Blood pump system

In a pump comprising an arcuate bearing surface adapted to carry a flexible tube through which fluid may pass, a pair of 180.degree. spaced-apart, pivotally-mounted rollers whose axes travel along a circular path concentric with said bearing surface whereby said rollers occlude the tube so as to pump the fluid therethrough, means for rotating said rollers around said circular path, and lead ramps extending from each end of said bearing surface, the improvement wherein:

• said bearing surface defines an arc of approximately 168.degree. and each of said lead ramps is substantially tangent to the end of the bearing surface from which said respective lead ramp extends so as to provide the optimal torque peak reduction for driving said pump, and the optimal graduated change in cross-section of the bore of the tube as each of said rollers approach and recede from the points of occlusion of the tube;
• and further comprising means located radially with respect to the axis of rotation of said rotating means independently operable with respect to each of said rollers for independently and precisely varying the extent to which each of said rollers occludes the tube, including means for continuously adjusting the radial deflection of each roller as it occludes the tube so as to provide proper occlusion despite tube irregularities while allowing for varying the rate of change of radial force applied to each of said rollers, said means for varying the extent to which each of said rollers occludes the tube comprising two separate arms, each of said arms carrying one of said rollers, said continuously adjusting means comprising a separate thumb wheel threadedly connected to each of said arms, each of said thumb wheels having a neck portion, and compression spring and an elastic sleeve concentrically located around said neck portion, said spring being spaced from said sleeve and said sleeve being located within said spring and supported by said neck portion.