Abstract: A stirring blade includes a first member having a first flat surface and a second member having a second flat surface, wherein the stirring blade is rotatable about a rotational axis in a state where the first and second flat surfaces are opposed to each other and spaced by a first distance across the rotational axis. When the stirring blade is rotated about the rotational axis with the first and second flat surfaces at least partially immersed in an object to be stirred, the object to be stirred having entered between the first and second flat surfaces is discharged in a direction away from the rotational axis by a centrifugal force and, simultaneously, the object to be stirred is sucked into and between the first and second flat surfaces from a direction along the rotational axis.

Abstract: An adapter for a dispensing container in a planetary mixer and an adapter and dispensing container combination are provided. The container has a longitudinal axis and a transverse axis and includes a composition dispensing nozzle with a removable cap closing the dispensing nozzle, the removable cap having a first width dimension measured along the transverse axis, and a container part spaced apart from the dispensing nozzle along the longitudinal axis, the container part having a second width dimension measured along the transverse axis. The adapter includes a cavity for receiving the cap, the cavity having a transverse dimension that exceeds the first width dimension, and a passageway extending from the cavity for receiving the container therein, the passageway having a transverse dimension that is less than the first width dimension and less than the second width dimension.

Abstract: A bushing for a foam mix-head includes an injection port wall surrounding a vestigial area for foam accumulation, a substrate opening transition segment configured to be situated with an opening of a substrate, a seal housing, and a seal seated in a seal seat of the seal housing. The seal helps prevent leakage during a foaming operation, such as when manufacturing a vehicle interior panel having a foam layer between a skin layer and a substrate.

Abstract: Method and device for metering a medium from at least one storage tank by a metering device, which has a piston pump, which defines a working chamber with a cylinder and a piston, wherein in a first method step a determined filling quantity of a medium is conveyed via an inlet valve into the working chamber and the determined filling quantity is greater than the quantity to be metered and, in a second method step, the piston reduces the working chamber in size enough that only the quantity to be metered remains, wherein the excess medium flows out of the working chamber, wherein the excess medium flows via the inlet valve back into a ring line, which is connected in a medium-conducting manner to the storage tank and is arranged outside the working chamber.

Abstract: A method of mixing in a discharge conduit, in a turbine engine with two or more flows, of a primary flow and a secondary flow, the two flows emerging in the discharge conduit by two coaxial ducts, separated by an internal housing which has an end downstream relative to the flow direction of the flows, the two coaxial ducts each being defined between an internal wall and an external wall, upstream of the downstream end of the internal housing, and the secondary flow surrounding the primary flow, is provided. The method includes disposing a divergent radial deflection device in the primary duct, spaced apart from the walls of the primary duct. A turbine engine including the deflection device is also provided.

Abstract: A magnetic drive system comprising three members, a first and second of which form an input member and an output member each arranged to rotate relative to the third member, wherein two of the members have respective sets of permanent magnets, the two sets having different numbers of magnetic poles, and the other of the members comprises a cylindrical body having a plurality of pole pieces embedded therein, the pole pieces being arranged to modulate the magnetic field acting between the magnets, and wherein one of the pole pieces is of varying radial thickness.

Abstract: A swirler including an annular housing with limiting walls. At least two vanes are arranged in the annular housing including the sidewalls of the swirler. The leading edge area of each vane has a profile, which is oriented parallel to a main flow direction prevailing at the leading edge position, wherein the profiles of the vanes turn from the main flow direction prevailing at the leading edge position to impose a swirl on the flow, and wherein, with reference to a central plane of the vanes the trailing edges are provided with at least two lobes in opposite transverse directions. A burner for a combustion chamber of a gas turbine including such a swirler and at least one nozzle having its outlet orifice at or in a trailing edge of the vane and to a method of operation of such a burner.

Abstract: The invention relates to an impeller for use in a bioreactor for growing adherent mammalian cells and/or a cell separator for adherent mammalian cells. The impeller of the invention is designed to efficiently and rapidly lift a bed of settled cells and microcarrier beads at low rotational speeds. Cell growth and concomitant yield is therefore improved by maintaining the culture in an environment of low shear force.

Abstract: A system for mixing a fluid in a tank includes a mixer assembly, a housing, and an actuator. The mixer assembly has a motor, a shaft, and an impeller. The housing is disposed in a side wall of the tank. The housing has sufficient volume to contain the impeller. The actuator is configured to retract the mixer assembly and draw the impeller into the housing. The mixer assembly has a first conformation and a second conformation. In the first conformation the impeller is disposed in a main portion of the tank and configured to mix the fluid in response to rotation of the impeller via the motor and shaft. In the second conformation the impeller is disposed in the housing and out of the main portion of the tank.

Abstract: A method and apparatus for dispersing and entraining and controlling the residence time, absorption and release of gas bubbles or particles in a fluid without losing gas utilization efficiency from escaping surface gas events. A mechanical, rotating plurality of hollowed blades that induce both an axial and radial controlled circulatory flow and provide a means of gas introduction into the discharge flow that has a conical helical, axial and radial outward flow from the axis of rotation and allows entrained gas bubbles to be trapped as particles and recirculated by means of a circulatory flow back into the intake vortex of said mechanical, rotating plurality of blades. The flow is characterized by a forced intake vortex caused by a low pressure zone with a radial component, and subsequent axial component drawing fluid in a circular fashion toward the eye of the rotating device and impelling fluid.

Abstract: Apparatus and methods for a mixing device are presented. The mixing device comprises a shaft and a plurality of blades attached to the shaft. The blades include a variable pitch angle configured to create axial fluid flow and radial fluid flow within a container. The apparatus includes a hub and a cage located at ends of the apparatus. The cage includes an open end configured to mate with a structure attached to the container. In further examples of the apparatus, the upper blade is configured to create axial flow in a substantially downward direction. The lower blade is configured to create axial flow in a substantially upward direction. The lower blade can create an axial flow that encounters the upper blade. A method includes locating a mixing apparatus within the container, inserting fluid within the container, rotating the mixing apparatus, and mixing the fluid.

Abstract: In this disclosure, a method is described wherein the method comprises mixing a therapeutic gas or a therapeutic liquid or a combination thereof and a liquid carrier in a high shear device to produce a dispersion; and administering the produced dispersion intravenously to a patient; wherein the produced dispersion contains nanobubbles of the therapeutic gas or droplets of the therapeutic liquid with a mean diameter of less than about 1.5 ?m. In this disclosure, a system is also described wherein the system comprises a therapeutic gas source or a therapeutic liquid source or a combination thereof; a liquid carrier source; a high shear device (HSD) having an inlet, an outlet, at least one rotor, and at least one stator separated by a shear gap; and a pump configured to control the flow rate and residence time of a fluid passing through the high shear device.

Abstract: A device for accelerating mixing and dissolving processes of liquid water and powder. The device includes a main body formed in a bottle cap shape including a top surface and a side periphery surface, and a shaft disposed at a center of an upper portion of the main body in such a manner as to be inserted into a shaft insertion groove formed at a center of an impeller. The top surface of the main body has two or more introducing portions to introduce the liquid water and the powder into the device, and the side periphery surface of the main body has two or more discharging portions to discharge the liquid water and the powder introduced into the device through the two or more introducing portions to the outside of the device.

Abstract: A device and method prevents freeze over of a fishing hole cut through a layer of ice overlying a body of water. The device has a housing; a motor; at least one water inlet in the housing; at least one water outlet in the housing; and at least one water-moving element driven by the motor and moving water out of the at least one water outlet. The device may spin within the hole and stir water to prevent too rapid ice buildup.

Abstract: A device for mixing a pulp- and/or fiber-containing fluid which comprises an apparatus for moving the fluid free from shearing, and a corresponding method.

Abstract: Provided is a microfluidic mixing system comprising a loop system for transferring one or more fluids, wherein the loop system comprises a plurality of sub loops, each sub loop formed from one or more common channels shared with at least one other sub loop and completed by an outer channel portion that is not shared by any other sub loop, and wherein the outer channel portion of each sub loop comprises one or more valves such that the sub loop is capable of isolation from all other sub loops and each common channel comprises one or more valves such that the common channel is capable of isolation from the remainder of the loop system, and wherein one or more sub loops in the system comprise valves that are configured to enable peristaltic mixing.

Abstract: Mixing system comprising: a flexible bag with a mixing device comprising a magnetic impeller; and an alignment facilitation device adapted to facilitate alignment between the magnetic impeller and a magnetic driver located external to the system. Specific flexible bag and hardware therefore.

Abstract: The invention provides a mixing system comprising a magnetically coupled drive system and a foil for cultivating algae, or cyanobacteria, in an open or enclosed vessel. The invention provides effective mixing, low energy usage, low capital expenditure, and ease of drive system component maintenance while maintaining the integrity of a sealed mixing vessel.

Abstract: A submersible, circulation system for small and shallow bodies of water such as a small pond. The system includes a driving unit with a tubular shell member and a base member and has a submersed motor and pump supported therein. The shell member extends along and about a vertical axis and has upper and lower openings with the base member spaced below and extending across the lower opening to create inlets therebetween. The pump draws water horizontally through the inlets into the unit where a relatively small first portion of the incoming water enters the pump and is driven downwardly and out upwardly directed discharge nozzles. The discharged flow passes through the remaining portion of the incoming flow to induce the larger, remaining portion to move upwardly with it toward the pond surface in a non-turbulent manner to raise the pond surface into a slightly convex mound.

Abstract: A system for blending polymers and other chemicals in an aqueous liquid is provided. Static mixers and tubes, preferably in one or more tube bundles, provide a volume sufficient to allow a residence time in the system to hydrate a polymer. Static mixers may be integrated with a tube bundle. The system may be mounted on a portable base such as a trailer. The concentration of polymer and chemicals in water may be controlled by a controller. A variable speed electric pump may be utilized to precisely control the amount of polymers or other chemicals added to the aqueous liquid.

Abstract: The invention relates to a rotary pump (1) including a rotor (3) arranged in a closed pump housing (2) which is in operative connection with a drive (5) for the pumping of a fluid (4), wherein an inlet opening (6) is provided at the pump housing (2) for the intake of the fluid (4) into the pump housing (2) and an outlet opening (7) is provided at the pump housing (2) for conveying the fluid (4) out of the pump housing into a storage container (8) which is at least partially filled with the fluid (4). In accordance with the invention the outlet opening (7) is arranged and designed at the pump housing in such a way that the fluid (4) can be conveyed out of the pump housing (2) through the outlet opening (7) to the storage container (8) directly and free of ducting. The invention further relates to a hydrodynamic mixer (100) with a rotary pump (1) in accordance with the invention and also to the use of the rotary pump (1) and of the hydrodynamic mixer (100) for the processing of a fluid (4).

Abstract: A mixing unit may be disposed under water of a circular reservoir tank. The mixing unit squirts out water at an upward, outward and skewed angle so as to facilitate rotation of the water within the tank and vertical mixing of the water so as to destratify the temperature gradients within the water.

Abstract: Circulation systems for ponds, lakes, or other bodies of water using a flotation platform, dish, and impeller. One embodiment has a connecting arrangement between the drive motor and the impeller that permits the two to be easily and quickly coupled and uncoupled. The connecting arrangement also is designed to accommodate slight misalignments between the shafts. An arrangement to adjust and calibrate the depth of the inlet to the draft tube is disclosed. The system further includes solar panels that can be pivotally swung outwardly to open positions, angularly adjusted about a horizontal axis, and mounted to face toward the central axis of the flotation platform rather than away from it. Arrangements are further provided to monitor and control the components of the system including remotely from shore.

Abstract: A dynamic mixer in which two members (1,2) are rotated relative to each other about a predetermined axis (XX), the members having facing surfaces (15, 16) which extend axially and between which is defined a mixing chamber through which a flow path extends between an inlet (7) for material to be mixed and an outlet (8). An array of two or more mixing formations is defined on at least one of the facing surfaces (15, 16) which extend radially towards the facing surface of the other element (15, 16) and which act to mix material within the mixing chamber, and which extend axially generally parallel to the axis.

Abstract: A mixer device for materials made up of various divided solid waste, in a vertical silo (1). The device includes the following: a central working area extending along the entire height of the silo (1); a peripheral zone; elements (6) which are distributed vertically at different successive levels (n1, n2, n3 . . . n21) of the working area, along the entire height of the silo (1) and which can lift materials from each of the levels of the working area and release the materials; elements (1a, 19) for bringing matter from the upper part of the peripheral area to the lower center part of the silo (1).

Abstract: A mixing apparatus has a chamber, a shaft extending into the chamber, a motor drivingly interconnected to the shaft, a nozzle support affixed to the shaft and extending outwardly therefrom within the chamber, and a nozzle having an interior passageway affixed to the nozzle support such that the nozzle moves in the chamber as the motor drivingly rotates the shaft. The chamber has a multi-phase fluid therein. A flow restrictor is affixed to an inner wall of said chamber so as to extend inwardly therefor. The flow restrictor is a plurality of flat panels arranged in spaced relation around the interior of the chamber and within a liquid phase of the multi-phase fluid.

Abstract: A mixing apparatus has a chamber, a shaft extending into the chamber, a motor drivingly interconnected to the shaft, a nozzle support affixed to the shaft and extending outwardly therefrom within the chamber, and a nozzle having an interior passageway affixed to the nozzle support such that the nozzle moves in the chamber as the motor drivingly rotates the shaft. The chamber has a multi-phase fluid therein. The nozzle moves through the fluid such that fluid is channeled through the interior passageway at a same rate that the nozzle moves through the fluid. Another nozzle can be affixed to the nozzle support diametrically opposite to the nozzle.

Abstract: A homogenizer is disclosed, which can produce an emulsion with a grain diameter as extremely fine as approximately 1 ?m without using large-scale equipment such as a high-pressure pump, and in which a grain diameter distribution of the produced emulsion exhibits sharp characteristics in the vicinity of a target grain diameter. A fixed portion and a disc-shaped agitation rotor are arranged in an opposing manner through a predetermined clearance to constitute a thrust hydrodynamic bearing, and while supporting a rotation of the agitation rotor with respect to the fixed portion by the thrust hydrodynamic bearing, a plurality of mutually incompatible raw liquids A and B are introduced into the bearing clearance to be mixed and agitated in the bearing clearance in accordance with the rotation of the agitation rotor.

Abstract: According to the present invention, there is provided a stirred tank for storing yeast slurry to be supplied to fermentation tanks where fermented foods such as beer are fermented, is characterized in that a stirring impeller is provided within the stirred tank and so constructed that a maximum diameter of a rotation body defined by the rotation of the stirring impeller is 60-90% of the inner diameter of the stirred tank, and the height of the rotation body is 70% or more of a standard depth of the yeast slurry normally stored in the stirred tank.

Abstract: A method for suspending settled solids in a liquid using a mixing assembly having a mixing vessel, draft tube disposed within the mixing vessel and an impeller disposed within the draft tube. The method includes rotating the impeller in a first rotational direction for a first period of time so as to cause the liquid to flow in a first axial direction. The method also includes rotating the impeller in a second rotational direction so as to cause the liquid to flow in a second axial direction opposite the first axial direction.

Abstract: A tank agitator connects to a low head feed and causes agitation by discharging through a port that might rotate, oscillate, or otherwise issue a pulsing stream. This agitator has a housing with a turbine plenum and an exhaust plenum. A turbine in the turbine plenum spins by the flowthrough of the feedwater and exhausts to the exhaust plenum. A hollow drive shaft is spun by the turbine and extends through the exhaust plenum and to terminate outside the housing. It has an aperture that allows water in the exhaust plenum to flow into its lumen. A nozzle caps the shaft and is bent such that the discharge issuing therefrom sweeps in circles with the spinning of the drive shaft. A variant form of the agitator includes a drive train that incorporates a drag link to convert the spinning input of the turbine into an oscillating output in the drive shaft. In another variant form, the discharge is pulsed.

Abstract: Disclosed is an apparatus for wetting particulate material comprising a tank (1) that has an outlet (2) at its lower end and an inlet (3) at its upper end, into which is mounted a container (4) comprising a number of individual internal chambers (5) having horizontal baffles (6) which each have an orifice (7), a stirring rod (8) which is substantially coaxial with the tank passes through each orifice, and one or more impeller(s) (9) and one or more collar(s) (10) are attached to the stirring rod above each orifice and the apparatus additionally comprises a hopper (11) connected to a feeding device (12) which in turn is connected to an eductor (13) that is coupled to a water supply (24) and the inlet.

Abstract: A method and device for removing particulate matter from a liquid medium, especially a molten salt bath. The structure includes a device for capturing and removing particulate matter from a liquid medium. In operation, the device is inserted into the liquid having the particulate matter, with a particulate matter collector in the particle collecting position. An agitator circulates the liquid having the particulate matter therein. A portion of the particulate matter is collected in the particulate matter collector during the circulation. Thereafter, the circulation is ceased and the device is removed from the liquid with the particulate matter in the particulate matter collector. The device is moved to a discharge position, and the particulate matter collector is moved to a particle discharge position to discharge the particulate matter.

Abstract: A self-anchoring mast for deploying a high-speed submersible mixer in a tank includes operably connected first and second mast members (20, 22) and a foot member 46 operably connected to the second mast member for supporting the mast in a tank. The second mast member includes a track (36, 38) for slidably receiving a bearing of the mixer to change the orientation of the mixer in the tank.

Abstract: A method of mixing plural liquids in a liquid chamber is provided which comprises steps of introducing plural liquids into the liquid chamber, and repeating expansion and shrinkage of a bubble in the liquids in the liquid chamber. In this method, the liquid may be heated to produce the bubble. A liquid-mixing apparatus for mixing plural liquids in a liquid chamber to obtain a liquid mixture is also provided. The liquid-mixing apparatus comprises a liquid chamber; flow channels for introducing the plural liquids into the liquid chamber; a heating part placed in the liquid chamber for heating the liquid mixture in the liquid chamber; and an energy-supplying means for causing expansion and shrinkage of a bubble in the liquid mixture in the liquid chamber.

Abstract: A body 300 having a cavity 310 for mounting a substrate 120 fabricated with probe sequences at known locations according to the methods disclosed in U.S. Pat. No. 5,143,854 and PCT WO 92/10092 or others, is provided. The cavity includes inlets 350 and 360 for introducing selected fluids into the cavity to contact the probes. Accordingly, a commercially feasible device for use in high throughput assay systems is provided.

Abstract: A body 300 having a cavity 310 for mounting a substrate 120 fabricated with probe sequences at known locations according to the methods disclosed in U.S. Pat. No. 5,143,854 and PCT WO 92/10092 or others, is provided. The cavity includes inlets 350 and 360 for introducing selected fluids into the cavity to contact the probes. Accordingly, a commercially feasible device for use in high throughput assay systems is provided.

Abstract: The present invention provides an apparatus and method for mass transfer of gas or other fluids into a liquid and/or liquid suspension. The present invention is preferably used in conjunction with waste treatment processes and/or fermentation processes that are commonly carried out in a mixing vessel. In such an arrangement, the mass transfer process is utilized to contact air to liquid in a mixing vessel or aeration basin.

Abstract: A mixer of fluids, such as paint or resins, having a shaft capable of rotating about a longitudinally-extending, centerline axis of the shaft and at least one rotor assembly that is fixedly connected to and axially-aligned of the shaft. The shaft rotates about its centerline axis as well as each rotor assembly. Each rotor assembly consists of a plurality of spaced apart rotors. Each rotor has substantially uniform upper and lower surfaces and generally smooth and uniform edges. In preferred form, each rotor is a smooth disk that may be flat, wavy, concave, convex, dimpled, or tilted in shape.

Abstract: The present invention provides for a cavitational mixing and/or pumping device and method including a body having a base portion and a peripheral wall extending from the base portion and defining an inlet space therebetween. Additionally, the base portion includes at least one inlet port disposed therein that is in fluid communication with the inlet space. The peripheral wall includes an outlet channel disposed therein that is in fluid communication with the inlet space. A cavitation assembly is disposed within the outlet channel. Alternatively, a plurality of cavitation assemblies may be disposed within the outlet channel.

Abstract: A tank agitator connects to a low head feed and causes agitation by discharging through a port that might rotate, oscillate, or otherwise issue a pulsing stream. This agitator has a housing with a turbine plenum and an exhaust plenum. A turbine in the turbine plenum spins by the flowthrough of the feedwater and exhausts to the exhaust plenum. A hollow drive shaft is spun by the turbine and extends through the exhaust plenum and to terminate outside the housing. It has an aperture that allows water in the exhaust plenum to flow into its lumen. A nozzle caps the shaft and is bent such that the discharge issuing therefrom sweeps in circles with the spinning of the drive shaft. A variant form of the agitator includes a drive train that incorporates a drag link to convert the spinning input of the turbine into an oscillating output in the drive shaft. In another variant form, the discharge is pulsed.

Abstract: Apparatus for mixing a material contained in a vessel comprises one or more flow channels and at least one pair of first and second members which are coaxially mounted one within the other about an axis of rotation such that their facing surfaces curve around the axis defining a chamber therebetween. At least one of the first and second members having a non-circular curvature, the first and second members being rotatable relative to one another about the axis to thereby produce a pumping force to force material through said flow channels. The radially outermost of said first and second members moves to a wall of the vessel relative to stress and displace material present between the mixing apparatus and the wall of the vessel.

Abstract: A method and apparatus is provided for mixing a film of fluid, particularly a film of chemical, biochemical, or biological fluids, undergoing a reaction. The apparatus comprises a means for creating a bubble within the film of fluid, and moving the bubble in the fluid, thereby mixing the fluid.

Abstract: This invention relates to a fluid driven agitator used in densified gas cleaning system, which comprises a hydraulic motor mounted to a cleaning vessel of the densified gas cleaning system, wherein the hydraulic motor comprises a fluid in-port for charging the fluid into the hydraulic motor from outside of the cleaning vessel, and a fluid out-port for discharging the fluid from the hydraulic motor out of the cleaning vessel. An output shaft of the hydraulic motor can be joined to a rotatable component, such as a rotary basket or an impeller, subjecting circulation of the fluid and resulting in stirring.

Abstract: A method and device are described for mixing an oil-containing liquid stored in an oil storage tank to determine the monetary value of said oil-containing liquid contained therein. The method comprises rotating an agitating device in the oil-containing liquid; providing a mixed oil-containing liquid; and determining the monetary value of the oil in said oil-containing liquid. The device includes a shaft disposed in the tank and extending along a central axis of the tank. The shaft includes at least one arm structure extending outward from the shaft so that when the shaft is rotated, the arm structure causes the liquid components to be mixed. The shaft is rotated by a power actuating device which may be a fuel powered motor, an electric powered motor a wind turbine or a manual hand crank.

Abstract: A surface aeration impeller for use in a liquid filled tank. The impeller is rotatable about an axis perpendicular to the static liquid surface. The impeller has a plurality of blades mounted on the underside of a disc or disc-like surface. Each blade has a multi-faceted or curved geometry ranging from vertical at the point of attachment to the disc to partially inclined at the bottom. The blades are spaced circumferentially about the axis and are disposed at acute angles to radial lines from the axis of rotation of the impeller. The lower portions of the blades, which are inclined but non-vertical, are positioned at or below the static liquid surface. When the impeller is rotated, the lower portion pumps the liquid up onto the vertical portion of the blades where the liquid is discharged into a spray umbrella in a direction upwardly and outwardly away from the impeller.

Abstract: A method and apparatus is provided for mixing a film of fluid, particularly a film of chemical, biochemical, or biological fluids undergoing a reaction. The apparatus comprises a means for nucleating a bubble using a discrete heat source, such as a resistor, and moving the bubble in the fluid by creating a temperature gradient, thereby mixing the fluid.

Abstract: A tank agitator connects to a low head feed and causes agitation by discharging through a port that might rotate, oscillate, or otherwise issue a pulsing stream. This agitator has a housing with a turbine plenum and an exhaust plenum. A turbine in the turbine plenum spins by the flowthrough of the feedwater and exhausts to the exhaust plenum. A hollow drive shaft is spun by the turbine and extends through the exhaust plenum and to terminate outside the housing. It has an aperture that allows water in the exhaust plenum to flow into its lumen. A nozzle caps the shaft and is bent such that the discharge issuing therefrom sweeps in circles with the spinning of the drive shaft. A variant form of the agitator includes a drive train that incorporates a drag link to convert the spinning input of the turbine into an oscillating output in the drive shaft. In another variant form, the discharge is pulsed.

Abstract: A method and apparatus is provided for mixing a film of fluid, particularly a film of chemical, biochemical, or biological fluids, undergoing a reaction. The apparatus comprises a means for creating a bubble within the film of fluid, and moving the bubble in the fluid, thereby mixing the fluid.

Abstract: In one aspect, a mixing arrangement is provided for a tank mixing system which includes a tank defined by a side wall, a bottom and a top, the top including at least one opening therethrough. The arrangement includes a non-rotating elongated arm extending through the opening in the top of the tank, the arm pivoted for movement about a pivot axis; an impeller positioned on the arm for movement therewith and within the tank, the impeller moving back and forth along an arcuate path within the tank as the arm pivots back and forth about the pivot axis. In another aspect, a ball-and-socket assembly is positioned above the top of the tank and is movable along a curved path to mope an impeller in a curved path within the tank.