Tandem rotary pump with pressure chamber between two intermediate side plates

A tandem pump, comprising:

• a pump housing in which a hollow chamber, first and second suction passages and first and second discharge passages are formed, said first and second discharge passages communicating with respective different fluid equipment;
• a rotating shaft rotatably supported in said pump housing and positioned at one end in said hollow chamber;
• first and second rotors which are axially movably connected in two places in the axial direction on one end of said rotating shaft and rotatable as one body;
• one side wall of said first rotor being in contact with one of said walls of said hollow chamber;
• said rotors being each provided with vanes radially moving outward with rotation within respective containing chambers formed at a plurality of positions in the circumferential direction on the outer peripheral surface of said rotors;
• first and second cam rings which are so disposed that a cam face formed on the inner pheriphery faces the outer peripheral surface of each of said rotors, drawing a fluid from respective suction passages into an inside space defined by said vanes moving outwardly and delivering an increased pressure to respective discharge passages, and one side of said first cam ring being in contact with one of said walls of said hollow chamber;
• an intermediate side plate movable in the axial direction of said rotating shaft which is positioned between said first cam ring said second cam ring, said intermediate side plate being constituted of first and second side plates which are in contact with each other on their one side, and the other side of said first side plate being contact with the other side of said first rotor and said first cam ring, while the other side of said second side plate being in contact with one side of said second rotor and said second cam ring;
• and a recess serving as a pressure chamber which is formed in the inner peripheral surface of at least one of said one sides of said first and second side plates;
• a rear side plate which is mounted movable in the axial direction of said rotating shaft, in contact with the other side of said second cam ring and said second rotor, forming enclosed first and second fluid chambers between said rear side plate and the other wall of said hollow chamber;
• a first fluid introducing passage which leads a part of the pressure fluid discharged from one of said first and second cam rings into said pressure chamber;
• a second fluid introducing passage which leads a part of the pressure fluid discharged from said first cam ring into said first fluid chamber;
• and
• a third fluid introducing passage which leads a part of the pressure fluid discharged from said second cam ring into said second fluid chamber.