Airport lighting unit

A lighting unit particularly for airports includes a base unit (1) for securing at ground level, and a demountable module (2) including a lamp (9) and a pair of oppositely disposed optical elements (11, 12, 17) for directing the light beam along prescribed light emitting paths. Electrical contacts (6, 16) are respectively mounted on the base (1) and the module (2) for mating together when the module (2) is in place, and are situated in a position which is above ground level when the unit is secured to the ground.

The present invention relates to a lighting unit primarily intended for use 
at airports and of the kind which is set on or into the ground to provide 
illumination at ground level adjacent runways and taxiways for the benefit 
of aircraft and other airport vehicles. 
Many different constructions of such lighting units are known including 
some which have the lamp and associated lens unit contained in a casing 
which is separable from the base of the lighting unit in order to 
facilitate servicing and replacement of the lamp and lens assembly. 
However existing constructions are complex and expensive and moreover tend 
to suffer from electrical faults particularly due to water entering the 
electrical contacts between the demountable casing and the base of the 
unit. 
It is an object of the invention to provide a lighting unit particularly 
for airports in which the lamp and lens assembly is contained in a 
demountable module and which forms an inexpensive, reliable and readily 
serviceable unit. 
According to the present invention, a lighting unit particularly for 
airports comprises a base unit adapted to be secured at ground level and 
including first electrical contact members; and a demountable module 
releasably connected to the base unit, said module including a lamp, at 
least one lens forming part of a light emitting path and second electrical 
contact members for mating with said first electrical contact members when 
the module is located in position in the base unit, both said first and 
second electrical contact members being situated at a position which is 
above ground level when the lighting unit is secured on or into the 
ground. 
In a preferred arrangement the module has two oppositely disposed light 
emitting paths each including a said lens. 
According to a feature of the invention the or each lens is a prism lens 
for gathering light from the lamp and which assists in producing the 
required beam shape. 
With such a construction only this component has to be different for a unit 
intended for straight runway/taxiway sections and a unit intended for 
curved runway/taxiway sections in order to provide the correct angle for 
the emitted light beam under all conditions. In a preferred embodiment 
optical means are provided which consists of a bi-convex lens, a dichroic 
filter and said prism lens. As mentioned above, the latter component is 
chosen depending on whether the lighting unit is to be used on a straight 
runway/taxiway section or a curved runway/taxiway section. To this end the 
prism lens is preferably accessible from the outside of the lighting unit 
and can be arranged so that either a straight section lens or a curved 
section lens can be fitted. 
In an alternative arrangement, the inner face of the prism lens can be 
dichroic coated, thus dispensing with a separate dichroic filter, or the 
prism lens can be colored. 
According to an alternative feature of the invention, the module includes a 
reflector for gathering light from the lamp and which assists in producing 
the required beam shape, said reflector extending substantially from the 
lamp to the lens. Where two lenses are provided, a separate reflector is 
associated with each lens. 
In this arrangement, the or each reflector is preferably designed to gather 
as much light as possible from the lamp and direct it to the required beam 
shape. Thus the reflector plays a major part in shaping the beam. Two 
different reflector shapes may be provided, one for straight sections of 
taxiway or runway and one four curved sections, in order to provide the 
correct angles for the emitted light beam under all conditions. 
In a preferred construction the lamp fits into a lamp holder which forms a 
part of the module and is releasably secured to the main part of the 
module such that the lamp itself extends into the main part of the module. 
The second electrical contacts are carried by the lamp holder for 
engagement with the first electrical contacts in the base unit when the 
module is located in position. 
The lamp holder may be made from a translucent material so that a small 
amount of light or a glow is visible from the top of the unit to indicate 
when it is alight to an observer at a remote point, such as in a control 
tower. 
The module is preferably located in a recess in the base unit and secured 
therein by a single fastening member, such as a bolt located to one side 
of the module. In such an arrangement opposite side walls of the module 
and the abutting walls of the recess can be slightly angled or offset such 
as to restrain the module against movement out of the recess when the 
securing bolt is tightened.

Referring to the drawings, the lighting unit to be described is 
particularly intended to be set in the surface of a runway or taxiway at 
an airport. The unit comprises two main parts namely a base generally 
indicated at 1 and a demountable module generally indicated at 2. The base 
1 comprises a circular metal casting having a central lower portion 1a and 
a peripheral region 1b for resting in a preformed ground recess. This 
latter region is provided with holes 3 to receive bolts by means of which 
the lighting unit is secured in position. The central portion 1a supports 
a cable gland 4 through which an underground cable 5 can be fed to 
electrical contacts 6 located to one side of a recess 7 formed in the 
upper surface of the base 1. The recess 7 is of generally rectangular form 
but includes a salient or bay 7a. The demountable module 2 itself consists 
of two interconnected parts, namely a main module housing 2a and a lamp 
holder 2b. The main module housing, which may be an alloy casting, is 
hollowed to provide a central horizontal cavity 8 for receiving a lamp 9 
and two oppositely directed cavities 10 shaped to be of generally 
cylindrical form. Each cavity 10 houses a bi-convex lens 11 adjacent the 
lamp 9, a dichroic filter 12 separated from the bi-convex lens 11 by a 
spacer ring 134 and a prism .lens 17 separate from the dichroic filter by 
a further spacer ring 13b. 
The demountable module 2 includes a pair of apertures 25 adjacent the outer 
end of each cavity 10 for receiving bolts 23 securing each prism lens 17 
in place. The bolts 23 are positioned so as to be easily accessible to 
facilitate the substitution of either straight or curved section lenses. 
Alternatively, the appropriate prism lens can be fixed in position with an 
adhesive. 
The connecting pins 9a of the lamp 9 protrude from the housing 2a and are 
received into a complementary electrical socket 14 in the lamp holder 2b 
which effectively supports the lamp. The lamp holder 2b may be made of a 
translucent plastics material and is secured to the housing 2a in a 
readily releasable manner by means of a bayonet connection comprising a 
pair of studs 15 projecting from the housing which fit into shaped 
apertures (not shown) in the lamp holder. Thus the lamp holder 2b is 
inserted into its location at an angle and then twisted slightly to engage 
the bayonet connection so that it is securely located against an O-ring 
seal 22. It can be readily released by turning the holder in the opposite 
direction and withdrawing it. The contacts of the socket 14 are 
electrically connected to pins 16 projecting from the underside of the 
lamp holder and which engage with the electrical contacts 6 when the 
module 2 comprising the interconnecting housing 2a and lamp holder 2b is 
lowered into the recess. 
The module 2 is secured in position in the recess 7 of the housing by means 
of a securing bolt 18 which passes down through the main body of the 
housing into a threaded aperture in the base 1. The lamp holder 2b is then 
located in the bay 7a. 
In order to prevent any undesirable movement of the module 2 relative to 
the recess 7 when it is secured by the single bolt 18, the opposite 
abutting sidewalls 19, 20 of the recess 7 and the module 2 can be offset 
at a small angle, e.g. 2.degree. which serves to prevent relative 
movement. However, once the bolt 18 is released, the module can be readily 
withdrawn from the recess for servicing. If desired a spring (not shown) 
may be arranged underneath the module so that it pops up from the recess 
when the bolt 18 is released in order to assist in removing the module 
from the recess. The lamp can be quickly and easily changed by simply 
releasing the lamp holder 2b and withdrawing the lamp from the cavity 8. 
A rubber or similar strip may be fixed around the top edge of the module 
aperture in base 1 so that when module 2 and lampholder 26 are inserted 
into base 1 they are sealed around their periphery. 
It will be noted that with the construction described, the mating 
electrical contacts 6, 16 are situated well above the ground level GL and 
hence are not liable to be affected by ground water running into the 
contacts, as is readily possible with prior art constructions. The area of 
the contacts is also protected by an O-ring or gasket seal 21 and a 
further such seal 22 is provided between the lamp holder 2b and the 
housing 2a. Drainage apertures (not shown) are also provided in the base 
unit 1. 
By reason of the features of the present invention, not only is it possible 
to provide a lighting unit which is identical for both straight and curved 
runway/taxiway sections, apart from the outer prism lens which is readily 
changeable; but the lamp holder can be removed and the lamp replaced in a 
very short time. 
By reason of the simple and inexpensive nature of the module 2 it can, if 
desired, be treated as a throw-away unit, which means that servicing of a 
faulty module can be speedily carried out by merely fitting a replacement. 
While a particular embodiment has been described it will be understood that 
various modifications may be made. 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 and the various parts 
of the light unit may be made of alternative materials to those mentioned.