Extensible beam arrangement

摘要

Rock drilling equipment includes a boom carrying an extensible beam arrangement supporting a drilling mast, the extensible beam arrangement comprising a support pivotally mounted on the boom, a first elongated element slidably mounted on the support for movement longitudinally of the first element, a second elongated element slidably mounted on the first element for movement longitudinally of the first element, and drive transmission means sensitive to movement of the first element and adapted to move the second element relative to the support upon sensing relative movement between the support and first element.