GB2299659A - Lighting systems - Google Patents

Abstract

A lighting system for a garden comprises a number of fluorescent lamps supplied by a low voltage (12 volt) supply in a cable extending between lamp sockets. The sockets each contain converter circuits to generate a high voltage high frequency power supply for a respective lamp. The system therefore has low voltage distribution lines which can be informally and safely laid in a garden and the light output is comparatively much higher and/or cost effective than when using other forms of lamp.

Description

LIGHTING SYSTEM; The invention relates to lighting systems.

The invention relates more particularly to lighting systems primarily for domestic use usually but not necessarily outside the home and the invention will be described in relation to a garden lighting system.

According to the invention, there is provided a lighting system for supplying a number of fluorescent lamps separated from one another and distributed around a region to be illuminated, the system including a number of sockets for the fluorescent lamps, low voltage electrical supply cables connecting the sockets to a single supply point, and included in each socket an electrical circuit for converting a low voltage low frequency supply to a high voltage high frequency power supply for a respective fluorescent lamp.

The lighting system may include a transformer for connection between the single supply point.and a mains supply to convert the mains supply to a low voltage supply.

The lighting system may include a light sensitive switch connected to turn power supplied to the sockets on and off automatically due to changes in ambient light.

A garden lighting system according to the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic layout of the system; Figure 2 is an isometric view of the system; Figure 3 is a circuit diagram for lamp outlet sockets for the system; and Figure 4 is an exploded isometric view of a lamp assembly for use in the system.

Referring to the drawings, in Figure 1 a plug 9 is provided for connecting a transformer 10 a domestic mains supply to convert the mains voltage from 240, 110, or 100 volts as appropriate, to 12 volts.

The low voltage 12 volt supply, usually at a low frequency of 50 or 60 Hz, but may be at a lower frequency including direct current, is fed via a light sensitive switch 11 to an outlet socket or single supply point 12. A plug 13 is connected to a length of low voltage supply cable 14 which has a number of lamp sockets 15 connected to it along its length. The cable 14 may be arranged in a closed loop from the supply point 12. Each lamp socket 15 is associated with an electric circuit (see Figure 3) and is arranged to receive plug terminals of standard sized miniature fluorescent lamp (not shown). The lamps are usually rated between 5 and 11 watts.

In Figure 2, three different forms of standing lamps are shown by way of illustration. The lamps are designed for use outside at a house (a hotel or other building) to illuminate a garden or driveway, for example. The cable is usually simply laid on or near the surface of the ground and connected from underneath base stands of each lamp.

For each lamp socket there is provided a converter circuit (see Figure 3) comprises a full-wave rectifier 20 and an optional zener diode 21 to limit the voltage developed across the rectifier 20. A multiple wound transformer 22, which is automatically switched by a transistor 23, supplies starting voltages and normal power at 50 volts, 170 milliamps and frequency at 24 KHz to lamp outlet sockets 24 for connection to a fluorescent lamp 25. The transformer 22 as required also supplies in use power to the sockets 24 for heater filaments in the fluorescent lamp 25.

The circuit in Figure 3 is known per se for converting a low voltage input and supplying appropriate power to drive a fluorescent lamp.

Other similar circuits are also known and may be used in the described lighting system.

The circuit of Figure 3 may include a light sensitive switch having a sensor which responds to the level of ambient light and arranged so that each lamp 25 is turned on and off automatically and individually.

This can be arranged to act instead, or additionally, to the switch 11 in Figure 1.

In Figure 4, a lighting arrangement is shown which is particularly and conveniently designed for assembly "on site", allowing it to be more readily packed and transported. A base stand 30 has opposing slots 31 to accept power supply cables 32 and 33. Each of the cables extend inside a tube 34, which fits snugly to the base stand, and are connected to a terminal board (not shown) on the bottom surface of a screwed socket 35. An outlet adapter 36 is arranged to be a tight fit into the socket 35 and its body surrounds and supports the circuit shown in Figure 3. The adapter 36 has sockets (not shown) in its upper surface for receiving plug terminals of a standard miniature fluorescent lamp 37. A weather protecting cover 38 releasably fits over the lamp 37 and a ground stake 39 fits into the bottom of the base stand 30.

The described lighting system can conveniently be provided as a kit of parts for assembly and installation by a purchaser and laid out according to the purchaser's requirements. The kit can normally be packed quite flat in a single carton which includes a length of low voltage cable which can be easily cut to length and safely run in the ground or around the inside of a dwelling. As power in the cable is at low voltage, the system is safe even if the cable is accidentally broken and touched. The use of alternating voltage (at relatively low mains frequency) reduces or eliminates any tendency otherwise for the conductors of the cable to corrode, and in this case, especially because a full-wave rectifier is used, the system is not polarity sensitive.

The power supplied by the cable is converted at each fluorescent lamp outlet socket and as the distributed supply in the cables is at low voltage, power losses in the cables are low. In an earlier proposal, where fluorescent lights were used in a space lighting system, the distributed power was at high frequency and consequently not satisfactory and certainly not suitable for an informal installation around a garden or a house. It is also known to use low voltage direct current distribution systems for garden lighting and employ halogen lamps. However, such systems and the use of halogen lamps compare unfavourably with embodiments of the present invention. Both the performance, especially long term, of the cables and the lamps is less reliable, and the cost of installation and power consumed per lumen of light output is considerably higher.

Claims (5)

1. A lighting system for supplying a number of fluorescent lamps separated from one another and distributed around a region to be illuminated, the system including a number of sockets for the fluorescent lamps, low voltage electrical supply cables connecting the sockets to a single supply point, and included in each socket an electrical circuit for converting a low voltage low frequency supply to a high voltage high frequency power supply for a respective fluorescent lamp.

2. A lighting system according to claim 1, including a transformer for connection between the single supply point and a mains supply to convert the mains supply to a low voltage supply.

3. A lighting system according to claim 1 or 2, including a light sensitive switch connected to turn power supplied to the sockets on and off automatically due to changes in ambient light.

4. A lighting system according to any one of claims 1 to 3, including one or more lamps substantially as described with reference to Figure 4.

5. Lighting systems substantially as herein described with reference to any one or more of the Figures 1 to 4 of the accompanying drawings.