Abstract: Contactor comprising at least two fixed studs, at least one movable stud capable of making or breaking an electric contact between the two fixed studs, and at least one membrane which can deform under the action of a fluid. The movable stud is fastened to the membrane in such a manner that the movable stud is isolated from the two fixed studs in position of rest. The contactor is characterized by the fact that the membrane comprises the following two parts:(a) at least one substantially nondeformable base to which the movable stud is fastened; and(b) flanks which are elastic with respect to the base and firmly attached to the base, the deformation of the membrane being obtained substantially solely by stretching of the flanks, this deformation causing a displacement of the base and therefore a displacement of the movable stud.

Abstract: An erosion device comprising at least one head and means for imparting to the head movements of rotation around an axis and of translation along said axis is improved due to the fact that:(a) the head comprises knives each having several teeth; on each knife two adjacent teeth are spaced apart from each other and leading edges of the teeth and their virtual extensions form a practically continuous line, called line of attack;(b) the teeth being capable of digging grooves in a material to be eroded, the groove corresponding to each tooth having a portion in common with at least one groove corresponding to a tooth of an adjacent knife.