A flexible coupling includes an input coupler including an inner face, an output coupler including an inner face, and a plurality of rigid linkages. Each rigid linkage is coupled between an input attachment point coupled to the inner face of the input coupler and an output attachment point coupled to the inner face of the output coupler. Each rigid linkage is pivotably and slidably coupled to the input attachment point and the output attachment point.

A flexible coupling includes an input coupler including an inner face, an output coupler including an inner face, and a plurality of rigid linkages. Each rigid linkage is coupled between an input attachment point coupled to the inner face of the input coupler and an output attachment point coupled to the inner face of the output coupler. Each rigid linkage is pivotably and slidably coupled to the input attachment point and the output attachment point.

A cup member has a cylindrical portion, a bottom portion, and a short shaft portion having a solid shaft shape and including a joining end surface at an end portion thereof. A shaft member has a solid shaft shape and includes a joining end surface at one end thereof. The joining end surfaces of the cup and shaft members are brought into abutment against each other and welded from a radially outer side to form a welded portion. At this time, center segregation is prevented from interfering with the welded portion. The cup member is formed by forging including upsetting a billet having a columnar shape successively in a plurality of stages, extruding the cylindrical portion and the short shaft portion, and ironing the cylindrical portion. In the course of the upsetting, a region of the billet corresponding to a bottom side of the cup member is narrowed.

A cup member has a cylindrical portion, a bottom portion, and a short shaft portion having a solid shaft shape and including a joining end surface at an end portion thereof. A shaft member has a solid shaft shape and includes a joining end surface at one end thereof. The joining end surfaces of the cup and shaft members are brought into abutment against each other and welded from a radially outer side to form a welded portion. At this time, center segregation is prevented from interfering with the welded portion. The cup member is formed by forging including upsetting a billet having a columnar shape successively in a plurality of stages, extruding the cylindrical portion and the short shaft portion, and ironing the cylindrical portion. In the course of the upsetting, a region of the billet corresponding to a bottom side of the cup member is narrowed.

Delivering a blood processing solution to blood in a blood bag includes coupling a first tube to a vented spike at one end and to a Y-shaped tube connector at a second end. An in-line microbiotic barrier filter is coupled to the first tube between its ends. A second tube is coupled to a transfer bag at one end and to the Y-shaped tube connector at its other end. A third tube is coupled to the output of the Y-shaped tube connector and sealed at its distal end. The blood bag includes a fourth tube that is sealed at a distal end. The third tube is welded to the fourth tube using a sterile tubing welder, wherein a functionally-closed, sterile flow path through which the blood processing solution can flow into the blood bag is maintained.