LIGHTING UNITS

Abstract: A lighting unit for an aircraft taxiway or runway comprises a base (1) adapted to be secured to the ground with its upper surface generally at ground level and a lighting module (2) releasably connected to the base unit. The lighting module includes an opening in its undersurface communicating with a cavity (9) for receiving and retaining a lamp (8) with its bulb uppermost and with its electrical contacts exposed through the module opening for connection to a source of electrical power via cabling. The lighting module also includes two upwardly and outwardly inclined light emitting passageways (12) in each of which is positioned one or more optical lenses (14, 15). Each light emitting passageway communicates at its lower end with a lamp retained in the module cavity and is formed such that the optical axis of light emitted through it is inclined at an angle relative to the horizontal greater than a desired angle of emission. The or each optical lens is arranged to redirect the emitted light so its outward path is at a desired angle.

Description: LIGHTING UNITS The present invention relates to lighting units. More especially, but not exclusively, the invention relates to lighting units for use at airports which provide illumination at ground level on or adjacent to runways and taxiways for the benefit of aircraft and other vehicles. Many different constructions of such lighting units are known including some which have a lamp and associated lens unit contained in a casing which is separable from a base set in the ground to facilitate servicing and replacement of the lamp and lens assembly. A lighting unit of this type, which is inexpensive, reliable and readily serviceable, is disclosed in my co-pending UK Patent Application No: 2250577A. This unit is intended to be mounted at ground level and includes electrical contacts for connecting the lamp to a mains power source; the electrical contacts are positioned above ground level to avoid electrical faults occasioned by water entering the unit casing. The lamp is mounted in a generally horizontal attitude which renders speedy insertion and connection difficult to achieve. There has recently been a tendency towards minimising the extent to which lighting units project above ground level to reduce stresses on aircraft undercarriages and it is an object of the present invention to provide an improved lighting unit whose lamp and lens assembly is contained in a demountable module, the electrical contacts of which are located below ground level. According to the present invention, there is provided a lighting unit comprising a base adapted to be secured to the ground with its upper surface generally at ground level and a lighting module releasably connected to the base unit, the lighting module including an opening in its undersurface communicating with a cavity for receiving and retaining a lamp with its bulb uppermost and with its electrical contacts exposed through the module opening for connection to a source of electrical power via cabling, the lighting module also including an upwardly and outwardly inclined light emitting passageway in which is positioned one or more optical lenses, the light emitting passageway communicating at its lower end with a lamp retained in the module cavity and being formed such that the optical axis of light emitted through it is inclined at an angle relative to the horizontal greater than a desired angle of emission, the or each optical lens being arranged to redirect the emitted light so its outward path is at a desired angle. O 95/19912 3 In a preferred arrangement, two light emitting passageways are provided, each angularly disposed relative to the other to define a substantially vee-shaped arrangement. Advantageously, the upper surface of the module adjacent each light emitting opening of the passageway slopes upwardly to avoid obstruction of redirected light emitted from the module. Each light emitting passageway may include a planoconvex lens and a prism lens. The inner face of the prism lens can be dichroic coated, or an even thickness of the prism lens can be coloured, or a separate dichroic filter can be provided. In one embodiment, particularly for use on curved taxiway sections, the or each light emitting passageway may be tilted or "toed-in" at an appropriate angle to the vertical so that, in use of the unit, the or each light path is emitted at an angle to a tangent of the curved taxiway section. One end of the module is preferably located in a recess in the base to form a retaining ledge with the opposite end of the module held by a single fastening member, such as a bolt. The invention will now be described by way of example only with reference to the accompanying diagrammatic drawings, in which:- Figure 1 is a plan view of a lighting unit according to the invention; Figure 2 is a cross-section taken on line II-II in Figure 1; Figure 3 is a cross-section taken on line III-III in Figure 1; Figure 4 is a view from below of a feature of the unit illustrated in Figure 3; Figure 5 is a side view in section of a plug for use with a unit in accordance with the invention; Figures 6 and 7 are sectional side views of sockets for connecting to lighting units in accordance with the invention; and Figures 8 and 9 are respectively plan and side views of an alternative lighting unit in accordance with the invention. The lighting units illustrated in the drawings are intended particularly to be set into the surface of a runway or taxiway of an airport. The lighting unit illustrated in Figures 1 to 3 comprises a base 1 and a demountable lighting module 2. The base 1 comprises a metal casting having a peripheral lip 3 for resting in a preformed ground recess. The lip 3 has holes 4 to receive bolts (not shown) for securing the lighting unit in position. Extending downwardly from the undersurface of the module 2 is a cylindrical open ended collar 6 which receives a lamp holder 7 for retaining a lamp 8. The lamp is not illustrated in Figure 2. As will be seen from Figure 3 of the drawings, the lamp 8 is positioned generally vertically with its bulb uppermost and extending into a cavity 9 formed in the lower portion of the module. The lamp 8 is supported within the lamp holder 7 and has connecting pins 10 which are received in an electrical socket 11 connected to mains wiring. The lamp holder is introduced into the module through the collar 6 from below for ease of assembly. The module 2 includes two upwardly and outwardly inclined passageways 12 each of which defines a path for light emitted by the lamp 8. The lower ends of the passageways 12 communicate with the cavity 9. Each passageway 12 houses a planoconvex lens 14 and a prism lens 15 which is spaced from the lens 14 by a spacer ring. An even thickness of the prism lens 15 may be coloured or may be dichroic coated on its inner face. Alternatively, a separate dichroic filter can be placed between the lens 14 and the prism lens 15 and held in position by two spacer rings. One or more suitably shaped reflectors may be provided to re-direct light directed by the lamp onto wall surfaces of the cavity along the light emitting paths- of the passageway. The collar 6 provides a secure housing for the lamp 8 and lamp holder 7 and guards against damage caused when removing the lamp and lamp holder from the module. As shown, an "0" ring 16 is set in a groove formed in the outer circumference of the collar 6 to provide an effective seal between the lamp holder 7 and the collar interior and to retain the lamp holder 7 in its intended position within the collar 6. Means are preferably provided to ensure that the lamp is correctly aligned with respect to the passageways 14. As will be seen from Figure 4, radial grooves 17 are provided in the base of the collar 6 for this purpose which can be aligned with protrusions on the lamp holder itself. It will be noted that the base 1 of the lighting unit is secured at ground level GL with the upper surface of the module 2 slightly above ground level. Because the module is essentially mounted at ground level, the passageways 12 are mutually inclined to define a vee-shaped arrangement with each passageway set at an angle greater than the desired angle of emission of the light passing through that passageway. For example, the passageways may be positioned at typically between 35"and 45°to the horizontal and the required emission angle of the beam may be near horizontal, typically only 4.5° to 5.5°. Thus, each prism lens 15 is designed to redirect the emitted light so that it leaves the unit at the required angle. The module 2 is secured in position in the base 1 by locating one end of the module under a retaining ledge of the base and securing the other end of the module to the base 1 by a bolt 20 which passes down through the main body of the module and into a threaded bore of the base. The head of the bolt 20 may itself engage the adjoining surfaces of the module and base thereby doing away with the need for a ledge. 95/19912 7 If desired, a spring (not shown) may be provided to urge the module upwardly from the recess when the bolt 20 is released to assist in removing the module from the recess. Alternatively, an "E" clip may be positioned below the retaining lug so that as the bolt is released so the lug rises and can be removed readily to provide access to the module itself. The lamp can be quickly and easily changed by simply releasing the lamp holder 7 and withdrawing the lamp 8 from the cavity 9. A rubber or similar strip may be fixed around the top edge of the module aperture in base 1 so that when the module 2 and lamp holder 7 are inserted into the base 1 they are sealed around their periphery. Alternatively, the module may be a machined fit in the base with a clearance of, for example, 0.004". The contacting surfaces of the module and the base may be coated with a material which provides lubricity and efficient sealing between the surfaces. Also, the coating may provide efficient heat dissipation from the module to the base. The lamp holder is illustrated in greater detail in Figure 5. The holder contains all of the electrics required for operation of the light unit. The holder includes a ceramic upper section 21 including pin receptors 22 and a plastics lower section 23 in which the "0" ring groove and "0" ring 16 are located. The pins 10 extend downwardly from the holder 7. The holder has a lip 24 which abuts the under surface of the collar 6 to ensure that the lamp 8 is accurately located along the true optical axis of each passageway 12. The socket 11 is illustrated in greater detail in Figures 6 and 7. Figure 6 shows the socket before a mains connection is made, and Figure 7 shows the socket after a connection has been made. The socket has a plastics housing 25 with brass receptors 26 for receiving the pins 10 of the lamp holder 7. The receptors 26 are connected to flexible leads 27- including receptors for crimping to a mains lead 28. Thus, mains connectors can readily be made notwithstanding the dimensions of plugs normally carried by the mains wiring. A threaded brass ferrule 29 is located at the " lower opening of the plastics housing for connection to a standard electrical gland for sealing. A heat shrink sleeve may be positioned about the ferrule 29 for insulation purposes. The base 1 is preferably spaced from the ground mounted housing in which it is sited by a resilient spacer, e.g. a gasket. Figures 8 and 9 show an alternative embodiment particularly for use on curved taxiway sections. In this embodiment, the longitudinal axes of one or both light emitting passageways 12 are offset from the centre line of the module. The base 1 may be provided with cooling fins for heat dissipation purposes. It will be understood that the foregoing is merely exemplary of lighting units in accordance with the invention and that, various modifications may be made thereto without departing from the true scope of the invention. For example, the lighting unit may only comprise one light emitting path. The shape and configuration of the module and its recess may be other than that shown, the various parts of the light unit may be made of alternative materials so those mentioned, and alternative arrangements of the electrical contacts may be provided.

Claims: CLAIMS 1. A lighting unit comprising a base adapted to be secured to the ground with its upper surface generally at ground level and a lighting module releasably connected to the base unit, the lighting module including an opening in its undersurface communicating with a cavity for receiving and retaining a lamp with its bulb uppermost and with its electrical contacts exposed through the module opening for connection to a source of electrical power via cabling, the lighting module also including an upwardly and outwardly inclined light emitting passageway in which is positioned one or more optical lenses, the light emitting passageway communicating at its lower end with a lamp retained in the module cavity and being formed such that the optical axis of light emitted through it is inclined at an angle relative to the horizontal greater than a desired angle of emission, the or each optical lens being arranged to redirect the emitted light so its outward path is at a desired angle. 2. A lighting unit as claimed in Claim 1 wherein two light emitting passageways are provided each angularly disposed relative to each other to define a substantially vee-shaped arrangement. 3. A lighting unit as claimed in Claim 1 wherein the light emitting passageway includes a planoconvex lens and a prism lens. 4. A lighting unit as claimed in Claim 3 wherein the inner face of the prism lens is dichroic coated. 5. A lighting unit as claimed in any one of the preceding Claims wherein one end of the module is located in a recess in the base to form a retaining ledge with the opposite- end of the module held by a single fastening member, such as a bolt. 6. A lighting unit substantially as herein described with reference to Figures 1 to 7 and Figures 8 and 9 of the accompanying diagrammatic drawings.

Inventors: CONWAY DAVID HARRISON, CONWAY, DAVID, HARRISON
Applicants: CONWAY DAVID HARRISON, CONWAY, DAVID, HARRISON
Application year: 1995
Main classification: B64F1
IPC codes: B64F1, F21S8