Patent Publication Number: US-2007119448-A1

Title: Range hood cleaning assembly

Description:
FIELD OF THE INVENTION  
      This invention relates to range hoods, and more particularly to a cleaning assembly for a range hood wherein compressed air directs accumulated grease accumulated within the range hood to an external grease receptacle.  
     BACKGROUND OF THE INVENTION  
      Range hoods are used above cooking surfaces to remove grease, common odors and hazardous gases created during the cooking process. Typically, range hoods have a pair of motors horizontally installed in a motor housing within the hood body. Each motor drives a fan. The fans suck air from the cooking area below and force it through the motor housing to ventilation piping.  
      As the vaporized grease contained in the entrained air travels through the motor housing, some of it condenses on the inside walls of the housing from where the shaping of the walls and floor of the housing directs the grease to a circular grease catcher mounted below each fan opening. Grease catchers are known in the art as illustrated in U.S. Pat. Nos. 6,216,686 B1 and 5,537,988.  
      Grease catchers are also adapted to capture any grease that drips off the fan blades when the motors are turned off. Typically, the grease catcher has radial inner and outer trays with a wall separating them. The wall extends vertically so as to be almost flush with the lower edge of the outer circumference of the fan. In this way air being drawn in by the fans is compelled to enter the motor housing rather than the hood body. The wall therefore acts to control the air currents of the range hood.  
      The grease catchers are usually provided with an inclined base or floor, so as to direct accumulated grease to a hole in the floor. A hose is attached to the hole to convey the grease to a grease receptacle outside the range hood.  
      The motor housing and grease catchers are mounted within the hood body. Openings in the lower surface of the hood body are positioned so as to match those of the motor housing. Typically the lower surface of the hood body is removably fitted into the main hood body. A protective grill is attached to the outside of each opening in the hood body so as to prevent the insertion of body parts when the fan is in operation.  
      Alternatively, as set out in my U.S. and Canadian patent applications, numbers 10/035,116 and 2,365,790 respectively, the motor housing may be adapted to act as a grease catcher itself. In this system, a circular wall defining the motor housing intake openings projects vertically into the motor housing, acting as a barrier to grease accumulated therein. The accumulated grease drains directly from the housing rather than to a grease catcher. Grease trays inserted into the intake openings provide a barrier for proper airflow into the housing and to capture any grease that should happen to drip from the fan when it has stopped motion.  
      Both of the foregoing designs rely on gravity to cause the accumulated grease to drain out of the range hood. However, gravity is not effective in removing all the grease with the result that some becomes caked on to the interior surfaces, thereby reducing the efficiency of the range hood and creating a possible fire hazard.  
      The foregoing systems of motor housing and grease catchers therefore require periodic cleaning to remove condensed grease accumulated on the fans, motor housing interior and grease trays. In order to clean the interior of the range hood, a user must first remove the lower surface of the hood body, following which the grease catcher must then be removed. This can be quite awkward and is difficult for those without the strength to support the weight of the lower surface. Washing the inside of the motor housing, the fans and the grease trays to remove the accumulated grease is also time consuming.  
      Attempts have been made to overcome the necessity to manually clean the interior of a range hood exhaust system. It is known in the art to provide a washing fluid under pressure in order to clean the interior of the exhaust system. For example, U.S. Pat. No. 4,259,945 teaches an exhaust system in which a washing fluid under pressure is used to clean the flue and fan. Similar washing fluid systems are taught in U.S. Pat. Nos. 3,795,181 and 4,085,735.  
      A similar approach is known in the art with respect to the range hood design described above. A fluid delivering nozzle is fitted into a hole in the side of the motor housing so as to deliver a spray of washing fluid to clean the interior. This is done while the motors are activated so that the force of the air being drawn into the motor housing forces the sprayed fluid against the interior surfaces of the motor housing and prevents any liquid from passing through the air intakes.  
      While these prior art systems reduce the amount of cleaning required of the exhaust system, maintenance is still required. Because there is so much waste fluid resulting from the combination of the grease and the washing solution, a large waste fluid receptacle is required and must be emptied often. The waste receptacle takes up usable space below the range hood and is not pleasing to the eye. In addition, the washing fluid receptacle must be constantly refilled.  
      It is therefore an object of an embodiment of the present invention to provide a range hood in which the interior of the range hood, including the motor housing and the fans, may be automatically cleaned without the use of washing fluid so as to negate the need for a large waste fluid receptacle or the constant refilling of a washing fluid receptacle.  
      Various aspects of the invention address these objects, but not all aspects of the invention necessarily address all such objects simultaneously. Other objects of the invention will be apparent from the description that follows.  
     SUMMARY OF THE INVENTION  
      The invention is directed to a cleaning assembly for use in a range hood. According to one aspect of the invention, a plurality of air dispensers are used to direct compressed air against the grease laden surfaces of the range hood including the fan(s), the interior surfaces of the motor housing and, if applicable, the grease tray(s), thereby directing any accumulated grease out of the range hood.  
      In the preferred embodiment, the range hood has a motor housing encasing two motors, each motor contained within a separate chamber of the motor housing and driving a respective fan. At least one source of compressed air, such as an air compressor, acts to drive compressed air through air dispensers, the compressed air acting to force accumulated grease out of the range hood.  
      Preferably, the air dispensers will comprise air hoses with directional nozzles, however any suitable means of delivering compressed air is satisfactory; for example, hollow, rigid tubes or conduits.  
      Preferably, a plate is attached about the base of each motor, such that a portion of each of the motors is bordered by a plate. A space is present between the plate and the upper surface of the motor housing. A plurality of air dispensers is attached to each plate and is positioned between the plate surface and the upper surface of the motor housing. Compressed air is directed through each air dispenser such that it is directed against the upper surface of the motor housing. The air dispensers dispense the compressed air over a wide angle. In the preferred embodiment, four hoses and nozzles are attached to the plate. However, this number can be varied to provide different levels of cleaning efficiency. While it is preferred that the plate be circular, it need only be shaped so as to fit around the motor and to provide a surface upon which to mount the air dispensers and could for example be star-shaped or scalloped.  
      The compressed air forced against the upper surface of the motor housing drives any accumulated grease down the side of the interior to the lower surface of the motor housing where it drains to an outer grease receptacle.  
      In the preferred embodiment, intake openings in the lower surface of the housing are formed by walls that project into the interior of the motor housing (one for each chamber). An extension extends from the wall into the opening and in a downward direction so as to form a gap between the extension and the wall. The housing is shaped so as to direct any accumulated liquid or debris within the housing, such as grease, towards a drainage hole in the lower surface of the housing where the liquid is directed out of the range hood. An additional air dispenser is mounted in the side of the motor housing and acts to force liquid accumulated on the lower surface of the motor housing towards the drainage hole. The intake opening walls prevent any liquid from passing back through the intake opening.  
      Two further air dispensers are attached to the underside of the lower surface of the motor housing, one travelling towards each of the intake openings. These air dispensers direct compressed air travelling through them towards the blades of the fan mounted above each respective intake opening.  
      In one aspect the cleaning assembly is for use in a range hood comprising a motor housing having an interior defined by upper, lower and side surfaces containing at least one motor and at least one fan and having at least one drain hole. The cleaning assembly comprises at least one source of compressed air located externally to the motor housing and a plurality of air dispensers for delivering the compressed air to the motor housing interior.  
      In another aspect, the air dispensers direct the compressed air against at least one of the interior surfaces of the motor housing.  
      In another aspect the cleaning assembly further comprises a plate releasably attachable to the motor housing about the motor and above an upper surface of the fan such that there is a space between the plate and the motor housing.  
      In another aspect at least a first one of the air dispensers is mounted to the plate in the space.  
      In another aspect the air dispensers direct compressed air from the source of compressed air against the upper surface of the motor housing interior.  
      In another aspect a second one of the plurality of air dispensers is releasably attachable to the lower surface of the motor housing and directs compressed air from the source of compressed air against the at least one fan.  
      In another aspect at least a third one of said plurality of air dispensers is integral with the side of the motor housing, the third one of the air dispensers being positioned within the motor housing interior above a top side of the lower surface of the motor housing.  
      In another aspect the third one of the air dispensers directs compressed air from the source of compressed air against the top side of the lower surface of the motor housing.  
      In yet a further aspect the cleaning assembly according to the invention is for use in a range hood comprising a motor housing having an interior defined by upper, lower and side surfaces containing at least one motor and at least one fan, and a grease tray. The grease tray is releasably attachable to the motor housing and comprises an opening, first, second and third tray walls extending around the opening, a first trough formed between the first and second tray walls, a second trough formed between the second and third tray walls, and at least one drainage hole. The cleaning assembly comprises at least one source of compressed air located externally to the motor housing and a plurality of air dispensers for delivering the compressed air to the interior.  
      In another aspect a first of the plurality of air dispensers is integral with the first, second and third tray walls.  
      In another aspect the first of the air dispensers directs compressed air from the source of compressed air against the at least one fan.  
      In another aspect at least a second one of the plurality of air dispensers is integral with the first tray wall, the second one of the air dispensers directing compressed air from the source of compressed air into the first trough.  
      In yet a further aspect the invention comprises range hood cleaning assembly wherein the range hood has a motor housing having upper, lower and side surfaces that generally defines an enclosure containing at least one motor and at least one fan. The lower surface has at least one intake opening and at least one drain hole. A wall depending from the lower surface and projecting into the interior of the enclosure defines the intake opening. A tray is releasably connectable to the intake opening. The tray comprises an opening, first and second tray walls extending around the opening, and a floor between the first and second tray walls. The cleaning assembly comprises at least one source of compressed air located externally to the motor housing and a plurality of air dispensers for delivering the compressed air within the range hood.  
      In another aspect a second one of said plurality of air dispensers is releasably attachable to the lower surface of the motor housing. The second one of the air dispensers directs compressed air from the source of compressed air against the at least one fan. The first and second tray walls have a gap in which the second one of the air dispensers may be fitted when the tray is releasably connected to the intake opening.  
      In another aspect a second of said plurality of air dispensers is releasably attachable to the tray, the second air dispensers directing compressed air from the source of compressed air against the at least one fan when the tray is releasably connected to the intake opening.  
      In another aspect the air dispensers comprise air hoses and nozzles, each air hose having a first end connectable to the source of compressed air and a second end releasably connectable with a respective one of the nozzles.  
      In yet a further aspect the invention comprises a cleaning assembly for use in a range hood comprising a motor housing having an interior defined by upper, lower and side surfaces containing at least one motor and at least one fan and having at least one drain hole. The cleaning assembly comprises at least one source of compressed air, a plurality of air hoses wherein each of the plurality of air hoses having a first and second end, a plurality of nozzles wherein at least one nozzle is releasably connected to each of the first ends and each of the second ends are releasably connected to the source of compressed air.  
      In yet another aspect the nozzles direct compressed air from the source of compressed air against at least one of the interior surfaces of the motor housing whereby to dislodge grease and debris from the at least one interior surfaces.  
      Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiment and to the claims that follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be described by reference to the detailed description of the preferred embodiment and to the drawings thereof in which:  
       FIG. 1  is a sectional view of a range hood according to the preferred embodiment of the invention with the right hand portion of the figure providing a deeper sectional view than the left hand portion of the figure;  
       FIG. 2  is a view taken along line  2 - 2  of  FIG. 1 ;  
       FIG. 3  is an exploded sectional view of portions of the range hood of  FIG. 1 ;  
       FIG. 4  is a sectional view of a range hood according to an alternative embodiment of the invention with the right hand portion of the figure providing a deeper sectional view than the left hand portion of the figure;  
       FIG. 5  is an exploded sectional view of portions of the range hood of  FIG. 4 ;  
       FIG. 6  is a sectional view of a further alternative embodiment of a range hood according to the invention with the right hand portion of the figure providing a deeper sectional view than the left hand portion of the figure;  
       FIG. 7  is a plan view of the grease tray of the range hood of  FIG. 6 .  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      The present invention relates to a cleaning assembly for a range hood.  
      The cleaning assembly is composed of a source of compressed air such as a compressor and air dispensers for directing the compressed air against grease coated surfaces within the range hood. The compressed air is used to drive accumulated grease out of the range hood. This will be described in greater detail below by reference to the preferred and alternative embodiments.  
      The preferred embodiment of a range hood  100  with a cleaning assembly according to the invention is illustrated in  FIG. 1 . In the preferred embodiment, the motor housing  110  includes an integral grease catcher. The housing  110  defines an enclosure and is mountable within a further enclosure formed by the hood body generally indicated by the numeral  102 . The interior of the housing  110  is coated with a non-stick material so as to facilitate grease removal and is separated into two substantially similar, separate chambers  2 ,  4  as best illustrated in  FIG. 2 . The chambers  2 ,  4  have intake openings  112  shown in  FIG. 3 , and ventilation holes (not shown). The ventilation holes project through the upper surface of hood body  102  when the housing  110  is attached to the interior of the hood body  102 .  
      Two motors  125  fit within the motor housing  110  and are attached to the inside of the upper surface of the hood body  102 , one in each of chambers  2  and  4 . Fans  120 , of the semi-impeller type, one secured to each of the motors  125  by fan caps  129 , act to draw grease-laden air into the motor housing  110  and out the ventilation holes. A plate, preferably shaped as a circular disc  8  is attached about the base of each of the motors  125  such that there is a space between plate  8  and the upper surface of the interior of motor housing  110 . Preferably, the plate  8  has a maximum radius that is approximately equal to the maximum radius of the fans  120 , the plates  8  being positioned just above the upper surface of the fans when they are installed in the motor housing  110 . The plate acts to prevent the air dispensers from coming into contact with any moving parts, such as the fans  120 , within the motor housing. The fans  120  and plate  8  are dimensioned so as to be removable from within the housing  110  through openings  112 .  
      The motors  125  are positioned within the motor housing so that when the fans  120  are attached they are positioned above intake openings  112  (of the motor housing  110 ) and air inlets  109  (of the lower panel  108 ), best shown in  FIG. 3 . The design of the motor housing  110  is such that when the fan is in position, the distance between the fan and the side wall of the motor housing increases in the direction of rotation of the fan, the space being the largest in the area of the ventilation holes, thereby maximizing air flow. This is best illustrated in  FIG. 2 . In the preferred embodiment the fans are counter-rotating as indicated by arrows  6 ,  7  in  FIG. 2 . However, the cleaning assembly is designed to work with alternative configurations such as where the fans rotate in the same direction.  
      As shown in  FIG. 3 , openings  112  in motor housing  110  have walls  130  depending and rising vertically from the lower surface of the motor housing. An outwardly and downwardly projecting extension or lip  132  depends from wall  130 , so as to form a gap  134  between the lip  132  and wall  130 . Extension  132  may diverge from wall  130  such that gap  134  forms a wedge surface. A tray  140  is dimensioned such that its outer wall  142  may be releasably connected to gap  134 . This is discussed in greater detail below.  
      The lower surfaces of the chambers  2 ,  4  of the motor housing  110  are each shaped such that any accumulated grease or other condensed liquid (condensate) is directed by gravity towards the respective drain holes  123 ,  124  (see  FIGS. 1, 2 ). Holes  123 ,  124  are therefore located at the lowest point of lower surface  118  of the motor housing. As seen in  FIG. 3 , drainage hoses  127 ,  128  are attached to each of holes  123  and  124 . Accumulated condensate travels through drainage hoses  127 ,  128  by way of gravity to external grease cups  126  (only one of which is shown in  FIG. 1 ).  
      Wall  130  acts as a barrier to any condensate which accumulates in the interior of the motor housing, preventing it from dripping through openings  112 .  
      Using chamber  2  as an example, air dispensers of the cleaning assembly, preferably four air hoses  12 ,  14 ,  16  and  18  are attached to the upper surface of plate  8  as shown in  FIGS. 1, 2  and  3 . This configuration is mirrored in chamber  4 . Depending on the size of the range hood and the dispersion characteristics of the air hoses and nozzles, less than or more than four air hoses could be used. At the end of each of air hoses  12 ,  14 ,  16  and  18  is a nozzle  20 . The nozzles  20  are approximately equally spaced about the outer circumference of, and firmly attached to plate  8 . The air hoses  12 ,  14 ,  16  and  18  pass through a hole in the motor housing and are attached to at least one air compressor (not shown). Preferably the hoses  12 ,  14 ,  16  and  18  are collected within rubber covering  24  as shown in  FIG. 2 , however this need not be the case. It is also contemplated that air hoses  12 ,  14 ,  16  and  18  could connect to a larger hose by way of a multi ended adapter or simply pass through the wall of the motor housing individually provided solely that each hose is connected at one end to a compressor and at the other end to a nozzle  20 . A plastic or rubber gasket seal (not shown) similar to that employed with respect to the power cord  50  of the motor  125  may be used to prevent any air from escaping from the motor housing where the air dispensers pass through, however anything preventing air from passing through is satisfactory. It is also contemplated that the air hoses  12 ,  14 ,  16  and  18  could be combined with the power cord  50  such that they pass through the motor housing wall together.  
      When in operation, compressed air travels through air hoses  12 ,  14 ,  16  and  18  to nozzles  20 , which widely disperse compressed air from the air compressor radially outward against the upper surface of the motor housing. This compressed air then follows the contours of the interior of the housing chambers, such that accumulated condensate in each chamber is directed from the upper surface and down the sides towards the lower surface  118  where it is prevented from passing back through openings  112  by walls  130  in troughs  150  formed between wall  130  and the side wall of the motor housing.  
      Further air dispensers act to direct grease along the bottom surface towards the drainage holes  123 ,  124 . This is accomplished by way of integrated nozzles  42 ,  44  in the motor housing  110  to which air hoses  26 ,  28  may be releasably attached as shown in  FIG. 2 . Air hoses  26 ,  28  are also attached to a source of compressed air such as an air compressor. While only one integrated nozzle  42  or  44  is shown in each of chambers  2  and  4 , it is contemplated that further integrated nozzles could be spaced about the perimeter of the motor housing should greater grease dispersing power be required. Integrated nozzles  42 ,  44  are positioned within troughs  150  so as to direct a wide spray of compressed air against the lower surface of the motor housing in the respective direction of rotation  6 ,  7 . Air follows troughs  150  forcing condensate around the perimeter of walls  130  towards drainage holes  123 ,  124 . Condensate entering the drainage holes  123 ,  124  travels to external grease cups  126  by way of drainage hoses  127 ,  128 .  
      As illustrated in  FIGS. 1, 2  and  3 , for each compartment the air cleaning assembly also includes a further air hose  162  connected at one end to nozzle  160  and at the other end to an air compressor. The nozzle  160  is positioned so as to direct compressed air from the air compressor against the fans  120  so as to force grease accumulated on the fans  120  into the compartments  2 ,  4 . The nozzle  160  is releasably connectable to the bottom of the motor housing. In this way, it can be disconnected in order to allow the fan, motor or plate to be removed from the interior of the motor housing. Once connected to the motor housing, hose  162  may be releasably attached to the nozzle by way of clip  290  or other means.  
      The tray  140  while also being releasably connectable to housing  110 , also connects to the lower panel  108 , which is removable from the remainder of main hood body  102 . Lower panel  108  has a pair of air inlets  109 , one of which is shown in  FIG. 3 . Air inlets  109  are defined by circular vertical walls  101 , which depend, and rise vertically from, lower surface  108 . The circular vertical walls  101  can vary in height between a minimum height and a maximum height. The minimum height is the height at which the circular vertical walls  101  will remain in contact with the tray  140  when it is connected to the housing  110  as described below. The maximum height is the height at which the top of the circular vertical walls  101  abuts the bottom of the nozzle  160  when the lower panel  108  is connected with hood body  102 .  
      Tray  140  is connected to the range hood  100  by inserting it through intake opening  109  in lower panel  108  and into intake opening  112  in the motor housing  110  until outer wall  142  is firmly in place within gap  134 . Tray  140  may be releasably connected to housing  110  by wedging outer wall  142  into gap  134 . When connecting the tray  140 , it must be positioned so as to line-up gap  148  (shown in  FIG. 3 ) with nozzle  162  such that the nozzle is positioned tightly within the gap  148 . When tray  140  is connected to the housing  110 , outer wall  142  is also in contact with lower panel  108  and acts to seal any space that may exist between the housing and the lower panel thereby preventing air from entering into any undesired area within the range hood body  102 . A clip or other form of suitable restraint (not shown) accessible on the outside surface of the range hood is used to hold the tray in place. In this way, lower panel  108  need not be removed in order to access the interior of the motor housing  110 . A user need simply remove the tray in order to access the interior of the housing.  
      Grease accumulated on the fans and within the motor housing, is therefore forced out of the range hood by air delivered by air hoses  162 ,  12 ,  14 ,  16 ,  18 ,  26 , and  28 . The preferred embodiment therefore covers 3 main areas: the fans, the upper to lower interior of the motor housing and the lower surface of the motor housing. It is contemplated, however, that other embodiments could cover one or more of these areas.  
      Preferably, plates  8  will be made of metal and will be of similar thickness to the motor housing. However, it is also contemplated that other solid substances such as plastic could be used. The plate can be a variety of shapes provided that it provides a surface upon which to mount the air dispensers and protects the air dispensers from coming into contact with the fans. For example, the plate could be star-shaped, with an air hose and nozzle mounted at each but one point of the star, at which point all the air hoses will meet so as to exit the housing  110  en masse. However, as discussed above, it is preferred that the plate be circular as this provides the least interference with the air flow within the chambers  2 ,  4  when the range hood  100  is in operation. The plate need not be continuous, and in the preferred embodiment has gap  10  which is dimensioned to allow the power cord  50  from motors  125  to fit within it. Alternatively, the plate could have a rounded trough, dimensioned to provide sufficient space for the motor power chord to fit within when the motor  125  and plate  8  are attached to the motor housing  110 . Similarly, while in the preferred embodiment the air hoses will be attached to the upper surface of the plate  8  by way of flexible metal loops welded to the plate (not shown), it is also contemplated that other methods of connection could be used, such as glue, or plastic molding.  
      An alternative embodiment is shown in  FIGS. 4 and 5 . Range hood  200  has motor housing  110  within hood body  202 . In this embodiment fan  220  is of the squirrel cage type and is attached to motor  125 . In order to remove grease from the fan  220 , nozzle  260  is used. At one end nozzle  260  has twin heads for greater dispersion of compressed air against the fan  220 . One end of air hose  262  is attached to the other end of nozzle  260 , while the other end of air hose  262  is attached to an air compressor. The remainder of the air dispensers of the cleaning assembly are similar to that described in relation to the preferred embodiment shown in  FIGS. 1-3 .  
      Range hood  200  also has a different tray  240  and lower panel  108  design. In this embodiment, tray  240  has inner wall  244  and concentric outer wall  242 . Inner wall  244  is proximate to, and defines, an opening. Outer wall  242  is distal from the opening in relation to the inner wall  244 . Outer wall  242  is shaped and dimensioned to fit within gap  134  when tray  240  is connected with housing  110  so that a portion of outer wall  142  is in abutment with wall  130 . Preferably, the diameter of inner wall  244  is smaller than the diameter of lower fan edge  222 . The tray  240  is dimensioned such that when connected with the motor housing  110 , the top of inner wall  244  is just below the level of fan  220 , thereby directing air into the housing  110  by way of the fan  220 .  
      Nozzle  260  may be releasably or permanently attached to tray  240  such that when the tray is connected to motor housing  110 , hose  260  may then be attached to nozzle  262 . Connection means such as a clip  290  are used to connect air hose  262  to one end of nozzle  260 . It is contemplated that other methods of connection would be equally viable. Compressed air from the compressor is sent through air hose  262  and is dispersed by nozzle  260  against fan  220  thereby blowing any accumulated grease into the interior of the motor housing  110 .  
      In order to access the interior of the range hood, one must remove lower panel  208 , which has integrated fan grill  238  to prevent insertion of objects into the fan  220 .  
      A further alternative embodiment of a range hood  300  is shown in  FIGS. 6 and 7 . Enclosed in hood body  302 , motor housing  310  is compartmentalized in a similar fashion to the housing  110  of the preferred embodiment. However, the lower surface  313  of motor housing  310  is shaped such that grease accumulated in the housing interior drains into tray  340 . The air dispensers  12 ,  14 ,  16 ,  18  are the same as in the preferred embodiment and act to force condensate from the upper surface and down the sides to the lower surface of the motor housing and finally into tray  340 . The force generated by the air of air hoses  12 ,  14 ,  16  and  18  is sufficient to drive accumulated grease down the sides of the housing towards tray  340 . Accordingly, there is no need for an additional air hose/nozzle in the side of the housing to drive the grease along the bottom as in the preferred embodiment.  
      Tray  340  has outer wall  342 , inner wall  344 , separating wall  348 , outer trough  346  and inner trough  345 . Separating wall  348  acts to control air flow into the motor housing as is known in the art. Most condensate drains into outer trough  346 . However, a very small amount may drain into inner trough  345 . Integrated nozzles  370 , pass through outer wall  342  such that they are facing in opposite directions. Air hoses  372  connected to an air compressor may be releasably attached to nozzles  370 . Compressed air delivered through air hoses  372  is directed by nozzles  370  about the circumference of outer trough  346 , thereby forcing any accumulated condensate towards drainage holes  380  and  382 . Alternatively, a single nozzle having twin heads could be used such that the number of nozzles passing through the tray is reduced.  
      An integrated fan nozzle  360  passes through each of walls  342 ,  348  and  344 . Air hose  362  attached to an air compressor may be releasably attached to the fan nozzle  362 . Compressed air travelling through air hose  362  is directed by fan nozzle  360  against the fan  120  thereby forcing any accumulated grease into the interior of the motor housing where is then forced down to tray  340 . As shown in  FIG. 7 , channel  395  travels from inner trough  345  through wall  348 , outer trough  346  to wall  342  where it combines with drainage hole  380 . Drainage hole  382  is located on the opposite side of a partition wall  390 , thereby allowing grease forced around that side of the tray to drain out of the range hood. Grease drains through drainage holes  380  and  382  to external grease cup  326 .  
      To access the motor housing interior, first lower panel  308  with integrated fan grill  338  must be removed from the remainder of the hood body  302 . Using crips  290 , hoses  362  and  372  are removed from nozzles  360  and  370  respectively, before removing tray  340 .  
      As is apparent from the three embodiments described above, the cleaning assembly of the present invention may be adapted for various range hood designs. The main elements of the system being a source of compressed air and air dispensers to direct the compressed air against grease coated surfaces so as to force grease out of the range hood. Further alternative embodiments of the invention are contemplated by combining different fan types with different motor housing and grease tray designs.  
      The cleaning assembly of the invention may be activated in one of two ways. First, the range hood may be adapted such that the air compressor(s) of the cleaning assembly is automatically activated for a set period of time each time the range hood is shut off. The duration of air compressor activity may be varied, however it preferably lasts for approximately 15 seconds.  
      Alternatively, the air compressor of the cleaning assembly may be activated manually. In this way, if the range hood is subjected to particularly greasy vapour on a given day, the cleaning assembly may be activated manually in order to ensure that sufficient air is blown through the system to drive out all the accumulated grease.  
      Typically only a very small amount of grease accumulates on a fan as most is dispersed by means of the centripetal force of the rotating fan. However, any grease or liquid that remain on the fan will be blown to the interior of the housing by compressed air as discussed with respect to the various embodiments above. The compressed air directed against the fan will cause the fan to turn due to the force exerted on the fan blades, thereby ensuring that each blade of the fan is struck by compressed air in turn. The fan is prevented from spinning too rapidly by the natural resistance of the motor  125 . As a result of the grease being removed from the fan, very little grease accumulates in the trays  140  and  240  and inner trough  345 , and they need only be checked, and cleaned if necessary, during regular maintenance of the range hood and need only have minimal depth.  
      It will be appreciated by those skilled in the art that the preferred and alternative embodiments have been described in some detail but that certain modifications may be practiced without departing from the principles of the invention.