Patent Publication Number: US-6706095-B2

Title: Cyclonic separating apparatus

Description:
The invention relates to cyclonic separating apparatus and to a method of separating dirt from dirt-laden air. Particularly, but not exclusively, the invention relates to cyclonic separating apparatus suitable for use in a vacuum cleaner. 
     Cyclonic separating apparatus is well known. In such apparatus, the dirt-laden air is introduced to the interior of a cyclone body in a tangential manner. The air follows a helical path around the interior surface of the cyclone body so that centrifugal forces act on the entrained dirt. At the bottom of the cyclone body, the airflow reverses its direction of travel parallel to the axis of the cyclone body and the dirt is separated from the main airflow. The separated dirt collects at the bottom of the cyclone body whilst the cleaned air exits the apparatus via a centrally located outlet at the top of the cyclone body. Examples of the application of this type of separating apparatus to domestic vacuum cleaners are shown in EP 0 042 723, U.S. Pat. Nos. 5,160,356 and 5,078,761. 
     One disadvantage of this type of arrangement is that, as the amount of collected dirt increases, the risk of that collected dirt being re-entrained into the airflow increases. Some attempts have been made to alleviate this problem by providing a dirt collection chamber, separate from the cyclone body, into which the collected dirt is transferred and in which it is allowed to accumulate. The cylinder vacuum cleaner manufactured by Electrolux and marketed under the name “CYCLONE POWER BAGLESS HOME CLEANING SYSTEM” (Model Number Z58102T) incorporates such a feature. A similar arrangement is shown in TWO 9611047. In theory, the collected dirt is kept separate from the main airflow which reduces the risk of re-entrainment so that larger volumes of separated dirt can be collected before the apparatus requires to be emptied. However, because the dirt-collection chamber is closed in all areas except at the inlet thereto, any air which enters the dirt-collection chamber is forced to follow a circuitous path and must exit the dirt-collection chamber via the inlet. This leads to a not insignificant amount of turbulence inside the dirt-collection chamber which can lead to previously separated dirt being carried back into the mainstream airflow by the returning air. Another disadvantage of the turbulent conditions existing within the closed dirt-collection chamber is that the separated dirt is carried to many different parts of the dirt-collection chamber. This makes the emptying of the dirt-collection chamber more complicated especially if it is desired to make use of emptying means which allow the user to avoid being exposed to the contents of the dirt-collection chamber. 
     It is an object of the present invention to provide cyclonic separating apparatus in which the risk of re-entrainment of separated dirt is reduced. It is a further object to provide cyclonic separating apparatus in which the capacity of the apparatus to collect dirt is improved. It is a still further object to provide cyclonic separating apparatus in which the risk of re-entrainment of separated dirt is reduced and the capacity of the apparatus to collect dirt is simultaneously increased. It is a still further object of the invention to provide cyclonic separating apparatus which can be easily and conveniently emptied in a manner which allows the user to avoid being exposed to the dirt collected in the dirt-collection chamber. It is a still further object of the invention to provide a method of separating dirt from dirt-laden air in which the risk of re-entrainment of separated dirt is reduced. 
     The invention provides cyclonic separating apparatus as set out in claim  1 . The invention also provides a method of separating dirt from dirt-laden air as set out in claim  21 . Preferred and advantageous features are set out in the subsidiary claims. 
     The provision of an air return duct communicating with the collecting portion of the dirt-collection chamber and with the interior of the cyclone body provides a separate exit path via which air entering the dirt-collection chamber can return to the cyclone body. This has a number of advantages. Firstly, the airflow within the dirt-collecting chamber is less turbulent so the risk of re-entrainment of dust is reduced. Also, since little or no air is reintroduced to the main airflow in the cyclone body via the entry portion, there is less disturbance to the main airflow. Thirdly, by allowing a small amount of air to flow through the dirt-collection chamber, the separated dirt and fibers can be encouraged to collect in a defined area of the collecting portion from which the separated dirt and fibers can easily be emptied, if required without exposing the user to the collected dirt. 
     It is preferred that the second end of the air return duct approaches the interior of the cyclone body in a direction which is inclined at an acute angle to the direction of flow within the cyclone body at the point of communication therewith. This is advantageous because, in use, the flow of the main airflow past the second end of the air return duct causes, by the venturi effect, air to be drawn out of the dirt-collecting chamber and into the interior of the cyclone body. This in turn helps to smooth the airflow path through the dirt-collecting chamber. 
    
    
     An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of cyclonic separating apparatus according to the invention; 
     FIG. 2 is a side view of the apparatus of FIG.  1 : and 
     FIG. 3 is a sectional view taken along line III-III of FIG.  2 . 
    
    
     The Figures illustrate cyclonic separating apparatus  10  according to the invention. The apparatus  10  is particularly suitable for inclusion in cyclonic vacuum cleaning apparatus. The cyclonic separating apparatus  10  comprises a cyclone body  12  and a dirt-collecting chamber  14 . The cyclone body  12  is generally cylindrical in shape. The cyclone body  12  has a dirt-laden air inlet  16  which is arranged to communicate with the interior of the cyclone body  12  in a tangential manner. The cyclone body  12  also has an outlet  18  which is located centrally of the upper end of the cyclone body  12  and coaxially therewith. The diameters of the inlet  16  and the outlet  18  are substantially the same. A perforated shroud  20  is sealingly mounted on the upper end of the cyclone body  12  and depends therefrom into the interior of the cyclone body  12 . The shroud  20  is coaxial with the cyclone body  12  and the outlet  18  and its distal end  20   a  is closed. The shroud  20  has a multiplicity of perforations  22  extending therethrough to allow air entering the cyclone body  12  via the inlet  16  to exit via the outlet  18 . The function and purpose of the shroud  20  is to reduce the risk of fluff and fine fibers passing through the cyclone body  12  and exiting via the outlet  18 , as described in the U.S. &#39;761 prior art mentioned above. 
     The dirt-collecting chamber  14  communicates with the cyclone body  12  at the lower end thereof, i.e. at the end thereof remote from the inlet  16  and the outlet  18 . The dirt-collecting chamber  14  extends laterally away from the cyclone body  12  and, when viewed from above, has a generally U-shaped configuration (see FIG.  3 ). The dirt-collecting chamber  14  has an entry portion  30  which takes the form of a tangential offtake leading from the cyclone body  12  to a collecting portion  32 . The entry portion  30  has a mouth portion  30   a  which communicates with a linear portion  30   b  leading to a U-shaped portion  30   c . Each of these portions  30   a ,  30   b ,  30   c  has a generally rectangular cross section seen in the direction of flow along the entry portion  30 . However, the external walls  34  which delimit the entry portion  30  in the lateral direction are smoothly curved, at least on the inside, so that they incorporate no sharp bends or sudden changes of direction. 
     The collecting portion  32  comprises a cylindrical chamber  32   a  into which the end of the U-shaped portion  30   c  remote from the mouth portion  30   a  opens. The wall  36  which delimits the cylindrical chamber  32   a  meets the wall of the cyclone body  12  at the point  38  so as to form an airtight seal therewith. The portion of this wall  36  extending between the point  38  and the U-shaped portion  30   c  and facing the inner portion  30   b  has a plurality of apertures  40  extending therethrough. As can be seen in FIG. 1, the apertures  40  are arranged in horizontal rows with the apertures of each row being offset with respect to those of the adjacent rows. 
     The apertures  40  communicate with an air return duct  42  which is delimited partly by the wall  36  which delimits the collecting portion  32 , partly by the wall  34  which delimits the entry portion  30 , and partly by the wall of the cyclone body  12 . The air return duct  42  is also delimited by upper and lower walls  44 ,  46 . The air return duct  42  has an outlet comprising an aperture  48  extending through the wall of the cyclone body  12  so that the air return duct  42  communicates with the interior of the cyclone body  12 . The aperture  48  is located in the wall of the cyclone body  12  so that it opens into the interior of the cyclone body  12  downstream of the mouth portion  30   a  of the dirt-collecting chamber  14 , seen in the direction of flow of incoming dirt-laden air (arrow A). The circumferential spacing α between the downstream edge of the mouth portion  30   a  and the upstream edge of the aperture  48  is kept relatively small so that any disruption to the cyclonic flow of the main airflow circulating within the cyclone body  12  is minimised. The circumferential spacing ox is ideally approximately 15° but can be as much as 40°. 
     The aperture  48  is also inclined at an acute angle β to the direction of flow A of the main airflow within the cyclone body  12  at the point at which the aperture opens into the interior of the cyclone body. The acute angle β is shown here as approximately 30° but can be varied between 20° and 50°. The inclination of the aperture  48  reduces the risk of air which is reintroduced to the interior of the cyclone body  12  via the air return duct  48  causing disruption to the main airflow as it enters. However, it is also desirable that air within the air return duct  48  is drawn into the cyclone body  12  by the main airflow by way of the venturi effect. 
     The collecting portion  32  of the dirt-collecting chamber  14  is provided with means for removing collected dirt therefrom. Depending beneath the cylindrical chamber  32   a  is a cylindrical conduit  50  which has a diameter similar to that of the cylindrical chamber  32   a . The floor  52  of the cylindrical chamber  32   a  is made slidingly or pivotably movable (in any known manner) in order to allow it to be displaced away from the position (shown in solid lines in FIG. 2) in which it forms a barrier between the cylindrical chamber  32   a  and the interior of the cylindrical conduit  50 . In the displaced position (shown in dotted lines in FIG.  2 ), the cylindrical chamber  32   a  communicates directly with the interior of the cylindrical conduit  50 . The lower end  50   a  of the cylindrical conduit  50  is open. 
     A second cylindrical conduit  54  communicates with the cylindrical chamber  32   a  on the upper side thereof. The second cylindrical conduit  54  is axially aligned with both the cylindrical chamber  32   a  and the cylindrical conduit  50 . Again, the diameter of the second cylindrical conduit  54  is essentially similar to that of the cylindrical chamber  32   a . A plunger  56  is slidably mounted within the second cylindrical conduit  54 . An actuating member  58  is fixedly attached to the upper surface of the plunger  56 . The configuration and dimensions of the second cylindrical conduit  54 , the cylindrical chamber  32   a , the cylindrical conduit  50  and the plunger  56  are such that the plunger  56  can be caused to move from a position in which it is wholly located within the second cylindrical conduit  54  to a position in which is it wholly located within the cylindrical conduit  50 . In moving between these two positions, the plunger  56  will be caused to pass through the cylindrical chamber  32   a . If desired, the plunger  56  can be caused to move to a position within the cylindrical conduit  50  in which it is located at or adjacent the lower end  50   a  of the cylindrical conduit  50 . 
     The apparatus described above operates in the following manner. Dirt-laden air is caused to enter the apparatus  10  along the dirt-laden air inlet  16 . The dirt-laden air then enters the cyclone body  12  in a tangential manner and, in view of the orientation of the inlet  16 , the dirt-laden air follows a general helical path around the interior surface of the cyclone body  12  from the upper end thereof to the lower end thereof. As the airflow reverses its direction and begins to travel upwardly from the lower end of the cyclone body  12  towards the upper end thereof, dirt and dust is separated from the main airflow. The main airflow passes through the perforations  22  located in the shroud  20  and exits the apparatus  10  via the outlet  18 . 
     Dirt and dust particles which are separated from the main airflow in the lower end of the cyclone body  12  continue to be carried in a circular path around the lower end of the cyclone body  12 . The dirt and dust particles are carried, partly by inertia and partly by the bleeding off of a small amount of the main airflow (which is preferably less than 10% but could be up to 20%), into the mouth portion  30   a  of the entry portion  30  of the dirt collecting  14 . The dirt and dust particles are carried along the linear portion  30   b  and around the U-shaped portion  30   c  of the entry portion  30  by the bled air which passes along the entry portion  30 . The dirt and dust particles continue to pass along the entry portion  30  until they arrive in the collecting portion  32  of the dirt collecting chamber  14 . Because the dimensions of the cylindrical chamber  32   a  are somewhat larger than the dimensions of the entry portion  30 , some inertial separation takes place and dirt and dust particles are deposited within the cylindrical chamber  32   a.    
     The bled air which has passed along the entry portion  30  and into the collecting portion  32  then passes through the apertures  40  in the wall  36  and into the air return passage  42 . The passage of the air through the apertures  40  also encourages further separation of the dirt and dust particles from the bled air and any remaining large dirt and dust particles are now retained within the cylindrical chamber  32   a . Meanwhile, the bled air passes along the air return duct  42  and is reintroduced into the cyclone body  12  via the aperture  48 . The inclination of the longitudinal direction of the aperture  48  to the direction of flow A within the cyclone body  12  encourages the bled air to be returned to the interior of the cyclone body  12  as explained above in a manner which causes least disruption to the circulating main airflow within the cyclone body  12 . The angle β is, however, sufficiently large to allow the passage of the main airflow across the opening of the aperture  48  to cause the bled air to be sucked out of the air return duct  42  and into the interior of the cyclone body  12  by means of the venturi effect. 
     It is preferred that the aperture  48  is located in the wall of the cyclone body  12  close to the mouth portion  30   a  of the entry portion  30 . This is advantageous because, if there is any disruption to the main airflow caused by the bleeding of a small amount of air into the dirt-collecting portion  14  and its return to the interior of the cyclone body  12 , then the location of the causes of this disruption are confined to a relatively small portion of the circumference of the cyclone body  12 . 
     In order to empty the cylindrical chamber  32   a  of the collecting portion  32  when it is full, the apparatus  10  is first switched off. A receptacle  60  is then placed beneath the lower end  50   a  of the cylindrical conduit  50 . The floor  52  of the cylindrical chamber  32   a  is then moved, by whatever means are provided, to the open position shown in dotted lines in FIG.  2 . The plunger  56  is then moved from the position shown in FIG. 1 in a downward direction so that the plunger  56  passes through the cylindrical chamber  32   a . Dirt and dust collected in the cylindrical chamber  32   a  is therefore removed from the cylindrical chamber  32   a  and dropped or pushed into the cylindrical conduit  50 . Dirt and dust which is not adhered to the walls of the cylindrical conduit  50  will fall into the receptacle  60 . If desired, the plunger  56  can be moved downward to a position in which it lies adjacent the lower end  50   a  of the cylindrical conduit  50 . In this way, substantially all of the dirt and dust previously collected in the cylindrical chamber  32   a  is caused to pass into the receptacle  60 . The plunger  56  can then be retracted to its initial position, the floor  52  can be returned to its closed position (shown in bold lines in FIG.  2 ), and the receptacle  60  can be sealed and disposed of in any convenient manner. The apparatus  10  can then be re-started. 
     It will be appreciated that, although a close contact between the plunger  56  and the walls of the second cylindrical conduit  54  is not shown in FIGS. 1 and 2 for reasons of clarity, the plunger  56  must form a good seal with the walls of the second cylindrical conduit  54 . No significant ingress of air must be allowed between the plunger  56  and the second cylindrical conduit  54 . This would be detrimental to the operation of the separating apparatus  10 . It will also be appreciated that other means of emptying the cylindrical chamber  32   a  will be immediately apparent to a skilled reader. For example, the collecting portion  32  of the dirt-collecting chamber  14  could be formed by a disposable capsule which can be easily and quickly attached to the end of the entry portion  30  remote from the mouth portion  30   a . The attachment of the capsule could be by adhesive tape, snap fitting details or any other convenient means. Instead of providing the cylindrical conduits  50 ,  54  and the plunger arrangement, the capsule could merely be removed when it is full and thrown away. In short, the manner of removal of the dirt and dust collected in the cylindrical chamber  32   a  is not an essential part of the present invention. 
     The advantages of collecting dirt and dust separated in a cyclone in a location which is remote from the cyclone body  12  are well known. The advantage of the present arrangement is that, by bleeding a small amount of the airflow along the entry portion  30  of the dirt-collecting portion  12 , the separated dirt and dust requiring to be transported to the collecting chamber  32  is more reliably deposited therein. Closed collector portions can give rise to unpredictable turbulence within the collector portion which in turn can lead to deposition of dirt and dust in inconvenient locations within the dirt-collecting portion. By providing an outlet for the bled air back into the cyclone body  12 , a smoother, more predictable airflow pattern can be established. 
     Other variations and alternatives will be apparent to a skilled reader. For example, it is not essential that the cyclone body  12  is cylindrical in shape; it could be frusto-conical. It is also envisaged that the apparatus illustrated and described above could form part of a cyclonic separating apparatus in which one or more further cyclonic separators are arranged downstream of the outlet  18  to allow for further cleaning of the dirt and dust which is allowed to exit from the apparatus  10  shown in FIG.  1 . Other means of emptying the dirt-collecting portion  12  will also be apparent and are intended to fall within the scope of the present invention. As an example, the receptacle  60  could be slidingly sealed about the lower end  50   a  of the cylindrical conduit  50  and the floor  52  omitted so that dirt and fibers collected in the cylindrical chamber  32   a  fall directly into the receptacle  60 . When it is full, the receptacle  60  can be removed and either emptied and returned or replaced. The plunger  56  can also be omitted if desired. 
     It is envisaged that the apparatus illustrated and described above will be manufactured from plastics materials. However, other appropriate materials suitable for manufacturing the appropriate components can also be used. 
     In order to make use of the apparatus described above in a cyclonic vacuum cleaner, the dirty-air inlet of the apparatus will communicate with the cleaner head or hose and wand assembly of the vacuum cleaner. The outlet of the apparatus will be connected to a motor/fan unit capable of drawing dirty air into the apparatus via the cleaner head or the hose and wand assembly. One or more further cyclones, capable of separating fine dust from the airflow, may be positioned between the apparatus described above and the motor. The motor may also be protected by one or more filters capable of collecting very fine dust particles. However, the apparatus described above may be used in applications other than vacuum cleaners and has general application in all cases where cyclonic separation is used.