Abstract: Impeller means (4 and 5) is provided in a container (2) for agitating fluid. The impeller means is movable to effect fluid flow. The impeller means includes an impeller (4) which is separate from a wall portion of the container to a point of which the impeller (4) is connected by supporting means (5). Movement of the impeller means relative to the wall portion is achieved by making the impeller means flexible. A vibrator (6) may be provided to cause movement of the impeller means. The characteristics of the components can be chosen so that when the vibrator is activated the impeller vibrates with a greater amplitude than the wall portion (3). This can be achieved by vibrating the wall portion at a frequency approximately equal to a resonant frequency of the impeller means.

Abstract: A mixing apparatus includes two compartments which are interconnected by conduits of two different types. The conduit or conduits together of the first type present a lower resistance of flow from one compartment to the other than do the conduit or conduits together of the second type. The conduit or conduits together of the second type present a lower resistance to flow from the other compartment to the one compartment than the conduit or conduits of the first type. Fluid is caused to flow between the compartments through the noted conduits. A method includes providing apparatus as above-described and causing fluid to flow between compartments.

Abstract: An impeller on a stirrer shaft is rotated at constant angular velocity by a motor within a chamber. Vibrations induced in the shaft by virtue of the stirring action of the impeller are sensed by a transducer whose output is conditioned by equipment from these signals. The invention can be applied to processes in a reaction vessel and liquid in a pump chamber. Since the excitation is a constant angular velocity and the induced effect is vibration, there is no interference between excitation and induced effect although the transducer is mounted on the stirrer shaft.