GB2028482A - A Light Diffuser Fitting for a Lamp Assembly and a Lamp Assembly which includes such a Fitting - Google Patents

Abstract

A light diffuser fitting (1) for a lamp assembly has a central portion (2) and legs (3) peripherally spaced around and extending radially from the central portion. Each leg (3) is of a non-rectilinear configuration, such as "S", "C", "V", "W" or "Z" shape, and is formed in flexible plastics material to be capable of radial compression so that the overall diameter of the fitting can be reduced to fit within different sized apertures in a lamp housing. The legs 3 can be integral with or attached to the central portion (2); alternatively the central portion (2) can be assembled from several leg members each of which has a part length corresponding to the leg portion (3). <IMAGE>

Description

SPECIFICATION A Light Diffuser Fitting for a Lamp Assembly and a Lamp Assembly which includes such a Fitting This invention relates to a light diffuser fitting for a lamp assembly and to a lamp assembly which includes such a fitting.

According to the present invention there is provided a light diffuser fitting for a lamp assembly and which comprises a central portion and leg portions peripherally spaced around and extending generally radially outwardly from said central portion, each said leg portion over its radial extent being of a non-rectilinear configuration and said leg portions being formed in flexible plastics material to be capable of radial compression in response to manual pressure applied radially inwardly to the outer ends of said leg portions whereby the effective radial extent of the leg portions can be contracted for assembly of the fitting in a housing of a lamp assembly.

Further according to the present invention there is provided a lamp assembly which includes a light diffuser fitting as specified in the immediately preceding paragraph and in which the fitting is mounted within, or to extend over, an aperture in a lamp housing of the assembly with the radially-outer end regions of the leg portions engaging with the lamp housing by the biasing reaction of the leg portions which are maintained in a contracted condition by their engagement with the housing.

In a known construction a light diffuser fitting is formed in plastics material by an array of radially spaced and concentric plastics rings which are interconnected together, substantially in a common plane, by peripherally spaced and radially extending plastics struts. Such a known diffuser fitting is usually mounted within a circular aperture of a lamp housing, reflector bowl or lamp shade (which, conveniently, will be collectively referred to herein as a "lamp housing") by the radially outer ends of the struts or the largest diameter ring engaging with appropriate retaining means on the lamp housing. Consequentiy various diameters of these known fittings have to be provided for mounting within different diameters of apertures in lamp housings.Diffuser fittings of the aforementioned known construction are generally produced by injection moulding and to provide the various diameters of such fitting it is common for one or more of the outermost rings (and outermost part lengths of the struts) to be cut away to provide the required diameter where this is less than the overall diameter of the fitting as moulded - this of course is a time consuming and expensive procedure. Alternatively it has been proposed to blank-off portions of the moulding cavity in the moulding tool so that different overall diameters of fittings can be produced from a single tool but this has the disadvantage that the moulding tool is of a somewhat complicated and expensive construction.The light diffuser fitting of the present invention alleviates the disadvantages of the aforementioned known fitting in that, within predetermined limits, the leg portions can be contracted radially from their normal unstressed, as moulded, condition as necessary for the fitting to be mounted within or over different sized apertures of lamp housings.

Usually the leg portions of the fitting in accordance with the present invention will extend radially outwardly of the central portion in a plane which, in general, may be regarded as common to all of the leg portions. Preferably the nonrectilinear configuration of the leg portions is moulded into those portions to be apparent when the fitting is viewed in a direction normal to the aforementioned common plane.

The non-rectilinear configuration of one or more of the leg portions can be, or comprise, a fair curved part length of such portions; such fair curve can, for example, be a single curve such as a "C" shape or a double curve suoh as an "S" shape. Alternatively or in addition the nonrectilinear configuration of one or more of the leg portions can be, or comprise, part lengths of angular structure, such as a "V", "W" or "Z" shape.

For convenience of assembling the diffuser fitting with a lamp housing and also for aesthetic purposes it is preferred that the non-rectilinear parts of the leg portions are similarly orientated with respect to the central portion. It will be appreciated however that leg portions of different configuration and orientation can be provided in the same fitting, for example a fitting may be provided with one leg portion of substantially "C" shape while the leg portion which is peripherally adjacent thereto may be in the shape of a relatively laterally inverted "C" (whereby the radially outer ends of those two leg portions may be closely adjacent to each other and, in fact, can be joined together so that they present a "petallike" appearance).

Usually the light diffuser fitting will have its leg portions moulded so that the radially outer ends of such portions are located on the circumference of a notional circle while the central portion is located at the central region of such notional circle.

Generally the fitting will be injection moulded as an integral unit although it is envisaged that the leg portions can be moulded separately and subsequently assembled to produce the fitting.

On this latter point each leg portion can be attached to a separately formed central portion, for example, by adhesive or mechanical interlocking techniques; alternatively a kit of separately moulded leg members can be provided which interlock together so that, when secured in interlocking relationship, part lengths of such members form the central portion of the fitting and part lengths form the leg portions.

The leg portions are preferably of blade or lathlike form whereby the length of each portion is considerably greater than its width and its width is considerably greater than its thickness.

Furthermore, the width of each leg portion can vary over the length, for example the leg can be of a tapering configuration whereby the width reduces from the central portion to the radially outer region of the leg portion. The radially outer regions of the leg portions will usually be provided with attachment means such as rebates, recesses or projections by which the fitting is intended to be secured, conveniently by the biasing effect exerted by the leg portions when under radial compression, in a lamp housing.

Examples of plastics material suitable for injection moulding the flexible leg portions (either separately or as an integral part of the fitting) are high density polythene and styrene.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings, in which: Figure 1 is a plan view of a light diffuser fitting in accordance with the invention, and produced as an integral unit in plastics material by injection moulding; Figure 2 is a side elevation of the fitting shown in Figure 1 when assembled with a lamp housing to provide a lamp assembly in accordance with the invention, and Figure 3 is a perspective view of a leg member from several of which a fitting in accordance with the invention can be assembled.

The light diffuser fitting 1 shown in Figure 1 is injection moulded as an integral unit in translucent plastics material such as high density polythene or styrene and has a central portion 2 and six leg portions 3. The central portion 2 is generally in the form of a short cylindrical tube around which the leg portions 3 are peripherally and evenly spaced. The leg portions 3 extend radially outwardly from the central portion and, as will be seen from Figure 2, are located in a common plane which extends perpendicularly to the axis of the central portion 2. Again, as will be seen from Figure 2, each leg portion 3 has a blade or lath-like form whereby its length is considerably greater than its width (the latter being measured in the axial direction of the central portion) and its width is considerably greater than its thickness.From Figure 2 it will be seen that each leg portion 3 is tapered whereby its width reduces from the central portion 2 to its radially outer end region while the uppermost side edges of the leg portions as seen in Figure 2 are co-planar.

In accordance with the present invention each leg portion 3 is of a non-rectilinear configuration over its radial extent and in the illustrated embodiment this configuration is of substantially "S" shape as shown in the plan view of the fitting in Figure 1. In providing the "S" shaped configuration for the leg portions 3, the radially inner end of each leg portion extends substantially tangentially with respect to the outer peripheral surface of the central portion 2 and the radially outer ends of the leg portions are substantially located on a notional circle which is concentric -with the cylindrical centre portion 2.By the fitting being moulded with the relatively thin blade-like leg portions of "S" configuration, each leg portion is capable of flexing radially inwardly relative to the central portion and from its unstressed condition as moulded so that the overall diameter of the moulded fitting as shown in Figure 1 can, within predetermined limits, be reduced by applying manual pressure radially inwardly to the outer ends of the leg portions upon assembly of the fitting with a lamp housing to form a lamp assembly (so that each of the double curves in the "S" shape is progressively tightened in response to the radially inward pressure).

Figure 2 shows a lamp assembly which includes the fitting of Figure 1 whereby the fitting 1 is located within a circular aperture 4 of a lamp housing in the form of a domestic lamp shade 5.

The diameter of the aperture 4 is not greater than the overall diameter of the diffuser fitting as seen in Figure 1 and can be considerably less than the diameter of the diffuser fitting whereby upon insertion of the fitting 1 into the lamp shade 5 the leg portions 3 are radially compressed as aforementioned from their unstressed condition and are retained in such a compressed state by the wall of the shade 5. The radially outward pressure exerted by the flexed leg portions 3 against the inner surface of the lamp shade 5 will assist in retaining the diffuser fitting within the lamp shade.Generally however the radially outer end regions of the leg portions 3 will be shaped to mate with a complementary projection or recess provided on the internal surface of the lamp shade 5; in Figure 2 the inner surface of the lamp shade 5 carries an annular rib 6 which engages with substantially complementary recesses 7 provided on the outer ends of the leg portions 3 and such engagement will usually be maintained by the spring biasing effect of the flexed leg portions.

Other than an integrally moulded plastics unit as above described, the light diffuser fitting can be constructed as an assembly, for example from a plurality of leg members such as that shown at 8 in Figure 3. The leg member 8 can be injection moulded in a similar plastics material to the fitting 1 and has a general overall shape and configuration which is similar to a leg portion 3 as above described. One end part length 9 of the leg member 8 is intended to form part of the central portion of the light diffuser fitting while the remaining part length of the leg member corresponds to the leg portion 3 as previously discussed (so that the radially outer end of this portion is provided with a projection 10 which wil eventually serve to secure the diffuser fitting in a lamp housing by mating with a recess in such housing in a converse manner to the engaging rib and recess shown at 6 and 7 in Figure 2.

Extending from what may be regarded as the radially inner end edge of the leg member 8 and spaced along the width of the leg member are two studs 11. Radially spaced along the leg member from the studs 11 and within the part length 9 are two slots 1 2 which are spaced widthwise of the leg member and are substantially complementary one with each stud 11. To assemble a light diffuser fitting from the leg members 8, for example six such leg members are provided which are arranged in a star wheel configuration similar to that shown in Figure 1 and the studs 11 of each leg member are located and retained, conveniently adhesively, within the slotted apertures 1 2 of the adjacent leg member in the peripheral array. Consequently, a tubular central portion is provided for the fitting by construction from the six part length portions 9 of the leg members and such central portion will have a generally hexagonal configuration in a plan view of the fitting similar to that shown in Figure 1.

Claims (15)

Claims

1. A light diffuser fitting for a lamp assembly and which comprises a central portion and leg portions peripherally spaced around and extending generally radially outwardly from said central portion, each said leg portion over its radial extent being of a non-rectilinear configuration and said leg portions being formed in flexible plastics material to be capable of radial compression in response to manual pressure applied radially inwardly to the outer ends of said leg portions whereby the effective radial extent of the leg portions can be contracted for assembly of the fitting in a housing of a lamp assembly.

2. A fitting as claimed in claim 1 in which the leg portions extend radially outwardly of the central portion substantially in a common plane.

3. A fitting as claimed in claim 2 in which the non-rectilinear configuration of the leg portions is apparent when said portions are viewed in a direction normal to the said common plane.

4. A fitting as claimed in any one of the preceding claims in which the non-rectilinear configuration of at least one of the leg portions is, or comprises, a fair curved part length of such portion.

5. A fitting as claimed in claim 4 in which the fair curved part length is substantially of "C" or "S" shape.

6. A fitting as claimed in any one of the preceding claims in which the non-rectilinear configuration of at least one of the leg portions is, or comprises, a part length of angular formation.

7. A fitting as claimed in claim 6 in which the angular formation is substantially of "V", "W" or "Z" shape.

8. Fitting as claimed in any one of the preceding claims in which the non-rectilinear parts of the leg portions are similarly orientated with respect to the central portion.

9. A fitting as claimed in any one of the preceding claims in which the leg portions are in the form of blades or laths whereby the length of each such portion is considerably greater than its width and the width is considerably greater than its thickness.

10. A fitting as claimed in any one of the preceding claims in which the leg portions have at their radially outer end regions attachment means by which the fitting is intended to be secured in a housing of a lamp assembly.

11. A fitting as claimed in any one of the preceding claims which is formed by injection moulding as an integral unit.

12. A fitting as claimed in any one of claims 1 to 10 in which separately moulded leg portions are attached to a separately formed central portion.

13. A fitting as claimed in any one of claims 1 to 10 in which each leg portion is formed of a leg member and several said leg members are assembled together so that the central portion is constructed from part lengths of each such leg member.

14. A light diffuser fitting for a lamp assembly substantially as herein described with reference to Figures 1 and 2 or with reference to Figure 3 of the accompanying illustrative drawings.

15. A lamp assembly which includes a light diffuser fitting as claimed in any one of the preceding claims and in which the fitting is mounted within or to extend over an aperture in a lamp housing of the assembly with the radially outer end regions of the leg portions engaging with the lamp housing by the biasing reaction of the leg portions which are maintained in a contracted condition by the engagement with the housing.