A hydraulic swivel drive for a grab that has two gripping arms or shells movable like tongs, including two swivel shafts parallel to each other and rotatably mounted in a drive housing, whose shaft ends are connectable with the gripper arms or shells, wherein the swivel shafts each have two oppositely threaded screw engagement portions, with which two pistons movable in opposite directions by means of hydraulic pressure for driving the swivel shafts are in screw engagement. Two differently large and differently contoured cylinder pressure chambers can be assigned to each piston in order to optimally adapt the cross-sectional area of the pistons for each of the reciprocating positioning movements and to appropriately select the pressure conditions. To be able to run in the differently contoured and dimensioned cylinder pressure chambers, each of the pistons is provided with different piston portions which are adapted to the respective cylinder pressure chamber.

A hydraulic control circuit operable to selectively hydraulically link first and second hydraulic actuators and to bypass that hydraulic link.

The disclosure concerns an excavation machine for making a trench into ground including a frame extending along a longitudinal direction, an excavation device disposed under the lower end part of the frame, the excavation machine further including at least a first guide device comprising at least a first guide flap protruding from a first lateral side of the frame outwardly of the frame, and wherein, considered in a plane perpendicular to the longitudinal direction, the first guide flap is inclined relative to the first lateral side.

A clamp assembly comprising a pair of clamps may couple to an assembly body. The clamps may pivot to receive material beneath the assembly body. The clamps may include opposing surfaces that define a scoop space beneath the assembly body. Each of the clamps may include a cutting plate. The cutting plate may include a perforating edge configured to extend into the scoop space relative to a corresponding one of the opposing surfaces. The clamp may further include a retention plate. The retention plate may include an inner surface that faces the cutting plate. The cutting plate and the retention plate further define the scoop space between the clamps. The clamp assembly may couple to a lift assembly. The lift assembly may include a hydraulic actuator configured to raise and lower the clamp assembly.

A clamp assembly comprising a pair of clamps may couple to an assembly body. The clamps may pivot to receive material beneath the assembly body. The clamps may include opposing surfaces that define a scoop space beneath the assembly body. Each of the clamps may include a cutting plate. The cutting plate may include a perforating edge configured to extend into the scoop space relative to a corresponding one of the opposing surfaces. The clamp may further include a retention plate. The retention plate may include an inner surface that faces the cutting plate. The cutting plate and the retention plate further define the scoop space between the clamps. The clamp assembly may couple to a lift assembly. The lift assembly may include a hydraulic actuator configured to raise and lower the clamp assembly.

A hydraulic control circuit operable to selectively hydraulically link first and second hydraulic actuators and to bypass that hydraulic link.