1. Field of the Invention
This invention relates to an impact damper having two tubes slidable one about the other, such that one of the tubes can be pushed into the other tube. In particular, such an impact damper is used in a motor vehicle to slow down the motor vehicle upon collision of the motor vehicle with an obstacle. Such an impact damper works by means of hydraulic damping forces and pneumatic spring forces. The inner tube of the impact damper is closed by a bottom, or base, and essentially comprises, in sequence starting from the base, a gas chamber holding a gas cushion at high pressure, a separating piston guided tightly and movably within the inner tube, a first fluid chamber, a partition defined within the inner tube and having a throttle opening, a second fluid chamber in communication with the first fluid chamber via the throttle opening, and a work piston.
2. Background Information
Known impact dampers, such as the impact damper as disclosed by DE-PS 34 19 165, which corresponds to U.S. Pat. No. 4,641,872, can generally have two tubes which are movable one inside of the other. Of the two tubes, the sealed inner tube of DE-PS 34 19 165 includes, in sequence starting from the bottom, a gas chamber containing a high pressure gas cushion, a separating piston guided so that it can move in a sealed manner within the inner tube, and a first fluid chamber connected via a throttle to a second fluid chamber, the first fluid chamber generating hydraulic damping forces. With such an impact damper, the maximum stroke of the impact damper is essentially large enough to absorb a collision impact at speeds of up to about 8 km/h. The expansion equalization and the return of the impact damper into the base configuration is accomplished by means of the gas cushion which is contained within the closed gas chamber.