Abstract: Apparatus for tensioning a safety belt, in which tension is applied to the belt through the action of a piston in a working cylinder, includes a mechanism for blocking the reverse action of the piston in the cylinder following the application of pressure. The reverse motion blocking mechanism includes at least one wedge, movable along a slide surface in response to the application of gas pressure, and toothings on the piston into which the wedge may be lodged to prevent reverse motion of the piston following the application of tension to the safety belt.

Abstract: An apparatus for tensioning a safety belt in response to applied gas pressure makes use of hollow winding roller attached to the safety belt and having a selected contour on its inner surface. A piston in a working cylinder is located coaxially adjacent to the roller. When the piston is displaced by the application of gas pressure it projects into the roller and engages the contouring on the inside surface of the roller to cause the roller to rotate in the direction of belt tightening.