Abstract: A drill boom arrangement comprises a boom proper that is universally pivotably carried by a boom support. The boom carries a feed beam for a rock drill. The boom is swingable on the support by means of two hydraulic cylinders forming a tripod and the feed beam is swingable on the boom by means of two hydraulic cylinders forming another tripod. One of the boom swinging cylinders (17) is coupled in series with one of the feed beam swinging cylinders (28) and these two cylinders are actuated by means of a common direction control valve (58). The boom swinging cylinder (17) can be short-circuited so that the feed beam can be swung upon actuation of the direction control valve (58) while the boom is arrested. The other boom swinging cylinder (16) is coupled in series with the other feed beam swinging cylinder (29) to a common direction control valve (57) in the same way. A joy-stick (59) is coupled to the two direction control valves (57, 58) through pilot valves and pilot lines (64-67).

Abstract: A drill boom arrangement comprises a boom proper (10) that is universally pivotably mounted on a support plate (13). The boom is swingable by means of two hydraulic cylinders (16, 17) that are coupled between the support plate and the boom to form a tripod with the boom. The hydraulic cylinders are located on each side of a vertical plane through the boom. A boom head (24) is universally pivotably mounted on the outer end of the boom (10) and it carries a feed beam (40) for a rock drill (41). The boom head is swingable by means of two hydraulic cylinders (27, 28) that are coupled between the boom and the boom head to form another tripod with the boom. These two tripods have similar geometry but the hydraulic cylinders of one tripod is located under the boom and the hydraulic cylinders of the other tripod is located above the boom.