Shock absorber

A shock absorber comprising a tubular working cylinder to be mounted on a suspended part of a vehicle, a piston rod assembly slidably received in said working cylinder and having an end to be mounted on a fixed part of a vehicle, said piston rod assembly comprising a tubular piston having at a free end a piston member cooperating with said working cylinder to divide the interior thereof into an upper and a lower working chamber, a telescoping tube received slidably and sealingly in a bore of said piston member, a mass located in an extension of said working cylinder and mounted slidably on a tubular core and displaceable in response to a predetermined acceleration of said shock absorber from a first position in which said mass closes a first passage between said upper working chamber and a reservoir to a second position in which said first passage is open, spring means resiliently urging said mass toward a rest position wherein the first passage is closed and comprising a spring member which opposes slidable movement of the mass in either of two opposed axial directions, the spring member disposed between stops located at the tubular core, and an electromagnetic valve connected with said tubular core and comprising a spool valve displaceable by a solenoid coil between an open and a closed position, said electromagnetic valve being adapted to selectively open and close a second passage between said upper working chamber and reservoir, the electromagnetic valve operating independently of the mass.