Abstract:
An gas diffusion device for introducing gas into a large body of liquid having at least one diffuser blade that engages over a mounting tube having a spar affixed to its exterior. A passage in the diffuser blade is dimensioned to cooperatively engage over the spar and mounting tube which holds the diffuser blade top surface at a determined angle once so engaged thereover. Changing the position of the spar on the exterior of the mounting tube in relation to the center axis of the mounting tube changes the resulting angle of the diffuser blade top surface. The diffuser blade can be attached to a hub mounted on a mainshaft that automatically cantilevers out of the fluid should compressed gas supplied to the diffuser blade through the mainshaft cease to avoid damage to the diffuser blade and diffuser pad on the blade from particulate in the liquid.

Description:
FIELD OF THE INVENTION  
         [0001]    The disclosed device herein relates to the field of aeration and mixing of large bodies of fluid. More particularly, the present invention is an improved apparatus for the introduction of gas and dissolved gases into a large body of liquid and for concurrently providing the ability to mix the liquid in a large body of liquid.  
         BACKGROUND OF THE INVENTION  
         [0002]    Aeration and mixing have been used for treating water and other liquids for more than one hundred years. During that time various devices and methods have been employed for the mixing and aeration of such large bodies of fluid. Such aeration devices include compressor/diffusers, surface aerators, turbine/spargers, jet aerators, blade diffusers, with each having its own utility when it comes to the task at hand.  
           [0003]    Compressor/diffuser type aerators employ a compressor suitable to the task to force gas through a diffuser located below the liquid surface. As the bubbles naturally rise to the surface of the liquid being aerated, gas is imparted from the bubbles into the liquid. Resulting mixing of the liquid is provided by the hydraulic resistance of the bubbles as they travel to the liquid surface.  
           [0004]    Diffuser type aereators range from coarse bubble to fine bubble diffusers. Coarse bubble systems as the name implies employ larger bubbles and are more reliable but less energy-efficient to operate, when compared to fine bubble systems. Fine bubble diffusing systems, while at first more energy-efficient, frequently become fouled or clogged due to the small apertures required to produce the small bubbles clogging thereby resulting in decreased reliability. Such fine-bubble diffusers, in particular, are limited in low volume capability, due to increased fouling problems at lower gas flow rates.  
           [0005]    Compressor diffuser type devices employ a rotating gas diffuser in the form of a large flat horizontal disk-shaped component. Compressed gas is therein discharged from porous plates arranged completely around the circumference of the disk. This type of gas deployment into the liquid tends to produce gas flow where many of the bubbles tend naturally to follow in the path of preceding bubbles which limits the efficiency of the transfer of gas into the surrounding body of liquid. Such a bubble pattern also tends to interrupt the effective inflow of liquid into the reactor column and therefor further limits mixing efficiency. Such a device is shown in U.S. Pat. No. 3,630,498 (Belinski) which teaches the use of a small, high-speed rotating mixing and an aerating element comprising a pair of horizontal radially extending blades or foils. In operation of Belinski, a partial vacuum is formed in a zone of cavitation behind the foils. Gas bubbles which emerge from the blades enter this zone of cavitation and expand due to the reduced pressure around the bubbles. While expanded, the bubbles are shattered by hydraulic forces into smaller bubbles. These smaller bubbles then exit the reduced pressure zone of cavitation and are further reduced in size as they are subjected to ambient pressure. Critical to the Belinski patent is the creation of the zone of cavitation. To create this zone of cavitation in a practical device, the foils must be short (such as 24 inches) and rotated at very high speeds (such as 450 RPM). Consequently, such a device is best suited for a smaller area. If the foils are made appreciably longer, the energy cost and physical loads of high-speed rotation quickly become prohibitive.  
           [0006]    Surface aerators employ an engine or motor to rotate impellers or blades near the surface of the liquid body. Such devices conventionally either lift the water into the air above the surface, or aspirate air and inject it just below the surface of the liquid body. Surface aerators in general possess a poor gas transfer efficiency when compared to fine bubble diffused aeration systems since they consume more horsepower hours of energy for each pound of dissolved oxygen they produce. Mixing from surface aerators is generally limited to liquid at or near the surface of the body of fluid being aerated. Further, mixing energy tends to be point limited to positions at or near the impeller. Consequently, localized zones of high shearing forces tend to damage delicate floc structures necessary for proper liquid clarification. Further, surface aerators are generally limited in the length of the shaft overhang, and shaft bearing life tends to be problematic.  
           [0007]    Turbine/Spargers aerators use compressors to force and distribute gas below the surface of the liquid body. They also employ a submerged impeller positioned just above the diffuser(sparger), to shear the bubbles and provide bulk mixing of the liquid body in which they reside. Disadvantages of turbine spargers are similar to those for surface aerators with the additional disadvantage caused by the turbine sparger requiring an independent source of compressed gas such as a compressor.  
           [0008]    Jet Aerators employ a liquid pump and an eductor to impart gas into the liquid body surrounding them using the Venturi principle. Such a system is taught in U.S. Pat. No. 4,101,286 (Nagao). Such jet aeration systems may also be equipped to mix additional gas, liquid, or solid chemicals into the liquid body into which they are engaged. While such systems are generally reliable and have good low volume capability, they tend to be inefficient aerators.  
           [0009]    Blade diffusers as taught in U.S. Pat. No. 1,383,881 (Ingram) use a flotation apparatus having rotating blades which dispense gas bubbles into the surrounding body of liquid. The design of these blades is dictated, however, by the requirement that they also act as impellers to rotate the blades as well as discharging the gas bubbles. Such blades are pitched so that the leading edges are elevated about 45 degrees and as a result, the emerging gas is formed into elongated and then enlarged bubbles, which result in a less efficient introduction of the gas into the liquid. In addition, examination of the patent and our research indicates that the blades would rotate in the opposite direction than is indicated in the Ingram Patent. This would result from the upward flow of fluid caused by the fluid lift pump effect of the released gas moving upward toward the liquid surface. Such a vertical water flow across the pitched blades would appear to in fact cause rotation opposite that which is taught in Ingram.  
           [0010]    Another excellent example of a device for aeration and mixing of large bodies of liquid is taught in U.S. Pat. No. 5,681,509(Bailey). Bailey teaches an apparatus and method for mixing and introducing gas into a large body of liquid by rotating a plurality of permanently mounted spoke-like discharge members which are below the surface of the liquid body. These members have upwardly facing perforated discharge surfaces through which compressed gas is released up into the liquid. Upward lift is countered by angling the members which are tilted with their leading edges lower than their trailing edges and balancing the rotation speed to achieve substantially zero lift. A control system is provided to change the depth of submergence of the discharge members to regulate dissolved gas infusion rate and speed of member rotation to maintain angle of attack. Bailey, while a leader in this field, teaches the use of permanantly mounted blade members which are self supporting for the load forces encountered and which can prove labor intensive to change if needed. Bailey also teaches the use of a vertically inclining main shaft which, while providing valuable utility in the ability to raise the blade members from the liquid in which they rotate, does require a substantial frame and mechanical structure to support the components allowing for the inclining main shaft.  
           [0011]    As such, there exists a need for a device for mixing and for introducing gas into a large body of liquid which is easily servicable and energy efficient. Such a device should provide maximum aeration and mixing to the water to which it is immersed and also provide easy ingress and egress of the diffuser blades from the water or liquid being aerated. Such a device should best use diffuser blades that are adaptable for attachment and use with prior systems for aeration to improve on their performance as well as in new installations with frame components designed to further enhance the aeration, energy, and servicing characteristics the device offers. Such a system would best use diffuser blades which are light weight due to transference of loading to load bearing members thereby reducing costs of manufacture and aiding in ease of installation.  
         SUMMARY OF THE INVENTION  
         [0012]    The device as herein disclosed features an improved diffuser blade that provides excellent aeration characteristics as well as a highly improved mounting scheme to the rotating hub which provides both compressed gas and rotation to the diffuser blade. The improved mounting system of the diffuser blade enhances both installation of the diffuser blades during the initial installation as well as during removal and reinstallation for maintenance. The improved diffuser blade is mounted on the disclosed support and operating structure and yields maximum utility due to the combined characteristics of the tilting support structure and easily mountable diffuser blades. Or disclosed diffuser blades may also be used to improve currently installed rotational aeration devices if adapted for cooperative installed engagement with aeration systems already in existence to thereby enhance the performance and improve the serviceability of such existing systems.  
           [0013]    The disclosed device herein consists of two main components in the form of a support frame which floats upon the liquid and diffuser blades which rotate when immersed in the liquid to aerate the liquid. The frame is mounted upon a means for floatation or continued elevation above a liquid pool such as pontoons or on another means to elevate it above a liquid pool such as a bridge or pier, and provides a platform for a tilting main shaft, a connection to a compressed air source, and a means to rotate a tiltable vertical main shaft such as an electric motor. The frame component features a unique attachment to the main shaft in that the main shaft is rotationally engaged with the frame and can be tilted or cantilevered upward and out of the water or liquid to either mount or service the diffuser blades to the main shaft or during power failures or other times when the diffuser blades need to be raised from the liquid to protect them from clogging.  
           [0014]    The diffuser blades attached to the lower or distal end of the main shaft employ a rectangular spar which is cooperatively engaged about its outer surface in a similarly shaped passage formed internally on the diffuser blade. The blade engaging spar is attached in a fixed position about the exterior surface of a mounting tube which either mounts directly to the hub of the main shaft or the mounting tube overlaps a nipple protruding from the hub which is attached to the main shaft. Once engaged for rotation by the main shaft, the mounting tube and spar project substantially normal from the center axis of the main shaft. A pair of cooperatively engageable mounting collars with one affixed on the mounting tube and the other upon the mounting end of the diffuser blade, allow for attachment of the diffuser blade with the mounting tube with the spar engaged with both the exterior of the mounting tube and internally on the diffuser blade. The spar being engaged in a cooperatively engaging passage in the diffuser blade, provides structural support to the diffuser blade during rotation through the fluid and provides support to the diffuser blade in maintaining the angle of attack during rotation in the liquid.  
           [0015]    This novel interlocking of the spar with the mounting tube and using a co-operatively engaging passage axially located in the diffuser blade, to engage the diffuser blade upon the spar, allows for easy mounting and dismounting of the diffuser blade to the mounting tube and spar, for both installation and for maintenance or replacement. Further, the provision of the metal spar, which cooperatively engages internally with a passage in the diffuser blade, provides reinforcement to the diffuser blade against the plurality of vector forces imparted upon the diffuser blade when rotating at the determined best angle of attack through the fluid in which it is immersed. This spar and diffuser blade engagement transfers a substantial portion of the vector forces imparted to the diffuser blade including the twisting force and the lateral force imparted to the diffuser blade at the angle of attack during rotation of the main shaft in operative communication with the mounting tube and the nipple. This transfer of force using the spar engaged in the cooperative passage thus allows the diffuser blade itself, and its mounting collar, to be made from much lighter material than if the diffuser blade was required to support the twisting and lateral forces generated by rotating at an angle in the fluid. Further, the current preferred spar engaging the cooperative passage in the diffuser blade has a generally “u” shape about it and provides an excellent path for disbursement of compressed gas communicated through the center of the mounting tube up and through the face of the diffuser blade.  
           [0016]    The attachment of the diffuser blade engaged over the rectangular shaped spar on the mounting tube, using the mating mounting collars to primarily maintain the diffuser blade upon the spar, also allows for the diffuser blade to be operatively positioned at a determined angle of attack when circulating through the fluid. The desired angle of attack may be achieved using one or a plurality of provided means for rotational engagement of the diffuser blade to the hub. This angle of attack is determined by either first positioning of the spar on the mounting tube in a fixed attachment such that it is at the proper angle to maintain the diffuser blade at the desired angle of attack when inserted thereover, or by taking a mounting tube with an affixed spar thereon, and cooperatively engaging it with the hub with the spar at the correct point to yield the proper angle to an attached diffuser blade. Either means to fix the spar at the proper angle extending from the hub could be used and yield a diffuser blade engaged over the spar with the diffuser blade at the desired angle of attack with the spar absorbing most of the force imparted to the diffuser blade from circulating angled in the fluid.  
           [0017]    In order to maximize the shearing effect of the flow of liquid relative to the rotating diffuser blades, it is desirable that the resultant angle of attack of the discharge surfaces of the diffuser blades, with regard to the relative liquid flow, be essentially zero or somewhat greater. In other words, such flow should be generally parallel to or tangential to such surfaces. To achieve this zero angle of attack the illustrated device is designed to take into account the effect of the upward discharge of gas from the diffuser blades. This discharge of gas causes an upward flow of the liquid in a cylindrical or reactor column that is an upward extension of the circle defined by the area between the center axis of the main shaft to the tips of the rotating diffuser blades. Specifically, such discharge of gas produces a zone of liquid above the diffuser blades, which due to the presence of gas bubbles in that liquid, is less dense than the ambient liquid below the diffuser blades. This less dense liquid is displaced vertically upwardly from below by ambient density liquid. The vertical upward flow of the less dense liquid is called the lift pump effect. The ambient liquid that displaces the rising less dense liquid enters the reactor column between the rotating blades. This upward flow of ambient liquid affects the angle of attack between the rotating blades and the ambient liquid.  
           [0018]    To achieve the desired zero angle of attack, in view of the aforementioned lift pump effect, the diffuser blades in the current best mode of the device, cooperatively engage through a formed internal passage, with the exterior of the rectangular spar which itself is in registered permanent engagement using welding or attachment components to fix it on the exterior of the mounting tube. Mating mounting attachment collars attached at the proper position to the exterior of the mounting tube and formed at the attachment end of the diffuser blades, hold the diffuser blade from sliding off the supporting spar during rotation in the fluid. The engagement of the internal passage of the diffuser blade over the rectangular spare, which has been properly positioned by affixing it at the correct position on the tube, or by rotating the mounting tube to place the spar in the correct position and then attaching it to the hub, maintains the diffuser blades fixed in a tilted or pitched position with the leading edges of the diffuser blades lowered to a determined angle to yield the zero angle of attack based on a number of factors noted below. The spar as noted must either be attached to the mounting tube at an angle, or rotated with the mounting tube which is then attached to the hub when the spar is properly positioned, such that, when the spar engages with the passage on the interior of the diffuser blade, the zero angle of attack is achieved.  
           [0019]    The provision of the easily mounted and dismounted light weight diffuser blade over the spar, and engaged at a determined fixed angle thereon, provides the ability of the diffuser blades to be installed to yield an infinite number of different angles of attack when attached to the mounting tube and adjusted as needed. This angle adjustment is achieved simply by attaching the spar to the mounting tube, by welding or bolting or other means to hold the spar engaged with the mounting tube at the proper determined angle, in such a manner as to yield the desired angle of attack of the diffuser blade when it is cooperatively engaged over the spar. Or as noted, the spar can be affixed to the mounting tube, and then the mounting tube can be attached to the hub with the spar at correct position using a means for engagement of the hub to the mounting tube that will allow for adjustment of the position of the spar before it is fixed to the hub. Changing the angle of engagement of the rectangular spar by either rotating the mounting tube and affixing it to the hub, or by using a mounting tube with the spar positioned properly for a non rotational attachment to the hub, results in a changed angle of attack of the engaged diffuser blade. Of course, in addition to using a means to rotate the mounting tube and then engage it with the hub, the mounting tubes can also be manufactured with the spars attached at different angles to thereby yield the proper angle of attack of the attached diffuser blades. This makes changing the angle of attack of the diffuser blades to the indented purpose easily accomplished by simply changing the mounting tube to one which has the spar attached at the proper angle to engage the diffuser tube and yield the desired angle of attack.  
           [0020]    Thus the diffuser blades may be easily manufactured of lightweight material with a properly dimensioned spar engaging passage and attachment collar and be used in a wide variety of liquids and at varying speeds and still yield the proper angle of attack simply by properly attaching the mounting tube to its engagement with the hub to yield the properly angled or positioned spar attached to its exterior. Adjustment of position of the spar to the proper point to engage the diffuser tube interior and hold the diffuser tube at the proper angle of attack is aided by the provision of a hub flange which attaches using fasteners to a mating flange affixed to the mounting tube. The hub flange is provided with a plurality of different hole combinations in the flange which will align with the holes formed in the mating flange to allow the mounting tube, and attached spar to be rotated into the proper position and held in that position by bolts or other fasteners affixed through the properly aligned holes in the hub flange and mating flange. By placing a plurality or large number of different holes in the hub flange, which when aligned with the mating flange will position the spar at varying positions about the center axis running from the hub through the mounting tube, great adjustability for the resulting angle of attack of the diffuser blade is achieved as well as providing substantial structural support to the diffuser blade from the properly positioned spar. Alternatively, these mounting tubes with attached spars could be manufactured in kits with each kit having spars positioned at different angles around the center axis of the mounting tube when attached to the hub directly. While this would eliminate the need for the plurality of different hole mating combinations between the hub flange and mating flange, and is anticipated by this patent, the preferred embodiment employs the hub flange with multiple alignable holes mating to the mating flange because of its adjustability which is especially important during installation and maintenance.  
           [0021]    An object of this invention is the provision of an easily mounted and dismounted diffuser blade for rotation in a fluid to both mix the fluid and discharge gas into the fluid from the diffuser blade.  
           [0022]    An additional object of this invention is the provision of such a diffuser blade that is light weight due to the provision of an internally engageable spar which reinforces the diffuser blade against rotational and lateral force generated when moving through a liquid.  
           [0023]    Another object of this invention is the provision of a diffuser blade that is easily slid upon and engaged over a cooperatively engaging spar which will then maintain the angle of attack of the diffuser blade when rotating in the fluid.  
           [0024]    A further object of this invention is to provide a diffuser blade that may be easily changed by slidably engaging the diffuser blade to and from its internal spar engagement.  
           [0025]    Yet another object of this invention is the provision of a frame having a main shaft for rotating the diffuser blade in a fluid which may be cantilevered out of the fluid for maintenance or replacement of the diffuser blades.  
           [0026]    A further object of this invention is to provide a fail safe system of fluid aeration wherein the diffuser blades aerating the fluid will cantilever out of the fluid should power to the air blower cease, thereby preventing clogging of the diffuser blades.  
           [0027]    Yet another object of this invention is to provide a diffuser blade that is slidably mountable to a mounting tube and secured at the proper angle of attack for rotation and being able to change the angle of attack of the diffuser blade by simply changing or rotating the mounting tube in its affixation to the hub to yield a differently angled spar.  
           [0028]    These together with other objects and advantages which will become subsequently apparent reside in the details of the construction and operation as more fully hereinafter described and claimed, reference being made to the accompanying drawings forming a part thereof, wherein like numerals refer to like parts throughout.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]    The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of this invention.  
         [0030]    [0030]FIG. 1 depicts a view of the aeration system herein disclosed showing improved diffuser blade affixed to a support shaft on a support frame with the diffuser blade in a submerged position.  
         [0031]    [0031]FIG. 2 depicts a view of the aeration system herein disclosed showing the diffuser blade affixed to the support shaft in a raised position.  
         [0032]    [0032]FIG. 3 depicts a top view of the diffuser blade engaged with the mounting tube.  
         [0033]    [0033]FIG. 4 depicts a side cut away view of the diffuser blade showing the elongated spar engaged with both the mounting tube and the interior of the diffuser blade.  
         [0034]    [0034]FIG. 5 shows an exploded view of the diffuser blade from the spar engaged upon the mounting tube.  
         [0035]    [0035]FIG. 5 a  depicts the hub and the engagement of the mounting tubes to the hub using angle adjusting hub flanges.  
         [0036]    [0036]FIG. 6 is a side cut away view along line  6 - 6  of FIG. 3 depicting the internal engagement of the spar and mounting tube.  
         [0037]    [0037]FIG. 7 depicts the hub flanges which provide a plurality of mounting holes aligned to vary the angle of an attached mounting tube.  
         [0038]    [0038]FIG. 8 depicts a vector analysis of the proper angle of attack of the diffuser blade when moving through the fluid. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]    Referring now to the drawings, wherein similar parts of the invention are identified by like reference numerals, there is seen in FIGS. 1-8 the various components of the disclosed device  10  that combine to yield an improved apparatus for both mixing and introducing gas into a large body of liquid such as a lake, reservoir, or sewage pond where proper aeration is a constant concern. As noted above the disclosed device  10  consists of two components including the spar supported diffuser blade  12  which rotates submersed in the liquid  14  and the support frame  16  which serves as a floating or elevated mount for the diffuser blade  12  above the liquid  14 . As described above the improved diffuser blade  12  and its unique spar engaging and supporting mounting system can be used to improve the performance and ease the maintenance of older gas mixing systems by adapting it for attachment to such systems using the unique spar  42  affixed to the mounting tubes  40  which would be adapted for attachment to existing devices and as such it could thus be used by itself without the support frame  16 . However, when combined with the unique support frame  16  and with the components and cantilever ability of the disclosed support frame  16 , the diffuser blade  12  and support frame  16  combine to yield exceptional function and utility in aeration, maintenance, and safety.  
         [0040]    The support frame  16  is best depicted in FIGS. 1 and 2, is designed to provide supported above, or float upon, the liquid  14  pool and thereby provide the platform for the various described components herein to rotate the diffuser blades  12  submerged in the liquid  14 . The support frame  16  is adapted to maintain a position above or float upon the surface of the liquid  14  which in the depicted embodiment uses a means to maintain the frame in position over a liquid pool such as pontoons  18  which are attached to a base  20 . The pontoons  18  or other flotation means would have sufficient flotation ability to carry all of the weight of the various components mounted on the support frame  16 . Of course those skilled in the art will realize that a pier or bridge or cable support system or other means to maintain the frame in position elevated above the liquid  14  could be used, and such are anticipated.  
         [0041]    A main shaft  22  is rotationally attached to the support frame  16  using a means for rotational engagement of the main shaft  22  with the support frame  16  which in the current embodiment is accomplished by hinge  24  which engages a collar  26  surrounding the upper portion of the main shaft  22  which is rotationally engaged therein. Consequently, rotating the collar  26  from a position perpendicular to the surface of the liquid  14  to a position substantially parallel to the surface of the liquid  14  will thus cantilever the main shaft  22  from a submerged position shown in FIG. 1 to an elevated position shown in FIG. 2. In the elevated position the main shaft  22  will still rotate to thereby ease the installation and maintenance process when attaching the diffuser blades  12  to their sealed engagement with the main shaft  22 .  
         [0042]    In a current preferred mode of the device  10  the rotation of the main shaft  22  between the elevated position and the submerged position is achieved by a cable  28  engaged with a winch  30  which is user activateable. To rotate the main shaft  22  to the submerged position, the winch is energized and the cable  28  is wound on the winch  30  and the main shaft  22 , which is rotationally engaged inside the collar  26 , is pulled into the liquid  14  when the collar  26  descends, thus submerging the diffuser blades  12  which are affixed to the distal end of the main shaft  22  into the liquid  14 .  
         [0043]    Also in a preferred mode of the device  10  the main shaft  22  is counter balanced using weights or components of the device  10  itself such as pump  32  or other means render the main shaft  22  substantially top heavy at the end above the frame  20 . This counter balance is best if it has sufficient weight to generate sufficient force whereby the main shaft  22  will default to and rotate to the elevated position unless pulled and held in the submerged position. Consequently, in the submerged position in the liquid  14 , the main shaft  22  with the diffuser blades  12  attached, will only remain submerged so long as a means to rotate and hold the mainshaft in the submerged position is engaged such as the cable  28  or a similar tether means is wound on the winch  30  and locked in position around the winch  30 , or if the cable is wound upon the winch and another locking means is engaged to hold the mainshaft  22  in the submerged position. As such, in a current preferred mode of the device  10 , the main shaft  22  with one or a plurality of diffuser blades  12  attached, will always default to the elevated position, unless held submerged by a means to rotate and hold the main shaft  22  in the submerged position with the main shaft  22  is substantially perpendicular to the base  20 . Defaulting to the elevated position insures that the diffuser blades  12  are always removed from the fluid  14  when the compressed air source communicating compressed air through the diffuser blades  12  and through the diffuser material  53  into the surrounding liquid  15  ceases. This prevents particulate in the fluid from clogging the diffuser material  53  mounted over the apertures  52  in the top of the diffuser blades  14  when compressed air is not available and being communicated through the apertures  52  and the diffuser material  53 .  
         [0044]    Currently the preferred means to maintain the main shaft  22  in the submerged position is an electro magnet  34  which contacts the collar  26  or a mating plate thereon, and holds the main shaft  22  perpendicular to the base  20  only as long as electrical power is provided to that electro magnet  34 . It would be best if the electro magnet  34  and the pump  32  are both energized by the same electrical force. If for some reason the electrical power fails to the pump  32 , which because of the potential for particulate clogging the diffuser blade  12  is hazardous the diffuser blade  12 , the magnet  34  will cease to function concurrently or just before the positive pressure from the pump  32  ceases and the main shaft  22  and diffuser blade  12  will rotate to the default elevated position with both elevated out of the liquid  14 . Of course those skilled in the art will realize that other means to maintain the main shaft  22  in the submerged position such as a solenoid, electrical locking mechanism for the cable  28  or winch  30 , or other devices might be used and consequently such are anticipated in the scope of this patent.  
         [0045]    The main shaft  22  is an elongated tube having axial passage defining a conduit running axially therethrough which communicates in a sealed engagement at the top end with a pressurized air source such as compressor or pump  32 . As shown in FIG. 1 the pump  32  if mounted at the top end of the main shaft  22  also provides some or all of the counter weight to rotate the main shaft  22  to the default elevated position should electrical power fail thereby disengaging the electro magnet  34  or any other means to maintain the main shaft  22  in the submerged position. However weights could also be used alone or in combination with the pump  32  to yield the proper force as a counter weight. Also weights alone might be used as the counter weight and a hose (not shown) might be attached between a remote compressed air source and the main shaft  22  to thereby provide a compressed air source into the conduit running axially through the main shaft  22  for communication of compressed air to the attached diffuser blades  12  at the distal end of the main shaft.  
         [0046]    Rotation of the main shaft  22  which in turn rotates the diffuser blade  12  at the distal or lower end of the main shaft  22  is provided by a means to rotate the main shaft  22  which as depicted is provided by a motor  34  engaged with the upper end of the main shaft  22  using a gearbox  36  or similar means for engagement of the motor  34  to rotate the main shaft  22 . In cases of an electrical motor a motor controller would be used to control the rotation speed imparted to the main shaft  22  by the motor  34  to achieve the proper speed of the diffuser blades  12  in the liquid  14  at the chosen angle of attack of the diffuser blade  12 . If course other types of motors might be used such as compressed air, hydraulic, or internal combustion motors with the appropriate rotation speed control means and such are anticipated.  
         [0047]    At the lower end of the main shaft  22  a hub  38  is located which has a plurality of mounting tubes  40  attached to the hub  38  using a hub flange  41  which would bolt or otherwise be attached to the hub  38 . The hub flange  41  provides an easy means to attach the mounting tube  40  to the hub  38  and the plurality of holes  58  in the hub flange  41  provides a means to rotate the mounting tube  40  to position the spar  42  at the proper point around the center axis of the mounting tube  40  to engage the diffuser blade  12  and hold it in place at the proper angle of attack. Or should additional support be desired, the mounting tubes  40  may be attached to a sealed engagement with the hub  38  by sliding the passage  51  extending axially inside the mounting tubes  40  over a plurality of appropriately diametered supporting nipples  39  projecting substantially perpendicular to the center axis of the main shaft  22 . This would be the case where longer diffuser blades  12  are used and once slid upon the nipples  39 , the hub flange  41  would be attached to the hub  38  and the position of the spar  42  around the center axis of the mounting tube  40  would be adjusted to the proper position wherein the hub flange  41  would be fixedly secured to the hub  38  thereby securing the mounting tubes  40  to a sealed engagement with the hub  38 . Nipples  39  are used when more support for the mounting tubes  40  is needed as in cases where longer diffuser blades  12  or diffuser blades  12  with longer mounting tubes  40  are employed. However, where shorter diffuser blades  12  or mounting tubes  40  are used and extra support from the nipples  39  is not required, the mounting tubes  40  could also be directly attached to the hub  38  by attaching the hub flange  41  to the hub  38  without the nipples  39 .  
         [0048]    Each mounting tube  40  has an axial passageway  51  in sealed communication with the compressed air supply from the conduit formed internally and running axially through the main shaft  22  through the hub  38  and through a flange aperture  56  communicating through the hub  38  or from the hub  38  through the distal end of the nipple  39  if used. Pressurized air or gas is thus communicated from the pump  32  through the mainshaft  22  through the hub  38  and to the axial passage  51  extending axially through the mounting tubes  40 . If the nipples  39  are employed, the pressurized air communicates from the hub  38  through nipple  39  which communicates through the flange and to the axial passage  51  of the mounting tubes  40 . In this manner, compressed air is communicated from the pressurized air source communicating with the conduit formed in the main shaft  22  at the top end of the main shaft  22  to the distal ends of each mounting tube  40  and into the diffuser blades  12  which are in sealed engagement to the mounting tubes  40 .  
         [0049]    Attached to the exterior of the mounting tube  40  is an elongated spar  42  which in the current best mode provides the necessary structural support to the diffuser blade  12  when frictionally engaged at the angle determined by the position of the spar  24  in relation to the center axis of the mounting tube  40 . The structural support of the spar  42  is sufficient to maintain the diffuser blade  12  structurally when exposed to the various force vectors generated from the liquid  14  being forced against the rotating diffuser blade  12  at the desired angle of attack.  
         [0050]    In the current best mode of the device  10  the spar  42  is generally a “U” shape and as shown in FIG. 6 and fixedly engaged by welding or other means for fixed engagement, over the exterior circumference of the projecting mounting tube  40  on one end and within a cooperating engagement passage  43  axially formed in the interior of the diffuser blade  12  on the other end, to provide support to the diffuser blade  12  from both the lateral forces imparted upon it from rotating in the fluid as well as the twisting forces imparted upon the diffuser blade  12  from rotating at the determined angle of attack. Using the slide-on engagement of the diffuser blade  12  over the spar  42  which is properly mounted on the mounting tube  40  which is properly attached to the hub  38  using the appropriate holes  58  to yield the proper angle of attack to the diffuser blade  12 , greatly reduces the time and cost of replacing or repairing clogged or otherwise impaired diffuser blades  12  and the cost of the blades themselves since they can be molded from lightweight material such as plastic which will be sufficient to hold up to the forces imparted when moving through the fluid  14  with added strength provided by the cooperatively engaged spar  42 . This slidable engagement of the spar  42  inside the engagement passage  43  axially formed in the diffuser blade  12  and at the proper angle of attack upon the mounting tubes  40  also allows the mounting tubes  40  to be pre attached to the hub  38  using the hub flange  41  or by having the mounting tubes  40  overlap the nipples  39  and attach using the mating hub flange  41 . Once the mounting tubes  40  are so mounted, with the spar  42  appropriately rotated to the proper position to yield the proper angle of attack of the diffuser blades  12 , they provide an easy slid-on target for the unwieldy elongated diffuser blades  12  over the cooperatively engaging spar  42  during mounting and dismounting which saves time on initial installation and over the life of the device  10 .  
         [0051]    Further, by using the spar  42  to carry and transfer to the mounting tube  40  the majority of the force imparted to the diffuser blade  12  it is easy to change the total length of the diffuser blade  12  to a longer or shorter total length to match the desired mixing and aeration for the job intended. A longer diffuser blade  12  is carried on a longer spar  42  which optionally slides over a nipple  39  for extra support, whereas a shorter one would be supported on a shorter spar  42  and mounting tube  40  which would attach directly to the hub  38 . As long as the mounting tubes  40  and nipples  39  if used, are sized to support the force of the longest spar  42  and diffuser blade  12  that is used, any size diffuser blade  12  below the longest is easily substituted.  
         [0052]    As noted above, the spar  42  is shaped about its circumference to engage with an engagement passage  43  axially formed inside the diffuser blade  12 . Consequently the angle of attack of the diffuser blade  12  through the liquid is easily achieved and permanantly maintained by using a mounting tube  40  which has the spar  42  attached in the proper position to yield the desired angle of attack of the diffuser blade  12  through the liquid  14  when the mounting tube  40  is attached to the hub  38 . The mounting tubes  40  with a flange  41  affixed to them, are attached to a sealed engagement with the hub  38  by engaging the hub flange  41  using bolts or similar fasteners which are locked in engagement with the hub  38 . As can be seen, the hub flange  41  has a plurality of holes  58  which are positioned to line up with appropriately positioned holes in the hub  38  and position the spar  42  at different positions depending on the amount of rotation of the mounting tube  40  and the holes in the hub  38 . As can be seen in FIG. 7, a large number of holes  58  can be placed in the hub flange  41  at both its ends to allow for a large number of different angles which the mounting tube  40  may be rotated to thereby rotate the position of the spar  42  about the center axis of the mounting tube  40  and thereby rotate and maintain the position of the diffuser blade  12  engaged over the spar  42 . Should a different angle of attack be required, the attachment of the mounting tube  40  to the hub  38  may be rotated one way or the other by aligning the appropriate holes in the hub flange  41  and holes in the hub  38  which line up with the holes  58  in the hub flange  41  at differing angles of rotation. Again, once rotated and attached to place the spar  42  in the proper position to hold the diffuser blade  12  in the desired proper angle of attack, that angle of attack is maintained by the spar  42  and diffuser blade  12  engagement until it is changed by re-mating the hub flange  41  to the hub  38 .  
         [0053]    The removable attachment of the diffuser blade  12  over the spar  42  and onto the mounting tube  40 , is maintained by a means of attachment of the diffuser blade to the mounting tube using mating mounting flanges. A first mounting flange  44  mounted about the circumference of the mounting tubes  40  adjacent to the spar  42  attaches to a second mounting flange  46  formed into or attached to the mounting end of the diffuser blade  12 . Apertures or slots in both these mounting collars would substantially align so that fasteners could be placed therethrough thereby providing a means of attachment of the mounting tube  40  to the mounting end of the diffuser blade  12 . Since the majority of the twisting and other forces imparted to the diffuser blade  12  rotating at the angle of attack in the liquid  14  are transmitted to the spar  42  inserted in the engagement passage  43 , the mounting flange  46  on the diffuser blade  12  is relieved of having to carry this major load and can be made of lighter material sufficient to withstand substantially the centrifugal force that might develop and pull the diffuser blade  12  off of its engagement with the spar  42 .  
         [0054]    The engagement of the mounting flanges  44  and  46  would also sealably engage the interior cavity  49  of the diffuser blade  12  with the axial passages  51  running the length of the mounting tubes  40  to thereby communicate the pressurized gas or air from the pressurized air source to the interior cavity  49 . From the interior cavity  49  the pressurized air can them be communicated through apertures  52  formed in the discharge surfaces  50  of the diffuser blades  12  and through the adjacent diffuser material  53  and into the fluid  14 .  
         [0055]    In order to maximize the shearing effect of the flow of liquid  14  relative to the rotating diffuser blades  12 , it is desirable that the resultant angle of attack of the top surface of the diffuser material  53  attached upon the upper or discharge surfaces  50  of the diffuser blades  12  with regard to the relative liquid flow, be essentially zero or somewhat greater. In other words, such fluid flow should be generally parallel to or tangential to the top surface of the diffuser material  53  located upon the discharge surfaces  50 . To achieve this zero angle of attack the disclosed device  10  is designed to take into account the effect of the upward discharge of gas from the diffuser blades  12 . This discharge of gas causes an upward flow of the liquid in a cylindrical or reactor column that is an upward extension of the circle defined by the area between the center axis of the main shaft  22  to the tips of the rotating diffuser blades. Specifically, such discharge of gas produces a zone of liquid above the diffuser blades  12 , which due to the presence of gas bubbles in that liquid, is less dense than the ambient liquid below the diffuser blades. This less dense liquid is displaced vertically upwardly from below by ambient density liquid. The vertical upward flow of the less dense liquid is called the lift pump effect. The ambient liquid that displaces the rising less dense liquid enters the reactor column between the rotating blades  12 . This upward flow of ambient liquid affects the angle of attack between the rotating blades and the ambient liquid.  
         [0056]    To achieve the desired zero angle of attack, in view of the aforementioned lift pump effect, as noted earlier, the diffuser blades  12  in the current best mode of the device are mounted over the spar  42  which has been rotated to the proper position and secured to the hub  38  by the aforementioned attachment of the hub flange  41  using the appropriate holes  58  respectively to achieve a position of the spar  42  which will yield the zero angle of attack for the diffuser blade  12  when it is engaged over the spar  42 .  
         [0057]    [0057]FIG. 8 illustrates the plane of the discharge surface  50  of the rotating diffuser blade  12  relative to the resultant vector  61  of the liquid  14 . The resultant vector  61  is the vectorsum of (I) the horizontal vector  63  produced by the diffuser blade&#39;s rotating forward motion, and (ii) the vertical vector  66  produced by the liquid column&#39;s upward motion. When the angle of the discharge surface  50  essentially coincides with the angle of the resultant vector  61 , the desirable angle of attack of approximately zero is achieved. It may be seen from this relationship that, for a given tilt or angle of incidence of the member surface, the desired zero angle of attack can be maintained over a range of lift pump effect vertical liquid flow rates by selectively varying the speed of rotation of the members. Using the above vector analysis the relationship between the vector  63  in the horizontal plane determined by speed of rotation of the blade, the vector  66  determined by the vertical speed of the rising liquid, the angle of incidence of the blade discharge surface  50 , and the vector sum of the vectors  63  and  66  as represented by resultant vector  61 . The angle at which the rotating inclined diffuser surface  50  is impacted by the liquid is the angle of attack and is shown as the angle between resultant vector  61  and surface  50 . This angle is maintained through the life of the blade member  12  by the engagement of the properly positioned spar  42  with the engagement passage  43  of the blade member  12 .  
         [0058]    Compressed gas communicated to the interior cavity  49  of the diffuser blades  12  from the conduit running through the main shaft  22  is as noted communicated to the interior of the diffuser blades  12  through the generally “U” shaped spar  42  which has an open side edge along substantially its entire length to thereby aid in the dispersion of compressed air into the entire length of the interior cavity  49  of the diffuser blade  12 . Once pressurized the interior cavity  49  communicates the pressurized air through the discharge material  53  from the plurality of apertures  52  spaced and positioned to achieve the proper disbursement of gas into the liquid  14  at the determined angle of attack and speed of the diffuser blade  12 . Between the apertures  52  and the liquid  14  a diffuser material  53  is attached to the discharge surface  50  of the diffuser blade  12  provide the proper discharge of compressed air into the liquid  14 . The diffuser material  53  provides proper defusing of the air into the liquid.  
         [0059]    The device herein shown in the drawings and described in detail herein disclose arrangements of elements of particular construction and configuration for illustrating preferred embodiments of structure and method of operation of the present invention. It is to be understood, however, that elements of different construction and configuration and other arrangements thereof, other than those illustrated and described, may be employed in accordance with the spirit of this invention. All such changes, alterations and modifications as would occur to those skilled in the art are considered to be within the scope of this invention as broadly defined in the appended claims.  
         [0060]    As such, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modifications, various changes and substitutions are intended in the foregoing disclosure, and will be appreciated that in some instance some features of the invention will be employed without a corresponding use of other features without departing from the scope of the invention as set forth in the following claims.