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.