Field of the Invention

This invention relates to lighting apparatus, especially airfield lighting apparatus. The term "airfield" as used herein is intended to embrace helipads and other aircraft landing sites.

Summary of the Invention

A first aspect of the invention provides a lighting apparatus, especially an airfield lighting apparatus, comprising a marshalling wand having an elongated light source, a handle, and an electrical power source for the light source, wherein the apparatus further includes means for adjusting the luminosity, or output power, of the light source.

In the preferred embodiment, the apparatus further includes a support unit on which the wand is removably mountable such that the light source extends, in use, upwardly from the support unit, and a landing-light lens for removably surrounding the light source at least when the wand is mounted on the support unit.

An advantage of the invention is that the light source of the marshalling wand is also used as the luminaire of an airfield landing light, thus providing a dual-purpose device and saving on component cost. >

Preferably the wand' s electrical power source "is rechargeable, and the support unit has an electrical connector for engagement with a complementary electrical

COMFIRMATIOiMCOPY connector on the wand for re-charging the power source from a power supply external to the wand.

Preferably, too, at least one of the wand and support unit includes a radio receiver for receiving signals controlling the power output of the light source.

In the preferred embodiment, the elongated light source comprises a discharge lamp, for example a fluorescent tube, and the landing-light lens comprises a Fresnel lens. This combination has two main advantages. First, the relative positioning of the tube with respect to the lens is not critical; with a conventional tungsten filament bulb, the positioning the bulb must be precise - it must be exactly in the centre of the lens unit. Second, the projected light has a wider span and this allows the light cast by the airfield light to be visible to aircraft on a wider range of approach angles. This is particularly surprising since Fresnel lenses are designed specifically for a centrally located "point" light source and are not contemplated for use with an elongate light source.

A second aspect of the invention provides a marshalling wand having an elongated light source, a handle, and an electrical power source for the light source, wherein the apparatus further includes means for adjusting the luminosity of the light source.

A third aspect of the invention provides an airfield lighting apparatus comprising: (a) a marshalling wand including a handle supporting an elongated light source and an electrical power source for the light source, (b) a support unit on which the wand can be removably mounted such that the light source extends visibly upwardly from the support unit, and (c) a landing-light lens for removably surrounding the light source at least when the wand is mounted on the support unit.

Other preferred features are recited in the dependent claims.

Further advantageous aspects of the invention will become apparent to those ordinarily skilled in the art upon review of the following description of a preferred embodiment and with reference to the accompanying drawings.

Brief Description of the Drawings

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic sectional view of an aircraft marshalling wand forming one component of a first embodiment of an apparatus embodying the invention;

Figure 2 is a schematic sectional view of a portable airfield landing light according to the first embodiment of the invention which incorporates the marshalling wand of Fig. 1; and

Figure 3 is a schematic sectional view of a' portable "airfield landing light according to a second embodiment of the invention. Detailed Description of the Drawings

Referring first to Figure 1, there is shown, generally indicate as 5 a preferred embodiment of an aircraft marshalling wand. The preferred wand 5 comprises an elongate light source. The light source preferably comprises a luminescent or discharge light source, for example in the form of a cold cathode lamp, e.g. a fluorescent lamp. Advantageously, the light source takes the form of an elongate tube. In the preferred embodiment, the light source comprises a cold cathode tube or fluorescent tube 10. In the present example, a 13 Watt fluorescent tube 10 is used. The tube 10 is connectable to, and extends from, a housing 12. The housing 12 contains a power supply preferably in the form of a rechargeable battery, particularly lithium-ion phosphate battery 14. The preferred battery 14 is a 12 volt battery with a capacity of at least 1 Ah. The housing 12 also contains a control unit or circuit 16.

A handle 18, conveniently comprising an elongated bar or other member, extends from the opposite side of housing 12 from the tube 10 and preferably extends in a direction substantially opposite to the direction in which the tube 10 extends. The handle 18 may be substantially coaxial with the elongated fluorescent tube 10. The battery 14 can be recharged from the mains, or other supply, via a removable power supply lead 22 which, conveniently, is ■connectable to the handle 18.

A removable translucent sleeve 20 surrounds the tube 10 to form a filter. A number of such filters 20 may be provided in different colours, such as red, blue, aviation yellow, IR filtering or NVG filtering, the appropriate filter being fitted according to circumstances.

The control unit or circuit 16, which typically includes a suitably programmed microprocessor or microcontroller, for example a PIC18F1220 microprocessor, may perform one or more of several functions. First, it may provide PCM (protection circuit module) circuitry for the rechargeable battery 14. As is well known, PCM circuitry monitors the voltages on the individual cells of the battery during charging and discharging and isolates individual cells according to whether their voltages exceed or fall below predetermined thresholds.

Second, the control circuit 16 provides power to the fluorescent tube 10. To this end the control circuit 16 includes a DC-AC inverter which converts the DC voltage of the battery 14 to an AC supply for energising the fluorescent tube 10 via a suitable electrical connector (not shown) between the tube 10 and the control circuit 16. Such inverters are well-known.

Third, it provides means for adjusting the luminosity of the light source. Preferably, this is achieved by varying the power output of the tube 10 by switching the inverter on and off in accordance with a variable duty cycle using pulse width modulation (PWM) . When the inverter is switched on, it supplies AC power to the tube 10, and when it is switched off it does not supply power to the tube 10. The rate at which the tube 10 is switched on and off is sufficiently fast to give the impression of substantially constant light to a human eye. In the preferred embodiment, the duty cycle is controlled, or adjusted, dynamically to maintain a specified inverter current. Conveniently, this is achieved by monitoring the current at, say, the input of the inverter and adjusting the duty cycle to maintain the current at a pre-determined level. This has the effect of stabilising the light output, or luminosity, of the tube 10 at one of several predefined power levels. Hence, by adjusting the power output (and therefore the intensity or luminosity of the radiated light) , the same apparatus can be used for various applications, for example as marshalling wand (reguires relatively lower power output) or airfield landing light (requires higher power output) . Moreover, the light intensity can be adjusted to meet different environmental conditions. It is noted that the luminosity of the light source may, in alternative embodiments, be adjusted by any conventional means.

Fourth, in cases where the fluorescent tube 10 includes electrode heaters (not shown) , the control circuit 16 may be arranged to energise, or activate (i.e. preheat) the heaters before the lamp 10 itself is struck, or lit, in order to improve striking efficiency and to increase the longevity of the lamp 10. This may be achieved by __ supplying electrical power, e.g. from the battery 14, to the heaters before the inverter is operated to strike the tube 10. Typically, the heaters need to be energised only for half a second or so before the tube 10 is energised, after which the heaters may be de-energised until they are next required.

Fifth, the control circuit 16 may facilitate the lamp 10 being flashed on and off in applications that require it (for example a "wigwag" lamp) . Conveniently, this involves setting the duty cycle so that the tube 10 is switched on and off at a rate that is detectable to a human eye. Depending on the rate at which the tube 10 is switched on and off by the duty cycle, it may or may not be necessary to energise the heaters (when present) before the tube 10 is switched on each time, and so judicious combination of heater preheat and PWM duty cycle control is required.

Sixth, the control circuit 16 supports an optional light sensor to effect automatic activation of the lamp at dusk and de-activation at dawn in applications that require it.

The handle 18 may include a push button 24, or other switch, the control circuit 16 being responsive to activation of the button 24 to toggle the fluorescent tube 10 on and off by consecutive pushes of the button 24. When used as a marshalling wand, the tube 10 is typically operated at 2.5 or 5 Watts. A separate control device (not shown) may be provided on the wand 5 for selecting the desired power output. Alternatively, the power output level can be set by respective sequences of activations of the on the on/off push button 24 that are recognised by the control circuitry 16 which causes the duty cycle to be adjusted accordingly. The duty cycle, and therefore the power output of the tube 10, may alternatively, or in addition, be adjusted by a control voltage, or signal, as is described below with reference to Figures 2 and 3. An LED 26, or other lamp, indicates the current state of the wand: e.g. green = charging, red = low battery, etc. Turning now to Figure 2, a preferred embodiment of a portable airfield landing light is shown, generally indicated as 15. The airfield landing light 15 incorporates the marshalling wand 5 of Figure 1. The landing light 15 includes a base or support unit which in the present example includes a housing 30 having a top opening 32. The marshalling wand 5 can be removably mounted on the support unit. In the present example, this is achieved by inserting the handle 18 through the opening 32 until the wand housing 12 comes to rest snugly within the opening 32 on supports (not shown) within the housing 30. In this position, the fluorescent tube 10 extends freely and visibly upwardly (in use) from the housing 30. When used in the airfield landing light, the wand filter 20 is removed and a removable lens 34, especially a landing light lens, is mounted on the housing 30 around the opening 32, surrounding and covering the fluorescent tube 10. Preferably, the lens 34 is a Fresnel, or fresnelled, lens, typically a multi- sided (usually four-sided) Fresnel lens. Each side and the top of the Fresnel lens can have the same or a different colour from the others, such as red, blue, aviation yellow, IR filtering or NVG filtering. Instead of being mounted on the housing 30, the lens 34 could be removably mounted on the periphery of the wand housing 12, or mounted on the wand 5 or support unit in any other convenient manner.

The support unit housing 30 preferably contains a rechargeable battery 36, advantageously a lithium-ion ■phosphate battery. In the present example, the battery 36 is a 12V battery with a capacity of 12 Ah. ' The support unit further includes a control circuit 38 and, preferably, a radio receiver 40 with associated antenna 42. The control circuit 38 is associated with an electrical connector, conveniently a three-pin connector 44, which is connectable to the wand handle 18 in place of the power lead 22 in order to supply electrical power to the tube 10. The battery 36 is rechargeable from the mains, or other power supply, using a power lead similar to the lead 22, or can be recharged by a photovoltaic panel (not shown) . In use as part of the airfield landing light 15, the fluorescent tube 10 may draw power from both the battery 14 and the battery 36, the latter maintaining the charge on the former.

The control circuit 38, which again may be based around a PIC18F1220 microprocessor, may perform several functions. ■ First, it may provide PCM charging circuitry for the rechargeable battery 36. Second, it controls the power output of the fluorescent tube 10. In the preferred embodiment, the required power output is determined in accordance with radio signals received by the radio receiver 40 from a remote control unit or fr.om an approaching aircraft. Third, it switches the tube 10 on and off at dusk and' dawn respectively according to the output of an optional dawn/dusk optical sensor 46..

The control circuit 38 varies the power output of the tube 10 by sending control signals via the connector 44 ■ to the- control circuit 16 to vary the duty cycle .under which the inverter is operated using pulse width ■ modulation. It.will be recognised that only two wires are necessary for battery charging and power supply 'functions, so that the third wire of the three- pin connection 44 can be used for carrying these control signals. Typically the fluorescent tube 10 would be run at 7.5 or 10 Watts when used as an airfield landing light, bur the control system 38, 16 allows the tube 10 to be run at various levels of power output providing corresponding levels of brightness.

A second embodiment of an airfield lighting apparatus is shown in Figure, generally indicated as 115. In the Figure 3, the same reference numerals have been used for components the same or equivalent to those in Figures 1 and 2, and will not be described again. In this embodiment, the support unit is in the form of a housing or sleeve 50 which can be set into the ground 52 as shown, and the marshalling wand 5 is mounted on the support unit by sliding its handle 18 into the housing 50 so that the tube 10 extends freely and visibly upwards. In this case the radio receiver 40 (not shown in Fig. 3) is incorporated in the wand housing 12, and the antenna 42 is fitted externally to the wand housing 12. Thus there is no need to send control signals from the support unit to the wand 5 to vary the power output of the fluorescent tube, as in the previous embodiment, since such signals may be sent directly to the control circuitry 16 in the wand 5.

The apparatus 115 further includes a lens, typically a Fresnel landing light lens 34, removably mounted on the wand housing 12. As before, the lens is preferably multi-sided, each side and the top of the lens having the same or a different colour from the others, such as red, blue, aviation yellow, IR filtering or NVG filtering. Also, optional interchangeable translucent sleeves 20 surrounding the fluorescent tube 10 can provide different colour filters. The base of the sleeve 50 preferably has an internal electrical connector 54 which is connectable to the handle 18 when the latter is fully inserted in the sleeve 50. The individual terminals (not shown) of the connector 54 are connected through the wall of the sleeve 50 to respective metal contacts 56 on the external surface of the sleeve 50. This allows the wand battery 14 to be re-charged via the metal contacts 56 from a solar panel or auxiliary power supply (not shown) while remaining in the ground. Alternatively the sleeve 50 can be removed from the ground for re-charging the battery 14, or further such sleeves can be provided on a trailer or the like into which the wands can be transferred for re-charging from, say, a vehicle battery.

Although the foregoing embodiments have used the same fluorescent tube 10 for both the marshalling and landing light applications, it is possible to use different light sources, and in particular different fluorescent tubes, to suit different applications. For example, it would be possible to use a relatively short 13W D/E tube for the landing light application, and a longer HW S/E tube for the marshalling wand.

I" The wand 5, when used as a standalone emergency light with or without the fresnelled lens, is relatively ,low weight (typically about 1.5Kg each) and requires relatively low charge currents (typically about 0 .75A per wand) . This facilitates, carrying up to around 12 wands (which is currently the maximum requirement for ■helipads) in a single case (not shown) , typically a storm proof, sealed case. Moreover, the -wands may be charged using a conventional cigar/cigarette lighter socket in a vehicle, e.g. car or SUV. In alternative embodiments, the light source may be provided by alternative means, for example an array of LEDs (light emitting diodes) . However, discharge light sources, especially cold cathode or fluorescent lamps, are preferred as they provide a relatively high light intensity while consuming relatively little power. When supplied by a suitable rechargeable battery, especially a battery based on Li-ion phosphate technology, the apparatus exhibits a relatively long life between charges and has relatively low charging requirements (including charge time and current) . Moreover, it is found that the diffuse nature of the fluorescent type light source is, surprisingly, well suited for use with a landing light lens, especially a Fresnel lens.

Apparatus embodying the invention are not limited to use as airfield lighting and may be used in other applications, e.g. road traffic control.

The invention is not limited to the embodiments described herein which may be modified or varied without departing from the scope of the invention.