Ratchet assembly device for fitting a back cover and/or a bezel onto a watch case middle

A ratchet assembly device for fitting a back cover and/or a bezel onto a watch case middle, comprising at least one elongated elastic assembly element combined with at least one elongated receptacle made in an assembly side face of one of the members to be assembled and forming in said assembly side face an opening through which a side portion of the surface of said elongated element projects for engagement by elastic deformation with a ratchet fastening element, fixedly connected to the other member to be assembled, upon the relative translatory displacement of these two members to fit them together, at least one of the faces of said ratchet fastening element being configured to hold said elastic assembly element under elastic strain and being orientated to resolve the force exerted upon it into a component parallel to said translatory displacement and the direction of which tends to hold said assembled members in place, wherein said elongated elastic assembly element is of tubular section and wherein a straight section of this receptacle is configured to allow the profile of a straight section of said elongated elastic assembly element of tubular section to be deformed by said ratchet fastening element upon coupling thereof.