GB2203527A - Lighting unit - Google Patents

Abstract

A spotlight comprises a cap (1) to be received in a standard electrical outlet, a conical housing (3, 4) containing a transformer, an end wall (15) having a recess (19) and a mounting (12) for a low voltage reflectorless lamp (13) to protrude into the recess which provides the reflector for the lamp. <IMAGE>

Description

Lighting Unit This invention relates to lighting units and more particularly to a spotlight unit which may be used to replace a common spotlight unit operating at the standard mains voltage of for example 240 volts but which incorporates rectification or transformer means to enable the spotlight to use a low voltage halogen lamp.

A standard form of spotlight lamp comprises a generally cylindrical body having a cap at one end which may be of bayonet or Edison screw type adapted to fit into a standard electrical socket outlet and having a heavy glass wall at the opposite end, the housing enclosing a filament to which is supplied current at the standard mains voltage. In recent years it has been appreciated that it is preferable to operate at low voltage, for example 12 volts and various lighting fittings using quartz halogen lamps operating at this voltage have been proposed. Some of these fittings are designed to use the available dichroic lamps which are constructed with an integral reflector which reflects much of the light generated by the filament but allows much of the heat to pass through to permit this heat to be dissipated. These lamps are very expensive.

According to the present invention a spotlight comprises a cap to be received in a standard electrical socket outlet, a generally conical housing, electrical transformer means located in the narrower portion of the housing, a lamp mounting located intermediate the ends of the housing, and an end wall extending across the wider end of the housing, the end wall having a recess with a hole at the bottom of the recess, the lamp mounting and the recess being arranged so that a low voltage reflectorless lamp mounted in the mounting protrudes through the hole into the recess, the surface of the recess being shaped to provide a reflector for the lamp.

The spotlight of the invention is intended to be used with one of the standard reflectorless halogen low voltage lamps which are now available and which are substantially less expensive than those having an integral reflector and which are also believed to be more reliable and to have a longer operating life.

Preferably at least the broader portion of the housing is of plastics material and also preferably the end wall is of metal. The broader portion of the housing may comprise a plurality of spaced rings and bridges interconnecting the rings. This provides an open structure which permits heat to be dissipated.

Although the end wall may take various forms provided that it contains the recess which affords a reflector for the lamp, in a preferred construction the recess is surrounded by an annulus which is domed away from the cap end of the spotlight.

The invention may be carried into practice in various ways but one spotlight embodying the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a side elevation of the spotlight; Figure 2 is a top view of the spotlight; Figure 3 is a bottom view of the spotlight and Figure 4 is a section through the spotlight on the line IV-IV of Figure 2.

Although the spotlight may take any orientation it will be described in the orientation shown in Figure 1 which is that which will be used in the majority of cases, the spotlight being arranged to direct light downwardly.

At the upper end of the spotlight there is an Edison screw cap 1 of a size to fit a standard electrical socket outlet of the size normally employed for lighting operating at the standard mains voltage of, for example, 240 volts. It will be apparent that the cap could have an alternative form such as that of the standard bayonet.

Attached to the cap 1 is a two-part housing having an upper part 3 and a lower part 4 the two parts being interconnected by three columns 5. The outer envelope of the housing 3,4 is generally conical and corresponds to that of a standard single part unperforated spun metal conical spotlight body. The upper part 3 contains encapsulated in resin an electronic rectification or transformer circuit which accepts the mains supply at 240 volts 50 Hz and delivers through leads 6 direct current at 12 volts.

The lower part 4 of the housing is a plastics injection moulding and consists of an upper ring 7, a lower ring 8 of greater diameter and three bridges 9 which interconnect the upper and lower rings. As can be seen from Figure 4, the upper ring 7 includes a tranverse wall 11 on which is mounted a mounting 12 to receive a two pin 12 volt reflectorless bulb 13 which, in the example being described, is a 50 watt bulb manufactured under the name Wotan of West Germany and sold under the identification SIC 64016. This bulb and others to a similar specification are readily available and are for example in use in the lamps at traffic lights.

The spotlight is completed by a transverse wall 15 of spun aluminium, the wall thus being a body of revolution and having an outer axially extending rim or flange 16 which is a press fit over a cylindrical wall portion 17 formed at the lower extremity of the lower portion 7 of the housing, an intermediate domed or conical section 18 and a central recess-forming portion 19 having a hole 21 at its centre. As can be seen from Figure 4, the lamp 13 extends through the hole 21 so that the filament 22 of the lamp is positioned approximately at the focus of the outer surface of the recess 19 which is of an approximately parabolic shape.

In the example being described, the end wall 15 which is of aluminium has its lower surface anodised in a pale gold colour so that it is reflective over its whole surface and the recess 19 thus serves without further processing as the reflector for the lamp and the outer conical or domed portion 18 provides an aesthetically pleasing appearance. However it will be appreciated that provided that the recess 19 has the necessary reflectance it may be of other colours and the domed or conical annular portion 18 may be of any colour that is required for the purposes of decor.

Since the end wall is of metal it acts as a heat sink to dissipate heat generated by the lamp. If it should prove necessary, a metal plate may be attached to the lower surface of the intermediate transverse wall 11 to act as an additional heat sink and as a shield to prevent excessive heat being transferred to the electronic circuit within the upper portion 3 of the unit.

It will be seen that the invention provides an extremely effective and economical replacement for a standard spotlight of which the filament operates at mains voltage, utilizing a lamp which operates at low voltage with the advantages that may be attributed thereto. The unit has an end wall which provides a reflector for the lamp and thus makes it possible to utilize a relatively cheap and reliable lamp without an integral reflector. The unit may be designed to be of relatively low weight and may therefore be used to replace existing spotlights operating at mains voltage without modification of the sockets, socket supports and surrounds.

Claims (6)

Claims:

1. A spotlight comprising a cap to be received in a standard electrical socket outlet, a generally conical housing1 electrical transformer means located in the narrower portion of the housing, a lamp mounting located intermediate the ends of the housing, and an end wall extending across the wider end of the housing, the end wall having a recess with a hole at the bottom of the recess, the lamp mounting and the recess being arranged so that a low voltage reflectorless lamp mounted in the mounting protrudes through the hole into the recess, the surface of the recess being shaped to provide a reflector for the lamp.

2. A spotlight as claimed in Claim 1 in which the broader portion of the housing is of plastics material.

3. A spotlight as claimed in Claim 1 or Claim 2 in which the end wall is of metal.

4. A spotlight as claimed in Claim 1 or Claim 2 or Claim 3 in which the broader portion of the housing comprises a plurality of spaced rings and bridges interconnecting the rings.

5. A spotlight as claimed in any of the preceding claims in which the recess is surrounded by an annulus which is domed away from the cap end of the spotlight.

6. A spotlight substantially as described herein with reference to Figures 1 to 4 of the accompanying drawings.