Abstract:
A cyclonic separation apparatus comprising at least two series connected separation stages and a receptacle for collecting material separated by the separation stages, is described. The first stage comprises a first cyclone separator and the second stage comprises a plurality of parallel connected second cyclone separators. The first and second separation stages are connected by at least one transfer duct which extends through the receptacle and transfers fluid that has been partly cleaned by the first separation stage, to the second separation stage.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a cyclone separation apparatus. 
         [0003]    2. Related Background Art 
         [0004]    Cyclonic separation apparatus are well known apparatus for removing particles from a gas flow without the use of filters. Cyclone separators have found utility in the field of vacuum cleaners to separate dirt and dust from the airflow. It is well known that the separation efficiency of cyclonic separators is dependent upon the force which is applied to the particles in the airflow, in accordance with the following formula: 
         [0000]        F= 2 mv   2   /d,    
         [0000]    where
 
F=the force applied to the particles;
 
m=the mass of the particle;
 
v=the flow velocity; and,
 
d=the diameter of the cyclonic air flow
 
         [0005]    Thus, it is evident that the separation efficiency is inversely proportional to the diameter of the cyclone chamber, such that smaller diameter cyclones are more suited to separating lighter particles than larger diameter cyclones. Accordingly, it is well known for vacuum cleaners to incorporate a first upstream separation stage, comprising a relatively large diameter cyclone and a plurality of parallel connected downstream cyclones having a smaller diameter. In use, the upstream cyclone separates coarse dirt and dust from the airflow, whereas the downstream cyclones separate the finer dirt and dust. 
         [0006]    Cyclonic separators for vacuum cleaners comprising two stages of separation have been proposed. U.S. Pat. No. 2,171,248 discloses an arrangement whereby a high efficiency downstream cyclone is nested co-axially inside a low efficiency upstream cyclone. The respective cyclones discharge their separated solid material into a removable receptacle comprising a central chamber for the material discharged from the downstream cyclonic chamber, and an annular chamber from material discharged from the upstream cyclonic chamber. 
         [0007]    EP1674021 discloses a two stage cyclonic separator for a vacuum cleaner comprising a low efficiency upstream cyclone separator, followed by an array of parallel-connected mini cyclones disposed in an annular chamber, which surrounds the first cyclonic chamber. Partly cleaned air that exits first stage passes upwards by way of an axially orientated central outlet and is fed into the high efficiency cyclones. However, the complex alignment of the flow path between the two stages of the separation gives rise to a pressure drop. 
         [0008]    DE 202006017010 discloses a two stage cyclonic separator for a vacuum cleaner again comprising a low efficiency cyclone separator followed by an array of parallel connected high efficiency cyclone separators situated above the first stage. Partly cleaned air leaving the first stage is ducted upwards through an annual cavity between the high efficiency cyclones and the outer wall of the separator unit and is then ducted regularly inwards to the respective high efficiency cyclones. This arrangement gives rise to less of a pressure drop. However, in situations where the high efficiency cyclones are not disposed equidistantly on the periphery of the separator unit, the cyclones can become unevenly loaded with respect to the dust laden air, and can result in the blocking of some cyclones. 
       SUMMARY OF THE INVENTION 
       [0009]    In accordance with the present invention, a cyclonic separation apparatus which alleviates the above-mentioned problem comprises a first separation stage and second separation stage,
       the first stage comprising a first cyclone separator, the second stage comprising a plurality of parallel connected second cyclone separators, the apparatus further comprising a receptacle for collecting material separated by the second cyclone separators,   the first and second separation stages arranged in fluid communication by at least one transfer duct which transfers fluid that has been partly cleaned by the first separation stage, to the second separation stage,   wherein the at least one transfer duct extends through the receptacle.       
 
         [0013]    Preferably, the at least one transfer duct extends substantially parallel to the rotational axis of the cyclone separators of the first and second separation stages. 
         [0014]    Preferably, the second cyclone separators are arranged in plurality of groups. 
         [0015]    The cyclonic separation apparatus preferably comprises a plurality of transfer ducts. Each transfer duct preferably transfers fluid to one group of the plurality of groups of second cyclone separators. 
         [0016]    Preferably, each group of second cyclone separators are arranged equidistantly from the downstream end of the respective transfer duct to avoid uneven loading of the second cyclone separators of the group. 
         [0017]    Preferably, the receptacle is disposed partly above the first separation stage. 
         [0018]    Preferably, the cyclonic separation apparatus comprises a collection chamber disposed axially within the first separation stage, for collecting material discharged by the first and second cyclone separators. 
         [0019]    Preferably, the receptacle is funnel shaped and discharges material separated by the second separation stage into the collection chamber. 
         [0020]    Preferably, the first separation stage and second separation stage are connected in series. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings in which: 
           [0022]      FIG. 1  is a longitudinal-sectional view through the separation portion of a 2-stage cyclonic vacuum cleaner in accordance with the present invention; 
           [0023]      FIG. 2  is a perspective view of the top of the first stage of the cyclonic vacuum cleaner of  FIG. 1 , when the second stage is removed therefrom; 
           [0024]      FIG. 3  is a perspective view of the bottom of the second stage of the cyclonic vacuum cleaner of  FIG. 1 ; 
           [0025]      FIG. 4  is a perspective view of the top of the second stage of the cyclonic vacuum cleaner of  FIG. 1 , when fitted to the first stage; and 
           [0026]      FIG. 5  is a perspective view of the top of the second stage of the cyclonic vacuum cleaner of  FIG. 1 , when fitted to the first stage and when a cover portion is fitted thereto. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    Referring to  FIG. 1  of the drawings, there is shown the separation portion of an upright vacuum cleaner. The separation portion is mounted to a chassis (not shown) incorporating a handle, the lower end of the chassis being pivotally interconnected to a wheeled floor-cleaning head incorporating a rotatable agitator brush. 
         [0028]    The separation portion comprises a generally cylindrical upright housing, which houses the first and second separation stages  10 ,  11  at its lower and upper ends respectively, the second stage  11  being fluidly connected downstream of the first stage  10 . 
         [0029]    The first stage  10  comprises a tubular side wall  12  defining a circular-section cyclone chamber  13 . The lower end of the tubular side wall  12  is provided with a closure  14 , which can be opened to allow separated dirt and dust to be emptied from the chamber  13 . 
         [0030]    An inlet duct  15  for carrying dirt and dust laden air from the floor cleaning head extends tangentially into the upper end of the tubular side wall  12  of the first stage  10 . An elongate tubular container  16  extends through the cyclone chamber  13  along the centre axis thereof. The lower end of the container  16  is sealingly closed by a disk  17 , which is mounted to the closure  14  such that the lower end of the container  16  is also opened when the closure  14  is opened. The upper end of the container  16  communicates with an outlet of the second stage  11  from which the separated fine dust is discharged. 
         [0031]    The upper end of the first stage  10  is closed by an annular end wall  18  having a central aperture  19 , through which the elongate container  16  extends. A perforated shroud  20  depends from the upper end wall into the cyclone chamber  13 , the lower end of the shroud being sealed against the external surface of the tubular container  16 . 
         [0032]    Referring also to  FIG. 2  of the drawings, a circular manifold  21  is sealingly mounted on top of the upper end wall  18  of the first stage  10 . The manifold  21  comprises six upstanding tubular projections  22 , which are disposed at equally spaced circumferential positions on a concentric circular line on the manifold  21 . The lower end of the projections  22  fluidly communicate with the space inside the shroud  22  through the aperture  19  in the upper end wall  18  of the first stage  10 . 
         [0033]    Referring to  FIG. 3  of the drawings, the second stage  11  comprises a cylindrical main body  23 , which is fitted to the upper end of the first stage  10 , the manifold projections  22  extending into corresponding apertures  24  which extend through the body  23  between opposite sides thereof. Each aperture  24  is surrounded by six cyclone separators  25  which extend axially therewith and which are equally spaced around the circumference of the apertures  24 . The cyclone separators  25  are contained within hexagonal tubular boundary walls  26 . Each cyclone separator  25  comprises a frusto-conical side wall  27  (as shown in  FIG. 1  of the drawings), which tapers inwardly to a cone opening at the lower end of the body  23 . 
         [0034]    Referring to  FIG. 4  of the drawings, the cyclone separators  25  are arranged in six groups, each group e.g. A (as denoted by the shaded area in  FIG. 4 ) comprises five cyclone separators  25  arranged about a respective aperture  24  and disposed in an arc, which is centred on the central axis of the respective aperture  24 . It will be appreciated that one of the six cyclone separators  25  surrounding each aperture  24  belongs to an adjacent group of separators. 
         [0035]    Five channels  28  extend radially outwardly from the upper end of each aperture  24  in the upper surface of body  23 . The channels  28  lead tangentially into the upper ends of respective cyclone separators  25  of the group of separators associated with that aperture. 
         [0036]    The lower ends of the frusto-conical walls  27  of the cyclone separators  25  terminate above the level of their respective hexagonal tubular boundary walls  26 , in order to prevent any cyclonic air flow from being carried over to below the bottom surface of the body  23 . As shown in  FIG. 2 , baffles  40  supported by stems  41  extending from the upper surface of the manifold  21  may be positioned inside each hexagonal tubular boundary wall  26 , just below the opening of each cone. The bottom end of the hexagonal boundary walls  26  open into a gallery  29  formed below the body  23  and above the manifold  21 . The floor of the gallery  29  comprises an opening at its centre which is connected to the upper end of the elongate tubular container that extends through the cyclone chamber  13  of the first stage  10 . 
         [0037]    Referring to  FIG. 5  of the drawings, an apertured cover plate  30  is fitted to the upper surface of the body  23 . The apertures  31  in the plates  30  are disposed axially above respective cyclone separators  25 , the lower surface of the cover plate  30  comprising tubular projections  32  which extend from the apertures  31  into the upper ends of the cyclone separators to form so-called vortex finders. 
         [0038]    A filter housing  33  is disposed above the second stage  11  and, in use, a vacuum is applied to the filter housing  33  to cause an airflow through the first and second stages  10 ,  11  from the dirty air inlet  15 . The tangential orientation of the inlet  15  with respect to the wall  12  creates a cyclonic air flow inside the chamber  13  of the first stage  10 , whereby air spirals downwardly around the chamber  13  towards its lower end. As the air flows downwards, the volume of air in the spiral flow is constantly being diminished by virtue of it having been drawn radially through the perforated shroud  20  towards the second stage  11 . 
         [0039]    As the air swirls inside the chamber  13 , larger (denser) particles in the rotating airflow have too much inertia to follow the tight curve of the airflow and strike the outside wall  12  of the chamber, moving then to the bottom of the cyclone where they are deposited in the lower region of the chamber  13 . 
         [0040]    The air flowing through the perforated shroud  20  is divided equally into six separate parallel paths along the respective tubular projections  22  of the manifold  21 . The six separate air flows then divide below the lower surface of the cover plate  31  into five further air flows along the respective channels  28 . The channels  28  direct the airflows tangentially into the upper end of respective cyclone separators  25  to create a cyclonic airflow therein. The airflows spiral downwardly around the frusto-conical walls  27  of the separators  25  towards their lower ends. As the air flows downwards, the volume of air in the spiral flow is constantly being diminished, by virtue it having been drawn radially inwardly and axially upwardly through the vortex finders  32 . 
         [0041]    Any light particles of dust remaining in the airflow from the first stage  10  have too much inertia to follow the very tight curve of the airflow and strike the frusto-conical walls  27  of the separators  25 , the dust being carried downwardly through the cone openings and into the gallery  29 . The fine dust then falls into the elongate tubular container  16 . It will be appreciated that the dust separated by both the first and second stages  10 ,  11  can be emptied by removing the closure  14 . 
         [0042]    A vacuum cleaner in accordance with the present invention is relatively simple in construction, yet has a substantially improved separation efficiency by enabling large numbers of high-efficiency cyclones to be compactly accommodated. 
         [0043]    While the preferred embodiment of the invention has been shown and described, it will be understood by those skilled in the art that changes of modifications may be made thereto without departing from the true spirit and scope of the invention.