Abstract

Apparatus for accurately proportioning and mixing fluids comprising a double acting piston/cylinder unit of which the cylinder is divided into two chambers by the piston and the volume of the cylinder swept by the piston at one end of the piston is lesser than that at the other end. An inlet connection for a first fluid is made to one chamber, a conduit connects the two chambers and includes a connection to a source of the second fluid. Valve means are associated with the conduits and are effective to cause a charge of first fluid to be delivered to said one chamber and thereafter to be transferred to the other chamber drawing fluid from said source of second fluid to make up for the difference in the volumes of the chambers. Said valve means then cooperate to cause the mixed fluids to be discharged from the other chamber as said one chamber is again charged with said first fluid. In a variant of the invention the piston/cylinder unit is replaced by a receptacle within which is disposed a diaphragm the diaphragm serving to divide the receptacle into two chambers. In other variants means are provided for varying the ratio of first to second fluid in the mixture and in still other variants the second fluid is made up of components of two or more fluids the ratios of those components being adjustable.