Shock absorber for vehicle use

A shock absorber for vehicular use employing:

• a tubular casing provided at one end with a first mounting member for connection with a wheel-supporting member of a vehicle, a cylinder fixedly received in said casing, a piston slidably fitted in said cylinder to define a pair of first and second fluid chambers on the opposite sides thereof, a piston rod connected at one end with said piston and provided at the other end with a second mounting member for connection with a body portion of the vehicle, a damping-force control mechanism arranged in said cylinder for controlling the damping effect upon sliding movement of said piston relative to said cylinder, a first spring seat mounted on said piston rod for turning movement relative thereto, a second spring seat secured to said tubular casing, a suspension spring arranged between said first and second spring seats, a click stop mechanism provided between said first spring seat and said first mounting member for controlling the turning of said first spring seat relative to said piston rod in a stepwise manner, an adjusting sleeve fitted over said piston rod for rotation relative thereto, said adjusting sleeve being operatively connected at its opposite ends with said first spring seat and said damping-force control mechanism, said damping-force control mechanism comprising a first and a second fluid passageway formed in said piston for fluid communication between said first and second fluid chambers, an orifice disc connected to the adjusting sleeve on one side of said piston, for rotation relative to the latter and formed with a plurality of orifices of different diameters, said orifices being arranged so as to be selectively placed in fluid communication with said first fluid passageway upon rotation of said orifice disc relative to said piston, and a normally closed valve member arranged on the other side of said piston so as to open said second fluid passageway when the pressure in said first fluid chamber is increased to reach a predetermined level.