Hydraulic fluid circuit having a hydraulic motor and a three-position selector for selecting the circulation of fluid

Hydraulic fluid circuit comprising:

• a hydraulic motor with two directions of rotation, comprising a stator and a rotor, in particular of the type used for driving the members for displacing a machine in translation, said motor having two principal ports respectively intended to serve for supply and exhaust of fluid,
• a device for immobilization of the rotor of the motor which comprises at least one immobilization member and means for urging said member into an active position in which the rotor is immobilized and into an inactive position in which the rotor is free to rotate with respect to the stator,
• hydraulic fluid circulation means,
• two principal conduits, respectively intended to be connected to each of the two principal ports of the motor to serve as supply and exhaust conduits for the motor when the latter is in operation,
• a device for selecting the circulation of the fluid between the principal ports of the motor and the principal conduits to which they are respectively connected, this device comprising a principal selector capable of occupying a rest position in which, the fluid pressures in the principal conduits being substantially equal, the circulation of fluid between the principal conduits and the corresponding principal ports is prevented in the sense of exhaust;
• a first active position in which, the fluid pressure in the first principal conduit being greater than the fluid pressure in the second principal conduit, the circulation of fluid between the first principal conduit and the first principal port is allowed in the sense of supply while the circulation of fluid between the second principal conduit and the second principal port is allowed in the sense of exhaust;
• and a second active position in which, the fluid pressure in the first principal conduit being less than the fluid pressure in the second principal conduit, the circulation of fluid between the first principal conduit and the first principal port is allowed in the sense of exhaust while the circulation of fluid between the second principal conduit and the second principal port is allowed in the sense of supply, the selection device further comprising means for controlling the displacement of the principal selector between its three positions, wherein the means for controlling displacement of the principal selector comprise an intermediate system of selection capable of adopting a first configuration in which the principal selector is maintained in its position of rest and a second configuration in which the principal selector is allowed to leave its position of rest to adopt one or the other of its active positions, as well as two pilot conduits capable of being taken to the same pressure or to different pressures via the intermediate system of selection, the means for controlling the displacement of the principal selector further comprising means for controlling the intermediate system of selection which are connected to the immobilization device so that said intermediate system of selection is allowed to pass from its first to its second configuration only once the immobilization member has been urged towards its inactive position.