Passive dispenser

Claim 1

A non-siphoning passive dispenser for containing a quantity of a solution isolated from a body of liquid in which the dispenser is immersed and for causing a predetermined volume of said solution to issue from the dispenser solely under conditions of gravity flow in response to the level of said body of liquid being lowered from a first elevation to a second elevation, the dispenser comprising: a product reservoir containing a solute into which said liquid flows to form said solution when the level of said body of liquid rises from said second elevation to said first elevation, said quantity of solution being stored therein; venting means in fluid communication with said reservoir, and a discharge/refill conduit disposed below said venting means, said conduit connecting the reservoir with the body of liquid and comprising two chambers in fluid communication with each other, one chamber being adjacent to said reservoir to form an air trap chamber and the other chamber being adjacent to said body of liquid to form an air refill chamber, said air trap chamber and said air refill chamber having wall segments of equal length such that said solution issues from the dispenser due to non-siphonic flow; a transfer port connecting said air trap and air refill chambers, the cross-sectional area of said transfer port normal to fluid flow being smaller than the cross-sectional area of said air trap chamber normal to fluid flow such that air in said conduit is not completely displaced by said liquid when the level of said body of liquid rises from the second elevation to the first elevation, the air being entrapped in said air trap chamber and forming, upon cessation of flow into said reservoir, an air lock in said conduit which substantially isolates said solution from said body of liquid.