Impact sensor assembly

Claim 1

A motor vehicle energy absorbing apparatus having a cylindrical housing adapted to be mounted on a vehicle frame member, a sleeve member telescopically slidable within the cylindrical housing from one end of the latter, a piston and piston rod assembly projecting into the sleeve, the piston being mounted on one end of the piston rod, passageways in the piston providing communication between both sides thereof, a compressible material located within the sleeve and capable of passing from one side to the other of the piston as the sleeve telescopes within the cylindrical housing under vehicle impact conditions, and anchor means fixedly coupling the piston and piston rod assembly to the other end of the cylindrical housing, characterized in that: the anchor means comprises a shearable flange member threadedly mounted on the other end of the piston rod, a shearing means comprising a die nut threadedly anchored in the housing in abutting relation to the shearable flange, the shearable flange member being coupled to the housing by being held on the die nut by a clamp nut, the shearable flange member being shearable by the shearing means and permitting axial movement of the piston and piston rod assembly relative to the housing in reaction to an impact force on the energy absorbing apparatus in excess of a predetermined value, and a crushable switch means mounted between the shearable flange member and a base portion of the die nut in the path of movement of the shearable flange member and adapted upon being crushed by the latter to close an actuating circuit.