A hydraulic machine including: a casing rotatably mounted relative to a shaft; first brake means constrained to rotate with the casing; second brake means constrained to rotate with the shaft, and adapted to co-operate with the first brake means; a braking piston associated with return means and tending to exert a braking force; and a brake-release chamber adapted to be connected to a pressure force so as to apply a brake-release pressure selectively to the braking piston, so as to enable the first and second brake means to be separated; said hydraulic machine including a sweeping channel arranged in the shaft so as to define a leakage flow between the brake-release chamber and an internal volume of the casing.

A hydraulic machine including: a casing rotatably mounted relative to a shaft; first brake means constrained to rotate with the casing; second brake means constrained to rotate with the shaft, and adapted to co-operate with the first brake means; a braking piston associated with return means and tending to exert a braking force; and a brake-release chamber adapted to be connected to a pressure force so as to apply a brake-release pressure selectively to the braking piston, so as to enable the first and second brake means to be separated; said hydraulic machine including a sweeping channel arranged in the shaft so as to define a leakage flow between the brake-release chamber and an internal volume of the casing.

A hydrostatic machine comprising a stator and a rotor. The stator comprises an inner cylindrical surface with a constant diameter and a cam ring comprising a cam track on the inner circumference thereof, the outer circumference of the cam ring being mounted in the aforementioned inner cylindrical surface. The hydrostatic machine also comprises two bearings that allow the rotation of the rotor in relation to the stator and that are mounted on the inner cylindrical surface of the stator, axially on either side of the cam ring, the cam ring and the two bearings having the same outer diameter.

The hydraulic machine includes a cam and a cylinder block with pistons co-operating with cam lobes, each of which has two ramps extending between top and bottom dead center arcs. The cylinders are connected in alternation to a feed and to a discharge, in sequences separated by switchover stages including an isolation stage during which they are isolated relative to the feed and discharge main ducts. The angular position of the start or of the end of at least one first isolation stage relative to the corresponding dead center arc is different from the angular position of the start or of the end of at least one second isolation stage relative to its corresponding dead center arc, both of these dead center arcs being top dead center arcs or both of them being bottom dead center arcs.

The hydraulic machine includes a cam and a cylinder block with pistons co-operating with cam lobes, each of which has two ramps extending between top and bottom dead center arcs. The cylinders are connected in alternation to a feed and to a discharge, in sequences separated by switchover stages including an isolation stage during which they are isolated relative to the feed and discharge main ducts. The angular position of the start or of the end of at least one first isolation stage relative to the corresponding dead center arc is different from the angular position of the start or of the end of at least one second isolation stage relative to its corresponding dead center arc, both of these dead center arcs being top dead center arcs or both of them being bottom dead center arcs.

The assembly may include a cylinder block, a plurality of pistons, and a holding element, the holding element extending over all or part of the outer periphery of the cylinder block. The holding element may include a plurality of guide portions, each partially blocking a recess of the cylinder block so as to come into contact with a planar end of the crown of a piston to guide in the translation of each piston in their respective recesses. The holding element may include two indexing means cooperating with two indexing means of the cylinder block so as to hold the holding element under a traction force when positioned around the cylinder block.

A device for hydraulically operating a drive wheel of a wellbore tractor has, in certain embodiments, at least one cam and a rotatable assembly arranged to be rotatable with respect to the cam about an axis of rotation. The rotatable assembly has at least one piston. The device also has a chamber and at least one supply port for supplying hydraulic fluid from the chamber to the piston for energizing the piston, the supply port being arranged to be moved between first and second positions relative to the cam. In the first position, the piston can connect to the supply port and be energized to impart force against the cam for producing forward rotation of the assembly. In the second position, the piston can connect to the supply port and be energized to impart force against the cam for producing reverse rotation of the assembly. Related distributor assembly, wellbore tractor, and method are also described.

A device for hydraulically operating a drive wheel of a wellbore tractor has, in certain embodiments, at least one cam and a rotatable assembly arranged to be rotatable with respect to the cam about an axis of rotation. The rotatable assembly has at least one piston. The device also has a chamber and at least one supply port for supplying hydraulic fluid from the chamber to the piston for energizing the piston, the supply port being arranged to be moved between first and second positions relative to the cam. In the first position, the piston can connect to the supply port and be energized to impart force against the cam for producing forward rotation of the assembly. In the second position, the piston can connect to the supply port and be energized to impart force against the cam for producing reverse rotation of the assembly. Related distributor assembly, wellbore tractor, and method are also described.

A device for hydraulically operating a drive wheel of a wellbore tractor has, in certain embodiments, at least one cam and a rotatable assembly arranged to be rotatable with respect to the cam about an axis of rotation. The rotatable assembly has at least one piston. The device also has a chamber and at least one supply port for supplying hydraulic fluid from the chamber to the piston for energizing the piston, the supply port being arranged to be moved between first and second positions relative to the cam. In the first position, the piston can connect to the supply port and be energized to impart force against the cam for producing forward rotation of the assembly. In the second position, the piston can connect to the supply port and be energized to impart force against the cam for producing reverse rotation of the assembly. Related distributor assembly, wellbore tractor, and method are also described.

A device for hydraulically operating a drive wheel of a wellbore tractor has, in certain embodiments, at least one cam and a rotatable assembly arranged to be rotatable with respect to the cam about an axis of rotation. The rotatable assembly has at least one piston. The device also has a chamber and at least one supply port for supplying hydraulic fluid from the chamber to the piston for energizing the piston, the supply port being arranged to be moved between first and second positions relative to the cam. In the first position, the piston can connect to the supply port and be energized to impart force against the cam for producing forward rotation of the assembly. In the second position, the piston can connect to the supply port and be energized to impart force against the cam for producing reverse rotation of the assembly. Related distributor assembly, wellbore tractor, and method are also described.