WO1994000963A1

WO1994000963A1 - Incandescent globe power reducer

Info

Publication number: WO1994000963A1
Application number: PCT/AU1993/000309
Authority: WO
Inventors: John Penglase
Original assignee: John Penglase
Priority date: 1992-06-25
Filing date: 1993-06-25
Publication date: 1994-01-06
Also published as: CN1081554A

Abstract

A power reducer (10) comprising an adaptor (11) and a reducer circuit (12) for coupling between an incandescent globe (13) and a socket (14). The power reducer (10) reducing the voltage of operation and/or the in-rush current experienced by the incandescent globe (13) at turn-on for extending the operating life of the incandescent globe (13). An incandescent globe including the power reducer (10) is also described. During normal running the incandescent globe (13) operates substantially at its full rated power.

Description

TITLE INCANDESCENT GLOBE POWER REDUCER

FIELD OF THE INVENTION

The present invention relates to a power reducer for use in relation to incandescent globes. More particularly the invention relates to an adaptor capable of fitting between an incandescent globe and a socket carrying the globe, so as to reduce the voltage received by the globe and to reduce the in-rush current to the globe. The invention also relates to an electronic device for use with or inclusion in an incandescent globe for reducing the power delivered to the globe.

BACKGROUND OF THE INVENTION The operational life of an incandescent globe is primarily governed by: the temperature at which it operates; the voltage at which it operates; and, the in-rush of current experienced at turn-on of the globe. For example, if a globe is operated in excess of its rated ambient temperature then its operating life is substantially reduced. Also, if the glove is supplied with electrical power in excess of its rated voltage than its operating life is also substantially reduced. The reduction in life increases more rapidly than the excess in temperature or voltage. For example, operating a 240 vac glove at 250 volts (i.e. 4% above rated voltage) decreases the operating life by much greater than 4%. Also, operating at excess voltage causes the glove to operate at excess temperature and so has a compounding effect on shortening the operational life of the globe. Further, whilst the operating or "hot" resistance of a 100 Watt, 240 volt AC globe is 576 ohms its "cold" resistance is about 40 ohms.

Hence, at initial turn on the globe draws about 6 Amps. This reduces gradually as the globe warms up over about the first 10ms or so from turn-on. however, during this time the current creates a very large alternating magnetic field which tends to shake the filament of the globe and eventually break it. This is why most globes fail at turn- on.

These problems can be alleviated by reducing the operating voltage of the globe and the in-rush current. In the majority of cases the electrical power to operate the globe is provided by an independent utility company or authority and so reduction of the supply voltage is not feasible. Hence, it is necessary to reduce the voltage at or near the globe.

It is known in the prior art to use active circuits to vary the power supplied to an incandescent globe so as to control its brightness. This is typified by US 3893019 (KINGI), US 3836814 (RODRICUEZ), US 3781593 (RODRIGUEZ), AU 12179/88 (IYXX INC.) , GB 2110010 (MICROSCANDA LIMITED), and GB 1460006 (MOORES). In each of these inventions the active device electronically disconnects the incandescent globe from the supply of the electrical power for a portion of each cycle of alternating current (ie. 50 or 60 times per second). These have the disadvantage of producing RF interference and is relatively complicated. Also, these patents and patent applications are concerned only with operational brightness and not the transient situation at turn-on of the globe. It is also known in the prior art to use a diode to remove half of the alternating current from the globe. This is typified by US 4005334 (ANDREWS), 4117376 (ANDREWS) and US 3963956 (BEINING). In each of these patents an axial diode is used to allow only half of the electrical power to flow through the globe. These have the disadvantage of severely reducing the globe brightness and do not reduce the instantaneous in-rush current.

This can better be done by placing a power reducer in series in circuit with the globe wherein the power reducer operates at turn-on only. The in-rush current can thus be reduced by increasing the resistance of the globe when in circuit with a device whose resistance change as it heats up to its own operating temperature. The supply voltage at turn-on can be similarly reduced.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a power reducer for an incandescent globe to increase the operating life of the globe.

In accordance with one aspect of the present invention there is provided a power reducer for an incandescent globe, the power reducer comprising: a voltage reduction means for dissipating electrical energy at turn-on of the incandescent globe and to dissipate substantially no electrical energy thereafter; and, a circuit connection means for connecting the voltage reduction means into circuit with the incandescent globe; whereby, in use, the voltage reduction means increases the operating life of the globe by reducing transient power surges in the incandescent globe at turn-on.

In accordance with another aspect of the present invention there is provided a power reducer for an incandescent globe, the power reducer comprising: a current reduction means for limiting the in-rush current to the incandescent globe at turn-on of the incandescent globe and to provide substantially no limitation to the current thereafter; and, a circuit connection means for connecting the current reduction means into circuit with the incandescent globe; whereby, in use, current reduction means increases the operating life of the globe by reducing transient power surges in the incandescent globe at turn-on. In accordance with a further aspect of the present invention there is provided an incandescent globe having a power reducer as defined hereinabove.

The circuit connection means is, in one form an adaptor capable of physical coupling into an electrical light socket. In another form the circuit connection is a set of terminals for electrical connection to the electrical light socket. In one embodiment the voltage and current reduction means are installed between the globe and a socket for carrying the globe. In this case the voltage reduction means fits into the socket in the same manner as the globe and simultaneously provides a like receptacle for the globe (for either bayonet type or Edison screw type globes). Alternatively, the voltage and current reduction means could be located between an electrical terminal of the socket and an electrical terminal of the globe (especially for Edison screw type globes). In a still further embodiment the voltage and current reduction means are installed into the globe.

BRIEF DESCRIPTION OF THE DRAWINGS An exemplary embodiment of the present invention will now be described with particular reference to the accompanying drawings, in which:-

Figure 1 is a side view of a power reducer for a bayonet type globe, shown coupling the globe to an electrical light socket; Figure 2 is an exploded view of the power reducer, the globe and the socket shown in Figure 1; and,

Figures 3 to 5 are circuit diagrams of three alternative reducer circuits for the power reducer of Figures 1 and 2. DESCRIPTION OF THE PREFERRED EMBODIMENT

In Figures 1 and 2 there is shown a power reducer 10 comprising an adaptor 11 and a reducer circuit 12 for coupling between an incandescent globe 13 and a socket 14.

The adaptor 11 has a sleeve 16 at one end and a base 18 at its other end. The sleeve 16 has an internal dimension designed to receive a neck 20 of the globe 13. The sleeve 16 has two slots 22 terminating at locking ends 24 for receiving bayonet lugs 26 of the globe 13. The slots 22 and locking ends 24 are substantially "boot" shaped. The base 18 is attached to the sleeve 16 and substantially coaxial therewith. The base 18 has two bayonet lugs 28 substantially the same as the bayonet lugs 26 of the globe 13. The base 18 also has two terminals 30 located at an end 32 opposite from a top 34 of the sleeve 16. The external circumferential dimension of the base 18 is substantially the same as the external circumferential dimension of the neck 20 of the globe 13. The base 18 also has two posts 34 disposed upwardly into the confines of the sleeve 16 for bearing against two terminals 36 of the globe 13. The terminals 30 of the adaptor 11 are substantially the same in shape and disposition as the terminals 36 of the globe 13. By the nature of its design the base 18 is able to locate into the socket 14 through its top 38 by engagement of the bayonet lugs 28 into slots 40 and to locking ends 42 of the socket 14. The socket 14 has posts 44 similar to the posts 34 for bearing against the terminals 30. It can be seen that the sleeve 16 of the adaptor

11 is substantially the same as the socket 14 proximate its top 38, and the base 18 of the adaptor 11 is substantially the same as the neck 20 of the globe 13. Hence, the adaptor 11 acts as a male portion for the socket 14 and a female portion for the neck 20 of the globe 13. Consequently, the adaptor 11 can couple the globe 13 into the socket 14 as shown in Figure 1.

The reducer circuit 12, as shown in Figure 3, has a voltage reduction means in the form of a metal oxide varistor (MOV) 112 and a current reduction means in the form of three thermistors 114, 116 and 118.

The MOV 112 is connected in parallel with a mains input at terminals 120 and 122. The MOV 112 serves to shunt power, in excess of a predetermined voltage, between the terminals 120 and 122 so as to limit the voltage which passes through to the incandescent globe 13.

The thermistors 114 and 116 are connected in series with globe 13. The thermistors 114 and 116 are negative temperature dependent thermistors which commence conducting at high resistance and reduce their resistance as their temperature increases to operating temperature. The thermistors 114 and 116 are arranged in series with the incandescent globe 13. Accordingly, when power is first applied to the incandescent globe the thermistors 114 and 116 have a relatively high resistance and accordingly the current drawn through them is relatively low. With increased time the temperature of the thermistors 114 and 116 increases, the resistance of the thermistors 114 and 116 reduces and hence the current increases towards a maximum. Thus, the in-rush current to the incandescent globe 13 is reduced. The thermistor 118 is a positive temperature dependent thermistor and is connected in parallel with the incandescent globe 13. Accordingly, the thermistor 118 has a relatively low resistance as current commences to flow through it but increases in resistance as its temperature increases. Hence, when power is initially supplied to the incandescent globe 13 the thermistor 118 shunts a significant proportion of the current away from the incandescent globe 13 and back to the mains terminals 120 and 122 via the thermistors 114 and 116. Hence, the thermistors 114, 116 and 118 have the effect of reducing the initial start-up (or in-rush) current received by the incandescent globe 13.

Two alternative forms of the reducer circuit 130 and 140 are shown in Figures 4 and 5. The reducer circuits 130 and 140 are substantially the same as the reducer circuit 12 and like numerals denote like parts.

The reducer circuit 130 is devoid of the MOV 112 but has a MOV 150 in parallel with the thermistor 118.

The reducer circuit 140 has the MOV 112 and also has a second MOV 160 and a negative temperature dependent thermistor 162 both in parallel with the. globe 13.

The arrangement of the MOVs and thermistors used depends on the values of those components used.

In use, the power reducer 10 is coupled to the globe 13 by inserting the neck 20 of the globe 13 into the sleeve 16 with the bayonet lugs 26 projecting downwardly through the slots 22 and into the locking ends 24. Simultaneously, the terminals 36 bear against the posts 34. Consequently the terminals 30 of the power reducer 10 are in electrical contact with the terminals 36 of the globe 13 and with the reducer circuit 12 connected therebetween. The base 18 of the power reducer 10 is then inserted into the socket 14 with the bayonet lugs 28 projecting downwardly through the slots 40 and into the locking ends 42. Simultaneously, the terminals 30 bear against the posts 44. Consequently, the posts 44 are in electrical contact with the terminals 36 with the reducer circuit 12 in connection therebetween.

When electrical power is applied to the terminals 120 and 122 voltages in excess of a predetermined voltage, such as, for example 245 volts, are shunted by the MOV 112 so as to protect the incandescent globe 13 from excessive voltages. The thermistors 114 and 116 cooperate to reduce the in-rush current flowing into the incandescent globe 13 at switch on due to their relatively large resistance as the current commences to flow through them. With continuing flow of current the resistance of the thermistors 114 and 116 increases thereby allowing an increase in the current towards a maximum. Simultaneously, the thermistor 118 commencing at a relatively low resistance at switch on and increases to a relatively high resistance. Thereby, as current initially flows the thermistor 188 shunts current away from the incandescent globe 13. Therefore, the thermistors 114, 116 and 118 cooperate to reduce the in-rush current to the incandescent globe 13.

The power reducer 10 of the present invention has the advantage that it shunts excessive voltages away from the incandescent globe 13 and reduces the in-rush current to the incandescent globe 13. Accordingly, the operational life of the incandescent globe 13 is extended by isolating it from excessive voltages (including voltage spikes) and by reducing the current which it draws at switch on. Also, the globe 13 is protected from excessive mains voltage. Further, the thermistors 114 and 116 have the added effect of derating the globe 13 by always slightly reducing the voltage across the globe 13 by 10 to 20 volts.

Also, the power reducer 10 can be installed easily between a globe 13 and a socket 14 and removed for servicing or replacement of the globe 13 as desired. It is envisaged that the power reducer 10 could be colour coded so as to indicate its intention for use with globes of predetermined power output. For example, a red colour voltage reducer 10 may be used in respect of 100 watt globes and a yellow coloured power reducer 10 used in relation to 75 watt globes.

Modifications and variations such as would be apparent to a skilled addressee are considered within the scope of the present invention. For example, the power reducer 10 could be modified so that the base 18 has a circumferential thread replacing the bayonet lugs 28, the threaded base being capable of threaded location into an internally threaded socket 14 and the sleeve 16 being internally threaded for threaded engagement with an external thread of the neck 20 of the globe 13 (in the case of Edison screw type globes). Since Edison screw type globes have only a single terminal the power reducer 10 may be shaped to fit entirely within the socket 14 and the neck 20 of the globe 13 threading into the socket 14 and down onto the power reducer. Further, only one of the thermistors 114, 116 and 118 need be used to reduce the in-rush current in the incandescent globe 13. Still further, other forms of devices capable of reducing voltage and/or current could be used in place of the MOV 112 and the thermistors 114, 116 and 118, for example a choke. Still further, the power reducer 10 could be coupled to the electrical light socket electrically, rather than physically. For example, the power reducer 10, without the adaptor 11, could be wired into a back of the electrical light socket.

Claims

1. A power reducer for an incandescent globe, the power reducer comprising: a voltage reduction means for dissipating electrical energy at turn-on of the incandescent globe and to dissipate substantially no electrical energy thereafter; and, a circuit connection means for connecting the voltage reduction means into circuit with the incandescent globe; whereby, in use, the voltage reduction means increases the operating life of the globe by reducing transient power surges in the incandescent globe at turn-on.

2. A power reducer according to claim 1, in which the current reduction means is an electronic device connected in series with the incandescent globe, the electronic device having a relatively large impedance when electrical power is applied to it and which impedance reduces to a minimum with continued application of the electrical power.

3. A power reducer according to claim 2, in which the electronic device is a negative temperature coefficient thermistor.

4. A power reducer according to claim 1, in which the current reduction means is an electronic device connected in parallel with the incandescent globe, the electronic device having a relatively small impedance when electrical power is applied to it and which impedance increases to a maximum with continued application of electrical power.

5. A power reducer according to claim 4, in which the electronic device is a positive temperature coefficient thermistor.

6. A power reducer according to claim 1, in which the current reduction means is a network comprising the current reduction means referred to in claims 2 and 4.

7. A power reducer according to claim 1, in which the circuit connection means is an adaptor capable of physical coupling into an electrical light socket and capable of receiving the incandescent globe.

8. A power reducer according to claim 1, in which the circuit connection means is a set of electrical terminals for connection to an electrical light socket into which the incandescent globe can be inserted.

9. A power reducer for an incandescent globe, the power reducer comprising: a current reduction means for limiting the in-rush current to the incandescent globe at turn-on of the incandescent globe and to provide substantially no limitation to the current thereafter; and, a circuit connection means for connecting the current reduction means into circuit with the incandescent globe; whereby, in use, current reduction means increases the operating life of the globe by reducing transient power surges in the incandescent globe at turn-on.

10. A power reducer according to claim 9, in which the voltage reduction means is an electronic device connected in series with the incandescent globe, the electronic device being connected in series with the incandescent globe and being capable of creating a potential difference across it.

11. A power reducer for an incandescent globe, the power reducer being a combination of the current reduction means defined in claims 1 to 8 and the voltage reduction means defined in claims 9 and 10.