Blood pump

Claim 1

A blood pump comprising: an elongated flexible tube defining a flow path for the blood; inlet valve means for selectively restricting flow through said tube at a first longitudinal position along said tube, said inlet valve means comprising a first flat-surfaced plunger valve and a first fixed flat wall portion disposed in movable spaced relation on opposite sides of said tube at said first position; outlet valve means for selectively restricting flow through said tube at a second longitudinal position along said tube, said outlet valve means comprising a second flat-surfaced plunger valve and a second fixed flat wall portion disposed in movable spaced relation on opposite sides of said tube at said second position; displacement means comprising a third plunger valve and a third fixed wall portion disposed in movable spaced relation on opposite sides of said tube at a third position intermediate said first and second positions; actuator means for selectively actuating said first, second and third plungers for movement toward and away from said first, second and third wall portions, respectively, in a prescribed sequence so as to sequentially restrict said tube at said first, second and third positions; and adjustment means for limiting the restriction of said flow tube at least at one of said first and second positions by adjusting said spaced relation of at least one of said first and second fixed flat wall section such that a passage for blood flow through said tube is provided when the tube is in its most restricted condition at said at least one position, said passage having a length in the flow direction of at least 5 mm and having a restriction height of less than 0.5 mm.