Abstract: A low-shear valve for controlling fluid flow through a conduit does not change the volume of the fluid that it controls when it is actuated between its open and closed positions.

Abstract: A multiple pumping chamber pump in which the pressures in at least two of said chambers are equal for at least a portion of their pumping cycles, maintains a constant flow of pumped material by utilizing control means that selectively and continually replaces one material pumping chamber with another after the pressures in both of said chambers have equalized and after the outputs of said chambers have been connected to a common output conduit, by gradually and simultaneously causing a decrease in the pumping rate of material from one of said compression chambers and, to the same extent, a corresponding increase in the pumping rate of material from another of said chambers until the material pumping rate from one of said chambers is reduced from its normal pumping rate to zero and the pumping rate from the other of said chambers has been increased to the said normal pumping rate from the said chamber that had its flow rate reduced to zero.