GB2248790A - Scrubbing exhaust air - Google Patents

Abstract

An improved wet type kitchen exhaust fan is disclosed which has a casing (1) having a lower central inlet opening (2) and collecting troughs (11) and a collecting tank (12) formed around the side of the inlet opening (10), a trap device (2) provided above the inlet opening (10) to form a gap (G) therebetween, a water spray device (3) disposed above the trap device (2), a fan unit (5) mounted on the top of the casing (1), and a baffle plate device (4) disposed between the inlet port (50) of the fan unit and the baffle plate device (4). The baffle plate device (4) has fume/water fog mixture inlets (40) each being disposed outside a portion (A) of the baffle plate (4) located at a position directly facing the inlet port (50) of the fan unit (5), such that the aforementioned mixture will flow at a comparatively slow speed in a more evenly distributed manner toward the inlet port (50) of the fan unit (5). <IMAGE>

Description

MILK Kitchen Exhaust Fan This invention relates to an improved wet type kitchen exhaust fan.

As is well known, the kitchen exhaust fans used to remove oil particles from kitchen fumes are generally of two types, i.e. dry and wet types. In the former type, the kitchen exhaust fan is generally provided with a filtering device; in the latter type, it is further provided with a water spray device. The water spray device creates a water mist which helps to cool and condense the oil particles into an oil sludge which is then collected by the filtering device and washed away by the water spray. The wet type device is thus more efficient than the dry type in collecting oil particles.

For this reason kitchen exhaust fans recently developed are mostly of the wet type. The inventor has also noticed that the flow rate of kitchen fumes drawn by wet type devices is relatively slower than than of dry type devices having fan units of comparable capacity.

Furthermore, it has been observed that a part of the water mist created by the water spray device may drift out of the casing of the exhaust fan without being collected by same; this is ineffective and a disadvantage.

In addition, in conventional kitchen exhaust fans, of either wet or dry types, the fumes and water vapour produced during cooking cannot be completely collected and exhausted by the exhaust fan and are thus liable to escape and drift about the kitchen as there is a considerable open space between the fumes/air inlet port of the exhaust fan and the top of the cooking area.

In view of the aforementioned problems, the intention of this invention is to provide an improved wet type kitchen exhaust fan without impairing the flow rate of the kitchen fumes being drawn out by the exhaust fan, which efficiently prevents the water mist created in the device from leaving the exhaust fan before it can be collected by the same, and preferably in which an air curtain is formed to enclose the area just beneath the kitchen exhaust fan so that the fumes and water mist produced during cooking can be completely drawn into the casing of the kitchen exhaust fan without escaping into the kitchen.

According to this invention there is provided a kitchen exhaust fan comprising a casing having in a lower portion thereof a fumes inlet opening for allowing kitchen fumes to be drawn thereinto, collecting troughs and a collecting tank formed around the peripheral edges of said fumes inlet opening for receiving water and oils separated from said fumes, a trap means disposed above said fumes inlet opening, a water spray means disposed above said trap means for producing a water curtain including water mist, a fan unit disposed at an upper portion of said casing, and a baffle plate means disposed between said fan unit and said water spray means, wherein said baffle plate means comprises a plurality of fumewater mist mixture inlets disposed outside a position which faces directly the inlet port of said fan unit, whereby said fume-water mist mixture will flow at a relatively slow speed and in an evenly distributed state through said mixture inlets to said inlet port of said fan unit.

In a preferred form of this invention the kitchen exhaust fan of this invention consists of a fan unit and a casing which accommodates a trap device, a water spray device disposed above the trap device, and a baffle plate device disposed between the inlet port of the fan unit and the water spray device. The casing has a lower inlet port for allowing the fumes to be drawn thereinto, collecting troughs and a collecting tank respectively formed around the sides of that lower inlet port. The kitchen fume which contains oily vapour is drawn by the fan unit to pass first through the trap device which causes the kitchen fumes to make an abrupt turn and thus a part of relatively large particles of the oily vapour drip into the collecting troughs and the collecting tank.

The oily vapour containing relatively small particles is then drawn to come into contact with the water mist produced by the water spray in between the trap device and the baffle plate device whereby the oily vapour is caused to become condensed , and the fine oily particles are coagulated to become relatively large particles which will then drip onto the upper surface of the trap device and flow into the troughs and the tank. At the same time, the oily particles loosely stuck to the lower surface of the baffle plate device may be washed away by the water sprays from the water spray device, and the water spray that contains the oily particles will drip and flow into the collecting troughs and the tank in the same way as described above.

In a first illustrated embodiment of this invention, the baffle plate device is a single baffle plate disposed between the water spray device and the inlet port of the fan unit. The baffle plate is provided with a plurality of through-holes, leaving its central portion, which faces directly the inlet port of the fan unit, unperforated. The diameter of these through-holes is gradually enlarged in proportion to the distance measured from its respective location to that unperforated area.

With this arrangement, the still uncollected mixture consisting of oil particles and water mist will spread uniformly beneath the baffle plate and flow in a relatively slow speed via these through-holes towards the inlet port of the fan units, as a result the collecting efficiency is substantially promoted due to a more sufficient and thorough mixing of oil particles and water mist and a longer period for the mixture to become condensed so that it may be caused to drip by its own weight.

In a second illustrated embodiment of this invention, the baffle plate device includes a plurality of plates disposed one above another with a suitable spacing therebetween, in which the lowest plate is so located and dimensioned to face directly the inlet port of the fan unit, while each of the other plates is provided with an opening for allowing the aforementioned mixture to flow therethrough, which is formed at a position and has a dimension to correspond with the other plate disposed immediately therebelow. The mixture to be collected may be drawn through these spacing and flow through the openings of the plates towards the inlet port of the fan unit. Such an arrangement may result in substantially the same effect as that of the first illustrated embodiment.Preferably each of the said other plates has a central opening directly facing said inlet port of said fan unit, the closer a said other plate is to the said inlet port the larger the plate and the larger the central opening thereof.

In another advantageous form of this invention, the kitchen exhaust fan also comprises a collector member surrounding the fan unit for collecting residual mixture and the oil and water particles centrifugally discharged from the fan unit and deposited onto the peripheral wall of the collector member, and a collecting trough formed around the collector member to receive the condensed oil and water drops flowing through apertures formed on the peripheral wall of the collector member. The sludge consisting of oil and water may flow to the collecting tank by means of a tube connected between the collecting trough and the collecting tank. In this way the collecting efficiency is further promoted, and thus the gas exhausted from the fan unit is very clean.

In a further advantageous form of this invention, the kitchen exhaust fan is provided with an air duct along the peripheral rim of its casing. The air duct communicates with a blowing fan and is adapted to be mounted so that its bottom surface faces towards the kitchen floor and is so slotted that a substantially continuous air curtain is formed beneath the peripheral rim of the casing when the blowing fan is caused to operate, thereby the place just beneath the casing is shielded such that the fumes and water vapour produced during cooking will be completely drawn by the exhaust fan without escaping to the kitchen area.

By way of example, preferred embodiments of the invention will be described with reference to the accompanying drawings, wherein: Figure 1 is a schematic, cross-sectional view of a first embodiment of the kitchen exhaust fan illustrative of this invention, and Figure 2 is a schematic, cross-sectional view of a second embodiment illustrative of the kitchen exhaust fan of this invention.

As shown in Figure 1, the kitchen exhaust fan includes a generally box-shaped casing 1 having a lower central inlet opening 10, a trap device 2 disposed above central opening 10, a baffle plate 4 disposed above trap device 2 to form a space 2' therebetween, a water spray device 3 disposed in space 2', and a fan unit 5 disposed in the top end of casing 1.

Casing 1 has a lower panel la which is provided with inlet opening 10 at its centre, collecting troughs 11 located along the front, right and left sides of opening 10, and a relatively large capacity collecting tank 12 located at the rear side of opening 10. At the front side of casing 1 there is provided a chamber 13 and a front panel 14 into which an illuminating device and electronic control device (not shown) can be installed in a conventional manner.

At the bottom of collecting tank 12 a motorised pump unit 12d is provided. Water inlet 12a connected with a valve (not shown) and a tube (not shown) provided outside casing 1 is formed on the side panel of casing 1 and disposed above collecting tank 12. The level of liquid in collecting tank 12 is controlled by a float 12c and a float switch 12b. Float switch 12b is electrically connected to a power source (not shown) and a warning and indicating device (not shown). Drain tube 12e is also provided at the bottom of collecting trough 12.

Trap device 2 consists of an arcuate plate 2a disposed above and to correspond with central opening 10.

Arcuate plate 2a has its outer rim 20 extended beyond the inner side walls of collecting troughs 11 and collecting tank 12 to maintain a suitable gap G between the upper edge of central opening 10 and the lower edge of outer rim 20 of arcuate plate 2a. Trap device 2 causes the kitchen fumes drawn by fan unit 5 to enter into casing 1 through central opening 10, to make an abrupt turn over the side walls of collecting troughs 11 and tank 12 and side edges of arcuate plate 2a, and at the same time prevents water from water spray device 3 from dripping through central opening 10. It is readily understood that the oil sludge or water drops accumulating or dripping onto the upper surface of arcuate plate 2a will be easily directed to collecting trough 11 and tank 12.

Water spray device 3 includes pump unit 12d, a tube 3a having a first vertical tube section 3a' attached to the rear panel of casing 1 and a second horizontal tube section 3'' disposed just above the upper surface of arcuate plate 2a, and a plurality of short tube sections 3b each having a different length and being vertically and upwardly mounted on horizontal tube section 3razz with a spray nozzle or orifice on its top end. Water spray device 3, so arranged as to spray water against baffle plate 4, has a plurality of spray nozzles 3b having different heights and being adapted to spray water in various directions, such that a uniform water mist is formed in the entire space between casing 1 and arcuate plate 2a.

Baffle plate 4 is disposed between water spray device 3 and inlet port 50 of fan unit 5, and is provided with a plurality of through-holes 40 except for its central portion A which corresponds to inlet port 50 and is left unperforated. The diameter of through-holes 40 is gradually enlarged, depending on the distance between its respective location and unperforated area A; that is, the nearer through-hole 40 is to unperforated area A, the smaller the hole diameter will be.In this way, when the fumes passing around trap device 2 encounter the water mist sprayed from water spray device 3, a portion of the oil particles in the fumes is cooled to condense and merge with the water mist, thus becoming relatively large particles of oil sludge which can then fall downward to be collected in troughs 11 and tank 12, while the remaining portion of the oily vapour is mixed with the water mist to become a mixture of oily particles and water mist which will distribute itself uniformly beneath baffle plate 4 and then be carried upward via holes 40 into the space above baffle 4, and finally toward inlet port 50.With this arrangement, the oil particles in kitchen fumes can be sufficiently mixed with water mist as the oil particles are collecting The flow speed of the oil particles and water mist mixture is also relatively reduced, thereby the probability that the mixture will fall downward and increasingly enhance the efficiency of the oil particles collecting and decreasing the amount of the mixture which will escape through exhaust fan unit 5. Tests performed by the inventor, have shown that the first embodiment of this invention has a flow rate essentially equivalent to that of a conventional dry type kitchen exhaust fan having a fan unit of the same capacity.

Figure 2 shows a second embodiment of the kitchen exhaust fan illustrative of this invention. This embodiment differs from the first embodiment described above in the arrangement of baffle plate 4. More specifically, in this embodiment there is provided a plurality of baffle plates, which includes a first baffle plate 4a located in a position and having a dimension corresponding to inlet port 50 of fan unit 5, a second baffle plate 4b disposed above first baffle plate 4a with a gap B therebetween and having an opening 4b' located at a central portion and corresponding to first baffle plate 4a, and a third baffle plate 4c disposed above second baffle plate 4b and below inlet port 50 with gaps C and D between third baffle plate 4c and second baffle plate 4b and inlet port 50 respectively, and having an opening 4c' located at its centre portion and corresponding to opening 4b' of second baffle plate 4b. Such an arrangement has basically the same deflection and speed reduction functions with respect to the mixture of oil particles and water mist as that of baffle plate 4 of the first embodiment, requiring the oil particles and water mist mixture to flow through gaps B, C and D and through opening 4b' and 4c' toward inlet port 50, such that an oil particles collection substantially similar to but much more efficient than that of the first embodiment is created.

Referring again to Figure 1, top panel lb of casing 1 is extended upward around inlet port 50 to form a chamber 5a in which fan unit 5 can be installed. A first annular member 51 is fixedly attached in chamber 5a, and has provided at its bottom an opening which corresponds to inlet port 50. A second annular member 52 is fixedly mounted on the bottom of first annular member 51 to form a collecting trough 53 between the peripheral walls of first and second annular members 51 and 52. Collecting trough 53 communicates with collecting tank 12 by means of a drain tube 54 fixed onto the inner surface of casing 1. The annular peripheral wall of second annular member 52 is provided with a plurality of perforated holes 55 each extending slightly outward and downward, and the bottom wall of annular member 52 is extended toward fan unit 5 so as to coincide with inlet port 50 of fan unit 5.

In use, the oily vapour water mist mixture is drawn through inlet port 50 by the rotational movement of fan unit 5, and is then expelled from fan unit 5 by a centrifugal force produced by fan unit 5 and collides with and clings to the peripheral wall of second annular member 52 to condense into relatively large water or oil drops, which are then collected in collecting trough 53 through perforated holes 55 and drawn into collecting tank 12 through drain tube 54. Through this arrangement, the liquid particle content of the gas expelled from exhaust duct 56 can be greatly reduced and the gas expelled from the kitchen exhaust fan is relatively clean and dry without a lot of oil particles.

According to a further characteristic of this invention, the outer rim of casing 1 is further provided with an air pipe 6 which has provided along its bottom surface facing toward the kitchen floor or the cooking area F (shown in chain dotted lines) a continuous slotshaped air outlet 60 or outlets 60 consisting of a plurality of apertures. At least one air duct 61 connects air pipe 6 and the outlet of housing 7, which housing 7 contains an air fan 7a mounted at the opposite end of a rotary shaft of motor 5A for driving fan unit 5 If required, a water drop injector 8 may be mounted on air duct 61 to inject or drip in a controllable manner water drops into air duct 61.

With such an arrangement, an air curtain may be formed around the outer periphery of casing 1 of the kitchen exhaust fan when air fan 7a is caused to rotate, such that fumes produced during cooking can be advantageously confined by the air curtain so they can be completely drawn off the kitchen exhaust fan without escaping outside the area of casing 1 and contaminating neighbouring areas. Water drop injector 8 provides a humidifying effect so that the air curtain carries some water mist to cool the fumes thus further enhancing the efficiency of the oil particles collection.

While preferred embodiments of the kitchen exhaust fan of this invention have been illustrated and described, it is to be understood that the construction and arrangement of the kitchen exhaust fan of this invention may be otherwise modified; for example, air fan 7a can be provided at another location and separately driven to rotate instead of being driven by drive motor 5A of fan unit 5; baffle plate 4 can be formed into an arcuate or wavy shape to render the same effects.

Claims (8)

1. A kitchen exhaust fan comprising a casing having in a lower portion thereof a fumes inlet opening for allowing kitchen fumes to be drawn thereinto, collecting troughs and a collecting tank formed around the peripheral edges of said fumes inlet opening for receiving water and oils separated from said fumes, a trap means disposed above said fumes inlet opening, a water spray means disposed above said trap means for producing a water curtain including water mist, a fan unit disposed at an upper portion of said casing, and a baffle plate means disposed between said fan unit and said water spray means, wherein said baffle plate means comprises a plurality of fume-water mist mixture inlets disposed outside a position which faces directly the inlet port of said fan unit, whereby said fume-water mist mixture will flow at a relatively slow speed and in an evenly distributed state through said mixture inlets to said inlet port of said fan unit.

2. A kitchen exhaust fan as recited in Claim 1, wherein said baffle plate means comprises a single baffle plate, and said mixture inlets in said baffle plate are perforated holes each having a size corresponding to the respective distance between said respective hole and an unperforated portion of baffle plate located in a position which faces directly said inlet port of said fan unit.

3. A kitchen exhaust fan as recited in Claim 1, wherein said baffle plate means comprises a plurality of plates disposed one above another with a suitable spacing therebetween, and wherein the lowest plate is located and dimensioned so as to face directly said inlet port of said fan unit, and each of other plates is provided with an opening for allowing said mixture to flow therethrough, which opening is disposed at a position and has a dimension to correspond to said one plate disposed immediately therebelow, and said fume-water mist mixture inlets include spacings between said each two adjacent plates or between the uppermost plate and the top panel of said casing, and said openings each being located in said consecutive plates disposed above said lowest plate.

4. A kitchen exhaust fan as recited in Claim 3, wherein each of the said other plates has a central opening directly facing said inlet port of said fan unit, the closer a said other plate is to the said inlet port the larger the plate and the larger the central opening thereof.

5. A kitchen exhaust fan as recited in any preceding claim, further comprising a collector member surrounding said fan unit for collecting oil and water drops centrifugally discharged from said fan unit and deposited on the peripheral wall of said collector member, and a collecting trough formed around said collector member to receive the oil and water drops flowing through apertures formed on said peripheral wall of said collector member and to allow said drops to flow into said collecting tank by means of a tube connected between said collecting trough and said collecting tank.

6. A kitchen exhaust fan as recited in any preceding claim, further comprising an air duct formed along the peripheral rim of said casing, said air duct communicates with a blowing fan and is adapted to be so mounted that its bottom surface faces towards the kitchen floor and is so slotted that a substantially continuous air curtain is formed beneath said peripheral rim of said casing when said blowing fan is caused to operate.

7. A kitchen exhaust fan substantially as herein described and illustrated by Figure 1 of the accompanying drawings

8. A kitchen exhaust fan substantially as herein described and illustrated by Figure 2 of the accompanying drawings.