Physical Planning and Public Works

Fluids to be mixed and dispensed are metered out of hydraulic cylinders by movement of pistons therein. The rate of movement is controlled by movement of a recirculating ball nut connected to each piston rod, movement of the nut, in turn, being controlled by the rate of rotation of its ball screw. Each screw carries a gear, and the gears have a common drive so that the ratio of the diameter of the gears accurately controls the volumetric metering ratio of the cylinders. In one form, an inert fluid under pressure acting on the reverse sides of the pistons assists the force of the ball nut drive. In another form, two cylinders work as a pair on each fluid, inert fluid under high pressure acting on the reverse sides of the pistons of each pair to meter, mix and dispense the fluids at about two thousand to two thousand five hundred pounds per square inch.