US Patent 10562488 Load limiting seatbelt retractor

A seatbelt retractor includes a base, a spool, a cylinder and a cylinder lock. The spool is rotatably coupled to the base and has a piston portion. The cylinder is engaged with the piston portion and therewith defines a first chamber. The piston portion is movable from a first position yielding a first chamber volume to a second position yielding a second chamber volume. The cylinder lock in a first condition rotatably fixes the cylinder to the base. Damping fluid is disposed in the chamber.