Two-stage variable orifice energy absorber with cylinder cap having radially fixed blow out orifice

摘要

Energy absorbing unit for vehicle bumper support having inner and outer telescoping cylinders with a radially fixed flow control orifice in the piston cap for recessing a cooperating metering pin concentric with the orifice for controlling the flow of fluid between a pair of contractible and expansible fluid chambers to dissipate impact energy in a first stage operation. The radially fixed flow control orifice is designed to break away from the piston cap in response to predetermined high pressure buildup in one of the chambers to increase the opening between the chambers in a second stage operation to thereby reduce pressure and absorb the energy of increased impact load. A gas spring in the unit moves the two cylinders to their extended position on removal of bumper impact load.