Abstract: A hydraulic apparatus is shown for moving a heavy load along an I-beam shaped structural member comprising a releasable clamping assembly and a double acting hydraulic jacking cylinder. The releasable clamping assembly includes a ramp plate, a pair of ramp mating members and a pair of jaw members having a cavity defined by opposed sloped walls having a bearing surface which cooperate with a ramp plate and ramp mating members causing the gripping surface of the ramp plate and ramp mating members to engage the flange of an I-beam. The releasable clamping assembly transmits a thrust load from a jacking cylinder thrust to the jaw member which reacts to apply a clamping force to the ramp plate and ramp mating members such that a thrust load away from direction of load travel will result in the ramp plate and the pair of ramp mating plates being urged towards each other to grip the flanged surface of the I-beam and arrest the motion of the jacking cylinder relative to the I-beam.

Abstract: A jacking apparatus comprises a rail having a plurality of pairs of vertical slots longitudinally spaced apart. A sled slides along this rail and has cross members to which are pivotably attached ends of hydraulic cylinders, the other ends of the hydraulic cylinders being pivotably attached to cross heads which also slide along the rail. The cross heads have bevelled latches, slidable vertically, and longitudinally reversible for engagement with the slots in the rail; so that repetitive, reciprocal movement of the hydrauic cylinder pistons will cause successive, incremental movements of the sled and a load selectively pushed or pulled by the sled along the rail.

Abstract: A jacking apparatus comprises a rail with an attached vertical rack having teeth with a steep front face and a sloping back. A notch is arranged in the back of each of the rack teeth. A pair of cars are slidably mounted on the rail with each car carrying a pair of latches, one of which is engageable with the front face of a rack tooth and the other with the notch in the back of that tooth. Reciprocal motion, away from and toward each other, is imparted to the cars while the latches selectively engage teeth in the rack to cause progressive incremental travel of the cars along the rail, to move a load attached to one of them.

Abstract: A ship lifting apparatus, or drydock, is formed by a pair of parallel, spaced apart piers which define a slip in which is located a platform on to which a ship can be floated. The platform is raised or lowered by a plurality of chain jacks mounted in aligned rows on each of the piers. One of the chain jacks is a master jack and has chain link-engaging latches controlled by a cam and follower while the other chain jacks are slave jacks being actuated by connection to each other and the master jack by tensioned cables attached to their latch actuating mechanisms.