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 air through the system as well as creating a cylindrical vortex fluid flow providing an efficient and simple configuration. Also disclosed herein is a complete toroidal vortex vacuum cleaner in which a toroidal vortex nozzle is used in conjunction with the centrifugal separator. The vacuum cleaner exhibits recirculating airflow that not only prevents unseparated dust from escaping into the atmosphere, but also conserves the kinetic energy of the flowing air. The present invention excels in producing clean air of a better quality more efficiently, more quietly, and more simply than the prior art.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS  
       [0001]    This application is filed as 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 initially, and thus generally, to an improved vacuum cleaner. More specifically, the present invention relates to an improved vacuum cleaner that utilizes a cylindrical vortex flow such that the air pressure within the dust collector is above air pressure in the separation chamber. The high pressure maintains the cylindrical vortex flow pattern without preventing dust particles from traveling straight into the dust collector. Moreover, the present invention&#39;s impeller serves the dual purpose of both moving fluid through the system and creating a cylindrical vortex by spinning air at the blade speed of the impeller. Thus, the dual purpose impeller provides both efficiency and simplicity to the separator. The present invention eliminates the need for vacuum bags, HEPA filters, or liquid baths. Further, straightening vanes in the outlet air flow provide non-rotating air to the vacuum cleaner nozzle. The present invention provides non-rotating, substantially dust-free air to the vacuum cleaner nozzle. The preferred embodiment utilizes a toroidal vortex vacuum cleaner nozzle. However other nozzles or application of straightened airflow are possible.  
         BACKGROUND OF THE INVENTION  
         [0003]    The use of vortex forces is known in various arts, including the separation of matter from liquid and gas effluent flow streams, the removal of contaminated air from a region and the propulsion of objects. However, cylindrical vortex flow has not previously been provided in a bagless vacuum device having light weight and high efficiency.  
           [0004]    The prior art is strikingly devoid of references dealing with toroidal vortices in a vacuum cleaner application. However, an Australian reference has some similarities. This Australian reference does not approach the scope of the present invention, but it is worth disusing its key features of operation so that one skilled in the art can readily see how its shortcomings are overcome by that which is disclosed herein.  
           [0005]    In discussing Day International Publication number WO 00/19881 (the “Day publication”), an explanation of the Coanda effect is required. This is the ability for a jet of air to follow around a curved surface. It is usually referred to without explanation, but is generally understood provided that one makes use of “momentum” theory: a system based on Newton&#39;s laws of motion. Utilizing the “momentum” theory instead of Bernoulli&#39;s principles provide a simpler understanding of the Coanda effect.  
           [0006]    [0006]FIG. 1 shows the establishment of the Coanda effect. In (A) air is blown out horizontally from a nozzle  100  with constant speed V. The nozzle  100  is placed adjacent to a curved surface  102 . Where the air jet  101  touches the curved surface  102  at point  103 , the air between the jet  101  and the surface  102  as it curves away is pulled into the moving airstream both by air friction and the reduced air pressure in the jet stream, which can be derived using Bernoulli&#39;s principles. As the air is carried away, the pressure at point  103  drops. There is now a pressure differential across the jet stream so the stream is forced to bend down, as in (B). The contact point  104  has moved to the right. As air is continuously being pulled away at point  104 , the jet continues to be pulled down to the curved surface  102 . The process continues as in (C) until the air jet velocity V is reduced by air and surface friction.  
           [0007]    [0007]FIG. 2 shows the steady state Coanda effect dynamics. Air is ejected horizontally from a nozzle  200  with speed represented by vector  201  tangentially to a curved surface  203 . The air follows the surface  203  with a mean radius  204 . Air, having mass, tries to move in a straight line in conformance with the law of conservation of momentum. However, it is deflected around by a pressure difference across the flow  202 . The pressure on the outside is atmospheric, and that on the inside of the airstream at the curved surface is atmospheric minus          V 2 /R where          is the density of the air.  
           [0008]    The vacuum cleaner Coanda application of the Day publication has an annular jet  300  with a spherical surface  301 , as shown in FIG. 3. The air may be ejected sideways radially, or may have a spin to it as shown with both radial and tangential components of velocity. Such an arrangement has many applications and is the basis for various “flying saucer” designs.  
           [0009]    The simplest coanda nozzle  402  described in the Day publication is shown in FIG. 4. Generally, the nozzle  402  comprises a forward housing  407 , rear housing  408  and central divider  403 . Air is delivered by a fan to an air delivery duct  400  and led through the input nozzle  401  to an output nozzle  402 . At this point the airflow cross section is reduced so that air flowing through the nozzle  402  does so at high speed. The air may also have a rotational component, as there is no provision for straightening the airflow after it leaves the air pumping fan. The central divider  403  swells out in the terminating region of the output nozzle  402  and has a smoothly curved surface  404  for the air to flow around into the air return duct using the Coanda effect.  
           [0010]    Air in the space below the Coanda surface moves at high speed and is at a lower than ambient pressure. Thus dust in the region is swept up  405  into the airflow  409  and carried into the air return duct  406 . For dust to be carried up this duct, the pressure must be low and a steady flow rate must be maintained. After passing through a dust collection system the air is sent through a fan back to the air delivery duct. Constriction of the airflow by the output nozzle leads to a pressure above ambient in this duct ahead of the jet. In sum, air pressure within the system is above ambient in the air delivery duct and below ambient in the air return duct.  
           [0011]    Coanda attraction to a curved surface is not perfect. As shown in FIG. 5, not all the air issuing from the output nozzle is turned around to enter the air return duct. An outer layer of air proceeds in a straight fashion  501 . When the nozzle is close to the floor, this stray air will be deflected to move horizontally parallel to the floor and should be picked up by the air return duct if the pressure there is sufficiently low. In this case, the system may be considered sealed; no air enters or leaves, and all the air leaving the output nozzle is returned.  
           [0012]    When the nozzle is high above the ground, however, there is nothing to turn stray air  501  around into the air return duct and it proceeds out of the nozzle area. Outside air  502 , with a low energy level is sucked into the air return to make up the loss. The system is no longer sealed. An example of what happens then is that dust underneath and ahead of the nozzle is blown away. In a bagless system such as this, where fine dust is not completely spun out of the airflow but recirculates around the coanda nozzle, some of this dust will be returned to the surrounding air.  
           [0013]    Air leakage is exacerbated by rotation in the air delivery duct caused by the pumping fan. Air leaving the output nozzle rotates so that centrifugal force spreads out the airflow into a cone. The effect is to generate a higher quantity of stray air. Air rotation can be eliminated by adding flow straightening vanes to the air delivery duct, but these are neither mentioned nor illustrated in the Day publication.  
           [0014]    A side and bottom view of an annular Coanda nozzle  600  is shown in FIG. 6. This is a symmetrical version of the nozzle shown in FIG. 4. Generally, the nozzle  600  comprises outer housing  602 , air delivery duct  601 , air return duct  605 , flow spreader  603  and annular Coanda nozzle  604 . Air passes down though the central air delivery duct  601 , and is guided out sideways by a flow spreader  603  to flow over an annular curved surface  604  by the Coanda effect, and is collected through the air return duct  605  by a tubular outer housing  602 .  
           [0015]    This arrangement suffers from the previously described shortcomings in that air strays away from the Coanda flow, particularly when the jet is spaced away from a surface.  
           [0016]    While it is conceivable that the performance of the invention of the Day publication would be improved by blowing air in the reverse direction, down the outer air return duct and back up through the central air delivery duct, stray air would then accumulate in the central area rather than be ejected out radially. Unfortunately, the spinning air from the air pump fan would cause the air from the nozzle to be thrown out radially due to centrifugal force (centripetal acceleration) and the system would not work. This effect could be overcome by the addition of flow straightening vanes following the fan. However, none are shown, and one may conclude that the effects of spiraling airflow were not understood by the designer.  
           [0017]    The Day publication has more complex systems with jets to accelerate airflow to pull it around the Coanda surface, and additional jets to blow air down to stir up dust and others to optimize airflow within the system. However, these additions are not pertinent to the analysis herein.  
           [0018]    The problems with the invention of the Day publication are remedied by the Applicant&#39;s toroidal vortex vacuum cleaner. The toroidal vortex vacuum cleaner is a bagless design and one in which airflow must be contained within itself at all times. The contained airflow continually circulates from the vacuum cleaner nozzle to a centrifugal separator and back to the nozzle. Since dust is not always fully separated, some dust will remain in the airstream heading back towards the nozzle. The air already withing the system, however, does not leave the system. This prevents dust from escaping back into the atmosphere. It is not sufficient to design the cleaner to ensure essentially sealed operation while operating adjacent to a surface being cleaned, operation must also remain sealed when away from a surface to prevent fine dust particles from re-entering the surrounding air.  
           [0019]    Another reason for maintaining sealed operation when the apparatus is away from the surface is to prevent the vacuum cleaner nozzle from blowing surface dust around.  
           [0020]    The Day publication, in most of its configurations, is coaxial in that air is blown out from a central duct and is returned into a coaxial return duct. The toroidal vortex attractor is coaxial, but operates the in the opposite direction. With the toroidal vortex attractor, air is blown out of an annular duct and returned into a central duct.  
           [0021]    The inventor has also noted the presence of “cyclone” bagless vacuum cleaners in the prior art. The present invention utilizes an entirely different type of flow geometry allowing for much greater efficiency and lighter weight. Nonetheless, the following represent references that the inventor believes to be representative of the art in the field of bagless cyclone vacuum cleaners. One skilled in the art will plainly see that these do not approach the scope of the present invention, but they have been included for the sake of completeness.  
           [0022]    Dyson U.S. Pat. No. 4,593,429 discloses a vacuum cleaning appliance utilizing series connected cyclones. The appliance utilizes a high-efficiency cyclone in series with a low-efficiency cyclone. This is done in order to effectively collect both large and small particles. In conventional cyclone vacuum cleaners, large particles are carried by a high-efficiency cyclone, thereby reducing efficiency and increasing noise. Therefore, Dyson teaches incorporating a low-efficiency cyclone to handle the large particles. Small particles continue to be handled by the high-efficiency cyclone. While Dyson does utilize a bagless configuration, the type of flow geometry is entirely different. Furthermore, the energy required to sustain this flow is much greater than that of the present invention.  
           [0023]    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 comparatively large particle size. The dust and dirt is sucked into the cleaner by centrifugal force. 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.  
           [0024]    Specifically, the dirt collecting tub 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 contained in the air is separated from the air by centrifugal force and is collected at the dirt collecting tub. A dirt separating grill having a plurality of 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 connecting device, thus extending the period of time before replacing the paper filter.  
           [0025]    The device of Song et al. differs primarily from the present invention in that it requires a filter. The present invention utilizes such an efficient flow geometry that the need for a filter is eliminated. Furthermore, the conventional cyclone flow of Song et al is traditionally less energy efficient and noisier than the present invention.  
           [0026]    Also relevant to the present invention are the Prior Arts Kasper et al., U.S. Pat. No. 5,030,257, Tuvin et al., U.S. Pat. No. 6,168,641, and Moredock, U.S. Pat. No. 5,766,315. However none of these prior arts claim an invention as simple or efficient as the present invention. First, Kasper et al. make 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. The liquid then captures the debris and the cleaned air is free to return to the inside of the cylinder. Cleaned air is further sent upwardly out of the cylinder.  
           [0027]    The first major problem with Kasper et al. evolves from the use of a water bath. A liquid bath adds both weight and complexity. Additional maintenance is also required to change the liquid, prevent corrosion, etc. In contrast, the present invention has no need to utilize liquid to separate debris from air. In fact, the present invention can separate matter from liquids as well. Kasper et al.&#39;s device could not achieve such results given that the liquid-air surface is integral for collecting particles. More specific to the cyclone separator, the cyclone is maintained solely by the wall of the cylinder. The present invention uses a solid surface to maintain cylindrical flow in conjunction with high pressure from 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. Additionally, Kasper et al. mix circulating air ejected from the cyclone with non-circulating incoming air, thereby inducing energy losses. The present invention avoids this problem by ensuring that all incoming air is traveling in a circular path. Hence, the present invention is simpler, lighter, more efficient, and less noisy.  
           [0028]    Tuvin et al. also make use of a cyclone separation system. Tuvin et al.&#39;s patent includes a cyclone separator that ejects particles outward from a cyclone. However, there are several major differences between the present invention and Tuvin et al. First, the means for creating the cyclone flow is not the same. The present invention utilizes an impeller, centrifugal pump, or propeller to create the cylindrical airflow necessary to achieve separation. In contrast, Tuvin et al.&#39;s patent directs the air entering the cyclone chamber tangentially with the chamber&#39;s wall. Therefore, in Tuvin et al., the chamber&#39;s wall is what then forces the air into cylindrical flow.  
           [0029]    In terms of efficiency, the present invention utilizes an impeller, propeller, or centrifugal pump to create the cylindrical flow and the necessary suction in a single step. This is advantageous from energy saving and simplicity standpoints since two separate steps are not necessary. Tuvin et al., in contrast, makes use of a filter as the final step before air exits the device. This is disadvantageous because filters impede airflow, thus consuming energy and compromising efficiency. Filters are not needed in the present invention because separation is sufficiently performed. Moreover, the present invention can remove both large and small particles in one step. Tuvin, et al.&#39;s invention necessitates two steps, involving a course separator and a cyclone chamber. Therefore, the cyclone chamber must only capable of separating fine particles. Efficiency is further reduced by these extra steps while complexity is added. Consequently, the present invention in simpler and more efficient then that disclosed in Tuvin et al.  
           [0030]    Finally, Moredock U.S. Pat. No. 5,766,315 discloses a centrifugal separator that ejects particles radially. Nevertheless, the apparatus is not as simple and efficient as the present invention. In Tuvin et al., the cylindrical flow is created by allowing air to enter the dome tangentially in respect to the wall. The same disadvantages concerning efficiency and simplicity apply. Also, the ejection duct used by Moredock differs significantly from the present invention&#39;s dust collector. 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. The duct allows air to exit along with the particles. No indication of back-pressure is disclosed as in the present invention. Consequently, air pressure can not be used to maintain cylindrical flow. Without pressure back-pressure assisting stabilization, airflow is further disrupted reducing the acceptable width of the slot. Furthermore, Moredock allows air to exit the system. This air is still dust-laden and needs further cleaning. Also in Moredock, kinetic energy from the exiting air is lost from the system. However, the present invention keeps the dust-laden air within the chamber and dust collector. No dust-laden air is allowed to exit. Therefore, the present invention is not only simpler, more efficient, but also more effective than that disclosed in Moredock.  
           [0031]    Thus, as stated above, there is a clear need for a light weight, efficient and quiet bagless vacuum cleaner.  
         SUMMARY OF THE INVENTION  
         [0032]    The present invention was developed from the applicant&#39;s prior invention, a toroidal vortex vacuum cleaner.  
           [0033]    Described herein are embodiments that deal with both toroidal vortex vacuum cleaner nozzles and systems. The nozzles include simple concentric systems and more advanced, optimized systems. Such optimized systems utilize a thickened inner tube that is rounded off at the bottom for smooth airflow from the air delivery duct to the air return duct. It is also contemplated that the nozzle include flow straightening vanes to eliminate rotational components in the airflow that greatly harm efficiency. The cross section of the nozzle need not be circular, in fact, a rectangular embodiment is disclosed herein, and other embodiments are possible.  
           [0034]    Also disclosed herein is a complete vacuum system. The preferred embodiment takes in dust-laden air from the nozzle, and ejects dust-free air back to the nozzle utilizing toroidal vortex flow. Dust-laden air is taken in through an inner tubing leading into the impeller blades. The blades accelerate incoming air into a circular pattern inducing the cylindrical vortex flow in a separation chamber. Alternatively, an axial pump or propeller can be mounted in the inner tube. The inner tube may be swelled out for this purpose. Inside the separation chamber, dust is expelled to a dust collector. The cleaned air is then driven into an outer tube, which contains the inner tube. Therefore, the inner and outer tube form a concentric system in which the dust-laden airflow is contained in the inner tube; and clean airflow is contained between the outer and inner tubes. Also between the outer and inner tubes are straightening vanes. These straightening vanes provide non-rotating airflow back to the nozzle. Straightened air is needed for a toroidal vortex nozzle to function properly. If air is rotating, a significant amount can be expelled into the atmosphere, thus compromising the efficiency of the nozzle. However, the cylindrical vortex in the centrifugal separator is an inherent part of the dust separation process and is in itself independent of the toroidal vortex nozzle operation.  
           [0035]    More specific to the separation chamber, a cylindrical vortex is formed such that a circular pattern of flow exiting from the impeller spirals downward along the chamber&#39;s outer wall, and then upward along the chamber&#39;s inner wall. At the top of the chamber&#39;s inner wall is the opening leading air out of the chamber and into the annular duct between the outer and inner tubes. The circular flow of the air acts as a centrifuge, forcing the higher mass dust particles outward. The spiraling air also creates a pressure in the dust collector that is above that in the body of the separation chamber due to kinetic energy of the circulating air. This high pressure pushes the spiraling air inward, maintaining the air&#39;s circular path. However, the dust particles are not inhibited from traveling straight into the collector.  
           [0036]    Unlike other vacuum cleaners that employ centrifugal dust separation (e.g., the “cyclone” types discussed previously), the present invention spins the air 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 airflow. No vacuum bag, liquid bath, or filter is required.  
           [0037]    One of the main features of the present invention is the inherent low power consumption. The losses that must exist when bags or filters are utilized are not present here. Bags and filters resist airflow, thus requiring greater power to maintain a proper flowrate. Additional efficiency arises from the closed air system. Energy supplied by the impeller is not lost because air is not expelled into the atmosphere, but is instead retained in the system. Finally, since only smooth changes in the direction of airflow are made, the effect on the energy of the moving air is minimal. Hence, the disclosed system contains efficiency provisions not considered by the prior art. Furthermore, the design is expected to be virtually maintenance free.  
           [0038]    Thus, it is an object of the present invention to utilize cylindrical vortices in a dust separator application.  
           [0039]    Additionally, it is an object of the present invention to provide an efficient dust separator.  
           [0040]    Furthermore, it is an object of the present invention to provide a quiet vacuum cleaner.  
           [0041]    It is a further object of the present invention to provide a light weight dust separator.  
           [0042]    In addition, it is an object of the present invention to provide a low-maintenance dust separator.  
           [0043]    It is yet another object of the present invention to provide a bagless dust separator.  
           [0044]    It is also an object of the present invention to provide non-rotating air with highly reduced dust content to recycle through the vacuum cleaner&#39;s toroidal vortex nozzle.  
           [0045]    It is a further object of the present invention to provide a dust separator that does not require the use of filters.  
           [0046]    It is also an object of the present invention to provide non-rotating, substantially dust-free air as a product. 
       
    
    
     SUMMARY OF THE DRAWINGS  
       [0047]    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.  
         [0048]    For a more complete understanding of the present invention, reference is now made to the following drawings in which:  
         [0049]    [0049]FIG. 1, already discussed, depicts the establishment of the coanda effect (PRIOR ART);  
         [0050]    [0050]FIG. 2, already discussed, depicts the dynamics of the coanda effect (PRIOR ART);  
         [0051]    [0051]FIG. 3, already discussed, depicts the coanda effect on a spherical surface with both radial and tangential components of motion (PRIOR ART);  
         [0052]    [0052]FIG. 4, already discussed, depicts a coanda vacuum cleaner nozzle (PRIOR ART);  
         [0053]    [0053]FIG. 5, already discussed, depicts the undesirable airflow in a coanda vacuum cleaner nozzle (PRIOR ART);  
         [0054]    [0054]FIG. 6, already discussed, depicts a side and bottom view of an annular coanda vacuum cleaner nozzle (PRIOR ART);  
         [0055]    [0055]FIG. 7 depicts a toroidal vortex, shown sliced in half;  
         [0056]    [0056]FIG. 8 graphically depicts the pressure distribution across the toroidal vortex of FIG. 7;  
         [0057]    [0057]FIG. 9 depicts a toroidal vortex attractor;  
         [0058]    [0058]FIG. 10 depicts a cross section of a concentric vacuum system;  
         [0059]    [0059]FIG. 11 depicts a concentric vacuum system with air being sucked up the center and blown down the sides;  
         [0060]    [0060]FIG. 12 depicts the dynamics of the reentrant airflow of the system of FIG. 11;  
         [0061]    [0061]FIG. 13 depicts a cross section of an exemplary toroidal vortex vacuum cleaner nozzle in accordance with the present invention;  
         [0062]    [0062]FIG. 14 depicts a perspective view of an exemplary rectangular toroidal vortex vacuum cleaner nozzle in accordance with the present invention; and  
         [0063]    [0063]FIG. 15 depicts a cross section of an exemplary toroidal vortex bagless vacuum cleaner having an exemplary circular plan form.  
         [0064]    [0064]FIG. 16 depicts a vertical and horizontal cross sections of an exemplary toroidal vortex bagless vacuum cleaner with a dust collector and circular plan form. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0065]    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.  
         [0066]    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. The words “clockwise” and “counterclockwise” will indicate rotation relative to a standard “right-handed” coordinate system. Such terminology will include the words above specifically mentioned, derivatives thereof and words of similar import.  
         [0067]    A toroidal vortex is a donut of rotating air. The most common example is a smoke ring. It is basically a self-sustaining natural phenomenon. FIG. 7 shows a toroidal vortex  700 , at an angle, and sliced in two to illustrate the airflow  701 . In a section of the vortex, a particular air motion section is shown by a stream tube  702 , in which the air constantly circles around. Here it is shown with a mean radius  703  and mean speed  704 . Circular motion is maintained by a pressure differential across the stream tube, the pressure being higher on the outside than the inside. This pressure difference Δp is, by momentum theory, Δp=         V 2 /R where          is the air density, R is radius  703  and V is velocity  704 . Thus the pressure decreases from the outside of the toroid to the center of the cross section, and then increases again towards the center of the toroid. The example shows air moving downwards on the outside of the toroid  700 , but the airflow direction can be reversed for the function and pressure profile to remain the same. The downward outside motion is chosen because it is the preferred direction used in the toroidal vortex vacuum cleaner of the present invention.  
         [0068]    [0068]FIG. 8 shows a typical pressure profile across the toroidal vortex. Shown is the pressure on axis  801  as a function of distance in the x direction  802 . Line  803  is a reference for atmospheric pressure, which remains constant along the x direction. The present invention was developed from a toroidal vortex attractor previously described by the inventor.  
         [0069]    [0069]FIG. 9 shows a toroidal vortex attractor that has a motor  901  driving a centrifugal pump located within an outer housing  902 . The centrifugal pump comprises blades  903  and backplate  904 . This pumps air around an inner shroud  905  so that the airflow is a toroidal vortex with a solid donut core. Flow straightening vanes  906  are inserted after the centrifugal pump and between the inner shroud  905  and the outer casing  902  in order to remove the tangential component of air motion from the airflow. The air moves tangentially around the inner shroud  905  cross section, but radially with respect to the centrifugal pump.  
         [0070]    Air pressure within the housing  902  is below ambient. The pressure difference between ambient and inner air is maintained by the curved airflow around the inner shroud&#39;s  905  lower outer edge. The outer air turns the downward flow between the inner shroud  905  and outer casing  902  into a horizontal flow between the inner shroud and the attracted surface  907 . This pressure difference is determined by          v 2 /r where v is the speed of the air circulating  908  around the inner shroud  905 , r is the radius of curvature  909  of the airflow and          is the air density. The maximum air pressure differential is determined by the centrifugal pump blade tip speed (V) at point  910 , and tip radius (R)  911  (         V 2 /R).  
         [0071]    The toroidal vortex attractor  900  can be thought of as a vacuum cleaner without a dust collection system. Dust particles picked up from the attracted surface  907  are picked up by the high speed low pressure airflow and circulate around.  
         [0072]    The toroidal vortex vacuum cleaner is a bagless design and one in which airflow must be contained within itself at all times. Air continually circulates from the area being cleaned, through the dust collector and back again. The contained airflow continually circulates from the vacuum cleaner nozzle, to a centrifugal separator, and back to the nozzle. Since dust is not always fully separated, some dust will remain in the airstream heading back, towards the nozzle. The air already withing the system, however, does not leave the system preventing dust from escaping back into the atmosphere. It is not sufficient to design the cleaner to ensure essentially sealed operation while operating adjacent to a surface being cleaned, operation must also remain sealed when away from a surface to prevent fine dust particles from re-entering the surrounding air.  
         [0073]    Sealed operation away from a surface is also important because it prevents the vacuum cleaner nozzle from blowing surface is dust around.  
         [0074]    The toroidal vortex attractor is coaxial and operates in a way that air is blown out of an annular duct and returned into a central duct. FIG. 10 shows a system  1000  comprising outer tube  1001  and inner tube  1002  in which air passes down the inner tube  1003  and returns up the outer tube  1001 . While it would be desirable that the outgoing air returns up into the air return duct  1005 ; a simple experiment shows that this is not so. Air from the central delivery duct  1004  forms a plume  1007  that continues on for a considerable distance before it disperses. Thus, air is sucked into the air return duct from the surrounding area  1006 . This arrangement, without Coanda jet shaping is clearly unsuited to a sealed vacuum cleaner design.  
         [0075]    [0075]FIG. 11 shows a system  1100  having the reverse airflow of FIG. 10. Again, system  1100  comprises outer tube  1101  and inner tube walls  1102  (which form inner tube  1103 ). Air is blown down the outer air delivery duct  1104  and returned up the central return duct  1105 . Air is initially blown out in a tube conforming to the shape of the outer air delivery duct  1104 . As this air originates in the inner tube  1103 , replacement air must be pulled from the space inside the tube of outgoing air. This leads to a low pressure zone at A, within and below the air return duct  1105 . Consequently air is pulled in at A from the outgoing air. Thus the air (whose flow is exemplified by arrows  1107 ) is forced to turn around on itself and enter the return duct  1105 . Such action is not perfect and a certain amount of air escapes  1108  at the sides of the air delivery duct, and is replaced by the same small amount of air  1106  being drawn into the air return duct  1105 .  
         [0076]    Air interchange is reduced from the automatic lowering of the air pressure within the concentric system. FIG. 12 shows air returning from the delivery duct  1104  into the return duct  1105  with radius of curvature (R)  1203  and the velocity at  1204 . With airspeed V at  1204 , the pressure difference between the ambient outer air and the inside is          V 2 /R, where          is the air density. The airflow at the bottom of the concentric tubes is in fact half of a toroidal vortex, the other half being at the top of the inner tube within the outer casing  1101 . The system of FIGS. 11 and 12 is thus a vortex system, with a low internal pressure and minimal mixing of outer and inner air.  
         [0077]    The simple concentric nozzle system shown in FIGS. 11 and 12 can be optimized into an effective toroidal vortex vacuum cleaner nozzle  1300  depicted in FIG. 13. The inner tube  1301  is thickened out and rounded off at the bottom (inner fairing  1306 ) for smooth airflow around from the air delivery duct  1302  to the air return duct  1303 . The outer tube  1304  is extended a little way below the inner tube  1301  end and rounded inwards somewhat so that air from the delivery duct  1302  is not ejected directly downwards but tends towards the center. This minimizes the amount of air leaking sideways from the main flow. The nozzle has flow straightening vanes  1305  to eliminate any corkscrewing in the downward air motion in the air delivery duct  1302  that would throw air out sideways from the bottom of the outer tube  1304  due to centrifugal action. When compared to the coanda nozzles of the prior art, the vortex nozzle  1300  has less leakage and has a much wider opening for the high speed air flow to pick up dust.  
         [0078]    The vortex nozzle has so far been depicted as circular in cross section, but this is not at all necessary. FIG. 14 shows a rectangular nozzle  1400  in which the ends are terminated by bringing the inner fairings  1401  to butt against the outer tube  1402 . Air is delivered via the delivery duct  1403  and returns via the return duct  1404 . Flow straightening vanes are omitted for clarity, but are, of course, essential. An alternate system, not shown, is to carry the nozzle cross section of FIG. 13 around the ends, as there will be some air leakage around the flat ends.  
         [0079]    [0079]FIG. 15 shows the addition of a centrifugal dirt separator, yielding a complete toroidal vortex vacuum cleaner  1500 . Again, the ducting is created by an inner tube  1507  placed concentrically within outer tube  1508 . Airflow through the outer air delivery duct  1502 , the inner air return duct  1503  and the toroidal vortex nozzle  1506  (comprising flow straightening vanes  1504  and inner fairing  1505 ) are as described previously in FIGS. 12, 13 and  14 . The air mover is a centrifugal air pump (as in the toroidal vortex attractor of FIG. 9) comprising motor  1509 , backplate  1510  and blades  1511 . Air leaving the centrifugal pump blades is spinning rapidly so that dust and dirt are thrown to the circular sidewall of the outer casing  1512 . Air moves downward and inwards to follow the bottom of the dirt box  1501  so that dirt is precipitated there as well. The air then turns upwards over a dirt barrier  1513  and down the air delivery duct  1502 . At this point, the air is clean except for fine particulates that fail to be deposited in the dirt box  1501 . These particulates circulate through the system repeatedly until they are finally deposited out. The system operates below atmospheric pressure so that air laden with fine dust is constrained within the system and cannot escape into the surrounding atmosphere. After use, the dirt that has been collected in the dirt box  1501  can be emptied via the dirt removal door  1514 .  
         [0080]    [0080]FIG. 15 depicts a circular nozzle  1506 , but the system works equally well with the rectangular nozzle of FIG. 14. Various nozzle shapes can be designed and will operate satisfactorily, providing that the basic cross section of FIG. 13 is used.  
         [0081]    The present invention, presented in FIG. 16, involves an improved centrifugal dust separator. Improvement is made by the addition of a dust collector  1605 .  
         [0082]    The new toroidal vortex vacuum cleaner is also a bagless design with additional features to provide more thorough separation of air and dust by separating the main airflow from the dust collection.  
         [0083]    The preferred embodiment of the present invention is designed as shown in FIG. 16. At the bottom are two concentric tubes, the inner tube  1601  and the outer tube  1602 , through which fluid may pass. The annular duct created between inner tube  1601  and outer tube  1602  contains straightening vanes  1611 . Straightening vanes  1611  extend radially outward from the outer wall of inner tube  1601  to the inner wall of outer tube  1602 . Straightening vanes  1611  also extend from the top of the exit duct created by the inner tube  1601  and outer tube  1602  downward. The top of the inner tube  1601  curves outward such that its vertical cross section, as shown in FIG. 16, forms semicircles arranged with the open side of the circle facing downward. Centered directly above the inner tube  1601  is the impeller  1609 . At the outside of the impeller are the impeller blades  1608 , which are fitted to conform to the curvature in the inner tube  1601 . The motor  1610  which provides power to the impeller  1609  is located above the impeller  1609 . Housing is provided containing the impeller blades, separation chamber, dust collector. The dust housing connects to the concentric tubing providing in and out flow. The horizontal cross of FIG. 16 section illustrates the circular shape of the housing. The cylindrical walls of the housing maintain the vortex airflow. Attached to the cylindrical housing, is the dust collector  1605 . The dust collector  1605  is a sealed container in which debris ejected from the vortex accumulate. The housing has an opening in its outer wall through which dust may pass. As shown in the horizontal cross, the edge of the opening facing into the direction of airflow bends slightly inwards to facilitate dust collection. The dust collector  1605  is attached to the outer and lower walls of the housing as shown in FIG. 16. The walls of the outer tube  1602  bend slightly outward to facilitate smooth airflow from the chamber  1607  to the annular exit duct between inner tube  1601  and outer tube  1602 . Nevertheless, other arrangement to facilitate airflow just as well may be used. The inner tube  1601  and outer tube  1602  may extend downward and terminate with a toroidal vortex nozzle as depicted in FIG. 13. Although this is the preferred embodiment, 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  1601  and receives an output flow from annular duct formed between inner tube  1601  and outer tube  1602  is capable of utilizing the separator. This is a full disclosure of all parts and features embodied the centrifugal dust separator.  
         [0084]    The flow geometry of the present invention is also depicted in FIG. 16. This embodiment involves dust-laden air being sucked up through the inner tube  1601  under the power of the impeller  1609 . The impeller blades  1608  then move the air in a circular pattern. Circularly rotating air is then directed outwards where it spirals downward along the outer wall of the chamber  1607  creating a cylindrical vortex flow pattern. The kinetic energy of the circulating air creates a higher pressure than that of the air within the chamber  1607 . This higher pressure is maintained in the dust collector. Depending on the system geometry, this pressure may be higher or lower than the outside ambient. This high pressure forces air inward maintaining air&#39;s circular path. However, the circulating dust is not inhibited from carrying straight into the dust collector as shown in FIG. 16. When the spiraling air reaches the bottom of the outer wall of the chamber  1607 , the air then spirals upward along the inner wall of the chamber  1607 . Remaining dust particles may still travel outward from the inner spiral of air. The result is substantially clean air exiting the chamber  1605  at the top of its inner wall. The exiting, cleaned air is then sent into the annular duct created between the inner tube  1601  and the outer tube  1602 , in which it flows downward. With the addition of straightening vanes  1611 , straight flowing air is supplied as a product to a toroidal vortex nozzle in the preferred embodiment. However, alternative embodiments are possible which do not involve a toroidal vortex nozzle or any nozzle.  
         [0085]    The preferred embodiment in FIG. 16 has air mixed with dirt and dust passing through the impeller  1609 . If such an arrangement is considered undesirable, the impeller may be replaced with axial air pump or propeller. Such devices may be mounted in the inner tube  1601 . The inner tube  1601  may be swelled out for this purpose. Also, the addition of a separate centrifugal separator is contemplated that may be inserted into the air return path and may be driven by the same motor shaft as the impeller  1609 .  
         [0086]    The present invention is also capable of functioning in various fluid media, including water and other liquids and gases. Moreover, the present invention is capable of separating larger objects from fluid, such as nails, pebbles, sand, screws, etc., in addition to fine particles and dust.  
         [0087]    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.