US3404870A - Agitator - Google Patents

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US3404870A
US3404870A US489632A US48963265A US3404870A US 3404870 A US3404870 A US 3404870A US 489632 A US489632 A US 489632A US 48963265 A US48963265 A US 48963265A US 3404870 A US3404870 A US 3404870A
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vessel
arms
impeller
blade
plane
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Robert K Multer
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01FMIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05Stirrers
    • B01F27/11Stirrers characterised by the configuration of the stirrers
    • B01F27/112Stirrers characterised by the configuration of the stirrers with arms, paddles, vanes or blades

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  • This invention relates to apparatus for agitating a liquid mixture, and more particularly to an impeller for such apparatus, especially suited for blending liquids, and forv mixing andsuspending particles and fluids in aliquid material, and for maintaining such mixtures in a state of uniform dispersion.
  • Theliquids under agitation are usually driven by one or more powered,.rotating impellers, and the operation is usually carried out in a vessel with a circular cross-seclion and a vertical axis.
  • Extensive engineering literature on the subject classifies the liquid agitating systems according to the typefof flo'w developed by the impeller: rotational, axial, or radiaL,
  • the impeller generally comprises onepr more flat, vertically-surfaced paddles, radiating from 'a central driving shaft, which drives the liquid around horizontally.
  • Vertical and radial flow, and liquid shear, are minimal unless the basic design is modified with stationary or contra-rotating surfaces inserted in the liquid flow path.
  • liquids are often agitated with horizontal-shaft screw'propellers, which drive the liquid along straight, approximately radial paths.
  • horizontal-shaft screw'propellers which drive the liquid along straight, approximately radial paths.
  • the liquid is di-' verted upward and tangentially by the wall of the vessel,
  • the most common agitators for generating radial flow are the centrifugal type, including blade turbines, discs,
  • a good apparatus for'agitating aliquid mixture will set the entire mass of liquid incontinuousmotiongwith a uniform distribution of velocity throughout.
  • the im- "peller must be designed'to generate the required-mixing
  • the impeller is slow-turning, dynamically-stable, light in weight; easily constructed,.efiicientinuse of power, and versatile; .s .r Th-is impeller comprises any-number-of flat, horizontal arms that rotate .in a. single horizontal plane, eachiarm bearing'dat its-outer end an.--upward-pitched blade,, ;the whole beingsupported and rotated byasingle-, -vertical shaft'at the axis of. a cylindrical-vessel.”
  • FI G 2 is a planview.-of,a..double b1ade impellennwith a pair ofin-line. arms, in,a -typic al impellerc el configura o i vqp io bafi e and bra i ;FIG. .3 is;a fragmentaryside, elevatio nal View. of: the impeller of-. FI G.,-2 including an optional, brace.
  • FIG. 5 isra fragmentary-side elevational-iview, .in section, 1 showing; a typical side-outlet. drain mounted; inthe -.wall, ofa cylindrical vesself u .1
  • I F166 is a side elevational view, in seetion showsing example; :of ;an agitating, .-system incorporating numerous ,sets, of bladeebearing-armstatvarious elevations alongathe the shaft 2, with the minimum feasible clearance above the H bottom of the vessel 1.
  • the pitched tips or blades at the ends of these arms are brought as close as feasible to the wall of the vessel. Dimensions of one or two inches for bottom and end clearance are typical, but these may be varied.
  • baffles 7 may be mounted rigidly inside the vessel, with three or four being typical. These baffles ordinarily should be set as close as possible to the bottom of the vessel, and should usually extend upward to a height close to the liquid surface, but not so high as to cause the liquid to splash over the vessel wall.
  • An opening 8 in the baflle is generally desirable to eliminate stagnant pockets and to prevent solid material from adhering to the wall and battle.
  • a good width for the baflle in the radial direction is about one-third of the vessel radius, but this, and all other baflle dimensions, and the number and shape of bafiles, may be varied without changing the kind of agitation generated by my impeller.
  • the vessel 1 shown in FIG. 1 is a conventional, vertical, cylindrical tank, with diameter about equal to the height.
  • the dimensions of this vessel may be varied according to ordinary engineering practice, which generally prescribes a diameter equal to between one-third and three times the height.
  • the advantages that derive from the use of my impeller and the agitating systems which utilize my impeller are generally maintained regardless of variations in size and shape of the vessel.
  • the liquid When the impeller is rotated, the liquid follows a path 9 like that shown in FIG. 1: rising near the wall, radially inward at the surface, sinking near the shaft, and radially outward along the bottom. There may also be some rotation of the liquid, depending on the type of fluid, the nature of the baffling, the impeller speed, the depth of liquid, and other factors.
  • FIG. 6 three sets of blade-bearing arms 12 are shown at various elevations along the shaft 2.
  • FIG. 7 a three-blade impeller set 13 is shown.
  • FIGS. 8 and 9 are shown a four-blade impeller set 14, and a six-blade impeller set 15, respectively. In each of these three examples, all of the blades and arms in a set are in a single plane.
  • FIG. 2 shows how arm 6, shaft 2, and blades appear when typically installed in a vessel 1 which includes one optional baffle 7 with a wall-side opening 8.
  • Optional brace 11 is desirable for stiffening arms made of thin material. Two arms can be formed from a single, fiat strip, with its narrow edge facing in the direction of motion; the blades 10 can then be formed by twisting orv bending the outer extremities of the arms as shown in the drawings, or separate blades can be attached.
  • Bracing of the arms is desirable, because this permits the use of thinner material, not only reducing weight, but also reducing rotation of the liquid and improving the effectiveness of the arms in cutting through solids or viscous fluids at the bottom of the vessel.
  • the particular brace 11 shown also improves the agitation.
  • This brace is made from a flat strip, approximately the same in cross-section as the arm 6.
  • the brace is twisted through so that its inner end may be fastened to the shaft in a vertical plane, while its outer end may be fastened in a horizontal plane to the arm 6 next to the blade 10. If twisted in the correct direction, the brace will impel liquid downward near the shaft during normal rotation, and will also generate some radial flow by centrifugal action near the shaft.
  • FIG. 3 shows in detail a typical assembly of shaft 2, arm 6, blade 10, and twisted brace 11. The normal direction of rotation would be toward the viewer.
  • FIG. 4 shows an end view of an impeller blade 10 formed by twisting an arm made of a flat strip.
  • the blade is bent upward, so that the entire length of the arm and blade may closely follow the flat bottom of a tank,
  • the pitch should normally be about 10 to 15 from the horizontal, but this can be varied.
  • the pitched blade of the impeller should extend over about the outer one-third of the radius of the vessel.
  • the width of the flat side of the arm and blade can be about one-thirtieth of the vessel diameter.
  • Rotational speed depends on the kind of agitation desired, the kind of fluid, the size of the vessel, and the exact impeller configuration, among other variables. I have found that a speed of about 40 to 50 revolutions per minute gives good agitation of the aqueous dispersions in tanks whose diameters are 5 to 7 feet, when all other proportions are about as described in the foregoing.
  • the impeller performs well in simply-built, flat-bottomed tanks, with straight, vertical sides, and plain, sharp corners at the junction of wall with bottom. These tanks are usually the easiest and cheapest to build, but conventional agitators do not perform well in them. Not only does my impeller agitate all parts of such vessels, but it also promotes enhanced drainage despite the lack of slope. Furthermore, well-mounted, side-outlet drains may be used with my agitation system, eliminating the need for supports which raise the tank above the floor to provide for the usual, center-mounted drains.
  • FIG. 5 shows the tip of the impeller blade heretofore described sweeping closely past the mouth of a typical side-outlet drain 16, so that the drainage from a flatbottomed vessel through such a drain is facilitated and made more complete than with other impeller designs.
  • the impeller described here is easily modified to fit closely to a bottom of almost any shape.
  • the T shape can be inserted through small openings in avessel, or the arms can be attached to the shaft after both have been inserted separately into the vessel.
  • the impeller generates such uniform motion throughout the entire vessel, even while the speed is varied through a wide range, that the degree of agitation is easily adjusted without sacrifice in completeness of agitation throughout the vessel.
  • the liquid Since the liquid is initially placed in motion by being driven directly upward, adjacent to the smooth side wall of the vessel, it easily continues in motion all the way to the upper surface, even in tall vessels.
  • the fluid is not forced through right-angle turns before being lifted, as it is with other agitators.
  • Adhesion of suspended materials to the vessel is mini mized, because flow is largely directed parallel to vessel surfaces, rather than perpendicular as with conventional agitators.
  • the impeller is uniquely effective when the depth of liquid is very low, because centrifugal action drives most of the liquid to the outer rim, where the blades and baflies can function. Splashing and foaming are minimized under such conditions because the arms are so close to the bottom. Conventional agitators cease to function, and may cause excessive splashing and foaming at very low levels, because they operate near the center of the vessel, and usually not as close to the bottom as mine.
  • the small cross-section of my impeller in the direction of motion helps reduce the size of large particles which are to be dispersed, and reduces shock loads on the apparatus.
  • the plain shape of the impeller with its smooth, flat surfaces and a lack of undercuts, promotes easy cleaning, and minimizes adhesion of materials during use. Close proximity of the bottom of the vessel minimizes buildup beneath the impeller.
  • the lack of rotation also minimizes vortex action, which can draw undesired air into the liquid, but downward flow of liquid at the center is strong despite the absence of vortex.
  • the impeller can tolerate much wear and damage without loss in effectiveness.
  • a single piece of equipment can accommodate a wide variety of fluids and agitation requirements, with no more than a change in speed. Since the drive and bearing re quirements are so mild, the system can be powered by V-belt and other simple types of apparatus which permit easy speed changes.
  • An agitator for liquids comprising a vessel and an axial impeller suspended concentrically therein, the impeller comprising a vertical rotatable shaft with two inline opposed arms carried radially by this shaft and an impeller blade affixed radially and substantially horizontally to the outer end of each of these supporting arms,
  • each arm being about two-thirds of the radius of the vessel, each arm being made of a thin strip of flat material whose greater width lies in the horizontal plane of rotation and whose thickness in the vertical direction is so small that the hydraulic resistance in the direction of rotation is too slight to generate substantial rotary motion of the fluid under treatment, and the plane of rotation of the arms being adjacent to the bottom of the vessel so that sediment cannot accumulate to any significant depth beneath the rotating arms, and
  • each blade being about one-third of the radius of the vessel so that the outer tips of the blades rotate in close proximity to the wall of the vessel, the blades being made of flat material similar in shape to that of which the arms are made, with their thin leading edges rotating in the plane of the arms adjacent to the bottom of the vessel, and with their trailing portions twisted upward behind a lin connecting the leading outer corner of the blade with the trailing inner corner of the blade so .
  • the rearward surface of the blade comprises an approximately triangular plane inclined upward at an angle of about 10 to 15 from the horizontal plane of rotation of the arms while the forward surface of each blade comprises an approximately triangular plane in the plane of rotation of the arms.
  • a diagonal brace connects each arm-blade pair with the shaft, the brace comprising a flat strip whose ends have been twisted perpendicular to each other,with a smoothly-curving surface between the two ends, and so affixed to the impeller that the widest surface of the brace is vertical at the shaft and horizontal where it joins the arm at the junction of arm and blade, and being twisted in such direction that the brace has its downward-driving face in the forward direction during rotation of the impeller.

Description

Oct. 8, 1968 R. K. MULTER 3,404,870
AGITATOR Filed Sept. 23, 1965 5 sheets-sheet 1 INVENTOR QM 4 Mae;
Oct. 8, 1968 R. K. MULTER 3,404,870
AGITATOR Filed Sept. 23, 1965 5 Sheets-Sheet 2 FIG. 2
Oct. 8, 1968 R. K. MULTER 3,404,870
AGITATOR Filed Sept. 23, 1965 5 Sheets-Sheet 5 /NVNTOR 434 k, mwu;
Oct. 8, 1968 v R. K. MULTER 3,404,870
AGITATOR Filed Sept. 23, 1965 5 Sheets-Sheet 4 WW. W
INVENTOR.
ROBERT K. MU LTER Oct. 8, 1968 R. K. MULTER 3,404,870
, AGITATOR Filed Sept. 235, 1965 5 $heetsSheet 5 INVENTOR.
ROBERT K. MULTER i I Robert K. Multer,
States I Pa entbific 7 3,404,810 AGITATOR RED 1, Colts'Neck, NJ. 07722 Filed Sept. 23, 1965, Ser. No. 489,632
' 8 Claims. (Cl. 25943)' This invention relates to apparatus for agitating a liquid mixture, and more particularly to an impeller for such apparatus, especially suited for blending liquids, and forv mixing andsuspending particles and fluids in aliquid material, and for maintaining such mixtures in a state of uniform dispersion.
=-A great variety of apparatus for the agitation of liquids has been developed over the years, because. this opera- .tion has been requiredin almost every industry. Many kinds continue in use today, ,butmost have certain features in common.
Theliquids under agitation are usually driven by one or more powered,.rotating impellers, and the operation is usually carried out in a vessel with a circular cross-seclion and a vertical axis. Extensive engineering literature on the subject classifies the liquid agitating systems according to the typefof flo'w developed by the impeller: rotational, axial, or radiaL,
Amongthe oldest agitators are many rotational impeller systems. The impeller generally comprises onepr more flat, vertically-surfaced paddles, radiating from 'a central driving shaft, which drives the liquid around horizontally. Vertical and radial flow, and liquid shear, are minimal unless the basic design is modified with stationary or contra-rotating surfaces inserted in the liquid flow path.
Probably todays most common agitator for smaller vessels is the vertical-shaft screw propeller system, "in which the liquid is driven downward in a narrow, cylindrical path near the central axis of the vessel. Thepflow is diverted radiallyby the bottom of the vessel, and then upward by the wall, of the vessel, eventually to return radially inward at the upper surface of the agitated liquid. This vertical and radial motion is generated only when rotation of the liquid is inhibited 'by stationary bafl1es,'or
v Like conventional agitators, .mine'.. o ften.-.requires t ,sta-
counteracted by tilting of the impeller shaft sothat the axial flow from the propeller opposes the rotational flow.
In larger vessels, liquids are often agitated with horizontal-shaft screw'propellers, which drive the liquid along straight, approximately radial paths. Usually aft'erbei'ng driven across the bottom of the vessel the liquid is di-' verted upward and tangentially by the wall of the vessel,
to return across the 'surfac"e'of the liquid and downward to the propeller.
The most common agitators for generating radial flow are the centrifugal type, including blade turbines, discs,
cones, cylinders, etcl, which drive the liquidoutwardby friction and centrifugal force, near the bottomof the vessel, when rotated rapidly on a vertical shafL'The liquid is diverted upward'by the wall, eventually to return 'instrongly unless' rotation of the liquid is inhibited by-stationary bafiles. a Another well-known agitator for generating radial "flow 'ward and downward to the impeller. As with the verticalshaft propellers, vertical and radial flow does not persist is the radial propeller, in which a vertical shaft has hori--.
zontal arms at the ends of which are flat, vertical pumpingblades which are pitched so as to drive the liquid'outward. The flow path is likethat for the centrifugal impelle'rs.
A good apparatus for'agitating aliquid mixture will set the entire mass of liquid incontinuousmotiongwith a uniform distribution of velocity throughout. The im- "peller must be designed'to generate the required-mixing,
dispersing, and suspending action with minimum power consumption. For'uniformity in the product and-for high -wasting agitation anywhere.
Patentedv Oct. 8, 1968 "Advantages-soughtin-an agitatordesign include ability to produce the desired'mixture quickly and -to maintain'it "perpetually, low power consumption, durability, ease of *cleaning and machine maintenance, feasibility of'constructionfrom a wide variety of materials, low cost of construction, andfiexibility in major operating variables such as type of liquid and height of liquid in the vessel. My invention provides an improved balance :ofthese advantages by-impelling the liquid in'a different-"manner. My impeller drives the liquidupward, adjacent to and 'parallel to the wall of the vessel, from all points in anarea around the circumference. of the bottom of the .vessel, while sweeping closely over the remaining'area of; the bottom. The impeller is slow-turning, dynamically-stable, light in weight; easily constructed,.efiicientinuse of power, and versatile; .s .r Th-is impeller comprises any-number-of flat, horizontal arms that rotate .in a. single horizontal plane, eachiarm bearing'dat its-outer end an.--upward-pitched blade,, ;the whole beingsupported and rotated byasingle-, -vertical shaft'at the axis of. a cylindrical-vessel."
-Two.blades, on'the ends of.a pairof. in-line arms, .are often adequate. These would be installed as closefas possible to the bottom-of the .-vessel,:lwith theblade'tips as *closeas possible to the wall. v Additionalsarms and blades'maybe, placed in this'same plane. Additional impeller-sets may b.eattached to vthe shaft-at highertlocationsw 1 tionary baffles that inhibit rotation. of thezliquid';
"'The large diameteryof the impeller resultsgin high tip speeds at low rates of rotation. .Thecombination, of large diameter withlow rates of rotation produces great-dynamic stability; The high tip speeds make-possible transfenof large-amounts of energy-to the liquid ,withnonly a slight "pitch to'the' blades; This low pitch angle=yields high power efficiency and reduces-shock loads and damage; to fragile '-S.olid"particles. l a
Outboard-bearings, submerged thev liquid, are usually not needed, even in very large systems. -,,,In.the -drawings fIG. -1;is,a side,.e1evational view, in
.section, showinga ,typical agitating system. incorp0rat in g my impeller. ,FI G 2 is a planview.-of,a..double b1ade impellennwith a pair ofin-line. arms, in,a -typic al impellerc el configura o i vqp io bafi e and bra i ;FIG. .3 is;a fragmentaryside, elevatio nal View. of: the impeller of-. FI G.,-2 including an optional, brace.
4 isan end-yiew Of atypical impeller bladeand :.a rm ;0na shaft; I
5 isra fragmentary-side elevational-iview, .in section, 1 showing; a typical side-outlet. drain mounted; inthe -.wall, ofa cylindrical vesself u .1 I F166 is a side elevational view, in seetion showsing example; :of ;an agitating, .-system incorporating numerous ,sets, of bladeebearing-armstatvarious elevations alongathe the shaft 2, with the minimum feasible clearance above the H bottom of the vessel 1. a
The pitched tips or blades at the ends of these arms are brought as close as feasible to the wall of the vessel. Dimensions of one or two inches for bottom and end clearance are typical, but these may be varied.
One or more baffles 7 may be mounted rigidly inside the vessel, with three or four being typical. These baffles ordinarily should be set as close as possible to the bottom of the vessel, and should usually extend upward to a height close to the liquid surface, but not so high as to cause the liquid to splash over the vessel wall. An opening 8 in the baflle is generally desirable to eliminate stagnant pockets and to prevent solid material from adhering to the wall and battle. A good width for the baflle in the radial direction is about one-third of the vessel radius, but this, and all other baflle dimensions, and the number and shape of bafiles, may be varied without changing the kind of agitation generated by my impeller.
The vessel 1 shown in FIG. 1 is a conventional, vertical, cylindrical tank, with diameter about equal to the height. The dimensions of this vessel may be varied according to ordinary engineering practice, which generally prescribes a diameter equal to between one-third and three times the height. The advantages that derive from the use of my impeller and the agitating systems which utilize my impeller are generally maintained regardless of variations in size and shape of the vessel.
When the impeller is rotated, the liquid follows a path 9 like that shown in FIG. 1: rising near the wall, radially inward at the surface, sinking near the shaft, and radially outward along the bottom. There may also be some rotation of the liquid, depending on the type of fluid, the nature of the baffling, the impeller speed, the depth of liquid, and other factors.
This pattern of liquid motion will not ordinarily change much, in a well-proportioned system, as the depth of liquid changes. However in very flat, shallow vessels, or when the liquid level is extremely low in any vessel, the flow will not strictly follow the pattern shown; in these cases there will be an exceptional amount of turbulence,
rotation, and centrifugal action because of the close proximity of the impeller arms to the liquid surface.
In very tall, narrow vessels it may be desirable to place additional impeller arms with blades at various heights along the shaft. For most applications, only one, doublebladed pair of arms is required at any level.
In FIG. 6, three sets of blade-bearing arms 12 are shown at various elevations along the shaft 2.
For some applications, as in vessels with very large diameters, additional bladed arms in the same horizontal plane may be desirable.
In FIG. 7, a three-blade impeller set 13 is shown. In FIGS. 8 and 9 are shown a four-blade impeller set 14, and a six-blade impeller set 15, respectively. In each of these three examples, all of the blades and arms in a set are in a single plane.
It should be emphasized that many of the benefits of my impeller and agitating system derive from the fact that in most vessels, with most fluids, and regardless of variations in operating depth, only two blades on a pair of in-line arms are needed.
FIG. 2 shows how arm 6, shaft 2, and blades appear when typically installed in a vessel 1 which includes one optional baffle 7 with a wall-side opening 8. Optional brace 11 is desirable for stiffening arms made of thin material. Two arms can be formed from a single, fiat strip, with its narrow edge facing in the direction of motion; the blades 10 can then be formed by twisting orv bending the outer extremities of the arms as shown in the drawings, or separate blades can be attached.
Bracing of the arms is desirable, because this permits the use of thinner material, not only reducing weight, but also reducing rotation of the liquid and improving the effectiveness of the arms in cutting through solids or viscous fluids at the bottom of the vessel.
The particular brace 11 shown also improves the agitation. This brace is made from a flat strip, approximately the same in cross-section as the arm 6. The brace is twisted through so that its inner end may be fastened to the shaft in a vertical plane, while its outer end may be fastened in a horizontal plane to the arm 6 next to the blade 10. If twisted in the correct direction, the brace will impel liquid downward near the shaft during normal rotation, and will also generate some radial flow by centrifugal action near the shaft.
FIG. 3 shows in detail a typical assembly of shaft 2, arm 6, blade 10, and twisted brace 11. The normal direction of rotation would be toward the viewer.
FIG. 4 shows an end view of an impeller blade 10 formed by twisting an arm made of a flat strip. The blade is bent upward, so that the entire length of the arm and blade may closely follow the flat bottom of a tank, The pitch should normally be about 10 to 15 from the horizontal, but this can be varied.
In general, the pitched blade of the impeller should extend over about the outer one-third of the radius of the vessel. The width of the flat side of the arm and blade can be about one-thirtieth of the vessel diameter.
Rotational speed depends on the kind of agitation desired, the kind of fluid, the size of the vessel, and the exact impeller configuration, among other variables. I have found that a speed of about 40 to 50 revolutions per minute gives good agitation of the aqueous dispersions in tanks whose diameters are 5 to 7 feet, when all other proportions are about as described in the foregoing.
All of the dimensions, proportions and speeds described herein may be altered considerably, without departing from the essential concept of this invention, which is to use a simply-formed, large-diameter, rotating blade impeller, pitched upward at its outer extremities, so as to impart upward motion to a liquid from points near the bottom of the wall of a vertical, cylindrical vessel, for the chief purpose of mixing, dispersing, suspending, and otherwise agitating fluids and fluid mixtures in vessels of all sizes.
My impeller and agitating system have numerous advantages over previous designs, which will affect the way my invention will be used, and will govern the specific details of its construction in actual applications.
The impeller performs well in simply-built, flat-bottomed tanks, with straight, vertical sides, and plain, sharp corners at the junction of wall with bottom. These tanks are usually the easiest and cheapest to build, but conventional agitators do not perform well in them. Not only does my impeller agitate all parts of such vessels, but it also promotes enhanced drainage despite the lack of slope. Furthermore, well-mounted, side-outlet drains may be used with my agitation system, eliminating the need for supports which raise the tank above the floor to provide for the usual, center-mounted drains.
FIG. 5 shows the tip of the impeller blade heretofore described sweeping closely past the mouth of a typical side-outlet drain 16, so that the drainage from a flatbottomed vessel through such a drain is facilitated and made more complete than with other impeller designs.
Despite its suitability for flat-bottomed vessels, the impeller described here is easily modified to fit closely to a bottom of almost any shape.
The simple shape of this impeller, the lack of precision needed in its fabrication, and its dynamically stable shape, make possible the construction of units of any size, without complex tools or highly skilled labor, using standard shapes of almost any construction material, and applying protective coatings when required.
The T shape can be inserted through small openings in avessel, or the arms can be attached to the shaft after both have been inserted separately into the vessel.
Bearing and support requirements are not severe, even when shafts are long, diameters large, and power high.
Outboard bearings submerged in the liquid are not needed.
Power consumption is low.
The impeller generates such uniform motion throughout the entire vessel, even while the speed is varied through a wide range, that the degree of agitation is easily adjusted without sacrifice in completeness of agitation throughout the vessel.
Because the impeller sweeps the entire bottom of the vessel, heavy materials cannot remain there undisturbed. Materials that settle are continually lifted, fluidized, and carried radially to the blades for elevation.
Since the liquid is initially placed in motion by being driven directly upward, adjacent to the smooth side wall of the vessel, it easily continues in motion all the way to the upper surface, even in tall vessels. The fluid is not forced through right-angle turns before being lifted, as it is with other agitators.
Heavy materials which fall prematurely out of the rising stream are quickly relifted, while well-suspended materials follow the longest possible path.
Adhesion of suspended materials to the vessel is mini mized, because flow is largely directed parallel to vessel surfaces, rather than perpendicular as with conventional agitators.
The impeller is uniquely effective when the depth of liquid is very low, because centrifugal action drives most of the liquid to the outer rim, where the blades and baflies can function. Splashing and foaming are minimized under such conditions because the arms are so close to the bottom. Conventional agitators cease to function, and may cause excessive splashing and foaming at very low levels, because they operate near the center of the vessel, and usually not as close to the bottom as mine.
The small cross-section of my impeller in the direction of motion helps reduce the size of large particles which are to be dispersed, and reduces shock loads on the apparatus.
This small cross-section, and the sweeping action over the entire bottom, make my system effective in resuspending materials which have settled to the bottom, as for instance during a power failure. If the agitator has suflicient power to cut a path through the settled material, it will eventually redisperse it. On the other hand, if it lacks such power, but has been properly designed to withstand the torque of its drive and support apparatus, it will not rotate and will not be damaged. Most conventional designs either will not re-disperse materials under such condiitons, or else may be damaged during startup.
The plain shape of the impeller, with its smooth, flat surfaces and a lack of undercuts, promotes easy cleaning, and minimizes adhesion of materials during use. Close proximity of the bottom of the vessel minimizes buildup beneath the impeller.
The low velocity of the liquid at the surface, and its predominantly inward direction, minimizes splashing when the vessel is full. The lack of rotation also minimizes vortex action, which can draw undesired air into the liquid, but downward flow of liquid at the center is strong despite the absence of vortex.
The impeller can tolerate much wear and damage without loss in effectiveness.
Power consumption declines as the liquid depth falls in any vessel, so operating costs remain in proportion to the productive work performed, and the degree of agitation remains fairly constant.
A single piece of equipment can accommodate a wide variety of fluids and agitation requirements, with no more than a change in speed. Since the drive and bearing re quirements are so mild, the system can be powered by V-belt and other simple types of apparatus which permit easy speed changes.
I claim:
1. An agitator for liquids comprising a vessel and an axial impeller suspended concentrically therein, the impeller comprising a vertical rotatable shaft with two inline opposed arms carried radially by this shaft and an impeller blade affixed radially and substantially horizontally to the outer end of each of these supporting arms,
(a) the vessel being a right circular cylinder whose axis is vertical and whose bottom is flat and horizontal, and
(b) the length of each arm being about two-thirds of the radius of the vessel, each arm being made of a thin strip of flat material whose greater width lies in the horizontal plane of rotation and whose thickness in the vertical direction is so small that the hydraulic resistance in the direction of rotation is too slight to generate substantial rotary motion of the fluid under treatment, and the plane of rotation of the arms being adjacent to the bottom of the vessel so that sediment cannot accumulate to any significant depth beneath the rotating arms, and
(c) the length of each blade being about one-third of the radius of the vessel so that the outer tips of the blades rotate in close proximity to the wall of the vessel, the blades being made of flat material similar in shape to that of which the arms are made, with their thin leading edges rotating in the plane of the arms adjacent to the bottom of the vessel, and with their trailing portions twisted upward behind a lin connecting the leading outer corner of the blade with the trailing inner corner of the blade so .that the rearward surface of the blade comprises an approximately triangular plane inclined upward at an angle of about 10 to 15 from the horizontal plane of rotation of the arms while the forward surface of each blade comprises an approximately triangular plane in the plane of rotation of the arms.
2. The agitator of claim 1 wherein additional identical blades and arms are carried by the shaft in the horizontal plane of rotation adjacent to the bottom of the vessel.
3. The agitator of claim 1 wherein additional identical sets of blades and arms are carried by the shaft in horizontal planes of rotation above the set of blades and arms described.
4. The agitator of claim 1 wherein no foot bearing is employed to stabilize the lower end of the shaft in relation to the bottom of the vessel.
5. The agitator of claim 1 wherein stationary, vertical bafile surfaces are mounted radially inside the wall of the vessel.
6. The agitator of claim 1, wherein a diagonal brace connects each arm-blade pair with the shaft, the brace comprising a flat strip whose ends have been twisted perpendicular to each other,with a smoothly-curving surface between the two ends, and so affixed to the impeller that the widest surface of the brace is vertical at the shaft and horizontal where it joins the arm at the junction of arm and blade, and being twisted in such direction that the brace has its downward-driving face in the forward direction during rotation of the impeller.
7. The agitator of claim 1 wherein the rotational speed is about 40 to 50 revolutions per minute in vessels whose diameters are about 5 to 7 feet.
8. The agitator of claim 1 wherein a side-outlet drain is mounted in the wall of the vessel.
References Cited UNITED STATES PATENTS 683,474 10/ 1901 MacKinzie 259-44 754,931 3/ 1904 Meyrick 259--24 1,803,446 5/1931 Warrick 259-108 2,235,604 3/1941 Brumagin 259107 78,398 5/1869 Schuffert et al 259 583,572 1/1867 Gordon et al 259108 FOREIGN PATENTS 13,784 1893 Great Britain. 590,635 4/ 1959 Italy.
WILLIAM I. PRICE, Primary Examiner.

Claims (1)

1. AN AGITATOR FOR LIQUIDS COMPRISING A VESSEL AND AN AXIAL IMPELLER SUSPENDED CONCENTRICALLY THEREIN, THE IMPELLER COMPRISING A VERTICAL ROTATABLE SHAFT WITH TWO INLINE OPPOSED ARMS CARRIED RADIALLY BY THIS SHAFT AND AN IMPELLER BLADE AFFIXED RADIALLY AND SUBSTANTIALLY HORIZONTALLY TO THE OUTER END OF EACH OF THESE SUPPORTING ARMS, (A) THE VESSEL BEING A RIGHT CIRCULAR CYLINDER WHOSE AXIS IS VERTICAL AND WHOSE BOTTOM IS THAT AND HORIZONTAL, AND (B) THE LENGTH OF EACH ARM BEING ABOUT TWO-THIRDS OF THE STRIP OF THE VESSEL EACH ARM BEING MADE OF A THIN STRIP OF FLAT MATERIAL WHOSE GREATER WIDTH LIES IN THE HORIZONTAL PLANE ROTATION AND WHOSE THICKNESS IN THE VERTICAL DIRECTION IS SO SMALL THAT THE HYDRAULIC RESISTANCE IN TH DIRECTION OF ROTATION IS TOO SLIGHT TO GENERATE SUBSTANTIAL ROTARY MOTION OF THE FLUID UNDER TREATMENT, AND THE PLANE OF ROTATION OF THE ARMS BEING ADJACENT TO THE BOTTOM OF THE VESSEL SO THAT SEDIMENT CANNOT ACCUMULATE TO ANY SIGNIFICANT DEPTH BENEATHA THE ROTATING ARMS, AND (C) THE LENGHT OF EACH BLADE BEING ABOUT ONE-THIRD OF THE RADIUS OF THE VESSEL SO THAT THE OUTER TIPS OF THE BLADES ROTATE IN CLOSE PROXIMITY TO THE WALL OF THE VESSEL, THE BLADES BEING MADE OF THAT MATERIAL SIMILAR IN SHAPE TO THAT OF WHICH THE ARMS ARE MADE, WITH THEIR THIN LEADING EDGES ROATATING IN THE PLANE OF THE ARMS ADJACENT TO THE BOTTOM OF THE VESSEL, AND WITH THEIR TRAILING PORTIONS TWISTED UPWARD BEHIND A LINE CONNECTING THE LEADING OUTER CORNER OF THE BLADE WITH THE TRAILING INNER CORNER OF THE BLADE SO THAT THE REARWARD SURFACE OF THE BLADE COMPRISES AN APPROXIMATELY TRIANGULAR PLANE INCLINED UPWARD AT AN ANGLE OF ABOUT 10* TO 15* FROM THE HORIZONTAL PLANE OF ROATATION OF THE ARMS WHILE THE FORWARD SURFACE OF EACH BLADE COMPRISES AN APPROXIMATELY TRIANGULAR PLANE IN THE PLANE OF ROTATION OF THE ARMS.
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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2643560A1 (en) * 1976-09-28 1978-03-30 Stelzer Fa Erwin Impeller for tank agitation - having blades bent to give two angles of inclination to shaft axis over a radial distance
WO1980000925A1 (en) * 1978-10-31 1980-05-15 Union Process International An agitated-media mill with a baffled inner wall
FR2439614A1 (en) * 1978-10-27 1980-05-23 Melange Ste Europ Stiffening brace for blade or propeller for mixer, fan etc. - has surfaces which assist axial thrust of propeller in rotation
EP0011559A1 (en) * 1978-11-15 1980-05-28 Societe Metallurgique Le Nickel - S.L.N. Process and apparatus for wet attrition
DE3132263A1 (en) * 1980-08-27 1982-06-24 Institut Merieux, Lyon, Rhône Stirring appliance for liquids, and use of the appliance for stirring
US4457627A (en) * 1982-04-05 1984-07-03 Kirby Robert E Circular containment system for well drilling fluid
US4577975A (en) * 1984-05-09 1986-03-25 Carl Mccrory Enterprises, Inc. Mixing and blending apparatus
US4614439A (en) * 1984-07-06 1986-09-30 Pilkington Brothers P.L.C. Mixer for mixing fibres into a slurry
US4875781A (en) * 1988-05-19 1989-10-24 Raska Jack C Paint mixing paint container
US5324110A (en) * 1991-10-28 1994-06-28 Satake Chemikal Equipment Mfg., Ltd. Agitating device with baffle
US20030007417A1 (en) * 2001-05-17 2003-01-09 Tadaaki Miyata Agitating impeller, agitator using the same, and agitating method
US6508583B1 (en) * 2000-11-28 2003-01-21 E. I. Du Pont De Nemours And Company Agitated vessel for producing a suspension of solids
US20050162973A1 (en) * 2004-01-23 2005-07-28 Katz Jonathan M. Blender blade
US20150251146A1 (en) * 2007-12-21 2015-09-10 Philadelphia Mixing Solutions, Ltd. Method and apparatus for mixing
US20150259501A1 (en) * 2011-11-28 2015-09-17 Asahi Kasei Chemicals Corporation Steam Stripping Apparatus and Steam-Stripping Finishing Method Using Same

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US78398A (en) * 1868-05-26 George cooper
US583572A (en) * 1897-06-01 Churn
US683474A (en) * 1900-12-11 1901-10-01 Robert F Mackinzie Confectionery-kettle.
US754931A (en) * 1903-09-25 1904-03-15 George E Cain Butter-separator.
US1803446A (en) * 1928-12-10 1931-05-05 Charles F Warrick Electric mixer
US2235604A (en) * 1940-04-09 1941-03-18 Ivan S Brumagim Radial propeller agitator

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US78398A (en) * 1868-05-26 George cooper
US583572A (en) * 1897-06-01 Churn
US683474A (en) * 1900-12-11 1901-10-01 Robert F Mackinzie Confectionery-kettle.
US754931A (en) * 1903-09-25 1904-03-15 George E Cain Butter-separator.
US1803446A (en) * 1928-12-10 1931-05-05 Charles F Warrick Electric mixer
US2235604A (en) * 1940-04-09 1941-03-18 Ivan S Brumagim Radial propeller agitator

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2643560A1 (en) * 1976-09-28 1978-03-30 Stelzer Fa Erwin Impeller for tank agitation - having blades bent to give two angles of inclination to shaft axis over a radial distance
FR2439614A1 (en) * 1978-10-27 1980-05-23 Melange Ste Europ Stiffening brace for blade or propeller for mixer, fan etc. - has surfaces which assist axial thrust of propeller in rotation
WO1980000925A1 (en) * 1978-10-31 1980-05-15 Union Process International An agitated-media mill with a baffled inner wall
US4244531A (en) * 1978-10-31 1981-01-13 Union Process, Inc. Agitated-media mill with a baffled inner wall
EP0011559A1 (en) * 1978-11-15 1980-05-28 Societe Metallurgique Le Nickel - S.L.N. Process and apparatus for wet attrition
DE3132263A1 (en) * 1980-08-27 1982-06-24 Institut Merieux, Lyon, Rhône Stirring appliance for liquids, and use of the appliance for stirring
US4457627A (en) * 1982-04-05 1984-07-03 Kirby Robert E Circular containment system for well drilling fluid
US4577975A (en) * 1984-05-09 1986-03-25 Carl Mccrory Enterprises, Inc. Mixing and blending apparatus
US4614439A (en) * 1984-07-06 1986-09-30 Pilkington Brothers P.L.C. Mixer for mixing fibres into a slurry
US4875781A (en) * 1988-05-19 1989-10-24 Raska Jack C Paint mixing paint container
US5324110A (en) * 1991-10-28 1994-06-28 Satake Chemikal Equipment Mfg., Ltd. Agitating device with baffle
US6508583B1 (en) * 2000-11-28 2003-01-21 E. I. Du Pont De Nemours And Company Agitated vessel for producing a suspension of solids
US20030007417A1 (en) * 2001-05-17 2003-01-09 Tadaaki Miyata Agitating impeller, agitator using the same, and agitating method
US20050162973A1 (en) * 2004-01-23 2005-07-28 Katz Jonathan M. Blender blade
US7278598B2 (en) * 2004-01-23 2007-10-09 Vita-Mix Corporation Blender blade
US20080008029A1 (en) * 2004-01-23 2008-01-10 Katz Jonathan M Blender blade
US7552885B2 (en) * 2004-01-23 2009-06-30 Vita-Mix Corporation Blender blade
US20150251146A1 (en) * 2007-12-21 2015-09-10 Philadelphia Mixing Solutions, Ltd. Method and apparatus for mixing
US9802169B2 (en) * 2007-12-21 2017-10-31 Philadelphia Mixing Solutions, Ltd. Method and apparatus for mixing
US20150259501A1 (en) * 2011-11-28 2015-09-17 Asahi Kasei Chemicals Corporation Steam Stripping Apparatus and Steam-Stripping Finishing Method Using Same
US9616405B2 (en) * 2011-11-28 2017-04-11 Asahi Kasei Chemicals Corporation Steam stripping apparatus and steam-stripping finishing method using same

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