Abstract:
Apparatus for separating particulate matter from an airstream includes a housing including an intake for particulates-containing air and an exhaust for cleaned air, in which the apparatus includes a primary vortex generator in the intake air and the housing includes a separation zone which includes primary and secondary separation chambers each associated with respective particulates collector and including an interconnector adapted to generate a secondary vortex in the secondary separation chamber.

Description:
This is a continuation of International Application No. PCT/GB99/00507, having a filing date of Feb. 18, 1999, now abandoned, which is a continuation of Great Britain application no. GB9803539.7, having a filing date of Feb. 19, 1998, now abandoned. 

   TECHNICAL FIELD 
   This invention relates to a cleaning apparatus of the type for separating particulate matter from a fluid stream such as an airstream, which are used, for example, in so-called bagless vacuum cleaners. 
   BACKGROUND OF THE INVENTION 
   Patent Cooperation Treaty Publication WO 96/11047 describes apparatus for the removal of particulate material suspended in a gas stream, in which rotary motion is generated in the stream which is then passed to an expansion chamber where the gases are decelerated to enable particulates to fall out of suspension and to be collected in a collection chamber. It has been found that, whereas such apparatus deals effectively with large and medium-sized particles, small particles tend to remain entrained in the gas stream and are exhausted to the atmosphere. Clearly, where the apparatus is incorporated in a suction cleaner for indoor use, the result is that the small particulate matter tends to be recycled in the room being cleaned and, having left the apparatus in the exhaust stream, it eventually settles as dust on the furniture or the floor. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the invention, there is provided apparatus for separating particulate matter from a fluid stream, the apparatus comprising a housing including means for intake of particulate-containing fluid and means for exhaust of cleaned fluid. The apparatus further includes means for generating a primary vortex in the intake fluid and the housing comprises a separation zone that includes primary and secondary separation chambers each associated with respective particulate collection means and including interconnection means adapted to generate a secondary vortex in the secondary separation chamber. 
   Preferably, the fluid is air although a liquid stream could be cleared of particulates in the inventive apparatus. For convenience, the term “airstream” will be used throughout the remainder of this specification and is intended to include other fluids, such as, for example, liquids. 
   In operation, heavier particulates pass through the interconnection means from the primary to the secondary chamber and are separated from the airstream therein, whereas lighter particulates are retained within the primary chamber. The primary chamber and secondary chambers are preferably peripherally interconnected and the primary chamber preferably includes a parallel-sided or cylindrical portion and a cyclone portion. The cylindrical portion accommodates the interconnection means and may be disposed relatively upstream of and co-axial with the cyclone portion, which is preferably tapered inwardly in the downstream direction. The secondary chamber is preferably cylindrical and peripherally connected to the primary chamber in the parallel-sided portion, whereby the respective axes of the primary and secondary chambers are parallel. Dirt-laden air entering the separation zone of the primary chamber is constrained to follow a spiral pathway around and progressively along the axis thereof, optionally under the influence of vanes or other deflection means disposed internally of the primary chamber on the roof or wall thereof. Particulate material entrained therein is forced under the influence of centripetal force towards the wall of the chamber, the larger and denser particles, being more influenced by centripetal force than the smaller and less dense particles, are urged to follow the wall more closely. As the denser material moves around the periphery of the primary chamber, it reaches the intercommunicating connection with the secondary chamber and is urged to enter therein by centripetal force. The secondary vortex created therein, preferably in the opposite rotary sense to the primary vortex, maintains the particles in suspension and carries them to a collection chamber from where they may be removed from time to time. An inwardly-extending annular flange may be provided between the cylindrical and cyclone portions to improve discrimination between heavier and lighter particulates. Optionally, a tertiary or further separation chamber is interconnected with the secondary chamber and provides a corresponding vortex therein. 
   The lighter material remaining in suspension in the primary chamber is moved spirally to the tapered cyclone portion thereof where it becomes progressively accelerated as the diameter reduces. On reaching the narrowest part, it is ejected from the airstream which then passes, substantially clear of particulate matter, to the exhaust means. The fact that the air in the cyclone part of the apparatus has had the denser particles already removed therefrom results in a lower weight loading of the airstream. With the reduced weight loading, the airstream attains greater velocities. This, in turn, results in more effective removal of smaller particles than would be expected with a cyclone alone, without the secondary chamber, and the apparatus as a whole thereby has an enhanced ability to handle a wider range of material with greater efficiency and at higher loading rates. 
   The interconnection means may be adapted to generate a secondary vortex in the secondary chamber by means of airstream current-deflecting elements in the region of the interconnection between the chambers. Preferably, the current-deflecting elements establish a zone of spatial separation between the respective vortices whereby the vortices do not create or at least minimize any turbulence between them while still allowing particulate matter adjacent the wall of the primary chamber to pass unimpeded into the secondary chamber. The current-deflecting elements may comprise a chamber wall portion on at least one side of the intercommunication aperture that is deformed to increase its radius of curvature towards a tangential position. Preferably, the primary chamber wall on the upstream side of the aperture is so deformed. Even more preferably both the primary and secondary chamber walls on each side of the aperture are so deformed so as to provide an interconnecting neck that is generally chordal to both chambers. In these configurations, the deformed wall of the primary chamber urges the heavier particles to move outwardly of the radius of curvature of the primary chamber. Also, the deformed wall of the secondary chamber acts to separate the primary airstream to create a secondary vortex in the secondary chamber and preferably in the opposite direction to that of the primary vortex. 
   In the separation zone, the primary separation chamber may contain a cyclone separator, whereby the outer wall of the primary chamber and the wall of the cyclone separator define an annular chamber in peripheral communication with the secondary chamber. The cyclone separator may be arranged for either upward or downward swirling or helical motion of the airstream, with the particulate load thereof being either discharged upwardly so that it settles under gravity in a collection chamber formed about the upper portion of the cyclone separator, or discharged downwardly into a collection vessel disposed below the cyclone separator. 
   The means for generating a primary vortex in the particulate-containing airstream entering the housing may comprise an array of vanes upstream of the housing, individual vanes being optionally spaced apart axially to prevent clogging by large particulates or filamentary material, or an off-center, for example, tangential, inlet pipe. An auxiliary air intake may provide a laminar film or layer of dirt-free air at the periphery of the primary chamber across or at least into the interconnection means, to improve retention of lighter particulates in the primary chamber while not substantially impeding transfer of heavier particulates to the secondary chamber. The auxiliary air intake may have an entry orifice in the primary chamber immediately adjacent to or spaced apart from the intake means for particulates-containing air and the auxiliary airstream may be induced by the flow of particulates-containing air across the entry orifice or may be supplied under positive external pressure, for example by an auxiliary pump. 
   The primary separation chamber may comprise two or more cylindrical portions each with an associated secondary separation chamber, adjacent cylindrical portions being axially connected together by cyclone portions of progressively smaller diameter in the downstream direction. 

   
     DESCRIPTION OF THE FIGURES 
     Embodiments of the invention will now be described by way of example with reference to the accompanying schematic drawings, of which: 
       FIG. 1  is a side view of one embodiment of a separation apparatus; 
       FIG. 2  is a plan view showing the internal parts of the apparatus of  FIG. 1 ; 
       FIG. 3  is a side view of another embodiment of separation apparatus; 
       FIG. 4  is a side view of an alternative embodiment to that shown in  FIG. 3 ; 
       FIG. 5  is a side view of a further alternative embodiment in which the primary chamber is contained within a larger chamber; 
       FIG. 6  shows in plan view a variation of  FIG. 5  where the larger chamber constitutes the secondary chamber; 
       FIG. 7  shows in plan view another embodiment of  FIG. 5  where the larger chamber contains the secondary chamber; 
       FIG. 8  shows in plan view the use of a secondary air inlet to enhance the separation of larger particulates from the airstream; and 
       FIG. 9  shows in side view an embodiment in which the primary chamber has multiple cylindrical portions and cyclone portions. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1 and 2 , the apparatus consists of a primary chamber  11  and a secondary chamber  12  joined by a generally chordal interconnection neck  13 , the walls of which are constituted by respective wall portions of the primary and secondary chamber being tangentially deformed and joined to the other chamber. The primary chamber  11  has an upper cylindrical portion  14  and a lower co-axial cyclone separator  15 . An inner flange  16  is disposed between the upper and lower parts; the flange has an upwardly-turned inner peripheral lip  17 . The flange  16  is not essential. 
   A tangential inlet  18  is provided at the upper end and also an axial outlet  19  for exhaust air; an electric motor (not shown) draws air through the apparatus, or alternatively may blow air through under positive pressure. 
   Removable collection vessels  20 ,  21  are provided to the cyclone separator and secondary separation chamber respectively. As shown by the arrows, inlet air is constrained by the outlet  19  to follow a helical anticlockwise pathway around the inner wall of the cylinder portion of the primary chamber, heavier particulates, represented by the dotted arrow of  FIG. 2 , being carried through the neck  13  into the secondary chamber, where they follow a helical clockwise pathway. The heavier particles eventually fall by gravity into collection vessel  21 ; the lighter particles remain entrained in the primary chamber and are separated from the airstream in the cyclone separator, being collected in collection vessel  20 . The neck  13  not only provides an access pathway for heavier particulates but also provides a demarcation region between the respective vortices, to minimize generation of turbulence. The flange  16  assists in ensuring that heavier particulates enter the secondary chamber. 
   The arrangements illustrated in  FIGS. 3 and 4  have the cyclone separator  35 / 45  mounted within the cylindrical portion  34 / 44 . In  FIG. 3 , the inlet  38  is at the upper end of the apparatus, the cyclone separator  35  is arranged for upward flow and the helical flow in the cylindrical portion  34  is downwards, exhaust air passing through outlet  37 , whereas in  FIG. 4  the inlet  48  is at the lower end of the apparatus, the helical flow in the cylindrical portion  44  is upwards, the cyclone separator  45  is arranged for downward flow and the exhaust air passes through outlet  47 . Collection vessels for lighter particulates are identified by reference numerals  30 / 40  and for heavier particulates by reference numerals  31 / 41 ; secondary chambers are identified by reference numerals  32 / 42 . 
     FIG. 5  illustrates an alternative arrangement in which the primary separation chamber  51  and associated cyclone  52  are arranged within a larger chamber  53 . The respective chambers are each configured to have associated collection vessels  54 ,  55  for lighter ( 54 ) and heavier ( 55 ) particulates, respectively. 
   In  FIG. 6 , the larger chamber constitutes the secondary chamber and the vortex therein is in the same direction as the primary vortex, as shown by the dashed arrow. The wall of the primary chamber immediately upstream of the interconnection aperture is deformed tangentially at  61  into the secondary chamber to allow the vortex therein to be generated with minimum turbulence. In  FIG. 7 , the secondary chamber  71  is formed wholly within the larger chamber and the vortex therein is in the opposite rotational direction to the primary vortex. 
     FIG. 8  illustrates a secondary air inlet through pipe or channel  81  to provide a laminar film of clean air at the wall of the primary chamber  82  and continuing to the interconnection neck  83  linking the primary chamber with the secondary chamber  84 , to maintain the lighter particulates in the primary chamber while not impeding passage of heavier particulates through the neck. The secondary airstream can be supplied from a pump or may be drawn in by the dirt-laden airstream in channel  85  passing through orifice  86  and across the orifice  87  of pipe  81 . The secondary airstream flowrate may be restricted by means of adjustment of orifice sizes, to provide selective separation of material entering the apparatus. The orifices  86  and  87  may optionally be circumferentially spaced apart, as an alternative to the arrangement illustrated. 
     FIG. 9  shows multiple primary chambers  91 ,  92 ,  93  axially spaced apart and connected by respective cyclones  94 ,  95 ,  96 , each chamber having an associated respective secondary chamber  97 ,  98 ,  99  and cyclone  96  terminating in collection chamber  100 . Shown in cross-section, inlets  101  for dirt-laden air and  102  for secondary clean air are provided in primary chamber  91  and exhaust air passes out through duct  103 . Further inlets for secondary clean air may optionally be provided for each of primary chambers  92  and/or  93 . Internal annular upturned flanges  104 ,  105 ,  106  are provided to enhance passage of heavier particulates into the respective secondary chamber. In operation, the larger or more dense particulates are separated from primary chamber  91  and collected by secondary chamber  97  and material not separated is concentrated in cyclone  94  before entering primary chamber  92  of smaller diameter than primary chamber  91  but otherwise similar. Centripetal forces are greater in chamber  92 , whereby the larger particulates therein are separated by secondary chamber  98  and unseparated material passes to primary chamber  93  through cyclone  95  until, ultimately, the lightest particles are separated in cyclone  96  and collected in collection chamber  100 . 
   In all embodiments illustrated, clean exhaust air passes by reverse flow through the center of the apparatus, and there is no net flow of fluid through the secondary chamber or chambers. 
   The present invention establishes a significant advance over previously known cleaning devices and methods for cleaning a fluid stream, and the advance is achieved with reduced cost, simplicity of fabrication, and ease of use. 
   Numerous modifications and variations of the preferred embodiments disclosed herein will be apparent to those skilled in the art. Accordingly, even though only few variations of the present invention are described herein, it is to be understood that the practice of additional modifications and variations and the equivalents thereof, are within the spirit and scope of the invention as defined in the following claims.