Abstract:
An air extraction hood, which comprises a canopy defining an enclosed air collection and treatment zone, and having an operatively downwardly directed air inlet through which air to be treated can enter the zone, as well as an air outlet through which air can be discharged from the zone, the canopy being mountable with clearance above a cooking surface such that its inlet is located above the cooking surface; mounting means for mounting treatment means inside the canopy in the collection and treatment zone, between the inlet and outlet; and passageway defining means defining an air passageway between the inlet and the mounting means along which air can pass, with at least part of the passageway defining means being curved over at least a major portion of the distance from the inlet to the mounting means, to enhance air flow along the passageway.

Description:
FIELD OF THE INVENTION 
     This invention relates to an air extraction apparatus. It relates in particular to an air extraction hood mountable over a cooking surface, and to a cooking installation incorporating such a hood. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, there is provided an air extraction hood, which comprises 
     a canopy defining an enclosed air collection and treatment zone, and having an operatively downwardly directed air inlet through which air to be treated can enter the zone, as well as an air outlet through which air can be discharged from the zone, the canopy being mountable with clearance above a cooking surface such that its inlet is located above the cooking surface; 
     mounting means for mounting treatment means inside the canopy in the collection and treatment zone, between the inlet and outlet; 
     passageway defining means defining an air passageway between the inlet and the mounting means along which air can pass, with at least part of the passageway defining means being curved over at least a major portion of the distance from the inlet to the mounting means, to enhance air flow along the passageway. 
     The canopy may be square or rectangular in plan view, and may have a roof, a front wall, a rear wall spaced from the front wall, and a pair of spaced side walls spanning the space between the rear and front walls. In use, the rear wall can thus be mounted against a wall from which the cooking surface also protrudes. 
     In other embodiments of the invention, two of the canopies may be located side-by-side with a common rear wall, with each canopy then having its own mounting means and passageway defining means. Instead, or additionally, two of the canopies may be located side-by-side with a common front wall or a common side wall. When the canopies are located side-by-side in this fashion, then naturally the canopies, or portions thereof, can be of integral construction and/or the common wall, or a portion thereof, can be omitted, if desired. 
     The air inlet will then be provided by or in the lower or underside of the canopy. The air inlet may thus be defined between a first inlet defining member extending between the side walls and located in proximity to the front wall; a second inlet defining member also extending between the side walls and located in proximity to the rear wall; and the side walls, eg the operatively lower edges of the side walls. 
     The passageway defining means may then comprise the side walls, a first passageway wall between the first inlet defining member and the mounting means and providing a first air deflection surface, and a second passageway wall between the second inlet defining member and the mounting means and providing a second air deflection surface, with at least a portion of the second air deflection surface being curved over said at least a major portion of the distance between the inlet and the mounting means. 
     The first inlet defining member may be the operatively lower edge of the front wall and/or the operatively lower edge of the first passageway wall. Similarly, the second inlet defining member may be the operatively lower edge of the rear wall and/or the operatively lower edge of the second passageway wall. The first and second inlet defining members may thus extend parallel to each other. 
     The second air deflection surface may be curved along the entire distance from the second inlet defining member to the mounting means, and may be curved along its full width, ie the entire distance from the one side wall to the other side wall. 
     The second air deflection surface may be concave or dish shaped, when the hood is viewed end on or in vertical section along a plane extending parallel to the side walls. 
     Similarly, the first air deflection surface may be curved along at least a portion of the distance from the first inlet defining member and the mounting means. Thus, the first air deflection surface may be convex shaped, when the hood is viewed end on or in vertical section along a plane extending parallel to the side walls. 
     The second inlet defining member may be located at an operatively lower level than the first inlet defining member, when the hood is mounted in position. In other words, the depth of the hood at the rear wall may be greater than its depth at the front wall. 
     The mounting means may comprise brackets at the upper ends of the passageway walls for releasably holding the treatment means. The hood may thus include treatment means held by the mounting means. The treatment means may comprise a filter for filtering oils and fats from contaminated air passing through the hood. In particular, the treatment means may comprise separation apparatus as described in European Patent Application No. 963083779.9, which is hence incorporated herein by reference. The mounting means will thus be such that the separation apparatus is located at an angle to the horizontal to permit fats and oils which are separated from air to collect in a collection zone thereof located at a lower level than the air inlet of the separation apparatus. 
     According to a second aspect of the invention, there is provided a cooking installation, which comprises 
     a cooking hob; and 
     an air extraction hood as hereinbefore described, mounted above the hob. 
     The invention will now be described by way of example with reference to the accompanying diagrammatic drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a three-dimensional view of a cooking installation according to the invention, incorporating an air extraction hood according to a first embodiment of the invention; 
     FIG. 2 shows a sectional view through II—II in FIG. 1, with the wall and hob omitted; 
     FIG. 3 shows a sectional view, similar to that of FIG. 2, of an air extraction hood according to a second embodiment of the invention; 
     FIG. 4 shows a sectional view, similar to that of FIG. 2, of an air extraction hood according to a third embodiment of the invention, mounted above cooking hobs; and 
     FIG. 5 shows a side view of an air extraction hood according to a fourth embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 1 and 2, reference numeral  10  generally indicates a cooking installation according to the invention, incorporating an air extraction hood according to a first embodiment of the invention, and which is generally indicated by reference numeral  12 . 
     The cooking installation  10  thus includes the air extraction hood  12  mounted against a wall  14 , immediately above a cooking hob  16 . 
     The cooking hood  12  comprises a rear panel or wall  18  mounted against the wall  14 , as well as a front wall or panel  20  spaced from the rear panel. The hood  12  also includes a roof or top panel  22  spanning the upper edges of the rear panel  18  and the front panel  20  and provided with an air outlet  24 . A conduit or spigot  26  leads from the air outlet  24 . The hood  12  also has a pair of side panels  28 ,  30  closing off the ends of the rear panel  18  and the front panel  20 . An enclosed air collection and treatment zone  32  is thus defined between the panels  18 ,  20 ,  22 ,  28  and  30 , with the outlet  24  leading from the zone  32 , and a downwardly directed air inlet  34  leading into the zone  32 . 
     A first passageway wall  36  extends the full distance from the side wall  28  to the side wall  30 , from the lower edge  38  of the front panel  20  to the lower edge of a wall  40  depending from the roof  22 . A lip  42  along the upper end of the wall  36  folds over a flange  44  protruding from the wall  40 . The wall  36  provides an air deflecting surface  46  which is convex in cross-section as seen in FIG.  2 . 
     A second passageway wall  48  is provided in proximity to the rear panel or wall  18 . The passageway wall or panel  48  has a lower edge  50  which extends parallel to the edge  38  of the wall panel  20  but is located at a lower level than the edge  38 . The passageway panel  48  has, along its upper edge, a flange shaped component  52  to which is attached a complementary flange shaped component  54  such that the components  52 ,  54  between them define a recess  56 . The passageway wall  48  has an air deflecting surface  58  which is concave in cross-section as seen in FIG.  2 . The passageway wall  48  is attached to an inwardly protruding portion  60  of the rear wall  18 , as well as to the side walls or panels  28 ,  30 . 
     The passageway walls  36 ,  48  and side walls  28 ,  30  thus define between them an air passageway  62 . 
     A flange-like component  64  is also attached to the wall  40  such that a recess  58  is defined between the flange  44  and the component  64 . The recesses  56 ,  58  are aligned and accommodate, in removable fashion, a separation apparatus  200 . The separation apparatus  200  is substantially in accordance with the separation apparatus  200  described in FIG. 7 of European Patent Application No. 96308377.9 which is incorporated herein by reference. Thus, the separation apparatus  200  comprises a vessel  102  providing a separation zone. The vessel  102  comprises a roof  106  which is rectangular in plan view. The vessel  102  also has wall panels  112 ,  114  with an air inlet  118  being provided in the wall panel  112  at a relatively high level adjacent the roof  106 . The air inlet  118  extends the full length of the wall panel  112 . An air outlet  108  is provided at a low level in the wall  114  and extends the full length of the wall panel  114 . A floor  110  joins the wall panels  112 ,  114  and is thus spaced from the roof  106 . End panels close off the wall panels  112 ,  114  and extend from the floor  110  to the roof  106 . 
     A fat/oil collection zone is provided inside the vessel adjacent the floor  110 . 
     A bed  124  of curled separating media is associated with the air inlet  118 , with the bed being located inside the vessel  102 . The bed  124  rests on an apertured support (not shown) which may be in the form of a piece of mesh or the like, with a further similar apertured support (not shown) located on top of the bed to hold the curled separating media in position. Contaminated air thus passes downwardly through the bed from the inlet  118  to the outlet  108 . The curled separating media are typically manufactured from stainless steel, and are as described in EP 96308377.9. 
     Air extraction means (not shown) such as a fan or blower, is located in the conduit  26 . 
     In use, as foodstuffs are cooked on the hob  14 , fats and oils, in gaseous form, are discharged into the atmosphere immediately above the hob. As a result of the blower or fan located in the conduit  26 , this air is drawn into the air passageway  62 , with the air flow along the air deflecting surface  58  being laminar. The contaminated air passes through the separating apparatus  200  where oils and fats are condensed therefrom and collect in the collection zone of the apparatus  200 . Purified air passes through the outlet  108  of the separating apparatus  200  and is withdrawn through the outlet  24  along the conduit  26  for discharge to the atmosphere. From time to time the fats and oils which have collected in the collection zone of the separation apparatus  200  must be removed/dispensed of. The separation apparatus  200  will be removed by sliding it upwardly into the recess  56  until the lower edge thereof disengages the lip of flange  44 , thereby to permit it to be removed. Excess oil can then be poured from it whereafter it can be washed, eg in a dishwasher, to further clean it and to clean the curled separating media therein. It is then reinstalled by reversing the above operation. 
     The Applicant believes that the air extraction hood  12 , having the curved air deflecting surface  58  in its air passageway  62 , has substantial advantages over known cooking hoods not having such a curved air deflection surface. Thus, when the hood  10  is sized such that air flow along the surface  58  is laminar, typically having a velocity in the range of 4m/sec, good air extraction from the zone immediately above the hob  14  is experienced. 
     Thus, air flow will be along the top of the hob from the leading edge thereof towards the wall  14 , upwardly along the wall  14 , along the surface  58  and through the separation apparatus  200 . In contrast, in known hoods, the air movement is directly upwardly leading to substantial inefficiencies. For example, the sizing of the conduits  26  and the extraction means in known installations must be substantially greater than that of the installation  10  to obtain the same extraction efficiency. 
     Still further, it is no longer necessary for the edge  38  of the front wall or panel  20  to overhang the leading edge of the hob  14 . With known air extraction hoods, the leading edge of the front panel must overhang the leading edge of the hob, typically by about 150mm, in order to obtain satisfactory extraction of air from the zone immediately above the hob into the hood. 
     More specifically, with known air extraction hoods, a large percentage, typically 80% of the air drawn into the hood is external air, ie not drawn in from the zone immediately above the hob  14 . The conduit  26  and air extraction means must thus be oversized in order to handle this excess air as well as the contaminated air from the zone immediately above the hob  14 . This disadvantage is to a large extent obviated with the hood  12  where substantially all the air drawn into the hood is from the zone immediately above the hob  14  as a result of the laminar flow induced along the concave surface  58  of the passageway wall  48 . 
     Additionally, with known air extraction hoods, it is normally necessary that the leading edge of the front panel thereof be located a minimum distance from a floor to provide the necessary heads or movement space for people using cooking apparatus. With the hood  12 , this minimum distance is no longer necessary and the hood  12  can thus be located at a lower level so that it can be used in more confined spaces. 
     With reference to FIG. 3, reference numeral  300  generally indicates an air extraction hood according to a second embodiment of the invention. 
     Parts of the hood  300  which are the same or similar to those of the hood  12 , are indicated with the same reference numerals. 
     The hood  300  is thus very similar to the hood  12  save that its front panel  20  is much narrower, with the roof panel  22  having a downwardly forwardly sloping portion  302 . 
     Typically, the maximum depth of the hood  300  is about 700mm, the maximum distance it protrudes from the wall  14  about 700mm, the radius of curvature of the surface  58  about 800mm and the radius of curvature of the surface  46  about 600mm. 
     Referring to FIG. 4, reference numeral  400  generally indicates a cooking installation according to another embodiment of the invention incorporating an air extraction hood according to a third embodiment of the invention. 
     Parts of the installation  400  which are the same or similar to parts of the installations of FIGS. 1 to  3 , are indicated with the same reference numerals. 
     The installation  400  includes two cooking hobs  402 ,  404  located adjacent each other. The hobs  402  and  404  are effectively free-standing, ie they are not located against a peripheral wall of a kitchen. A composite air extraction hood  406  is located above the hobs  402 ,  404 . Effectively, the hood  406  can be considered a composite of two of the hoods  12  or  300 , with the rear panels  18  thereof having been dispensed with. 
     Referring to FIG. 5, reference numeral  500  generally indicates an air extraction hood according to a fourth embodiment of the invention. 
     Parts of the air extraction hood  500  which are the same or similar to parts of the air extraction hood  12  of FIGS. 1 and 2, are indicated with the same reference numerals. 
     In the air extraction hood  500 , the passageway wall  36  extends some distance beyond the wall  40 , and has a reentrant or folded back portion  502  on which rests the separation apparatus  200 . The separation apparatus  200  is somewhat larger than that shown in FIGS. 1 and 2 and of slightly different construction, but functions in the same manner. 
     A hood or canopy light  504  is mounted in the passageway wall  36  such that it directs light downwardly from the surface  46 . 
     The air extraction hood  500  is capable of handling 0.303m 3 /s of air at 250 Pa, per 0.5 length of the hood.