Abstract: A method and device for automatically adjusting the lightening of a working unit (U) of a machine by use of a hydraulic ram (57) associated with a hydropneumatic accumulator (67). Use is made of a second hydraulic ram (58) of which the piston (53), which can move as far as a predetermined position (PP) in the cylinder (C2) and which is detached from the rod (46) of the first hydraulic ram (57), acts directly or indirectly on the latter rod via the oil (O) contained in the first hydraulic ram (57). The working unit (U) is raised and lowered by the second hydraulic ram (58). When raising the working unit (U), the volume of oil in the first hydraulic ram (57) is increased or decreased in such a way that the working unit (U) is always at a predetermined height (HP) at the end of raising travel.

Abstract: A mowing machine includes a harvesting mechanism which extends during mowing transversely to a working direction, and a lightening device for the harvesting mechanism which includes at least one elastically deformable member whose action can be adjusted by way of an adjustment device connected to the elastically deformable member. The elastically deformable member can include a deformable envelope which contains a gas under adjustable pressure. The adjustment device can include a supply circuit provided with at least one electrovalve or gate connected to the deformable envelope. In an alternative embodiment, the adjustment device can include at least one jack connected to a mechanical spring, and a supply circuit provided with at least one gate or electrovalve connected to the jack.

Abstract: A valve includes a distributor with four ports and two positions. In a first position, a first non-return valve allows only circulation of a fluid from the first port toward the third port, while the second port and the fourth port are directly in communication with one another. In a second position, the third port and the fourth port are directly in communication with one another, while a second non-return valve allows only circulation of fluid from the third port and the fourth port in communication toward the first port.

Abstract: An agricultural machine has a fixed structure, a retractable assembly connected to the fixed structure by at least one joint such that said retractable assembly can move to at least one locking position, and a locking mechanism. The locking mechanism includes (i) at least one stop element mounted for movement with one of the fixed structure and retractable assembly and cooperable with the other of the fixed structure and the retractable assembly to lock the retractable assembly in one locking position; (ii) at least one elastic element cooperating with the at least one stop element to bias the at least one stop element into a stop element lock position in cooperation with the other of the fixed structure and the retractable assembly so as to lock the retractable assembly in the locking position. The stop element is enclosed in the stop lock position such that the stop element can be moved from the said stop lock position only by a special tool.