GB2500867A - An extraction canopy for a cooker - Google Patents

Abstract

Disclosed is an extraction canopy for a cooker, such as a commercial cooker. The extraction canopy comprises an inlet chamber 16, an extraction unit 20 attached to the inlet chamber 16 with an air inlet and a baffle or damper 32 to control the air flow direction between the inlet chamber 16 and the extraction unit 20. A removable filter 17 is contained in the inlet chamber 16 and a grease trap 34 is provided below the air inlet. A shelf 18 is provided on an exterior surface of the inlet chamber 16. The arrangement is intended to provide a compact extraction canopy with a separate filter and grease trap, both of which may be easily accessible and readily removed as required for cleaning and/or replacement.

Description

An extraction canopy The present invention relates to an extraction canopy for but not exclusively for extracting fumes from a kitchen.

Commercial cooking produces significant quantities of pollution in the form of grease, smoke, odours, steam and heat. Conventional methods of catchino and removing such pollution from the kitchen rely on stainless steel canopies mounted approximately 2m above the finished floor level and usually at least im above the cooking appliance.

According to the Heating and Ventilating Contractors' Association voluntary code of practice Ed/CA DTN 172 (htto: / /www.hvcapublicaticns.00.uk/Ecommerce/productplJEs/DWi72 udf) it is best practice that a canopy should be mounted more than 450mm from the work surface. Thus considerable energy is required to remove this pollution from the cooking process.

Filters contained in known canopies are intrinsically difficult to remove, usually by someone climbing onto very hot appliances to remove them. This is the source of many industrial accidents and poor kitchen hygiene. Often as a result canopy filters are left cut, thus increasing the risk of fire and the emission of pollution from the restaurant.

It is an aim of the present invention to provide an extraction canopy which addresses the aforementioned problems such that in use the present invention provides for the removal of cooking effluent from commercial cooking, and prevents large deposits of grease within the ducting. The present invention is also intended to reduce cocking extraction rates, provide point of origin fire protection and deliver ease of maintenance.

Accordingly a first aspect of the present invention is directed to an extraction canopy comprising an inlet chamber, an extraction unit attached to the inlet chamber with an air inlet, a damper placed between the inlet chamber and the extraction unit, a removable filter contained in the inlet chamber, a grease trap situated below the inlet chamber and a containment shelf attached to the inlet chamber above the air inlet which projects outwards.

This combination of features allows the extraction canopy to be mounted closer to the cooking appliance. The closer the extraction point is to the cooking appliance the more concentrated and therefore less diluted with normal kitchen air is the cooking plume. This means more pollution can be removed with less energy, and less relatively expensively treated and conditioned kitchen air is removed from the kitchen.

ihe present invention has the further advantage that is holds collected grease away from the air stream thus reduces the likelihood of excessive grease temperatures with its attendant fire risks. A low level exoraction canopy has the added advantage that the filter can be removed easily Icy kitchen personnel who remain on the ground at no risk.

Cocking of food often ignites airborne grease. Indeed this part of the cocking process produces the much sought after flame grilled' taste. The canopy accord.ing to the present invention reduces the ingress of these flames, when measured against the LPS263 standard for canopy filters flame penetration test.

Filters in known extraction canopies vary between 25mm and 50mm in depth. In the extraction canopy of the present invention the filter may be aoc!ording to the second aspect of the present invention to dissipate heat and eliminate flame penetration.

In a preferred embodiment the inlet chamber is cylindrical. This allows for ease of construction and a pleasing appearance. Preferably the damper is mounted to rotate round a central axis in the cylindrical inlet chamber.

This avoids any complicated construction for the damper and aids simple actuation of the damper. Advantageously a damper control motor is mounted at at least one end of the inlet chamber.

Advantageously the containment shelf is made of a translucent material preferably toughened glass. This advantageously allows good lighting of the top of the cooking appliance while ensuring that it is sufficiently large to entrain and capture the pollutants from the cooking process.

Preferably the grease trap comprises a container which is mounted underneath the inlet chamber such that it is pivotally attached at the rear and held at the front by releasable locking means. This allows for the trap to be easily lowered and cleaned.

Advantageously the extraction unit is placed vertically above the centre section of the inlet chamber such that air leaving the back of the filter passes through and or along the rear of the inlet chamber into the extraction unit.

Preferably the extraction unit Is equipped with a controllable fan to suck the air throuch the inlet chamber and exhaust to the atmosphere outside the kitchen. This has the advantage that the extraction canopy is a single unit with all the necessary equipment and can therefore be installed in a kitchen without a large amount of additional equipment.

In a preferred embodiment the extraction canopy has *at least one proximity switch off to cooking while the filter is removed.

Accordingly a second aspect of the present invention is direct to a filter which comprises at least two vanes which are angled such that air passing through the vanes Is subject to at least Three changes of direction and preferably five changes of direction.

This provides the advantage that grease and particles entrained in the air are more likely to fall cut of suspension to be collected.

Preferably the vanes are substantially the same and arranged as an array in the direction of flow of the air.

Advantageously the vanes have at least two angled corners in the direction of flow of the air. In a preferred embodiment at least one of those angled corners has an angle of at least 70°. Preferably each outside corner is equipped with a hooked surface perpendicular to the direction of flow of the air.

These hooked surface act as collection corners to collect the pollutants entrained in the exhaust gases. This provides the ad.vantage of greater turbulence in the air flowing through thus Improving the removal of pollutants. This removal of the grease ensures that in the event of a fire the flames flowing along the air extraction route do not come across large deposits of grease to ignite.

The filter should be a minimum of 120mm deep, the vanes should be spaced between 20-25mm, the design relies on an ideal face velocity of air 5m/s, (minimum 4m/s) , to reduce resistance the first angle should be no more than 75°, with the subsequent 2 angles in excess of this to improve centrifugal impacting of the grease particles. The capture hooks should provide an increase In air speed of over 6m/s again to increase centrifugal forces. The capture hooks should be on the opposite side of the preceding bend to aid centrifugal capture. The filter should be coared with PTFE or other similar non-stick coating to ensure continuous draining of the grease.

An example of an extraction canopy and baffle filter made according to the present invention will now be described in relation to the accompanying drawings, in which: Figure 1 shows a perspective view of an extraction canopy according to the present invention; Figure 2 shows a side view of the extraction canopy in Figure 1; Figure 3 shows a front view cf the extraction canopy in Figure 1; Figure 4 shows a cross section of the inlet chamber; Figure 5 shows a cross section of the inlet chamber with the grease sump open; Figure 6a shows a front view of a filter according to the present invention; Figure Eb shows a top view of the filter in Figure 6a; Figure En shows a perspective view of the filter in Figure 6a; and Figure 6a shows a side view of the end of the filter in Figure 6a.

Figure 1 show a perspective view of a cooking appliance with an extraction canopy 12 mounted on a wall 14 above it.

The extraction canopy 12 comprises an inlet chamber 16 which is of circular cross secrion and elongate horizontally, a containment shelf 18 which is elongate and projects from the centre of the inlet chamber horizontal to the ground and an extraction unit 20 which extends vertically from the centre of the inlet chamber 16. The containment shelf 18 is of a clear material preferable toughened glass and is held between two brackets 22 which extend outwards from the ends of the inlet chamber 22. The extraction unit 20 contains and extraction fan and control circuitry therefor and is connected to external ducting to carry away the exhausted air. The extraction unit 20 has an access door 23 and a control panel on its front.

Figure 2 shows a side view of the arrangement in Figure 1. As it can be seen the extraction canopy 12 is mounted flush with the wall 14. A panel 24 extends from the wall 14 to the middle of the bottom of the inlet chamber 16 and is secured gas tightiy to both. Similarly the extraction unit 20 extends up the wall 14 from the air inlet chamber 16. The distance between the top of the cooking appliance 10 and the bottom of the air inlet chamber 16 is noted as 300mm in this Figure.

Figure 3 shows extraction canopy 12 from the front. The containment shelf 18 is mounted between the owo brackets 22.

Below the containment shelf 18 can be seen a filter 17 in the centre. There are two filter spaces 32 on either side of the filter 17. Three grease traps 34 can be seen below the filter spaces 32 and filter 17. Each of the grease traps 34 has a catch 21 on its front. Each end of The inlet chamber 14 has a dome shaped structure 19 which caps the cylindrical inlet chamber 14.

Figures 4 and 5 show a cross section of the inlet chamber 16. The inlet chamber 14 lets in air through a gap 26 between the containment shelf 18 and the panel 24. Behind the gap 26 is formed the rectangular elongate filter space 32 in the lower half of the inlet chamber 16 in which fits the filter 17 which is not show. The filter space 32 is open underneath bar for support structure for the filter and has a roof 27 for the front half of the inlet chamber 16. The top rear half of the filter space 32 is open to allow the through flow of air into the upper half of the inlet chamber 16. The filter 17 is -1_c -removable for cleaning and is heid in by a locking mechanism.

The presence of the filter 17 is noted by out out switch 28 mcunted in the roof 27 which stos the cooking appliance 10 working when the filter 17 is removed. Below the space 32 is a triangular grease trap 34 which collects the grease that has been removed from suspension by the filter 17. The grease trap 34 neatly fit behind the panel 24 and below the space 32.

The grease trap 34 is pivotally attached by a pivot 36 at its rear co the inlet chamber 16. The grease trap 34 is attached at its front by a magnetic catch (not shown) to the inlet chamber 16 just below the gap 26, which works with a prestressed spring on the pivot 36. The front under side 0: the grease trap 34 has a facing 38 which in the closed position shown in Figure 4 matches with the panel 24. Figure 5 shows the grease trap 34 pivoted down to allow access so the grease oan be removed. In the upper half of the inlet chamber 16 there is a damper blade 32 to control the through flow of air. The damper blade 30 is mounted on a journal axis 33 which is in the centre of the inlet chamber 16 attached to the roof 27. The other end of the damper blade 30 touches the side wall of the cylindrical inlet chamber 16. The damper blade 30 rotates around the journal axis 33 such that in a fully closed position it forms a rear roof for the filter space 32 and in a fully open position it is past the forward jcin 43 of the extraction unit 20 to the inlet chamber 16.

-Il_i -The motor to control the damper blade 33 is position in one or both of the dome shaped struotures 19.

Figure 6 shows the filter 17. Figure 6a shows a front view of the filter 17. The filter 17 has a series of vertical vanes 46 mounted in parallel 10-20mm apart. The filter 17 has a rectangular rear portion with a curved front face that matches the cylindrical shape of the inlet chamber 14, with holders 48 at eaoh corner holding the vanes 46 in filter 17.

The filter 17 has two side end walls 50 which match the cross section of the filter space 32 in the inlet chamber 14. The filter 17 has rear wall 52 to which the vanes 48, side walls and rear holders 48 at top and bottom are attached. Each of the vanes 46 has a concertina shape behind front parts 54 which are perpendicular to the rear wall and match the curve of the inlet chamber 14. Each vane 48 mirrors the vane 46 next to it. The each vane 46 shown has five bends in it running front to back. The inside angles of each bend can vary from 65° to 90°. On the outside of each bend there is a hook shaped curved projection 54 which act as a collection corner for the pollution entrained in the exhausted gas. The first and last bends as the vane attached to the rear wall 52 and front part 54 transition in angle to that selected for inside bends. This structure means that air entering the filter 17 from the front will change direction three times and

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be swirled nhree times by the hooks. This results in a significant amount of the pollutants entrained in the air falling out in to the grease trap 34. The filter 17 is coated with PTFE or similar coating to ensure that the grease runs down into the grease trap 34.

The inlets of previously proposed kitchen filters range from around 250mm to above 500mm, the filter 17 shown in Figure 6 has an opening of 100mm. This has the effect of increasing the face velocity (incoming speed of air) to Sm/s.

Previously canopy filters have a face velocity between 1.5 to 3m/s. The pressure drop across the filter 17 is a maximum of 2EOPa and the noise generated at lm is below 7OdBa. This means any centrifugal motion the air undertakes increases the effect of particle removal by adding increased momentum to the pollution particulate.

Claims (15)

1. -13 -Claims 1. An extraction canopy comprising an inlet chamber, an extraction unit attached to the inlet chamber with an air inlet, a damper placed between the inlet chanter and the extraction unit, a removable filter contained in the inlet chamber, a qrease trap situated below the inlet charrer and a containment shelf attached to the inlet chamber above the air inlet which projects outwards.
2. 2. An extraction canopy according to Claim 1 in which the inlet chamber is cylindrical.
3. 3. An extraction canopy according to Claim 2 in which the damper is mounted to rotate round a central axis in the cylindrical inlet chamber.
4. 4. An extraction canopy according to Claim 1 to 3 in which a damper control motor is mounted at at least one end of the inlet chamber.
5. 5. An extraction canopy according to any preceding claim in which he containment shelf is made of a translucent material preferably toughened glass.

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6. 6. An extraction canopy according to any preceding claim in which the grease trap comprises a container which is mounted underneath the inlet chamber such that it is pivotally attached at the rear and held at the front by releasable locking means.
7. 7. An extraction canopy according to any preceding claim in which the extraction unit is placed vertically above the centre section of the inlet chamber such that air leaving the back of the filter passes through and or along the rear of the inlet chamber into the extraction unit.
8. 8. An extraction canopy according to any preceding claim in which ihe extraction unit is eguipped with a controllable fan to suck the air through the inlet chamber and exhaust to the atmosphere outside the kitchen.
9. 9. An extraction canopy according to any preceding claim in which uhe extraction canopy has at least one proximity switch off to cooking while the filter is removed.
10. 10. A filter for use with a canopy according to any preceding claim, comprising at least two vanes which are angled such that air passing through the vanes is subject to at least -15 -three changes of direction and preferably five changes of direction.
11. 11. A filter according to Claim 10 in which the vanes are substantially the same and arranged as an array in the direction of flow of the air.
12. 12. A filter according to Claim 10 or 11 in which the vanes have at least two angled corners in the direction of flow of the air.
13. 13. A filter according to Claim 12 in which at least one of the angled corners has an angle of at least 70°.
14. 14. A filter according to Claim 12 or 13 in which each outside corner is eguipped with a hooked surface perpendicular to the direction of flow of the air.
15. 15. A filter according to any of Claims 10 to 14 in which the filter is a minimum of 120mm deep and the vanes are spaced between 20-25mm.