US Patent 9234587 Multi-capacity cylinder

A multi-capacity hydraulic cylinder includes a hollow cylinder closed by a cylinder head, an annular piston moveable within the hollow cylinder to divide the interior of hollow cylinder into a first chamber and a second chamber, a hollow piston rod coupled to the piston and aligned with an opening in the piston, and a secondary rod moveable within the hollow piston rod to define a third chamber in the hollow piston rod, where the third chamber has a cross-sectional area that is less than the cross-sectional area of the first chamber.