Abstract: The hydraulic rotary-percussive hammer drill includes a fluid injection portion including a fluid feed-in inlet and an annular inner groove fluidly connected to the fluid feed-in inlet; a shank including a fluid injection conduit fluidly connected to the annular inner groove; front and rear main sealing gaskets disposed on either side of the annular inner groove and configured to cooperate with a first shank portion of the shank; a rear backup sealing gasket located at the rear of the rear main sealing gasket and configured to cooperate with a second shank portion of the shank; a leakage passage defined between the shank and the fluid injection portion; pressure drop generation means configured to generate pressure drops in the leakage passage when a leakage flow flows in the leakage passage.

Abstract: A tunnel boring machine for boring a tunnel in rock including: locating means mounted to a frame for supporting and locating the frame in a disposition with respect to a tunnel axis and a boring face of the tunnel being bored; a first boring assembly operatively associated with said frame for boring into an annular face surrounding a core substantially coaxial with the tunnel axis, the annular face being a portion of the boring face; a core removal assembly operatively associated with said frame and disposed axially with respect to said first boring assembly away from the annular face, said core removal assembly being operable for removing at the core exposed by the first boring assembly transverse to the tunnel axis to expose the remainder of the boring face; and drive means operatively associated with said first boring assembly for driving said boring assembly into the annular face.

Abstract: A stop collar for mounting to a downhole tubular includes: a cylindrical housing having a threaded inner surface and a tapered inner surface; a compressible slip ring having teeth formed in an inner surface thereof and a pair of tapered outer surfaces; a compressible cam ring having a tapered inner surface; and a cylindrical bolt having a threaded outer surface. A natural outer diameter of each ring is greater than a minor diameter of the threaded surfaces. Screwing the threaded surfaces of the housing and the bolt is operable to drive the tapered surfaces together, thereby compressing the slip ring such that the teeth engage a periphery of the tubular.

Abstract: The invention relates to a device for assessing the disintegration of a dosage form in the gastrointestinal tract, comprising a wall surrounding a cell for being filled with a fluid and for receiving the dosage form, further comprising a pressurizable compartment arranged exterior to the wall for repeatedly deforming the wall between a first state and a second state wherein the volume of the cell in the first state is larger than in the second state, wherein the device also comprises controlling means for quantitatively controlling a fluid flow from and into the cell, and/or for quantitatively controlling a contact force that the wall exerts on the dosage form.

Abstract: This invention relates to a torque control device for a downhole drilling assembly. The torque control device is adapted for connection to a drill bit, and has an outer sleeve and an inner shaft, the outer sleeve being movable longitudinally relative to the inner shaft. The torque control device also has a cylinder, a piston located within the cylinder, and a controller to control the volume of the cylinder. Changing the volume of the cylinder causes relative longitudinal movement between the outer sleeve and the inner shaft. The controller can receive inputs from a torque sensor and/or an accelerometer in order to determine if a threshold torque has been exceeded. Alternatively the controller can comprise a rotary valve which automatically responds to torque in the assembly.

Abstract: Methods and apparatus are described to drill and complete wellbores. Such wellbores include extended reach horizontal wellbores, for example in shales, deep subsea extended reach wellbores, and multilateral wellbores. Specifically, the invention provides simple threaded subassemblies that are added to existing threaded tubular drilling and completion equipment which are used to dramatically increase the lateral reach using that existing on-site equipment. These subassemblies extract power from downward flowing clean mud, or other fluids, in an annulus to provide additional force or torque on tubular elements within the wellbore, while maintaining circulation, to extend the lateral reach of the drilling equipment and completion equipment. These added elements include combinations of The Leaky Seal™, a Cross-Over, The Force Sub™ and The Torque Sub™. The use of such additional simple elements allow lighter drilling equipment to be used to reach a given lateral distance, therefore reducing drilling costs.

Abstract: A tunneling system is disclosed that includes a surface power-controller, umbilical tether, robotic tender, and robotic tunneling device. This system allows the robotic tunneling device to efficiently create new tunnels using the power and fluids provided from the surface through the robotic drilling tender, as well as a way to efficiently manage cuttings below surface. The system is designed to operate not only when the well is not producing, but also on a continuous basis while the well is producing.

Abstract: A rig for drilling a borehole from an underground tunnel includes a base assembly, a drilling assembly mounted to the base assembly, an upper frame assembly mounted to the drilling assembly above the base assembly, and a support hood coupled to the drilling assembly and positioned above the upper frame assembly. The support hood is configured to bear against a ceiling of the tunnel during drilling operations.

Abstract: A downhole coring tool conveyable within a borehole extending into a subterranean formation, wherein the downhole coring tool comprises a housing, a hollow coring bit extendable from the housing, a first motor operable to rotate the coring bit, and a second motor operable to extend the coring bit into the subterranean formation through a sidewall of the borehole in a direction not substantially parallel to a longitudinal axis of the borehole proximate the downhole coring tool. A static sleeve disposed in but rotationally independent of the coring bit receives a portion of a core sample of the formation resulting from extension of the coring bit into the formation. The static sleeve comprises a protrusion extending radially inward toward the core sample sufficiently to mark the core sample.

Abstract: An apparatus is for use by an operator in forming boreholes in a mine passage including a rib and a roof. The apparatus includes a boom having a proximal end mounted to a base, such as a vehicle. A drill supported by the boom near a distal end thereof is adapted for drilling into the rib of the mine passage. An operator's station carried by the boom adjacent the drill includes a platform for supporting the operator arranged at least partially between a generally vertical plane aligned with the second lateral side and the rib. Accordingly, the operator can access the rib when positioned on the operator's station without interference from the boom.

Abstract: A drilling tool (1) for drilling downhole, comprising a drilling head (2) in connection with a first portion (18) of the drilling tool, a driving unit (9) for driving the drilling head and the first portion forward in a longitudinal movement while drilling, and a feed control (19) for controlling the longitudinal movement of the drilling head.

Abstract: An apparatus for moving tubing through a borehole is disclosed. The apparatus includes a surface injector assembly and a downhole injector assembly with a driving mechanism to move the tubing through the borehole, an anchoring system for securing the downhole injector assembly downhole to a cased portion of a borehole wall and connections for receiving a power supply form the surface. A method of moving tubing through a borehole is also disclosed. The method involves attaching a downhole injector assembly to a cased portion of a borehole wall sufficiently downhole such that the downhole injector assembly can supply weight to a drilling assembly, and injecting tubing through the borehole using the downhole injector assembly.

Abstract: A wireline tractor includes a displacement mechanism and at least one driving wheel positioned on the displacement mechanism so that the driving wheel is held in a biasing manner against a well wall. The displacement mechanism is rotatable or movable between a first position at which the driving wheel bears against the well wall on one side of the wireline tractor, and a second position at which the driving wheel bears against the well wall on the opposite side of the wireline tractor.

Abstract: The method of controlling the load on a drill bit drilling a hole by providing differential pressure across a seal area on a drilling assembly to increase the bit load and providing a relief valve from the annular area above the seal to the bore returning fluid to the surface to limit the maximum differential pressure to limit the maximum load allowed.

Abstract: Disclosed is a novel autonomous excavating apparatus capable of solving conventional problems. The autonomous excavating apparatus comprises an apparatus body including a lower body 101 formed in a cylindrical shape and combined with a conical-shaped lower end, and a spiral blade 102 provided on an outer peripheral surface of the lower body 101 in the form of a right-handed screw. The lower body 101 has an internal space provided with a wheel 103 which has a rotary shaft 104 rotatably supported relative to the lower body 101 through bearings 105, 106. A motor 108 is fixed to the lower body 101 at a position above the wheel 103, and an output shaft of the motor is coaxially connected to the rotary shaft 104. Thus, the motor 108 can drivingly rotate the wheel 103 relative to the lower body 101.

Abstract: A method and apparatus for creating inverted laterals or drainholes for producing from a subterranean reservoir including the steps of lowering, positioning and securing a reverse whipstock in a wellbore. A tube is secured from the surface to a pull tube which extends through and below the reverse whipstock. Fluid is pumped from the surface and through a U-tube device below the pull tube. At least one inverted drainhole is drilled using force from the pumping fluid. The pull tube is pulled upward vertically toward the surface while pumping the fluid.

Abstract: The invention relates to an arrangement designed to be inserted in a cavity (19) in a front part (14) of a rock drilling machine with a shank adapter (16). The arrangement comprises a cartridge (1) with a flushing head (2) and a guide (3) coaxially arranged to create a longitudinal channel (5) designed as a passage for the shank adapter (16).

Abstract: The present invention relates to a drilling tool (1) for drilling downhole, comprising a drilling head (2) in connection with a first portion (18) of the drilling tool, a driving unit (9) for driving the drilling head and the first portion forward in a longitudinal movement while drilling, and a feed control (19) for controlling the longitudinal movement of the drilling head.

Abstract: Drilling tool (1) for drilling a well downhole where fluid is surrounding the tool and where the tool has a housing (15) and is connected to an electrical conducting means, such as a wireline. The drilling tool has a drilling head (2) and a fluid cleaner (3) for removal of elements, such as debris and formation pieces, from the fluid while drilling downhole. The fluid cleaner has a chamber (4) and a filter (5) within the chamber for separation of the elements from the fluid. The tool further comprises a pump (8) for pumping the fluid into the chamber through an inlet (11) in the drilling head (2) and through the filter before entering the well again. Furthermore, the tool comprises a driving unit for driving the pump and the drilling head.

Abstract: A downhole motor to drill a wellbore including a pumping apparatus having a first chamber configured to receive a first fluid and a second fluid, and a first flexible diaphragm disposed with the first chamber configured to separate the first and second fluid, wherein the first flexible diaphragm is configured to transfer a hydraulic energy between the first fluid and the second fluid. In addition, the downhole motor includes a motor portion coupled to the pumping apparatus and configured to receive the second fluid and convert the hydraulic energy of the second fluid into a mechanical energy, thereby creating a torque. Further, the downhole motor includes a bit shaft coupled to the motor portion, configured to receive the torque from the motor portion and the first fluid from the pumping apparatus.

Abstract: An earth boring apparatus for sinking shafts and removing shaft material from the shaft, the apparatus having at least two decks; hydraulic means for allowing movement of the decks relative to one another; releasable anchoring means associated with the decks for engaging walls of the shaft to secure the apparatus in a stationary position; whereby the releasable anchoring means of one of the decks engages the wall while the releasable anchoring means of the other deck is released from the wall to allow motion of the other deck along the shaft, in cooperation with the hydraulic means. The apparatus also includes guide means for forcing a bucket for hoisting shaft material from the shaft along a predetermined path, and an in-stage cut-boom drill.

Abstract: A method and apparatus for propelling a tool having a body within a passage. The tool includes a gripper including at least a gripper portion which can assume a first position that engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface. The gripper portion can also assume a second position that permits substantially free relative movement between the gripper portion and the inner surface of the passage. The tool includes a propulsion assembly for selectively continuously moving the body of the tool with respect to the gripper portion while the gripper portion is in the first position. This allows the tool to move different types of equipment within the passage. For example, the tool advantageously may be used in drilling processes to provide continuous force to a drill bit. This enables the drilling of extended horizontal boreholes.

Abstract: Apparatus, system and methods useful for controlling the traction of a downhole tractor in a borehole include the capability of repeatedly adjusting the normal force applied to at least one component that causes movement of the tractor in the borehole.

Abstract: A method and apparatus for propelling a tool having a body within a passage. The tool includes a gripper including at least a gripper portion which can assume a first position that engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface. The gripper portion can also assume a second position that permits substantially free relative movement between the gripper portion and the inner surface of the passage. The tool includes a propulsion assembly for selectively continuously moving the body of the tool with respect to the gripper portion while the gripper portion is in the first position. This allows the tool to move different types of equipment within the passage. For example, the tool advantageously may be used in drilling processes to provide continuous force to a drill bit. This enables the drilling of extended horizontal boreholes.

Abstract: Apparatus, system and methods useful for controlling the traction of a downhole tractor in a borehole include the capability of repeatedly adjusting the normal force applied to at least one component that causes movement of the tractor in the borehole.

Abstract: A tunneling system including a tunneling apparatus including a cutting structure for forming a borehole and at least one linkage section for transmitting a force generally toward the cutting structure is disclosed. A method of disposing a casing string within a subterranean formation by applying a force generally to the trailing end of the tunneling apparatus, generally toward the leading end thereof, but without transmitting the entire force through the entire casing string is also disclosed. At least one linkage section extending within but not in contact with at least one casing section of the casing string may transmit the force. Also, a force limiting member may limit a force applied to the casing string.

Abstract: A method and apparatus for propelling a tool having a body within a passage. The tool includes a gripper including at least a gripper portion which can assume a first position that engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface. The gripper portion can also assume a second position that permits substantially free relative movement between the gripper portion and the inner surface of the passage. The tool includes a propulsion assembly for selectively continuously moving the body of the tool with respect to the gripper portion while the gripper portion is in the first position. This allows the tool to move different types of equipment within the passage. Preferred uses for the tool include drilling, well completion, logging, retrieval, pipeline service, and communication line activities.

Abstract: A method and apparatus for controlling fluidic torque in a downhole tool is provided. One or more rotatable components of the downhole tool comprise a deformable material, such as rubber or SMA, selectively deformable in response to the flow of fluid through the downhole tool. The rotatable components may include a rotor and/or a turbine of a generator in the downhole tool. Non-rotatable components, such as the stator of the generator, may also be deformable. The rotor, the stator, and/or turbine may comprise a deformable material capable of selectively deforming in response to the flow of drilling mud through the generator. The desired deformation and/or the desired torque may be controlled by adjusting the parameters of the components.

Abstract: A method and apparatus for propelling a tool having a body within a passage. The tool includes a gripper including at least a gripper portion which can assume a first position that engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface. The gripper portion can also assume a second position that permits substantially free relative movement between the gripper portion and the inner surface of the passage. The tool includes a propulsion assembly for selectively continuously moving the body of the tool with respect to the gripper portion while the gripper portion is in the first position. This allows the tool to move different types of equipment within the passage. For example, the tool advantageously may be used in drilling processes to provide continuous force to a drill bit. This enables the drilling of extended horizontal boreholes.

Abstract: Enhanced horizontal drilling systems and methods encompass the production of crude oil from wells drilled from a subterranean production facility. This approach has the location of the well head below the oil reservoir to improve flow rate and recovery due to the consistent voiding of fluids by gravity flow within the well bore to the well head allowing well bore production pressure to achieve extremely low fluid pressure or even a vacuum of up to 15 PSI. This method increases oil recovery rate and factor, and lowers production costs. The present method is production of shallow crude oil by way of long horizontal or near horizontal boreholes drilled and serviced from a subsurface workroom. The subsurface workroom serves as both the drilling platform and the place to which production is centrally accumulated from the wells. Oil is collected in a central facility and is then lifted to the surface utilizing pumps.

Abstract: Method and apparatus for substantially cleaning fill from a borehole, variously including in preferred embodiments disturbing, particulate solids of fill while RIH, entraining particulates while POOH, jetting downhole while RIH and jetting uphole while POOH, and controlling at least one of a pump rate regime or a POOH rate regime.

Abstract: A method and apparatus for propelling a tool having a body within a passage. The tool includes a gripper including at least a gripper portion which can assume a first position that engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface. The gripper portion can also assume a second position that permits substantially free relative movement between the gripper portion and the inner surface of the passage. The tool includes a propulsion assembly for selectively continuously moving the body of the tool with respect to the gripper portion while the gripper portion is in the first position. This allows the tool to move different types of equipment within the passage. For example, the tool advantageously may be used in drilling processes to provide continuous force to a drill bit. This enables the drilling of extended horizontal boreholes.

Abstract: A method of and system for optimizing bit rate of penetration while drilling substantially continuously determine an optimum weight on bit necessary to achieve an optimum bit rate of penetration based upon measured conditions and maintains weight on bit at the optimum weight on bit. As measured conditions change while drilling, the method updates the determination of optimum weight on bit.

Abstract: A method and apparatus for propelling a tool having a body within a passage. The tool includes a gripper including at least a gripper portion which can assume a first position that engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface. The gripper portion can also assume a second position that permits substantially free relative movement between the gripper portion and the inner surface of the passage. The tool includes a propulsion assembly for selectively continuously moving the body of the tool with respect to the gripper portion while the gripper portion is in the first position. This allows the tool to move different types of equipment within the passage. For example, the tool advantageously may be used in drilling processes to provide continuous force to a drill bit. This enables the drilling of extended horizontal boreholes.

Abstract: A method of and system for optimizing bit rate of penetration while drilling substantially continuously determine an optimum weight on bit necessary to achieve an optimum bit rate of penetration based upon measured conditions and maintains weight on bit at the optimum weight on bit. As measured conditions change while drilling, the method updates the determination of optimum weight on bit.

Abstract: A drillstring pressure-modulation valve which is usable in combination with a downhole drilling motor and a drillstring thruster to compensate for changes in pressure drop through the drilling motor which normally occur during drilling. When conditions change during drilling, which in turn changes the pressure drop through the drilling motor, the drillstring pressure-modulation valve compensates for such changes to minimize the effect of such changes on the operation of the thruster and the resulting WOB created by the thruster. The modulation valve has a feature which allows it to find automatically a balanced preload condition for the main needle valve, the primary functional element within the modulation valve, each time the rig pumps are turned off and then turned on. The modulation valve is fully self-contained, and is assembled as part of the bottomhole assembly.

Abstract: A method of and system for optimizing bit rate of penetration while drilling substantially continuously determines an optimum weight on bit necessary to achieve an optimum bit rate of penetration based upon measured conditions and maintains weight on bit at the optimum weight on bit. As measured conditions change while drilling, the method updates the determination of optimum weight on bit.

Abstract: An apparatus for creating a pulling force on a bottom hole assembly contained within a bore hole is disclosed. Generally, the apparatus comprises a housing, a piston having a first section and a second section, and a venturi member, operatively associated with the piston, adapted for creating a zone of low pressure. In one embodiment, the housing is attached to a work string and the piston is attached to a bottom hole assembly. The first section of the piston and the housing forms a first chamber. The second section of the piston and the housing forms a second chamber. The venturi member contains a first passageway for communicating the zone of low pressure created by the venturi member with the first chamber; and a second passageway for communicating the inner diameter of the venturi means with the second chamber.

Abstract: A method and apparatus for propelling a tool having a body within a passage. The tool includes a gripper including at least a gripper portion which can assume a first position that engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface. The gripper portion can also assume a second position that permits substantially free relative movement between the gripper portion and the inner surface of the passage. The tool includes a propulsion assembly for selectively continuously moving the body of the tool with respect to the gripper portion while the gripper portion is in the first position. This allows the tool to move different types of equipment within the passage. For example, the tool advantageously may be used in drilling processes to provide continuous force to a drill bit. This enables the drilling of extended horizontal boreholes.

Abstract: A rock drilling machine of the self-feeding, integrated type which is designed to operate in situ in a drill hole. The rock drilling machine comprises a drive unit (1), an anchoring unit (2), and a feeding unit (3) which is active between the anchoring unit (2) and the drive unit (1). The drive unit (1) comprises a hydraulic power assembly (5, 8) at the rear end of the unit, a drill bit (21) which is rotatable at the front end of the unit, a guide (10) with a longitudinal cavity (23), which guide extends between the hydraulic power assembly and the drill head and connects these non-rotatably to each other, a rotatable drive shaft (22) which extends from the hydraulic power assembly, through the said cavity in the guide, for rotation of the drill bit, and first securing devices (17) in order to be able to anchor the drive unit releasably in the drill hole.

Abstract: A shielding apparatus comprises a cylindrical shield body, a crankshaft supported by the shield body rotatably around the axis of the shield body, a plurality of rotors successively provided in the direction of the axis in a front region ahead of the shield body and a driving mechanism for rotating the crankshaft around the axis, wherein the rotors define the outer surface of an approximately conical or truncated conical shape in conjunction with each other, and the adjoining rotors are made eccentric with respect to the axis of the shield body in the different directions from each other.

Abstract: A power generation unit associated with a downhole drilling motor capable of producing sufficient rotational speeds to produce power for operating downhole devices associated with the drilling operation. The power generation unit takes advantage of the high speed precessional rotation of the rotor within the stator to drive the generator. The assembly includes a multi-lobed rotor displaceable within a stator using drilling fluid pumped therethrough. A crankshaft, mounted at one end concentric with the rotor and at its high speed take-off end concentric with the stator, transfers the rotor center precession to the shaft of the generator. In a preferred embodiment, the generator will include a socket for simply connecting downhole devices requiring electrical power.

Abstract: A device for guiding a drilling tool into a well and for exerting a hydraulic force on the drilling tool includes a tubular body and an outer sleeve rotating about the body and longitudinally displaceable with respect to the body. Also, the device includes radially displaceable pistons, in an extension position, that come into anchoring engagement with the wall of the well and immobilize the external sleeve, as well as a jack to displace the body and the drilling tool integral therewith with respect to the external sleeve and to exert a pushing force onto the tool. Hydraulic circuits and appropriate control assembly are also provided for controlling the execution of a series of successive cycles of anchoring of the external sleeve in the well and of displacement of the drilling tool with respect to the external sleeve.

Abstract: An apparatus has an eccentric shaft on which are mounted rolls connected to one another by flexible members in the form of a corrugated collar for end sealing of the rolls and with auxiliary members for radial sealing of the rolls. The auxiliary members are received in a radial clearance defined between the adjacent rolls which are made hollow.

Abstract: For the drilling of bore holes there is provided an assembly of drilling machine elements which are positioned on top of each other and which include a gripping body comprising of two or more shells between which are positioned expanding-contracting cylinders for causing the shells to be pressed against the wall of a hole being drilled, a hollow drive shaft and a drilling tool being suspended below the gripping body. In addition to the above mentioned gripping body which acts outwardly of the center of the assembly, there are provided gripping plates which act radially inwardly of the hollow drive shaft to grip the stem of the drilling tool, which extends within the hollow drive shaft.

Abstract: A manually operated downhole for an underground earth boring apparatus having a pneumatically operated earth boring tool. A drill pipe is connected to the tool and to a source of pneumatic fluid. A valve is positioned in the drill pipe substantially adjacent to the tool between the tool and the source of pneumatic fluid. This downhole valve controls the flow of pneumatic fluid to the tool. The valve is operable in response to pushing or pulling on the drill pipe.

Abstract: An earth boring apparatus has a pneumatically operated earth boring tool, a flexible conduit or drill pipe connected to the tool and to a source of pneumatic fluid. The tool has an earth boring member and a reciprocally movable hammer positioned in the tool to apply a percussive force. A valve assembly in the flexible conduit or drill pipe substantially adjacent to the tool between the tool and the source of pneumatic fluid controls the flow of pneumatic fluid to the tool. The valve assembly has a pneumatic pressure-operated valve which is operable in response to the pressure of pneumatic fluid in the flexible conduit or drill pipe to be opened to permit flow of pneumatic fluid to the tool at a predetermined operating pressure to transmit an initial pulse of pneumatic fluid to initiate operation of the hammer. The valve is kept open at a lower pressure than that required to open it.

Abstract: In accordance with an illustrative embodiment of the present invention, a cased borehole is drilled under surface obstructions in a single pass operation. The drilling apparatus includes a rotary drill bit mounted on a guide head having a ball joint connection to a housing. Remote controlled hydraulic cylinders enable steering of the guide head and bit, so that the hole direction can be controlled at will. Casing sections connected to the housing are added end-to-end as the borehole is lengthened, and axial thrust is applied to the casing string at the borehole entrance by a drilling rig to force the bit against the formations. The bit is driven by drill pipe that is centralized within the casing, so that when the bit, guide head and housing emerge from the ground, these elements can be disconnected, and the drill pipe pulled out of the casing to leave an unobstructed, lined borehole that is formed in a single pass.

Abstract: The invention concerns an arrangement for underwater drilling of foundations, comprising at least one cutter (27) and one pump (29) for discharge of excavated material, and hydraulic motors for driving the said cutter and the said pump.It comprises an hydraulic turbine (16) capable of functioning by means of a fluid such as sea water, and an hydraulaic plant driven by the said turbine and designed for feeding the said hydraulic motors.

Abstract: The apparatus for making a substantially vertical slot in the ground, especially in a single operation in making a sealing or supporting wall, comprises a machine frame with a rectangular cross section guided in the slot in the ground with a plurality of guide surfaces and at least one driven cutting wheel positioned at the lower end of the machine frame. The machine frame and the cutting wheels have a width which correspond to the width of the slot in the ground within tolerances defined by the guide free play and the cutting free play. The machine frame is guided in the vertical slot with a plurality of guiding surfaces and comprises an upper guide frame and a lower guide frame. The cutting wheels are mounted on the lower guide frame. The controlling piston cylinder unit for control of the lower guiding frame is mounted between the upper and lower guiding frames.