Abstract: In the construction of tall concrete towers, a two part derrick is suspended by cables from the tower to the lower part of the derrick. The derrick is extended on hydraulic rams, raising its upper part and outside casting forms. A pulley system maintains a deck scaffold and inside forms at their original level during extension. Extension of the derrick slakens cables from the tower to the upper part of the derrick. These cables are disconnected from the tower and reconnected at a higher level. Outside forms are fixed, reinforcing steel set in place, and the derrick retracted, raising the deck scaffold and inside forms by the pulley system, and slacking the lower cables. The lower cables are disconnected from the tower and reconnected at a higher level. Inside forms are set and concrete is poured. The concrete sets and the procedure is repeated.The deck scaffold comprises radiating wooden beams with endpieces.

Abstract: A jacking apparatus for selectively moving a load in either of opposite directions such as vertically upwardly and downwardly. The apparatus is adapted for use in a wide range of building constructions, such as those using slipforms, wherein heavy loads are positioned by the jacking apparatus. The apparatus includes gripping elements having portions engaging elongated structural elements for effecting desired movement of the jacking apparatus in moving the load. The gripping elements are mounted on parallelogram linkage supports for maintained parallel relationship to the longitudinal extent of the elongated structural element with which they are selectively engaged. A control device is carried by the respective upper and lower gripping devices for effecting automatic control of the gripping elements in effecting a lowering of the apparatus when desired.

Abstract: A jacking device for use with a thread bar having a plurality of couplers and nuts spaced longitudinally thereon. The jacking device is arranged to permit movement thereof longitudinally past the respective couplers and nuts while permitting utilization of the nuts by threaded movement thereof on the thread bar for supporting different portions of the jacking device relative to the thread bar in effecting the desired jacking operation. The jacking device may be utilized to climb the thread bar and, alternatively, may be utilized to pull the thread bar and lift a load associated therewith. The jacking device includes biased chuck elements movably carried to permit passing of the couplers and nuts and selective support thereof on the nuts in effecting the controlled jacking operation.