US 2837111,Mueller, Paul G.,「Ball cock valve mechanism」,发表于6 January 1955,发行于3 June 1958; hysterisis issue. "Such flush tank valves as now commonly used are closed against the pressure of water from a source of supply which pressure opposes the movement of the float under rising water level in the tank. This results in a slow or delayed movement of the valve preliminary to its reaching its fully closed position and accordingly develops an objectionable hissing sound due to the discharge of water through the then slightly open valve under full water pressure; this delayed action continuing until the slowed delivery of water to the tank finally raises the water level to a point where the float will be effective in fully closing the valve. This action of the conventional float controlled valves frequently gives rise to a condition where full closing of the valve does not occur with a consequent continuous leakage of water through the valve with a resulting waste of water."
US 418162,Cahill, W. J.,「Ball cock」,发表于2 October 1889,发行于31 December 1889; hysterisis issue.
