US2978233A - Stabilized impeller - Google Patents

Description

April 4, 1961 K. DAVEY 2,978,233

STABILIZED IMPELLER Filed March 24, 1958 2 Sheets-Sheet 1 KINGSLE) DAVE):

April 4, 1961 K. DAVEY 2,978,233

STABILIZED IMPELLER Filed March 24, 1958 2 Sheets-Sheet 2 Ah/zwrom KINGSLEY 0A V531 STABILIZED lM'PELLER Kingsley Davey, 72 Whitehall Court, St. Louis 17, Mo.

Filed Mar. 24, 1958, Ser. No. 723,406

7 Claims. (Cl. 259-96) The present invention relates generally to liquid mixing devices, and more particularly to'a novelstabilized impeller for providing an improved mixing action with a minimum tendency to gyrate or whiplaround its normal axis of rotation;

Briefly, it has been found that a conventional impeller mounted at the free end of a rotating shaft for stirring liquids in a vatytank, or similar container almost always tends to revolve in an orbit about the normal axis of the rotating parts. Past efforts to overcome this tendency toward undesirable whipping have included both the employment of an oversize shaft for mounting the impeller and the addition of a lower guide bearing for the shaft. An oversize shaft, however, will increase the weight of the stirring apparatus andwillalso impair its mixing efficiency, besides being costly where conditions require the shaft tobe of expensive alloy metal. The use of a submerged bearing, on the other hand, provides obvious difliculties of service and maintenance.

It is an object of the present invention, therefore, to

'provide a novel liquid mixing impeller which largely overcomes any tendency towhip.

It is another object of the invention to provide a novel liquid mixing impeller adapted to be mounted at the free end of a. relatively slender rotatable shaft and having self-stabilizing operating characteristics.

It is another object of the invention to provide a novel liquid mixing impeller adapted to develop a liquid pressure differential which is effective to overcome whipping tendencies in the impeller.

It is another object of the invention to provide a novel liquid mixing impeller incorporating radially extended blades surmounted by ahub plate and having an underlying stabilizer ring.

It is another object of the invention to provide a novel liquid mixing impeller provided with axially spaced stabilizer rings.

The foregoing, along with additional objects and advantages, will be apparent from the following description of a preferred embodiment of the invention.

' In the drawings: a

Figure 1 is a top plan view of an impeller constructed in conformance with the present invention;

Figure 2 is aside elevation thereof, portions being broken away in order to disclose details shown in fragmentary section;

Figure 3 is a vertical section taken generally along the line 33 of Figure 1', the impeller being illustrated in mounted position at the free end of a vertical shaft shown fragmentarily;

Figure .4 is an isometric View of a removed spoke;

Figure 5 is a plan view of a'removed bracket;

Figure 6 is a side elevation thereof;

Figure 7 is a diagrammatic representation of the impeller of Figure 1 in, typical use as a stirring device;

Figure 8 is a top plan view of another impeller con structed in conformance with the present invention;

Figure 9 is a vertical section taken generally along 2,978,233 Patented Apr. 4, 1961 the line 9-9 of Figure 8, the impeller being illustrated in mounted position at the free end of a vertical shaft shown fragmentarily; and

Figure 10 is a diagrammatic representation of the impeller of Figure 8 in typical use as a stirring device.

Referring more particularly to the drawings by means of the reference numerals shown thereon, the numeral ll) designates generally one type of stabilized impeller constructed in accordance with the teachings of the present invention. The impeller it) includes a hub 12 provided with a central bore 14 for receiving a rotatable shaft 16. Keyways l8 and 20 formed in the hub 12 and in the shaft 16, respectively, accommodate an elongated key 22 retained by means of a set screw 24 inserted through a threaded hole 26 in the hub 12.

A plurality of spokes 28 disposed equidistantly about the periphery of the hub 12 are secured to the latter, as by welding, so as to extend radially therefrom as clearly indicated in Figure l. The spokes 28 here illustrated take the form of flat plates, as illustrated in Figure 4. Preferably, the spokes 28 are disposed at an inclination to a plane perpendicular to the axis of rotation of the hub 12, whereby they may serve as vanes for accommodating a vertical flow of liquid as the impeller It) is rotated. This arrangement of the vanes or spokes 28 is shown clearly in the sectional view of Figure 3. An upper stabilizing ring 3t having the form of a relatively short cylindrical sleeve is secured, as by welding, to the outer ends of the severalspokes 28 so as to be concentric with the hub 12.

The impeller 10 includes an even number of peripheral blades comprising equal but alternately pitched pluralities of downwardly directed blades 32 and upwardly directed blades 34. The blades 32 and 34 are generally indicated, in this instance, taking the form of arcuately bent straps. They differ, however, in having their inner ends beveled at opposite angles for achieving the aforementioned upward and downward disposition relative to their main plane of rotation. Thus, each blade 32 and 34 is provided at its inner end with both an upper blade bracket 36 and a lower blade bracket 38, these brackets being identical, except of opposite hand. An upper blade bracket 36, shown removed in Figures 5 and 6, is seen to comprise an arcuate base plate lit and a side gusset 42. The curvature of the base plate 40 corresponds to the outside of the stabilizing ring 30, and matching holes are provided in these members for receiving bolt assemblies 44.

As is clear from the illustration, the several blades 32 and 3:4 are supported from the upper stabilizing ring 30 by bolted attachment of the blade brackets 36 thereto. The lower blade brackets 38 are similarly secured to a lower stabilizing ring 46, similar in size and shape to the upper stabilizing ring Ml. Between the rings 30 and 46 is an open space 48.

Figures 8 through 10 of the drawings illustrate an impeller 54), also constructed in accordance with the teachings of the present invention, but of modified form relative to the above-described impeller ltl.

The impeller 56 differs from the impeller 16 primarily in having a solid hub plate 52 surmounting the blade structure at the inner ends of the blades in place of an upper ring such as the ring 30 in the impeller ill. Thus, as is clear from Figures 8 and 9, the hub plate 52 forms a solid annulus integral with the lower end of a hub 54 having a central bore 56 for receiving a rotatable shaft 53. Keyways 6i) and 62 formed in the hub 54 and in the shaft 58, respectively, accommodate an elongated key 64 retained by means of a set screw 66 inserted through a threaded hole 67 in the hub 54.

The impeller 50 has an even number of peripheral blades comprising equal but alternately pitched pluralities 3 of downwardly directed blades 68 and upwardly directed blades 70. As here illustrated, the blades 68 and 70 take the general form of straight blades given a backward sweep, as well as an upward or downward twist, from points adjacent their attachment to the hub plate 52. Each blade'68 or 70 is provided with a radially inwardly extending tab 72 at its upper edge and a downwardly extending tab 74 formed arcuately as clearly shown in Figure 8. These tabs 72 and '74 form integral portions of the blades 68 and 70 and differ from one another oni y in being adapted to conform to the upward or downward twist of their respective blades.

The blades 68 and 70 are secured in alternation to the hub plate 52 by means of bolt assemblies '76. The lower tabs 74 of the blades are similarly secured to a stabilizing ring 78 disposed in coaxial relation to the extended axis of the shaft 58.

Each of the stabilizing rings 30, 46 and 78 is defined by the rotation of a thin rectangle about the relatively distantly spaced hub axis, as is obvious from the drawings.

In use, either the impeller or the impeller 54) is normally secured to the lower end of a shaft, such as the shafts 16 or 58, and then disposed in a tank T containing a liquid L to be agitated or mixed. This arrangement, depicted diagrammatically in Figures 7 and 10, enables the particular rotating impeller to provide an efficient mixing action resulting from the form and relative disposition of its oppositely upwardly and downwardly directed blades. Of particular significance in the present invention, however, are the forces which prevail centrally or inwardly of the blades of the impellers 10 and 50.

Directing attention to this area, therefore, and noting the major currents of flow within the tank T as indicated generally by the directional arrows of Figures 7 and 10, it is evident that liquid L is caused to move downwardly at the center of the tank T along the shafts 16 and 58 toward the impeller hubs. At the same time, liquid rises from the region directly below the centers of the impellers. In the case of the impeller 10, the downward flow continues through the upper stabilizing ring 30 to meet the upward flow through the lower stabilizing ring 46. These two currents of flow merge at the open space 48 between the rings 30 and 46 and the resulting outwardly expanding merged flow is picked up by the inner ends of the blades 32 and 34- for outward propulsion.

It may be noted that the inclined arrangement of the spokes 28 in the impeller 10 is primarily for conformance with the above-described flow pattern, and not for instigating or maintaining it. In other words, the primary function of the spokes 28 is to support the portions of the impeller 10 outwardly of the hub 12 without inhibiting or restricting the aforementioned flow pattern. It is recognized, however, that under certain circumstances it may be desirable to avail the impeller 10 of flow impetus obtainable from the vane-like spokes 28. To this end, then, it is apparent, not only that the vanes 28 may be positioned in different attitudes, but also that similar vanes may be incorporated in the lower stabilizer ring 46.

The impeller 54), as previously indicated, eliminates the upper open ring corresponding to the ring 30 in the impeller 10 and provides instead the solid hub plate 52. The effect of this is to deflect the downwardly moving central current of liquid before it meets the upwardly moving current that rises through the lower ring 78. As a result, the deflected downwardly moving current enters the blade region from above and is directed generally toward the lower corners 80 of the tank T. Thus, the impeller 50 is particularly useful where corner scouring action is necessary to prevent pile-up of solids in the corners 80. By proper placement of the impeller relative to the lower tank corners, along with appropriate proportioning of tank and impeller sizes, an effective cooperation is obtained which results in improved efliciency of mixing.

Under any of the flow conditions described above, it is evident that a constant static liquid pressure will normally prevail at the outer surfaces of the stabilizer rings 30, 46, and 78. A different pressure will exist within these rings, however, due to the relatively high velocity of fluid flow therethrough. It has been found in respect to both the impeller 10 and the impeller 50 that this pressure differential between the inside and the outside of the rings 30, 46, and 78 provides effective stabilization which overcomes any tendency of the impellers to gyrate or whip. This stabilization not only increases the mixing efficiency, but also extends the life of the rotating parts.

Clearly, there has been provided a stabilized impeller which fulfills the objects and advantages sought therefor.

It is to be understood that the foregoing description and the accompanying drawing have been given by way of illustration and example. It is further to be understood that changes in form of the elements, rearrangement of parts, and the substitution of equivalent elements, all of which will be apparent to those skilled in the art, are contemplated as being within the scope of the present invention, which is limited only by the claims which follow.

What is claimed is:

1. A stabilized impeller of the kind described adapted to materially reduce shaft whip comprising a shaft receivable hub; a hollow cylindrical stabilizing member defined by the rotation of a thin rectangle about the relatively distantly spaced hub axis and spaced axially from,

but coaxial with, said hub, the space between said cylinder and said hub being axially open and being in communication through said cylinder with the axial extremity of said cylinder; means connecting said cylindrical member to said hub; and a plurality of spaced blades carried by said hub and extending between said hub and said cylinder and extending freely beyond said cylinder and hub in a generally radial outward direction.

2. The impeller of claim 1 wherein the blades, hub and cylinder are rotatable as a unit.

3. A stabilized impeller of the kind described adapted to materially reduce shaft whip comprising a shaft receivable hub; a cylindrical stabilizing member defined by a thin cylindrical wall and spaced from, but coaxial with, said hub; means connecting said cylindrical member to said hub; and a plurality of spaced blades attached to and extending between said hub and said cylindrical stabilizing member and radially outwardly therefrom; said hub being flared to a diameter approximately equal to a diameter of said cylindrical stabilizing member.

4. A stabilized impeller of the kind described adapted to materially reduce shaft whip comprising a shaft receivable hub; a first cylindrical stabilizing member defined by a thin cylindrical wall and spaced axially from, but coaxial with, said hub; a second cylindrical stabilizing member, the space between said first cylindrical member and said second cylindrical member being axially open and being in communication through each cylindrical member with the respective axial extremity of said cylindrical member defined by a -thin cylindrical wall coaxial with and spaced axially from said first cylindrical stabilizing member; means drivingly connecting said cylindrical members to said hub; and a plurality of spaced blades attached to one of said cylindrical stabilizing members and extending between said cylindrical stabilizing members and extending freely beyond said cylindrical members in a generally radial outward direction.

5. The impeller of claim 4 in which the cylinders are attached to the hub by spokes.

6. A stabilized impeller of the kind described adapted to materially reduce shaft whip comprising a shaft; a stabilizing cylinder defined by a thin cylindrical wall coaxial with and radially spaced from said shaft; a hub attached to said shaft and forming a top for said stabilizing cylinder; means connecting said cylinder to. said hubi a plurality of spaced impeller blades mounted between said cylinder and said top and serving to space said cyllizing sleeve circumscribing the spoke means, a second 15 thin-walled cylindrical stabilizing sleeve disposed coaxially with the first-mentioned stabilizing sleeve and axially wholly beyond the innermost ends of the impeller blades and means drivingly connecting said sleeves to said hub.

References Cited in the file of this patent UNITED STATES PATENTS 1,031,666 Richmond ..4 July 2, 1912 2,697,589 Davey Dec. 21, 1954 2,816,744 Penther Dec. 17, 1957 FOREIGN PATENTS 872,198 Germany Mar. 30, 1953 365,420 Great Britain Jan. 21, 1932 607,392 Great Britain Aug. 30, 1948

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