Roller pump carrying out alternate pumping operations, particularly suited to extra-corporeal blood circulation

A rotary roller pump for carrying out sequential pumping of fluid in a plurality of separate squeezable tubings, the pump comprising a plurality of tubings;

• a stator, having an inwardly facing seating and a rotor which is provided at opposite lateral ends with respective rollers, for engagement with the said tubings;
• a gap provided between said rotor and said inwardly facing seating of said stator, which seating partially surrounds said rotor, for accommodating said tubings which are arranged substantially parallel to each other and extend in a general circumferential direction;
• and wherein each said roller includes two cylindrical and coaxial parts having different diameters, each said cylindrical part having the larger diameter being engageable with a respective one of said tubings between that cylindrical part of larger diameter and the inwardly facing seating for exerting a pumping action on that tubing when said rotor rotates, and that each said cylindrical part having the smaller diameter being in supportive and non-pumping engagement with a different one of said tubings, which is adjacent that one engaged by said cylindrical part of larger diameter, the repsective positions of said rollers being reversed so that each of said tubings is engaged with a respective one of said cylindrical parts of larger diameter and a respective one of said parts of smaller diameter forming part of a different one of said rollers.