Abstract:
A vacuum cleaner comprising a separating apparatus comprising a first cyclonic separator and a second cyclonic separator arranged in parallel with the first cyclonic separator, an airflow generator arranged to generate an airflow through the first and second cyclonic separators, and a flow control device for controlling the flow of air through the second cyclonic separator. The vacuum cleaner has a first configuration in which the flow control device is arranged to prevent flow of air through the second cyclonic separator such that, in use, air flows through the first cyclonic separator and bypasses the second cyclonic separator, and a second configuration in which the flow control device is arranged to permit flow of air though the second cyclonic separator such that, in use, air flows through the first and second cyclonic separators.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to United Kingdom Application No. 1411749.3, filed Jul. 2, 2014, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    This invention relates to a vacuum cleaner, and particularly relates to a vacuum cleaner comprising a cyclonic separator. 
       BACKGROUND OF THE INVENTION 
       [0003]    GB2502819A shows a battery-powered handheld vacuum cleaner which is similar to the handheld vacuum cleaner DC59 manufactured by Dyson and sold in the United Kingdom. 
         [0004]    DC59 is a battery-powered lightweight handheld vacuum that comprises a cyclonic separator. 
         [0005]    The vacuum cleaner can be operated in two modes: a low-flow mode in which the vacuum can be used to clean lightly soiled floors, and a high-flow mode in which the vacuum can be used to clean heavily soiled floors. Typically, it is expected that the vacuum cleaner will be used in the low-flow mode most of the time in order to conserve battery power. The vacuum cleaner can be switched to the high-flow mode for short, intensive cleaning tasks. 
         [0006]    The cyclonic separator comprises a single primary cyclonic separator and a plurality of secondary cyclonic separators. The cyclonic separators are configured to provide optimum separation efficiency when the vacuum cleaner is operated in the low-flow mode. 
         [0007]    When the vacuum cleaner is operated in the high-flow mode, the greater airflow through the vacuum cleaner means that the secondary cyclonic separators become choked, which is detrimental to the performance of the vacuum cleaner. 
       SUMMARY OF THE INVENTION 
       [0008]    According to a first aspect of the invention there is provided a vacuum cleaner comprising a separating apparatus comprising a first cyclonic separator and a second cyclonic separator arranged in parallel with the first cyclonic separator, an airflow generator arranged to generate an airflow through the first and second cyclonic separators, and a flow control device for controlling the flow of air through the second cyclonic separator, wherein the vacuum cleaner has a first configuration in which the flow control device is arranged to prevent flow of air through the second cyclonic separator such that, in use, air flows through the first cyclonic separator and bypasses the second cyclonic separator, and a second configuration in which the flow control device is arranged to permit flow of air though the second cyclonic separator such that, in use, air flows through the first and second cyclonic separators. 
         [0009]    The airflow generator may have a low-flow configuration in which the airflow generator generates a flow of air through the separating apparatus at a first flow rate, and a high-flow configuration in which the airflow generator generates a flow of air through the separating apparatus at a second flow rate which is greater than the first flow rate. 
         [0010]    The vacuum cleaner may be configured such that, in use, the airflow generator operates in the low-flow configuration when the vacuum cleaner is in the first configuration and the airflow generator operates in the high-flow configuration when the vacuum cleaner is in the second configuration. 
         [0011]    The vacuum cleaner may be configured such that, in use, the flow rate through the first cyclonic separator when the vacuum cleaner is in the first configuration is the same as the flow rate through the first cyclonic separator when the vacuum cleaner is in the second configuration. 
         [0012]    The first and second cyclonic separators may be configured such that, in use, when the vacuum cleaner is in the second configuration, the flow rate through the first cyclonic separator is the same as the flow rate through the second cyclonic separator. 
         [0013]    The first and second cyclonic separators may be identical. 
         [0014]    The separating apparatus may comprise a plurality of first cyclonic separators. The first cyclonic separators may be identical. 
         [0015]    The separating apparatus may comprise a plurality of second cyclonic separators. The second cyclonic separators may be identical. 
         [0016]    The vacuum cleaner may further comprise a first debris collector arranged to collect debris separated from the airflow by the first cyclonic separator, and a second debris collector arranged to collect debris separated from the airflow by the second cyclonic separator. The first and second debris collectors may be fluidly isolated from each other. 
         [0017]    The separating apparatus may comprise a primary separator disposed upstream and in series with the first and second cyclonic separators. The primary separator may be a cyclonic separator. Alternatively, the primary separator may be an inertial separator. 
         [0018]    The flow control device may comprise a valve. The valve may be disposed downstream of the second cyclonic separator. 
         [0019]    The vacuum cleaner may be a battery-powered vacuum cleaner. 
         [0020]    The vacuum cleaner may further comprise a user-operable switch which is configured such that a user can switch the vacuum cleaner between the first configuration and the second configuration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    In order to better understand the present invention, and to show more clearly how the invention may be put into effect, the invention will now be described, by way of example, with reference to the following drawings: 
           [0022]      FIG. 1  is a schematic representation of a separating apparatus and an airflow generator of a vacuum cleaner; 
           [0023]      FIG. 2  is a schematic representation of the separating apparatus and airflow generator shown in  FIG. 1  showing an airflow through the separating apparatus when the separating apparatus is in a first configuration; and 
           [0024]      FIG. 3  is a schematic representation of the separating apparatus and airflow generator shown in  FIG. 1 , showing an airflow through the separating apparatus when the separating apparatus is in a second configuration. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIG. 1  is a schematic representation of a separating apparatus  2  and an airflow generator  4  of a battery-powered vacuum cleaner. 
         [0026]    The separating apparatus  2  comprises a primary cyclonic separator  6  and a plurality of secondary cyclonic separators  8  disposed fluidly downstream of the primary cyclonic separator  6  (the secondary cyclonic separators  8  are in series with the primary cyclonic separator  6 ). The secondary cyclonic separators  8  are arranged so that they are fluidly in parallel with each other. 
         [0027]    The secondary cyclonic separators  8  comprise two sets of cyclonic separators: a first set of cyclonic separators  10  and a second set of cyclonic separators  12 . In the embodiment shown, the first set of separators  10  comprises ten cyclonic separators  8  and the second set of separators comprises five cyclonic separators. There are fifteen secondary cyclonic separators  8  in total; however, for ease of reference, only one cyclonic separator  8  from each set  10 ,  12  is shown. The performance characteristics of all of the secondary cyclonic separators  8  are identical. 
         [0028]    The airflow generator  4  is disposed downstream of the secondary cyclonic separators  8 . The airflow generator  4  is arranged to draw air through the primary cyclonic separator  6  and the secondary cyclonic separators  8 . The airflow generator  4  may comprise a motor and an impeller (not shown). The airflow generator  4  has two modes of operation: a low-flow mode and a high-flow mode. In the low-flow mode, the airflow generator  4  generates a low volumetric flow rate of air through the separating apparatus  2 . In the high-flow mode, the airflow generator  4  generates a relatively high volumetric flow rate of air through the separating apparatus  2  compared with the low-flow mode. 
         [0029]    The primary cyclonic separator  6  comprises a cylindrical separating chamber  14  having an air inlet  16  and an air outlet  18 . The air inlet  16  is provided in a side wall of the separating chamber  14 . The air inlet  16  is configured to produce a rotational flow within the separating chamber  14  about a central axis X of the separating chamber  14 . 
         [0030]    A cylindrical screen  20  extends coaxially with the central axis X within the separating chamber  14 . The cylindrical screen  20  acts as a vortex finder within the separating chamber  14 . Holes in the screen  20  provide the outlet  18  from the separating chamber  14 . Such an arrangement is commonly referred to as a shroud. 
         [0031]    A dirt collection chamber  22  is provided below the separating chamber  14  and the air outlet  18 . The dirt collection chamber  22  may be formed by a bin which is detachable from the remainder of the separating apparatus  2 . 
         [0032]    The secondary cyclonic separators  8  are disposed above the primary cyclonic separator  6  and are arranged in an array which extends around the central axis X. Each secondary cyclonic separator  8  comprises a separating chamber  24 , which in the embodiment shown is conical, having an air inlet  26 , an air outlet  28  and a solids outlet  30 . The air inlet  26  is arranged to generate a rotational flow within the separating chamber  24 . 
         [0033]    A primary outlet duct  32  extends upwardly from the cylindrical screen  20  to an inlet manifold  34 . The inlet manifold  34  is in fluid communication with each of the respective air inlets  26  of the secondary cyclonic separators  8 . 
         [0034]    A vortex finder  36  extends from the upper region of the separating chamber  24  of each of the secondary cyclonic separators  8 . Each vortex finder  36  comprises an open-ended tube that extends along an axis Y of each secondary cyclonic separator  8 . The air outlet  28  of each secondary cyclonic separator  8  is defined by the opening at the lower end of the vortex finder  36 . Each air outlet  28  is in fluid communication with the airflow generator  4  via the vortex finder  36 , an outlet duct  38  and a common outlet manifold  40  into which each outlet duct  38  opens. An optional filter  42  is disposed between the outlet manifold  40  and the airflow generator  4 . 
         [0035]    The solids outlet  30  is located at the lower end of the separating chamber  24  of each secondary cyclonic separator  8 . A first fine dirt collection chamber  44  is disposed beneath the solids outlets  30  of the first set of cyclonic separators  10 . A second fine dirt collection chamber  46  is disposed beneath the solids outlets  30  of the second set of cyclonic separators  12 . 
         [0036]    The first and second fine dirt collection chambers  44 ,  46  are separate chambers that are fluidly isolated from each other: that is, air cannot pass directly from one of the chambers  44 ,  46  to the other. 
         [0037]    A flow control device in the form of a valve  48  is disposed at a junction between the outlet ducts  38  for the second set of cyclonic separators  12  and the outlet manifold  40 . The valve  48  has a closed state in which air is prevented from being drawn by the airflow generator  4  through the second set  12  of secondary cyclonic separators  8  and an open state in which air can be drawn by the airflow generator  4  through the second set  12  of secondary cyclonic separators  8 . 
         [0038]    When the valve  48  is closed, air flows through the primary cyclonic separator  6  and the first set  10  of secondary cyclonic separators  8  only. When the valve  48  is open, air flows through the primary cyclonic separator  6  and both the first and second sets  10 ,  12  of secondary cyclonic separators  8 . 
         [0039]    The airflow generator  4  and the valve  48  are connected to a controller (not shown), for example a Programmable Logic Controller, which controls operation of the airflow generator  4  and the valve  48 . 
         [0040]    The controller may be configured to control the airflow generator  4  and the valve  48  automatically, for example in response to a sensed reduction in pressure within a cleaner head attached to the vacuum cleaner, or in response to a command initiated by a user, for example, by actuating a switch provided on the vacuum cleaner. The valve  48  may be controlled via a mechanical, electromagnetic, hydraulic or pneumatic actuator connected to the controller. 
         [0041]    The vacuum cleaner has a first configuration (shown in  FIG. 2 ) in which the airflow generator  4  is in the low-flow mode and the valve  48  is closed, and a second configuration (shown in  FIG. 3 ) in which the airflow generator  4  is in the high-flow mode and the valve  48  is open. The first configuration is suitable for cleaning lightly soiled surfaces without drawing a large amount of power from the battery. The higher flow rate in the second configuration translates into an increase in the pick-up performance of the vacuum cleaner, which is of particular benefit for cleaning heavily soiled surfaces. The controller is configured to control the airflow generator  4  and the valve  48  simultaneously so that the vacuum cleaner can be switched between the first and second configurations simply. 
         [0042]    In the first configuration, the airflow generator  4  generates a relatively low flow rate of air through the primary cyclonic separator  6  and the first set of secondary cyclonic separators  10 . Flow through each of the cyclonic separators  8  of the first set  10  of cyclonic separators  8  is distributed evenly. For example, if the airflow generator  4  generates a flow rate of 10 litres/second through the separating apparatus  2 , the flow rate through each of the cyclonic separators  8  is 1 litre/second. The cyclonic separators  8  of the first set of the secondary cyclonic separators  10  are configured so that their separation efficiency is optimised for a flow rate of 1 litre/second. Consequently, the cyclonic separators  8  of the first set of cyclonic separators  10  operate at their optimum separation efficiency when the vacuum cleaner is in the first configuration. The optimum separation efficiency is dependent on the required performance characteristics of the vacuum cleaner, and may be a target “cut point” at a particular particle size. 
         [0043]    When the vacuum cleaner is switched to the second configuration, the airflow generator  4  generates a relatively high volumetric flow rate of air through the primary cyclonic separator  6 , and through both the first and second sets  10 ,  12  of secondary cyclonic separators  8 . Flow through each of the cyclonic separators  8  of the first and second set of separators  10 ,  12  is distributed evenly. For example, if the airflow generator  4  generates a flow rate of 15 litres/second through the separating apparatus  2 , the flow rate through each of the cyclonic separators  8  is 1 litre/second. The cyclonic separators  8  of first set of cyclonic separators  10  therefore continue to operate at their optimum separation efficiency. In addition, the second set of cyclonic separators  12 , which are also configured so that their separation efficiency is greatest for a flow rate of 1 litre/second, operate at their optimum separation efficiency. 
         [0044]    An advantage of the arrangement described above, is that the secondary cyclonic separators  8  of the separating apparatus  2  having two modes of operation can operate at optimal efficiency in both modes. Poor separation efficiency caused by low speeds or choking of the secondary cyclonic separators is therefore avoided. 
         [0045]    The above arrangement is described by way of example only. It will be appreciated that there are other configurations of secondary cyclonic separators that could be used. For example, the first set of cyclonic separators may comprise fewer cyclonic separators than the second set of cyclonic separators, or the number of cyclonic separators in each set may be the same. In each case, the performance characteristics of the first and second sets of cyclonic separators would tailored towards the flow rates at each mode of operation of the airflow generator so that the secondary cyclonic separators operate at their optimum efficiencies in each mode. 
         [0046]    In an alternative embodiment, the single valve may be replaced with multiple valves arranged to control the flow of air through each secondary cyclonic separator. The valves could be opened and closed in unison to control flow through the secondary set of cyclonic separators. 
         [0047]    It will be appreciated that the flow control device and the airflow generator may be controlled in accordance with a sensed parameter, such as the sensed flow rate through the separator. For example, if the flow rate drops below a predetermined threshold, air flow through the second set of cyclonic separators is stopped by the flow control device in order to maintain (or increase) the separating efficiency of the first set of cyclonic separators. 
         [0048]    It will be appreciated that either or both of the first and second sets of cyclonic separators could comprise a single cyclonic separator. For example, both sets could comprise a single cyclonic separator, or the first set could comprise a plurality of cyclonic separators and the second set could comprise a single cyclonic separator, and vice versa. 
         [0049]    In a further embodiment, the primary cyclonic separator could be replaced by a non-cyclonic separator, such as an inertial separator. 
         [0050]    Further sets of secondary cyclonic separators could be provided having respective flow control devices and the airflow generator could be configured to generate respective airflow rates through the secondary cyclonic separators depending on which sets of separators have air passing through them. For example, a third set of secondary cyclonic separators could be provided having a corresponding flow control device. The airflow generator could be configured to produce a flow rate greater than the high-flow rate when air passes through all of the first, second and third sets of secondary cyclonic separators.