Variable orifice oil/gass damper for aircraft landing gear

A variable orifice damper for dissipating energy in an aircraft landing gear, comprising:

• a hollow cylinder having an elongated wall defining a longitudinal axis, said elongated wall being closed at each longitudinal end, the cylinder containing a cavity portion having an axially variable cross sectional area between the longitudinal ends;
• a piston rod defining a longitudinal axis and mounted for sliding movement in the cylinder, said piston rod being supported laterally by and extending through one of said closed longitudinal ends of the cylinder, said piston rod having an axial bore sealed against passage of fluid, a separator portion located within the bore for sliding movement therein dividing the bore into first and second members, and at least one passage communicating the first chamber to the interior of the cylinder;
• a portion head carried by the piston rod, adapted to pass through the cavity portion with a predetermined space therebetween, the size of the space between the cavity portion and the piston head changing as the position of the piston head changes relative to the position of the cavity portion;
• and
• a tail rod connected to the piston rod, said tail rod being supported laterally by and extending through the other of said closed longitudinal ends of the cylinder, wherein the cavity portion of said hollow cylinder contains a first cavity portion, a second cavity portion, and a third cavity portion located between the first cavity portion and the second cavity portion along the longitudinal axis of the cylinder, the cross sectional area of the first and second cavity portions being constant and the cross sectional area of the third cavity portion changing along the longitudinal axis of the cylinder, such that at each end of the third cavity portion the cross sectional area of the third cavity portion equals that of the adjacent first and second cavity portion respectively, and between each end of the third cavity portion the cross sectional area of the third cavity portion is reduced along the longitudinal axis of the cylinder, and wherein the size of the predetermined space changing such that it is greater adjacent the first and second cavity portions.