US Patent 7469776 Rotation damper with valve

A rotation damper for a vehicle that runs on rails, having piston and cylinder parts moving with respect to one another. This damper has a friction characteristics, that is to say the fluid connection over the piston is not a permanently open hole but exclusively comprises spring-loaded valves. In order to facilitate the installation of such dampers, it is proposed to make a separate connection between the working cylinder and the reservoir in which a valve that can be manually operated is arranged, which valve, on operation, opens a connection as a result of which the piston and cylinder can be moved relative to one another under manual force.