Jacking apparatus

Claim 1

Jacking apparatus having a plurality of hydraulic cylinders arranged to move a load along a rail; in which the improvement comprises: a. a rail having a plurality of pairs of vertical slots uniformly spaced along the length of said rail, said slots in each pair being transversely aligned; b. a sled comprising a pair of spaced apart side members pivotably connected to a plurality of spaced apart cross members slidably mounted on said rail; c. a plurality of cross heads slidably mounted on said rail, each of said cross heads being spaced apart from an adjacent sled cross member; d. hydraulic cylinders pivotably attached between the outer ends of each of said cross heads and the said adjacent sled cross members; e. a pair of transversely aligned latches having longitudinally bevelled bottom surfaces mounted in each of said cross heads so as to be vertically slidable and engageable with said slots in said rail; f. means for maintaining said pair of latches in each of said cross heads in transverse alignment with said pairs of slots in said rail; g. means for causing simultaneous alternate retraction and extension of the piston rods of said hydraulic cylinders, thereby to cause repetitive, incremental movement of said sled along said rail by engagement of said latches with said slots in said rail when said cross heads are moved by said hydraulic cylinders in one direction with respect to said sled, and sliding of the bevelled bottom edges of said latches over edges of said slots in said rail when said cross heads are moved by said hydraulic cylinders in the other direction with respect to said sled; and, h. means on an end of said sled for engaging a load to be moved along said rail.