US 3352543 A
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H. H. NIEDERMAN ET AL 3,352,543
Nov. 14, 1967 VERTICAL MIXER 3 Sheets-Sheet 1 Filed June 10, 1966 m M O A M /W E AE m g M s m J 4 UR f. fi mH X m v q 4 m\ v 7 9 O\@\ x V. 3 i 5 i t BY W AGENT 14,1967 7 H. H. NIEDERMAN EFAL 3,352,543
I VERTICAL MIXER Filed June 10, 1966 5 Sheets-Sheet 3 L25 INVENTORS 14/. PAUL JENSEN HOWAIPDJf. N/EDERMA/V AGENT NOV. 14, 1967 H NlEDERMAN ET AL 3,352,543
VERTICAL MIXER Filed June 10, 1966 5 Sheets-Sheet 3 INVENTORS W PAUL JENSEN HOWARD H. N/EDERMAN BY MK AGENT United States Patent 3,352,543 VERTICAL MIXER Howard H. Niederman, Pasadena, Calif., and William Paul Jensen, Springfield, Va., assignors to Atlantic Research Corporation, Fairfax, Va., a corporation of Virginia Filed June 10, 1966, Ser. No. 556,733 14 Claims. (Cl. 25944) ABSTRACT OF THE DISCLOSURE Vertical mixers designed to provide a multitude of flow patterns and a broad spectrum of shear characteristics by the use of a first blade set tracing an envelope in close proximity to the interior wall of the receptacle and a second blade set tracing an envelope entirely within that of the first set. The blades are of helical ribbon configuration and can be wound in like or opposite directions with equal or ditierent pitches. Each blade set can be on a separate shaft, and can be rotated in different directions and speed than the other. In addition, the blade sets can reciprocate and can be adjusted along the axis of the receptacle to vary the depth to which it extends into the receptacle.
Background the invention This invention relates broadly to mixing apparatus, and more particularly to vertical mixing apparatus of high efficiency.
As modern technology advances, it becomes necessary to provide mixing apparatus in which sophisticated flow patterns can be generated in order to properly mix liquids and slurries. In the prior art, there are a multitude of designs for mixing apparatus, in most cases tailored to a specific mixing problem and oifering a minimum of versatility. More often than not, when a new flow pattern or mixing characteristic was found necessary, an old mixing design was modified by the addition of bafiles, secondary agitators, or extra paddle wheels in order to qualify for the new job. It was generally not possible to vary the flow patterns or mixing characteristics of a particular mixing machine except within very limited parameters. One of the primary problems in the mixing field has been that of providing a mixer so versatile as to be able to efficiently mix materials of both high and low viscosity or of viscosity which changes as the mixing progresses, While still providing the desired degree of mixing violence with the proper shear action. The instant invention provides a mixer design in which the mixing characteristics and flow patterns are variable over a wide range in order to solve this problem. Furthermore, since chemical reactions often are to take place along with the mixing of the materials, the instant design offers a large area of reactive contact as well as a large surface area where the mixture may be aerated or deaerated.
Summary of the invention This invention involves designs of vertical mixers and reactors, the former designed to optimize the mixing of liquids and slurries and the latter designed to minimize reaction time by increasing the intimacy of contact of the reacting materials. The design of the blades is such that a single blade set can be used in a mixer receptacle without the use of bafiies or other accessories. Essentially, the blade set consists of a helica-lly wound outer blade tracing an envelope closely conforming to the interior shape of the mixer receptacle, and a helically wound inner blade tracing an envelope spaced from and within the outer envelope. The blade set has no center shaft and can be constructed with or without a foot bearing. Depending upon the flow patterns desired, the direction of helical winding of the inner blades can be the same as or opposite to that of the outer blades. The inner and outer blades can be fixed with relation to each other or can be mounted on separate concentric shafts so that they may be rotated in the same direction or in opposite directions at the same or different speeds.
The mixing receptacles to which this invention applies can be sections of right-circular cylinders, frustroms of cones alone or in combination with cylindrical sections, or either or both of these combined with a bottom portion such as a segment of a sphere. The mixer bowl preferably has a valved discharge opening in the bottom.
By specific design in the case of the embodiment utilizing integral blades, and by altering relative speeds and directions in the embodiment having independently rotatable blades, a variety of mixing flow patterns, speeds, and degrees of shearing action can be provided. For example, if oppositely wound blades move in a direction such that the material to be mixed is driven downwardly by the outer blades, it will be moved in the opposite direction, i.e., upwardly, by the inner blades. In .the case where both blades are wound in the same direction, the mixture is moved downwardly by both inner and outer blades and is forced to squeeze upwardly between the two downward flow streams. Rotation in the opposite direction will cause both inner and outer blades to move the mixture upwardly. This is especially desirable when the mixture is to contact a vapor space above its surface, for the mass movement of mixture is high and the greatest amount will be exposed to the vapor space in a minimum time, thus allowing maximum contact with a reactive vapor in the space or maximum opportunity to draw off unwanted vapors. In the case where both blades move the mixture downward, if the outer blade is properly spaced from the receptacle interior wall, an upward flow is established immediately adjacent this interior surface and a large area of contact and shear is provided. Considering the pitch of each of the blades to be the distance between adjacent turns, if the blades are made such that the pitch of the outer blades is greater than that of the inner blades, the major force will be contributed by the outer blades and the mixture can be expeditiously extruded from a discharge opening in the bottom of the receptacle.
It is an object of this invention to provide a mixing apparatus having new and improved mixing blades.
Another object of this invention is to provide a mixing apparatus in which the flow pattern of the material being mixed can be varied.
Another object of this invention is to provide a mixing apparatus having a readily predictable and controllable shear rate and reproducible mixing characteristics.
Another object of this invention is to provide an im proved mixing apparatus which effects rapid and total dispersion of the ingredients in a minimum mixing time.
Another object of this invention is to provide mixing 7 apparatus in which the action of the blades provides a momentum for discharge of the ingredients firom the receptacle.
Other objects and advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings wherein:
The drawings FIGURE 3 shows the mixer of FIGURE 1 in which the inner blades have been modified;
FIGURE 4 shows the mixer of FIGURE 2 in which the clearance between outer blades and receptacle .can be varied; and
FIGURE .5 shows the mixer of the instant invention 'in which the inner and outer blades are independently mounted on concentric shafts, and in which the clearance between blades and receptacle can be varied.
Description the invention Briefly "stated, this invention is presented in two embodiments, a first in which the inner and outer blades are fixed with respect to one another and a second in which the inner and outer blades are independently mounted on concentric shafts. Both embodiments provide a mixing apparatus including a "vertically oriented receptacle having within it a set of mixing blades. The blade set consists of outer blades of helical ribbon configuration tracing a first envelope which closely approximates the interior shape of the receptacle and which is spaced slightly therefrom, and inner blades of generally helical ribbon configuration within and concentrically aligned with the outer blades and tracing a second envelope entirely within the first envelope. The blade set is supported by the drive shaft at its upper end, and can be supported by 'a foot bearing at the lower end, but under no circumstances is it supported by a center col- 'umn. The elimination of the center column for blade support provides this mixer with certain important advantages, including the fact the instruments can be lowered into the receptacle along the center axis and take measurements at any horizontal plane, more varied fiow streams can be provided by utilizing this center space, and the blades are allowed a greater degree of 'flexure to absorb 'the various strains, stresses, and shocks of heavy mixing. In the first embodiment of the invention, both inner'and outer blades are fixed in relation to each other and are attached at their upper ends to and rotate with a single drive shaft in the same direction. In this first embodiment, several predetermined flow patterns are possible, as illustrated in FIGURES 1-4. In the second embodiment of the invention, illustrated in FIGURE 5, the blades are placed one within the other as in the first embodiment but are mounted 'on'two separate concentric shafts. The inner and outer blades are driven such that the inner blademay be rotated independently in the same or in opposite directions from the outer blade, and the speeds of the two shafts can be the same or diiferent. -Ifithe configuration of the mixeris generally cone-shaped, it will foster the additional feature of allowing easy varying of the distance between the outer blade envelope .and theinterior surface of the receptacle by moving the blade set upward and downward along the axis, with resulting changes in the flow pattern, which will "hereinafter be discussed. If additional support for the blade set is desirable, a foot bearing supported by the lower portion .of the receptacle can be added.
In FIGURE .1 there @is shown a cylindrically shaped receptacle having an axis 11 and .a bottom portion 12 of hemispherical shape, as well as a discharge opening 13 with associated valve means 14. Outer blades 15 of helical ribbon design extend from a blade shaft 16 which is mounted concentric with the receptacle axis 11. Blade shaft 16.is driven .by any conventional means such as motor 17 and terminates at the point of attachment to the blades. Outer blades .15 trace a first envelope which is adjacent and closely corresponds to the shape of interior surface 18 of receptacle 10. Inner blades 19, also of helical ribbon design and also'mounted "on shaft 16, are positioned so that the second envelope traced by them is entirely within the first envelope traced by outer blades 15. In the showing of FIGURE 1, the outer blades 15 and inner blades 19 are helically wound in opposite direc- "blades '19. Maximum shear action takes place along all.
edges of the flow stream. It is also within the concept of the operation of the mixer shown in FIGURE 1 to reverse the direction of rotation and to move the mixture upwardly along the interior surface 18 by action of outer blades 15 and downwardly through the center. This would be advantageous if it is desired to expose a large amount of the mixture to a vapor space above its surface so that the mixture can be aerated ordeaerated.
To remove the mixture from receptacle 10, valve 14 is opened and the mixture is discharged through opening -13. Discharge is facilitated by rotation of the blades in a clockwise direction, for outer blades '15 will then force the mixture to the bottom of the receptacle 10 and through discharge opening 13. The fact that the pitch of outer blades 15 is greater than that of the inner blades 19 means that more mixture is forced down than can be lifted up and thus discharge is facilitated.
The mixing apparatus as shown in FIGURE 2 is like that of FIGURE 1 in operating principle, however, the receptacle and the envelope traced by the blade set are of conical shape. This mixer comprises a cone-shaped receptacle 20 disposed about a receptacle axis 21. The base is oriented upwardly and the bottom portion of the receptacle has a discharge port 23 and a valve means 24. Outer blades 25 conform to the shape of the receptacle and are mounted on shaft 26, driven by a conventional means such as a motor 27. Blades 25 trace an envelope whichis closely adjacent to and conforms with the shape of the receptacle interior surface 28. Also mounted on shaft 26, and subscribing a second cone-shaped envelope entirely within the first envelope, are inner blades 29. In the showing of FIGURE 2, inner blades 29 are helically wound in the opposite direction from outer blades 25. Thus, if the blades are rotated in a clockwise direction, the resulting flow pattern will be downwardly along the interior surface 28 as moved by blades 25, and then upwardly in the center of the receptacle as moved by blades 29. If the blade set of FIGURE 2 is rotated in the opposite direction, the outer blades will lift the mixture up and the inner blades will force it down, as described above with reference'to FIGURE 1.
In FIGURE 3 there is shown a mixer of design like that of FIGURE 1 including a receptacle 30 with axis .31 and a bottom portion 32 including a discharge opening 33 and a valve means 34. Outer blades 35 are mounted on a blade shaft 36 driven by a motor 37, and trace an outer envelope closely conforming to the shape of the receptacle interior surface 38. In FIGURE '1 the inner and outer blades are helically wound in opposite directions, but in FIGURE 3 .inner blades 39 and outer blades .35 are helically wound in the same direction. In the mixer shown in FIGURE 3, with the blade set being rotated in a clockwise direction, the flow path of the mixture is downwardly along the inner surface 38 as moved by outer blades .35, and also downwardly in the interior of the receptacle as moved by blades 39. To move upwardly the mixture must squeeze between the two downward flow streams or move in the extreme center of the receptacle along axis 31. This flow pattern provides an extremely large area of reactive surface and thus, the design fosters very eificient chemical reaction while mixing.
This blade arrangement is also ideal for use with ingredients which must be treated additionally immediately after mixing, for both outer blades 35 and inner blades 39 force the mixture downward and when valve 34 is opened the mixture will be extruded in a minimum time. Reversal of direction of rotation will cause the mixture to be thrown upward in the vapor space above its surface, with interior surface 48, the result consequent aeration, or deaeration if the space is evacuated.
In certain particular applications, it may be desirable to provide additional support for the blade set in the form of a foot bearing installed in the bottom portion of the receptacle. Such a foot bearing, shown in FIGURE 3 for convenience only, could consist of a journal 80 which will support the blade set by means of a stud shaft 81 fixedly attached to and rotating with the blade set. Such an arrangement is particularly desirable when extremely viscous materials are being mixed. However, the material being mixed should be of such properties as would not foul the bearing, or 'be adversely effected by any heat which may be generated by the bearing; preferably, it would provide some lubrication. Such a bearing as that above described could be provided for any of the mixers constructed in accordance with the present invention.
The mixing apparatus in a conical configuration possesses distinct advantagesover other shapes, and this is illustrated inFIGURE 4 wherein is shown a cone-shaped receptacle 40 having an axis 41, a discharge opening 43, and associated valve means 44. The blade set consists of outer blades 45 and inner blades 49, both mounted on a blade shaft'46 driven by conventional means such as a motor 47. The envelope swept by outer blades 45 again closely conforms ,to the shape of interior surface 48 of receptacle 40 and inner blades 49 trace an envelope entirely Within th'atof outer blades 45. If the blade set of the mixer of FIGURE 4 were positioned so that the outer blades described an envelope closely adjacent to would be a flow pattern identical to that of FIGURE 2. However, the mixer of .FIGURE 4 is provided with means for raising the blade set so that a plurality of predetermined spacings 50 can be established between the envelope traced by blades 45 and the interior surface 48. This is accomplished by conventional means such as a rack 51 attached to motor 47 and a worm gear 52 to raise and lower it. Inner blades 49 and outer blades 45 are helically wound in the same direction so that if the blade set is rotated clockwise, both blades will push the mixture downwardy. With a predetermined distance 50 established between the envelope traced by outer blades 45 and interior surface 48, an up- .ward flow'stream will be established along the interior wall 48 because it is now possible for a stream of mixture to squeeze upward there as well as between the two downward streams and in the center. This means that still another large area of shear surface is provided and even more efficientimixing and chemical reaction takes place. It is also within the concept of this invention to provide the arrangement of'FIGURE 4 with means to constantly reciprocate the blade set to provide still another desirable method o f mixing FIGURE Sis illustrative of a second embodiment of the instant invention which may be in any of the heretofore 'mentioned configurations, but is illustrated here in a most versatile form, the conical configuration. This mixing apparatus comprises a receptacle 60 disposed about an axis 61 and having atits bottom a discharge opening 63 and associated valve means 64. Outer blades 65 are supported and driven in rotation by a shaft 66, motor 67, and suitable. gear box 68. As in the previous models described, outer blades 65 trace an envelope conforming to the shape of interior surface 69 of receptacle 60, and shaft 66 terminates at the point of attachment to blades 65. Inner blades 70 are internal of and transcribe an envelope completely within that of outer blades 65. However, as opposed to the previously described embodiment, inner blades 70 are separately mounted and independently rotatable on a second drive shaft 71 which is concentric with drive shaft 66 and is driven by a motor 72 through gear box 68. Shaft 71 terminates at the point of attachment to blades 70. In order to achieve spacing 75 from interior surface 69, the blade set and the motor and driving mechanism are arranged to be raised and lowered by such means as a rack 73 driven by a worm gear 74 and can be caused to reciprocate by the same mechanism. Motors 67 and 72 are of the variable speed type and are reversible, so that it is possible to rotate blades and independently in opposite directions and at independently variable speeds. It is obvious from this arrangement that a multitude of flow patterns and characteristics can be obtained, including those described in connection with FIG- URES 1-4. Although in FIGURE 5 blades 65 and 70 have been shown helically wound in opposite directions, they could, of course, be Wound in the same direction. The advantages offered by this arrangement of FIGURE 5 are numerous and include precise control over the fiow stream and mixing characteristics to match a multitude of mixing tasks, including driving the ingredients to be mixed in a downwardly direction to cause squeezing upwardly of the flow streams and extremely high shearing action, or the converse to provide a boiling surface and maximum exposure to the vapor space above the mixture. In addition, by rotating both blades such that they drive downwardly the receptacle can be emptied in minimum time.
Apparatus designed in accordance with the instant invention, in addition to providing a most versatile mixing action, are easily adaptable to the accessories, such as sensing devices, which are well-known in the mixing art. For example, blades 65 and 70 may be provided with integrally installed accessories such as viscosity sensors and temperature sensors at 76 and 77. In this connection also the design of the blade set, having no elements projecting inwardly through the center of rotation and no center support column, adapts the mixing apparatus to lowering of accessories 78 through hollow drive shafts 66 and 71 along the mixer axis 61 so that instruments, such as thermocouples and viscosimeter probes, can be easily and quickly lowered to any point along the mixer axis.
Also, mixer blades 65 and 70 and the walls of receptacle 60 can be provided with passages through which heating and cooling fluids may flow.
It is thus seen that the instant invention provides an extremely versatile mixer which can provide a multitude of mixing characteristics without the use of :complicated accessories. The blades and receptacle cooperate to promote maximum agitation and shearing action, while promoting quick discharge of the mixture. In addition, the mixing apparatus of the instant invention is operable with standard accessories such as heating and cooling means and various sensing devices. Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
What is claimed as new and desired to be secured by Letters Patent of the United States is:
1. Mixing apparatus comprising a receptacle having a substantially vertical axis and an interior surface concentrically disposed about'said axis throughout the length thereof,
a mixing blade set having an axis of rotation coincident with said receptacle axis and comprising first blades of helical ribbon configuration tracing a first envelope in close proximity to said interior surface, 7
second blades of helical ribbon configuration in fixed relationship to said first blades and tracing a second envelope of radius correspondingly less than said first envelope and entirely within said first envelope,
a hollow shaft coincident with said receptacle axis and driven by said motor, said shaft being fixedly attached to and terminating at the upper portion of said blades, said blades being free of support throughout their entire length, and
7 means 'for sensing a condition in the receptacle inserted through said hollow shaft and communicating with the interior ofsaid receptacle. 2. Mixing apparatus comprising a receptacle having a substantiallyvertica'l axis and -a substantially cone-shaped interior surface concentrically disposed about said axis throughout the length thereof, the 'base of said conical shape being oriented upward, a mixing blade set having an axis of rotation coincident withsaid receptacle axis and comprising first blades of helical ribbon configuration tracing a substantially cone-shaped first envelope in close proximity to said interior surface, second'blades ofhelical ribbon configuration tracing a second envelope of radius correspondingly less than said first envelope and entirely within said first envelope, a motor, a shaft coincident with said receptacle axis and driven by said motor, said shaft being fixedly attached to and terminating at the upper portion .of said blades, said "blades being free of support throughout their entire length, and means for moving said blade set between a first "position wherein said first envelope is in close proximity to said interior surface and a plurality of second positions wherein said first envelope is spaced from said interior surface a distance such that said first envelope and said T interior surface cooperate to define and contain a predetermined ifiow stream therebetween.
3. Mixingapparatus comprising Ia receptacle having a substantially vertical axis and an interior surface :concentrically disposed about said axis throughout the length thereof a mixing blade set having an axis of rotation coincident withsaid receptacle axis and comprising first blades of helical ribbon configuration tracing a first envelope 'in close proximity to said interior surface,
a first shaft coincident with said receptacle :axis, said'first shaft being fixedly attached to and terminating at the uppermost portion-of said first blades, -said first blades being free of support throughout their entire length,
means for rotating said first shaft,
second'blades of helical ribbon con-figurationtrac- 'ing a second envelope of radiuscorresponding'ly less .thansaid first envelope and entirely within said first 'envelope,
'a second shaft coincident with said first shaft, said second shaft being fixedly attached to and terminating :at the :uppermost portion of :said second blades, saidsecond blades being free of .support throughout their entire zlength, and means for rotating :saidsecond .shaft.
4. The mixing apparatus of claim 3 wherein-said second shaft is a hollow TtlIbE communicating with the initerior of said receptacle whereby :a means for sensing a condition in the receptacle may be inserted therethrough.
'5. The mixing apparatus o'f claim 3 wherein said first i8 envelope and said receptacle are of substantially .cylindrical shape.
6. The mixing apparatus of claim 3 'whereinsaid dirst envelope and said receptacle are of substantially .conical .5 shape, the base of said conical shape being orientedaupward.
7. The mixing apparatus of claim-6 'furthercornprising means for moving said blade set between :a Ifirst position :wherein said first envelope is in close proximity to said inside surface and a plurality .of second 10 positions wherein said first envelope 'is spaced from said interior surface a distance such that said first envelope and saidinterior surface cooperate to define and contain a predetermined lflow :stream therebetween.
8. The mixing apparatus of claim 3 wherein said first blades and said second blades are helically wound in the same-direction.
9. The mixing apparatus of-claim SWherein said ifirst blades and said second blades are helically wound "in opposite directions.
10. The mixing apparatus of claim 3 wherein :said first blades are of ditferent'pitc'h than 'said' se con'd blades.
11. The mixing apparatus of claim 3 wherein :said receptacle includes a bottom discharge opening.
12. The mixing apparatus of claim 3 wherein said means for rotating said first shaft comprises means for selectively varying the speed of rotation -'of said first shaft,and means for selectively changing the direction ofn'otation of said firstshafh-and wherein said means for driving said second sh'a'ft comprises means for selectively varying the speed of *rotation of said second shaft, and means for selectively changing the direction of rotation ofsaid second shaft.
13. The mixing apparatus of claim 12 :further comprising means for moving said :blade set between a ifirst zp'os'ition wherein said first envelope is in cl'ose proximity to said inside surface and a plurality of second positions wherein said first envelope -is spaced from :sziid interior surface a distance such that said firs't envelope and said interior surface cooperate Ito define and contain a predetermined :flow stream therebetween.
'14. The mixing apparatus of claim .3 further vcomprising bearing means interposed between said blade set and the bottom portion of said receptacle.
References .Cited UNITED STATES PATENTS 116,855 7/1871 Monfort 259-21 1,049,600 1/1913 Rambeaud 2'59 133 1,734,632 11/1929 Merrill 259'1'U8 2,515,713 -7/1950 Johnson -259 r54 3,138,167 6/1964 Fisher -'259-=9 3,249,342 5/1966 'Mikkelsen 1259-424X FOREIGN PATENTS 608,164 4/1926 France.
ROBERT W. JENKINS, Primary Examiner.