Abstract: A compact and highly reliable proportioning pumping system for supplying a precise and controllable mixture of concentrate and water in a kidney dialysis machine comprises a central body and a pair of oppositely mounted pivotable linkages coupled to the body. A first pivotable linkage is coupled by connecting rods to a water metering piston and a concentrate metering piston respectively, a variable stroke ratio being provided by a signal actuated drive coupled to the linkage mechanism and controlling the relative position of the end of one of the connecting rods. The change of position is advantageously effected so as to maintain a precise proportionality between the flows delivered by each of the pistons throughout their variable stroke lengths. The range of proportioning adjustments can be mechanically limited and alarm conditions can readily be detected.

Abstract: A medical instrument, specifically shown as a dialysis machine, incorporates an electrically isolated and hermetically sealed high thermal flux heater in conjunction with means for vectorially cancelling alternating current signal components generated in the operation of the machine. Because of electrical coupling between the medical instrument and a human patient blood stream, large ground leakage currents can result in electrical shock for a patient if the ground wire of the machine becomes open circuited. However, the combination of a specially modified dialysate fluid heater with an extremely large and dependable isolation resistance and operating mode dependent vectorial compensation for resistive and capacitive leakage current permits total leakage current from chassis to ground to be brought below a hitherto unattainable 1 microamp level.

Abstract: A system for continuously removing gases from a liquid initially subjects the liquid to a pressure drop and then injects the liquid into a toroidal chamber in which it is impelled into a hollow annular flow path of high surface area and velocity. The liquid is forced helically about the annulus to create internal cavitation, and entrained and dissolved gases are removed both during injection and cavitation by a suction vent at an interior region of the toroidal flow chamber. Liquid is ejected from the periphery of the toroidal chamber into the bottom of a settling chamber, also maintained under vacuum, such that gases rise to another suction vent at the top of the chamber. Degassed liquid in the settling chamber moves under gravity into the orbit of an adjacent centrifugal pump and is continuously fed out from the system into ambient pressure by a positive drive pump.

Abstract: The conductivity of an electrolytic solution is determined with accuracy and sensitivity by measuring the conductance along extended paths of small cross-sectional areas between large area electrodes. Current flow is thereby measured with minimization of distortion effects created by electrolytic depositions or other form of electrode surface contamination. Further, sensitivity and reliability are enhanced by employing conductivity cell sections as variable resistance arms in a bridge excited with an extremely low voltage, low duty cycle AC signal which is filtered and synchronously demodulated to provide the desired conductivity measurement.