Controlling flow in a medical injection system

A method for controlling flow in a medical injection system, the system including a pump having an inlet port and an outlet port, the outlet port being coupled to a first tubing line that is adapted to receive therethrough injections of fluid expelled from the pump, and the inlet port being coupled to a second tubing line that extends from a fluid reservoir for filling the pump, and the method comprising:

• positioning the first tubing line between a pinching member and a first anvil, the first anvil being at a first spring member, the first spring member comprising an elongate flexure having a length between a fixed first end and a floating second end that includes the first anvil, the length extending along a first elongate flexure central longitudinal axis that does not intersect the pinching member, the first spring member having a pre-load deflection established by a first pre-load support located between the fixed first end and the floating second end;
• positioning the second tubing line between the pinching member and a second anvil, the second anvil being at a second spring member, the second spring member comprising an elongate flexure having a length between a fixed first end and a floating second end that includes the second anvil, the length extending along a second elongate flexure central longitudinal axis that does not intersect the pinching member, the second spring member having a pre-load deflection established by a second pre-load support located between the fixed first end and the floating second end;
• and
• moving the pinching member from a first position, at which the pinching member compresses the first tubing line against the first anvil, to a second position, at which the pinching member compresses the second tubing line against the second anvil.