Abstract:
A pool cleaning robot for cleaning a surface of a swimming pool, said robot may include: a main housing; main wheels being configured for propelling the robot and for rotating at a first angular velocity; at least one auxiliary brushwheel disposed between said main wheels; and at least one inlet being formed in a bottom panel of the housing between said main wheels and being configured for intake of water and debris; wherein said robot is configured for rotating said auxiliary brushwheel about an axis of rotation at a second angular velocity which is substantially greater than the first angular velocity; wherein said second angular velocity is at least substantially twice that of the first angular velocity.

Description:
FIELD OF THE INVENTION 
     This invention relates to pool cleaning robots, and to filter units for use therewith. 
     BACKGROUND OF THE INVENTION 
     Pool cleaning robots which automatically scan the floor and/or sidewalk of a swimming pool are well known in the art. These units are powered internally, by one or More battery packs, or externally, by way of a power cable. A robot of this type typically comprises a drive motor, a pump motor with an impeller, a filter, brushwheels, and a track. All of these components are contained within a housing. The housing comprises inlets at the bottom, and an outlet at the top. The robot comprises several sections, which permits at least partial disassembly of the robot. 
     The drive motor drives the track, which propels the robot. In addition, the motion of the track imparts a rotation to the brushwheels, which scrubs the surface of the pool. 
     The pump motor drives the impeller to create an upwardly directed suction. This suction draws water, and with it debris, through the inlets and exiting the outlet via the filter. 
     The drawing of the water through the inlets further provides a suction force which helps maintain the robot&#39;s position on the floor of the swimming pool, and is especially important for maintaining the robot on the sidewalls when scanning there. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, there is provided a pool cleaning robot for cleaning a surface of a swimming pool, the robot comprising:
         a main housing;   at pair of main wheels disposed at opposite ends of a bottom panel of the housing spanning along a majority of its width and carrying a pair of continuous tracks spanning between edges thereof, the main wheels being configured for rotating at a first angular velocity (it will be appreciated that herein, unless otherwise noted, when comparing angular velocities, only the magnitudes thereof are taken into account, with direction being ignored);   at least one inlet being formed in the bottom panel between the main wheels and being configured for intake of water and debris; and   at least one auxiliary brushwheel disposed between the main wheels;
 
the robot being configured for rotating the auxiliary brushwheel about an axis of rotation at a second angular velocity which is substantially greater than the first angular velocity.
       

     Herein the specification and claims, the term “surface” when used in reference to as pool is used in its broadest sense, including, but not limited to, bottom and side surfaces thereof. 
     The robot may be designed such that motion thereof is independent of the rotation of the auxiliary brushwheel, i.e., the rotation of the auxiliary brushwheel at an elevated speed does not impact the movement of the robot. For example, the auxiliary brushwheel may be disposed at a position sufficiently raised from a planar surface disposed below the robot such that motion of the robot on the planar surface is independent of the rotation of the auxiliary brushwheel. This arrangement ensures that the pressure between the auxiliary brushwheel and the planar surface is sufficiently low that it does not influence the motion of the robot. 
     The second angular velocity may be at least substantially twice that of the first angular velocity. 
     The inlet may be is formed between one of the main wheels and the auxiliary brushwheel. 
     The robot may be configured to rotate the auxiliary brushwheel such that the direction of movement of a portion thereof contacting the pool surface is toward the inlet. 
     The bottom panel may have first and second halves being separated by an axis spanning along the bottom panel between midpoints of the main wheels, the robot comprising:
         two auxiliary brushwheels, a first of the auxiliary brushwheels being disposed substantially between the axis and one of the tracks, and a second of the brushwheels being disposed substantially between the axis and the other of the tracks; and   two of the inlets, a first of the inlets being formed substantially in the first half of the bottom panel between the auxiliary brushwheel and a first of the main wheels, and a second of the inlets being formed substantially in the second half of the bottom panel between the auxiliary brushwheel and a second of the main wheels;
 
wherein the robot is configured to rotate the first auxiliary brushwheel such that the direction of movement of a portion thereof contacting the pool surface is toward the first inlet, and to rotate the second auxiliary brushwheel such that the direction of movement of a portion thereof contacting the pool surface is toward the second inlet.
       

     The track and main wheel may be co-configured so that the tracks move in tandem with the rotation of the main wheels. 
     The robot may further comprise a motor and a drive element, the drive element, which may be a gear, being configured to:
         transmit rotational motion of the motor to linear motion of the track; and   transmit rotational motion of the motor to rotational motion of the auxiliary brushwheel.       

     The track may be co-configured with the drive element to rotate in tandem with movement thereof. 
     The robot may further comprise a compound gear with first and second gear stages, the compound gear being arranged such that the first gear stage meshes with the drive element, and the second gear stage meshes with a gear rotationally fixed to the auxiliary brushwheel. 
     The auxiliary brushwheel may comprise a plurality of bristles, each bristle comprising a shaft and a head, the shaft being flexible enough so that rotation of the auxiliary brushwheel does not substantially affect the movement of the robot, the head being designed to dislodge debris from the pool surfaces. 
     Each of the heads may project laterally from the bristle in a direction which is substantially parallel to the axis of rotation of the auxiliary brushwheel. 
     In addition, each of the heads may comprise one or more blades extending substantially parallel to the axis of rotation of the auxiliary brushwheel. 
     The auxiliary brushwheel may comprise:
         a drive cylinder formed on its perimeter with longitudinally extending grooves; and   a plurality of bristle units, each carrying a plurality of the bristles, and adapted for being removably retained within the grooves.       

     The arrangement facilitates replacement of bristles. 
     The main wheels may be further configured for dislodging debris from the pool surfaces (i.e., they may be brushwheels). 
     According to another aspect of the present invention, there is provided it filter kit for use with a pool cleaning robot, the filter kit comprising:
         a frame configured for attachment thereto of one or more filter elements and insertion into a pool cleaning robot in a fluid path between an inlet and outlet thereof for; and   two or more of the filter elements of substantially different designs.       

     One of the filter elements may be of fine filter constituting a fabric-like screen configured to substantially cover at least one side, or two opposing sides, of the frame. 
     The kit may further comprise a securing element configured to substantially cover at least one side of the frame and to secure the screen therebetween. The securing element may comprises one, two, or more panes comprising a coarse filter formed integrally therewith, the securing element being configured so that the pane lies substantially in registration with the side of the frame during the securing. 
     The securing element may comprise one or more frame-facing walls disposed, at least when the securing element is mounted to the frame, to restrict (i.e., by obstructing) lateral movement of the screen. 
     The filter kit may further comprise at least one cartridge detachably attachable to a side of the frame, the cartridge comprising a fine filter. 
     The frame may comprise an inlet configured for being located above the inlet of the robot and a one-way valve located at the inlet. The frame may comprise a ridge around the inlet, the one-way valve comprising a flaccid tube fastened at a proximal end thereof to the ridge and a pair of elongated members extending at least across a distal end thereof, each of the elongated members being configured to be buoyed by the movement of water along the fluid path due to operation of the robot, and to sink in the absence of such movement. 
     According to a further aspect of the present invention, there is provided a filter element for use with the filter kit as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a robot according to the present invention; 
         FIG. 2  is a bottom view of the robot illustrated in  FIG. 1 ; 
         FIG. 3  is a closeup perspective view of the robot illustrated in  FIG. 1 , with a side panel thereof removed; 
         FIG. 4  is a closeup view of part of a transmission system interfacing with an auxiliary brushwheel, both of the robot illustrated in  FIG. 1 ; 
         FIG. 5  is a perspective view of a bristle unit for use with the robot illustrated in  FIG. 1 ; 
         FIG. 6  is a partially exploded view of auxiliary brushwheels of the robot illustrated in  FIG. 1 : 
         FIGS. 7A and 7B  are exploded views of a filter unit for use with a pool cleaning robot. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     As illustrated in  FIGS. 1 and 2 , there is provided a pool cleaning robot, which is generally indicated at  10 . The exterior of the robot  10  comprises a housing  12  (which comprises a removable cover  14  with an outlet  15  formed therein, side panels  16  and a bottom panel  18 ) and a handle  20  attached thereto. The robot further comprises two main brushwheels  22 , with a pair of continuous tracks  24  spanning therebetween, and one or more auxiliary brushwheels  26  attached adjacent the bottom panel  18 . Each brushwheel is configured to rotate about a longitudinal axis of rotation R. The interior of the robot  10  comprises one or more motor units for propelling the robot, a filter unit, for trapping debris entering the robot, an impeller for generating a suction for drawing water and debris through the robot and which may be driven by one of the motor units (all not shown in  FIGS. 1 and 2 ), and other elements necessary for operation thereof. In the event that the robot  10  comprises two motor units, they may be arranged back-to-back, so that their respective shafts rotate in opposite senses. 
     The bottom panel  18  is bisected by an axis X spanning therealong between the midpoints of the two main brushwheels  22 . A pair of inlets  28  are formed therein, one between the auxiliary brush wheel  26  and each of the main brushwheel  22 , and each one being formed substantially in a different half of the bisected bottom panel  18  from the other inlet. The inlets  28  are arranged such that water and debris entering each one passes through one of the filter units before exiting through the outlet  15 . 
     As illustrated in  FIG. 3 , each of the brushwheels  22 ,  26  is formed with a plurality of bristles  30   a ,  30   b  configured for dislodging debris from surfaces of the pool while the brushwheels are spinning during use of the robot. The bristles  30   b  of the auxiliary brushwheel  26  may be different than the bristles  30   a  of the main brushwheels  22 , as will be described below. 
     Each of the main brushwheels  22  comprises a wheel gear  32  at least one of its ends, which is configured to rotate in tandem with its respective brushwheel. This may be accomplished by any appropriate means. For example, the wheel gear  32  may be formed integrally with the rest of the main brushwheel  22 , or mounted thereto with such an arrangement which allows rotation in tandem therewith, such as with a non-circular pin (not illustrated) protruding is from the main brushwheel, with the wheel gear being formed with a corresponding cavity to receive the pin. The tracks  24  are each formed with a plurality of teeth  34  configured to mesh with the wheel gear  32 . 
     As illustrated in  FIG. 4 , the auxiliary brushwheel  26  comprises an auxiliary gear  36  at least one of its ends, which is configured to rotate in tandem with the auxiliary brushwheel. This may be accomplished by any appropriate means, for example those listed above in connection with the wheel gears  32 . 
     The wheel gears  32 , auxiliary gear  36 , and tracks  24  constitute part of a main transmission system, which is illustrated in  FIGS. 3 and 4 . Besides the elements listed above, the main transmission system comprises a drive gear  38 , a two-stage compound gear  40 , and two tensioning rollers  42 . 
     The drive gear  38  is configured to rotate in tandem with the shaft of the motor unit, for example by being mounted directly thereon. It thus serves as the source of rotational motion in the main transmission system. The drive gear  38  is configured to mesh with the teeth  34  of the track  24 . The tensioning rollers  42  are configured to keep the track  24  in place meshed with the drive gear  38  and wheel gears  32 . 
     The compound gear  40  comprises a first stage  44  and smaller second stage  46 . It is disposed so that the first stage  44  meshes with the drive gear  38 , and the second stage  46  meshes with the auxiliary gear  36 . The drive gear  38 , wheel gears  32 , auxiliary gear  36 , and stages  44 ,  46  of the compound gear  40  are designed such that the angular velocity of the auxiliary brushwheel  2  greatly exceeds, for example by approximately a factor of two, the angular velocity of the main brushwheels. 
     It will be appreciated that the robot  10  is described herein and illustrated in the accompanying drawings as comprising a transmission system only on one side, it will be appreciated that, depending on the configuration of the robot, the other side may comprise a complementary transmission system. 
     For example, if the robot  10  is designed such that it comprises two independently rotating auxiliary brushwheels  26 , one each spanning substantially between the axis X and one of the tracks  24 , the complementary transmission system in be the same as the main transmission system. This arrangement ensures that when both tracks  24  are moving in the same direction, the two auxiliary brushwheels  26  rotate in the same sense. Thus, when the robot is moving in a straight line along a surface of the pool, both auxiliary brushwheels  26  are rotating in the same sense. 
     According to another example, one of the transmission systems may be altered, for example by the inclusion of an additional gear (not illustrated), to ensure that when both tracks  24  are moving in the same direction, the two auxiliary brushwheels  26  rotate in opposite senses from one another. Thus, when the robot is moving in a straight line along a surface of the pool, the auxiliary brushwheels  26  are rotating in opposite senses. This may be advantageous, for example since it allows the robot  10  to utilize, at the same time, both inlets  28  on either side of the auxiliary brushwheel  26 , resulting in a more even distribution of debris between the two filter units. 
     According to a further example, if the robot  10  is designed such that it comprises a single auxiliary brushwheel  26 , then it be designed such that it does not comprise a complementary transmission system, and it may also only comprise a single motor unit. However, the robot  10  may be provided with two motor units and a complementary transmission system, in order to provide additional power and even distribution thereof between the two tracks  24 . 
     According to any of the above examples, or any other example, the auxiliary brushwheel  26  rotates at a higher angular velocity that the main brushwheels  22 . As the brushwheels  22 ,  26  are substantially of the same diameter, there is relative motion between the periphery of the auxiliary brushwheel and the surface of the pool. Thus, the auxiliary brushwheel  26  scrubs the pool surface at a much greater relative speed than do the main brushwheels  22 , which results in more debris being dislodged than would be in the absence of the auxiliary brushwheel, or if the auxiliary brushwheel rotated at an angular velocity similar to that of the main brushwheels. 
     As illustrated in  FIG. 5 , bristle units  48  may be provided on the brushwheels, and in particular on the auxiliary brushwheel  26 . Each bristle unit  48  comprises a plurality of bristles  30 . Each bristle  30  may comprise it head  50  disposed for engagement, during use of the robot, with the surface to be cleaned of the pool, and a shaft  52 , which connects the head to its respective brushwheel or to a base strip  66  of the bristle unit  48 . Each head  50  may be connected to the base strip  66  (or the brushwheel) by two shafts  52  separated from one another by a gap  53  extending between the head and the base strip (or brushwheel). 
     The head  50  is specifically designed to facilitate in dislodging debris from the surface of the pool. As such, it may comprise several blades  54  projecting therefrom. Each blade  56  has a distal end  58  which extends substantially parallel to the axis of rotation R of its respective brushwheel. Thus, when the brushwheel rotates about the axis R, the edge  58  of each blade  56  moves along the surface of the pool and is disposed in a direction substantially perpendicular thereto. 
     The shaft  52  is designed to be rigid enough to support the head  50  and provide enough pressure between it and the surface for the blades  56  to effectively dislodge debris therefrom. At the same time, it must also be flexible enough that the bristles  30  do not affect movement of the robot, i.e., they do not substantially or perceptibly bias the robot away from the surface of the pool, especially during use thereof. 
     As illustrated in  FIG. 6 , the brushwheels, and in particular the auxiliary brushwheel  26 , may comprise a drive cylinder  60  which is directly rotated by the transmission system. The drive cylinder is formed on its perimeter surface with longitudinally extending grooves  62 . A plurality of bristle units  48  is provided. The base strip  66  of each bristle unit  48  is formed to be slid into one of the grooves  62 . The grooves  62  and base strips  66  are co-configured such that the bristle units  48  are retained within the grooves, but may be removed by a user by being slid out therefrom. An end cap  68  may be provided to prevent the bristle units  48  from sliding out of the grooves  62  during use of the robot  10 , or during any other undesired time. Such an arrangement allows a user to, e.g., replace worn-out or damaged bristles, or to replace the bristle units  48  with improved bristle units that may be developed. 
     As further seen in  FIG. 6 , in the event that the robot  10  comprises two independently rotating brushwheels  26 , a spindle  35  may be provided spanning between the two. The spindle  35  comprises a base  37  with two circular projections  39  (only one seen in  FIG. 6 ) projecting symmetrically from opposite sides thereof. Each projection  39  is rotatably received within an end of the drive cylinder  60 . This arrangement contributes to the stability of the brushwheels  26  within the robot  10 . 
     The robot  10  may comprise one or more filter units  80 , illustrated in  FIG. 7A , which allows a user to selectively choose the degree of cleaning which is performed by the robot. Typically, the robot  10  comprises one filter unit  80  corresponding to each inlet  28  thereof, although the specific construction of the robot may allow more or fewer filter units. 
     The filter unit  80  comprises a rigid frame  82  designed to be inserted via the top of the robot  10  when the cover  14  is removed, and attached to an inner side of the bottom panel  18  of the housing  12 . Thus, the filter unit  80  may be easily removed for cleaning, replacement of filter elements (as described below), and other necessary servicing thereof. 
     The frame  82  comprises a bottom panel  84  having a filter inlet  86 , a top panel  88 , and two opposing closed side panels  90  and two opposing open side panels  92 , each extending transversely between the bottom panel  84  and the top panel. The open side panels  92  are disposed opposite one another, and each is formed having a window  94  configured to allow water to pass therethrough. The bottom, top, and side panels  84 ,  88 ,  90 ,  92  define an enclosed volume (save for the filter inlets  86  and windows  94 ) therebetween. 
     Each filter inlet  86  is formed within the bottom panel  84  such that when the frame  82  is attached to the bottom panel  18  of the housing  12 , it is substantially aligned with one of the inlets  28  of the robot  10 . Thus, the enclosed volume of the filter unit  80  is in a fluid path between its associated inlet  28  and the outlet  15 . In addition, each filter inlet  86  is formed with a ridge  96  therearound, projecting upwardly into the enclosed volume. 
     The frame  82  is configured for attachment thereto of one or more filter elements which are designed for use thereof. Two or more filter elements, each of a different coarseness, are provided with the frame  82 . Each filter element may be selectively attached to and removed from the frame, depending on the intended use of the filter unit  80 . For example, a coarse filter element (i.e., designed to remove large debris, even though smaller debris may pass therethrough) and a fine filter element (i.e., designed to remove small debris) may be provided, for use, respectively, to remove large debris (e.g., at the beginning of a season when there are many large pieces of debris in the pool) and for regularly scheduled cleaning throughout the season. 
     A one-way valve, which is generally indicated at  98 , may be provided at the filter inlet  86 , attached to the ridge  96  thereof. The valve  98  may comprise a flaccid tube  100 , which is fastened at a proximal end  102  thereof to the ridge  96 , such that all debris entering the filter inlet  86  passes therethrough under influence of suction generated by the impeller. The valve  98  further comprises a pair of elongated members  104  attached to and extending along at least a distal end  106  of the tube  100 . Each of the members  104  is configured to be buoyed by the movement of water along the fluid path due to the suction generated during operation of the robot  10 , and to sink in the absence of such movement. 
     Thus, during operation of the robot  10 , the distal end  106  of the tube  100  is open, allowing water and debris to freely flow therethrough. When the suction is terminated, typically due to a cessation of operation of the robot  10 , the tube  100 , under the influence of the sinking of the elongated members  104 , collapses, preventing debris from exiting the filter unit  80  via the filter inlet  86  and be deposited on the pool surface adjacent thereto. The tube  100  may be made of a filter material, so that water can drain from the filter unit  80  via the filter inlet  86 . 
     The fine filter element  108  may be provided as a fabric-like screen which is provided so that it covers the open side panels  92  of the frame  82 . According to this arrangement, when the fine filter element  108  is mounted to the frame  82 , all unfiltered water passing through the filter unit  80  will be subject to fine filtering. A securing element  110  is provided to secure the fine filter element  108  in place. 
     The securing element  110  comprises two panes  112 , each articulated to a connecting element  114 . The panes  112  are each formed with coarse filter elements  116 . The panes  112  and the connecting element  114  are designed so that when the fine filter element  108  is in place, the securing element  110  is secured between it and the frame  82 , with the panes  112  lying in registration with the open side panels  92  thereof. In addition, locking elements  115  are provided to hold the securing element  110  in place during use. 
     The securing element  110  further comprises frame-facing walls  118 , which are disposed along the periphery thereof, and project toward the frame  82  when the securing element is mounted thereto. The walls  118  are arranged such that when the fine filter element  108  held therewithin, lateral (i.e., side to side) motion of the fine filter element is restricted, i.e., it will be prevented by the walls from sliding out of the securing element  110 . It will be appreciated that even in the absence of the walls  118 , the lateral movement of the fine filter element  108  is limited, for example by the pressure between the securing element  110  and the frame  82 , etc. 
     When coarse filtering is desired, the fine filter element  108  as removed, and the securing element  110  is used alone. When fine filtering is desired, the fine filter element  108  is replaced. In such a case, as the fine filtering is accomplished at a location which is upstream from the coarse filter element  116 , they do not perform a significant amount of filtering. 
     In addition, as illustrated in  FIG. 7B , filter cartridges  120  may be provided. The cartridges  120  comprise a rigid casing  122  housing a fine filter element  124 , and are designed so as to fit and be secured within the window  94  of one of the open side panels  92 . A similar cartridge is disclosed in WO 2007/015251 in FIGS. 8C and 8D and the accompanying description, which is incorporated herein by reference. 
     It will be appreciated that the filter unit  80  may be provided with the robot  10 , either with the filter elements attached thereto or separate therefrom, and/or it may be provided as a separate kit, and specifically configured or designed for use with one or more specific pool cleaning robots. 
     Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations and modifications can be made without departing from the scope of the invention mutatis mutandis.