(57) A valve stem seal comprises an elastomeric moulding adapted to lip seal against a
valve stem and, at its lip sealing region, is helically ribbed on its stem-adjacent
surface to define lubricant control passages. The elastomeric moulding also provides
downstream of its lip seal, in terms of lubricant flow, a control collar adapted to
contact the valve stem to provide both a compensation for lateral loading of the valve
stem resulting from rocker action and a secondary seal.
The control collar may be integral with the elastomeric moulding but it is preferred
that it be constituted by a plastics ring, preferably but not exclusively formed of
PTFE, held within the elastomeric moulding in non-bonded relationship.
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