Abstract: A lifting apparatus comprising a chassis, a platform, a stretchable boom assembly comprising lower, middle, upper and cover member respectively axially aligned with each other, a sliding member mounted on the upper boom including a hydraulic cylinder, and other three hydraulic cylinders respectively mounted in the lower boom, between the lower boom and the chassis and between the upper boom and the platform, a hydraulic control system for operating the three hydraulic cylinders in synchronism to move the platform toward and away from the chassis in a substantially perpendicular relation to the chassis. Load on the platform is imposed on the cover member, next on the stretchable member so that the load on the platform is stably movable horizontally and vertically irrespective of the level difference provided between each of the stretchable boom assembly.

Abstract: A lifting apparatus comprises a mobile vehicle, a platform disposed above the mobile vehicle, a single telescopic stretchable boom pivotally joined at the lower end with a pin to the mobile vehicle and at the upper end with a pin to the platform, and a hydraulic control system comprising a control circuit and a hydraulic circuit.