Abstract:
Disclosed is an improved vacuum cleaning apparatus utilizing a self-sustained vortex flow in a centrifugal separator. More specifically, vortex flow is maintained via pressure differentials allowing the ejection of dust and other particles without bags, filters, or liquid baths. Furthermore, the impeller inside of the separator serves the dual purpose of moving fluid through the system as well as creating a cylindrical vortex fluid flow. Additional circulating blades present throughout the separation chamber prevent fluid flow from slowing due to frictional losses. The axial design of the present invention allows the centrifugal separator to be constructed with an arbitrary length. The present invention excels in producing clean fluid of a better quality more efficiently, more quietly, and more simply than devices known in the art.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS  
       [0001]    This application is filed as a continuation-in-part of co-pending application Ser. No. 10/025,376 entitled “Toroidal Vortex Vacuum Cleaner Centrifugal Dust Separator,” filed Dec. 19, 2001, which is a continuation-in-part of co-pending application Ser. No. 09/835,084 entitled “Toroidal Vortex Bagless Vacuum Cleaner,” filed Apr. 13, 2001, which is a continuation-in-part of co-pending application Ser. No. 09/829,416 entitled “Toroidal and Compound Vortex Attractor,” filed Apr. 9, 2001, which is a continuation-in-part of co-pending application Ser. No. 09/728,602, filed Dec. 1, 2000, entitled “Lifting Platform,” which is a continuation-in-part of co-pending Ser. No. 09/316,318, filed May 21, 1999, entitled “Vortex Attractor.” 
     
    
     
       TECHNICAL FIELD OF THE INVENTION  
         [0002]    The present invention relates to an improved centrifugal dust separator. Specifically, the improved dust separator centrifugally separates dust by ejecting particles into a collector attached to the side of a separation chamber. The high pressure within the collector maintains the cylindrical fluid flow within the separator. Circulating blades are implemented to compensate for energy losses due to friction. The fluid inlet is at the opposite side of the fluid outlet to adapt the separator for general use.  
         BACKGROUND OF THE INVENTION  
         [0003]    Centrifugal separation is a well known technique in the art of separation, including separation of solids from liquids, liquids from gases, and liquids from liquids. Although the present invention is unique and novel, in order to fully understand it in its proper context, the following references are provided.  
           [0004]    Specifically, the references of Dyson, U.S. Pat. No. 4,593,429, Kasper et al., U.S. Pat. No. 5,030,257, Moredock, U.S. Pat. No. 5,766,315, Tuvin et al., U.S. Pat. No. 6,168,641, and Song et al., U.S. Pat. No. 6,195,835, are relevant to the present invention.  
           [0005]    Dyson, U.S. Pat. No. 4,593,429, discloses a vacuum cleaning appliance utilizing a series of connected cyclones. The appliance utilizes a low-efficiency cyclone in series with a high-efficiency cyclone. This is done in order to effectively collect both large and small particles, respectively. Dyson teaches the incorporation of a low-efficiency cyclone to handle larger particles. Small particles continue to be handled by the high-efficiency cyclone. While both Dyson and the present invention utilize a bagless configuration, they utilize completely different flow technology. Unlike Dyson, the flow geometry of the present invention allows separation of both large and small particles by a single separation process.  
           [0006]    Kasper et al., U.S. Pat. No. 5,030,257, makes use of a vortex contained in a vertically aligned cylinder comprising multiple slots running the length of the side of the cylinder. A vortex fluid flow is generated within the cylinder, thereby ejecting air, dirt, and other unwanted debris outward through the slots. The ejected air and debris then come into contact with the surface of a liquid bath. The liquid then captures the debris and the clean air is free to return to the inside of the cylinder.  
           [0007]    Kasper et al. requires a liquid bath, and this is a major difference between Kasper et al. and the present invention. Liquid baths add both weight and complexity to the vacuum cleaner system. Furthermore, the liquid must be periodically changed to prevent corrosion, etc. Another feature of Kasper et al. is the mixing of circulating air ejected from the cyclone with non-circulating incoming air. To maximize efficiency and simplicity, a separator preferably requires no liquid bath and does not mix circulating and non-circulating air.  
           [0008]    Accordingly, the present invention is designed for maximal efficiency and simplicity. First, the present invention does not utilize a liquid bath or a liquid-air surface to separate debris from fluid; in fact, one feature of the present invention is its ability to separate matter from liquids as well as gases. Kasper et al.&#39;s device does not achieve such results given the necessity of the liquid-air surface for collecting particles. Second, the present invention uses a solid surface to maintain cylindrical flow in conjunction with high pressure in the dust collector. No such pressure is provided in Kasper et al.&#39;s patent; air is free to be ejected out the slots and return into the cylinder from beneath. Moreover, the present invention avoids mixing non-rotating incoming fluid with already circulating air by ensuring that all incoming air is traveling in a circular path.  
           [0009]    Moredock, U.S. Pat. No. 5,766,315, discloses a centrifugal separator that ejects particles radially. In order to create a cyclone, Moredock directs the air entering the cyclone chamber tangentially with the chamber&#39;s wall. Therefore, the chamber&#39;s wall forces the air into the cyclone flow pattern. Additionally, the speed of airflow in the cyclone is that of the incoming flow. Further, Moredock ejects particles from the dome via a slot running vertically along the wall. The slot leads into a duct traveling away from the apparatus. Thus, the duct allows air to exit along with the particles.  
           [0010]    The aforementioned aspects of Moredock are not found in the present invention. For instance, the present invention utilizes an impeller or centrifugal pump to create the cylindrical flow and the necessary suction in a single step. This has energy and efficiency advantages over Moredock&#39;s configuration. Further, incoming fluid is spun at the blade speed of the impeller, and consequently, can achieve a higher rate of rotation than that which is possible with Moredock&#39;s configuration. Also, the present invention uses back-pressure from the dust collector to maintain a cylindrical vortex. Moredock, on the other hand, expels air from the system. However, the present invention keeps the dust-laden air within the system to prevent dust from escaping into the atmosphere; fluid does not exit until it has been sufficiently cleaned. Therefore, the present invention advances over Moredock.  
           [0011]    Tuvin et al., U.S. Pat. No. 6,168,641, also makes use of a cyclone separation system. Tuvin et al.&#39;s patent includes a cyclone separator that ejects particles outward from a cyclone. As in Moredock, Tuvin et al. creates the cylindrical flow by allowing air to enter the dome tangentially with respect to the wall. Further, Tuvin et al. makes use of a filter as the final step before air exits the device. Also, Tuvin et al.&#39;s invention necessitates two separation steps, involving a course separator and a cyclone chamber. Therefore, the cyclone chamber separates fine particles while the course separator is employed for larger particles. However, the present invention is designed to provide a simpler design than Tuvin et al.  
           [0012]    First, the present invention provides both suction and the cylindrical vortex fluid flow with a single impeller. Thus, the separate suction means and directing means utilized in Tuvin et al. are unnecessary. Moreover, incoming fluid is spun at the blade speed of the impeller in the present invention. Such high rotational speed is not found in Tuvin et al. Also, filters are not used in the present invention because separation is sufficiently performed without them. Finally, the present invention separates all matter in a single separation chamber, unlike the two separation steps of Tuvin et al. Consequently, the present invention is simpler and more efficient than that which is disclosed in Tuvin et al.  
           [0013]    Song et al., U.S. Pat. No. 6,195,835, is directed to a vacuum cleaner having a cyclone dust collecting device for separating and collecting dust and dirt of a large particle size. The cyclone dust collecting device is biaxially placed against the extension pipe of the cleaner and includes a cyclone body having two tubes connected to the extension pipe and a dirt collecting tub connected to the cyclone body.  
           [0014]    Specifically, the dirt collecting tub of Song et al. is removable. The cyclone body has an air inlet and an air outlet. The dirt-containing air sucked via the suction opening enters via the air inlet in a slanting direction against the cyclone body, thereby producing a whirlpool air current inside of the cyclone body. The dirt is separated from the air centrifugally and is collected in the dirt collecting tub. A dirt separating grill having multiple holes is formed at the air outlet of the cyclone body to prevent the dust from flowing backward via the air outlet together with the air. Thus, the dirt sucked in by the device is primarily collected by the cyclone dust collecting device, thus extending the period of time before which the paper filter must be replaced. However, the present invention is configured to advance over Song et al.  
           [0015]    The device of Song et al. differs primarily from the present invention in that Song et al. utilizes a filter. The present invention utilizes such an efficient flow geometry that the need for a filter is eliminated.  
           [0016]    Thus, there is a clear need for a simple, light weight, efficient, quiet, and filterless centrifugal separator. The art is devoid of such a device, but the present invention meets these needs.  
         SUMMARY OF THE INVENTION  
         [0017]    The present invention relies upon technology from Applicant&#39;s prior invention disclosed in co-pending application Ser. No. 10/025,376 entitled “Toroidal Vortex Bagless Vacuum Cleaner Centrifugal Dust Separator,” filed Dec. 19, 2001, which is incorporated herein by reference. The separator of this application is based on technology disclosed in co-pending application Ser. No. 09/835,084 entitled “Toroidal Vortex Bagless Vacuum Cleaner,” filed Apr. 13, 2001, which is incorporated herein by reference. The bagless vacuum cleaner of this invention was developed from technology disclosed in the co-pending application Ser. No. 09/829,416 entitled “Toroidal and Compound Vortex Attractor,” filed Apr. 9, 2001, which is incorporated herein by reference. These attractors stem from technology disclosed in the co-pending application Ser. No. 09/728,602 entitled “Lifting Platform,” filed on Dec. 1, 2000, which is incorporated herein by reference. Finally, the lifting platform technology is based upon technology disclosed in co-pending application Ser. No. 09/316,318 entitled “Vortex Attractor,” filed May 21, 1999, which is incorporated herein by reference.  
           [0018]    As indicated above, the present invention was developed from the centrifugal separators of parent applications. Therein, cylindrical vortices are formed such that a circular pattern of flow exiting from the impeller spirals along the chamber&#39;s outer wall. The circular flow of the fluid acts as a centrifuge, forcing the higher mass dust particles outward. The spiraling fluid also creates a pressure in the dust collector greater than the pressure in the separation chamber due to the kinetic energy of the circulating fluid. This high pressure pushes the spiraling fluid inward, maintaining the fluid&#39;s circular path. However, the dust particles are not inhibited from traveling straight into the collector.  
           [0019]    Unlike other vacuum cleaners that employ centrifugal dust separation (e.g., the “cyclone” types discussed previously), the centrifugal separator disclosed herein spins the fluid around at the blade speed of the impeller. Thus, the system acts like a high speed centrifuge capable of removing very small particles from the fluid flow. No vacuum bag, liquid bath, or filter is required.  
           [0020]    One of the main features of the present centrifugal dust separator is the inherent low power consumption. The energy losses that occur when bags or filters are utilized are not present here. Specifically, bags and filters resist fluid flow, thus requiring greater power to maintain a given flowrate. Additionally, since only smooth changes in the direction of fluid flow are made in the present invention, the effect on the energy of the moving fluid is minimal. Hence, the present centrifugal separator contains provisions not already considered in the art. Furthermore, the design is expected to be virtually maintenance free.  
           [0021]    In the centrifugal separators, fluid flow is slowed by frictional losses when circulating along the separation chamber&#39;s walls. Consequently, Applicant&#39;s previous design has been modified to compensate for such frictional losses, thereby more completely cleaning incoming fluid. Particularly, the separator is modified with the addition of circulating blades that run the length of the separation chamber. Thus, fluid is spun by these blades for the entire duration that the fluid is in the separation chamber. The additional energy of the elongated circulating blades compensates for the frictional losses incurred as fluid flows against the separation chamber&#39;s walls. Finally, exiting fluid may be straightened with straightening vanes (i.e., the rotational component of the fluid is eliminated).  
           [0022]    Also, the possibility of excessive fluid flow into and out of the dust collector of the present invention can disrupt fluid flow. This is minimized, however, by strategically placing baffles inside the dust collector.  
           [0023]    Further, the present invention can be configured to achieve an arbitrarily high level of separation. To do so, the separation chamber is lengthened as far as is necessary to achieve a specific level of separation. Also, energy losses induced by fluid exchange via fluid passage into the collector can be minimized by narrowing the passage as it nears the outlet of the separation chamber (i.e., tapering the passage). Since particles in the separation chamber become finer as the fluid nears the outlet, appropriate tapering of the passage will not compromise separation. Valves may also be placed at the inlet or outlet of the separator in order to regulate fluid flow. By controlling fluid flow with valves, the efficiency of the separator can be maximized. Moreover, the separator of the present invention is modified such that overall fluid flow travels axially with respect to the rotation of the impeller vanes and circulating blades. Such an axial design allows the separator to be adaptable to a wider range of systems than conventional separators.  
           [0024]    An alternative embodiment of the present invention provides a recycle of fluid flow. Thus, fluid may be repeatedly cleaned to effect more complete separation. Implementation of a valve within the recycle tube may be used to control the amount of fluid that is recycled.  
           [0025]    Thus, it is an object of the present invention to utilize cylindrical vortices in a dust separator application.  
           [0026]    Additionally, it is an object of the present invention to provide an efficient dust separator.  
           [0027]    It is a further object of the present invention to provide a lightweight dust separator.  
           [0028]    In addition, it is an object of the present invention to provide a low-maintenance dust separator.  
           [0029]    It is yet another object of the present invention to provide a bagless dust separator.  
           [0030]    It is a further object of the present invention to provide a dust separator that does not require filters.  
           [0031]    It is also an object of the present invention to provide non-rotating, substantially dust-free fluid as a product.  
           [0032]    Moreover, it is an object of the present invention to provide a dust separator that compensates for frictional losses incurred from fluid flow encountering solid walls or a fluid passage into a dust collector.  
           [0033]    Furthermore, it is an object of the present invention to provide a dust separator that is easily modified (via elongation) in order to achieve an arbitrarily high level of dust separation.  
           [0034]    Also, it is an object of the present invention to provide a dust separator that minimizes exchange of fluid between the separation chamber and dust collector.  
           [0035]    Additionally, it is an object of the present invention to provide an axial flow design to adapt the dust separator for general use.  
           [0036]    Furthermore, it is an object of the present invention to recycle fluid flow to effect more complete separation.  
           [0037]    Moreover, it is an object of the present invention to smoothly guide fluid flow through a separation system.  
           [0038]    These and other objects will become readily apparent to one skilled in the art upon review of the following description, figures, and claims.  
         SUMMARY OF THE DRAWINGS  
         [0039]    A further understanding of the present invention can be obtained by reference to a preferred embodiment set forth in the illustrations of the accompanying drawings. Although the illustrated embodiment is merely exemplary of systems for carrying out the present invention, both the organization and method of operation of the invention, in general, together with further objectives and advantages thereof, may be more easily understood by reference to the drawings and the following description. The drawings are not intended to limit the scope of this invention, which is set forth with particularity in the claims as appended or as subsequently amended, but merely to clarify and exemplify the invention. 
       
    
    
       [0040]    For a more complete understanding of the present invention, reference is now made to the following drawings in which:  
         [0041]    [0041]FIGS. 1A and 1B (FIGS. 1A and 1B) depict a side plan view and cross-section thereof, respectively, of an exemplary centrifugal dust separator with a dust collector;  
         [0042]    [0042]FIGS. 2A and 2B (FIGS. 2A and 2B) depict a side plan view and cross sections thereof, respectively, of an exemplary centrifugal dust separator which compensates for frictional losses with circulating blades;  
         [0043]    [0043]FIG. 3A (FIG. 3A) depicts a centrifugal dust separator inlet which avoids the motor;  
         [0044]    [0044]FIG. 3B (FIG. 3B) depicts a centrifugal dust separator which contains its motor in the rotating drum;  
         [0045]    [0045]FIG. 4 (FIG. 4) depicts a centrifugal dust separator which is elongated to achieve a higher level of dust separation;  
         [0046]    [0046]FIG. 5 (FIG. 5) depicts modified circulating vanes and rotating drum designed to more smoothly guide fluid flow; and  
         [0047]    [0047]FIG. 6 (FIG. 6) depicts a centrifugal dust separator which recycles fluid flow. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0048]    As required, a detailed illustrative embodiment of the present invention is disclosed herein. However, techniques, systems and operating structures in accordance with the present invention may be embodied in a wide variety of forms and modes, some of which may be quite different from those in the disclosed embodiment. Consequently, the specific structural and functional details disclosed herein are merely representative, yet in that regard, they are deemed to afford the best embodiment for purposes of disclosure and to provide a basis for the claims herein which define the scope of the present invention. The following presents a detailed description of a preferred embodiment (as well as some alternative embodiments) of the present invention.  
         [0049]    Certain terminology will be used in the following description for convenience in reference only and will not be limiting. The words “in” and “out” will refer to directions toward and away from, respectively, the geometric center of the device and designated and/or reference parts thereof. The words “up” and “down” will indicate directions relative to the horizontal and as depicted in the various figures. Such terminology will include the words above specifically mentioned, derivatives thereof, and words of similar import.  
         [0050]    Applicant has disclosed in the parent patent application “Toroidal Vortex Vacuum Cleaner Centrifugal Dust Separator” an improved centrifugal dust separator designed to be used with a toroidal vortex vacuum cleaner. Such a centrifugal dust separator is illustrated in FIG. 1. This centrifugal dust separator advances the art by the addition of a dust collector that uses efficient flow geometry. Here, the dust is collected and stored separately from the cylindrical vortex fluid flow. Further, this separator spins fluid at the high rotational speed of the impeller, which effects efficient separation. Therefore, more complete and reliable separation than possible with conventional separators can occur.  
         [0051]    As seen in FIGS. 1A and 1B, at the bottom of the separator are two concentric tubes, the inner tube  101  and the outer tube  102 , through which fluid flows. The annular duct created between inner tube  101  and outer tube  102  contains straightening vanes  111 . Straightening vanes  111  extend radially outward from the outer wall of inner tube  101  to the inner wall of outer tube  102 . Straightening vanes  111  also extend from the top of the annular duct created by inner tube  101  and outer tube  102  downward. The proximal opening of inner tube  101  curves outward to allow for smooth fluid flow. Centered directly above inner tube  101  is impeller  109  comprising impeller blades  108 , which are fitted to conform to the curvature in inner tube  101 . Motor  110 , which provides power to impeller  109 , is located above impeller  109 . Housing  113  contains impeller blades  108 , separation chamber  107 , and dust collector  105 . Housing  113  connects to the concentric tubing, which is formed by inner tube  101  and outer tube  102 , that provides incoming and outgoing fluid flow. The horizontal cross-section depicted in FIG. 1B illustrates the circular shape of housing  113 . The cylindrical walls of housing  113  maintain the vortex fluid flow. Attached to the cylindrical portion of housing  113  is dust collector  105 . Dust collector  105  is a sealed container in which debris ejected from the vortex accumulate. Housing  113  has an opening in its outer wall through which dust  106  may pass. As shown in the horizontal cross, the edge of the opening facing into the direction of the fluid flow bends slightly inwards to facilitate dust collection. The dust collector  105  is attached to the outer and lower walls of housing  113  as shown in FIG. 1A. The walls of outer tube  102  bend slightly outward to facilitate smooth fluid flow from chamber  107  to the annular exit duct between inner tube  101  and outer tube  102 . However, other arrangements to facilitate fluid flow may be used. Inner tube  101  and outer tube  102  may extend downward and terminate with a toroidal vortex nozzle as disclosed in parent applications. Although this is the preferred use, the centrifugal dust separator is capable of functioning without such a nozzle. Any other concentric nozzle design may be used. In addition, any system that supplies an input flow to inner tube  101  and receives an output flow from an annular duct formed between inner tube  101  and outer tube  102  is capable of utilizing the separator.  
         [0052]    The flow geometry of the centrifugal dust separator is also depicted in FIGS. 1A and 1B. This embodiment involves dust-laden fluid being sucked up through inner tube  101  under the power of impeller  109 . The impeller blades  108  then move the fluid in a circular pattern. Circularly rotating fluid is then directed outwards where it spirals downward along the outer wall of chamber  107  creating a cylindrical vortex flow pattern. The kinetic energy of the circulating fluid creates a higher pressure in dust collector  105  than that of the fluid within the chamber  107 . Depending on the system specifications, this pressure may be higher or lower than the outside ambient pressure. This high pressure forces fluid inward, maintaining the fluid&#39;s circular path. However, circulating dust  106  is not inhibited from traveling straight into dust collector  105  as shown in FIG. 1. When the spiraling fluid reaches the bottom of the outer wall of chamber  107 , the fluid then spirals upward along the inner wall of chamber  107 . Remaining dust particles may still travel outward from the inner spiral of fluid. The result is substantially clean fluid exiting the chamber  107  at the top of its inner wall. The cleaned fluid is then sent into the annular duct created between inner tube  101  and outer tube  102 , in which it flows downward. With the addition of straightening vanes  111 , straight flowing fluid is supplied as a product to a toroidal vortex nozzle or any other desired destination. However, alternative embodiments are possible which do not involve a toroidal vortex nozzle or any nozzle.  
         [0053]    The centrifugal separator in FIGS. 1A and 1B has fluid mixed with dirt and dust passing through impeller  109 . If such an arrangement is considered undesirable, a trap for large debris may be inserted in the fluid input path upstream of impeller  109 . Additionally, the impeller may be replaced with an axial fluid pump or propeller. Such devices may be mounted in inner tube  101 . Further, inner tube  101  may be swelled out for this purpose.  
         [0054]    The centrifugal dust separator is also capable of functioning in various other fluid media, including water, other liquids, and gases. Moreover, the centrifugal dust separator is capable of separating larger objects from fluid, such as nails, pebbles, sand, screws, etc., in addition to fine particles and dust.  
         [0055]    During operation of the aforementioned centrifugal dust separator of FIGS.  1 A and lB, frictional losses may slow fluid flow within chamber  107 . Frictional losses are induced by fluid flow interacting with the walls of chamber  107  and fluid flow entering and exiting dust collector  105 . Nevertheless, the centrifugal separator of the present invention compensates for such frictional losses with the addition of circulating blades, strategically placed baffles, and a specially designed passage into the dust collector.  
         [0056]    The first embodiment of the present invention is depicted in FIGS. 2A and 2B. As shown in FIG. 2A, fluid is impelled at inlet  213  on one side of the separator and expelled out outlet  212  on the other side. One major difference from the separator of FIG. 1 lies in the positioning of inlet  213  and outlet  212 . Collector  202 , similar to that which is depicted in FIG. 1, is contained within outer casing  204 . Also within outer casing  204  is rotating drum  203 . Rotating drum  203  is coupled to driveshaft  214  which is powered by motor  201 . Motor  201  may be fixed to outer casing  204  via bracket members  221 . Driveshaft  214  may be equipped with shaft bearings  205  to reduce friction and stabilize driveshaft  214  during rotation. Coupled to the outside of rotating drum  203  are impeller blades  207  and circulating blades  209 . Impeller blades  207  are preferably constructed with a reverse curve which more smoothly guides fluid to circulating blades  209 . Just before outlet  212 , flow straightening vanes  211  are installed to remove the rotational component from exiting fluid.  
         [0057]    Cylindrical design of separation chamber  210  is illustrated in FIG. 2B. The improved centrifugal dust separator operates by impelling fluid with impeller  206 . Impeller blades  207  spin fluid at the high speed at which they rotate. The rotating fluid then forms a cylindrical vortex fluid flow pattern in separation chamber  210 . Higher mass dust particles  216  are centrifugally separated and ejected in collector  202 . The movement of the rotating fluid increases the pressure in collector  202  since fluid flow  215  exerts an outward force ρRV 2 . Here, ρ=fluid density; R=radius of rotation; and V=fluid&#39;s velocity close to the wall. This high pressure creates, in equilibrium, an inward force of equal magnitude maintaining cylindrical fluid flow  215  without inhibiting smaller dust particles from flowing into collector  202 . Dust flow  216  is shown in FIG. 2B.  
         [0058]    The dust collection in the present invention does not depend on the amount of dust in collector  202 , as in conventional systems where dust collection deteriorates as dust accumulates. Moreover, the separator of the present invention is capable of collecting various other matter such as sand, screws, dirt, nails, bolts, and other objects.  
         [0059]    Fluid travels further from inlet  213 , however, frictional losses are incurred as fluid flow travels along the outer wall of the separation chamber  210 . Such frictional losses occur any time fluid flows along a solid surface. Further frictional losses result from fluid exchange between separation chamber  210  and collector  202 . To minimize the friction of fluid flowing along the outer wall of separation chamber  210 , the wall preferably ahs a highly polished finish. To further compensate for the frictional losses, rotating drum  203  rotates circulating blades  209 . Circulating blades  209  continue to spin fluid for the entire length of separation chamber  210 , thereby replacing kinetic energy lost to friction. Spinning the fluid at a constant velocity for the entire length of separation chamber  210  results in a constant pressure along the entire length of the collector  202 . Without the additional circulating blades  209 , the pressure would gradually decrease as the fluid flow slows due to friction and as a consequence there would be a fluid flow along collector  202  that could allow dust and debris to reenter separation chamber  210  further upstream. Thus, the action of circulating blades  209  results in more thorough separation by maintaining the velocity of spinning fluid flow.  
         [0060]    In order to minimize the fluid exchange between separation chamber  210  and collector  202 , baffles  202  (which are in this case vertical) can be implemented strategically to divide collector  202  into sections. These baffles minimize fluid circulation across collector  202 .  
         [0061]    The separator can be modified to prevent the motor from obstructing incoming fluid. Two such modifications are depicted in FIGS. 3A and 3B. FIG. 3A shows extended inlet  302  which is bent to avoid motor  301 . FIG. 3B shows an embodiment in which motor  301  is mounted on motor mount  308  inside rotating drum  307 . Motor mount  308  may be supported by attaching it (via radial members) to the housing. Thus, flowing fluid does not interact with the motor  301 .  
         [0062]    The separator may be further modified to achieve higher levels of dust separation. To do so, the separator can be elongated axially as shown in FIG. 4. Since the basic design of the separator is the same, the separator can be constructed arbitrarily long to achieve any desired level of separation. Inlet  401 , shaft bearings  406 , bracket members  421 , impeller  402 , impeller blades  407 , flow straightening vanes  405 , and outlet  409  remain as disclosed in previous embodiments of the present invention. Separation chamber  413  is elongated to extend the amount of time fluid spends in separation chamber  413 . Therefore, the number of times the fluid circulates within separation chamber  413  is also increased. Consequently, light and fine dust particles have more time to migrate to the outer wall of separation chamber  413  and be ejected into collector  410 . Likewise, collector  410 , circulating blades  404 , rotating drum  403 , and outer casing  414  are also elongated. Thus, the fluid flow&#39;s high rotational speed is maintained throughout separation chamber  413 . Motor  411  is mounted on motor mount  408  inside rotating drum  403 . Motor mount  409  may be fixed to flow straightening vanes  405  via bracket members  420 .  
         [0063]    As the fluid flow nears outlet  409 , the remaining particles in circulating fluid flow  412  decrease in size. Additionally, the necessary width of the passage into collector  410  decreases as the size of the dust particles decrease. Therefore, the passage into collector  410  preferably narrows as it nears the outlet. The narrower passage minimizes fluid exchange between separation chamber  413  and collector  410 . Thus, the energy losses caused by such fluid exchange can also be minimized.  
         [0064]    The efficiency of separating fine particles from fluid flow depends on the length of time it takes the particles to drift to the outer wall of separation chamber  413 . By metering the rate of fluid flow through the separation system, the operation may be optimized to capture the most dust particles. Valves may be placed at either fluid inlet  401  or fluid outlet  409  in order to meter the rate of fluid flow through the system.  
         [0065]    The outlet of the present invention can be configured to more smoothly guide fluid flow. To achieve this, FIG. 5 depicts modified outlet  500  of an axial flow centrifugal separator in accordance with the present invention. Rotating drum  501  comprises tapered end  502  which smoothly guides fluid flow  503  to outlet tube  504 . Because dust and debris remain close to wall  505  during the end of separation, circulating blades  506  may be tapered as shown. Thus, separation can continue without being compromised while fluid flow  503  passes through the tapered section of circulating blades  506  while minimizing disturbance of exiting fluid flow  503 . Consequently, flow dynamics are optimized.  
         [0066]    In some instances (i.e., when there is a space constraint limiting the size of the separator), a single pass through an axial flow separator may not be suffice for achieving the desired level of separation. In such situations, recycle tube  601  may be fitted to axial flow centrifugal separator  600  of FIG. 6. Here, dirty fluid flow  602  enters the system and mixes with recycled fluid flow  603 . The mixed fluid flow continues through separation chamber  604  as described supra. Cleaned fluid flow  605  exits the system from outlet  609 , but some fluid flow will pass into collector  606 . Once in collector  606 , fluid flow  607  may pass into inlet  608  of recycle tube  601 . Preferably, inlet  608  is as close to outlet  609  as possible while centered within the vertical cross-section of collector  606 . This positioning ensures that the only the cleanest fluid enters inlet  608  because dust and debris tend to circulate around the outer walls of collector  606  or settle to the bottom of collector  606 . Furthermore, the pressure within collector  606  must be maintained higher than the pressure of dirty fluid flow  602  in order to prevent fluid from flowing in the reverse direction in recycle tube  601 . Additionally, valve  610  may be implemented in recycle tube  601  to control the amount of fluid flow that is recycled.  
         [0067]    While the present invention has been described with reference to one or more preferred embodiments, which embodiments have been set forth in considerable detail for the purposes of making a complete disclosure of the invention, such embodiments are merely exemplary and are not intended to be limiting or represent an exhaustive enumeration of all aspects of the invention. The scope of the invention, therefore, shall be defined solely by the following claims. Further, it will be apparent to those of skill in the art that numerous changes may be made in such details without departing from the spirit and the principles of the invention.