GB2239307A

GB2239307A - Improvements in or relating to light fittings

Info

Publication number: GB2239307A
Application number: GB9025447A
Authority: GB
Inventors: Michael Gallagher
Original assignee: LIGHT PROJECTS Ltd
Current assignee: LIGHT PROJECTS Ltd
Priority date: 1989-12-18
Filing date: 1990-11-22
Publication date: 1991-06-26
Anticipated expiration: 2010-11-22
Also published as: GB2239307B; GB9025447D0; GB8928479D0

Abstract

The invention provides a light fitting comprising a housing for an electric lamp and a removable protective cover 11 for a light emitting face of the housing, in which a magnetic housing surface 14 is provided on the housing around that light emitting face, and the cover is provided with a corresponding magnetic cover surface 19 arranged to engage the housing surface when the cover is in place on the housing, in which one of said housing surface of said cover surface is magnetised to retain the cover on the housing. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO LIGHT FITTINGS This invention relates to light fittings, particularly but not exclusively light fittings of the type designed to be fitted flush in a ceiling or ceiling panel and to illuminate downwardly.

Such light fittings are usually mounted in the structure of a ceiling or false ceiling, and in many applications such as in hospitals or kitchens they are required to be protected by a transparent cover. Such a cover often needs to be sealed to the light fitting to prevent the ingress of dust or moisture during use or cleaning. In the present arrangement of such fittings, the attachment ot the cover to the basic light fitting has presented problems, in that the cover needs to be removable for access to the flitting, for instance to change a bulb when it is faulty. Previous arrangements have had covers which are attached by the means of screws requiring the use of tools to remove the cover with ensuing inconvenience.

It is an object of the present invention to provide an arrangement of such a light fitting with a cover which alleviates the problem of such prior arrangements.

Accordingly, the present invention provides a Iiqht fitting comprising a housing for an electric lamp and a removable protective cover for a light emitting tace ot the housing, in which a magnetic housing surface is provided on the housinq around that light emitting face, and the cover is provided wit a corresponding magnetic cover surface arranged to engaqe the housing surface when the cover is in place on the housing, in which one of said housing surface or said cover surface is magnetised to retain the cover on the housing.

Preferably the housing surface and the cover surface are both magnetised.

Preferably the housing surface and the cover surtace are both magnetised with a similar pattern of north and south poles disposed around their periphery so that they attract one another in one angular relationship to retain the cover and repel one another in a second relationsnip to release the cover.

Preferably, the housing surface and/or the cover surface is formed from synthetic plastics material impregnated with permanently magnetised magnetic material.

Preferably, such plastics material is nylon.

Preferably, such magnetic material is strontium ferrite.

In order to promote a fuller understanding of the above, and other aspects, of the present invention, an embodiment will now be descrlbed, by way of examDle only, with reference to the accompanying drawings in which: Figure 1 is a schematic perspectlve view of a lamp housing with a protective cover thereon, Figure 2 is a part cross-sectional view taken on the axis of the housing of Figure 1. and Figure 3 is a part cross-sectional view, similar to Figure 2, of a modified embodiment of the invention.

The drawings show a housing for a lamp witting ot the type to be flush fltted in a celllng or ceiling panel to illuminate downwardly. The housing comprises, as shown in Figure 1, a body 10 which is arranged to be mounted in a ceiling in known manner per se, and to support therein with a suitable lamp holder, an electric lamp, in known manner per se. The housing 10 is provided with a protective cover 11 which is positioned over the light emitting face of the housing, which is the lower face when in use. The cover 11 is provided with a glass window 12 throuqh which light from the electric lamp in the housing may pass.

The housing 10 is formed with a flange 13 to provide a housing surface 14 around the light ? face, which is covered by a seal in the form of an annular layer of silicon rubber 15. At least the flange 13 of the housing is formed of magnetic material. The cover 11 is formed with a rim 16 which extends downwards, in the drawings (upwards when in use), to closely enclose the rim of the flange 13. The cover turther includes an inner shield member 17 for the lamp, which also serves to hold the window 12 in the cover 11, and which includes a flange 18 extending outwardly under the wall of the cover over the flange 13. A seal engaging member 19 provides a cover surface 19a around the cover, is attached to the flange 18 and positioned to engage, and seal on, the silicon rubber layer 15 on the sealing surface 14.The seal engaging member 19 is formed as an annulus of Nylon 6 material impregnated with magnetised material ln the form of strontium ferrite particles.

In the injection moulding of the member 19, the magnetic particles are arranged to form a permanent magnetic structure having, in the arrangement shown, eight substantially equally spaced like magnetic poles on respective faces. In an alternative arrangement, the member 19 may be formed to have a sinqle pole distributed around each face.

As it can be seen with this arrangement, the magnetic seal engaging member 19 will serve a dual purpose. Firstly, it retains the cover 11 firmly on the housing 10 with the cover surface 19a engaging the housing surface 14 through the intermediary of the seal 55, and secondly, it seals against the sealing surface and seals the cover effectively to the housing 10. Since the magnetic member is active around the whole circumference of the cover, the seal is thus effective around the whole circumference. Further, it can be seen that the cover 10 may be simply removed by pulling it with suiticient force to overcome the magnetic attraction, and may equally easily be replaced simply by positioning it on the cover so that the magnetic attraction may again retain it.

While in the above discussion the seal engaging member 19 is shown attached to the cover and the seal surface with the silicon rubber layer is shown as part of the nousing 10; the alternative arranqement may be provided, in which the seal engaging member 1U is on the housing providing the housing surface, and the cover surface is provided by the flange 18 which may leave a seal layer on it similar to that shown at 15.

Preferably, the housing 1O, the cover li. and the shield 17 are formed of terromagnetlc material such as steel, and it will be noted that the arrangement with the rim 16 closely approaching the edge of the flange 13 provides a substantially ciosed magnetic circuit to enhance the effectiveness of the magnetic attraction.

In an alternative arrangement, which is shown in Fiqure 3, both the housing and the cover surfaces 14 and 19a are provided by respective annuli of magnetic material 20 and 21 attached respectively to the housing flange 13 and the cover flange 18. The annuli 20 and 21 are preferably both formed, similarly to the seal engaging member 19 of the previously descrlbed embodiment, from nylon impregnated with magnetic material in the form of strontium ferrite particles.

The annuli 20 and 21 are preferably magnetised so that they each have a similar pattern of north and south poles disposed around their periphery, so that in one angular relationship between the cover and the housing, opposite poles on the annuli attract one another to retain the cover on the housing; while in another angular relationship, the poles on the annuli repel one another to release the cover.

Thus the cover may be released or retained on the housing by twisting it between these two angular positions.

Preferably the annuli 20 and 21 are of rectangular crosssectlon, the housing and cover surfaces provided by them may engage and another axially as shown. In a further arrangement (not shown), the housing and cover surfaces may be provided one on the inner periphery of one annulus and the other an outer periphery of the other annulus to engage one another radially when the cover is on the housing.

In the arrangement discussed with regard to Figure 3, the annuli can seal against one another without the intermediary of a seal, such as that shown at 15 in Figures 1 and 2 bering formed by nylon material.

Claims

1. A light fitting comprising a housing for an electric lamp and a removable protective cover for a light emitting face of the housing, in which a magnetic housing surface is provided on the housing around that light emitting face, and the cover is provided with a corresponding magnetic cover surface arranged to engage the housing surface when the cover is in place on the housing, in which one of said housing surface or said cover surface is magnetised to retain the cover on the housing.

2. A light fitting as claimed in Claim 1, in which both said housing surface and said cover surface are so magnetised.

3. A light fitting as claimed in Claim 1 or 2, in which said housing surface and/or said cover surface are formed by a respective surface of an annulus of magnetic material.

4. A light fitting as claimed in Claim 3, in which each said annulus is of rectangular cross-section.

5. A light fitting as claimed in Claim 3 or 4, in which said surfaces are both formed on such annuli and engage axially when the cover is in position.

6. A light fitting as claimed in Claim 3 or 4, in which said surfaces are both formed on such annuli and engage radially when the cover is in position.

7. A light fitting as claimed in Claim 5 or 6, in which said annuli are both magnetised with a similar pattern of north and south poles disposed around their periphery so that they attract one another in one angular relationship to retain the cover and repel one another in a second angular relationship to release the cover.

8. A light fitting as claimed in Claim 1, in which one of said housing and said cover surfaces is provided with a seal thereon, and the other is formed on a seal engaging member.

9. A light fitting as claimed in Claim 8, in welch said seal comprises a layer of silicon rubber.

10. A light fitting as claimed in Claim 8 or 9, in which said seal engaging member is an annulus of magnetic material.

11. A light fitting as claimed in Claim 8, 9 or 10, in which said seal engaging member is magnetised.

12. A light fitting as claimed in any preceding Claim, in which said housing surface and/or said cover surface is or are formed of synthetic plastics material lmpregnatea with particles of permenantly magnetised material.

13. A light fitting as claimed in Claim 12, in which said plastics material is nylon.

14. A light fitting as claimed in Claim 12 or 13, in wflich said magnetised material is strontium ferrite.

15. A light fitting substantially as herein descrlbed with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.