Rotary drilling swivel - with inner sleeve sliding for hard and locked for soft rock drilling

摘要

A swivel for a rotary drilling of the reverse flushing type transmits the thrust from a hydraulically operated cross-piece to the string of the drill tubes and the roller bit by two rolling friction bearings between an inner and an outer sleeve. The inner sleeve is divided into two which can axially slide relative to each other in keyways. The axial clearance is taken up by a split spacer ring only when drilling in soft strata; in that case the thrust is transmitted to the lower bearing. This allows the same swivel to be used for hard rock as well as soft strata by a simple addition of a sheet clamp ring. In hard rock the bearings are relieved of large upward thrust, so that the bearing life is lengthened.