Abstract: A damper includes a cylinder containing a hydraulic fluid inside which is a piston defining first and second chambers in the cylinder, the second chamber containing the piston rod. A hydraulic fluid reservoir communicates selectively with the first chamber. A reference chamber contains a gas at substantially constant pressure. A control valve is acted on by the pressure of fluid in the first chamber (tending to open the valve), by a return spring, by the pressure in the reference chamber and by the pressure of fluid in the second chamber (tending to close the valve). A flow restrictor between the reservoir and the first chamber enables hydraulic fluid to flow only from the first chamber to the reservoir. It defines a control pressure to open the valve in response to the rate of inward movement of the piston rod exceeding a predetermined limit value. The flow rate permitted by the flow restrictor is variable so that the valve can open at rates of inward movement different to the predetermined limit value.

Abstract: A shock absorber has a cylinder, a piston dividing the cylinder into two chambers, and a valve in the piston which opens to permit hydraulic fluid to flow through the piston when the compression rate of the shock absorber exceeds a limit value. The valve is moved to its open position by the pressure of hydraulic fluid in the chamber in the path of piston movement, and it is biased toward its closed position by a spring on the piston, a constant pressure gas in a reference chamber on the piston and the pressure of hydraulic fluid in the chamber behind the path of piston movement. Fluid from the contracting chamber is released by a check valve into a storage space.