Note: Descriptions are shown in the official language in which they were submitted.
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SURFACE ~ERATION IMæELLER
1. Background of the Invention
The present invention relates generally to rotating
impellers and more particularly to an impeller designed to
rotate near the surface of a liquid to aerate the liquid.
In recent years aerating impellers have been used
quite extensively on the surface of liquid sewage for aerating
the sewage. Typical of such aeration impellers are those
shown in U.S. Patent NosO 3,479,017 to Thikotter; 3,576,316 and
3,610,590 to Kaelin; and 3,741,682 to Robertson. Although such
10. devices have functioned in a generally satisfactory manner,
problems ha~e been experienced with excessive splashing and
misting, insufficient pumping and circulation, and clogging of
the impellers during operation. Additionally, these prior art
impellers have been of a fixed diameter, and thus if a larger
or smaller impeller were needed, an entire unit would have to
be substituted in the field.
Summary of the Invention
Accordingly, the present invention provides an
impeller for aerating a liquid which is adapted to be affixed
20. to a rotating shaft and includes a support disk having a cir-
cular outer edge. The support disk is affixed to the rotating
shaft in such a manner that it is maintained in a substantially
perpendicular relationship with the shaft. A plurality of
impeller blades are affixed to the support disk in such a
manner as to be spaced from the shaft and extend above the
upper surface of the support disk and below the lower surface
of the support disk. The impeller blades further extend
radially outwardly from the circular outer edge and have an
upper edge which lies in a plane substantially parallel to the i~
30. support dis~ and a lower edge which is tapered causing the
`~ blades to be widest at the portion closest to the rotating
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1. shaft and progressively more narrow as the blades extend
radially outwardly from the support disk. Additionally, each
of the impeller blades includes a flow inducing fin along the
lower edge of a blade which fins are tapered so as to be widest
at the portion closest to the rotating shaft and progressively
more narrow as the blade extends radially outwardly from the
support disk. A cover means is affixed to the impeller blades
and spaced from the upper surface of the support disk for creat-
ing an air intake opening above the upper surface of the support
10. disk and for reducing the amount of splashing caused by the
rotation of the impeller near the surface of the liquid. In
one embodiment the impeller includes means for adjustably
securing the impeller blades to the support disk so that the
degree of radial extension is adjustable and further includes
means for adjustably securing the cover means to the upper
edges of the impeller blades.
Objects of the Present Invention
Thus, an object of the present invention is the
provision of an impeller for aerating a liquid which will
20. produce a relatively low spray profile to thereby avoid
excessive splashing and misting of the liquid.
Another object of the present invention is the
provision of an impeller for aerating a liquid which will
significantly increase the pumping and circulation of the ~-
liquid with respect to impellers heretofore available.
A further object of the present invention is the
provision of an impeller for aerating a liquid which will
operate in a relatively clog-free manner and permit easy
access to the impeller interior.
30. Another object of the present invention is the
provision of an impeller for aerating a liquid having circulation
and aeration characteristics which are very sensitive to the
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1. level of the liquid.
Still another object of the present invention is the
provision of an impeller for aerating a liquid which has a pro-
vision for permitting the diameter of the impeller to be varied.
A still further object of the present inven~ion is
the provision of an impeller for aerating a liquid which is
relatively simple in construction and there~ore easy and
inexpensive to manufacture.
Other objects, advantages, and novel features of the
10. present invention will become apparent from the following
detailed description of the invention when considered in
conjunction with the accompanying drawings.
Brief Description of the Drawings
Figure 1 shows a perspective view of the surface
aeration impeller of the present invention.
Figure 2 shows a bottom plan view of the impeller
shown in Figure 1.
Figure 3 shows a partial cross-sectional schematic
view of the impeller shown in Figure 1.
20~ Figure 4 shows a cross-sectional view of a second
embodiment of the impeller shown in Figure 1.
Figure 5 shows an end view of the embodiment shown
in Figure 4.
Description of the Preferred Embodiments
The surface aeration impeller of the present invention
will now be described in detail with reference to Figures 1
through 5 of the drawings. A surface aeration impeller 10 for
aerating a liquid is adapted to be affixed to a rotating shaft
12. The shaft 12 may be connected to any suitable prime mover
30. (not shown). The impeller 10 includes a support disk 1~ having
a circular outer edge 16 and upper and lower surfaces 18 and 20,
respectively. The surfaces 18 and 20 are preferably planar,
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1. although beveled surfaces would clearly fall within the scope
of the present invention. Means are provided for affixing the
support disk to the rotating shaft 12 so that the support disk
14 is maintained in a substantially perpendicular relationship
with the shaft 12. This affixing means is preferably a hub 22
which may be affixed to the shaft 12 by means of a set screw.
A plurality of impeller blades 24 are affixed to the
support disk 14 in such a manner as to be spaced from the shaft
12. The impeller blades 24 extend radially outwardly from the
10. circular outer edge 16 and also extend above the upper disk
surface 18 and below the lower disk surface 20. Additionally,
each of the impeller blades 24 has an upper edge 26 which lies
in a plane substantially parallel to the support disk 14. Each
of the blades 24 also has a lower edge 28 which is tapered in
such a manner as to cause the blades 24 to be widest at that
portion 30 which is closest to tha rotating shaft 12 and become
progressively more narrow as the blade 24 extends radially out-
wardly from the support disk 14. The impeller blades 24 are
preferably curved along their entire length in the radial
20. direction. Although from a theoretical standpoint many types
of curved configurations might prove suitable, from an ease of
manufacture standpoint it has proved preferable to make this
curvature be of a fixed radius. It should be understood that
the use of planar blades also falls within the scope of the
present invention. As is most clearly shown in Figure 3, the
impeller blades 24 may include a notch 32 along the inner edge
30 which is adapted to receive the circular outer edge 16 of
! the support disk 14, so that the blades 24 may be securely
fastened to the support disk 14 in a dovetail fashion. Thus,
30. the blades 24 may be permanently affixed to the support disk
14. If for example, the blades 24 and the support disk 14 are
made of steel, then the blades 24 may be welded to the support
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1. disk 14 along the notched portion 32.
Each of the impeller blades 24 includes a flow induc-
ing fin 34 along the lower edge 28 of the blade 24. The fins
34 are also tapered so as to be widest at the portion 36 which
is closest to the rotating shaft 12 and so as to become pro-
gressively more narrow as the blade 24 extends radially outwardly
from the impeller. The fins 36 are also preferably curved to
correspond to the shaft of the blade 24.
The fins 36 and the blades 24 may be made of steel,
10. in which case the fins may be welded to the blades 24 along the
lower edge 28. In the alternative, the fins 36 and the blades
24 may be made of cast aluminum and thus be a unitary structure.
A cover means in the form of a covering disk 38 is
affixed to the impeller blades 24 and spaced from the upper
disk surface 18, for creating an air intake opening above the
upper disk surface 18 and for reducing the amount of sp]ashing
caused by the rotation of the impeller near the surface of the
liquid. The disk 38 preferably includes a circular outer edge
40 and a circular inner edge 42, which defines an aperture at
20. the center of the disk. this aperture defines the air intake
opening and permits the covering disk 38 to surround the ro-
tating shaft 12. Due to manufacturing considerations, both
upper and lower surfaces of the covering disk 38 are preferably -~
planar. In the embodiment shown in Figure 3, the covering disk
38 is permanently affixed to the top edges 26 of the blades 24,
preferably by welding.
¦ Referring to Figures 4 and 5, a second embodiment of
the surface aeration impeller of the present invention will now
be described in detail. In connection with this description
, 30. like numerals will be utili~ed to identify like components.
This second embodiment is identical to the first embodiment
described above with the exception that in the second embodiment
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1. means are provided for adjustably securing the impeller
blades 24 to the support disk 14 so that the degree of radial
extension of the blades 24 with respect to the disk 14 is
adjustable. Additionally, means are provided for adjustably
securing the covering disk 38 to the upper edges 26 of the
impeller blades 24 so that the degree of radial extension of
the blades 24 remains adjustable. For simplicity of illustra- -
tion only, a planar blade has been shown in the embodiment shown
in Figures 4 and 5. To achieve this adjustability, the impeller
10. blades 24 include a pair of flanges 44 and 46 along a stepped
top edge of the impeller blades 24. It should be understood
that the flanges 44 may also be utilized with blades having a
curved configuration and that the flanges 44 may be positioned
on either side of the blade. When planar blades are used,
gussets are preferably placed on the top surface of the blade
opposite the flange, to provide added stability for the blade.
The means for adjustably securing the impeller blades to the
support disk 14 includes three radially aligned mounting holes
48 in the support disk 14 for each of the blades 24. It should
20. be understood that if a further degree of adjustability is
desired, additional holes may be added and the spacing between
the holes may be changed. Additionally, the same result could
be achieved by placing plural mounting holes in the flange 44.
However, if the plural mounting holes are contained in the disk
14 then only a single mounting hole 50 need be contained in the
flange 44. A suitable fastener 52, such as a nut and a bolt,
~ may be inserted through the desired mounting holes to properly
;I position the blade 24 with respect to the support disk 14. In
a like manner, two sets of radially aligned mounting holes 52
30. are contained in the covering disk 38, and a pair of mounting
holes 54 are contained in the flange 46 to thereby adjustably
secure the covering disk 38 to the upper edges of the impeller
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1. blades. Once again, it should be understood that the numker
of mounting holes 52 and the spacing between the mounting holes
could be altered to correspond to the desired degree of adjust-
ability. Also, the plural mounting holes could be contained in
the flange 46 instead of the disk 38. Yet another possible
alternative would be to replace all but one set of the adjustable
mounting holes 52 and 48 with slots to provide radial adjust-
ability. In this embodiment the blades 24 are preferably made
of cast aluminum so that the flanges 44 and 46 and the blade
10. portion 24 comprise a unitary structure.
In the operation of the surface aeration impeller of
the present invention, the impeller 10 is positioned near the
surface of the liquid to be aerated. Since the impeller 10
will normally not be lowered to such an extent as to submerge
the support disk 14 during rotation, input air enters the impel-
ler through the aperture in the covering disk 38 defined by the
edge 42 and may pass through the space between the disk 38 and
the disk 14. Since the blades 24 are provided with a tapered
lower edge 28 and since the fins 36 are also tapered, as
20. discussed above, and assuming that the prime mover for the shaft
12 provides a fixed degree of rotational input speed, the mixing
power level and therefore the circulation and aeration character-
istics of the impeller 10 may be adjusted rather easily by rais- -
ing and lowering the impeller with respect to the surface of the
liquid. The use of the covering disk 38 in combination with the
flow inducing fins 36 creates a relatively low spray profile to
thereby avoid excessive splashing and misting of the liquid being -~
aerated. Furthermore, the shape of the blades 24 and the flow
inducing fins 36 significantly increase the pumping and circula-
30. tion action of the impeller 10 with respect to impellers which
were heretofore available. Since the impeller 10 is of a rela-
tively open construction which is most apparent from the bottom
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1. view shown in Figure 2, the impeller operates in a relatively
clog-free manner and permits easy access for servicing to the
interior of the impeller. Should one desire to change the -
diameter of the impeller, it is merely necessary to reposition
the fasteners 52 within the desired set of mounting holes.
Thus, the diameter of the impeller may be easily adjusted after
installation.
While there have been described what are at present
considered to be *he preferred embodiments of the present
10. invention, it will be obvious to those skilled in the art that
various changes and modifications may be made therein, without
departing from the invention, and it is, therefore, aimed in
the appended claims to cover all such changes and modifications
as fall within the true spirit and scope of the invention.
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