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able for use in harsh chemical and/or physical environments. Traditionally, these seals have an energiser ring made from stainless steel. However, there are disadvantages to such an arrangement. Making the band in the required shape and configuration, within the desired tolerances, can be difficult. In addition, the band can be difficult to fit, and requires skilled fitters and specialist, dedicated tooling. The band described in this patent includes one or more plastics materials. The material from which it is made, includes at least 80% -preferably 90% -of a plastics material by weight. In some arrangements, it is preferred that the band is made mostly of plastics material, for example, only an engineering plastics material. Compared with a band made from stainless steel it offers a number of advantages. For instance, dimensional accuracy can be improved. The band may be formed by moulding or machining -techniques that may give rise to a more uniform shape and/or configuration than is possible for one made from steel. Problems relating to shape, associated with welding steel bands, also can be reduced or avoided, as can those related to fitting such a band. In addition, the cost of manufacturing a large number of the bands is relatively low.
π SIMILAR VOLUMES
A high aspect ratio seal is provided for a large, roller cone drill-bit. It