Abstract: The invention relates to the geometry of drill bits for jet assisted rotary drilling. According to the invention there is used a drill bit comprising platelets of small radial dimension disposed about a central burster in a discontinuous peripheral crown axially extending said drill bit, channels for supplying pressurized fluid opening from the crown close to the platelets. Said platelets are preferably separated from one another by rectilinear discharge ramps. A drill bit in accordance with this invention can be manufactured e.g. by turning or milling. It can be applied for drilling rock formations in mines, and other hard materials.

Abstract: A rotary drilling bit is provided which includes means for providing a protective stream of a high pressure fluid for its cutting edges fed parallel to the drilling axis directed perpendicular to the cutting edges. The drilling bit also includes means for providing a stream of low pressure fluid for flushing away pulverized rock cut by the drilling bit. The drilling bit is mounted on the end of boring tubing made up of a pair of coaxially positioned tubings, the innermost one supplies the high pressure fluid and the outermost one supplies the low pressure fluid. A drilling process which employs the drilling bit and boring tubing efficiently drills through both soft and non-abrasive rock and hard or abrasive rock.

Abstract: The invention relates to a device for the preparation and injection of sealing cement for bolts in propping gallery roofs and walls in mines, quarries or tunnels. The device of the invention comprises a flexible pouch contained in a rigid housing which is connected to a liquid supply system and an injection nozzle that is double-walled along its entire length, the inner nozzle receiving pulverulent cement from the flexible pouch and the outer ring of the nozzle being supplied with water. Thus, the cement and water are separately introduced into a bore for the bolts and the mixing process takes place in the bore.