US3415493A - Mixing device - Google Patents

Description

Dec. 10, 1968 R. L. BATES ET AL 3,415,493

MIXING DEVICE Filed Aug. 21, 1967 FIG-1 INVENTORS ROBERT L. BATES 8: PHILIP L. FONDY ATTORNEYS m yza United States Patent 3,415,493 MIXING DEVICE Robert L. Bates and Philip L. Fondy, Dayton, Ohio, assignors to Chemineer, Inc., Dayton, Ohio, a corporation of Ohio Filed Aug. 21, 1967, Ser. No. 661,888 Claims. (Cl. 259--7) ABSTRACT OF THE DISCLOSURE An in-line paste mixer mountable in a line handling a continuously flowing high viscosity material, includes a cylindrical vessel defining a mixing chamber with a radially extending inlet and an axially extending centrally located outlet of substantially equal cross-sectional area. A driven rotatable shaft supported within the chamber includes baflies each with axially extending finger-like elements rotatable between corresponding elements of stationary baifles mounted on the vessel. A mounting flange on each conduit for connecting the mixer within the line and sealed jackets surounding the vessel and the conduits for circulating a heat transfer fluid to control the temperature of the material within the mixer. By maintaining the chamber substantially completely full, plug flow characteristics and a shear-type mixing are accomplished in a very brief time.

Background of the invention To mix a predetermined volume or a batch of a high viscosity liquid or material such as a polymer or mixture of polymers, e.g., a heavy paste, sealant, caulking compound, paint composition, adhesive, mastic or the like, it is desirable to employ a mixing element as disclosed in Bates Patent No. 3,197,180 and assigned to the assignee of the present invention. In general, this mixer incorporates an inclined container defining a cylindrical mixing chamber having an upper inlet and a bottom outlet.

An axially extending shaft is rotably supported within the container and a pair of generally flat paddles or baflles are mounted on the shaft in perpendicular relation adjacent the opposite end walls of the container. The baflles include axially extending finger-like elements which pass between similar axially extending elements of one or more stationary baflles projecting into the chamber from the cylindrical wall of the container. The rotatable and stationary baflles cooperate with the inclined container to produce a recirculating end-to-end mixing action which is highly effective for mixing a predetermined volume or batch of high viscosity material. It is sometimes desirable, however, to mix a continuously flowing high viscosity material, as for example, when it is desirable to add an ingredient into a high viscosity material flowing within a line, Without separating the material into batches, and to obtain uniform dispersion of the ingredient within the material.

Summary of the invention The present invention is directed to a mixing device or apparatus which is particularly suited for mounting in a line conducting a continuous flow of high viscosity material and is especially adapted for mixing materials within a wide range of viscosity, for example from 10,000 to 33,000,000 centipoises. Thus as a primary object, the pres ent invention provides an improved and efficient apparatus for continuous mixing of a high viscosity material flowing continuously through a line while substantially eliminating end-to-end mixing. In addition, the in-line" mixing apparatus of the invention provides for controlling the temperature of the material as it is subjected to the intensive shear-type mixing action produced by the appartus.

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,conduit. The vessel has a flat annular end wall from which a centrally located discharge conduit extends axially to define an outlet having a cross-sectional area substantially the same as that of the inlet. Jackets surround the inner wall defining the chamber and the inlet and discharge conduits in spaced relation to define corresponding annular chambers through which a heat transfer fluid is circulated for controlling the temperature of the material within the mixer. Annular flanges are secured to the outer ends of the conduits for conveniently mounting the apparatus within the line conducting the material.

A power driven shaft is disposed within the chamber and is supported in a cantilevered manner for rotation on an axis extending through the outlet. A baffle is rigidly connected to the shaft adjacent the outlet and a similar baffle is connected to the shaft for rotation past the inlet. The baffles each include axially finger-like elements which rotate between and in close spaced relation with the corresponding elements of a pair of diametrically opposed stationary baflles projecting into the mixing chamber from the inner wall of the vessel.

Brief description of the drawing FIG. 1 is an elevational view in part axial section of an in-line mixing device constructed in accordance with the invention;

FIG. 2 is an end view taken generally on the line 2--2 of FIG. 1;

FIG. 3 is a fragmentary axial section taken generally on the line 3-3 of FIG. 2; and

FIG. 4 is a section taken generally along the line 4-4 of FIG. 1.

Description of the preferred embodiment Referring to the drawing, the in-line mixer shown in FIGS. 1 and 2 includes a fluid tight vessel 12 having a cylindrical inner wall 13 which defines a cylindrical mixing chamber 14. A circular inlet 15 is formed within the wall 13 by the inner end of a radially extending cylindrical inlet conduit 16 rigidly connected to the wall 13. An annular mounting flange 17 is secured to the outer end of conduit 16 and has a series of annularly arranged holes (not shown) for receiving bolts to connect the flange 17 to a mating flange 18 connected to the end of a line 16 adapted to conduct a high viscosity material.

The vessel 12 further includes an annular flat end wall 20 formed by a relatively thin hardened inner annular plate 21 (FIG. 3) reinforced by a substantially thicker outer plate 22. An axially extending tubular discharge conduit 25 is rigidly connected to the end wall 20 and the inner end portion defines a concentrically located circular outlet 26 for the chamber 14. An annular mounting flange 28 is rigidly secured to the outer end of the outlet conduit 25 and has a series of annularly arranged holes for receiving bolts to connect the flnage 28 to a mating flange 29 connected to the end of a continuation of the line 19.

A spacing ring 34 (FIG. 3) is secured to the outer surface of the inner wall 13 of the vessel 12 adjacent the end wall 20 and a rectangular flange 35 is secured to the opposite end of the wall 13. A cyclindrical outer wall or jacket 36 surrounds the inner wall 13 and is connected on opposite ends to the ring 34 and flange 35 to define an annular chamber 38 (FIG. 4) surrounding the chamber 14.

A cylindrical jacket 40 surrounds the inlet conduit 16 in spaced relation and extends between the flange 17 and jacket 36 to form an elongated annular chamber 42 which extends from the chamber 38. Similarly, a cylindrical jacket 44 surounds outlet conduit 25 in spaced relation and extends between the end wall plate 22 and the flange 28 to form an elongated annular chamber 45. Pipe fittings 46 are secured to each of the jackets 36, 40 and 44 to provide a series of inlets and outlets by which a heat transfer fluid is circulated through the corresponding annular chambers 38, 42 and 45. In addition, suitable fittings 47 are connected to the conduits 16 and 25 to obtain samples of the material for testing.

Positioned within the mixing chamber 14 is a driven shaft 51 rotatably supported by a bearing (not shown) retained within a housing 52 secured to the end portion of the wall 13 surrounded by the flange 35. Thus the housing 52 forms the end wall of the chamber 14 opposing the end wall 20 and supports the shaft 51 in a cantilevered manner. In addition, the housing 52 retains shaft seal 54 which prevents material from flowing along the shaft into its supporting bearing.

Mounted on the shaft 51 is a baffle 55 which is formed integrally with the unsupported end portion of the shaft 51 and has an elongated bar member 56 which extends perpendicular to the shaft 51 parallel to the end wall plate 21 and diametrically across the outlet 26. The member 56 supports a series of integral finger-like elements 58 which extend axially within the chamber 14 away from the end Wall 20.

Also mounted on the shaft is another generally flat baflle 60 which is formed integrally with the shaft 51 and is positioned adjacent the end wall formed by the bearing retaining housing 52. The baffle 60 includes an elongated bar member 61 which extends perpendicular to both the shaft 51 and the bar member 56 of the baflle 55. The member 61 supports a series of integral finger-like elements 62 which extend axially within the chamber 14 away from the bearing retaining housing 52.

A pair of diametrically opposed stationary baffles 65 project radially inwardly into the chamber 14. Each stationary baflle 65 includes a support arm 66 which extends radially through aligned holes formed within the cylindrical wall 13 and jacket 36 and is rigidly secured and sealed thereto by suitable welds. Each arm 66 supports a pair of parallel spaced finger-like elements 68 which extend axially between the rotational paths of the elements 58 and 62 of the corresponding baffles 55 and 60 mounted on the shaft 50. The ends of the elements 68 are spaced close to the paths of the bar members 56 and 61 and the ends of the elements 62 pass close to the arms 66.

A housing or pedestal 70 extends from the bearing housing 52 and includes an annular flange 72 which is removably connected to the flange 35 by a series of bolts (not shown). The pedestal 70 supports a gear reducer 75 having an output shaft 76 which is connected to the shaft 51 by a flange coupling 77. The gear reducer 75 has an multiple V-belt drive (not shown) covered by a belt input shaft 78 which is driven by a motor 80 through a guard 82. The motor 80 is supported by a bracket 83 mounted on a frame 84 connected to the gear reducer 75.

It has been found that a mixing apparatus constructed in accordance with the invention provides several desirable features and advantages. For example, by providing the outlet 26 with an area substantially equal to the area of the inlet and by locating the outlet centrally within the end wall with the member 56 of the baflle 55 extending diametrically across the outlet at all times during rotation of the shaft (FIG. 4), the high viscosity material flowing into the chamber 14 is assured of substantial mixing prior to flowing through the outlet 26. Moreover, a highly effective mixing action is produced by the extension of the finger-like elements 68 of the stationary baffles 65 substantially the full distance between the paths of the members 56 and 61 of the corresponding rotatable baflles 55 and 60. In fact, it has been found that the mixing apparatus of the invention will produce an effective mixing action regardless of the orientation of the common axis of the shaft and vessel 12. For example, the apparatus may be supported so that the shaft 51 extends horizontally a shown in FIG. 1 or vertically or at any angle therebetween without significantly affecting the mixing action.

The cylindrical jackets 36, 40 and 44 also provides an important advantage of the invention. That is, by circulating a heat transfer fluid of con-trolled temperature through the corresponding annular passageways 38, 42 and 45, the viscosity of the material being pumped through the mixing apparatus may be controlled, as for example, by circulating a cooling fluid to insure that the substantial heat produced by the mixing action does not adversely affect the product being mixed.

One of the significant features of the present invention is the plug flow characteristic achieved by the mixer of the present invention. The start-up procedure involves introducing material into the mixing chamber while venting the air therein to eliminate the presence of air pockets. Either the connection between flanges 28 and 29 can be broken, or the sampling fitting 47 of conduit 25 may be used. With the chamber substantially full of material, and free of substantial air pockets or dead space, plug flow is achieved which produces highly eflicient mixing for the relatively short dwell time.

Assuming the mixer is horizontally disposed as shown, the mixing is believed to occur in vertically disposed zones. That is, the particles in any vertical zone or band remain in that zone, and due to the arrangement of baifles and the fact that the chamber is substantially completely full, the particles are shifted relative to each other in that zone or band and exit at about the same time. The mixing action is generally that of a spiral within each zone, with the entire mass in the chamber being advanced toward the exit. There is little if any end-to-end mixing because of the absence of appreciable air pockets and the continued advancement of material through the chamber. This is to be contrasted with the Bates patent previously disclosed.

While the mixer of the present invention has been illustrated with a vertically arranged inlet and horizontally arranged outlet, it is to be understood that these may be reversed, or the horizontally disposed opening may be used as the inlet. Also, it is understood that the plug flow characteristics previously described is associated by having the mixing chamber substantially completely full of material to be mixed, and assuring that there is not too great a density difference in the material. In this Way, the residence time of each particle flowing through the mixer is quite close to the average residence time. That is to say, elimination of end-to-end mixing assures efiicient high shear-type mixing in a comparatively short dwell time within the mixer.

While the description of the present invention has been made with reference to a mixer wherein the finger elements of both the movable and stationary b-affle elements are in-line, it will be understood by those skilled in the art that the finger elements of the stationary or movable baifles or both may be pitched to provide a lateral thrust. Pitched baflie elements have application in those instances where the flow characteristics of the material being mixed are such that some lateral thrust is desirable for eflicient mixing or investment of power into shear.

While the form of mixing apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. An in-line paste mixer adapted to be mounted in a fluid handling line for continuously mixing and blending high viscosity material flowing through the line, comprising a mixing chamber including a generally cylindrical center section and spaced end walls, means defining an opening in one of said end walls and an opening in said cylindrical section for continuous entry and exit of high viscosity material at substantially the same flow rate for maintaining said mixing chamber completely full whereby plug flow characteristics are maintained in said chamber, means for connecting said openings to inlet and outline lines, stationary baffle means mounted in said mixing chamber in the path of flow of said material through said chamber, rotatable shaft means entering said mixing chamber through the other of said end walls and mounted in sealing relation therewith with the axis of said shaft generally centrally located with respect to the opening formed in said one end wall, said shaft including a pair of spaced baflie elements mounted on said shaft for non-interfering rotation relative to said stationary baffle means, each said bafile element including a plurality of spaced fingers extending generally axially within said mixing chamber, one of said bafllle elements being mounted adjacent the said opening in said one end wall and continuously sweeping thereacross during rotation of said shaft, the other of said bafiie elements being mounted to sweep across the open ing in said cylindrical section, said stationary baffles being located between said spaced bafile elements and in approximately the same plane as said shaft and including a plurality of fingers extending generally axially within said mixing chamber, means connecting said shaft to effect r0- tation thereof, and said movable and stationary baffies cooperating with said mixing chamber to effect sheartype mixing and blending of said high viscosity material which substantially completely fills said mixing chamber While maintaining plug flow characteristics and substantially eliminating end-to-end mixing of the material being advanced through said mixer.

2. An in-line paste mixer as set forth in claim 1 including a jacket surrounding said cylindrical center sec tion and said means for connecting said openings to inlet and outlet lines for defining a heat transfer fluid circulation chamber, and means for circulating a fluid through said fluid circulation chamber for controlling the temperature of the material within said mixing chamber.

3. An in-line paste mixer as set forth in claim 2 wherein said mixing chamber is disposed in a horizontal plane, said opening in said cylindrical section being an inlet opening disposed in a generally vertical plane, and wherein said opening in said one end wall is an outlet opening disposed in a generally horizontal plane.

4. An in-line paste mixer as set forth in claim 1 wherein said opening in said cylindrical section is an inlet opening and wherein said opening in said one of said side walls is an outlet opening, and the cross-sectional areas of said openings being approximately the same.

5. An in-line paste mixer as set forth in claim 4 wherein said stationary baffies are disposed in a plane normal to the axis of said inlet opening.

6. An in-line paste mixer as set forth in claim 4 wherein the material being mixed has a viscosity of between 10,000 and 33,000,000 centipoises and wherein said means for rotating said shaft is sufficiently large to provide an output in horsepower at least half of which is converted to shear by the action of said movable baflie elements and said stationary baffies are in cooperation with said mixing chamber.

7. An in-line paste mixer as set forth in claim 6 further including jacket means surrounding said mixing chamber and said inlet and outlet opening connecting means for circulation of heat transfer fluid therethrough for control of the temperature within said mixing chamber.

8. An in-line paste mixer as set forth in claim 1 wherein said rotatable baflie means are integral with said shaft and disposed with respect to each other.

9. An in-line paste mixer as set forth in claim 1 further including bearing means adjacent said other end wall suporting said shaft within said mixing chamber in cantilevered manner.

10. An in-line paste mixer as set forth in claim 1 wherein said mixing chamber is disposed in a horizontal plane, and wherein said opening in said cylindrical section is an inlet opening disposed in a generally vertical plane.

References Cited UNITED STATES PATENTS 2,183,859 12/1939 Chace 2597 2,688,470 9/1954 Marco 2598 2,892,619 6/1959 Thurman 2597 3,184,221 5/1965 Mould 2597 3,197,180 7/1965 Bates 2597 ROBERT W. JENKINS, Primary Examiner.

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