Abstract: The invention disclosed relates to the art field embracing positive displacement reciprocating compressors of the type featuring hydraulic drive, and sets out to simplify the construction of such units, rendering them more functional at the same time. Four coaxial bulkheads are adopted, set apart one from the next by three cylinder barrels, and three pistons which are mounted to a common rod and reciprocated thus, each in its respective barrel; the central piston and barrel are of either greater or smaller diameter than the remainder. Hydraulic oil from a power pack driving the compressor flows alternately into chambers which are occupied by the rod, and bounded at one end by one of the pistons of smaller or greater diameter.

Abstract: A multi-stage, reciprocating, positive displacement compressor, in which the various stages are coaxial one with the other. The compressor has a double acting, monorod, hydraulic jack and at least one piston guided to slide hermetically in a cylindrical chamber that is fixed to the support structure of the compressor; a cylindrical tubular liner that is fixed coaxially, at one extremity, to the aforementioned piston and points towards the jack. The cylindrical chamber is sealed, at the extremity pointing towards the jack, by a guide ring for the liner and, at the other extremity, by a disk. The piston and the cylindrical liner define in the cylindrical chamber the first and the second stage in the compressor. Third and fourth stages of the compressor are formed in a second cylindrical chamber coaxial with the first chamber and secured to the disk sealing the first chamber.