Patent ID: 7779580

Claim:
A guidance device for guiding a first mast having a first axis with respect to a second mast having a second axis, the second mast being installed substantially coaxially within the first mast and being slidable therein, said guidance device being fixed to one end of the first mast and engageable with a contact area on the outside face of said second mast, said guidance device including at least one guide unit arranged to cooperate with a corresponding contact area on said second mast, the thrust direction of said guide unit being substantially orthogonal to the contact area with which it will cooperate, said guide unit comprising: a roller freely mounted to rotate about an axis substantially orthogonal to the direction of thrust, the guidance device being installed such that the roller axis is substantially orthogonal to said first mast axis; a pad having a bearing face substantially orthogonal to the thrust direction, the rotational axis of the roller is fixed to a lever installed to freely pivot around an axis fixed with respect to the pad and substantially parallel to the axis of the roller; and elastic means for displacing the roller axis with respect to the pad substantially parallel to the thrust direction as a function of forces applied by the mast on the roller, between a first position in which the roller extends beyond said bearing face of the pad, the bearing area of said guide unit on Said masts being formed only by a portion of said roller, and a second position in which said roller does not extend beyond the bearing face of the pad, the bearing area of the guide unit on the masts being formed by a portion of said roller and said pad.