Field

The present invention relates to luminaires for inductive power transfer lighting systems; and to an inductive lighting system using the luminaire. The luminaire and lighting system of the invention may be for agricultural use, such as in buildings that are used for horticulture or animal husbandry.

Background Inductive power transfer lighting systems can find use in harsh operating conditions.

In agricultural use, such as in buildings used for horticulture or animal husbandry, high levels of dirt and dust are present. There is a need to cleanse frequently and thoroughly by washing. An inductive system can have advantages. The power cable is generally dirt and water proof. It is not required to make wiring connections between the cable and the light fittings (luminaires) employed. Power transfer is wireless. Therefore the luminaires employed can be sealed or substantially sealed units. In a typical known system luminaires are clipped onto power cables, by clamping together two parts of the luminaire about the power cabling. This ensures close proximity between a cable and the receiver wiring coil within the luminaire. This type of system may be subject to ingress of dirt or water, in-between the parts clamped together. It can be relatively time consuming fitting a large number of luminaires onto a cable, in an extensive system.

Therefore there is a continuing need for improved lighting systems, especially for use in harsh environments. Summary

According to a first aspect the present invention provides a luminaire for an inductive power transfer lighting system; the luminaire comprising:

a luminaire body; and

a receiving coil within the body and electrically connectable to a lamp;

wherein the luminaire body is provided with a slot, open at a periphery of the body to receive a power cable; whereby in use the luminaire can hang from the power cable mounted in the slot and the receiving coil receives power from the cable. The inductive power transfer lighting system may be for use in agriculture, for example for use in agricultural buildings such as sheds, greenhouses or other buildings employed for horticulture or animal husbandry. Horticulture may include fruit and/or vegetable growing. Animal husbandry may include rearing of poultry, pigs or other animals. The luminaire may therefore be waterproof or even hermetically sealed, to avoid failure due to ingress of contaminants such as dirt or water. The luminaire may be washable. The luminaire may comply with the Ingress Protection Rating (IP rating) IP69K.

The slot may be open at a periphery of the body. The opening of the slot may extend across a width of the body. Both the opening of the slot and the width of the slot may extend across a width of the body. This allows the luminaire to be hung from the power cable by: aligning the opening of the slot with the longitudinal direction of the cable; and placing the slot about the cable. Other slot arrangements may be employed. A power cable is received into the slot and the luminaire can then hang from the power cable. The power cable will rest in the slot, typically at or close to a closed end of the slot, distal to the opening at the periphery. A closed end to the slot is advantageous where the luminaire is waterproof or even hermetically sealed. The slot may be sized so that a power cable for use with the luminaire may be a relatively loose fit. Alternatively the slot may be sized so that the power cable employed is a snug or even an interference fit. The cable may then be gripped by the slot, for example at a selected depth in the slot. For example the slot may narrow near the end distal to the opening in the periphery of the body, so as to grip the cable at or near the distal end of the slot. The opening of the slot may vary in height, for example across the width of the body. For example, the opening of the slot may be tapered, with a greater height at one end, typically towards or at one edge of the luminaire body. This can aid in placing the slot about a power cable. The greater height (more open) part of the slot opening allows easier location about the power cable. Where such a tapered opening is employed, the slot itself may also be tapered. The slot may be tapered in height correspondingly to the height of the opening of the slot, across its width.

Conveniently the slot is formed and arranged to allow the luminaire to hang from the cable without requiring additional fixings to secure it, such as straps or clips. The slot may be angled upwards into the body of the luminaire from the opening at the periphery, when the luminaire is in an in use position.

The slot may be arranged so that when the luminaire hangs from the lamp, for example, hangs freely, light from the lamp is transmitted in a desired direction.

Additional fixings may be provided to aid in fixing the luminaire in a selected location along the length of the cable and/or for fixing the position of the luminaire about a cable, in use.

When the luminaire is hung from a power cable, the power in the cable can be transmitted to the receiving coil in the body of the luminaire. The received power can in turn be used to light an electrically connected lamp. To achieve reasonably efficient transmission of power, by induction, the cable should be close to the receiving coil when it is located in the slot.

The receiving coil may be elongate with a spiral winding or windings of coil wire running along its length. Conveniently the receiving coil is elongate and curves along its length to be disposed about a power cable when the cable is in a rest (in use) position in the slot. The receiving coil may be positioned in the body of the luminaire so as to be disposed about a power cable in the slot in a plane substantially at right angles to, or at right angles to, the longitudinal direction of a power cable in the slot; in use. A receiving coil that 'wraps round' i.e. fits closely about, a power cable placed in the slot, can interact well with the fields produced from the current flowing in the cable. The receiving coil may be elongate and circular in curvature.

Typically the receiving coil has a generally 'C shape, with the two ends of the opening in the C disposed to either side of the slot in the luminaire body. Thus the ends of the coil may be spaced apart so that the slot passes there through. This allows the cable to be located in the slot and at a selected position with respect to a circular or curved coil. A slot sized to accept a power cable up to a closed end can provide a positive location with respect to a coil fitted within the body of the luminaire. This can aid in consistently obtaining the desired power transmission.

The receiving coil may be provided with a core to support the coil. Typically a magnetic core, such as a ferrite core will be employed, to aid in power transmission. Thus for a circularly arranged or curved coil a 'C shaped ferrite core may be used as shown hereafter with respect to a specific embodiment.

The receiving coil is electrically connectable to a lamp. The luminaire may include a lamp connected to the receiving coil by appropriate circuitry. The lamp may be mounted inside the body of the luminaire or inside a sealed or sealable compartment attached to the luminaire body.

Conveniently the lamp is an electroluminescent device that may comprise one or more light emitting diodes (LEDs) or alternatively one or more other types of electroluminescent device such as one or more light emitting electrochemical cells (LEECs).

The lamp, such as an LED or LEEC lamp can be powered inductively by an intermediate frequency alternating current (IFAC). An IFAC operating at about or at 50kz with a current of from 1 .5 to 2.5 amps, for example about 2 amps or 1 .9 amps may be employed.

Such a frequency allows the use of the alternating current induced in the receiving coil to power a lamp without rectification. The frequency may be sufficiently high to avoid disturbing stock, such as poultry, that can perceive lower frequency lighting as a flashing light source. Thus a luminaire and lamp combination may be electrically connected by circuitry not including rectification. Circuitry may include a capacitor or capacitors, such as polyester capacitors, to provide a tuned secondary load.

The luminaires may be employed with existing inductive lighting systems for agriculture - where known luminaires are clipped onto power cables.

The luminaires of the present invention may be provided with a unitary or substantially unitary luminaire body. The luminaire body may be sealed or sealable so as to be waterproof or even hermetically sealed. Conveniently the luminaire includes a lamp within the body or within a sealed or sealable waterproof or hermetically sealed compartment. Where a compartment is employed it may be in sealing engagement with the body to provide a sealed luminaire body and lamp compartment arrangement.

Additional protection from damage, dirt or water, may be provided by potting at least part of the luminaire body i.e. filling at least part, for example all, of the luminaire body with a suitable potting compound as is known in the art. The use of a potting compound to fill unoccupied space in the luminaire body may also provide improved electrical reliability. The luminaire body may have first and second opposed faces, spaced apart to contain the contents of the luminaire, the opposed faces having a joining wall or walls extending there between. The space between the first and second opposed faces may define a width of the luminaire across which both the opening of the slot and the width of the slot each extend. The depth of the slot extends into the luminaire body with sides of the slot open at each opposed face. The slot may extend at an upwards angle into the luminaire body and the luminaire may be weighted so that the luminaire hangs on the power cable under gravity without additional fixings being required.

The first and second opposed faces may be flat or substantially flat faces, such as rectangular, square or trapezoidal faces. The joining wall or walls may be at right angles or substantially at right angles to the plane of at least one of the first and second faces. The joining wall or walls may be at right angles or substantially at right angles to the plane of each of the first and second faces.

For example the body of the luminaire may be generally cuboid in form. In a convenient and compact form, the body of the luminaire may be generally in the form of a cuboid surmounted with a part cylinder, or other arched solid. The part cylinder or other arched solid may be of the same width as the cuboid i.e. the first and second opposed, generally flat faces may each have the form of a rectangle, square or trapezoid surmounted by an arch, that may be a part circle arch. The arched part of the body is upper in use.

In such a body the power receiving coil may be of a generally C shape and located in the part cylinder (or other arch shaped) part of the body. The slot and its opening extend across the width between the first and second opposed faces. The slot may extend into the body at an upwards angle from the opening, into the interior of the C shape of the power receiving coil. The slot may end so that a power cable placed in the slot is positioned substantially in the centre, or in the centre, of the C shaped coil. The circuitry for the lamp and the lamp itself are located below the coil in use. For example both the circuitry and the lamp may be inside the luminaire body. The light from the lamp is emitted through a window or windows of the luminaire body. The lamp may be at the bottom of the luminaire body with a window or windows at or near the bottom, allowing light output.

Such a luminaires can be easily hung from a power cable and the lamp can project light generally downwards. Luminaires having bodies with opposed flat faces can be stacked one on the other when in storage, with reduced risk of damage, especially if the window or windows that emit light from the lamp are in, or mounted on, a bottom edge of the luminaire body. In use, where more powerful lighting is required in a location these compact luminaires can be positioned more closely together, even touching, along the power cable.

A luminaire of the invention may thus include;

a C shaped receiving coil with a ferrite core;

circuitry connecting to a lamp that does not have rectification, but includes capacitors to provide a tuned secondary load; and

a mid power LED lamp, for example 0.5 to 1.5W or even 0.7W.

Advantages of luminaires of the invention can include; easy installation as the luminaire can be hung anywhere along a power cable run;

a low voltage and low current secondary circuit that can reduce fire and other safety hazards; and

consistent power transfer by positive location, without difficulty of the power cable inside the C shape of a receiving coil and core.

According to another aspect the present invention provides an inductive power transfer lighting system comprising at least one of the luminaires of the invention as described herein. The lighting system may be of the generally known forms, such as those employed for agricultural use.

A typical system will include a power distribution hub to distribute alternating current (AC) electricity of a selected current and frequency, along a power cable circuit (a bus).

The distribution hub will typically convert mains electricity to the desired form for the lighting system. A constant current system is generally used to provide a mostly sinusoidal AC waveform across the range of complex impedances applied to the power cable. This is cost effective and simplifies regulatory compliance such as Electromagnetic Compatibility Compliance (EMC). Other components may include a dimmer system to alter light output and a timing clock to switch the lights on and off as required.

In laying out the lighting system at a location such as in an agriculture shed, the power cable is distributed out from the distribution hub to locations where lighting is desired. It is convenient in many cases to have both the outwards run of cable, from the power distribution hub, and the return run of cable, back to the power distribution hub, bundled together. The bus has two cable portions running together, typically twisted together, out from the power distribution hub to a distal end of the cable run. If a single length of power cable is used, the cable turns back along itself at the distal end of the cable run. Alternatively two cable lengths are employed and are electrically connected by a termination piece at the distal end of the cable run.

Thus in such arrangements, there are two power cable portions present ('out' and 'back') along the cable run where a luminaire may be positioned. One of the power cable portions is placed in the slot of a luminaire of the invention to allow it to hang and receive power into its receiving coil. The other portion of cable may pass by the body of the luminaire. Conveniently the luminaire body may be provided with a fixing on the body to engage with the cable portion not in the slot. For example a tie, clip, groove or grooves that can locate or even grip the cable portion that is not in the slot, at the luminaire body. Such an arrangement can aid in fixing the location of the luminaire and its attitude (rotational position and/or angle with respect to the general longitudinal direction of the power cable within the slot). Where the power cable does not run with the out and back cable portions bundled together, but instead as a single cable running round the location in a loop, then the luminaire may hang from a single cable portion at its selected location; with or without the use of an additional fixing to aid in securing to the cable and/or positioning the luminaire with respect to the cable direction.

Brief Description of the Drawings

Figures 1 a and 1 b show a luminaire in elevation and end elevation;

Figure 2 shows the interior of a luminaire; and

Figure 3 shows the luminaire of figures 1 a and 1 b hanging on a power cable arrangement, in a perspective view.

Detailed Description

Figures 1 a and 1 b show in elevation (figure 1 a) and end elevation (figure 1 b) a luminaire 1.

The luminaire 1 has a body 2 including first and second opposed faces 4,6 and a connecting wall 8 in between. The lower portion 10 of body 2 is a generally trapezoidal prism, slightly narrower at the bottom 15 of the body 2. The upper portion 12 of the body 2 is a part cylinder in this example. The body 2 will typically be made of a plastics material and may be dark coloured to reduce interference from livestock.

The body 2 is sealed, for example by use of adhesives or heat fusion to join faces and walls together, where they are not formed integrally. Other sealing techniques such as 'Ο' ring seals may be used, for example to seal a window to the body of the luminaires of the invention.

A window 14 at the bottom of the body 2 allows light from an integral lamp (see figure 2) to be directed outwards and downwards.

The body of the luminaire 2 has an open end 16 for slot 18 running across the full width W of wall 8. The slot 18 also extends across the full width W of the body. The slot 18 is angled upwards from opening 16 into the body 2 and terminates at closed end 20 where a power cable sits when the luminaire 1 is hung from it.

In figure 1 b the insertion of a power cable into the opening 16 is suggested by dashed line 21 . Where the power cabling utilised to power the luminaire has two cable portions running together (out and back to a distribution hub) then the power cable portion that is not in slot 18 may be conveniently located in cup shaped clip 22. (See figure 3)

Figure 2 shows the interior of a luminaire 1 of the type depicted in figures 1 a, 1 b with like parts numbered the same.

A receiving coil 24 wrapped round a ferrite core 26 forms a circular C shape about the closed end 20 of slot 18. Thus a cable located at or close to end 20 of the slot 18 will have the coil 24 disposed about it. The coil 24 and core 26 can obtain power from a power cable and transmit it via circuitry 28 to an LED lamp 30 located at the bottom 15 of the body 2. Light from the lamp is emitted from window 14 (figure 1 a).

The interior of the body 2 may be filled, partially or completely, with a potting compound to secure and further protect the electrical components.

Typical operating parameters for a cable would be a frequency of 50kz with a current of about 2A, e.g. 1 .9A.

Figure 3 shows the luminaire of figures 1 a and 1 b on a cable bus 32 that has both out and back power cable portions 34, 36 running twisted together from a power distribution hub (not shown, in the direction of arrow H). Power cable portion 34 is fitted into slot 18 at the closed end 20 distal to the opening 16. The opening 16 of the slot 18 may have greater height at one end to aid initial insertion of cable portion 34 into position. Cable portion 36 is located in clip 22. The luminaire 1 is thus hung from power cable portion 34 to allow transfer of power. Light emitted from window 14 can project downwards and outwards.