| 摘要 |
A lifting boom having three telescopic sections. A hydraulic ram has the piston rod free end connected by a horizontal pin movable in guide slots at the rear of the base section. A deflection limiter is axially slidable on the piston rod, and is less high then the base section. The rear of the ram cylinder is pin connected by horizontal pins to the mid section, and has a transverse ram cylinder plate attached to it. Pull rods are connected to the deflection limiter and pass forwardly through the transverse plate, having detents at their forward ends beyond the transverse plates. A pair of chains extends from the base section forward and around sprockets at the rear of the mid section, being attached to the rear of the fly section, a further chain extending thence forwardly and around a sprocket on the front end of the ram cylinder, and thence rearwardly to an anchor on the base section; the ram sprocket has a roller portion which rolls on the fly section bottom plate to support the ram cylinder. The heel of the fly section raises the ram forward end when the boom is extended and the sections are cocked or arched, limited by the roller engaging the bottom of the fly section top plate. |
