Abstract:
The invention provides a vacuum cleaner comprising an airflow path having a dirty air inlet ( 14 ) and a clean air outlet ( 44   e ), a fan ( 48 ) for drawing an airflow along the airflow path from the dirty air inlet ( 14 ) to the clean air outlet ( 44   e ), a motor ( 50 ) for driving the fan ( 48 ), separating apparatus ( 18 ) for separating dirt and dust from the airflow, a pre-motor filter ( 32 ) arranged upstream of the motor ( 50 ) and a post-motor filter ( 42 ) arranged downstream of the motor ( 50 ), wherein both the pre-motor filter ( 32 ) and the post-motor filter ( 42 ) are cylindrical filters. The invention further provides a vacuum cleaner comprising an airflow path having a dirty air inlet ( 14 ) and a clean air outlet ( 44   e ), a fan ( 48 ) for drawing an airflow along the airflow path from the dirty air inlet ( 14 ) to the clean air outlet ( 44   e ), a motor ( 48 ) for driving the fan ( 50 ), separating apparatus ( 18 ) for separating dirt and dust from the airflow, a pre-motor filter ( 32 ) arranged upstream of the motor ( 50 ) and a post-motor filter ( 42 ) arranged downstream of the motor ( 50 ), wherein the post-motor filter ( 42 ) is housed in a casing ( 44 ) containing a plurality of slots or apertures ( 44   e ), the slots or apertures ( 44   e ) forming the clean air outlet and being arranged such that, in use, the airflow is diffused as it leaves the clean air outlet.

Description:
FIELD OF THE INVENTION 
     The invention relates to a vacuum cleaner. 
     BACKGROUND OF THE INVENTION 
     In general, a vacuum cleaner incorporates a dirty air inlet, separating apparatus for separating dirt and dust from an airflow, a fan and motor for drawing an airflow into the separating apparatus via the dirty air inlet, and an outlet for expelling clean air into the atmosphere. Very often, a pre-motor filter is arranged in the airflow path upstream of the motor to prevent any dust or debris remaining entrained within the airflow from entering the motor. This reduces the risk of the motor becoming damaged or worn as a result of dirt or dust passing therethrough and also prevents such dirt or dust from being expelled into the atmosphere. It is also quite common for a post-motor filter to be arranged downstream of the motor to prevent any carbon particles dislodged within the motor, for example from the brushes within the motor, from being expelled into the atmosphere with the airflow. These pre- and post-motor filters are normally simple filters or pleated filters which are positioned such that they are relatively easily accessibly whilst being unobtrusive during normal use of the vacuum cleaner. Known vacuum cleaners house the pre- and post-motor filters in cassettes slidably receivable in slots or sockets in the motor casing or within the main casing so that they become visible when the cleaner is opened to allow the separating apparatus to be emptied 
     A disadvantage of the existing pre- and post-motor filters is that they are often relatively small in size, which means that the available filtering surface is relatively small. The filters can therefore become clogged over a period of time, despite the small amount of dust and debris they collect, which can affect the performance of the vacuum cleaner. They therefore require to be cleaned or changed more often than is desirable and this leads to increased costs and/or customer dissatisfaction. A further disadvantage is that, because the filters are generally hidden during normal operation of the vacuum cleaner, the user of the vacuum cleaner is often unaware that the pre- or post-motor filter may require changing which frustrates the user of the vacuum cleaner. 
     Another disadvantage of known vacuum cleaners relates to the cleaner outlet. Very often, the clean air is expelled to the atmosphere in the form of a stream of air. In some cases the expelled air is directed in front of the cleaner which can disturb debris which the user intended to pick up with the cleaner. Streams of expelled air can also cause difficulties such as extinguishing pilot lights on gas fires or disturbing curtains, other furnishing or papers lying near the vacuum cleaner. The more powerful the motor of the cleaner, the more likely the expelled air is to cause a disturbance. 
     It is an object of the present invention to provide a vacuum cleaner having pre- and post-motor filters which do not require to be cleaned or replaced as frequently as known cleaners. It is a further object to provide a vacuum cleaner having pre- and post-motor filters, in which the fact that one or both of the filters requires cleaning or replacement is more readily apparent to a use of the vacuum cleaner than is currently the case. A still further object of the invention is to provide a vacuum cleaner in which the stream of air exiting the clean air outlet is less likely to cause difficulties than in known vacuum cleaners. 
     SUMMARY OF THE INVENTION 
     The invention provides a vacuum cleaner which utilizes cylindrical filters that expose a significantly larger filtration surface area to the airflow which extends the useful life of each filter. The preferable co-axial arrangement of the filters with the airflow passing through the centre of the post-motor filter allows the filters to be conveniently located adjacent one another so that they can be accessed easily, should cleaning or replacement be required. 
     The invention also provides a vacuum cleaner which diffuses air as it exits the outlet. This diffusion reduces the intensity of the exiting airstream which avoids the problems mentioned above and reduces customer dissatisfaction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the invention will now be described with reference to the accompanying drawings, wherein: 
     FIGS. 1 a  and  1   b  are side and front views respectively of a vacuum cleaner according to the invention; 
     FIGS. 2 a  and  2   b  are isometric views of the pre-motor filter and the pre-motor filter housing respectively, each forming part of the vacuum cleaner of FIGS. 1 a  and  1   b ; 
     FIGS. 3 a  and  3   b  are isometric views of the post-motor filter and the post-motor filter housing respectively, each forming part of the vacuum cleaner of FIGS. 1 a  and  1   b ; and 
     FIG. 4 is a sectional side view of the filters of FIGS. 2 and 3 illustrated in coaxial arrangement as in use. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A vacuum cleaner according to the invention is illustrated in FIGS. 1 a  and  1   b . As can readily be seen, the vacuum cleaner  10  is an upright cleaner having a cleaner head  12  which incorporates a dirty air inlet  14 . A central support member  16  supports dust separating apparatus  18  on one side thereof and a filter arrangement  20  on the other side thereof. An upwardly extending handle  22  is positioned rearwardly of the central support member  16  and is optionally releasable in the manner of a wand if the vacuum cleaner  10  is to be used in the cylinder mode. The upwardly extending handle  22  incorporates a hand grip  24  and other features which do not form part of the present invention. The cleaner head  12  is pivotably attached to a motor casing  26  to which support wheels  28  are attached and inside which a motor is located In use, the motor draws dirty air into the vacuum cleaner  10  via the dirty air inlet  14  or alternatively via the wand  22 . The air then passes through the dirt and dust separating apparatus  18  and through the filter assembly  20  before being expelled to the atmosphere. 
     The dirt and dust separating apparatus  18  does not form part of the present invention. The separating apparatus  18  can take the form of a bag or other separating means, e.g. cyclonic separating apparatus. In the example shown, it is envisaged that the dirt and dust separating apparatus  18  will take the form of two concentric cyclones designed to remove dirt and dust particles from the airflow. The airflow is fed to the dirt and dust separating apparatus  18  via conduits housed within the central support member  16 . 
     Once the airflow has passed through the dirt and dust separating apparatus  18 , it is then transferred, via a conduit housed within the central support member  16 , to the filter assembly  20 . The filter assembly  20  is located on the side of the central support member  16  remote from the dirt and dust separating apparatus  18 . 
     It is envisaged that the general shape of the filter assembly  20  will be similar to that of the dirt and dust separating apparatus  18 . For example, in the embodiment shown, the dirt and dust separating apparatus  18  will be generally cylindrical in shape and the filter assembly  20  will therefore also be cylindrical in shape with substantially the same diameter as that of the dirt and dust separating apparatus  18 . 
     The filter assembly  20  consists of a pre-motor filter assembly  30  and a post-motor filter assembly  40 . The pre-motor filter assembly  30  is illustrated in FIGS. 2 a  and  2   b  and the post-motor filter assembly  40  is illustrated in FIGS. 3 a  and  3   b . Each assembly  30 , 40  consists of a cylindrical filter  32 , 42  located within a housing  34 , 44 . In each cylindrical filter  32 , 42 , the filtration material is pleated and formed into a cylindrical shape with caps  32   a , 32   a ′, 42   a , 42   a ′ located at either end to maintain the shape of the filter. The pleating of each filter, the support mesh  32   b , 42   b  and the fitting of the filtration material into the end caps  32   a , 32   a ′, 42   a , 42   a  are all standard and known in the art. These details will not be described any further here. 
     Each housing  34 , 44  is designed and arranged to hold the respective filter  32 , 42 . Each housing  34 , 44  is also designed and arranged so as to direct the airflow entering the filter assembly  20  along the correct airflow path. The pre-motor filter housing  34  has a generally cylindrical outer wall  34   a  whose diameter is approximately 10 mm larger than the external diameter of the pre-motor filter  32 . This allows an annular chamber  34   b  to be formed between the outer surface of the pre-motor filter  32  and the cylindrical outer wall  34   a  of the housing  34 . The upper end of the outer wall  34   a  is open to allow the pre-motor filter  32  to be dropped into the housing  34  with ease. A collar  34   c  extending outwardly from the upper end cap  32   a  centralises the filter  32  when dropped into the housing  34 . A loop-shaped tab  32   d  is fixed to the upper end cap  32   a  to allow the filter  32  to be easily removed from the housing  34  when required. A similar collar  42   c  and tab  42   d  are fixed to the upper end cap  42   a  of the post-motor filter  42  for the same reason. 
     At the lower end of the pre-motor housing  34  is an annular base  34   d  having a cylindrical opening in the centre thereof. Upstanding from the annular base  34   d  are a plurality of upstanding webs  34   e  on which the lower end of the pre-motor filter  32  is supported. Radial channels are formed between the upstanding webs  34   e  along which the airflow can pass. A ridge or groove  34   f  is formed in the annular base  34   d  around the periphery thereof to receive the post-motor filter housing  44 . 
     The lower end of the pre-motor filter  32  is closed by means of the cap  32   a ′ extending across the central aperture of the cylindrical filter  32 . In this way, air is prevented from passing down the centre of the pre-motor filter  32  beyond the end cap  32   a′.    
     The post-motor filter housing  44  also consists generally of an outer cylindrical wall  44   a . The diameter of the outer cylindrical wall  44   a  is approximately 10 mm greater than the outer diameter of the post-motor filter  42 . This allows an annular chamber  44   c  to be created therebetween. A plurality of slots  44   e  are provided in the outer wall  44   a  and extend around substantially all of the circumference thereof. Bosses  44   f  are provided on the base of the post-motor filter housing  44  for receiving screws (not shown). 
     An inner cylindrical wall  44   b  forming part of the motor casing of the vacuum cleaner extends upwardly through the centre of the cylindrical post-motor filter  42 . The upper lip of the inner cylindrical wall  44   b  is dimensioned and arranged so as to abut against the inner circumference of the annular base  34   d  of the pre-motor filter housing  34 . Sealing means  45  are provided between the upper lip and the annular base  34   d . The lower end of the inner cylindrical wall  44   b  is integral with a conduit  46  arranged in the motor casing  26  which leads the airflow through the fan  48  and past the motor  50  before returning it to the post-motor filter  42 . 
     The diameter of the inner cylindrical wall  44   b  is approximately 15 mm less than the inner diameter of the post-motor filter  42  so that a second annular chamber  44   d  is created therebetween. The second annular chamber  44   d  communicates with the conduit  46  downstream of the fan  48  and the motor  50 . This portion of the conduit  46  is essentially the exhaust side of the motor housing. 
     The filter assembly  20  operates in the following manner. The airflow enters the pre-motor filter assembly  30  via a conduit  31  which communicates with the interior of the pre-motor filter  32 . There being no axial escape route due to the cap  32   a  at the bottom of the filter  32  extending across the interior of the filter  32 , the airflow is forced to pass through the filter  32  in an outwardly radial direction. The airflow then enters the annular chamber  34   b  and passes downwardly to the conduits arranged between the upwardly extending webs  34   e . The airflow passes radially inwardly between the webs  34   e  and then passes axially down inside the inner cylindrical wall  44   b  within the post-motor filter housing  44 . The airflow thus by-passes the post-motor filter  42  until it has passed along the conduit  46  leading to the fan  48  and the motor  50 . The airflow passes through the fan  48 , around the motor  50 , thus having a cooling effect, and then back into the second annular chamber  44   d  located between the post-motor filter  42  and the inner cylindrical wall  44   b . Because the upper end of the post-motor filter  42  is sealed to the top of the inner cylindrical wall  44   b , the airflow is forced to pass through the post-motor filter  42 . It then passes through the annular chamber  44   c  and exits the post-motor filter housing  44  via the slots  44   e  into the atmosphere. 
     The conduit  46  and inner cylindrical wall  44   b  form part of the motor casing  26  of the vacuum cleaner  10  or may take the form of separate parts fixed to or located within the motor casing. The fan  48  and the motor  50  are also permanently housed within the motor casing  26 . However, the pre-motor filter  32 , the post-motor filter  42  and the pre-motor filter housing  34  are all removable from the vacuum cleaner  10 . The post-motor filter housing  44  is permanently fixed by means of screws, preferably by passing the screws upwardly through bores in the motor casing and into the bosses  44   f , into the position shown in FIG. 1 b . The post-motor filer  42  is made accessible by removing the pre-motor filter housing  34  from the vacuum cleaner  10 . The post-motor filter  42  can then be removed from the fixed post-motor filter housing  44  via its open upper end. 
     At the upper end of the filter assembly  20 , a releasable fastening device must be employed. Any appropriate releasable fastening means will suffice; for example, a snap-fit arrangement or releasable clip. The arrangement illustrated in FIG. 4 consists of a rotatable collar  52  which, in its operational position, is biased into a downward position. A depending tube  54  having cylindrical walls makes a seal with the inner circumference of the end cap  32   a  of the pre-motor filter  32  so as to ensure that an airflow entering the filter assembly  20  is directed into the interior of the pre-motor filter  32 , and also with the upper lip of the outer cylindrical wall  34   a  of the pre-motor filter housing  34 . The tube  54  centralises and maintains the pre-motor filter  32  and the pre-motor filter housing  34  in the appropriate position. The ridge or groove  34   f  at the lower end of the cylindrical wall  34   a  maintains the desired relative positions of the pre-motor filter housing  34  and the post-motor filter housing  44 . 
     The collar  52  is designed so as to be rotatable with respect to the body of the vacuum cleaner and also with respect to the pre-motor filter housing  34 . Cam surfaces (not shown) are provided such that, when the collar  52  is rotated, it is lifted with respect to the pre-motor filter housing  34  so that the tube  54  depending from the collar  52  is raised clear of the filter  32  and the housing  34 . Biasing means (not shown) are provided in order to bias the collar  52  into its downward position in order to avoid inadvertent raising of the collar  52 . The biasing means can take the form of a stop detail in the profile of the cam surfaces, resilient plastic strips, deformable foam materials, torsion springs etc. 
     In order to remove the filter assembly  20  from the vacuum cleaner  10 , the collar  52  is rotated against the action of the biasing means. The cylindrical walls of the tube  54  depending from the collar  52  are raised clear of the filter  32  and the cylindrical wall  34   a  of the housing  34 . This allows the housing  34  to be lifted slightly and removed from the post-motor filter housing  44 . As soon as the pre-motor filter housing  34  has been removed, the post-motor filter  42  can be removed from the post-motor filter housing  44  merely by lifting it from the housing  34 . The pre-motor filter  32  can also be lifted or tipped out of its housing  34 . Removing either or both housings  34 , 44  means that either or both filters  32 , 42  can be removed or replaced as desired. 
     The housings  34 ,  44  are moulded from transparent plastics materials. The transparency of the cylindrical walls  34   a , 44   a  of the housings  34 , 44  allows a user of the vacuum cleaner  10  to inspect the filters  32 , 42  for signs of clogging. There is no requirement that the pre-motor filter  32  and post-motor filter  42  be inspected only when the dust separating apparatus  18  are accessed for emptying purposes. The filters  32 , 42  are visible to the user at all times and the user can therefore readily determine whether or not either or both filters  32 , 42  require replacement. Because both the pre-motor filter  32  and the post-motor filter  42  are cylindrical filters having large filtration surface areas, it is envisaged that neither filter  32 , 42  will require replacement very often. 
     The slots  44   e  located in the post-motor filter housing  44  extend around substantially all of the circumference of the housing  44 . The substantial area through which the airflow is expelled from the vacuum cleaner  10  means that the strength of the exiting airflow is not high. Furthermore, because the slots are arranged on a curved surface, in this case a cylindrical surface, the airflow is diffused as it leaves the vacuum cleaner. The strength of the airflow is thereby considerably reduced and therefore the problems previously associated with concentrated airflows are avoided. 
     As a further example, the following dimensions are given in order to further enable a skilled reader to the put the invention into practice. 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 External diameter of filters 32, 42 
                 10 cm 
               
               
                   
                 Internal diameter of filters 32, 42 
                 5.2 cm 
               
               
                   
                 Length of filters 32, 42 
                 14 cm 
               
               
                   
                 Internal diameter of outer cylindrical walls 34a, 44a 
                 11 cm 
               
               
                   
                 External diameter of inner cylindrical wall 44b 
                 3.7 cm 
               
               
                   
                   
               
             
          
         
       
     
     The scope of the invention is not limited to the precise details of the embodiment described above. Modifications and variations will be apparent to a reader skilled in the art For example, the post-motor filter housing can be made releasable from the motor casing if desired.