GB2400433A - Lighting module for paving slabs - Google Patents

Abstract

A rugged and waterproof lighting assembly for embedding in paving or pavement slabs. The assembly comprises a plurality of light emitting diode (LED) lights 2 and an interconnect structure 1 encapsulated in a plastic moulding 3. Some of the LEDs may be connected in series and a Zener diode bypass connected over the severable LEDs.

Description

LIGHTING MODULE FOR PAVING SLABS AND DECKING

This invention relates to a lighting module in particular, but not exclusively, suitable for outdoor use and/or for embedding in paving slabs or mounting in decking or the like for patios.

In recent years there has been an increasing demand for attractive and varied paving slabs for both domestic patio and commercial use. Often there is also a demand for lighting both for decorative and safety purposes.

Provision of separate lighting may add to expense and complexity and can itself become a hazard if it is not permanently fixed or is located where it can cause a fall or cause injury if fallen upon.

The present invention is directed towards providing lighting that is integral to a paving slab and avoids separate lighting units and their attendant problems. The invention is also directed towards providing a lighting assembly that is suitable for casting within slabs or for external mounting in decking.

A further aspect of the invention is to provide an economic circuit arrangement that can be cut without losing power to remaining lights.

In a preferred embodiment the assembly comprises a plurality of LED lights and an interconnect structure encapsulated in a plastics overmolding. An extended lens/light guide on the LEDs protrudes from the overmolding. The circuit enables LEDs more remote from the power source to be severed without disconnection of the remainder.

Some of the LEDs may be connected in series and a Zener diode bypass connected over the severable LEDs.

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À e À À e À The invention is now described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates schematically a preferred embodiment of the invention in external s perspective view, and Figure 2 is a schematic cross-section through an embodiment ofthe invention; Figure 3 is a circuit diagram for a preferred embodiment of the invention; Figure 4 is an alternative part circuit diagram; Figure 5 is a partial perspective view at the start of a molding process; Figure 6 is a partial side view of a further stage in the molding process, and Figure 7 is a partial side view when the mold closes.

Referring to the drawings, the figures show a paving slab with a plurality of integral light sources for use in garden and commercial paving applications. It has an especially useful application in illuminating or highlighting the perimeter of a pathway or paved area. The slabs can also be used to add decorative lighting effects to a paved area or paved footpath.

2s Light Emitting Diodes (LEDs) are used as light sources to reduce the maintenance normally associated with external incandescent and florescent lighting. The LEDs are cast inside the slab at the time of manufacture and are therefore maintenance free. This LED structure also provides safety as there are no loose parts.

The LED lighting may be arranged in different patterns and colours to achieve various effects, the most useful pattern being a single row of lights to highlight the edge of the slab. When the slabs are used in a pathway application they can highlight the safe edge of the path in poor light conditions Other configurations are also envisaged, for À À Àe. e À e e e e e e seeee e e . e ee e example border slabs or edging, which may incorporate lights in a similar way both as an alternative or additional illumination. Within the context of this specification 'paving slab incorporates all shapes and also edging which may not be planar and which may have a larger vertical than lateral dimension.

In the preferred embodiment the lights in each slab are powered by a low voltage direct current (DC) power supply connected by an external cable.

The LED light sources are supported on a substrate comprising a circuit board or other lo form of interconnect, which is protected from corrosion by any suitable means and cast deep inside the slab.

Normally the paving slabs are constructed from concrete but other materials could be used, such as plastics or ceramics, either alone or in combination with one another and/or concrete.

Various construction techniques may be employed to produce the slabs including casting, vacuum or pressure moulding. The construction may vary depending on the manufacturing process as long as the circuit board or other substrate is held in position inside the slab until the material has set In some modifications more than one substrate may be provided. For example two substrates each with a row of lights located at opposite edges of a slab.

Figure I shows the external appearance of a typical slab incorporating illumination in accordance with the invention. In this example, nine lights 2 are arranged in a straight row marking the edge of the slab. The slabs could be laid end to end to make a path with a continuous strip of edge lighting. In this particular embodiment the lights are carefully positioned within the slab to maintain equidistance between lights from slab to slab. A double width path illuminated on both sides could be made using the same slab/lighting design with pairs of slabs side by side rotated at 180 with respect to one another.

It will be appreciated that other slab shapes may be used and lights provided in patterns and/or along more than one edge.

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Each slab is connected to a low voltage electrical supply via a short connection cable 6.

Permanent electrical supply would be provided by an external mains operated power supply with suitable isolation and appropriate maximum current limitation. Operation from battery power or from solar charged sources is also envisaged in some modifications.

Figure 2 shows the general construction of a lighting module suitable for casting in a slab and this assembly may also be modified for use externally of a slab, such as for mounting in decking.

The lighting module comprises a circuit board 1, or other form of interconnect, to which the plurality of lights 2 are connected. Low power consumption and long life is a major requirement for the lights and LEDs are well suited to the purpose. The circuit board and the base of the LEDs are encapsulated in a plastics module 3. The upper part of the LED lens or light guide protrudes out of the plastics module, the plastics forming a seal around the periphery. As the intended use is embedding in a slab or mounting in decking, the lens/light guide of the LEDs is relatively elongate so that it is clear of the rest of the module. Additional light guides may be provided for special purposes.

A typical size for the assembly may be 350 to 400 mm in length, 7 to 10 mm in depth in the region x -x shown in Figure 2, and 12 to 1 5mm in width (i.e. into the paper as viewed in Figure 1). It will be appreciated that this is a relatively elongate, flat structure surrounding a ribbon- like circuit board. For ease of mounting or embedding, the final structure should be relatively rigid, or at least self supporting and resistant to significant bending during normal handling. Greater rigidity is provided by a series of blisters (protrusions) 4, which also serve to encapsulate other electronic components 5 attached to the circuit board.

At various positions along the module mounting pillars 7 are installed which are used to hold the lighting assembly in position as the slab material sets. Once the slab material has solidified the support pillars are cut flush with the under surface of the finished slab.

Other means of supporting the substrate or other circuit board are possible. In Figure 2 the pillars 7 are shown in dotted outline as these are not required for mounting to .: A -s - decking, and modules may be formed without them or they may be cut off. For mounting in decking, the lights may be located in pre-drilled holes and laterally extending flanges with screw holes may be provided on the molding.

s In a simple circuit arrangement each of the four LEDsis provided with a resistor and connected over a 12 volt source. In this way one or more of the LEDs remote from the power source may be cut from the assembly without resulting disconnection of the others. This may be required for example when a slab into which the assembly is cast is cut.

However, in order to reduce power consumption it is proposed to arrange at least some of the LEDs in series. A circuit for a four LED assembly comprising two series pairs is shown in Figure 3 In this circuit each LED pair has a single resistor and a Zener diode is connected from between the LEDs of the pair to the return path, across the outermost Is LED of the pair (i.e. further from the power source or cable 6 as shown in Figure 2).

When all four LEDs are connected, current does not flow through the Zener diodes. If the outermost (along the length of the assembly) of a pair of diodes is severed from the assembly, for example LED 10, then current will flow through Zener diode 11 retaining a complete current path for LED 12. Cutting off both LEDslO and 12 leaves the closer circuit intact, and if three are cut off the second Zener diode provides the return path for the remaining LED.

More than two LEDs may be placed in series with a point between each of the adjacent pairs of the series chain being connected to a Zener diode loop, as shown in Figure 4 for 2s three LEDs. In this instance either the lowermost LED as viewed or two lowermost LEDs as viewed can be removed activating the relevant Zener diode or diodes.

A preferred method of encapsulating the assembly is by overmolding. In view of the ribbon-like structure of the circuit board and the need to hold the board in position within the mold, a support pin and melting insert is used, as now described with reference to Figures 5 to 7.

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Referring first to Figure 5, the printed circuit board 1 has a plurality of holes at spaced intervals along its length. For a board of approximately 350 mm, about seven equally spaced holes is satisfactory. Into each hole a plastics insert 15 is fitted, the insert having a flat, solid cap part and a hollow cylindrical shank that fits into the hole in the circuit board.

The mold, as is usual, has a fixed part and a moving part, each part having a pin that registers with the insert. Referring to Figure 6, the fixed part of the mold has a flat ended pin 16 that bears against the flat cap of the insert. The moving part of the mold lo has a tapered pin 17 that fits inside the shank of the insert.

As the mold closes, the slightly larger diameter of the tapered pin pushes the shank of the insert outwards, as shown in Figure 7. Then when the hot plastics for the injection molding is introduced the plastic insert melts, and resolidifies to form a seal around the edge of the hole where it meets and seals with the injection molded plastics. This ensures continuity of cover in the vicinity of the support and hole in the circuit board.

It will be appreciated that the circuit board could be replaced by another interconnect structure such as a frame and that shapes of lighting assembly other than elongate may be provided, following the general principle of providing a rugged and waterproof module À e À.

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Claims (1)

1. I A lighting assembly comprising a plurality of LED lights (2) and an interconnect structure (1) for supplying power to the LEDs, the interconnect structure and at least part of each LED being encapsulated in a self supporting module and at least some of the LED lights being connected in parallel with a Zener diode connected from a point between adjacent series - connected LEDs to a point on the return current path.

   2. A lighting assembly according to claim 1 in which the interconnect structure is a lo circuit board.

   3. A lighting assembly according to any preceding claim in which the interconnect structure and base portion of the LED lights are encapsulated in injection molded plastics.

   5. A lighting assembly according to any preceding claim in which each LED light has a light guide portion extending outside the encapsulation.

   A method of forming a lighting assembly, the method comprising providing a plurality of LED lights and an interconnect structure for supplying power to the LEDs, supporting the interconnect structure and LEDs in a mold by way of opposing pairs of 2s pins in the mold and a plastics insert that engages with the interconnect structure and pins, introducing molding plastics to the mold which forms an overmolding on the interconnect structure and base of the LEDs and melts the inserts to provide seals at the supported points of the interconnect structure.

   À e* ee * e e e * * À * *e* Àe e e * * * * e À e * e * e À * e e e * À. * e À e 6 A lighting assembly comprising a plurality of LED lights and an interconnect structure for supplying power to the LEDs, at least two of the LEDs being connected in series with a Zener diode connected from a point between adjacent in series LEDs to a point on the return current path.

   7. A lighting assembly comprising a plurality of LED lights and an interconnect structure for supplying power to the LEDs, the interconnect structure and at least part of each LED being encapsulated in a self supporting module.

   lo 8. A paving slab with integral light sources comprising a cast or moulded paving slab having an upper, a lower and side surfaces, and embedded therein at least one substrate on which a plurality of LEDs are mounted with light from the LEDs visible at the upper or side surfaces of the slab, and in which the substrate comprises an interconnect for routing power to each LED, the substrate and at least part of each LED being encapsulated in a self-supporting module.

   9. A paving slab according to any preceding claim including support pillars extending from the module to the lower surface of the slab 10 A method of fabricating a paving slab with integral light sources, the method comprlsmg: providing a substrate on which a plurality of LEDs with light guide coverings are mounted, the substrate comprising an interconnect for routing power to each LED and the substrate and base of the LEDs being encapsulated in a self-supporting module, forming the slab around the substrate, and LEDs while supporting the substrate in position with the light guides extending to the surface of the slab.

   11. A method according to claim 10 in which the substrate is supported from below on mounting pillars with the LEDs extending upwardly.

   À . . À . . : ' : : : .. : : À . À . -9 - 12. A method according to claim 11 in which the pillars are cut flush with the slab bottom surface after formation.

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