Abstract:
Certain embodiments include a fluid recovery system. The fluid recovery system includes a vacuum system that applies a suction force on fluids on the floor surface to draw fluids to a fluid recovery tank. A reservoir is operably coupled to a recovery hose. The reservoir includes an inlet passage, an outlet passage leading to the recovery hose, and a fluid trap portion positioned between the inlet and outlet passages. The reservoir permits passage therethrough of fluids suctioned by the vacuum system from the floor to the recovery hose, and traps a backflow of fluids from the recovery hose in the fluid trap portion when the vacuum system stops suctioning fluids from the floor to the recovery hose. The reservoir is shaped to be generally self-cleaning and clears most fluids trapped in the fluid trap portion when the vacuum system starts suctioning fluids from the floor to the recovery hose.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. patent application Ser. No. 61/835,264, filed Jun. 14, 2013 and titled “SURFACE MAINTENANCE VEHICLE WITH SELF-CLEANING RESERVOIR THAT CAPTURES HOSE RUNOFF.” The entire content of this application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to fluid recovery systems of surface cleaning machines having a self-cleaning reservoir. 
       BACKGROUND OF THE INVENTION 
       [0003]    Floor cleaning in public, commercial, institutional and industrial buildings have led to the development of various specialized floor cleaning machines, such as hard and soft floor cleaning machines. These cleaning machines generally utilize a cleaning head that includes one or more cleaning tools configured to perform the desired cleaning operation on the floor surface. These cleaning machines include dedicated floor sweeping machines, dedicated floor scrubbing machines and combination floor sweeping and scrubbing machines. 
         [0004]    An example of a dedicated hard floor sweeping and scrubbing machine is described in U.S. Pat. No. 5,901,407, which is assigned to Tennant Company of Minneapolis, Minn. and which is hereby incorporated by reference in its entirety. The machine uses a cleaning head having two cleaning tools in the form of cylindrical brushes. The cleaning tools counter-rotate in the directions indicated by the arrows shown. Water and detergent are sprayed on the floor ahead of the brushes so the brushes can scour the floor at the same time they are sweeping debris from the floor. A vacuum squeegee removes liquid waste from the floor during the wet scrubbing and sweeping operations. The cleaning tools engage each other such that debris on the floor is swept between the two cleaning tools and is directed into a waste hopper by a deflector. 
         [0005]    An example of a dedicated floor sweeper is described in U.S. Pat. No. 4,571,771, which is assigned to Tennant Company of Minneapolis, Minn. and is hereby incorporated by reference in its entirety. The floor sweeper includes a cleaning head comprised of a rotating cylindrical brush that contacts the floor and throws loose debris into a hopper which is periodically emptied either manually or through a motorized lift. Combination floor sweeping and scrubbing machines were developed to avoid the necessity of having two machines. Some floor sweeping and scrubbing machines were created by mounting sweeping components to the front end of a dedicated scrubbing machine to making one large, multi-function machine. 
         [0006]    When a surface maintenance machine performs wet scrubbing operation, water and detergent from a solution tank are sprayed or poured on the floor through a solution valve to the brushes. As the surface maintenance machine moves forward, a squeegee wipes the waste water off the floor, and a vacuum system applies suction to remove the waste water from the floor upwards through a recovery hose and into a recovery tank. When the vacuum supply is turned off, any waste water still present in the recovery hose flows down to the floor due to lack of suction. This is referred to as hose runoff Hose runoff is typically prevented by tying a knot or including a loop in the recovery hose. 
         [0007]    Some prior art means for preventing hose runoff include a narrow water trap built on top of a vacuum squeegee. The waste water collects inside the water trap and is emptied with the assistance of jets of air created by the vacuum system. The shape of the water trap introduces swirling vortices from the air jets created by the vacuum system. These swirling vortices are deployed to remove water and debris from the water trap prior to shutting off the vacuum to prevent over flow of the water trap. The prior art water traps comprise fasteners and mounting means for the water trap on the squeegee, increasing the packaging and footprint. Additionally, the water traps mounted on the squeegee are limited by the dimensions of the squeegee, resulting in shapes that do not introduce swirling vortices of sufficient velocity to effectively remove waste water and debris from water trap. Such low velocity swirling vortices are also accompanied by large pressure losses. Designs that introduce large pressure losses in the recovery system require a larger capacity vacuum fan for drawing the same quantity of waste water in comparison to designs with lower pressure losses. Large pressure losses also translate to a higher input power to the larger capacity vacuum fan and loss of overall efficiency of the recovery system. In addition, the shape of the water trap may also allow non-uniform velocity of fluids at the inlet of the water trap resulting in “dead zones” that permit accumulation of debris. 
       SUMMARY 
       [0008]    Certain embodiments of the present invention include a floor surface maintenance machine that has a frame, a scrub head, and a fluid recovery system. In certain embodiments the fluid recovery system includes a squeegee, a recovery hose, a vacuum system and a self-cleaning reservoir. The surface maintenance machine sprays or pours water or a cleaning liquid on the surface beneath the machine, and brushes coupled to the scrub head scrub the surface. The soiled liquid is collected by the fluid recovery system. The squeegee wipes the waste water solution off the floor, which is then picked up and drawn into the recovery hose by the vacuum system. The recovery hose is coupled to the self-cleaning reservoir by hose clamps, flanges or other means. The self-cleaning reservoir is fabricated as a single part that includes an inlet passage, an outlet passage, and a fluid trap portion. The fluid trap portion is of rounded shape and has a rounded clearance above the inlet passage that allows air jets to form and move in rotational motion in the fluid trap portion. The rounded shape of the fluid trap portion, and the rounded clearance permit waste water and debris collected from the surface to be emptied out of the self-cleaning reservoir while the vacuum system is operational, ensuring that waste water does not stagnate in the recovery hose and cause hose runoff when the vacuum system is not operational. 
         [0009]    Certain embodiments of the present invention include a floor surface maintenance machine that has a frame, a scrub head, and a fluid recovery system. In certain embodiments the fluid recovery system includes a squeegee, a recovery hose, a vacuum system and a self-cleaning reservoir. The self-cleaning reservoir is fabricated as a single part that includes an inlet passage, an outlet passage, a fluid trap portion, a nose and a flow splitter. When the vacuum system is operational, waste water and debris flow from the inlet passage, and is split into two either by the shape of the fluid trap portion or by the flow splitter, or both. Two jets, a first jet flowing in a curvilinear direction away from the nose and a second jet flowing towards the nose in a rotational direction are formed. The first jet moves with a velocity much smaller than the velocity of the waste water at inlet. Any waste water and debris not removed from the self-cleaning reservoir stagnates in the reservoir and nose and will be cleaned during the next use of the surface maintenance machine. 
         [0010]    Certain embodiments of the present invention include a floor surface maintenance machine that has a frame, a scrub head, and a fluid recovery system. In certain embodiments, the fluid recovery system includes a squeegee, a recovery hose, a vacuum system and a self-cleaning reservoir. In certain embodiments, the self-cleaning reservoir comprises an inlet passage, an outlet passage, a fluid trap portion and at least one guide trough. The inlet and outlet passages can have substantial overlap to minimize footprint of the self-cleaning reservoir on the surface maintenance machine. When the vacuum system is operational, waste water and debris flow from the inlet passage to the outlet passage by following the curvature of the fluid trap portion. The curvature of the fluid trap portion introduces air jets that move in a rotational direction, facilitating movement of waste water and debris from the regions in the fluid trap portion where they tend to stagnate. The guide troughs are contoured surfaces on the walls of the self-cleaning reservoir that guide the waste water and debris to collect in the fluid trap portion when the vacuum system is not operational to be cleaned during the next use of the surface maintenance machine. The guide troughs ensure that waste water does not have a line of sight and flow from the outlet passage back to the inlet passage when the vacuum system is not operational. 
         [0011]    Certain embodiments of the present invention include a floor surface maintenance machine that has a frame, a scrub head, and a fluid recovery system. In certain embodiments, the fluid recovery system includes a squeegee, a recovery hose, a vacuum system and a self-cleaning reservoir. In certain embodiments, the self-cleaning reservoir comprises an inlet passage, an outlet passage, a fluid trap portion and an inclined portion. The inlet and outlet passages can have substantial overlap to minimize footprint of the self-cleaning reservoir on the surface maintenance machine. When the vacuum system is operational, waste water and debris flow from the inlet passage to the outlet passage by following the curvature of the fluid trap portion. The waste water and debris collected in the fluid trap portion can then be cleaned during the next use of the surface maintenance machine. The curvature of the fluid trap portion introduces air jets that move in a rotational direction, facilitating movement of waste water and debris from the regions in the fluid trap portion where they tend to stagnate. The inclined portion guides the waste water and debris to collect in the fluid trap portion when the vacuum system is not operational. The inclined portion ensures that waste water does not have a line of sight and flow from the outlet passage back to the inlet passage when the vacuum system is not operational. The inclined portion is characterized by an angle of inclination. The angle of inclination of the inclined portion determines whether waste water will collect in the fluid trap portion. 
         [0012]    Certain embodiments of the present invention include a floor surface maintenance machine that has a frame, a scrub head, and a fluid recovery system. In certain embodiments, the fluid recovery system includes a squeegee, a recovery hose, a vacuum system and a self-cleaning reservoir. In certain embodiments, the self-cleaning reservoir comprises an inlet passage, an outlet passage, a fluid trap portion and an indentation. The inlet and outlet passages can have substantial overlap to minimize footprint of the self-cleaning reservoir on the surface maintenance machine. The indentation is characterized by a radius of curvature of the indentation. When the vacuum system is operational, waste water and debris flow from the inlet passage to the outlet passage by following the curvature of the fluid trap portion. The curvature of the fluid trap portion introduces air jets that move in a rotational direction, facilitating movement of waste water and debris from the regions in the fluid trap portion where they tend to stagnate. The indentation guides the waste water and debris to collect in the fluid trap portion when the vacuum system is not operational. The indentation ensures that waste water does not have a line of sight and flow from the outlet passage back to the inlet passage when the vacuum system is not operational. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The following drawings are illustrative of particular embodiments of the invention and therefore do not limit the scope of the invention. The drawings are not necessarily to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements. 
           [0014]      FIG. 1  is an upper perspective view of an exemplary floor surface cleaning machine employing an embodiment of the self-cleaning reservoir of the present invention; 
           [0015]      FIG. 2  is a lower perspective view of an exemplary floor surface cleaning machine employing an embodiment of the self-cleaning reservoir of the present invention; 
           [0016]      FIG. 3  is an upper perspective view of a frame of the machine of  FIG. 1  and a portion of an embodiment of the self-cleaning reservoir of the present invention; 
           [0017]      FIG. 4  is a rear elevation view of a frame of the machine of  FIG. 1  and the portion of an embodiment of the self-cleaning reservoir of the present invention; 
           [0018]      FIG. 5  is an upper perspective view of a frame of a squeegee of the machine of  FIG. 1  portion of an embodiment of the self-cleaning reservoir of the present invention; 
           [0019]      FIG. 6  is a rear elevation view of a frame of a squeegee of the machine of  FIG. 1  and the portion of an embodiment of the self-cleaning reservoir of the present invention; 
           [0020]      FIG. 7  is an upper perspective view of a portion of an embodiment of the self-cleaning reservoir of the present invention; 
           [0021]      FIG. 8  is a top plan view a portion of an embodiment of the self-cleaning reservoir of  FIG. 7 ; 
           [0022]      FIG. 9  is a cross-sectional view of a portion of the self-cleaning reservoir of  FIG. 7 ; 
           [0023]      FIG. 10  is an upper perspective view of a portion of another embodiment of the self-cleaning reservoir of the present invention; 
           [0024]      FIG. 11  is a front elevation view of a portion of the self-cleaning reservoir of  FIG. 10 ; 
           [0025]      FIG. 12  is a top plan view of a portion of the self-cleaning reservoir of  FIG. 10 ; 
           [0026]      FIG. 13  is a bottom plan view a portion of the self-cleaning reservoir of  FIG. 10 ; 
           [0027]      FIG. 14  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 10 ; 
           [0028]      FIG. 15  is a top plan view of a cross-section of the self-cleaning reservoir of  FIG. 10 ; 
           [0029]      FIG. 16  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 10 ; 
           [0030]      FIG. 17  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 10  with the path of the fluids shown by arrows during operation of the vacuum system; 
           [0031]      FIG. 18  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 7  with the path of the fluids shown by arrows during operation of the vacuum system; 
           [0032]      FIG. 19  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 7  with the path of the waste water shown by arrow when the vacuum system is not in operation; 
           [0033]      FIG. 20  is a front elevation view of a portion of an embodiment of the self-cleaning reservoir of the present invention; 
           [0034]      FIG. 21  is a top plan view a portion of the self-cleaning reservoir of  FIG. 20 ; 
           [0035]      FIG. 22  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 20 ; 
           [0036]      FIG. 23  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 20  with the path of the fluids shown by arrows during operation of the vacuum system; 
           [0037]      FIG. 24  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 20  with the path of the waste water shown by arrow when the vacuum system is not in operation; 
           [0038]      FIG. 25  is an upper perspective view of a portion of another embodiment of the self-cleaning reservoir of the present invention; 
           [0039]      FIG. 26  is a front elevation view of a portion of the self-cleaning reservoir of  FIG. 25 ; 
           [0040]      FIG. 27  is a top plan view of a portion of the self-cleaning reservoir of  FIG. 25 ; 
           [0041]      FIG. 28  is an upper perspective view of a portion of another embodiment of the self-cleaning reservoir of the present invention; 
           [0042]      FIG. 29  is a front elevation view of a portion of the self-cleaning reservoir of  FIG. 28 ; and 
           [0043]      FIG. 30  is a front elevation view of a cross-section of the self-cleaning reservoir of  FIG. 28 . 
       
    
    
     DETAILED DESCRIPTION 
       [0044]      FIGS. 1 and 2  are upper and lower perspective views, respectively, of an exemplary floor surface cleaning machine  100 . Embodiments of the machine  100  include components that are supported on a motorized mobile body. The mobile body comprises a frame supported on wheels  102  for travel over a surface, on which a cleaning operation is to be performed. The mobile body includes operator controls and a steering wheel  104 , which is positioned with respect to a seat  106  of machine  100 , so that a seated operator of machine  100  may steer a front center wheel  108  of machine  100 . Machine  100  is preferably powered by one or more batteries that may be contained in a compartment beneath the seat. Alternately, the power source may be an internal combustion engine, powered through an electrical cord, or one or more power cells, may be employed to power machine  100 . 
         [0045]    Cleaning components extend from an underside of the machine  100 . For example, a scrub head  110  is shown located at a middle portion of machine  100 . The scrub head  110  has a housing that encloses two scrub brushes  114 . The brushes  114  are driven by two electric motors. An electric actuator attached between the scrub head  110  and the housing raises the scrub head  110  for transport, lowers it for work, and controls its down pressure on the floor. The scrub head  110  uses two disk scrub brushes  114  rotating about parallel vertical axes. Alternatively, scrub heads may be made with only one disk scrub brush, or one or more cylindrical brushes rotating about horizontal axes. While a scrub head  110  is depicted in the drawing figures, any appliance or tool for providing surface maintenance, surface conditioning, and/or surface cleaning to a surface may be coupled to an associated machine or vehicle in accordance with the present invention. 
         [0046]    Vehicle  100  may include a side brush assembly for cleaning a larger floor envelope. Such side brush assemblies make it easier to clean near walls or other obstacles without damaging the machine or the wall while at the same time widening the cleaning path of the machine to increase productivity. 
         [0047]    During wet scrubbing operations, water or a cleaning liquid contained in a tank  118  is sprayed to or poured on the surface beneath machine  100 , in proximity to the scrub head  110 . Brushes  114  scrub the surface and the soiled cleaning liquid is then collected by a fluid recovery system and deposited in a waste recovery tank  120 . One embodiment of the fluid recovery system of the machine  100  includes a vacuum squeegee mounted adjacent the rear end of the machine  100  on a frame  122  that supports the squeegee. The vacuum squeegee also includes a vacuum port that is placed in vacuum communication with a vacuum fan. The vacuum fan operates to remove liquid and particle waste collected by the vacuum squeegee for deposit in the waste recovery tank  120 . 
         [0048]    In alternate embodiments, the floor surface maintenance machines  100  may be combination sweeper and scrubber machines. In such embodiments, in addition to the elements describe above, the machines  100  may also include sweeping brushes and a hopper extending from the underside of the machine  100 , with the sweeping brushes designed to direct dirt and debris into the hopper. Alternatively, the machine  100  may be designed for use by an operator that walks behind the machine, or the machine may be configured to be towed behind a vehicle. 
         [0049]      FIG. 3  is an upper perspective view of the machine  100  and a portion of the fluid recovery system.  FIGS. 4 ,  5  and  6  are front elevation, perspective and rear elevation view of portions of the fluid recovery system. In  FIGS. 3-6 , several components of the machine are omitted for clarity. The fluid recovery system comprises a squeegee  124  supported on the frame  122  (best seen in  FIGS. 1 and 2 ). A vacuum port (not shown) is placed in communication with a vacuum fan (not shown). When the vacuum fan is operational, it creates suction inside the recovery hose  130 , collecting the liquid and particle debris from the surface. A self-cleaning reservoir  400  is coupled to the recovery hose  130  by employing hose clamps, flanges or other means of coupling. 
         [0050]      FIG. 7  is an upper perspective view of the self-cleaning reservoir according to some embodiments. The self-cleaning reservoir comprises an inlet passage  410 , guide troughs  440 , a fluid trap portion  420 , and an outlet passage  430 . The self-cleaning reservoir may be fabricated as a single part facilitating the assembly of the self-cleaning reservoir on to the recovery hose. For instance, the inlet passage,  410 , the fluid trap portion  420  and the outlet passage  430  can be formed integrally (e.g., by molding). Alternatively, the self-cleaning reservoir may be assembled from a plurality of pieces. For instance, the inlet passage  410 , the fluid trap portion  420  and the outlet passage  430  may be separate pieces operatively connected (e.g., adhesives, fasteners, complementary threads etc.) to each other to form the self-cleaning reservoir. The inlet and outlet passages  410  and  430  are illustrated as having a circular cross-section. The shape of the inlet and outlet passages can be adapted to engage with a recovery hose or other water flow passageways. When the vacuum fan is operational, a suction force is created in the reservoir hose, resulting in movement of waste water on the inside area of the inlet passage  410 . It is preferable to have sufficient clearance for the inlet passage  410  below the fluid trap portion  420  to allow the flow velocity to be nearly uniform at the inlet passage  410 . Additionally, it is preferable to have a rounded contour immediately above the inlet passage  410  to allow the flow velocity to be nearly uniform. As illustrated in  FIG. 9 , the inlet passage extends a distance “r” into the self-cleaning reservoir forming a barrier in the fluid trap portion  420  ensuring that any waste water and debris collected in the fluid trap portion does not flow into the inlet passage  410 . The fluid trap portion  420  has a rounded profile so that it does not act as a sharp corner to the fluids entering the self-cleaning reservoir, to prevent the fluids from slowing down at the sharp corner, thereby allowing the velocity of fluids to remain uniform at the inlet passage  410 . As best seen in  FIGS. 8 and 9 , the inlet passage  410  and the outlet passage  430  overlap. A distance “x” indicates the extent of the overlap of the inlet and outlet passages  410  and  430 . As shown in  FIG. 9 , “x” is the distance between the walls of the inlet and the outlet passages  410  and  430  respectively. It may be appreciated that the walls of the inlet passage is approximately parallel to those of the outlet passage. In certain preferred embodiments, “x” can be as low as zero. The low-profile design of this embodiment with substantial overlap of the inlet and outlet passage provides a compact footprint of the self-cleaning reservoir  400 . 
         [0051]    When the vacuum fan is non-operational, the suction force is no longer available in the reservoir hose, resulting in a tendency for the waste water to move in a downward direction. A substantial overlap of the inlet and outlet passages  410  and  430  may cause the waste water to flow from the outlet passage  430  to the inlet passage  410 . The guide troughs  440  prevent this tendency of the flow by guiding the flow of waste water towards the fluid trap portion  420 . The waste water flows downward along the walls of the guide trough, and so it does not have a clear line of sight despite a substantial overlap of the inlet and outlet passages  410  and  430 . The rounded contour of the walls of the fluid trap portion  420  and the presence of the guide troughs  440  direct the waste water towards the fluid trap portion  420 . Collected waste water and debris in the fluid trap portion can then be cleaned during the next use of the surface maintenance machine by the vacuum system. 
         [0052]      FIGS. 10-13  show different views of a self-cleaning reservoir  500  according to another embodiment. The self-cleaning reservoir  500  includes an inlet passage  510 , an outlet passage  530 , a fluid trap portion  520 , and a nose  522 . The self-cleaning reservoir may be fabricated as a single part facilitating the assembly of the self-cleaning reservoir on to the recovery hose. The inlet and outlet passage  510  and  530  are operably coupled with a recovery hose (not shown) of a surface maintenance machine by deploying flanges, hose clamps or other similar means. The shape and size of the inlet and outlet passage  510  and  530  can be chosen to allow uniform velocity of the waste water at the inlet passage. The fluid trap portion  520  and the nose  522  have a rounded profile to avoid sharp corners for the incoming fluid, because a sharp corner causes the fluids to slow down and create a large pressure loss in the self-cleaning reservoir. The fluid trap portion  520  has a clearance “c” above the inlet passage  510 . The clearance “c” allows for uniform velocity at fluids at the inlet passage  510 . Some embodiments include a flow splitter  524 , as shown in  FIG. 14 . The flow splitter can be included with the self-cleaning reservoir  400  by mechanical means, or by contouring the walls of the fluid trap portion  420  and  520 . The flow splitter  524  facilitates the flow through the inlet passage  510  to be divided into two jets, a first jet away from the nose  522  and a second jet toward the nose  522 . 
         [0053]    During operation, a vacuum system is engaged to provide suction force in the recovery hose. Waste water travels through the recovery hose and enters the inlet passage  510  of the self-cleaning reservoir  500 . The rounded profile of the nose  522  and fluid trap portion  520  and the flow splitter  524  acts to split the incoming fluids from the inlet passage  510  into two jets. In some other embodiments, the fluids entering the inlet passage  510  are split without the flow splitter  524 . A first jet  560  comprising fluids moving away from the nose  522 , and a second jet  570  comprising fluids moving toward the nose  522 . The first jet  560  may additionally be split by the shape of the nose into additional secondary jets as shown in  FIG. 15 . Any fluid that does not move towards or away from the nose  522  in the direction of the first jet  560  and the second jet  570  flow along the sides, as indicated by arrows “s”.  FIG. 16  is a cross-section view of the self-cleaning reservoir  500  that shows the direction of movement of the first and second jets  560  and  570 . The first and second jets  560  and  570  in this embodiment have a rotational direction “e” and “f”. 
         [0054]      FIG. 17  shows the direction of movement of fluids through the self-cleaning reservoir  500 . The direction of motion of the fluids is indicated by arrows, and is obtained by Computational Fluid Dynamics simulation of fluid flow through the self-cleaning reservoir  500 . Fluids, such as air moving in the recovery hose due to suction, or waste water enter the inlet passage  510  of the self-cleaning reservoir  500 . The inlet passage  510  is of cylindrical shape. The constant cross-sectional area, combined with a clearance “c” below the fluid trap portion  520  and the nose  522  provide allow fluids to be drawn inside the self-cleaning reservoir uniformly by applying suction force, resulting in a nearly uniform velocity of flow at inlet. The fluids travel in an upward direction through the inlet passage  510 . The flow splitter  524 , or the rounded shape of the fluid trap portion  520  and nose  522 , or both cause the fluids from the inlet passage to be divided into the first jet  560 , that moves in a first direction “e”, with a first speed, and the second jet  570  that moves in a second direction “f” with a second speed. The first jet  560  does not have a substantially rotational motion, as shown in  FIG. 17 , because the distance between the rounded portion of the reservoir  520  and the inlet passage  510 , shown by “a” in  FIG. 17  is larger than the distance between the rounded portion of the nose  522  and the inlet passage  510 , shown by “b” in  FIG. 17 . This larger distance facilitates the first jet  560  to not move in a substantially rotational direction, but rather move in a curvilinear direction “e”, bend in an upward direction and move towards the outlet passage  530 . 
         [0055]    The first speed of the first jet  560  is substantially higher than the second speed of the second jet  570 , because the distance “a” is larger than the distance “b”. The shorter distance for the fluid to flow and the presence of the nose  522  creates an obstruction to the fluid flow path, causing the first speed of the first jet  560  to be higher than the second speed of the second jet  570 . This lower value of the second speed prevents effective removal of water and debris from the nose, as fluids and debris tend to stagnate in the nose  522 . The first jet  560  moves in a first direction with a first speed much larger than the second speed. As a result of higher speed of the first jet in comparison to the second jet, the fluids moving in the first direction “e” have greater momentum and bend in an upward direction and flow out of the outlet passage  530 , thus emptying the self-cleaning reservoir  500 . 
         [0056]    In some preferred embodiments, such as the self-cleaning reservoir  400 , the nose is eliminated to facilitate better removal of waste water and debris.  FIG. 18  shows the path of fluids through the self-cleaning reservoir  400 . The direction of motion of the fluids is indicated by arrows, and is obtained by Computational Fluid Dynamics simulation of fluid flow through the self-cleaning reservoir  400 . Fluids, such as waste water or air from suction of the vacuum fan flow through the inlet passage  410  of the self-cleaning reservoir  400 . The rounded shape of the fluid trap portion  420  and the clearance “t” below the fluid trap portion  420 , draw the fluid in an upward direction uniformly by eliminating a sharp corner for the fluid from the inlet passage. As the fluids move upwards into the fluid trap portion, the rounded shape of the fluid trap portion  420  causes the fluids to move in a curvilinear direction “y”. The fluid stream substantially conforms to the shape of the fluid trap portion  420 . The curved section  426  of the fluid trap portion  420  causes any fluid in this region to move with a velocity much lower than the velocity of the fluids at inlet passage  420 . As a result, some of the waste water and debris may not have a tendency to move upwards towards the outlet passage  430 . Any waste water and debris that do not move out of the curved section  426  fall back into the inlet passage  410 , where they are pushed by the incoming stream of air from the suction caused by the vacuum fan and move upwards towards the outlet passage, thus precluding the need to manually empty the self-cleaning reservoir to remove accumulated waste water and debris. 
         [0057]    When the vacuum system is not operational, any waste water and debris that has not been drawn into the recovery tank travels in a downward direction, assisted by gravitational force through the recovery hose, and into the outlet passage  430  of the self-cleaning reservoir  400 . The guide troughs  440  are contoured with a relatively large radius of curvature relative to the cross-section of the volume of suctioned fluid flow. If the quantity of water and debris that fall in a downward direction is not substantially large relative to the volume of suctioned fluid flow, the waste water and debris follow a curvilinear path of motion as indicated by “d” in  FIG. 19 , the curvilinear path of motion conforming to the contour of the guide trough due to a phenomenon known as Coanda effect. 
         [0058]      FIGS. 20-24  illustrate alternate embodiments of the self-cleaning reservoir  600 . In this embodiment, the self-cleaning reservoir  600  includes an inlet passage  610 , an outlet passage  630 , a nose  622  and a fluid trap portion  620 . The self-cleaning reservoir may be fabricated as a single part facilitating the assembly of the self-cleaning reservoir on to the recovery hose. As shown in  FIGS. 21 and 22 , the inlet and outlet passages have an overlap distance “x”. The overlap “x” is the distance between the walls of the inlet and the outlet passages  610  and  630 . In some preferred embodiments, the overlap distance “x” can be zero, implying that the inlet and outlet passages  610 ,  630  do not have a line of sight. The inlet passage  610  extends a distance “g” into the fluid trap portion  620 , to form a barrier between the fluid trap portion  620  and the inlet passage  610  to prevent the fluids collected in the fluid trap portion from flowing outwardly to the inlet passage  610 . The fluid trap portion  620  has a rounded profile to avoid a sharp corner against which fluids from the inlet passage  610  may slow down. 
         [0059]      FIG. 23  shows the direction of movement of fluids through the self-cleaning reservoir  600 . The direction of motion of the fluids is indicated by arrows, and is obtained by Computational Fluid Dynamics simulation of fluid flow through the self-cleaning reservoir  600 . When the vacuum system is operational, waste water and debris travel upwards through the inlet passage  610 . The rounded shape of the fluid trap portion  620  allows the waste water and debris to move in a curvilinear path as indicated in  FIG. 23 . The rounded shape of the nose  622  and its proximity to the inlet passage  610  defined by distance “h” introduces motion of waste water and debris in a rotational direction “z” as indicated by the arrows at velocities much lower than the velocity of waste water at inlet and outlet passages  610  and  630 . As a consequence, waste water and debris tend to stagnate at the nose  622 . When the vacuum system is not operational, waste water and debris from the outlet passage  630  flow towards the nose  622  along a curvilinear path indicated by the arrow “j” in  FIG. 24 , the curvilinear path conforming to the contour of the self-cleaning reservoir  600  due to a phenomenon known as Coanda effect. 
         [0060]      FIGS. 25-27  show the self-cleaning reservoir  700  according to another embodiment. In this embodiment, the self-cleaning reservoir comprises an inlet passage  710 , a fluid trap portion  720 , an inclined portion  728  and an outlet passage  730 . The self-cleaning reservoir may be fabricated as a single part facilitating the assembly of the self-cleaning reservoir on to the recovery hose. The fluid trap portion has a rounded profile to allow uniform velocity at the inlet passage  710  by eliminating sharp corners and accompanying pressure losses in the self-cleaning reservoir. The inlet and outlet passages are shown having circular cross-section, and have a common axis. The overlap of the inlet and outlet passages is substantial, but waste water and debris do not have a line of sight as illustrated in  FIG. 27 . The angle of inclination of the inclined portion with respect to the vertical axis is indicated by “θ” in  FIG. 26 . Waste water and debris will flow from the outlet passage  730 , along the walls of the inclined portion  728  and into the fluid trap portion  720  when the vacuum system is not operational. Increasing the angle of inclination θ of the inclined portion from the vertical direction increases the likelihood of waste water and debris collecting in the fluid trap portion  720 , rather than flowing from the outlet passage  730  to the inlet passage  710 . 
         [0061]      FIGS. 28-30  illustrate the self-cleaning reservoir  800  according to another embodiment. The self-cleaning reservoir comprises an inlet passage  810 , an outlet passage  830 , a fluid trap portion  820  and an indentation  826 . The self-cleaning reservoir may be fabricated as a single part facilitating the assembly of the self-cleaning reservoir on to the recovery hose. The recovery hose may be coupled to a vacuum system with a vacuum fan that draws waste water and debris into the inlet passage  810 . The inlet passage  810  and the outlet passage  830  overlap. A distance “x” indicates the extent of the overlap of the inlet and outlet passages  810  and  830 . The walls of the inlet passage  810  extends a distance “k” into the fluid trap portion to form a barrier that prevents waste water and debris contained in the fluid trap portion  820  from flowing outwardly into the inlet passage  810 . The indentation is characterized by a radius of curvature “l”. The rounded shape of the fluid trap portion  820  avoids a sharp corner for the fluids flowing into the fluid trap portion and introduces a curvilinear path for the waste water from the inlet passage to the outlet passage. The indentation  826  causes waste water pressure at the outlet passage  830  to be lower than that at the inlet passage  810 . When the vacuum system is not operational, water from the outlet passage  830  follows the contour of the self-cleaning reservoir. The indentation  826  introduces a curvilinear path as indicated by the direction “m” in  FIG. 30  because of the radius of curvature “l”, causing the waste water to collect in the fluid trap portion  820 . A larger radius of curvature “l” translates to a greater likelihood for the waste water to flow into the fluid trap portion  820 . 
         [0062]    Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is, therefore, not limited to the specific details, representative apparatus and illustrative examples shown and described. Accordingly, departures from such details may be made without departing from the spirit or scope of the applicant&#39;s general inventive concept.