TITLE: NAVIGATION LIGHT

Introduction This invention relates to navigation lights particularly for use with shipping.

Background of the Invention

There are international standards that determine the use of navigation lights, especially with regard to shipping. International standards dictate that a vessel should carry two navigation lights towards the bow of the vessel; one directed to the starboard and one to the port side of the vessel. The positioning of the navigation lights and the field of the projected light is critical and it has been agreed that each front light should have a beam confined to an arc of 112.5°. A green light is used on the starboard side of the vessel, with a red light on the port side. It is also stipulated that a white light should be used at the stern of the vessel with a beam defining an arc of 135° . This means that the three lights circumscribe 360°, which in effect, means that a light can be seen from any position around the vessel.

It is essential that the boundary at each end of the arc of light is as sharp as possible because fuzzy boundaries cause excessive overlap which can make the reading of the manoeuvring of a vessel difficult from afar. There are several National and International Standards prescribing the performance of navigation lamps. The most widely used standard COLREG 72 prescribes a practical cut-off to be reached, for the forward boundary, at between 1 and 3 degrees outside the prescribed sector. For the aft sectors a practical cut-off must be reached within 5 degrees outside the prescribed sector.

In recent years, bulb based navigation lamps are

being replaced by light: emitting diodes (LEDs) which are significantly more energy efficient and have a significantly longer lifespan than filament bulbs . Light emitting diodes use less power and have a considerably longer life span than filament bulbs . A navigation light using light emitting diodes is conventionally similar to the bulb design, namely that an array of light emitting diodes are positioned centrally of a baffle, the extremities of which define the boundary of the light beam. The sharpness of the boundary increases in accordance with the distance from the light emitting diode to the tip of the baffle.

There is an ongoing push for navigation lights to be as small as possible and the use of an array of LEDs fully sealed in small plastics enclosures has become very popular. However, the small size of such lights makes it difficult to provide the sharpness of boundary that is dictated by the standards .

It is these issues that have brought about the present invention .

Sτiτmnary of the Invention According to one aspect of the present invention there is provided a navigation light comprising arrays of light emitting diodes (LEDs) , the arrays being spaced apart and surrounded by an optical baffle whereby in use, the edges of the baffle constitute boundaries of the light emanating from the LEDs .

Preferably, a first array is pointed to a first edge of the baffle to define a first boundary and a second array is pointed to a second edge of the baffle to define a second boundary.

In a preferred embodiment, the baffle has opposed

outwardly diverging walls , each array being positioned in the plane of one wall and directed towards the edge of the opposite wall . Each array may comprise a line of equally spaced LEDs. Preferably, the LEDs are located on a circuit board located within a housing and a lens covers the front of the housing to define a sealed unit.

According to a further aspect of the invention there is provided a navigation light comprising: a housing covered by a curved outer lens; the housing supporting a circuit board with a plurality of LEDs ; and an optical baffle surrounding the LEDs and terminating in a peripheral boundary adjacent the lens characterised in that the LEDs are positioned in at least two spaced arrays inclined to the circuit board so that the LEDs face opposite sides of the baffle and the edges of the baffle constitute boundaries of light emanating from the LEDs .

Description of the Drawings

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

Figure 1 is a plan view of a navigation light; Figure 2 is a side elevational view of the light of Figure 1;

Figure 3 is a cross sectional view of the light taken along the lines A-A of Figure 1;

Figure 4 is a cross sectional view of the light taken along the lines B-B of Figure 1;

Figure 5 is a perspective view of an optical baffle that forms part of the light of Figure 1; and Figure 6 is a view of Figure 3 showing the arc of the beam of light emanating from the navigation light.

Description of the Preferred Embodiment

A navigation light 10 is of substantially rectangular configuration as shown in Figures 1 and 2 and is mounted in a plastics mount 30 that has longer sides 31, 32 of semi-circular profile and shorter ends 33 , 34. The underside of the mount 30 includes a pair of opposed mounting flanges 36, 37 with holes 38, 39 to support fasteners (not shown) so that the mount 30 can be screwed against a support surface. The light 10 which is a sealed unit is adapted to clip between the longer sides 31, 32 of the mount 30.

The light 10 comprises a base 11 that supports a centrally mounted circuit board 12 that in turn supports two parallel arrays 13 and 14 of four equally spaced LEDs 20. A convex mirror 15 extends over the circuit board 12 between the arrays of LEDs 20 and the base 11 also supports an optic baffle 40 that is surrounded by a clear plastics lens 26 of spherical profile in section with elongate straight sides 27, 28 as shown in Figure 1.

Each array 13, 14 of LEDs 20 is positioned along the shorter ends of the light 10 with the LEDs 20 inclined at an angle of about 50° to the horizontal. The optic baffle 40 is shown in detail in Figure 5. The arrays 13, 14 of LEDs 20 are located at the base of upwardly inclined end walls 41, 42 that join upwardly inclined side walls 43, 44. The upper edge 45 of each end walls 41 , 42 defines one boundary of the light shining from the array of LEDs 13, 14 on the opposite end wall. In this way the light from the LEDs shines out through the shorter ends of the light 10 past the upper edge 45 of the baffle 40.

The role of the baffle 40 is illustrated with particular reference to Figure 6 from which it can be seen that the left hand array 13 of LEDs has one boundary 50 of the beam running to the right hand tip of the baffle and

the other boundary 51 of the beam extending virtually at right angles to the light 10. When the other array 14 comes into effect which reverses this situation it can be seen that the total beam in fact transcribes an arc of 135° . It can also be seen that the distance from the LEDs 20 to the edge 45 of the optic baffle 40 is 33.5mm. This is considerably greater than would be the case if the array of LEDs was simply positioned centrally of the light thus reducing the distance from the LED to the edge of the baffle. Thus, the light of the subject application through use of two inclined spaced apart arrays 13, 14 of LEDs 20 provides a much sharper boundary than would be the case with a single array positioned centrally of the light.

LEDs of the kind used herein project a cone of light having an included angle of 120° . The light is at its most intense at the centre of the cone. The array of LEDs is thus positioned so that the angle between the centre of the LED and the edge of the optical baffle is 10° off the plane of the wall of the baffle, thus ensuring that a bright light is hitting the edge of the baffle to define a pronounced and well defined boundary.

As shown in Figure 5 the arrays 13, 14 of four spaced LEDs are located in a slot at the base of each end wall 41, 42 of the baffle 44 the top surface of the LEDS are in the same plane as the wall and the wall is inclined rearwardly to the vertical by an angle of 50° . To improve the aesthetics of the light the small convex mirror 15 is placed over the circuit board to extend across the gap between the base of the end walls .

It is understood that the orientation of the LEDs to the optical baffle would vary in accordance with the role of the light. Thus, the bow lights would project red or green light in an arcuate beam of 112.5°.

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The lights described above utilise the current LED technology whilst satisfying the toughest international standards .