Hydraulic machine, in particular hydraulic motor, with a reciprocating movement, and differential piston for such a machine

A differential hydraulic machine, comprising:

• a casing (1);
• a differential piston (4) having a region (5) of large cross section and a region (6a) of smaller cross section capable of sliding in a reciprocating movement in the casing and in a smaller-diameter housing coaxial to the casing, respectively, the piston separating two chambers (8, 9) of the casing;
• hydraulic switching means (C) for supplying liquid to and emptying from the two chambers separated by the differential piston, the hydraulic switching means being controlled by the reciprocating movement of the piston and being able to adopt two stable positions;
• and
• triggering means capable of causing, at end of the travel of the piston, a sudden change in a position of the hydraulic switching means, under action of an elastic means (E), in order to reverse travel of the piston, the piston (4) being equipped, in the region of the large cross section (5) and of the region of smaller cross section (6a), with sealing lips (48, 49) directed in opposite directions,
• wherein the sealing lips (48, 49) are provided on detachable circular rings (50, 51) and the piston (4) is molded as a single piece;
• and
• wherein each of the detachable circular rings (50, 51) is fixed to the piston by an assembly of a bayonet type.