Composite seal for hydrostatic coupling to percussion drill - involving viscoelastic and rubber components opt. of polyacetal and polyurethane

摘要

A seal for a tapered spigot coupling for the fluid circuit of a percussion drill comprises a combination of a sleeve made of viscoelastic matl. and an annular seal of an abrasion resistant rubber (polyurethane). The viscoelastic matl. can deform to fit between the spigot and a conic socket seat, utilising local hydrostatic pressures to sustain the rubber seal in place. Pref. both spigot and socket have annular lands which limit hydrostatic extrusion of the viscoelastic sleeve. Opt. the sleeve is made of polyacetal.