Publication Date: 2005-May-26
The IP.com Prior Art Database
An incandescent lamp gives uniform light over its whole surface. When lenses or other shapes are placed onto the lamp surface the light can be focussed or send in a wanted direction. A sparkling effect is created. The material, used to create the forms, must be transparent and withstand a) the heat of the lamp, b) the UV radiation and c) may not induce cracks in the glass due to stress. A group of materials that meet these specifications are silicone rubbers and silicone resins. The silicone material can be applied directly onto the glass surface or made as a free form and then stretched around the lamp. When a free form is stretched around the glass the intermediate space can be filled with curable silicone rubber.
The greatest problem, when applying lenses or other shapes on the glass surface of a lamp, is the induced stress due to difference in expansion coefficient at the operating temperature. Stress can induce cracks in the glass and malfunction of the lamp. To apply a glass lens on the lamp surface it must be a low melting glass. Many of these low melting glasses contain lead (environmental unfriendly). With conventional techniques it is also hard to make large forms that not introduce large stress. With a silic one rubber none of the stress problems occur. The silicone rubber can withstand temperatures of 250°C for at least the lifetime of the lamp. The cured silicone material is environmental friendly because no fluid silicone oil is present.
For this application an addition-curing silicone rubber or silicone resin can be used. Curing is accelerated at increased temperature. It is also possible to add colour pigments or dyes to the silicone rubber to make a product with coloured layer.
The shape of the forms can be spherical lenses, a-spherical lenses, cubes, pri...