Ladder or boom extension system

An extension system for a ladder or boom of the type including a base section and at least one section movable relative to the base section in response to forces directed by a hydraulic circuit comprising

• a piston and piston rod fixedly secured in the base section;
• a hydraulic cylinder longitudinally movable relative to the piston rod in response to hydraulic forces in the hydraulic circuit, the cylinder having a first end and a second end;
• a first crosshead means affixed to the cylinder nearer to the first end and being adapted to be moved by the cylinder,
• the first crosshead rotatively carrying at least a first pulley;
• a first cable means trained about the first pulley, the first cable means having first and second ends, the first and second ends being respectively connected to a portion of the base section and to a portion of the movable section;
• and
• a second crosshead means affixed to the cylinder nearer to the second end and being adapted to be moved by the cylinder;
• whereby the cable causes movement of the movable section relative to the base section in response to movement of the cylinder.

An extension system for an aerial or boom having a base section and at least one movable section in telescoping relation thereto comprising

• a piston rod including a medially positioned piston secured in the base section;
• a double acting cylinder longitudinally movable relative to the piston rod in response to fluid forces upon the piston;
• a front crosshead and a rear crosshead secured to the cylinder and adapted to be moved as the cylinder is moved,
• each crosshead comprising at least one pulley and at least one guide;
• a front cable trained about the front crosshead pulley and having its ends respectively secured to the base section and to the movable section;
• and a rear cable trained about the rear crosshead pulley and having its ends respectively secured to the base section and to the movable section;
• whereby longitudinal movement of the cylinder causes either the front cable or the rear cable to pull the movable section to extend or retract the movable section relative to the base section.