GB2123135A - Trimming lampshades - Google Patents

Abstract

A method of trimming lampshades is disclosed which is applicable to lampshades of which the diameter at one end is less than at the other. Problems have been encountered when trimming lampshades with plastics trimming material which is rigid but flexible and substantially j-shaped in cross-section. In order to solve these problems accurately dimensioned endless rings 9, 10 are formed of the trimming material. A ring of trim used for the narrower end of the lampshade is heated to soften the plastics and shaped to conform to the narrower end to which it is subsequently adhered. The ring of trim used for the wider end of the lampshade has a circumferential length slightly less than that of the wider end and is forced over the end. By this means the edges of the rings lie closely adjacent to and follow the line of the lampshade. <IMAGE>

Description

SPECIFICATION Improvements in or relating to lampshades This invention relates to lampshades and is particularly concerned with a method oftrimming lampshades Lampshadesaregenerallyformedwith an upper wire ring joined by spokes to a central attachment ring and a lowerwire ring,with stiffened lampshade material, such as parchment, plastics-reinforced fabric orthe like extending between the rings and secured circumferentially around the upper and lower rings.

Where the upper and lower rings are of substantially the same diameter orthe bottom ring is only slightly larger, the lampshades are sometimes referred to in the trade as "drum shades". Where the diameter of the lower ring is largerthan that ofthe upper by about two or three times, the Iampshades are referred to as "empire shades" and where the diameter of the lower ring is very much largerthan that ofthe upperthe lampshade may be referred to as "coolie shades".

The lampshade material may be joined circumferentiallyto the upper and lower rings by a tape of paper or the like one edge of which lies on the the inside ofthe lampshade and the other edge of which lies on the outside ofthe lampshade. In order to hide the edge of the tape, which may be unsightly, it is usual to apply an exteriortrim to the top and bottom of the lampshade.

Problems arise when attempts are made to use as an exterior trim a material comprising a thin strip of aluminium foil, which may be coloured, extrusioncoated with an ABS-plastics (acrylonitrile - butadiene styrene), the strip being substantially j-shaped in cross-section, and being rigid butflexible. The strip is applied by glueing one end of a length of strip to the end of the lampshade so that the hook ofthej engages overthewire ring. The trim isthen applied byglueing the trim and winding it round the lampshade as tightly as possible until the circle of trim is complete, whereupon the trim is cut and the cut end matched as neatly as possible with the beginning. This operation, like many operations in the manufacture of lampshades is performed by hand.

This method oftrimming issatisfactoryfordrum shades, but is not satisfactory for empire shades and coolieshades. Dueto its inherent stiffness it is impossibleto make the trim material conform to the shape of the lampshade. The resulting rings of trim material present substantially right-cylindrical outer surfaces which spoil the line of the empire or coolie shade. Furthermore,the lower ring tends to stand proud of the lampshade material and form a gutter in which dirt and dust become trapped.

It is an object ofthe invention to rationalise the production of lampshades by the method just outlined and to enable a satisfactory trim to be effected on shades of which the diameteratthe top is less than at the bottom, such as empire shades.

According to the present invention there is provided a method oftrimming a lampshadeofwhichthe diameter at one end is less than at the other, wherein a strip of plastics trimming material, which is rigid but flexible and which is substantially j-shaped in cross section, is cut into a first length, the length of which is substantially exactly the same as the circumferential length of the one end of the lampshade and the ends are joined to form a firstendless ring, the ring then being heated to soften the plastics and shaped on a mandrel shaped in conformity with said one end ofthe lampshade, whereafterthe ring is adhered to the top ofthe lampshade with the hook ofthe j engaging over the one end ofthe lampshade and the remainder splaying out in conformity with the shape of the lampshade, and wherein a second length of said trimming material is cut, the length ofwhich is slightly less th an that of the ci rcu mferential length of the other end of the lampshade, and the ends of joined to form a second endless ring which is then forced overthe other end of the lampshade with the hook ofthe j engaging overthe other end ofthe lampshade.

It is essential that the circumferential extent of the top ring should be substantially exactlythe same as that of the top end of the lampshade. Due to the flexibility ofthe trim material, an undersizetolerance is preferable to an oversize tolerance.

The use of preformed rings of trim material is of particular significance in the trimming of empire shades, because the preformed upper ring can be heat-softened and shaped to conform to the line ofthe lampshade so that when finally adhered in place, it does not present a right-cylindrical outer surface but a conical one. The lower ring is undersized compared with the circumference ofthe end ofthe lampshade and is stretched in the region of the hook of the jas it is placed in position. The ring rests snugly againstthe lampshade material and conforms to the line of the lampshade.The degree of undersize of the ring is determined by the necessity to have the ring as small as possible while still being able to force it into position without undue effort and without breaking it.

In orderforthe ring to lie snugly against the lampshade material for empire shades, experiments have shown that the circumferential length of the ring should be about 0.2% less than the circumferential length of the base of the lampshade.

When making the preformed rings oftrim material, it is preferred to make a mitre cut and to join the two ends by solvent-welding using a solution of the plastics in a volatile solvent. This is effected using a mitreing and measuring jig in orderto achieve the accuracy required in the length of trim material.

In orderto enable the invention to be more readily understood, referencewill now be madetothe accompanying drawing, which illustrates diagramati cally and byway of example an embodimentthereof, and which is a schematic cross-section through a lampshade of the empire type.

Referring now to the drawing, there is shown an empire lampshade comprising an upperwire ring 1 joined by spokes 2 to a central ring 3 by which the lampshade may be attached to a light fitting, and a lower wire ring 4 of larger diameter than the upper ring 1. Lampshade material 5, which may be parchment, fabric-covered plastics material or other conventional lampshade material, extends between the rings to form the frusto-conical lampshade shown.

The lampshade material 5 is adhesively secured to the rings by a tape 6 of paper, plastics orthe like. One edge 7 of the tape is secured inside the lampshade, the tape passes around the respective ring, and the other edge 8 is secured to the outside ofthe lampshade. The outside edge 8 ofthetape may be unsightly, since the tape material may be of different texture or colourto those ofthe lampshade material, the edge ofthe tape maybe uneven, orthetape may be otherwise unsuitablefortrimmingtheedgesofthe lampshade. It is therefore usual to apply a trim to the edges ofthe lampshade and this presents no problems where the trim is fabric.

However,onetrim material used in the manufacture of lampshades comprises a j-section flexible strip comprising aluminium foil extrusion-coated with ABS-plastics. The aluminium foil may be coloured or decorated and the strip is capable of providing an attractive finish to a lampshade while at the same time reinforcing the ends ofthe shade. As indicated above, however, this trim material can only be used satisfactorilywith drumshadesand not with empire shades.

In orderto be ableto trim an empire shade with this trim material, a first length of the material is cut, the length being carefully measured so that it is substan tially exactly the same as the circumference of the lampshade at the upper ring 1. The cut is preferably a mitre cut and the cut ends are joined preferably by solvent-welding using a solution of ABS-plastics in acetone, the cut ends being held together until the acetone has evaporated. The resuiting ring is then heated to a temperaturesufficienttosoftenthe plastics but not sufficient to cause it to flow on a mandrel which is shaped to conform to the upper end ofthe lampshade so thatthe ring assumes the shape as the ring 9 in the drawing.It is convenientto heat the mandrel and place the ring on the mandrel to effect softening but it is also possible to heat the ring separately and then place it on the mandrel. When it has cooled,the ring is removed from the mandrel, adhesive is placed in the hook of the j and the ring is placed in position as shown. In practice, it may be convenientto up-end the ring and lampshade, place a weight on what is normally the underside of the ring 3 and allowthe lampshadeto stand until the adhesive has set.

In order to provide a bottom trim a second length of trim material is cut and formed into a ring 10 in the same manner as before. However, the length of trim is carefully selected such that the diameter ofthe resulting ring is slightly less than that of the lampshade atthe ring 4. This ring 10 is not heated but is then forced into the bottom ofthe lampshade in a manner similar to fitting a tyre onto a bicycle wheel.

By forming the rings 9 and 10 in this mannerthe free edges ofthe rings remote from the hook of the j lie closelyadjacentto andfollowthe lineofthe lampshade, so that an attractive effect is obtained.

It has been ascertained by experiment that good resultsforan empire shade are obtained if the circumferential length ofthe ring 10is O.2% lessthan the circumferential length ofthe base ofthe lampshade. Although it into be appreciated thatthis relationship may vary slightly in dependence upon the trim material and other factors.

In orderto ensurethatthetop and bottom rings 9 and lOarecuttothe required length accurately, the trim material is cut in a mitreing and measuring jig and the cut ends are carefully joined to maintain the required degree of accuracy.

Claims (8)

1. A method oftrimming a lampshadeofwhich the diameter at one end is less than at the other, wherein a strip of plastics trimming material, which is rigid but flexible and which is substantiallyj-shaped in crosssection, is cut into a first length, the length of which is substantially exactlythe same as the circumferential length of the one end of the lampshade and the ends are joined to form a first endless ring, the ring then being heated to soften the plastics and shaped on a mandrel shaped in conformity with said one end ofthe lampshade, whereafterthe ring is adhered to the top ofthe lampshadewiththe hookofthe j engaging over the one end of the lampshade and the remainder splaying out in conformity with the shade ofthe lampshade, and wherein a second length of said trimming material is cut, the length of which is slightly less than that of the circumferential length of the other end ofthe lampshade, and the ends are joined to form a second endless ring which is then forced over the other end of the lampshade with the hook of the j engaging overthe other end of the lampshade.

2. A method as claimed in Claim 1, wherein the mandrel is heated and the first endless ring is placed on the mandrel to soften and shape it.

3. A method as claimed in Claim 1, wherein the first endless ring is heated ahd placed in the mandrel to shape it.

4. A method as claimed in any preceding Claim, wherein the lengths of trimming material are cut in a mitreing and measuring jig and the cut ends are carefully joined to maintain the required degree of accuracy.

5. A method as claimed in any preceding Claim, wherein the cut ends of the lengths oftrimming material are joined bysolventwelding.

6. A method as claimed in any preceding Claim, wherein the lampshade is an empire shade and the circumferential length of the second endless ring is about 0.2% less than the circumferential length of the other end ofthe lampshade.

7. A method oftrimming a iampshade of which the diameter at one end is less than at the other substantially as hereinbefore described with reference to the accompanying drawing.

8. A lampshade of which the diameter at one end islessthanattheothertrimmed bythemethod claimed in any preceding Claim.