Blood transfusion apparatus

Claim 1

Device for pumping fluid through a flexible tube at a controlled rate, which device comprises a wheel, a plurality of rollers mounted to rotate freely about equidistant points on said wheel while projecting radially from the periphery of said wheel, a casing in which said wheel is rotatably mounted, an opening in said casing positioned radially of said wheel, a pressure member slidably mounted in said opening and having a surface adjacent the periphery of said wheel, said casing, wheel and surface defining a passage for the reception of said flexible tube which traverses an arc of substantially less than 180° between said wheel and surface and leads from one side of said casing to its opposite side and through which the fluid within said tube is advanced when rotation of said wheel advances said rollers through said passage, a motor driving said wheel, a dropping chamber through which fluid in said tube flows, and means responsive to the passage of fluid drops through said dropping chamber to control the speed of said motor, said device further comprising in combination: means resiliently biassing said pressure member toward said wheel, and a plurality of recesses within said pressure member, which impart elasticity thereto, said pressure member surface being divided into successive entrance, central and exit portions, each portion being substantially part-circular in section, and those ends of the entrance and exit sections which are remote from said central section begin likewise more remote from the center of curvature of said central section.