Patent ID: 6883960

Claim:
A mixing arrangement for a closed-tank mixing system including a tank defined by a side wall, a bottom and a top, the top including at least one opening therethrough, the arrangement comprising: a non-rotating elongated arm extending through the opening in the top of the tank, the arm pivoted for movement about a pivot axis; an impeller positioned on the arm for movement therewith and within the tank, the impeller moving back and forth along an arcuate path within the tank as the arm pivots back and forth about the pivot axis, wherein the impeller is configured to produce a net circular flow within the tank about an axis normal to the opening in the top of the tank when the impeller is moved back and forth alone the arcuate path; and a flexible seal arrangement exterior of the opening and positioned about the arm and including a flexible seal having a first continuous edge held between spaced apart support surfaces and a second continuous edge held between spaced apart support surfaces, the flexible seal arrangement enclosing contents within the tank.