Metering and mixing liquids in fixed proportions - by magnetic floats rising with liquids in intermediate vessels

摘要

Measured amts. of a number of liq. components fed by gravity from individual vessels with inlet and outlet valves into a collector are controlled by magnetic annular floats which move concentrically along the outside of a sealed tube inside the vessel. At intervals up the tube wall interior are reed contacts whose output signals as the float passes them control the various stages of admitting liq. and discharging it into the collector, with the level of each contact inside the measuring vessel determining tha amt. of that component present when a 'ready' signal is actuated preparatory to discharge. Each tube can have several reed contacts, permitting programming of different mixt. ratios. Suitable for large vol. or repeated mixing, esp. of dangerous liqs. eg. mixtures of hydrofluoric, hydrochloric and acetic acids for etching silicon semiconductor dice, and does not involve pressurising such liqs. as did known devices using controlled numbers of pumping strokes for each liq.