Multi-stage compressor

A multi-stage compressor composing:

• two movement converting scotch yoke means driven by the same driving shaft for converting a rotating movement to a linear reciprocating movement;
• first, and second pistons connected to one of the two movement converting means in opposite directions for making linear reciprocating movements;
• and
• third, and fourth pistons connected to the other one of the two movement converting means in opposite directions and arranged at an angle to the first and second pistons for making linear reciprocating movements,
• wherein at least two of the first to fourth pistons are operative as first stage compression pistons, and at least one of the rest of the pistons are operative as a second stage compression piston, and
• wherein the scotch yoke means comprises:
• a crank shaft,
• a crank pin connected to the crank shaft so as to revolve around the crank shaft along a circular locus as the crank shaft rotates,
• a frame having one pair of sliding surfaces on parallel opposite inside surfaces thereof for fixing one or more than one piston to an outside of the sliding surface,
• a sliding block rotatably coupled to the crank pin and arranged between the one pair of sliding surfaces, having a surface facing the sliding surface sloped at an angle to the sliding surface,
• one pair of wedge members each having a surface opposite to the sliding surface and a sloped surface in surface to surface contact with the sliding block,
• one pair of self-lubricating members each attached to the sliding block so as to be in surface to surface contact with the sliding surface, and
• an elastic member having one end fixed to the wedge member and the other end fixed to a predetermined position for pressing the wedge member having the self-lubricating member attached thereto both to the sliding block and the sliding surface.