Blocking device for a handle-bar stem

Claim 1

In a structure comprising in combination: a handle-bar stem having a cylindrical plunger tube for insertion in a cylindrical fork tube of a wheeled vehicle, and a device for blocking the plunger tube in the fork tube; the improvement comprising in combination a tightening screw extending through the plunger tube in coaxial and rotatable relation to the plunger tube, a nut screwthreadedly engaged on and coaxial with the screw, the plunger tube defining at least three first bevelled faces in the vicinity of a lower end of the plunger tube, the nut defining a number of second bevelled faces corresponding to the number of first-bevelled faces, the second faces of the nut being upwardly convergent and the first faces of the plunger tube being downwardly convergent relative to the axis of the plunger tube, and expanding means comprising a number of double wedges arranged around the axis of the screw corresponding to the number of first-bevelled faces, each double wedge having a planar bevelled third face and a planar bevelled fourth face respectively bearing laterally against a corresponding first face of the tube and a corresponding second face of the nut, said first, second, third and fourth faces having in planes perpendicular to the axis of the plunger tube a rectilinear contour whose radius is centered on the axis of the plunger tube, and the planar faces of said double wedges terminate in spaced lateral edges which are in engagement with those of an adjacent double wedge along the median plane transverse thru said double wedges, with the outer peripheries of said double wedges contiguous with the outer periphery of said plunger tube, the screw having an enlarged end portion which is in axial abutting relation to the stem and is accessible from outside the stem, and the screw being cooperative with the nut to urge the double wedges radially outwardly against the fork tube by axial displacement of the nut on the screw upon rotation of the screw relative to the plunger tube, and means for retaining the double wedges between the plunger tube and the nut.