A boom for a pipelaying machine includes a pair of posts located in a first plane and disposed in a tapered configuration with respect to a second plane transverse to the first plane. The boom also includes a cross-brace disposed between the pair of posts and located partway along a length of the pair of posts. The cross-brace includes a first link member and a second link member disposed along the first plane. Further, each of the first and second link members are angularly offset from each other and the second plane respectively. Furthermore, ends of the first and second link members are rigidly attached to the pair of posts. The cross-brace further includes a first rib member and a second rib member disposed along the second plane and rigidly attached to the first link member and the second link member respectively.

A crane includes a base, an upperstructure rotationally mounted on the base, a boom, and a gantry. The boom is pivotally attached to the upperstructure at a front attachment location and supports a load line operable to raise a payload. The gantry is mounted on the upperstructure and supports a boom line coupled to the boom. The gantry includes at least one front leg mechanically coupled to the front attachment location and inclined away from the boom to apply, to the front attachment location, a horizontal force component towards the boom opposed by a horizontal force component applied by the boom towards the front leg. The upperstructure includes a frustoconical turret forming an upper circle and a lower circle. The front attachment location is aligned over the upper circle of the frustoconical turret.

The invention related to a concrete-pump boom-arm segment having an upper chord (33), a lower chord (34) and two lateral parts (35, 36) which connect the upper chord (33) and the lower chord (34). The boom-arm segment comprises a longitudinal connection (44) between two subregions (41, 42) of the boom-arm segment which adjoin one another in the longitudinal direction, wherein the longitudinal connection (44) extends over a chord portion (56, 66) and over a lateral part portion (53, 63). The lateral part portion (53, 63) is bent over with respect to the chord portion (56, 66) in the first subregion (41) and in the second subregion (42). The material thickness of the chord portion (56) is greater in the first subregion (41) than the material thickness of the chord portion (66) in the second subregion (42). The invention additionally relates to a method for producing such a boom-arm segment. Such a boom-arm segment is well suited for absorbing static and dynamic loads and can be produced in a cost-effective manner.

A rotary tower crane with a tower, which carries a jib and a counterjib, with a jib stay being guided from a tower top to the jib and to the counterjib. The jib stay tensions only an inner jib portion, the length of which is less than 40% of the total length of the jib, and an outer portion, the length of which is more than 60% of the total length of the jib, forms an untensioned bending beam jib which includes at least one jib piece which tapers in height and which is adjoined on the inner side by at least one jib part of greater height and on the outer side by a jib piece of smaller height.

A rotary tower crane with a tower, which carries a jib and a counterjib, with a jib stay being guided from a tower top to the jib and to the counterjib. The jib stay tensions only an inner jib portion, the length of which is less than 40% of the total length of the jib, and an outer portion, the length of which is more than 60% of the total length of the jib, forms an untensioned bending beam jib which includes at least one jib piece which tapers in height and which is adjoined on the inner side by at least one jib part of greater height and on the outer side by a jib piece of smaller height.

An upper turning body mounted on a lower body for a crane includes a turning frame mounted on the lower body to turn freely, and a boom provided to the turning frame to be raised and lowered freely. The turning frame includes a pair of attachment brackets to which a base end section of the boom is attached such that the boom is free to be raised and lowered, and a frame body to which the pair of attachment brackets are provided with an interval in a left-right direction of the upper turning body. The frame body is formed of a plurality of divided frames arranged side by side in the left-right direction of the upper turning body, adjacent divided frames of the plurality of divided frames being separably joined to each other.

An upper turning body mounted on a lower body for a crane includes a turning frame mounted on the lower body to turn freely, and a boom provided to the turning frame to be raised and lowered freely. The turning frame includes a pair of attachment brackets to which a base end section of the boom is attached such that the boom is free to be raised and lowered, and a frame body to which the pair of attachment brackets are provided with an interval in a left-right direction of the upper turning body. The frame body is formed of a plurality of divided frames arranged side by side in the left-right direction of the upper turning body, adjacent divided frames of the plurality of divided frames being separably joined to each other.

A boom, of a machine, may include a first member; a second member opposite the first member; and a support structure. The support structure may comprise a first support member; a second support member; and a third support member. The first member, the first support member, and the second support member may define a first opening. The second member, the second support member, and the third support member may define a second opening. A first area of the first opening may exceed a second area of the second opening.

A boom, of a machine, may include a first member; a second member opposite the first member; and a support structure. The support structure may comprise a first support member; a second support member; and a third support member. The first member, the first support member, and the second support member may define a first opening. The second member, the second support member, and the third support member may define a second opening. A first area of the first opening may exceed a second area of the second opening.

There is provided a crane including a main body, a tower derrickably supported by the main body, a jib derrickably supported by the tower, an assist member that assist the jib to move along a ground, and a determination unit that determines whether or not the jib is stopped when the tower is lowered in a lowering work state where the jib is assisted by the assist member.