SKARVFOERBAND VID BERGBORRUTRUSTNING.

摘要

An extension coupling for rock drilling equipment comprises a coupling rod (1) having a screw-threaded portion (3) with an outer thread whose diameter is smaller than the diameter of the non-threaded portion (6) of the rod, and a sleeve-like part (2) with a portion (4) having an internal screw-thread which corresponds to the outer screw-thread of the rod. The screw-like part (2) includes an extension (5) in the form of a plain skirt-like part which extends from the screw-threaded portion (4) of the sleeve-like part to the outer end thereof and which embraces a part (6) of the plain portion of the coupling rod. The skirt (5) according to the invention provides a supporting effect which reduces the occurrence of bending stresses on the coupling.