Blood collection bag weighing device

Claim 1

A blood collection bag weighing device for filling a blood collection bag with a predetermined weight of blood flowing from a tube extending from the vascular system of a donor, said device comprising in combination: (a) means for clamping the tubing, said clamping means including a member for embodying stored potential energy when positioned in a retained state and for clamping the tube when positioned in a clamping state, said member including a planar surface and means for exerting a first magnitude of force against retention in the retained state and a second magnitude of force for clamping the tubing in the clamped state, which second magnitude of force is substantially greater than the first magnitude of force; (b) a permanent magnet for overcoming the first magnitude of force to magnetically capture and retain said member in the retained state, said magnet including a straight edge and movable mounting means for accommodating realignment of said magnet to position said straight edge of said magnet in aligned contacting relationship with said planar surface of said member and maximize the magnetic coupling therebetween; (c) means for momentarily disrupting the magnetic field of said magnet to a value insufficient to overcome the first magnitude of force and independent of the magnitude of the second magnitude of force and permit repositioning of said member from the retained state to the clamping state in response to said exerting means; (d) means for sensing achievement of the predetermined weight by the blood collection bag during the filling of the blood collection bag; and (e) means for generating an electrical signal in response to said sensing means to energize said disrupting means; whereby, the energy level of said magnet and of said generated electrical signal may be unrelated to the level of energy of the second magnitude of force to clamp the tubing.