Hydraulic damper

In a hydraulic damper including a piston working in a cylinder and partitioning the interior of the cylinder into two liquid chambers, a piston rod having a first end connected to said piston and a second end extending to the outside of said cylinder, a liquid passage formed in said piston rod for connecting said two liquid chambers, an opening adjusting member movably disposed in said liquid passage for selectively adjusting the effective passage area of said liquid passage between at least three different passage area conditions, and actuating means for reciprocatingly moving said adjusting member between two extreme positions and at least one intermediate position corresponding to respective said passage area conditions, the improvement wherein said actuating means comprising:

• a rotary actuator;
• a reciprocably rotatable member connected to said adjusting member and driven by said rotary actuator;
• two fixed stop means for engaging with said rotatable member corresponding to said two extreme adjusting positions;
• at least one axially displaceable member displaceable in a direction parallel to the rotary axis of said rotatable member between a first position cooperating with and stopping rotary movement in respective given directions from either of said extreme adjusting positions of said rotatable member to define an intermediate position corresponding to said intermediate adjusting position and a second position permitting rotation of said rotatable member in said given directions;
• means for displacing axially said axially displaceable member between said first and second positions thereof;
• and
• means for preventing movement of said axially displaceable member in the circumferential direction at least when said axially displaceable member is in said first position thereof.