Patent ID: 8061218

Claim:
A fluid flow detector for detecting the flow of a fluid in a transfusion line, comprising: a detector main body defining a fluid flow channel having a circular cross section and comprising, an upstream hole formed at an upstream end of the detector main body, a downstream hole formed at a downstream end of the detector main body, a fluid flow detection channel positioned adjacent the upstream hole, a discharge channel positioned adjacent the downstream hole, and an intermediate flow channel provided between the fluid flow detection channel and the discharge channel; and a mobile body positioned within the fluid flow channel and dimensioned to be movable along the fluid flow channel in response to the flow of a fluid inside the fluid flow channel, and in which an outer peripheral edge part of a face of the fluid flow channel which is orthogonal to the direction of movement is formed to be circular; wherein the diameter of the fluid flow detection channel is smaller than the diameter of the discharge channel, and the maximum diameter of the outer peripheral edge part of the face of the fluid flow channel orthogonal to the direction of movement of the mobile body is set to be slightly smaller than the diameter of the fluid flow detection channel, and the upstream hole and the downstream hole are formed with a size and shape such that fluid can flow around the mobile body through the upstream and downstream holes; wherein the intermediate flow channel has a diameter that becomes steadily greater from the fluid flow detection channel towards the discharge channel; wherein the intermediate flow channel has a length in a longitudinal direction that is smaller than the diameter of the outer peripheral edge part of the mobile body; and wherein the fluid flow detection channel, the discharge channel, and the intermediate flow channel, are arranged in a straight line.