Bumper energy absorber

A motor vehicle bumper energy absorber comprising:

• an outer tube rigidly attached to a body of a motor vehicle,
• an inner tube having an end connected to a bumper bar of said motor vehicle and supported on said outer tube for relative linear translation with said bumper bar between an extended position of said bumper bar and a retracted position of said bumper bar,
• a resistance medium means operative to resist linear translation of said bumper bar from said extended position to said retracted position thereof in response to an impact thereon thereby to convert into work a fraction of the kinetic energy of said impact on said bumper bar, and
• an actuator means on said body of said motor vehicle operative to linearly translate said inner tube between said extended and said retracted positions of said bumper bar and to prevent said resistance medium from resisting linear translation of said inner tube from said extended position to said retracted position of said bumper bar when such linear translation is effected by said actuator means wherein said actuator means comprises:
• a wedge-shaped groove in an outer wall of said inner tube facing an inner wall of said outer tube,
• a hard sphere in said wedge-shaped groove having a diameter corresponding to the depth of a deep end of said wedge-shaped groove,
• a shuttle supported on said inner tube for back and forth linear translation in the direction of linear translation of said inner tube relative to said outer tube,
• an actuator rod supported on said body for back and forth linear translation in the direction of linear translation of said inner tube relative to said outer tube having an end rigidly connected to said shuttle,
• a drive means operative to effect back and forth linear translation of said actuator rod,
• a first stop means on said shuttle engageable on said inner tube operative to transfer thrust from said shuttle to inner tube to effect linear translation of said inner tube from said extended position of said bumper bar toward said retracted position of said bumper bar,
• a second stop means on said shuttle engageable on said inner tube operative to transfer thrust from said shuttle to inner tube to effect linear translation of said inner tube from said retracted position of said bumper bar toward said extended position of said bumper bar, and
• a radial finger on said shuttle engageable on said sphere in said wedge-shaped groove to confine said sphere to said deep end of said wedge-shaped groove concurrent with the transfer of thrust from said shuttle to inner tube to effect linear translation of said inner tube from said extended position of said bumper bar toward said retracted position of said bumper bar.