GB1587564A

GB1587564A - Rotary surface aerator

Info

Publication number: GB1587564A
Application number: GB2551577A
Authority: GB
Original assignee: General Signal Corp
Current assignee: SPX Corp
Priority date: 1976-06-18
Filing date: 1977-06-17
Publication date: 1981-04-08
Also published as: JPS6130840B2; SE441088B; DE2727224C2; DE2727224A1; AU2393577A; CA1079874A; SE7706994L; FR2355182A1; JPS52156409A; FR2355182B1; AU510239B2

Description

(54) ROTARY SURFACE AERATOR (71) We, GENERAL SIGNAL COR PORATION, a corporation organized and existing under the laws of the State of New York, United States of America of High Ridge Park, Stamford, Connecticut 06094, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a rotary surface aerator.

In recent years surface aerators have been used quite extensively on the surface of liquid sewage for aerating the sewage. Typical of such aerators are those shown in U.S.

Patent Nos. 3,479,017 to Thikotter; 3,576,316 and 3,610,590 to Kaelin; and 3,741,682 to Robertson. Although such devices have functioned in a generally satisfactory manner, problems have been experienced with excessive splashing and misting, insufficient pumping and circulation, and clogging of the aerators during operation. Additionally, these prior art aerators 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.

According to the present invention there is provided a rotary surface aerator comprising a plurality of blades disposed in a circular array about a central axis and wherein each blade is spaced from the central axis and extends outwardly therefrom and transversely to a plane normal to said axis and has a tapered edge such that the extent of projection of the blade, in a direction parallel to the axis of rotation becomes progressively less as the blade extends outwardly, and wherein each of said blades has a flow inducing fin along the tapered edge thereof which fin extends transversely to the respective blade and is of tapering width with its widest portion at the part of the blade edge closest to the rotational axis of the aerator.

Described hereinafter is a preferred embodiment of the present invention which comprises a fluid surface aerator which includes a support disk adapted to be affixed to a rotating shaft in such a manner that it is maintained in a substantially perpendicular relationship with the shaft. A plurality of blades are affixed to the support disk in such a manner as to be spaced from the shaft and to extend above the upper surface of the support disk and below the lower surface of the support disk. The blades further extend outwardly from the circular outer edge of the support disk, and each blade has an upper edge which lies in a plane substantially parallel to the support disk and a lower edge which is tapered causing the blades to be widest at the portion closest to the rotating shaft and progressively more narrow as the blades extend 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 outwardly from the support disk. A cover means is affixed to the blades and spaced from the upper surface of the support disk for creating an air intake opening above the upper surface of the support disk and for reducing the amount of splashing caused by the rotation of the impeller near the surface of the liquid.

In another modified embodiment, the aerator further includes means for adjustably securing the blades to the support disk so that their degree of outward extension is adjustable, and further includes means for adjustably securing the cover means to the upper edges of the impeller blades.

As will be explained in the following descriptions, the embodiments briefly outlined above are capable of producing a relatively low spray profile thereby to avoid excessive splashing and misting of the liquid.

Furthermore, a significant increase in the degree of pumping and circulation of the liquid can be achieved as compared with impellers heretofore available. The embodiments operate in a relatively clog-free manner and permit easy access to the impeller interior, and have circulation and aeration characteristics which are very sensitive to the level of the liquid. Provision is made for permitting the diameter of the aerators to be varied, and the aerators are relatively simple in construction and therefore easy and inexpensive to manufacture.

Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein: Figure 1 shows a perspective view of one embodiment of rotary surface aerator according to the present invention Figure 2 shows a bottom plan view of the aerator shown in Figure 1; Figure 3 shows a partial cross-sectional schematic view shown in Figure 1; Figure 4 shows a cross-sectional view of a modified form of the aerator shown in Figure 1; and Figure 5 shows an end view of the aerator shown in Figure 4.

The surface aerator of the present invention will now be described in detail with reference to Figures 1 through 5 of the drawings. A rotary surface aerator 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 (not shown). The aerator 10 includes a support disk 14 having a circular outer edge 16 and upper and lower surfaces 18 and 20, respectively. The surfaces 18 and 20 are preferably planar, although bevelled 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 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 outwardly from the 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 the rotating shaft 12 and become progressively more narrow as the blade 24 extends outwardly from the support disk 14.

The blades 24 are preferably curved along their entire length as is shown in the drawings.

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 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, 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 disk 14 along the notched portion 32.

Each of the blades 24 includes a flow inducing 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 progressively more narrow as the blade 24 extends radially outwardly from the aerator. The fins 34 are also preferably curved to correspond to the shape of the blade 24.

The fins 34 and the blades 24 may be made of steel, in which case the fins may be welded to the blades 24 along the lower edge 28.

In the alternative, the fins 34 and the blades 24 may be made of cast aluminium and thus be a unitary structure.

A cover means in the form of a covering disk 38 is affixed to the 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 splashing caused by the rotation of the aerator 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 the centre of the disk.

This aperture defines the air intake opening and permits the covering disk 38 to surround the rotating 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 rotary surface aerator of the present invention will now be described in detail. In connection with this description like numerals will be utilized to identify like components. This second embodiment is identical to the first embodiment described above with the exception that in the second embodiment means are provided for adjustably securing the blades 24 to the support disk 14 so that the degree of outward 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 blades 24 so that the degree of outward extension of the blades 24 remains adjustable. For simplicity of illustration only, a planar blade has been shown in the embodiment shown in Figures 4 and 5.To achieve this adjustability, the blades 24 include a pair of flanges 44 and 46 along a stepped top edge of the blades 24. It should be understood that the flanges 44, 46 may also be utilized with blades having a curved configuration and that the flanges 44, 46 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 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 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 flanges 44, 46.However, if the plural mounting holes are contained in the disk 14 then only a single mounting hole 50 need be contained in each of the flanges 44, 46. A suitable fastener 52, such as a nut and a bolt, may be inserted through the desired mounting holes to properly position the blade 24 with respect to the support disk 14. In a like manner, two sets of aligned mounting holes 52 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 blades. Once again, it should be understood that the number of mounting holes 52 and the spacing between the mounting holes could be altered to correspond to the desired degree of adjustability. 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 adjustability. In this embodiment the blades 24 are preferably made of cast aluminium so that the flanges 44 and 46 and the blade portion 24 comprise a unitary structure.

In the operation of the rotary surface aerator of the present invention, the impeller 10 is positioned near the surface of the liquid to be aerated. Since the aerator 10 will normally not be lowered to such an extent as to submerge the support disk 14 during rotation, input air enters the aerator 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 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 characteristics of the aerator 10 may be adjusted rather easily by raising and lowering the aerator 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 increases the pumping and circulation action of the aerator 10 with respect to aerators which were heretofore available. Since the aerator 10 is of a relatively open construction which is most apparent from the bottom 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 aerator.

Should one desire to change the diameter of the aerator, it is merely necessary to reposition the fasteners 52 within the desired set of mounting holes. Thus, the diameter of the aerator may be easily adjusted after installation.

WHAT WE CLAIM IS: 1. A rotary surface aerator comprising a plurality of blades disposed in a circular array about a central axis wherein each blade is spaced from the central axis and extends outwardly therefrom and transversely to a plane normal to said axis and has a tapered edge such that the extent of projection of the blade, in a direction parallel to the axis of rotation becomes progressively less as the blade extends outwardly, and wherein each of said blades has a flow inducing fin along the tapered edge thereof which fin extends transversely to the respective blade and is of tapering width with its widest portion at the part of the blade edge closest to the rotational axis of the aerator.

2. A surface aerator as claimed in claim 1 wherein said blades are mounted around the edge of a generally circular support disk arranged to be rotated by means of a shaft engaged centrally of said disk and extending transversely thereto.

3. A surface aerator as claimed in claim 2 wherein said blades each extends from one side of said disk towards its respective said tapered edge and furthermore extends from the other side of said disk to provide support for a cover member which extends generally parallel to the plane of said disk at a spacing from said other side thereof for reducing the amount of splashing caused in use of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. disk 38 to the upper edges 26 of the blades 24 so that the degree of outward extension of the blades 24 remains adjustable. For simplicity of illustration only, a planar blade has been shown in the embodiment shown in Figures 4 and 5. To achieve this adjustability, the blades 24 include a pair of flanges 44 and 46 along a stepped top edge of the blades 24. It should be understood that the flanges 44, 46 may also be utilized with blades having a curved configuration and that the flanges 44, 46 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 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 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 flanges 44, 46. However, if the plural mounting holes are contained in the disk 14 then only a single mounting hole 50 need be contained in each of the flanges 44, 46. A suitable fastener 52, such as a nut and a bolt, may be inserted through the desired mounting holes to properly position the blade 24 with respect to the support disk 14.In a like manner, two sets of aligned mounting holes 52 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 blades. Once again, it should be understood that the number of mounting holes 52 and the spacing between the mounting holes could be altered to correspond to the desired degree of adjustability. 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 adjustability. In this embodiment the blades 24 are preferably made of cast aluminium so that the flanges 44 and 46 and the blade portion 24 comprise a unitary structure. In the operation of the rotary surface aerator of the present invention, the impeller 10 is positioned near the surface of the liquid to be aerated. Since the aerator 10 will normally not be lowered to such an extent as to submerge the support disk 14 during rotation, input air enters the aerator 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 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 characteristics of the aerator 10 may be adjusted rather easily by raising and lowering the aerator 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 increases the pumping and circulation action of the aerator 10 with respect to aerators which were heretofore available. Since the aerator 10 is of a relatively open construction which is most apparent from the bottom 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 aerator. Should one desire to change the diameter of the aerator, it is merely necessary to reposition the fasteners 52 within the desired set of mounting holes. Thus, the diameter of the aerator may be easily adjusted after installation. WHAT WE CLAIM IS:

1. A rotary surface aerator comprising a plurality of blades disposed in a circular array about a central axis wherein each blade is spaced from the central axis and extends outwardly therefrom and transversely to a plane normal to said axis and has a tapered edge such that the extent of projection of the blade, in a direction parallel to the axis of rotation becomes progressively less as the blade extends outwardly, and wherein each of said blades has a flow inducing fin along the tapered edge thereof which fin extends transversely to the respective blade and is of tapering width with its widest portion at the part of the blade edge closest to the rotational axis of the aerator.

impeller by rotation thereof at the surface of a liquid with the tapered impeller blade edges immersed in the liquid.

4. A surface aerator as claimed in claim 3 wherein said cover member comprises a generally annular disk having a central opening defining an air intake spaced from said other side of the first-mentioned disk.

5. A surface aerator as claimed in any of the preceding claims wherein the outward spacing of each blade from the centre of the arrangement is adjustable.

6. A surface aerator as claimed in any of the preceding claims wherein the blades are each curved in an outward direction from the centre of the arrangement.

7. A rotary surface aerator for aerating a liquid and adapted to be affixed to a rotating shaft, comprising: (a) a support disk having a circular outer edge and upper and lower surfaces; (b) means for affixing said support disk to said rotating shaft so that said support disk is maintained in a substantially perpendicular relationship with said shaft; (c) a plurality of blades; (d) cover means for creating an air intake opening above said upper disk surface and for reducing the amount of splashing caused by the rotation of said impeller near the surface of said liquid;; (e) means for adjustably securing said blades to said support disk so that said blades extend outwardly from said circular outer edge, extend above said upper disk surface and below said lower disk surface, and so that the degree of radial extension is adjustable, wherein each of said blades has an upper edge which lies in a plane substantially parallel to said support disk and each blade being tapered causing said blades to be widest at the portion closest to said rotating shaft and progressively more narrow as said blade extends out wardly from said support disk, and wherein each of said blades includes a flow inducing fin along the lower edge of the blade, said fins being tapered so as to be widest at the portion closest to said rotating shaft and progressively more narrow as said blade extends outwardly from said support disk;; and (f) means for adjustably securing said cover means to the upper edges of said blades so that said cover means is spaced from said upper disk surface and so that the degree of radial extension of said blades remains adjustable wherein each of said blades includes a flange portion along the upper edge thereof and wherein said means for adjustably securing said cover means to the upper edges of said blades includes a plurality of radially aligned mounting holes in one of said cover means and said flange portions and fastener means adapted to be inserted into one of said mounting holes to thereby adjustably secure said cover means to the upper edges of said blades.

8. A rotary surface aerator for aerating a liquid and adapted to be affixed to a rotating shaft, comprising: (a) a support disk; (b) means for affixing said support disk to said rotating shaft so that said support disk is maintained in a substantially perpendicular relationship with said shaft;; and (c) a plurality of blades affixed to said support disk and extending outwardly therefrom, each of said blades having an upper edge which lies in a plane sub stantially parallel to said support disk, and each of said impeller blades being tapered causing said blades to be widest at the portion closest to said rotating shaft and progressively more narrow as said blade extends outwardly from said support disk wherein each of said impeller blades is curved along its entire length in the outward direction, and wherein each of said blades includes a flow inducing fin along the lower edge of the blade, said fins being tapered so as to be widest at the portion closest to said rotating shaft and progressively more narrow as said blade extends outwardly from said support disk.

9. A rotary surface aerator for aerating a liquid and adapted to be affixed to a rotating shaft, comprising: (a) a support disk having a circular outer edge and upper and lower surfaces; (b) means for affixing said support disk to said rotating shaft so that said support disk is maintained in a substantially perpendicular relationship with said shaft;; (c) a plurality of blades affixed to said support disk in such a manner as to be spaced from said shaft when said support disk is affixed to said shaft, said blades extending outwardly from said circular outer edge, and extending above said upper disk surface and below said lower disk surface, wherein each of said blades has an upper edge which lies in a plane substantially parallel to said support disk and each of said blades being tapered causing said blades to be widest at the portion closest to said rotating shaft and progressively more narrow as said blades extend radially outwardly from said support disk, and wherein each of said blades includes a flow inducing fin along the lower edge of the blade, said fins being tapered so as to be widest at the portion closest to said rotating shaft and pro gressively more narrow as said blade extends outwardly from said support disk; and (d) cover means, affixed to said blades and spaced from said upper disk surface, for creating an air intake opening above said upper disk surface and for reducing the amount of splashing caused by the rotation of said impeller near the surface of said liquid.

10. A rotary surface aerator substantially as herein described with reference to the accompanying drawings.