Institut Cerac Sa

Hans Bergkvist

Hans Jaun

A rock drilling apparatus for drilling with high pressure hydraulic jet including a rock drill body (11), a drill tool (12) coupled to said body (11) and a feeding device (15) with a motor (16) for feeding said body and tool to and fro the working face. The drilling tool (12) has an inner rotating tube (40) with a high pressure nozzle body (41) at the nose thereof and an outer tube (42) surrounding said inner tube (40). Said outer tube (42) is provided with a hard metal collar (61) at the front end for protecting the nozzle body (41) and for calibration of the drill hole size. A sensing device including a pressure operated switch 73 and an adjustable time relay (83) is adapted for sensing the feed resistance met by said collar (61) and causing said feed motor (16) to retract said drill body (11) and tool (12) when a preset value of the resistance is exceeded.

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Ecublens, Switzerland

Hans Bergkvist