Abstract:
An aerating propeller for attaching to the end of a drive shaft includes blades having a chamber to receive a flow of fluids from a conduit in a drive shaft. A trailing face of the blade includes a first opening into the chamber to permit the flow of fluids in the chamber to exit the propeller and a tip of the blade includes a second opening extending into the chamber to permit the flow of fluids in the chamber to exit the propeller. The first opening of the first blade is aligned generally in the same plane with the leading face of the second blade which follows the first blade when the propeller is rotated.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to a submersible mixing propeller used to introduce and mix a fluid (air, other suitable gasses and/or liquids) into liquids and to mix liquids and solids in those liquids. 
         [0002]    Submersible mixing propellers are used as an aerator to aerate a liquid (that is introduce fine bubbles of air, or other gas, to intermix with the liquid) while simultaneously mixing the liquid with the air (or other gas) and also mixing the liquid (including solids suspended therein) into which the propeller is submerged. They are commonly used in industrial applications, including in waste water treatment plants to mix and aerate the waste liquids to facilitate digestion of waste in those liquids. It is important in achieving maximum efficiency of the digestion process to provide significant mixing of the waste water liquid and solids contained therein as well as to introduce air or other suitable gasses into the waste water in a manner which facilitates the mixing of the air or other suitable gasses with the waste water. Preferably the mixing propeller not only causes significant mixing of the liquids and solids, but also introduces the air and/or other suitable gases into the liquid in fine bubbles to assist in the absorption process with the liquid. The air and/or other suitable gasses suspended in the liquid is important as oxygen in the air or other suitable gasses is used by bacteria and other microscopic organisms in the process of digestion of the waste solids and decomposition of organic matter in the water in order to clean the water. 
         [0003]    Such propellers can also be immersed into a first liquid and used to introduce and mix a second liquid into the first liquid. A mixture of air (or other gas) and a second liquid may also be introduced and mixed with the first liquid. 
         [0004]    The application is also directed to a propeller that is suspended in a liquid to both mix that liquid and introduce fluids into the liquid in a manner which maximizes the absorption of the fluids into the liquid. The propeller is designed to provide both axial and radial flow to the liquid. Openings in the propeller for introducing fluid into the liquid are positioned optimally, as are the blades with respect to each other, to ensure the creation of fine bubbles of air or gas discharged into the liquid to physically contact the propeller as it spins. The shape of the blades of the propeller further assist in the mixing and aerating process undertaken by the propeller, the suction of fluid from the propeller openings into the liquid, and the axial and radial flow caused by rotation of the propeller. 
         [0005]    It should be understood that while the term “air” is used in this description that term includes any other suitable gas or mixtures of gases as would be apparent to one skilled in the art. Similarly the use of the term “gas” includes air and any suitable mixtures of gases. The use of the term “fluid” means either a gas (including air), a liquid or a mixture of gas and liquid. 
         [0006]    In an aspect of the invention a submersible mixing propeller for dispersing and mixing a fluid in a liquid, the propeller having an axis of rotation, includes an input for receiving a flow of fluid, first and second blades having a pressure side, suction side, tip, root section, leading face and a trailing face and a chamber communicating with the input for receiving the flow of fluid from the input. The trailing face comprises a first opening extending into the chamber to permit the flow of fluid in the chamber to exit the propeller. The tip comprises a second opening extending into the chamber to permit the flow of fluid in the chamber to exit the propeller. The suction side is angled from a plane perpendicular to the axis of rotation in a direction toward the pressure side when moving from the leading face to the trailing face. The first opening of the first blade is aligned generally in the same plane with the leading face of the second blade which follows the first blade, when the propeller is rotated. 
         [0007]    In a further aspect of the invention the leading face is curved rearwardly along its length in a direction away from the direction of rotation of the propeller. 
         [0008]    In another aspect the width of the leading face is greater than the width of the trailing face such that the pressure side and suction side are closer together at the trailing face as compared to the leading face. 
         [0009]    Optionally, the pressure side is angled from a plane perpendicular to the axis of rotation in a direction toward the suction side when moving from the leading face to the trailing face. The angle of the suction side from the said plane may be greater than the angle of the pressure side from the said plane. 
         [0010]    In a further embodiment the suction side is located at a lower region of the blade and is angled upwardly and the pressure side is located at an upper region of the blade and angled downwardly. The suction side may be located at an upper region of the blade angled downwardly and the pressure side may be located at a lower region of the blade angled upwardly. 
         [0011]    In a further aspect of the invention the trailing face is curved rearwardly along its length in a direction away from the direction of rotation of the propeller and wherein the amount of curvature of the leading face is less than the amount of curvature of the trailing face such that the distance between the leading face and the trailing face is greater at the tip as compared to the root section of the blade. 
         [0012]    In another embodiment the first opening of the first blade is configured to direct the flow of fluid from the chamber rearwardly in a direction away from the direction of rotation of the propeller to contact the leading edge of the second blade. Optionally, the second opening of the first blade is configured to direct the flow of air from the chamber radially and rearwardly to contact the leading edge of the second blade. 
         [0013]    The number of blades may be four, oriented symmetrically about the axis of rotation. 
         [0014]    In another embodiment the suction side is angled sufficiently to provide axial flow of the liquid when the propeller is rotated. The angle may between 5 degrees and 17 degrees from the said plane. The angle may be about 6.95 degrees from the said plane. 
         [0015]    As a further embodiment the angle of the suction side from the said plane is greater than the angle of the pressure side from the said plane wherein the pressure side is angled sufficiently to provide axial flow of the liquid when the propeller is rotated. The angle may be between 1 degree and 10 degrees from the said plane. The angle may be about 1.30 degrees from the said plane. 
         [0016]    In a further embodiment the plane defined by the leading face is oriented generally parallel with the axis of rotation of the propeller. 
         [0017]    In another embodiment the plane defined by the trailing face is oriented generally parallel with the axis of rotation of the propeller. 
         [0018]    In another embodiment the width of the blade between the leading face and the trailing face at the tip is greater than the width of the blade between the leading face and the trailing face at the root section. 
         [0019]    In another embodiment an submersible mixing propeller adapted to be rotated about a central axis, includes an intake, a plurality of hollow propeller blades radially extending outwardly from the central axis and connected to the intake, the propeller blades having a pressure side, suction side, tip, root section, leading face and a trailing face. The pressure side is oriented at an angle from a plane perpendicular to the axis of rotation in a direction toward the suction side when moving from the leading face to the trailing face. The suction side is oriented at an angle from a plane perpendicular to the axis of rotation in a direction toward the pressure side when moving from the leading face to the trailing face. A first discharge opening in the trailing face and a second discharge opening in the tip are also provided. The trailing face of a first blade is aligned generally in the same plane with the leading face of the second blade which follows the first blade such that when the propeller is rotated in use liquid exiting the discharge opening of the first blade is struck by the leading edge of the second blade. The angled orientations of the pressure side and the suction side cause an axial flow of the water in which the propeller is submersed. 
         [0020]    In a further embodiment of the invention a mixer for aerating and mixing a liquid includes a propeller, a shaft connected to the propeller, a motor connected to the shaft for imparting rotational force from the motor to the propeller through the shaft, a conduit in the shaft for transmitting a flow of gas to the propeller. The propeller includes at least one blade having a pressure side, suction side, tip, root section, leading face and a trailing face. The propeller includes a chamber connected to the conduit for receiving a flow of gas from the conduit. The trailing face includes a first opening extending into the chamber to permit the flow of gas in the chamber to exit the propeller. The tip includes a second opening extending into the chamber to permit the flow of gas in the chamber to exit the propeller. Optionally the shaft comprises an intake opening for receiving the flow of gas into the conduit in the shaft. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a top perspective view of the propeller of a preferred embodiment of the subject invention; 
           [0022]      FIG. 2  is a bottom perspective view of the propeller of  FIG. 1 ; 
           [0023]      FIG. 3  is a top view of the propeller of  FIG. 1 ; 
           [0024]      FIG. 4  is a side view of the propeller of  FIG. 1 ; 
           [0025]      FIG. 5  is a cross-sectional view showing the outer periphery and internal chamber of the propeller of  FIG. 1 , and 
           [0026]      FIG. 6  is a side view of the propeller of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Referring to  FIGS. 1 and 2 , propeller  10  is shown in a top perspective view ( FIG. 1 ) and a bottom perspective view ( FIG. 2 ). Propeller  10  is designed to be attached to a shaft (not shown) at an end with the shaft attached to an appropriate motor to impart rotational motion on the shaft and propeller  10  about axis  12  in the direction of rotation  14 . That is, to cause rotation of blades  18  in the direction of arrow  20 . 
         [0028]    Propeller  10  includes four lateral blades  18  arranged symmetrically about axis  12  as seen best in  FIG. 3 . When viewed from the side as in  FIG. 4  blades  18  are generally perpendicular to axis  12 , with some modification as discussed below. 
         [0029]    Propeller  10  further includes upper extension  22  into which hollow threaded portion  24  is attached. Threaded portion  24  includes threads designed to mate with internal threads of the shaft (not shown) to attach propeller  10  through the shaft to a motor to rotate Propeller  10  in the direction of rotation  14 . 
         [0030]    Each blade  18  is comprised of upper surface or pressure side  26 , lower surface or suction side  28 , root section  30 , tip  32 , leading face  34  and trailing face  36 . 
         [0031]    Referring to  FIG. 3 , both leading face  34  and trailing face  36  are curved rearwardly in a direction away from the direction of rotation  14 . It can be seen that the degree of curvature of leading face  34  is less than a degree of curvature of trailing face  36 . This causes the distance between face  34  and face  36  to be less near root section  30 , as compared to tip  32 . This creates a relatively bulbous tip  32  of blade  18 . 
         [0032]    Leading face  34  includes outer extension  37  which extends outwardly beyond tip  32 . Extension  37  is an optional component and provides additional impingement against the liquid and the fluid exiting from openings  40  and  42 , as discussed below. 
         [0033]    Referring to  FIGS. 4 and 6 , upper surface (pressure side)  26  is angled upwardly from a plane  50  perpendicular to axis  12 . This orientation of surface  26  means that upper surface (pressure side)  26  is lower adjacent leading face  34  as compared to trailing face  36 . The preferred angle  48  between the plane perpendicular to axis  12  and the plane defined by upper surface (pressure side)  26  is about 1.30 degrees. Although a range of angles between about 1 and 10 degrees is also suitable. 
         [0034]    Lower surface (suction side)  28  is also angled upwardly from a plane  50  perpendicular to axis  12 . This orientation of surface  28  means that lower surface (suction side)  28  adjacent leading face  34  is lower than lower surface (suction side)  28  adjacent trailing face  36 . The preferred angle  52  between plane  50  and the plane defined by lower surface (suction side)  28  is about 6.95 degrees. Although a range of angles between about 5 and 17 degrees is also suitable. In a preferred embodiment angle  48  of upper surface (pressure side)  26  is less than angle  52  of lower surface (suction side)  28 . 
         [0035]    In this embodiment the said angle of Lower surface (suction side)  28  is greater than the said angle of upper surface (pressure side)  26  which is a preferred orientation. 
         [0036]    The orientation of upper surface (pressure side)  26  and lower surface (suction side)  28  in this manner, with angle  48  of upper surface (pressure side)  26  is less than angle  52 , means that the distance between upper surface (pressure side)  26  and lower surface (suction side)  28  is less adjacent trailing face  36  as compared to the distance between upper surface (pressure side)  26  and lower surface (suction side)  28  adjacent leading face  34 . 
         [0037]    Referring to  FIG. 5 , each of blades  18  is hollow with chamber  38  extending Into and connecting with each blade  18  of propeller  10 . Threaded portion  24  includes hollow channel  44  ( FIG. 3 ) which is connected to channel  38 . The shaft connecting threaded portion  24  with the drive motor likewise contains a hollow channel which connects to hollow channel  44 . The opposite end of the drive shaft contains a plurality of openings which permit fluid to enter the hollow channel of the drive shaft and flow into chamber  38 . 
         [0038]    Each blade  18  includes two openings connected to chamber  38 , a rearward opening or first opening  40  and an outer opening or second opening  42 . Opening  40  is positioned within trailing face  36  and faces rearwardly toward the leading face of a blade  18  of propeller  10  to the rear of blade  18  containing a particular opening  40 . Opening  40  is rectangular in shape positioned within trailing face  36  with an root section adjacent root section  30  of blade  18 . 
         [0039]    Opening  42  is positioned within tip  32  facing outwardly from axis  12 . Opening  42  is positioned within tip  32  adjacent leading face  34  at one end and with its opposite end near trailing face  36 . Opening  42  is generally rectangular in shape, although due to the angling of upper and lower surface (suction side)s  26  and  28  as discussed above, opening  42  is somewhat wider at its end adjacent leading face  34  as compared to its opposite end. 
       Operation 
       [0040]    Propeller  10  is designed to be immersed in a liquid to provide both mixing of the liquid and aerating of the liquid, that is introducing air into the liquid. One useful application is in the mixing and aeration of municipal waste tanks to enhance the breakdown of organic waste by bacteria which need the oxygen in the introduced air to properly digest that material and to multiply. although the submersible mixing propeller can be used to introduce and mix various fluids in a liquid in which the propeller is submerged. 
         [0041]    As discussed above, propeller  10  is designed to be rotated in the direction of arrow  20 . A suitable motor (not shown) is connected to propeller  10  by means of a drive shaft, also not shown. The drive shaft is hollow with the hollow opening connected to the hollow channel  44  which, in turn, is connected to chamber  38 . 
         [0042]    Upon rotation of propeller  10 , fluid (in the case of aeration, the fluid is air) is either forced down or drawn down the hollow interior of the drive shaft into channel  44  and then into chamber  38 . Due to the centrifugal forces on the fluid within propeller  10  as it rotates, the fluid in chambers  38  of each blade  18  is forced out of openings  40  and  42 . Fluid exiting chamber  38  through opening  40  exits rearwardly striking the leading face  34  of blade  18  (including optional extension  37  if utilised) which follows the blade  18  of that particular opening  40 . That leading face  34  (and optional extension  37 ) contacts the fluid exiting opening  40  which splits the fluid into fine bubbles to assist in dispersing the fluid in the liquid in which propeller  10  is immersed. 
         [0043]    Fluid exiting chamber  38  through opening  42  is flung outwardly into the liquid generally in a lateral direction perpendicular to axis  12 . Fluid exiting chamber  38  through opening  42  is thereby widely dispersed away from propeller  10  with a portion of the fluid being struck by leading face  34  (and optional extension  37  if utilised) of blade  18  following that opening  42  further facilitating the dispersal of the fluid from chamber  38  through opening  42  in a wide direction away from propeller  10 . 
         [0044]    As propeller  10  rotates in the direction of arrow  20 , the angle of upper surface (pressure side)  26  creates an additional physical contact with the liquid, in addition to the contact caused by leading face  34 . The contact of upper surface (pressure side)  26  with the liquid causes the liquid to flow axially in a direction generally parallel with that of axis  12 , in an upward direction. 
         [0045]    The angle of lower surface (suction side)  28  creates a suction beneath blades  18  as propeller  10  is rotated in the direction of arrow  20 , which sucks the liquid along lower surface (suction side)  28  in a direction from an area adjacent leading face  34  toward and past trailing face  36  which also causes the liquid to move generally axially in a direction perpendicular to axis  12  and upwardly from propeller  10 . This also provides thrust which makes propeller  10  run more smoothly. 
         [0046]    The upward movement of the liquid past propeller  10  acts to mix the liquids and also to facilitate mixing of the fluid with the liquid as the liquid is drawn past propeller  10  as fluid is leaving propeller  10  through openings  40  and  42 . 
         [0047]    Fluid exiting openings  40  and  42  moves generally in a lateral direction causing mixing of liquid located generally laterally of propeller  10 , that is perpendicular to axis  12 . On the other hand, the angles of upper surface (pressure side)  26  and lower surface (suction side)  28  cause an upward movement of liquid as propeller  10  is rotated. This simultaneous lateral mixing (i.e. radial mixing) and upward mixing (i.e. axial mixing) provides significant benefits as compared to propellers which mix liquid in only one direction, either radially or axially. Mixing is further enhanced due to the positioning of opening  40  with respect to leading face  34  of the following blade  18  which causes fluid leaving opening  40  to be struck by leading face  34  to further enhance the mixing process of fluid in the liquid further enhancing the operation of propeller  10  to aerate that liquid. 
         [0048]    Also beneficial to the mixing of the liquid and mixing of the liquid with the fluid is the curvature of leading face  34 , which is curved rearwardly in a direction away from the direction of rotation  14 . Furthermore, blades  18  at their tip are wider than at their root section to form a bulbous tip. As propeller  10  turns in the direction of arrow  14 , the liquid accelerates across leading edge  34  creating an area of high pressure in front of and on top of each blade  18 . The curvature of leading edge  34  accelerates the liquid along leading edge  34  outwardly toward extension  37 . Liquid is also accelerated across upper surface (pressure side)  26  and lower surface (suction side)  28  of each blade  18  toward tip  32  of each blade  18 . 
         [0049]    This high pressure stream of liquid accelerates across openings  40  and  42  to create a low or negative pressure area within chamber  38 . That negative pressure draws fluid down the hollow shaft into chamber  38  and the fluid is then flung outwardly by centrifugal force due to the rotation of propeller  10 . The fluid leaving openings  40  and  42  are sheared by the blade  18  immediately behind the openings  40  and  42  through which the fluid exists. The fluid leaving opening  40  is sheared by extension  37  and the outer portion of leading face  34  whereas the fluid leaving opening  40  is sheared by the inner part of leading face  34 . This creates very fine bubbles of fluid leaving these openings  40  and  42  for improved oxygen absorption into the liquid. 
         [0050]    It should further be noted that the combination of the perpendicular, relatively blunt, configuration of leading face  34 , the generally bulbous tip  32  of blades  18  and the curvature rearwardly of leading face  34  cause the liquid in which the propeller is submerged to travel across blades  18  and along leading face  34  in a manner which creates streams of higher pressure of the liquid in front of and on top of each blade  18 . The higher pressure streams of liquid flows past openings  40  and  42  as propeller  10  is rotated in the direction of arrow  14 . This creates a region of lower pressure within chamber  38  which draws the fluid down the hollow shaft (not shown) through chamber  38  and out openings  40  and  42  into the liquid. This facilitates the dispersing and mixing of the fluid with the liquid. 
       Alternatives 
       [0051]    An alternative preferred embodiment provides an opposite axial flow as compared to the embodiment discussed above. In this embodiment the suction side of blade  18  is oriented in a similar manner, with a similar angle from a plane perpendicular to the axis of rotation of the propeller of this embodiment, as with lower surface (suction side)  28  of the previous embodiment, although instead of being located on the lower side of blade  18  suction side is located on the upper side of blade  18 . The suction side in this embodiment is angled downwardly from a plane perpendicular to the axis of rotation of the propeller of this embodiment. 
         [0052]    Similarly the positioning of the pressure side is reversed from that of the above embodiment. The pressure side of blade  18  is oriented in a similar manner, with a similar angle from a plane perpendicular to the axis of rotation of the propeller of this embodiment, as with upper surface (pressured side)  26  of the previous embodiment, although instead of being located on the upper side of blade  18  pressure side is located on the lower side of blade  18 . The pressure side in this embodiment is angled upwardly from a plane perpendicular to the axis of rotation of the propeller of this embodiment. 
         [0053]    This causes an axial flow of the liquid in which the propeller of this embodiment is submerged in a downward direct from the propeller, rather than the upward direction of the previous embodiment. 
         [0054]    As will be apparent to those skilled in the art to which the invention is addressed, the present invention may be embodied in forms other than those specifically disclosed above, without departing from the spirit or essential characteristics of the invention. The particular embodiments of the invention described above and the particular details of the processes described are therefore to be considered in all respects as illustrative or exemplary only and not restrictive. The scope of the present invention is as set forth in the complete disclosure rather than being limited to the examples set forth in the foregoing description.