Contractable shock absorber strut

A contractable single acting shock absorber strut comprising:

• an outer cylinder closed at one end and open at the other end;
• a centrally open bearing defining the open end of said cylinder;
• a strut piston mounted for reciprocation in said cylinder and extendable therefrom through said centrally open bearing, said strut piston being closed at its extendable end and open at its other end whereby shock absorber fluid is free to pass between the interiors of said cylinder and said strut piston;
• a contracting piston slideably mounted in said cylinder externally of said strut piston;
• a floating piston slideably mounted in the extendable end of said strut piston;
• a first constantly open fluid port in said cylinder between said contracting piston and said centrally open bearing;
• a second constantly open fluid port in said strut piston between said floating piston and the extendable end of said strut piston;
• a source of hydraulic fluid pressure;
• a return to said source;
• a first fluid duct between each of said first and second fluid ports and said hydraulic fluid source;
• a second fluid duct between each of said first and second fluid ports and said return;
• and
• a control valve for said fluid ducts operable to selectively connect either one of said fluid ports to receive hydraulic fluid from said source and simultaneously connect the other of said fluid ports to said return whereby said floating piston may be hydraulically locked in a fixed position while said strut piston is free to reciprocate in said cylinder and may be selectively unlocked while said strut piston is fully contracted into said cylinder.