjusted on the voltmeter 24, is applied to the starter switch. With this are voltage the normally closed contact must securely remain open. If this is not the case, it has to be accordingly adjusted by bending the bimetal strip 11. With the described auxiliary device it is therefore possible to adjust with one measuring the delay in switching as well as the keeping open of the normally closed contacts at the occurring lowest possible current and voltage values.

After the adjusting of the normally closed contact 12 a voltage corresponding to maximum voltage of the respective type of lamp can be adjusted on the transformer 22 of the auxiliary device by moving the contact 23. This test voltage is e.g. 130 v. for the usual 40 watt lamp. Now, the control is made to be sure that the normally open contact 13 does not yet close at this voltage. Then a voltage is adjusted on the transformer 22 which corresponds to the lowest permittable no-load voltage. This voltage is for a 40 watt lamp according to international specifications e.g. 140 v. Now it can be checked that the normally open contact closes securely at this voltage.

In the embodiment according to Fig. an adjusting

screw

31, 32 screwed through the insulating base plate 19 is acting on every

bimetal strip

10, 11. By screwing in the screw 31 the contact pressure on the contact 12 is increased, whereas this contact pressure is reduced when the screw 32 is tightened. By screwing in the one or the other screw in the direction of the arrows, the contact pressure accordingly can be varied. An adjusting screw could also act only on one of the two bimetal strips, whereby the contact pressure could also be increased or decreased by tightening or loosening the screw. Because the adjusting screws traverse the base plate 19, the contact pressure can be regulated without first opening the housing.

I claim:

1. An automatic starter switch for the ignition and operation of a fluorescent lamp comprising a housing including a connecting socket having a pair of terminals,

g a fluorescent lamp cathode heating circuit connecting said pair of terminals, said circuit including a temperature sensitive means, a low ohmic resistor for heating the temperature sensitive means and a normally closed contact operated by said temperature sensitive means to open when the temperature sensitive means is heated, a high ohmic heating resistor bridging said normally closed contact and adapted to heat the said temperature sensitive means and maintain said normally closed contact open when the fluorescent lamp is ignited, and a normally open contact bridging said pair of terminals and said cathode heating circuit and operated by the temperature sensitive means to close when heated by said high ohmic resistor upon failure of the fluorescent lamp to ignite, said high ohmic heating resistor having a low thermal inertia whereby to exert a fast heating and cooling effect on said temperature sensitive means.

2. An automatic starter switch for the ignition and operation of a fluorescent lamp comprising a housing including a connecting socket having a pair of terminals, a fluorescent lamp cathode heating circuit connecting said pair of terminals, said circuit including a temperature sensitive means and a normally closed contact operated by said temperature sensitivemeans to open when the temperature sensitive means is heated, a high ohmic heating resistor bridging said normally closed contact and adapted to heat the said temperature sensitive means and maintain said normally closed contact open when the fluorescent lamp is ignited, and a normally open contact bridging said pair of terminals and said cathode heatingcircuit and insulated from but operated by the temperature sensitive means to close when heated by said high ohmic resistor upon failure of the fluorescent lamp to ignite.

3. An automatic starter switch according to claim 1 wherein said high ohmic heating resistor is located in intimate relation to said temperature sensitive means whereby heat is quickly transferred thereto.

4. An automatic starter switch according to claim 1 wherein said temperature sensitive means is horizontally positioned in said housing and together with said normally closed and open contacts and said low and high ohmic resistors occupy only a small part of the vertical 1 space available 'in said housing, and an ignition condenser of relatively large size positioned in the remaining vertical space and occupying approximately all of the remaining space of said housing.

5, An automatic starter switch according to claim 1 wherein an ignition condenser and an attenuation resistor in series are additionally provided bridging said pair of terminals.

6. An automatic starter switch according to claim 1 wherein is additionally provided a condenser connected in series with said high ohmic heating resistor in bridg ing relation to said normally closed contact.

7. An automatic starter switch according to claim 5 wherein said ignition condenser and said attenuation resistor together with an additional condenser in series with said high ohmic resistor are positioned in the upper part of said housing and molded therein by means of plastic material.

8. An automatic starter switch according to claim 2 wherein said temperature sensitive means comprises a first and a second bimetallic strip, said normally closed contact being operated to open by said first bimetallic strip upon heating thereof, the movable part of said normally open contact being insulatedly carried by said first bimetallic strip and the stationary parts of both said normally closed and open contacts being carried by said second bimetallic strip, said bimetallic strips having the same deformation characteristics with respect to changes in temperature so that undue changes in contact pressure are avoided.

9. An automatic starter switch according to claim 1 wherein said high ohmic heating resistor comprises a carbon metallic resistor provided with a lacquer insulation and having a diameter of approximately 0.039 inch and a length of approximately 0.236 inch.

10. An automatic starter switch according to claim 1 wherein said high ohmic heating resistor comprises a voltage-dependent semiconductor material having a metallized surface which is soldered directly to said temperature sensitive means.

11. An automatic starter switch according to claim 1 wherein said high ohmic heating resistor has a weight of less than 0.1 gram and is positioned close to a portion of said temperature sensitive means, said means having a weight of less than 0.05 gram whereby to obtain a low thermal inertia and fast operation of said normally closed and open contacts.

12. An automatic starter switch according to claim 1 wherein is additionally provided a regulating means engaging said temperature sensitive means and extending through said housing for adjusting from the outside thereof, said regulating means being adapted to adjust the contact pressure of said normally closed and open contacts.

13. An automatic starter switch according to claim '8 wherein said first and second bimetallic strips each have a U-shaped mounting end secured to an insulating portion of said housing, and an adjusting screw is threaded through said insulating portion of the housing and bears against the bight of the mounting end of one of said bimetallic strips.

14. A method of adjusting a fluorescent starter switch 30 open contact and a heating element adjacent thereto, comprising passing through the switch the smallest possible preheating current for a fluorescent lamp with which the starter switch is to be used, measuring the delay time for the switch to open, varying the distance between the heating element and the heat responsive element until the desired delay time is attained, passing a voltage through the switch which is the lowest possible arc voltage of the lamp when the normally closed contact is open, determining whether this voltage will cause said contact to remain open, varying the distance between the normally closed contact and a contact on the heat responsive element to a position where said voltage causes said normally closed contact to remain open.

15. The method of claim 14 comprising passing a voltage through the starter switch corresponding to the maximum arc voltage of the lamp, determining whether the normally open contact closes at this voltage, adjusting said contact to a position where it remains open at this voltage.

16. The method of claim 14 comprising passing a voltage through the starter switch corresponding to the lowest permittable no-load voltage for the lamp, determining whether the normally open contact closes at this voltage, adjusting said normally open contact to a position where it securely closes at this voltage.

McCarthy Aug. 10, 1943 Smith et al Aug. 8, 1944