Fluid Mixing Apparatus and Methods for Mixing and Improving Homogeneity of Fluids

Abstract

Apparatus that mixes non-homogenous fluid. A threaded shaft within a housing circulates fluid within a container to effect mixing. In one embodiment, when placed in a container of fluid, the housing the fluid is recirculated through opposing ends of the housing. In an embodiment of a related method for mixing, a pump housing containing a screw journaled for rotation receives fluid within a container and conveys the fluid therethrough to circulate a fluid portion in the container along an exterior surface of the housing for mixing with another fluid portion to improve fluid homogeneity. After mixing, the portion of the fluid which first circulates through the housing may recirculate through the housing with said another portion of the fluid. The fluid may be continuously mixed and recirculated through the housing.

Claims

1. An apparatus for mixing a non-homogeneous fluid comprising liquid in a container, comprising: a tubular pump housing having an exterior surface and first and second opposing end portions each suitable for passage of the fluid therethrough, the first end portion including at least a first opening for receiving the fluid into the pump housing and the second end portion including at least a second opening for emitting the fluid within the same container; and a threaded shaft positioned within the pump housing to act as a screw conveyor, the pump housing and the shaft forming an assembly which circulates the fluid within the container, wherein: when the assembly is immersed in a non-homogeneous portion of the fluid and the shaft undergoes rotation with respect to the pump housing, a portion of the non-homogeneous fluid enters the housing through the first opening, exits the pump housing through the second opening and travels along the pump housing exterior surface to effect circulation and mixing of fluid circulating through the assembly thereby improving homogeneity of the fluid

2-23. (canceled)

Description

DESCRIPTION OF THE DRAWINGS

[0014] These and other features, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, wherein:

[0015] FIG. 1 is a partial cut-away elevation view of a portion of a fluid mixing apparatus according to an embodiment of the invention;

[0016] FIG. 2A illustrates the housing of a pump subassembly shown in the embodiment of FIG. 1;

[0017] FIG. 2B illustrates the auger screw component of the pump subassembly shown in the embodiment of FIG. 1; and

[0018] FIG. 3 is an exploded view of components in the fluid mixing apparatus shown in FIGS. 1 and 2.

[0019] Like reference numbers are used throughout the figures to denote like components. Numerous components are illustrated schematically, it being understood that various details, connections and components of an apparent nature are not shown in order to emphasize features of the invention. Various features shown in the figures are not to drawn scale.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring to the figures generally, there is shown a fluid mixing apparatus 6, also referred to as a pump, according to an embodiment of the invention. The apparatus, shown installed through the lid, L, of a container, includes a pump subassembly comprising an auger screw 10, also referred to as a threaded shaft, positioned within a tubular, cylindrically shaped pump housing 12. More specifically, the apparatus is illustrated positioned for operation in a 55 gallon (220 liter) drum container 20, but the invention may be deployed in a wide variety of container sizes and designs, including totes and tanks, and is not limited containers having cylindrical shapes. As shown in FIG. 1, the apparatus is mounted through a standard two inch (5 cm) diameter bung opening 8 in the lid L. During transport and storage of the container the opening 8 is normally sealed with a threaded member The auger screw 10 and the housing 12 may be fabricated from a wide variety of materials, including Al, stainless steel, composites, molded plastics and carbon fiber compositions.

[0021] The pump housing 12 includes a cylindrically shaped body 12′ having lower and upper opposing end portions 12a, 12b, each suitable for passage of fluid therethrough, and a collar 12c positioned to extend from the upper end portion 12b and away from the cylindrically shaped body 12′. The lower end portion 12a includes one or more inlet openings 12o for receiving the fluid into the pump housing 12. Inlet openings 12o may be located at one or at multiple different positions along the lower end portion 12a. Distances from one or plural inlet openings to the bottom of the container may be determined based on the quantity and range of density or viscosity of fluid material along the bottom of the container. In the illustrated embodiment the lower end portion of the body 12′ is open, providing the inlet opening 12o. The inlet opening may include a series of cutouts along the wall of the body 12′ to facilitate fluid flow into the housing. See FIG. 2A.

[0022] The upper end portion 12b of the pump housing 12 terminates in a second opening (not illustrated) about a terminating edge (also not illustrated) having a circular shape and a flat surface perpendicular to the cylindrical axis of symmetry of the housing 12. The circular shape and flat surface of the terminating edge provide a suitable interior ledge for seating of a circular shaped seal 12s when a collar is fitted about the upper end portion. In the example design a collar 12c, having an inside diameter slightly larger than the outside diameter of the second end portion 12b, is placed about the upper end portion 12b so that the collar 12c extends beyond the upper end portion; and the terminating edge of the housing is positioned against an interior wall of the collar 12c to provide the interior ledge for seating of the seal 12s. The positioned collar 12c is welded in place to the housing upper end portion 12b.

[0023] The portion of the collar 12c extending away from the second end portion 12b of the housing 12′ terminates in an opening 12o′ having a diameter equal to the outside diameter of the cylindrically shaped body 12′, e.g., about 1.75 inches (4.44 cm). The interior surface of the collar 12c adjacent the opening 12o′ includes a series of threads (not illustrated) to securely affix the collar to an adapter by which the pump housing 12 is attached to the motor 18. The collar 12c further includes a series of circular exit ports 12p circumferentially distributed about the collar to provide passage of fluid, received through the inlet opening(s) 12o and conveyed through the cylindrically shaped body 12′, out of the housing 12. The illustrated apparatus 6 includes eight such exit ports 12p arranged in a circular pattern around the collar, but this is exemplary. A variable number the ports may be arranged in a variety of configurations to effect mixing.

[0024] The auger screw 10 is generally in the shape of a cylindrical body with threads 10t formed therein providing the cylindrical profile. The majority of the length of the exemplary auger screw comprises one continuous thread but the thread does not extend along an upper shaft portion 10s of the auger screw 10. The threaded portion of the auger screw is positioned within the housing 12 with relatively small clearance between the thread pattern and the interior wall of the housing 12. With the cylindrically shaped body 12′ having an inside diameter of 1.5 in. (3.81 cm), the clearance between the thread pattern on the auger screw and the interior surface of the body 12′ may be 0.125 in. (3.175 mm) or less, e.g., less than or equal to 0.0625 in. (1.59 mm).

[0025] The upper shaft portion 10s of the auger screw 10 is engaged with the shaft 18s of a motor 18 to drive the pump subassembly. The upper shaft portion 10s of the auger screw is of sufficient length to allow a coupling 16 to be installed between the auger screw 10 and the shaft 18s of a motor 18 when the auger screw is inserted into the housing 12 from the lower end portion 12a of the cylindrically shaped body 12′. The illustrated motor 18 driving the auger is air-driven, but may be an electric or hydraulic motor. The air-driven motor includes an air chuck 18a coupled to a flow control valve 18b which feed an air supply to the motor. Air output from the motor passes through a muffler 18c.

[0026] The motor size and the auger thread design (e.g., length, diameter and thread pitch) will vary depending on the application (e.g., flowrate requirements, range of fluid viscosity within the container and desired differential pressure between fluid entering and exiting the pump assembly.

[0027] As shown in FIG. 1, the pump assembly 10, 12 is coupled via an adapter 14 and a coupler 16 to the air motor 18 which controllably drives rotation of the auger screw 10 at variable speeds, e.g., up to 3,000 RPM or higher. An adapter 14 secures the apparatus 6 to the container lid, L, and also provides a firm and stable connection between the housing of the motor 18 and the housing 12 of the pump assembly as the apparatus develops necessary torque to create high RPM needed to generate sufficient pressure differentials for pumping the relatively dense materials.

[0028] The coupler 16 is a cylindrical body having upper and lower ends 16u, 16l and a bore extending therethrough to insert and lock the upper shaft portion 10s of the auger screw 10 to the shaft 18s of the motor 18 for rotation with one another and transfer of torque. The upper shaft portion 10s of the auger screw is inserted within the coupler lower end 16l and welded in place. The coupler upper end 16u receives the shaft 18s of the motor 18. A series of set screws 16s pass through the coupler upper end 16u to secure the motor shaft 18s to the coupler so that the air motor shaft effects powered rotation of the auger screw with the motor 18.

[0029] The adapter 14 is a hollow body through which the coupler 16 passes when attaching the adapter to the motor 18. The adapter 14 attaches to a cylindrically shaped lower housing section 18h of the air motor 18 through which the motor drive shaft 18s extends. A sealing O-ring 14o is positioned at this interface. An upper-most body section 14a of the adapter 14 includes an opening 14o sized to fit about the lower housing section 18h. Set screws 14s mounted through the upper-most body section 14a secure the adapter to the motor. With this attachment the motor drive shaft 18s is positioned within the adapter 14 while coupled to the upper shaft portion 10s of the auger screw. The apparatus 6 is secured to the container 20 by attachment of a mid-body section 14b of the adapter 14, which is a first threaded section, of suitable diameter (e.g., 2 inches) and thread pitch, that engages mating threads formed within the lid along the bung opening 8. Mating threads of the mid body section 14b and the bung opening are not shown in the figures. A lower-most body section 14c of the adapter is a second threaded section, of suitable diameter (e.g., 2 inches) and pitch, that engages afore-described mating threads formed along the interior surface of the collar 12c, i.e., adjacent the opening 12o′, to securely affix the collar to the adapter.

[0030] An embodiment of a method to assemble the drum blender begins with attaching the adapter 14 to the collar by engaging threads of the lower-most body adapter section 14c with mating threads along the interior surface of the collar 12c. Next, the auger screw 10 is inserted through the lower end portion 12a of the housing 12 with the upper shaft portion 10s and the attached coupling 16 extending beyond the collar 12c and beyond the opening 14o of the upper-most adapter body section 14a. With the seal 12s positioned about the coupling 16, the threads of the lower adapter body section 14c engage mating threads along the interior surface of the collar 12c to affix the adapter 14 to the collar 12c. The motor shaft 18s is then inserted within the coupler upper end 16u and the set screws 16s are tightened about the motor shaft to couple the motor shaft 18s with the upper shaft portion 10s of the auger screw. During installation of the apparatus 6 the cavity interior to the coupling 12c and adapter 14, bounded by the seal 12c and the lower motor housing section 18h, is filled with lubricating grease.

[0031] The motor 18 is then moved into mating contact with the adapter 14 and secured to the adapter. This displacement also moves the auger screw 10 into its operational position within the housing 12. Specifically, the lower housing section 18h of the motor 18 is positioned within the opening 14o of the upper-most adapter body section 14a and affixed to the housing section by tightening the set screws 14s. This secures the adapter 14 to the motor 18 with the motor drive shaft 18s positioned within the adapter 14. The apparatus 6 is then installed by inserting the housing 12 through the bung opening 8 and into the container 20, and then rotating the adapter to engage threads of the adapter mid body section 14b with the mating threads formed along the lid bung opening 8. The adapter is rotated to securely tighten the connection to the container for mixing of contents with the apparatus.

[0032] During operation, fluid within the illustrated drum container 20 is circulated and mixed along a path extending along an inner surface 12i of the housing 12, from the inlet opening(s) 12o to the exit ports 12p, and then along an outer surface 12s of the housing 12 where the fluid emitted from the exit ports mixes with other portions of the fluid in the container. The fluid which has exited the ports 12p, as part of a mixture of fluids from different regions in the container, may then re-enter the housing 12 through the first opening(s) 12o.

[0033] When the assembly 6 is immersed in a non-homogeneous fluid, there may be relatively dense material along the container bottom 20b (e.g., having viscosity on the order of 1,000 to 5,000 Centipoise (cps); and there may be relatively light material (e.g., having a lower viscosity on the order of one to 100 cps) in an upper region closer to the lid, L. With rotation of the auger screw 10 relative to the housing 12, a portion of the relatively dense or high viscosity fluid material enters the housing 12 through the inlet opening(s) 12o, travels through the housing 12 and, upon exiting through the ports 12p may begin to mix with the relatively light or low viscosity fluid material. Continued movement of high viscosity fluid and low viscosity fluid along this path effects further mixing of fluid components within the container, thereby increasing homogeneity of the fluid.

[0034] An exemplary flow path generated with operation of the apparatus 6 in a container filled with fluid is shown in FIG. 1. In one method of operation, initially, when the apparatus is started, the air motor 18 drives the pump (10, 12) at relatively low speeds, e.g., 100 to 500 RPM to begin slowly pulling the higher density fluid from along the bottom of the container for redistribution out of the exit ports 12p for a period of 5 to 10 minutes.

[0035] The pump speed may be retained in the range of 100 to 500 RPM to prevent the apparatus 6 from pulling lower viscosity fluid located above the inlet opening(s) 12o (e.g., closer to the container lid, L), and to prevent the pump from drawing air from above the surface of the fluid; so that the volume of material initially drawn into the housing primarily consists of material having viscosity values in the highest range present in the container.

[0036] As portions of fluid having different material compositions are combined, the rotational speed of the auger screw 10 may be increased over a period of, for example, five to thirty minutes, to improve homogenization without drawing air or creating cavitation. Generally, the auger screw 10 is rotated within the housing 12 to move fluid upward within the housing 12 from a lower portion of the container.

[0037] The threads of the auger screw 10 may be straight or tapered. The thread count or pitch of the auger screw 10 (e.g., threads per inch or spacing in mm) can be optimized for mixing based on the fluid components in the container that are to be blended. The auger shaft is slightly smaller than the housing to allow minimum clearance based on tolerances of the shaft 10 and the housing 12.

[0038] Definition of the invention is not limited to any particular theory of operation. The apparatus may function in two operating modes. At very low speeds operation of the auger screw 10 within the housing 12 may lift materials upward from near the container bottom 20b, i.e., involving little or no differential pressure between the inlet opening(s) 12o and the exit ports 12p. At higher rotational speeds, operation of the auger screw 10 within the housing 12 appears to develop a sufficient pressure differential between the inlet opening(s) 12o and the exit ports 12p to pump the fluid through the exit ports. As the fluid mixture becomes more homogeneous, generation of higher differential pressure values appears to improve the speed of achieving satisfactory fluid homogenization and the degree of fluid homogenization. Advantageously, at high speeds (e.g., 1,500-3,000 RPM) the pumped fluid may move axially through the housing 12 without significant turbulence.

[0039] It is believed, with operation of the apparatus based on axial rotation of a screw to generate differential pressure that conveys fluid material along the axis, foaming of high viscosity fluids is limited or absent. Further, the flow rate through the pump housing 12 may be less sensitive to changes in viscosity, possibly because the rotational screw design may be capable of sustaining a desired RPM despite varying demands for increased torque as the viscosity increases. It is believed that the effectiveness of the apparatus for generating the differential pressure at all speeds, to more optimally mix and homogenize fluids, is enhanced by minimization of clearance between the auger screw and the interior surface 12i of the housing 12.

[0040] One or more example embodiments of an apparatus and methods have been illustrated for mixing non-homogeneous fluids. The illustrated embodiments have been described to provide understanding of inventive concepts and underlying principles. It will be recognized by those skilled in the art that the concepts and principles of operation can be readily modified and extended to create other designs and methods providing enhanced performance and functionality to mixing and homogenization processes. Accordingly, the scope of the disclosure is only limited by the claims which follow with each claim describing an embodiment while still other embodiments may combine features recited in different claims. Combinations of different embodiments are within the scope of the claims and will be apparent to those of ordinary skill in the art after reviewing this disclosure.