GB2243487A - A thermal starter switch for fluorescent lights - Google Patents

Abstract

A thermal starter switch for a fluorescent light comprises a housing 10 enclosing a gas filled starter bulb 20 containing a pair of normally closed switch contacts 21a, 21 b which are connected by respective connecting leads 23, 24 to two terminals 40 inserted into the housing 10. When the power is applied, one of the switch contacts 21b is deformed by heating to cause the switch contacts to open which in turn induces a high voltage in a ballast to enable the fluorescent light to be turned on. A control means 30 in one of the connecting leads 23 includes a SCR which is turned on when the power is first applied to allow current to flow through the thermal switch and heat the filaments of the fluorescent light but which is turned off when the fluorescent light is on so that current will not flow through the thermal switch when the contacts 21a, 21 b reclose. <IMAGE>

Description

which is for initiating a high voltage across the two eletrodes 3 & 4. When the power is turned on, a potential difference exists between two filaments 5a of the fluorescent tube 5 and the ballast 6, and between the fixed electrode 3 and the deformable electrode 4 of the high voltage initiating tube 2 of the glow starter (GS). The fixed electrode 3 and the deformable 4 start to discharge because the power voltage is higher than the discharge voltage at the high voltage initiating tube 2. During discharging, the deformable electrode 4 is gradually heated to expand to contact the fixed electrode 3. Thus, the preheating circuit is completed between the filaments 5a of the fluorescent tube 5 and the ballast 6.

The filaments 5a of the fluorescent tube 5 is then gradually heated. Immediately after the connection of the electrodes 3 & BR< 4, the discharging of the high voltage initiating tube 2 stops, then the deformable electrode 4 will be gradually cool down and break the contact. Because of the sudden change in current, a high induced voltage is created in the ballast 6 to cause the filaments 5a to discharge electrons. Finally, the fluorescent tube 5 is turned on.

According to the above-mentioned structure, the two electrodes 3 & 4 are in a normal open status, and when they are connected to form a short circuit by means of discharging process, the preheating current will be provided for the filaments 5a of the fluorescent tube 5. Only after the filaments 5a of the fluorescent tube 5 absorb a sufficient amount of heat energy, the ballast 6 can be induced by the disconnection operation of the electrodes 3 & 4 to provide a THERMAL SWITCH STARTER FOR FLUORESCENT LIGHTS The present invention relates to a thermal switch, specifically to a thermal switch starter for a fluorescent light.

As shown in Figure 1 & 2, the prior art hereby teaches the structure of a glow starter which comprises an insulating casing 1 having therein a high voltage initiating tube 2, being filled with compressed inert gases such as neon or argon and provided a fixed electrode 3 and an deformable electrode 4. Referring to Figure 2, the glow start is then connected with a fluorescent tube 5 and incorporated with a ballast 6 high voltage. Therefore, the fluorescent tube 5 requires more time (about 4 seconds) to be turned on. In the beginning, just after initiation, the discharging process of the electrodes 3 & 4 does not make a stable connection; and this will reduce the service life of the fluorescent tube 5.

Accordingly, the objects and advantages of a thermal switch starter for a fluorescent light of my invention are: (a) to provide a thermal switch starter which can speed up the initiating time; (b) to provide a thermal switch starter whIch can stablize the discharging process and thus prolong its life; (c) to avoid the interrupted connection problem; (d) to provide a secure initiating of the fluorescent tube in low temperature The present invention provides a thermal switch starter for a fluorescent light which is powered from an ordinary electric utility power line and comprises a housing having a starter bulb, a wire, a controlling wire and two terminals thereof.The starter bulb, being filled with a predetermined proportion of compressed inert gases such as helium, neon and argon, has one set of thermal switch including a fixed contact and a deformable contact, being in normal close status and sealed therein.

Extending respectively opposite from the contact portion of the fixed contact and the deformable contact, the wire and the controlling wire are provided for respectively attacnng to the fixed and the deformable contact upper ends and passing through the upper end of the starter bulb to attach to the lower end of the two terminals, therewith the two terminals being respectively and partially inserted into the housing.

The controlling wire has, being connected with the fixed contact, outside the starter bulb upper end and the terminal lower end therebetween formed an integrated circuit (IC) being rovided for ensuring that the current is block thereupon the fluorescent tube being in operation. The compressed inert gases of the starter bulb are for facilitating the ionization of the thermal switch.

In the drawings: Fig. 1 is a schematic drawing shows the structure of the prior art.

Fig. 2 is a circuit diagram of Fig. 1.

Fig. 3 is a perspective plan view of the thermal switch starter for a fluorescent light of the present invention.

Fig. 4 is a circuit diagram of the thermal switch starter for a fluorescent light of the present inventon.

Fig. 5 is an illustrated graph of the temperature/time according to the present invention.

The invention will now be described by way of example.

Referring to Figure 3, the thermal switch starter for a fluorescent light comprises a housing 10 having therein a starter tube 20, from and through thereon respectively extending and passing upwardly a wire 24 and a controlling wire 23 being respectively attached to the lower ends of two terminals 40. The terminals 40 has a lower portion being provided to be inserted into the housing 10 and an upper portion being bigger in size than its lower portion for allowing the terminals 40 to stop against the outer surface of the upper portion of the housing 10.

The portions of the wires 23 & 24, passing through the upper end of the starter bulb 20 being defined as its lower portion, from thereunder slightly extend downwardly to respectively connect with the upper ends of a fixed contact 21a and a deformable contact 21b. The fixed contact 21a and the deformable contact 21b are the components of a set of thermal switch 21 which is sealed in the starter bulb 20. The upper ends of the fixed and deformable contacts 21a and 21b are oppositely spaced from each other. Extending downwardly from their upper ends, the lower ends of the fixed and the deformable contacts 21a and 21b are in contact with each other. The fixed contact 21a is an ordinary conductive metal, the deformable contact 21b is an alloy with different coefficient of thermal expansion. Inside the starter bulb 20 is filled with a predetermined proportion of compressed inert gases 22 such as helium, neon and argon.

On the controlling wire 23 between the outside upper end of the starter bulb 20 and the lower end of the terminal 40, a control means such as an integrated circuit 30 is provided.

In the present embodiment, the critical temperature is set at 60C C. As soon as the temperature reaches 600 C, the deformable contact 21b expands and deforms, due to its different coefficient of thermal expansion, to cause the contact portion i.e., the lower ends of the two contacts 21a & BR< 21b to disconnect from each other.

Figure 4 shows the circuit of the control means s ch as the integrated circuit 30, therein comprising a Silicon Controlled Rectifier (SCR) 31, a diode 32, a Zener diode 53 being placed between the diode 32 and the SCR 31 and, against the diode 32. A resistance-capacitance (RC) circuit 34, being connected in series between the SCR 31 and the Zener diode 33, comprising two parallel-connected resistors 341 & 342 and a diode 343 therebetween a capacitor 344 being connected in series. According to the aforesaid arrangement, the IC 30 enables to automatically turn on/off the SCR 31. The SCR Ql circuit is then connected in series with two resistors 35 & 36 therein each resistance is 68K/4W so as to further increase the voltage drop.

The thermal switch starter is incorporated with a fluorescent tube 5 to initiate high voltages between its two filaments 5a. As shown in Figure 3 & 4, the fixed contact 21a and the deformable contact 21b form an open circuit when power is turned on because of their constant contact. And this permits a high voltage to pass therethrough and directly preheat the filaments Sa of the fluorescent tube 5. During the preheating process, the fixed contact 21a is heated by conduction current to conduct the deformable contact 21b. And the heat causes the ionization of the helium first, then the neon and the argon to collide each other and raise the temperature of the starter bulb.Since the break over temperature of the deformable contact 21b is set at 60 C, (the required heating time of the thermal switch starter approximately 0.4 second), the current circuit will e broken when the contact portion of the fixed contact 21a and the deformable contact 21b is disconnected, by then the filaments 5a of the fluorescent tube 5 are heated to an extent such that the thermoelectrons are emitted. At this moment, the deformable contact 21b deforms and breaks the circuit, the ballast 6 is s.imultaneously induced to initiate a high voltage which forces the thermoelectrons to act on the mecury vapor of the fluorescent tube 5 to emit light.Being different from the prior art, the thermal switch starter is able to directly preheat the filaments 5a and drive the deformable contact 21b to break the current circuit after the preheating process. By this means, the fluorescent light 5 will be immediately turned on after power is applied.

The circuit of the present invention is characterized, as shown in Figure 4, in that 110/220 VAC is provided across the series-connected resistors 35 and 36 to approximately produce a voltage of 37V at resistor 36. Referring to Figure 5, in the beginning, the voltage does not deliever any current during the positive half cycle. During the negative half cycle, current from the resistor 36 passes through the Zener diode 33 and the diodes 32 and 343 to charge the capacitor 344, and then passes through resistors 341 & 342 to trigger the gate of the SCR 31 to allow current to flow during the positive half cycle and directly heat the filaments 5a of the fluorescent tube 5.After the thermoelectrons are ionized within the fluorescent tube 5, the remained volt of the voltage between the two filaments 5a reduces to 50-70V and is shunted through the series-connected resistors 35 & 36. Thus, a voltage of 17-22V is obtained from the resistor 36, and such a voltage is not sufficient to charge the capacitor 344 because it does not exceed the breakdown voltage of the Zener diode 33, so that the SCy 31 is in the nonconducting status. When the thermal switch 21 once again make contact, current will no longer flow through the thermal switch 21.

The deformable contact 21b of the thermal switch 21 can be frequently heated and deformed to break off the contact with the fixed contact 21a, by this means, to protect the ballast 6 and the fluorescent tube 5 from damage by the continual increasing of the temperature. Because the amount of the electric current at the filaments 5a is 1.5 times than that of the fluorescent tube 5 when the fluorescent tube 5 is near the end of its service life.

More over, as shown in Figure 5, the deformable contact 21b of the thermal switch 21 will deform when the heating temperature raises to its breakover temperature. This is because the current will raise the temperature above the breakover temperature which is located at the maxima of its sine curve.

Claims (3)

1. A thermal switch starter for a fluorescent light comprising a housing extending downwardly and having two terminals, a starter bulb, a wire, and a controlling wire being provide with a control means thereof; said two terminals respectively having one end, being partially inserted into one portion of said housing, thereon being connected with said wire and said controlling wire and defined as its lower end, from thereon extending upwardly and attaching to a fluorescent light, an upper end, being bigger than the lower end in size for stopping against the outer surface of said housing upper end;; said wire extending downwardly from the lower end of one of said terminals and passing slightly through the upper portion of said starter bulb; and said controlling wire, extending downwardly from the lower end of the other one of said terminals and slightly passing through the upper portion of said starter bulb, having a control means being placed between said terminal and the outside upper portion of said starter bulb; said starter bulb comprising a predetermined proportion of compressed inert gases and a thermal switch including a a fixed contact and a deformable contact therein;; said fixed contact being made of a conductive metal, and said deformable contact being made of an alloy with different coefficient of thermal expansion for permitting to be deformable by heating, said fixed ana said deformable contacts, being oppositely spaced from each other at their upper ends thereon being respectively connected with said controlling wire and said wire, from thereon extending respectively downwardly and contacting with each other in normal close status before the power being applied; said compressed inert gases, being filled with said starter bulb and provided for permitting the ionization by heating; said control means, being formed on the controlling wire and provided for permitting the controlling of the voltage charging and discharging process and ensurIng the block of the current after the fluorescent light being in operation.

2. A thermal switch starter for a fluorescent light as claimed in claim 1, wherein the breakover temperature of said thermal switch being set at 600 C.

3. A thermal switch starter for a fluorescent light as claimed in claim 1, wherein said control means such as an integrated circuit comprising at least two resistors being connected in series for permitting the reduction of current to a suitable range of voltage, a silicon control rectifier (SCR) circuit including therein a SCR and a diode being connected in series, therebetween a Zener diode being placed opposed to said diode; between said SCR and said Zener diode and in a series-connected manner being formed a resistance-capcitance (RC) circuit, being provided for permitting the automatic control of the operation of said SCR in nonconductive status when said thermal awitch being in contact once again after the fluorescent light being in operation, having another two resistors being connected in parallel, therebetween a diode and a capacitor being connected in series.

4 A thermal switch starter for a fluorescent light substantially as herein described with reference to and as illustrated in Figures 3, 4 and 5 of the accompanying drawings.