GB2344230A

GB2344230A - An energy saving LED torch

Info

Publication number: GB2344230A
Application number: GB9926169A
Authority: GB
Inventors: Nicholas Anwyl-Davies
Original assignee: ANWYL DAVIES NICHOLAS
Current assignee: ANWYL DAVIES NICHOLAS
Priority date: 1998-11-04
Filing date: 1999-11-04
Publication date: 2000-05-31
Also published as: GB9926169D0

Abstract

An electric torch (Figures 1 to 7) with a light emitting diode (LED) 23 as a light source has two modes of operation, one where the LED is powered continuously and the other where power to the LED is pulsed. The pulsed output is controlled by an integrated circuit 29 including a chopper circuit and constitutes a battery saving mode. A slider (14, figs 1, 4, 6 and 7) is provided to activate switches 18, 19 so that the user can select the desired mode of operation. The user may also vary the frequency of the flashing in the pulsed mode of operation. The light source can also be used in table lamps or signs where the battery powered pulsed operation will typically be used as a back-up during mains power failure.

Description

AN ELECTRIC LIGHT DEVICE This invention relates to an electric light device such as, a bedside or table lamp or a sign or an electric torch which is sometimes known as a flashlight.

A simple electric torch comprises a hollow casing which is open at one end and which accommodates one or more replaceable batteries and a spring arrangement which reacts against a closed base of the casing and urges the one or more batteries towards the open end, a metal bulb holder into which a replaceable electric filament bulb is fitted so that a good electrical connection is made between the bulb and the holder, and which forms or supports an annular silvered reflector which forms a flared silvered reflective surface around the bulb so that light emitted sideways by the bulb is reflected axially, an annular cap which is realisably fitted to the open end of the casing and which thereby traps the bulb holder in position within the open end of the casing in good electrical contact with one end terminal of the one or more batteries which are urged against it by the spring arrangement, and a switch mechanism which is mounted on the casing and which co-acts with the bulb holder and the one or more batteries whereby to make or break an electrical circuit whereby the bulb is energised by the batteries when the circuit is made and a beam of light is formed by light emitted axially by the bulb and by light reflected axially by the silvered reflector, the annular end cap forming an aperture through which the beam of light is directed. The switch mechanism may be operable by sliding a slider or by depressing one or more push buttons in order to switch the torch on or off.

Usefulness of such a torch or flashlight is dependent upon the state of the batteries and the bulb which have limited lives and which must be replaced from time to time.

One object of this invention is to provide an electric torch or flashlight which has an improved light source and means for economising battery usage.

Broadly, in one aspect, the invention comprises an electric torch or flashlight wherein the light source is a light emitting diode, especially, although not exclusively, a white light emitting diode. Preferably means are provided whereby the torch or flashlight can be operated in a selected battery energy saving mode as an alternative to a full power continuous beam output mode.

The idea of using a light emitting diode as a light source which has two modes of operation, one being a continuous bright beam output while the other is a battery powered pulsed output can be applied to other forms of electric light device such as a bedside or table lamp or a sign such as an exit sign. In such an application the electric light device can be arranged so that, normally the light emitting diode would be powered by a mains supply or by some other suitable electric power supply external to the electric light device for the continuous bright beam output mode of operation, the battery power source of the device being inoperative during this continuous bright beam output mode of operation. The electric light device would be arranged so that, in the event of a failure in the means or other external power supply, the light emitting diode could be operated in an energy saving pulsed mode by battery power under control of an integrated circuit including a chopping circuit substantially as has been described above for the selected battery saving mode of the torch or flashlight. The electric light device could be arranged to be switched automatically to the back up battery powered energy saving mode in the event of a failure in the mains or other external power supply.

Indeed the light emitting device itself could be a backup light source which would only be energised in the event of failure of the mains or other external light source which had been used to energise another higher emitting device which could be a conventional light blub Hence another object of this invention is to provide an electric light device which is designed for norma : operation powered by a mains supply or other suitablz electric power supply external to the device but whicl has a back-up battery powered mode of operation which i ! economic in the use of battery power.

According to a preferred embodiment of thi : invention there is provided an electric torch oz flashlight having a casing which forms an aperture at it : front, an electric power source holder within the casinc for receiving and holding a source of electric power anc having terminals for contact with terminals of < source of electric power held by the electric powez source holder, an electric light source, circuit means for electrically connecting the light source to the terminals of the electric power source holder whereby the light source is energised when said source of electric power is fitted into the electric power source holder anc a beam of light emitted by the light source is directec through the aperture, and manually operable switch means mounted on the casing and operable to make and break the electrical connection between the light source and the terminals of the electric power source holder, whereii the electric light source is a light emitting diode, the circuit means includes means operable to emit a pulsec output of electric power pulses and said switch means are operable to select one of the following operational modes, namely: i) an off mode in which the connection of the light emitting diode to the terminals of the electric power source holder is broken; ii) a flashing mode in which the light emittinc diode is connected to the terminals of the electric powez source holder through the means operable to emit a pulsec output of electric power pulses, and iii) a continuous beam mode in which the light emitting diode is connected directly to the terminals oS the electric power source holder, and wherein a reflector body part of solic transparent material is mounted upon the body of the light emitting diode so as to receive rays which radiate from the light emitting diode and pass through the bod3 of the diode at non-useful light giving angles to the optical axis of the light emitting diode, the reflectoj body part causing the light rays to be substantially totally internally reflected by it to form useful light directed through the aperture.

A focusing lens may be mounted within the casing ir the optical path of light from the light emitting diode and the reflector body part through the aperture.

The means operable to emit a pulsed output of electric power pulses and the switch means may be arranged to enable selection from a range of different frequencies of flashing of the light emitting diode in the flashing mode up to and including a high frequency at which the periodic interruptions in the emitted light beam cannot be detected by the human eye.

Conveniently the switch means which is operable to select different frequencies of flashing of the light emitting diode is a snap action push button switch whereas the switch means which is operable to switch the torch on and off for the continuous beam mode comprises a slider switch which may carry the push button actuating element of the push button switch.

One form of electric torch or flashlight in which this invention embodied is described now by way of example with reference to the accompanying drawings, of which: Figure 1 is a side elevation of the torch; Figure 2 is a front elevation of Figure 1 ; Figure 3 is a plan view of Figure 1 ; Figure 4 is a view similar to Figure 3 with part of the casing removed to reveal components inside the casing; Figure 5 is a schematic cross-section of the torch shown in Figures 1 to 4 showing the relative location of the batteries, the printed circuit board, the light emitting diode and the reflector body part; Figure 6 is a section on the line VI-VI in Figure 3 showing the switch means set for selection of a flashing mode ; Figure 7 is a view similar to Figure 6 showing the switch means set for the continuous beam mode; and Figure 8 is a schematic electrical circuit diagram of the solid state circuitry of the torch shown in Figures 1 to 7.

Figures 1 to 7 show that the torch comprises hollow casing 10 which is generally rectangular in both longitudinal and transverse planes. The casing 10 has rounded corners and is closed at one end 11 which is the rear end. It is open at the other or front end 12. A rectangular slot 13 is formed at the center of the top so as to extend in the fore and aft direction. A slider 14 is mounted for sliding movement in the slot 13 between one operating position in which the slider 14 abuts the rear of the slot 13 and another operating position in which the slider 14 abuts the front of the slot 13. The slider 14 carries a snap action push button actuator 15 which is operable to exert downwards thrust when the button is depressed.

Support structure 16 is fitted to the top of the casing 10 at the front of the slot 13. An L-shaped tray 17 is arranged with its shorter side depending from the support structure 16 and its longer side extending below the slot 13 within the casing 10. The tray 17 carries two switches 18 and 19. Each switch 18, 19 has an upstanding actuating button and the switch is arranged so that its state is changed by depression of its button.

The switches 18 and 19 are located on the tray 17 one behind the other so that the button of the rear switch 18 is below the push button actuator 15 when the slider 14 is in its rear operating position whereas the button of the forward switch 19 is depressed by structure of the slider 14 when the latter is moved to the forward end of the slot 13.

Three batteries 21 are located side by side on the bottom of the casing 10 below the tray 17. They are connected in series and their rear ends are adjacent to the rear end 11 of casing 10.

A printed circuit board 22 is supported within the casing 10 so as to extend transversely therein in front of the batteries 21 and the tray 17 against which its upper end rests. A white light emitting diode 23 is mounted on the forward face of the printed circuit board 22 substantially centrally within the casing 10 and substantially axially in line with the underside of the tray 17. The white light emitting diode 23 faces forwardly. It is surrounded by an annular reflector body 24 of solid transparent material such as polymethymethacrylate or any other material used for making the bodies of known light emitting diodes. In addition to being fitted circumferently around the white light emitting diode 23, the transparent annular reflector body 24 is bonded to the white light emitting diode 23 by an ultra-violet glue as is described in GB-A2,282,700. The central aperture of the body 24 is cylindrical and receives the white light emitting diode 23. The radially outer surface of the annular reflector body 24, between the forward and rear ends of the body 24 is part parabolic with the focus of the parabola being at or near the white light source of the light emitting diode 23. The front surface of the transparent annular reflector body 24 is concave so that the body 24 has an annular leading edge forward of the white light emitting diode 23. Although the reflector body part 24 is designed to cause light rays that enter it from the white light emitting diode 23 to be totally internally reflected, a reflective coating is provided on its back so as to reflect any light which is not totally internally reflected due to manufacturing tolerances.

A focusing lens 25 is mounted centrally in a transparent pane 26 which is fitted into the open end 12 of the casing 10 in front of the white light emitting diode 23 and the transparent annular reflector body 24.

Figure 8 shows the electrical connections of the solid state components of the torch or flashlight. Apart from the switches 18 and 19, the battery 21 and the white light emitting diode 23, the circuit is formed on the printed circuit board 22.

Figure 8 shows that the white light emitting diode 23 is connected between the negative terminal of the batteries 21 which are connected in series and the collector of a transistor 27. The positive terminal of the batteries 21 is connected in parallel to the emitter of the transistor 27 and, through a resistance 28 and the slider operable switch 19, to the connection between the white light emitting diode 23 and the collector of the transistor 27. The base of the transistor 27 is connected to an output port of an integrated circuit 29 which includes a chopping circuit and which has a toggle on/off setting actuated by the push button operable switch 18, the integrated circuit 29 being powered by the batteries 21 that are connected across it.

The torch or flashlight is switched off when the slider 14 is at its rear location and the integrated circuit 29 is in its off setting. To operate the torch or flashlight in its flashing mode, the push button actuator 15 is depressed when the slider is in its rear location, so that the downward thrust exerted by the push button actuator 15 actuates the switch 18 below it. That actuation of the switch 18 triggers the integrated circuit 29 to emit a pulsed square wave output of a certain frequency that is transmitted via the transistor 27 to actuate the white light emitting diode 24 in a flashing mode of that frequency. A second depression of the push button actuator 15 will actuate the switch 18 again and thereby effect a change in the frequency of the pulsed square wave output of the integrated circuit 29 to a higher frequency with a consequent increase in the frequency of the flashing output of the white light emitting diode 24. Likewise a third depression of the push button actuator 15 will actuate the switch 18 for a third time which in turn will effect a change in the frequency of the pulsed square wave output of the integrated circuit 29 so that the consequent white light output from the white light emitting diode will be at a yet higher frequency which will appear to human eye to be a continuous beam since it is a frequency of which the periodic interruptions in the emitted white light beam cannot be detected by the human eye.

In order to switch the torch or flashlight to its continuous bright white light beam output mode, the slider 14 is slid forwards to its other operatinc position at the front of the slot 13. In that slidinc movement, the underside of the leading edge of the slidex 15 depresses the actuating plunger of the forward switcl 19 which results in the full voltage of the batteries being connected across the white light emitting diode 2 and the integrated circuit 29 being bypassed. The white light output in this mode is higher because ths integrated circuit 29 has been bypassed and the full voltage of the batteries 21 has been applied to the white light emitting diode 23 continuously whereas the voltage applied to the white light emitting diode 23 in thf flashing mode is somewhat less because it is a square wave output, that is to say a series of electric pulses which itself is pulsed as well.

Electric power sources other than dry cell batteries may be used. They may comprise a solar power source ox a mechanical mechanism which is operable to generatc electric power.

Claims

CLAIMS: 1. An electric light device such as an electric torch, a table lamp or an illuminated sign, wherein the light source is a light emitting diode and it is arranged to be operated in at least two different modes, one being an energy saving mode where the diode is energised in an interrupted mode and the other where the diode is operated continuously.
2. A device according to Claim 1 in which the device is arranged to be selectively powered by a mains supply and by a battery power source, and that when mains supply is selected the power source is operated continuously.
3. A device according to Claim 2 in which the battery power source is arranged as a back-up supply which only becomes operative in the event of failure of the mains supply.
4. An electric light device in the form of an electric torch or flashlight having a casing which forms an aperture at its front, an electric power source holder within the casing for receiving and holding a source of electric power and having terminals for contact with terminals of such a source of electric power held by the electric power source holder, an electric light source, circuit means for electrically connecting the light source to the terminals of the electric power source holder whereby the light source is energised when said source of electric power is fitted into the electric power source holder and a beam of light emitted by the light source is directed through the aperture, and manually operable switch means mounted on the casing and operable to make and break the electrical connection between the light source and the terminals of the electric power source holder, wherein the electric light source is a light emitting diode, the circuit means includes means operable to emit a pulsed output of electric power pulses and said switch means are operable to select one of the following operational modes, namely: i) an off mode in which the connection of the light emitting diode to the terminals of the electric power source holder is broken; ii) a flashing mode in which the light emitting diode is connected to the terminals of the electric power source holder through the means operable to emit a pulsed output of electric power pulses, and iii) a continuous beam mode in which the light emitting diode is connected directly to the terminals of the electric power source holder, and wherein a reflector body part of solid transparent material is mounted upon the body of the light emitting diode so as to receive rays which radiate from the light emitting diode and pass through the body of the diode at non-useful light giving angles to the optical axis of the light emitting diode, the reflector body part causing the light rays to be substantially totally internally reflected by it to form useful light directed through the aperture.
5. An electric light device according to Claim 4 wherein the means operable to emit a pulsed output of electric power pulses and the switch means may be arranged to enable selection from a range of different frequencies of flashing of the light emitting diode in the flashing mode up to and including a high frequency at which the periodic interruptions in the emitted light beam cannot be detected by the human eye.
6. An electric light device according to Claim 5 in which the switch means which is operable to select different frequencies of flashing of the light emitting diode is a snap action push button switch and the switch means which is operable to switch the torch on and off for the continuous beam mode comprises a slider switch which may carry the push button actuating element of the push button switch.
7. An electric light device substantially as herein described with reference to and as illustrated in Figures 1 to 8 of the accompanying drawings.