Abstract: An electric cable is provided having a conductor element, and successively around the conductor element an electrically-insulating layer; a metal screen and an outer protective sheath. The cable has an extruded outer layer surrounding the outer protective sheath, the extruded outer layer being directly in contact with the outer protective sheath, and being obtained from a composition containing more than 50.0 parts by weight of apolar polymer per 100 parts by weight of polymer in the composition, together with an electrically-conductive filler.

Abstract: The present invention provides an electric cable comprising a conductor element, and successively around said conductor element: an electrically-insulating layer; a metal screen; and an outer protective sheath; the cable further comprising an extruded outer layer surrounding the outer protective sheath, said extruded outer layer being directly in contact with said outer protective sheath, and being obtained from a composition containing more than 50.0 parts by weight of apolar polymer per 100 parts by weight of polymer in the composition, together with an electrically-conductive filler.

Abstract: In rock drilling utilizing mechanical destruction of the rock and circulation of drilling fluid for removing debris from the cutting face, the drilling fluid is directed on to the cutting face in the form of two opposed pulsed jets, the cycles of which are 180.degree. out of phase. In order to achieve the phased opposition of the pulsed jets a ball is disposed in the distribution chamber of the drilling fluid and is subjected to a combination of hydraulic and mechanical forces which cause the ball to oscillate between two end positions in which the ball respectively closes off one of two outlet ducts leading to nozzles which direct the drilling fluid towards opposite points on the bottom of the drill hole.