Abstract: The impact hammer comprises a working piston (22) exerting impacts onto an impact surface (23). The hydraulically driven working piston (22) is reciprocatingly controlled by a control means (40,41). At the rearward end of the working cylinder (21), there is a rear chamber (50) into which the projection of the piston (51) immerses. Connected to the rear chamber (50) is a pressure gas reservoir (52) which is charged with each return stroke of the working piston and discharges with the subsequent working stroke.

Abstract: Mounted on a vehicle (10), the mast (20) of a boring rig is supported by an erection hinge (18). The erection hinge (18) is provided on a first carriage (19) having a support cylinder attached (28) to it for the purpose of support and erection of the mast (20). The hydraulic erection cylinder (24), attached to the vehicle (10), is connected to the second carriage (21). The mast (20) is extended to an oblique angle by the hydraulic erection cylinder (24). The final phase of the erection of the mast (20) is completed by the retraction of the secondary take-in cylinder (27), which connects the two carriages together. When in a horizontal position, the mast (20) can be guided in a longitudinal direction in order to have a more favorable position of the center of gravity on the vehicle (10).

Abstract: A hydraulic base-load motor (M1) drives a load with the working pressure generated at the motor rising with the load. When the working pressure reaches an upper limit pressure, a hydraulic stand-by motor (M2) is switched on. Since the pressure drops upon switching on the stand-by motor, the control device is designed such that, upon reaching a lower limit pressure, it deactivates the stand-by motor again, the lower limit pressure being less than half the upper limit pressure. This switching hysteresis prevents a repeated switching over of the stand-by motor.

Abstract: The device comprises a solid drill bit (28) and an annular drill bit (40). Axial impacts are exerted on the solid drill bit (28) which are transmitted onto the annular drill bit (40) through impact transmission surfaces. The annular drill bit (40) is freely axially displaceable within limits. It has rearwardly projecting tongues (43) that engage windows (15) of an outer pipe end piece (12). Thus, the movability of the annular drill bit (40) is ensured without any keyings or the like being necessary, which entail the risk of a clogging with bore material. All movable parts are included in the scavenging so that jamming is avoided.