TECHNICAL FIELD

This disclosure generally relates to kitchen ventilations systems. More specifically, this disclosure generally relates to air filters for kitchen ventilation systems.

BACKGROUND

Range or kitchen hoods are used to extract cooking particles suspended in the air, such as vapours (including water vapour), grease, cooking odours, heat, smoke, etc. The unwanted particles are forced through a filter and extracted from the exhaust air. In some range hoods, the unwanted particles are forced through a baffle filter, which filters grease molecules from the air by collecting the grease particles along the interlocking baffles. Other range hoods have cyclonic or centrifugal filters that extract grease particles in the air by forcing the air through a helical path in a vortex chamber. However, these filtration systems require routine maintenance to clean the baffles and grease that is collected.

Other known range hoods use filters that use clay or porous ceramic beads to trap grease or oil particles on the filter’s surface area. However, the retention rate of grease on these beads can be diminished at lower air velocity rates. Thus, to achieve the optimal retention of grease particles, a larger driving force (such as a fan) is required to evacuate the air from the cooking surface and force through the filter, which incurs an additional energy consumption and cost.

There is therefore a need for improvement for an efficient and ecological filtration system.

SUMMARY

According to one aspect, there is provided a kitchen hood for filtering air removed from a cooking space or surface, the kitchen hood comprising a frame with an air intake and an outlet; a means of suction configured to move the air into the frame through the inlet and exhaust the air through the outlet; and at least one foam filter provided in the frame and being configured to receive the air from the inlet and filter unwanted particles from the air.

According to another aspect, there is provided a use of a refractory open cell foam filter in a kitchen hood. According to another aspect, there is provided a filter for use in a kitchen hood, the filter comprising a refractory open cell foam.

According to a general aspect, there is provided a kitchen hood for filtering air removed from a cooking place. The kitchen hood comprises: a frame with an air intake and an outlet; a means of suction configured to move the air into the frame through the inlet and exhaust the air through the outlet; and at least one foam filter provided in the frame and being configured to receive the air from the inlet and filter unwanted particles from the air.

According to another general aspect, there is provided a use of a refractory open cell foam filter in a kitchen hood. In an embodiment, the at least one foam filter is a refractory open cell foam filter, which can comprise ceramic foam, such as silicon carbide, aluminum oxide, and/or zirconium oxide.

According to still another general aspect, there is provided a filter for use in a kitchen hood, wherein the filter comprising a refractory open cell foam.

In an embodiment, the at least one foam filter is a refractory open cell foam filter, which can comprise ceramic foam, such as silicon carbide, aluminum oxide, and/or zirconium oxide.

In an embodiment, the at least one foam filter has a thickness between about 0.25 inches and about 8 inches, in another embodiment, a thickness of about 0.5 inches to about 3 inches, and, in still another embodiment, a thickness of about 1 inch to about 2 inches.

In an embodiment, the at least one foam filter has a porosity of between about 5 pores per inch (PPI) and about 40 PPI and, in another embodiment, a porosity of between about 10 PPI and about 25 PPI.

In an embodiment, the at least one foam filter comprises an upstream foam filter, with an upstream porosity, and a downstream foam filter, with a downstream porosity. The upstream porosity can comprise larger pores than the downstream porosity. For instance, the upstream porosity is between about 5 PPI and about 15 PPI and the downstream porosity is between about 15 PPI and about 25 PPI.

In an embodiment, the at least one foam filter is a plurality of foam filters. The plurality of foam filters can comprise an upstream foam filter, an intermediate foam filter, and a downstream foam filter. The upstream foam filter can comprise larger pores than the intermediate foam filter and/or the downstream foam filter. The porosity of the upstream foam filter can be between about 5 PPI and about 15 PPI and the porosity of the intermediate foam filter and the downstream foam filter can be between about 15 PPI and about 25 PPI. In an embodiment, the plurality of foam filters are spaced apart by a gap, which can be between about 0.015625 inches and about 6 inches, or between about 0.125 inches and about 3 inches, or between about 0.25 inches and about 0.5 inches.

In an embodiment, the at least one foam filter has a filter surface area of between about 2 inches to about 30 inches per linear foot, in a further embodiment, the filter surface area is between about 4 inches and about 30 inches per linear foot, in another embodiment, the filter surface area is between about 6 inches and about 24 inches per linear foot, and, in still another embodiment, the filter surface area is between about 8 inches to about 20 inches per linear foot.

In an embodiment, the kitchen hood is self-cleaning.

In an embodiment, the kitchen hood further comprises a baffle filter provided in the frame adjacent to the air intake. In an embodiment, the kitchen hood can further comprise an upstream cleaning system on an upstream side of the baffle filter. In an embodiment, the kitchen hood can further comprise a downstream cleaning system on a downstream side of the baffle filter. The baffle filter can be removable from the frame.

In an embodiment, the frame further comprises a baffle system.

In an embodiment, the means of suction has a capacity to create an air velocity of between about 100 and about 500 feet per minute at the foam filter and, in another embodiment, the air velocity is between about 150 and 350 feet per minute at the foam filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional side view of a kitchen hood in accordance with a first embodiment showing a baffle filter and two foam filters superposed to the baffle filter;

FIG. 2 is a cross sectional side view of a kitchen hood in accordance with another embodiment showing a baffle filter and two foam filters, spaced-apart from the baffle filter;

FIG. 3 is a cross sectional side view of a kitchen hood in accordance with another embodiment showing a baffle filter and three foam filters, spaced-apart from the baffle filter;

FIG. 4 is a cross sectional side view of a kitchen hood in accordance with another embodiment showing a baffle filter and three foam filters, spaced-apart from the baffle filter;

FIG. 5 is a cross sectional side view of a kitchen hood in accordance with another embodiment showing an integrated baffle system, acting as baffle filter, and three foam filters; FIG. 6 is a partial cross sectional side view of a kitchen hood in accordance with another embodiment showing a cross sectional view of an integrated baffle system acting as baffle filter, and a foam filter, and a side view of the frame;

FIG. 7 is a perspective front view of a foam filter for use in a kitchen hood; and

FIG. 8 is a graphical representation of a filter performance comparison between a prior art kitchen ventilation system that uses a filter comprising clay balls and a kitchen hood according to another embodiment.

DETAILED DESCRIPTION

The devices and techniques described herein relate to kitchen or fume hoods and kitchen filtration systems, also known type I and type II hoods (NFPA 96 - National Fire Protection Association - Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations). In this context, a “kitchen hood” may refer to any duct or ductless ventilation system configured to vent away grease, oil, fat, moisture, smoke, etc. from a cooking surface or space, such as a range. Accordingly, “a kitchen hood” may refer to a range hood, vent hood, exhaust hood, kitchen exhaust system, kitchen ventilation system, ventilated ceilings, etc. The kitchen hoods described herein filter the airflow vented away from a cooking surface or space, at least in part, with a foam filter. Foam filters are a type of air cleaner filter that use small cells or pockets as the filtering material to trap unwanted air contaminants and particulates. Foam filters are made up of these tiny interlocking cells or pockets that prevent the passage of undesired particles, while simultaneously allowing the passage of air. In some implementations, the foam filter can be a refractory open-cell foam filter. Foam filters have other known uses such as soundproofing, thermal insulation, or other types of filtration, such as filtration for compressed air, exhaust gas, water, metal, or engine oil. Foam filters, including refractory open-cell foam filters, are durable and resistant to fire and flame passage; thus, a foam filter for use in a kitchen hood provides a filter that is resistant to high temperatures, while efficiently reducing the grease, oil or particle content in the exhaust airflow. The foam filters can act as a barrier to prevent a fire in the kitchen hood from spreading to the ventilation system, thus reducing the risk of fire in the ventilation system. Furthermore, foam filters have surprisingly been found to be particularly efficient in the context of kitchen hoods, in part due to these known qualities, but also in that, unlike other types of kitchen ventilation filters, they maintain a better filtration performance at low velocity. This characteristic makes foam filters particularly suitable for kitchen hoods, especially in conjunction with demand ventilation systems. Other characteristics that make foam filters suitable for application in a kitchen hood include, without limitation, having a neutral pH, ability to be regenerated, ability to promote the creation of biofilms, lightweight, modular, and being washable for continued use.

The foam filters described herein can comprise any type of foam or foaming filter, such as refractory open cell foams, including, without limitation ceramic foams, carbon foams, and metal foams, such as metal oxide foams. The refractory open-cell foams can comprise, for example, silicon carbide, zirconium oxide, aluminum oxide or a combination thereof. The refractory opencell foams are lightweight, porous structures that are configured to allow a forced airflow therethrough, with an exiting airstream having a reduced quantity of unwanted particles.

Referring now to Figure 1 , a kitchen hood 110 comprising at least one foam filter 120, a removable baffle filter 130, and a hood housing or frame 140. The foam filter 120 is configured to receive a forced airflow 150 therethrough and extract unwanted particles, such as grease, from the forced airflow 150, producing a cleaned or filtered airflow 160. The forced air flow 150 is produced by a means of suction (not shown) that removes at least a portion of air around a cooking surface or space and forces the air through the baffle filter 130 and foam filter 120 in the kitchen hood 110. In this implementation, the at least one foam filter 120 comprises two foam filters separated by a gap 122. However, it is understood that the at least one foam filter 120 can comprise any number of foam filters stacked or abutted against each other or provided separately from each other.

In some implementations, when multiple foam filters 120 are used, the foam filters 120 can be directly superimposed on each other to create a continuous filter area. In other implementations, the multiple foam filters 120 can be spaced apart by a gap 122 to limit the propagation of grease by capillarity, thus contributing to better and more efficient filtration. The gap 122 is a spacer between two adjacent foam filters 120 that can increase the air cleaning efficiency of the kitchen hood 110 when compared to two adjacent foam filters 120 that are superimposed on each other. For example, when the foam filters are superimposed on each other, the grease molecules can migrate along the surface of the open cells in the foam filter due to surface tension. However, when two adjacent foam filters are separated by a gap 122, the capillarity of the grease molecules is reduced. Accordingly, gaps of varying size can be provided between adjacent or abutting foam filters. In some implementations, the gap 122 can be between about 1/64 of an inch (0.015625 inches) to about 6 inches between the adjacent foam filters 120. In other implementations, the gap 122 can be between about 1/8 of an inch (0.125 inches) to about 3 inches, or between 1/4 of an inch (0.25 inches) to about 1/2 of an inch (0.5 inches).

The baffle filter 130 removes some of the unwanted particles from the air as they attach, precipitate, and/or condense onto the various interlocking baffles. The baffle filter 130 can be removable from the frame 140 to facilitate easier cleaning and/or removal of unwanted particles, such as grease. The baffle filter 130 can be any type of known filter, such as a filter that includes a plurality of interlocking baffles that removes oil and grease particles from the air.

In the non-limitative embodiment shown, the foam filters 120 and the baffle filter 130 are removable as a single unit from the kitchen hood 110.

In some implementations, the kitchen hood 110 can comprise cleaning systems, such as a cleaning ramp, (not shown) above and below the baffle filter 130 and/or the foam filter 120. For example, the kitchen hood 110 can comprise an upstream cleaning system that is located adjacent to the baffle filter 130 on an upstream side (such as, near the air intake 142). When the baffle filter 130 and the foam filters 120 are spaced apart, the kitchen hood 110 can also comprise a downstream cleaning system that is located on a downstream side of the baffle filter. In other implementations, the kitchen hood 110 can be self cleaning such that hot or cold water, and optionally cleaning solution, can flow through the filters via the means of suction to remove the unwanted particles that have collected on the foam filters 120 and/or the baffle filter 130.

The kitchen hood 110 has a frame 140 defining an air intake 142 and an outlet 144, and including a filter holder. In this implementation, the filter holder comprises protrusions 146a and 146b, upon which the baffle filter 130 is supported. The protrusions 146a and 146b extend from the frame 140 internally to the kitchen hood 110 and provide a surface against which the baffle filter 130 can sit. The protrusions 146a and 146b can be configured to have fastening means to secure the baffle filter 130. Alternatively, the baffle filter 130 can rest upon the protrusions 146a and 146b for easy removal. In this implementation, protrusion 146a extends downwardly from a top side of the frame 140 and a portion of the protrusion 146a is angled inwardly towards the second protrusion 146b. The second protrusion 146b creates a pocket for a corner of the baffle filter 130 to rest upon. Accordingly, the baffle filter 130 is secured between protrusions 146a and 146b during regular use and can be lifted and removed from the kitchen hood 110 when being replaced or cleaned.

The air intake 142 is configured to receive the forced airflow 150 produced by the means of suction, which then flows through the baffle filter 130 and then the foam filters 120 and out the outlet 144. The outlet 144 can be connected to a duct system to remove the filtered air 160 from the room the kitchen hood 110 is being used in. For example, the outlet 144 can have flanges 145a and 145b to facilitate coupling to a duct system. Alternatively, the kitchen hood 110 can be a ductless system where the filtered air 160 is recirculated to the room through the outlet 144. In this implementation, the foam filters 120 are abutted against the baffle filter 130 such that the forced airflow 150 that flows through the baffle filter 130 is immediately filtered through the foam filters 120 before being expelled or exhausted through outlet 144. The foam filters 120 and the baffle filter 130 are supported by protrusions 146a and 146b on the frame 140 at an angle to the flow direction of the forced airflow 150 and the filtered air 160 being expelled or exhausted through the outlet 144.

Referring now to Figure 2, there is shown an alternative embodiment of the kitchen hood wherein the features are numbered with reference numerals in the 200 series which correspond to the reference numerals of the previous embodiment. The kitchen hood 210 includes an upstream foam filter 220a, a downstream foam filter 220b, a removable baffle filter 230, and a frame 240. The frame 240 defines an air intake 242 and an outlet 244 and includes a baffle filter holder and a foam filter holder. The baffle filter holder comprises protrusions 246a and 246b creating a surface upon which the baffle filter 230 is supported. The foam filter holder comprises a second set of protrusions 248a and 248b, extending from the frame 240 near the outlet 244, and is configured to produce a surface upon which the upstream foaming filter 220a is supported. In some implementations, the protrusions 246a and 246b can comprise means to fasten the upstream foam filter 220a to the frame 240. Alternatively, the protrusions 248a and 248b can provide a surface upon which the upstream foam filter 220a can be supported without being coupled to the frame 240, to facilitate easy removal for replacement or cleaning.

Similarly to the implementation shown in Figure 1 , the kitchen hood 210 of Figure 2 has the upstream foam filter 220a and the downstream foam filter 220b provided at an angle to the flow direction of the forced airflow 250 and the filtered air 260 being expelled or exhausted through the outlet 244. However, in this implementation, a second set of protrusions 248a and 248b is provided to support the upstream foam filter 220a at a distance from the baffle filter 230, such that a forced airflow 250 is pre-filtered in the baffle filter 230 and a pre-filtered airflow 252 exits the baffle filter 230 and is forced through the upstream foam filter 220a and then the downstream foam filter 220b via the means of suction, producing a filtered airflow 260. Thus, in this implementation, the upstream foam filter 220a is affixed or supported by the frame 240 independently from the baffle filter 230. The second set of protrusions 248a and 248b extends inwardly from the frame 240 to create a surface upon which the upstream foam filter 220a can rest. When there is a gap 222 between the upstream foam filter 220a and the downstream foam filter 220b, additional sets of protrusions can extend from the frame 240 to support the downstream foam filter 220b. In other implementations, the downstream foam filter 220b can be separated from an upstream foam filter 220a via at least one spacer configured to hold the downstream foam filter 220b at a distance (/.e., the gap 222) from the upstream foam filter 220a, while still allowing the downstream foam filter 220b to be supported by the upstream foam filter 220a, and thus by the second set of protrusions 248a and 248b.

Referring now to Figure 3, a kitchen hood 310 comprising an upstream foam filter 320a, an intermediate foam filter 320b, a downstream foam filter 320c, a baffle filter 330, and a frame 340 is shown. The frame 340 defines an air intake 342 and an outlet 344 and includes a baffle filter holder and a foam filter holder. The baffle filter holder comprises protrusions 346a and 346b creating a surface upon which the baffle filter 330 is supported. The protrusions 346a and 346b can be adjustable to accommodate varying sizes of baffle filter 330. In some implementations, the protrusions 346a and 346b can be moveable to facilitate an open configuration and a closed configuration, thus allowing the baffle filter 330 to be removed from the frame 340 for cleaning or replacement. The foam filter holder comprises a second set of protrusions 348a and 348b, extending from the frame 340 near the outlet 344, and is configured to produce a surface upon which the upstream foaming filter 320a is supported.

Similarly to the implementation shown in Figure 2, the kitchen hood 310 of Figure 3 has foam filters 320a, 320b, and 320c that are provided at a distance from the baffle filter 330 and thus are affixed or supported by the frame 340 independently from the baffle filter 330. The second set of protrusions 348a and 348b provides the foam filters 320a, 320b, and 320c at a distance from the baffle filter 330 such that a forced airflow 350 is pre- filtered in the baffle filter 330 and a pre-filtered airflow 352 exits the baffle filter 330 and is forced through the foam filters 320a, 320b, and 320c via the means of suction, producing a filtered airflow 360. However, in this implementation, the second set of protrusions 348a and 348b is configured to support the foam filters 320a, 320b, and 320c in a substantially horizontal configuration. The pre-filtered airflow 352 exits the baffle filter 330 at an angle and is forced or vented through the foam filters 320a, 320b, and 320c at an orientation that is substantially similar to the direction of flow of the filtered airflow 360 exiting the outlet 344.

The second set of protrusions 348a and 348b is provided adjacent to the outlet 344. The protrusions 348a and 348b form a receptacle to hold the foam filters 320a, 320b, and 320c. The protrusions 348a and 348b can be adjustable to accommodate varying sizes of foam filters 320a, 320b, and 320c. In some implementations, the protrusions 348a and 348b can be moveable to facilitate an open configuration and a closed configuration, thus allowing the foam filters 320a, 320b, and 320c to be removed from the frame 340 for cleaning or replacement. Similarly, to the embodiment shown in Figure 2, the upstream foam filter 320a can be separated from the intermediate foam filter 320b via a gap 322, and the intermediate foam filter 320b can be separated from the downstream foam filter 320c via a gap 322. The foam filter holder can be provided with protrusions or apertures to hold or secure the intermediate foam filter 320b and the downstream foam filter 320c to facilitate a gap between the corresponding foam filter that is located upstream.

Referring now to Figure 4, a kitchen hood 410 comprising an upstream foam filter 420a, an intermediate foam filter 420b, a downstream foam filter 420c, a baffle filter 430, a frame 440, and a collar 470, making a link between the frame 440 of the kitchen hood 410 and a ventilation duct (not shown), is shown. In the embodiment shown, the foam filters 420a, 420b, 420c are located on the collar 470, instead of being located inside the frame. In an alternative embodiment (not shown), the foam filters 420a, 420b, 420c can be located in a ventilation duct instead of the collar 470. The frame 440 defines an air intake 442 and an outlet 444 and includes a baffle filter holder. The baffle holder comprises protrusions 446a and 446b configured to support the baffle filter 430. In this implementation, the foam filters 420a, 420b, and 420c are orientated horizontally in the collar 470 (i.e. normal to sidewalls of the collar 470 and to the airflow path) coupled to the outlet 444, such that a forced airflow 450 that flows through the baffle filter 430 exits the baffle filter 430 as a pre-filtered airflow 452 and flows through the outlet 444 to the collar 470. The pre-filtered airflow 452 is vented through the foam filters 420a, 420b, and 420c simultaneously with being removed from the frame 440 via the collar 470.

The outlet 444 can comprise a flange or other surface to facilitate attachment to the collar 470. In this implementation, the collar 470 can be provided as part of the kitchen hood 410 and be configured to attached to the ventilation system of the building, such as via flanges 449. Thus, the collar 470 has means to support or attach (not shown) the foam filters 420a, 420b, and 420c, such a protrusion, flange, or aperture that the foam filters 420a, 420b, and 420c can fit partially within. In other implementations, the outlet 444 may comprise a flange or other surface to facilitate attachment to the ventilation system of the building, and the foam filters 420a, 420b, and 420c are configured to be placed in the ventilation system of the building to filter the pre-filtered airflow 452. The means to support or attach the foam filters 420a, 420b, and 420c should allow the individual foam filters 420a, 420b, and 420c to be removed easily for cleaning or replacing.

It is appreciated that, in an alternative embodiment (not shown), the number and configuration of the foam filters 220a, 220b, 320a, 320b, 320c, 420a, 420b, 420c can vary from the embodiments in Figures 2, 3, and 4. Referring now to Figure 5, a kitchen hood 510 with at least one foam filter 520 and a frame 540 comprising a baffle system is shown. The baffle system comprises a first baffle 532, a second baffle 534, a third baffle 536, and an opening 538, which are configured to force airflow 550 through the kitchen hood 510 along a non-linear path. As noted above, the forced airflow 550 is provided by a means of suction (not shown). The frame 540 further defines an air intake 542 and an outlet 544, and includes a foam filter holder. The outlet 544 can comprise a flange 549 or other attachment means that is configured to connect with the ventilation system of the building. The foam filter holder comprises a set of protrusions 548a and 548b that forms a surface upon which the foam filters 520 are supported. In this implementation, the protrusions 548a and 548b also form a channel 545 between an opening 547, created by the protrusions and the outlet 544, and the outlet 544 of the frame 540. The foam filters 520 are contained in the channel 545, such that the airflow 552 directed from the baffle system flows through the channel 545, and thus through the foam filters 520, and out the outlet 544.

The first baffle 532 protrudes into the interior of the kitchen hood 510 from a top side of the frame 540 in a substantially vertically or downward direction. In some implementations, the first baffle 532 can be coupled to the frame 540 in an area that is adjacent to the outlet 544. A portion of the first baffle 532 is angled towards the outer side wall of the frame 540 to direct the forced airflow 550 through the opening 538 in the baffle system. The opening 538 is formed by the first baffle 532 and the second baffle 534. The third baffle 536 can be provided adjacent to the opening 538 to disrupt the airflow flowing through the opening 538 and/or direct the airflow towards the opening 547 and through the channel 545. In this implementation, the forced airflow 550 is pulled into a cavity 580 defined by the frame 540 by the means of suction (not shown). The cavity 580 is formed by the topside and one side of the frame 540 and the first baffle 532. The forced airflow 550 flows through the opening 538 formed by the first baffle 532 and the second baffle 534 and is directed upwardly towards the outlet 544 by the third baffle 536.

This baffle system thus acts to force airflow, act as a splash guard to prevent liquid from the cleaning system from contacting the cooking appliances, and trap grease particles along the surface of the baffles. Thus, the baffle system serves to reduce the initial grease and particulate content in the airflow, prior to filtration through the foam filters. The pre-filtering by a baffle system or baffle filter can reduce the chance of build-up of unwanted particles, such as grease, in the foam filter, thus, prolonging the life or period between cleanings of the foam filter. However, in some implementations, at least one foam filter can be provided in a kitchen hood without the use of a baffle system or baffle filter, such that the forced airflow is directed through the foam filters without being pre-filtered.

Referring now to Figure 6, a kitchen hood 610 with at least one foam filter 620 and a frame 640 is shown. In this implementation, the kitchen hood 610 includes a baffle system comprising a first baffle 632, a second baffle 634, and an opening 636, which are configured to allow the force airflow 650 through the foam filter 620. In this embodiment, the baffle system is an integrated baffle system that forms part of the frame of the kitchen hood 610. In other embodiments, the baffle system can be a removable filter cartridge that can be removed from the frame 640 for cleaning, replacement, maintenance, etc.

As noted above, the forced airflow 650 is provided by a means of suction (not shown). The frame 640 further defines an air intake 642 and an outlet 644 and includes a foam filter holder. The outlet 644 can comprise a flange 649 or other attachment means that is configured to connect with the ventilation system of the building. The foam filter holder comprises a set of protrusions 648a and 648b that form a surface upon which the foam filters 620 can be wedged between, for example by an interference fit.

The kitchen hood 610 includes a baffle system that comprises a first baffle 632 that protrudes into the interior of the kitchen hood 610 from a top side of the frame 640 in a substantially vertically or downward direction. A portion of the first baffle 632 is angled towards the outer side wall of the frame 640 to direct the forced airflow 650 towards the opening 636 in the baffle system. The opening 636 is formed between an end of the first baffle 632 and an end of the second baffle 634. In this implementation, the forced airflow 650 is pulled into a cavity 680 by the means of suction (not shown). The cavity 680 is defined by the topside and one side of the frame 640, the first baffle 632, and the second baffle 634. The forced airflow 650 flows through the opening 636 and is directed upwardly through the foam filter 620 by the means of suction. The filtered air 660 can then exit the outlet 644, and through a duct system or recirculated in the room. The kitchen hoods provided herein are examples of locations for the foam filters, and optionally a baffle filter or system. However, the person skilled in the art will understand that the kitchen hood can have other orientations that facilitates the movement of forced airflow through the foam filters via a means of suction. For example, the air intake can comprise the entire bottom side of the frame, or a substantial portion thereof. Similarly, the outlet can comprise the entire top side of the frame, or a substantial portion thereof.

Referring now to Figure 7, an exemplary foam filter 720 is shown. The foam filter 720 is a porous or permeable material with a plurality of open cells or pores 724 that allows the air to filter through the foam filter 720. The foam filter 720 can have a varying porosity (/.e., number of open cells or pores 724 per linear inch) that defines the filtration efficiency of a given particle size. For example, the porosity of the foam filter 720 in a kitchen hood 110, 210, 310, 410, 510, or 610 can range from between about 5 pores per inch (PPI) and about 40 PPI. In some implementations, the porosity can vary from between about 10 PPI and about 25 PPI, or between about 10 PPI and about 20 PPI. In some implementations, when multiple foam filters are used, each individual foam filter can have different porosity. For example, a kitchen hood can have multiple foam filters, with the upstream foam filter having a porosity of 10 PPI and the downstream foam filter and, optionally, the intermediate foam filter, having a porosity of 20 PPI. Alternatively, the kitchen hood can have a single foam filter with a porosity of 10 or 20 PPI, or two foam filters, each with a porosity of 20 PPI. Consideration of the duration of air filtration, the air speed, the size of the intended particles being filtered, and the type of cooking equipment being used should be given when determining the ideal porosity of each of the foam filters. It is understood that any number of foam filters with any combination of porosity can be used in the kitchen hoods described herein.

The foam filter(s) 720 used in the kitchen hood 110, 210, 310, 410, 510, or 610 can have a varying thickness. When multiple foam filters 720 are used, each individual foam filter 720 can have a unique thickness. In some implementations, the foam filter 720 has a thickness of between about 0.25 inches and about 8 inches. In other implementations, the foam filter has a thickness of between about 0.5 inches and about 3 inches, or between about 1 inch and about 2 inches. Consideration of the duration the air filtration being used and the air speed, which is dependent upon the means of suction and the presence or absence of a pre-filtration system, should be given when determining the quantity and thickness of the foam filter 720. For example, in the context of an industrial kitchen, where air filtration systems may be running constantly throughout the day, a greater number of foam filters 720 with a greater thickness may be considered, as opposed to a kitchen hood used in a home setting.

In some implementations, the foam filter 720 can have a varying size, and thus varying filter area or surface area of the filter medium that the forced airflow is received by. The size of the foam filter 720 can affect the pressure drop on either side of the foam filter(s) 720, and thus consideration of the driving force (/.e., means of suction) should be given when determining the size of the foam filter 720. In some implementations, the foam filter area can be between about 2 inches and about 30 inches per linear foot of hood. In some implementations, the foam filter area can be between about 6 inches and about 24 inches, or between about 8 inches and about 20 inches. Similarly to quantity, thickness, and porosity, consideration of the duration of air filtration, air speed, and type of cooking equipment being used should also be given when determining the size of the foam filter, and thus the foam filter area the forced air is exposed to.

It can be appreciated by the skilled artisan that any combination and/or quantity of foam filters 720 with a varying thickness, porosity, and surface area can be used in the kitchen hoods described herein.

Referring now to Figure 8, a graphical representation of the filtration performance of a prior art filtration system that uses clay balls (labelled “clay”) and a kitchen hood with a foam filter (labelled “foam filter”) is shown. The kitchen hood comprised a frame with a single foam filter comprising aluminum oxide and having a porosity of 10 PPI. As can be seen from Figure 8, the kitchen hood using a foam filter had an efficiency rate of about 99.6% when operated at an air velocity of 250 ft/min, which increased to about 99.7% when the kitchen hood was operated with an air velocity of 300 ft/min. In contrast, the prior art filtration system that uses clay balls had an efficiency rate of only about 98.6% when operated at an air velocity of 250 ft/min, which increased to about 98.7% when the filtration system was operated with an air velocity of 300 ft/min. Accordingly, the kitchen hood using a foam filter performed significantly better than the prior art filtration system using clay filters at air velocities of 250 ft/min and 300 ft/min.

In some embodiments, the means of suction in the kitchen hoods described above can have a capacity to create an air velocity of between about 100 and about 500 feet per minute, or between about 150 and about 350 feet per minute.

The means of suction can be any device that is configured to pull air into the air intake of the frame, through the foam filters, and exit through the outlet. For example, the means of suction can be a centrifugal or axial fan. The means of suction can be located in a position downstream of the foam filters, such that the air is pulled through the foam filter. For example, the means of suction can be located in a chamber defined by the frame that is between the foam filters and the outlet or the flanges configured to couple to the duct system (/.e., within the frame downstream of the foam filters). In other implementations, the means of suction can be located in a collar between the frame and the duct system, such as collar 470, in a position downstream of the foam filters. In other implementations, the means of suction can be located in the duct upstream of the foam filter or in any position in the duct system.

When the air velocity is increased due to an increase in the means of suction, the pressure drop at the filter terminals increases. For example, when the air velocity is 350 ft/min, the pressure at the filter terminals is around 0.65 in inches of water column (W.C.). As the pressure drop increases, the driving force required to move the air through the kitchen hood also increases to maintain the same air velocity. Thus, reducing the pressure drop at the filter terminals can reduce the driving force required to move the air through the filtration system (/.e., means of suction). A reduced driving force thus reduces the overall energy cost of the filtration system. Accordingly, use of the foam filters comprising aluminum oxide allows a similar filtration of grease in a kitchen hood when the air velocity in the filters is reduced to 150 ft/min to 250 ft/min, thus reducing the overall power requirement to achieve the same result.

Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while the specific embodiments have been illustrated and described, numerous modifications come to mind. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.