Shock absorber

A shock-absorber of the piston-and-cylinder kind for use in the landing gear of an aircraft and comprising a cylinder, a piston-rod and a shock-absorbing rod which encloses a chamber for compressed gas and is provided with a valve having a throttling orifice, said shock-absorbing rod is mounted to slide, in a fluid-tight manner in a first chamber filled with hydraulic fluid in either said cylinder or said piston-rod, to form a oleopneumatic shock-absorber;

• said piston-rod is mounted to slide, in a fluid-tight manner in said cylinder and is solidly connected to a piston-head which, with said cylinder, defines a descent chamber to control lowering of the landing gear when hydraulic fluid is admitted to said descent chamber, said shock-absorber also comprises a lifting piston to load said shock-absorber and mounted to slide within a second chamber in either said cylinder or said piston-rod, so defining a lifting chamber to control lifting of the landing gear when hydraulic fluid is admitted to the lifting chamber through a hydraulic locking valve having a pressure-controlled opening and a locking device for locking said piston-rod in relation to said cylinder, in the "landing gear down" position, said locking device being releasable in two ways, firstly by the application of the lifting pressure to the landing gear, which simultaneously pressurizes said lifting chamber, by displacement of said lifting piston which loads said shock-absorber, and voids said descent chamber by displacement of said piston-rod in said cylinder, and secondly by the application of a simple pressure for releasing said locking device, thus permitting said piston-rod to be displaced in said cylinder under the action of the weight of the aircraft which thus moves the landing gear into a dropped position when said descent chamber is voided, the movement from the dropped position or the "landing gear retracted" postion to the "landing gear down" position being effectable solely by applying a descent pressure simultaneously in said descent chamber and at said locking valve, so as to open said locking valve.