A reverse-circulation drilling assembly having an overshot subassembly and a head subassembly. In the event retrieval of the drilling assembly by reverse-circulation fails, the drilling assembly can be retrieved using a secondary overshot.

The invention relates to a drill head of a ground drilling device having a drill bit and an attachment which can be fastened to the drill bit, wherein at least one dowel pin is provided for holding the attachment on the drill bit, and the drill bit has one or more receptacles for a dowel pin, wherein the receptacle is enlarged with respect to the radius of the dowel pin.

A percussion boring device comprising a casing, a guide tube fixed to the casing, and a control bushing axially displaceable on the guide tube. An impact piston of the device is axially displaceable on the control bushing and configured to be actuated in a reciprocating manner within the casing such that in a first switching position the impact piston strikes a front impact surface to actuate the percussion boring device in a first movement direction, and in a second switching position a rear impact surface to actuate the percussion boring device in a second movement direction. A pressure increasing means is provided and configured to generate a pressure for reversing the percussion bore device, wherein the generated pressure is higher than a pressure for moving the impact piston. The guide tube and the control bushing are configured to reverse movement directions of the impact piston.

A percussion drilling device for drilling in earth includes at least one housing section for a main piston, and a ring insert arranged in the housing section in front of the main piston so that the ring insert transmits at least part of the energy of the main piston onto the housing. The ring insert is attached to the housing by a shrink-fit connection.

A drilling head for a percussive displacement ground drilling device with a first drilling head section and a second drilling head section, the first drilling head section having discharge ducts, and the second drilling head section having a cross section that increases in the longitudinal direction, wherein the second drilling head section includes a plurality of step-shaped areas.

A self-propelled drilling head for drilling in soil by means of a multi-stage method comprises the drilling head having a housing and a drilling head tip arranged in the housing, and a spacer provided on the drilling head tip, by means of which the drilling head tip is in contact with the housing in order to change the multi-stage method to a method with a reduced number of stages.

A drilling head for a percussive displacement ground drilling device with a first drilling head section and a second drilling head section, the first drilling head section having discharge ducts, and the second drilling head section having a cross section that increases in the longitudinal direction, wherein the second drilling head section includes a plurality of step-shaped areas.

A diaphragm wall down-the-hole hammer trenching machine comprises a crane, a guide frame, a push-pull device, cluster down-the-hole hammers, gas collecting hoods, a high-pressure medium pipe or cable, and a slurry discharge pipe. The crane suspends the guide frame; the cluster down-the-hole hammers are connected to the bottom of the guide frame by means of the push-pull device; each cluster down-the-hole hammer comprises a primary hammer and secondary hammers; the plurality of secondary hammers are provided on each primary hammer; one gas collecting hood is provided on the lower part of each primary hammer; the high-pressure medium pipe or cable passes through the guide frame and the push-pull device to enter a primary hammer distribution pipeline to drive the secondary hammers to perform percussive drilling; mud channels are provided in each primary hammer; and the slurry discharge pipe passes through the guide frame and communicates with the gas collecting hoods.

A reverse-circulation drilling assembly having an overshot subassembly and a head subassembly. In the event retrieval of the drilling assembly by reverse-circulation fails, the drilling assembly can be retrieved using a secondary overshot.

A ground drilling device comprising a housing, a lengthwise movable drilling head tip arranged in the housing, and a bearing for supporting the drilling head tip in the housing during its lengthwise movement.