Abstract:
Disclosed is an improved debris collection apparatus that utilizes a toroidal vortex within the apparatus housing to establish a pressure differential between the outside of the device and the inside. This system and its derivatives are essentially closed systems-there is no constant intake and exhaust of fluid. Included in the debris collection apparatus is a compaction means that captures debris caught in the toroidal vortex flow, and deposits it in a desired chamber.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS  
       [0001]    This application 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 initially, and thus generally, to an improved debris collection apparatus. More specifically, the present invention relates to an improved debris collection apparatus that utilizes a toroidal vortex such that the air pressure within the device housing is below atmospheric. In the present invention, this prevents debris-laden air within the device from being carried to the surrounding atmosphere. The addition of enhanced collection apparatus ensures that attracted debris is properly deposited within the device.  
         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, a toroidal vortex has not previously been provided in a vacuum device having light weight and high efficiency.  
           [0004]    The prior art is strikingly devoid of references dealing with toroidal vortices in a particulate/debris collection application. However, an Australian reference has some similarities. Though it does not approach the scope of the present invention, it is worth disusing its key features of operation such 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 WO00/19881 (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 generally referred to without explaining the effect, but is simply understood provided that one makes use of “momentum” theory; a system based on Newton&#39;s laws of motion, rather than try to weave an understanding from Bernoulli.  
           [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. As the air is carried away, the pressure at point  103  drops. There is now a pressure difference 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 QV 2 /R where Q 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  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 maintained. After passing through a dust collection system the air is connected 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. The overall system is not shown, as this is not necessary to understand its fundamental characteristics.  
           [0011]    Coanda attraction to a curved surface is not perfect, and 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 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, the basis of the present invention, is coaxial and operates the reverse way in that air is blown out of an annular duct and returned into a central duct. The one is the reverse of the other.  
           [0019]    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. Further, with regard to the improved collection apparatus of the present invention, applicant has noted the presence of refuse collection and compression apparatus. However, none of these apparatus approach the scope of the present invention. Nonetheless, the following represent references that the inventor believes to be representative of the art in the applicable fields. One skilled in these arts will plainly see that even these do not approach the scope of the present invention.  
           [0020]    Reinhall U.S. Pat. No. 4,379,385 discloses a compaction apparatus for use with lawn grooming equipment such as a lawn mower, leaf blower and the like. The device comprises a compactor housing having an inlet opening at one end to receive the refuse material picked up from the lawn and a screw conveyor rotatably mounted within the housing to transport and compact the received material as it is advanced through the conveyor housing. Perforations in the housing provide outlets for evacuating from the housing, air and moisture separated from the compressed material as it is initially compacted in the housing. A flexible tubular collector casing or hose is extensibly connected to the outlet end of the compactor housing, into which the initially compacted material is continuously advanced. The cuttings and other refuse material are further compacted against the interior wall of the casing by the force of the continuously advancing material and form a plug in the end of the hose-like casing, causing it to extend from the outlet end of the compactor housing. The compacted refuse material crawls in serpentine fashion along a guided path on the top of the main body of the grooming equipment. When the casing, filled up with backed-up refuse material, has been extended or unfolded, the resultant refuse is severed from the compactor housing and may be dropped on the lawn for subsequent removal to composting dump or other collection site. The screw conveyor may be provided with a bore for transporting a composting fluid from the inlet end of the conveyor to be discharged into the housing towards its outlet end. While the apparatus of Reinhall is directed to the attraction and compaction of refuse, the present invention utilizes completely different means to these ends. To attract the refuse, the present invention utilizes a toroidal vortex flow. Such flows are neither mentioned nor contemplated by Reinhall. Also in distinction, the present invention uses a screw to catch and compress the attracted debris.  
           [0021]    Namdari U.S. Pat. No. 4,443,997 teaches an apparatus for leaf and grass vacuuming and compaction in a bag. The apparatus is usable independently, but is shown in the reference shown mounted on a wheeled carriage of a power lawnmower on which are mounted a push-handle, a gasoline engine, a lawnmower blade drivable by the engine, a vacuum chamber enclosing a fan drivable by the engine, and a receptacle bag above which is mounted a compactor having a reciprocating ram. The ram is driven either by a belt-drive from the engine, or by an electric motor energized from the engine generator or starter battery, or by a hydraulic pump/motor system driven by the engine. A pick-up hose is attached to the vacuum chamber inlet and a discharge hose is attached to the vacuum chamber outlet whereby material such as leaves and grass clippings entering the pick-up hose are expelled through the discharge hose into the removable bag. As the material fills the bag, the compactor is actuated to cause the movable ram member to repeatedly descend into the bag to compact the material therein. The compactor also includes a fan or centrifuge for blowing material off the ram and into the bag after the ram returns above the bag opening. The pick-up hose is selectively connectable to the lawnmower to pick up material as the lawn is being mowed or as the carriage is moved or manually while the carriage is stationary and the mower is disengaged. While Namdari is directed to an apparatus for the collection and compaction of debris, it does not utilize even remotely similar attraction and compression means.  
           [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 lowefficiency 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. The type of flow geometry taught by Dyson is entirely distinct from that described herein. Furthermore, the energy required to sustain this flow is much greater than that of the present invention.  
           [0023]    Holtom U.S. Pat. No. 5,960,710 teaches a refuse compactor having a storage/compaction chamber, a lid, and a compaction blade. The compaction blade is driven by a cylinder that is attached to either the lid or the chamber. The device is meant for use as a refuse collector/compactor in areas too densely populated to allow for a conventional garbage truck to pass through. While Holtom teaches an apparatus for compaction of refuse, it does not teach any means of collecting the refuse, and further, utilizes completely different means of compaction.  
           [0024]    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. 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. 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.  
           [0025]    Thus, there is a clear and long felt need in the art for a by light weight, efficient and quiet debris collection apparatus.  
         SUMMARY OF THE INVENTION  
         [0026]    The present invention was developed from the applicant&#39;s prior inventions regarding toroidal vortex attractors (as disclosed, for example, in inventor&#39;s application Ser. No. 09/829,416 entitled “Toroidal and Compound Vortex Attractor,” which is herein incorporated by reference) and toroidal vortex bagless vacuum cleaners (as disclosed, for example, in inventor&#39;s application Ser. No. 09/835,084 entitled “Toroidal Vortex Bagless Vacuum Cleaner,” which is herein incorporated by reference).  
           [0027]    Described herein are embodiments that deal with 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 would greatly harm efficiency. The cross section of the nozzle need not be circular, in fact, a rectangular embodiment is disclosed therein, and other embodiments are possible.  
           [0028]    A complete toroidal vortex bagless vacuum cleaner is also disclosed. The air mover is a centrifugal pump, much like those used in certain toroidal vortex attractor embodiments. Air leaving the centrifugal pump blades is spinning rapidly so that dust and dirt are thrown to the sidewalls of the casing. Ultimately, dirt is deposited in a centrifugal dirt separation area. The air then turns upwards over a dirt barrier and down the air delivery duct. At this point, the air is quite clean except for the finest particulates that do not deposit in the centrifugal dirt separation area. These particulates circulate through the system repeatedly until they are eventually deposited. 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.  
           [0029]    Also disclosed is a complete debris attraction system with collection apparatus. A conventional toroidal vortex vacuum system is modified by the addition of a feed screw that assists in the depositing of collected debris into an isolated area. The device can also include removable collection means, such as a garbage bag or bucket, to hold the collected debris.  
           [0030]    Unlike other vacuum cleaners that employ centrifugal dust separation (e.g., the “cyclone” types discussed above), the present invention spins the air around at the blade speed of the centrifugal pump. Thus, the system acts like a high speed centrifuge capable of removing very small particles from the airflow, and no vacuum bag or HEPA filter is required. However, an embodiment is taught that utilizes a bag (but not a conventional vacuum bag, i.e., those that act as a filter) to assist in the collection of large amounts of debris.  
           [0031]    One of the main features of the present invention is the inherent low power consumption. There are no losses that must exist when vacuum bags or HEPA filters are utilized. These devices restrict the airflow, thus requiring greater power to maintain a proper flow rate. The majority of the power saving, however, comes from the closed air system in which energy supplied by the pump is not lost as air is expelled into the atmosphere, but is retained in the system. The design is expected to be practically maintenance free.  
           [0032]    Thus, it is an object of the present invention to utilize toroidal vortices in a vacuum cleaner application.  
           [0033]    It is a further object of the present invention to provide toroidal vortex vacuum cleaner nozzles.  
           [0034]    It is yet another object of the present invention to provide a complete toroidal vortex vacuum cleaner system.  
           [0035]    Additionally, it is an object of the present invention to provide an efficient vacuum cleaner.  
           [0036]    Furthermore, it is an object of the present invention to provide a quiet vacuum cleaner.  
           [0037]    It is a further object of the present invention to provide a light weight vacuum cleaner.  
           [0038]    In addition, it is an object of the present invention to provide a low-maintenance vacuum cleaner.  
           [0039]    It is a further object of the present invention to provide a vacuum cleaner that does not require the use of filters.  
           [0040]    It is a further object of the present invention to provide an apparatus that attracts debris using a toroidal vortex, and deposits it into a bag or bucket.  
           [0041]    It is an additional object of the present invention to provide an apparatus that attracts debris using a toroidal vortex, and with the help of a screw, deposits it into a bag or bucket.  
           [0042]    It is a further object of the present invention to provide an apparatus that attracts debris using a toroidal vortex, and deposits it into a removable bag or bucket.  
           [0043]    It is an additional object of the present invention to provide an apparatus that attracts debris using a toroidal vortex, and with the help of a screw, deposits it into a removable bag or bucket.  
           [0044]    It is an additional object of the present invention to provide an improved leaf collector.  
           [0045]    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  
       [0046]    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.  
         [0047]    For a more complete understanding of the present invention, reference is now made to the following drawings in which:  
         [0048]    [0048]FIG. 1, already discussed, depicts the establishment of the coanda effect (PRIOR ART);  
         [0049]    [0049]FIG. 2, already discussed, depicts the dynamics of the coanda effect (PRIOR ART);  
         [0050]    [0050]FIG. 3, already discussed, depicts the coanda effect on a spherical surface with both radial and tangential components of motion (PRIOR ART);  
         [0051]    [0051]FIG. 4, already discussed, depicts a coanda vacuum cleaner nozzle (PRIOR ART);  
         [0052]    [0052]FIG. 5, already discussed, depicts the undesirable airflow in a coanda vacuum cleaner nozzle (PRIOR ART);  
         [0053]    [0053]FIG. 6, already discussed, depicts a side and bottom view of an annular coanda vacuum cleaner nozzle (PRIOR ART);  
         [0054]    [0054]FIG. 7 depicts a toroidal vortex, shown sliced in half;  
         [0055]    [0055]FIG. 8 graphically depicts the pressure distribution across the toroidal vortex of FIG. 7;  
         [0056]    [0056]FIG. 9 depicts a toroidal vortex attractor;  
         [0057]    [0057]FIG. 10 depicts a cross section of a concentric vacuum system;  
         [0058]    [0058]FIG. 11 depicts a concentric vacuum system with air being sucked up the center and blown down the sides;  
         [0059]    [0059]FIG. 12 depicts the dynamics of the re-entrant airflow of the system of FIG. 11;  
         [0060]    [0060]FIG. 13 depicts a cross section of an exemplary toroidal vortex vacuum cleaner nozzle in accordance with the present invention;  
         [0061]    [0061]FIG. 14 depicts a perspective view of an exemplary rectangular toroidal vortex vacuum cleaner nozzle in accordance with the present invention; and  
         [0062]    [0062]FIG. 15 depicts a cross section of an exemplary toroidal vortex bagless vacuum cleaner having an exemplary circular plan form.  
         [0063]    [0063]FIG. 16 depicts a cross section of an embodiment of a toroidal vortex debris collection apparatus comprising improved collection means. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0064]    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.  
         [0065]    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.  
         [0066]    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 difference across the stream tube, the pressure being higher on the outside than the inside. This pressure difference Δp is, by momentum theory, Δp=ρV 2 /R where ρ 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.  
         [0067]    [0067]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.  
         [0068]    The present invention was developed from a toroidal vortex attractor previously described by the inventor. 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.  
         [0069]    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 ρV 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 ρ 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  (ρV 2 /R).  
         [0070]    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.  
         [0071]    The new 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. Dust collection is not perfect and so air returning to the surface is dust laden. This air must, of course, contact the surface in order to pick up more dust but must not be allowed to escape into the surrounding atmosphere. It is not sufficient to design the cleaner to ensure essentially sealed operation while operating adjacent to a surface being cleaned, it must also remain sealed when away from a surface to prevent fine dust particles from re-entering the surrounding air.  
         [0072]    Another reason for maintaining sealed operation when away from the surface is to prevent the vacuum cleaner nozzle from blowing surface dust around when it is held at a distance from the surface.  
         [0073]    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 walls  1002  (which form inner tube  1003 ) 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.  
         [0074]    [0074]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 .  
         [0075]    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 ρV 2 /R, where ρ 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.  
         [0076]    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.  
         [0077]    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.  
         [0078]    [0078]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 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. These 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  1516 .  
         [0079]    [0079]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.  
         [0080]    This embodiment has air mixed with dirt and dust passing through the centrifugal impeller vanes. If such an arrangement is considered undesirable, 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 air pump.  
         [0081]    [0081]FIG. 16 depicts a cross-section of a toroidal vortex debris collection apparatus having improved collection means. The apparatus consists of a motor  1601  coupled via belt  1602  to pulley  1603 . Pulley  1603  is coupled to screw  1604  such that the rotation of pulley  1603  induces the rotation of screw  1604 . Motor  1601  is also coupled to impeller  1610 , which, as has been described, generally comprises a plurality of vanes. Impeller  1610  and screw  1604  are together encased in a structure consisting generally of leaf collector ring  1607 , outer tube  1608 , coaxially disposed inner tube  1609 , and container  1605 . Container  1605  can be removable or fixed, and further can be lined with or consist of a garbage bag  1606 . Airflow through the outer tube  1608 , the inner tube  1609  and the toroidal vortex nozzle  1612  (generally comprising flow straightening vanes (not shown) and inner fairing  1613 ) are as described previously in FIGS. 12, 13 and  14 . Air leaving the impeller  1610  blades is spinning rapidly so that debris (as an example, leaves  1611  are depicted) is thrown to the sidewall of the collector ring  1607  and eventually is thrown toward the compactor screw  1604 . The circulating airflow in the collector ring  1607  creates a greater pressure in the container  1605  than exists in the collector ring  1607 . This pressure differential maintains the circular flow of air in the collector ring  1607  without preventing the debris from being ejected into the container  1605 . The compactor screw  1604  ensures that debris thrown outward by the impeller  1610  is pushed down into the container  1605 . This allows for easy collection of the debris, and also prevents its re-circulation into the airflow. The air that traveled through the collector ring  1607  turns upwards over a barrier  1614  and down a certain portion of the outer ring  1608 . At this point, the air is substantially clean except for fine particulates that fail to be deposited. These circulate through the system repeatedly until they are finally deposited out. The system operates below atmospheric pressure so that air laden with fine particulates is constrained within the system and cannot escape into the surrounding atmosphere. After use, the debris that has been collected in the container  1605  can be emptied in several ways. If a removable container is used (as depicted  1605 ), it can simply be detached and emptied. Further, the container can be lined with a garbage bag  1606 . Alternatively, a fixed container could be used that utilizes a door (not shown) that allows for removal of the collected debris.  
         [0082]    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.