Field of the invention

The present invention relates to a cooktop comprising a downdraft extractor or ventilator.

Background art

US patent application US 2018 / 0073745 A1 discloses a household appliance including a heating element at an upper surface of the appliance, and a variable height down-draft vent assembly movable relative to the upper surface. The vent assembly includes a duct defining a flow passage between an upper end and a lower end thereof. The duct is movable in a vertical direction relative to the upper surface of the appliance. A drive assembly is provided for engaging the duct to position the upper end of the duct at a user selected variable height relative to the upper surface of the appliance. The movable duct includes an inner tube and an outer tube, wherein the inner tube has an upper end, a lower end and an internal passageway extending between the upper end and the lower end. A plurality of openings are formed in the upper end of the inner tube and fluidly communicate with the passageway. The outer tube is disposed around the inner tube and axially aligns therewith. The outer tube includes an upper end and a lower end. A plurality of openings is formed in the upper end of the outer tube, and air is drawn from the region proximate the upper end of the movable duct, through the plurality of openings in the outer tube, through the plurality of openings in the inner tube, along the passageway in the inner tube.

Downdraft vent assemblies as described above often suffer from high and unpleasant noise levels and moist/grease build-up limiting ventilation/extraction efficiency when in operation. The increased noise levels are typically caused by turbulent air flow through the duct as air passes through a plurality of openings when entering the duct, wherein the turbulent air flow further reduces the ventilation/extraction efficiency of the downdraft vent assembly.

Summary of the invention

The present invention seeks to provide a cooktop with improved downdraft extraction/ventilation, wherein the downdraft extraction produces significantly lower noise levels and exhibits higher extraction efficiencies and/or higher cooking vapour catch effectivity. Furthermore, the cooktop provides improved handling of moist, grease dirt etc. and minimizes uncontrolled internal contamination.

According to the present invention, a cooktop of the type referred to in the preamble above is provided, wherein the cooktop comprises an extractor duct extending through the support surface; and a ventilation system arranged underneath the support surface and fluidly connecting to the extractor duct for drawing air from above the support surface downwards, wherein the extractor duct comprises an inlet end, an outlet end and a convex inner surface extending between the inlet end and the outlet end. By providing a convex inner surface to the extractor duct allows significant reduction of turbulent airflow as air above the support surface converges into the extractor duct in smoother fashion, thereby reducing noise whilst increasing efficiency of the (downdraft) ventilation system.

In an advantageous embodiment, the convex inner surface is an air foil shaped inner surface, which provides even smoother convergence of air into the extractor duct and prevent early surface separation. In an exemplary embodiment, the inlet end of the extractor duct comprises a leading edge of the air foil shaped inner surface and wherein the outlet end comprises a trailing edge of the air foil shaped inner surface. In this embodiment, air drawn into the extractor duct flows from the leading edge toward the trailing edge and is prevented from separating early from the inner surface as a result of which laminar airflow is maintained within the extractor duct, thereby reducing turbulence and noise.

Short description of drawings

The present invention will be discussed in more detail below, with reference to the attached drawings, in which

Figure 1 shows a cross sectional view of a cooktop with a downdraft extractor duct according to an embodiment of the present invention;

Figure 2 shows a top view of a cooktop with a downdraft extractor duct according to an embodiment of the present invention;

Figure 3 shows a cross sectional view of a cooktop with a downdraft extractor duct according to another embodiment of the present invention;

Figure 4A and 4B show a streamline and noise level simulation of a downdraft extractor duct, respectively, according to a first embodiment of the present invention.

Figure 5A and 5B show a streamline and noise level simulation of a downdraft extractor duct, respectively, according to a second embodiment of the present invention.

Figure 6 shows a cross sectional view of a cooktop with a fan motor according to an embodiment of the present invention.

Detailed description of the embodiments

Figure 1 and 2 show a cross sectional view and top view, respectively, of a cooktop 1 with a downdraft extractor duct 4 according to an embodiment of the present invention. In the embodiments shown, the cooktop 1 comprises a support surface 2 for support of one or more cooking pots“P”. A downdraft extractor duct 4, hereinafter an extractor duct 4 for short, is provided and extends through the support surface 2. A ventilation or suction system 6 is arranged underneath the support surface 2 and fluidly connects to the extractor duct 4 for drawing air, cooking vapours etc. above the support surface 2 downwards. The extractor duct 4 comprises an inlet end 4a and an outlet end 4b, and in an exemplary embodiment the inlet end 4a extend through the support surface 2.

As further depicted, the extractor duct 4 comprises a (smooth) convex inner surface 8 that extends between the inlet end 4a and outlet end 4b. The convex inner surface 8 may be seen as a circumferential inwardly arched or curved wall surface of the extractor duct 4 providing an inner diameter/width“D” to the extractor duct 4 that varies from the inlet end 4a to the outlet end 4b, where a smallest inner width is provided somewhere there between.

According to the present invention, the circumferential convex inner surface 8 facilitates smooth air flow into the inlet end 4a, through the extractor duct 4, and out of the outlet end 4b of the extractor duct 4. The smooth air flow provided by the convex inner surface 8, when the (downdraft) ventilation system 6 is in operation, is to a large extent laminar in nature as a result of which turbulence is minimized, resulting in a more efficient flow and less noise. As a further advantage, the convex inner surface 8 improves the ventilation/suction efficiency of the ventilation system 6 due to lower air flow resistance.

From the top view of Figure 2 it follows that the extractor duct 4 need not be a circular or cylindrical duct. For example, in a group of embodiments the extractor duct 4 may be a rectangular, square, oval or circular duct, so that the shape of the extractor duct 4 may be chosen according to particular requirements/needs of the cooktop 1. In case the extractor duct 4 is substantially rectangular, for example, the convex inner surface 8 comprises two different widths D1 , D2 from the inlet end 4a to the outlet end 4b.

Furthermore, a grill, (mesh) screen) or vanes may be applied to the extractor duct 4, e.g. provided in the aperture formed by the inlet end 4a.

It is further noted that the extractor duct 4 may be arranged at any position P1 , P2 in the support surface 2 as shown depending on requirements of the cooktop 1 .

In an embodiment, the convex inner surface 8 may comprise an air foil shaped inner surface. The air foil inner surface provides for improved laminar flow through the extractor duct 4 as air flow separation from the air foil shaped inner surface occurs closer to the outlet end 4b of the extractor duct 4 rather then the inlet end 4b. In a particular advantageous embodiment, the inlet end 4a of the extractor duct 4 comprises a leading edge of the air foil shaped inner surface 8 and wherein the outlet end 4b comprises a trailing edge of the air foil shaped inner surface 8 In this embodiment, the air foil shaped inner surface 8 fully spans between the inlet end 4a and outlet end 4b, so that laminar air flow is provided over by and large the entire length of the extractor duct 4, wherein air flow separation from the air foil shaped inner surface 8 is delayed and occurs as close as possible to the outlet end 4b of the extractor duct 4.

As further shown in Figure 1 and 2, in an embodiment the extractor duct 4 may comprise an internally arranged, e.g. centrally arranged, duct wall 10 extending from the inlet end 4a to the outlet end 4b providing an extraction channel 12 on either side of the duct wall 10. This allows for directional air extraction from both sides of the extractor duct 4, such as when the extractor duct 4 is arranged between two cooking spots P on the support surface 2. The internally arranged duct wall 10 may further reduce turbulence in a central portion of the extractor duct 4 to keep noise and ventilation/suction inefficiencies to a minimum. In the embodiment shown, the extraction channels 12 on either side of the duct wall 10 are symmetrically arranged such that air/vapour extraction is substantially symmetrical with minimal noise and turbulence. In an embodiment, the duct wall 10 widens, i.e. tapers outward, from the inlet end 4a toward the outlet end 4b of the extractor duct 4, thereby reducing intake air flow resistance when air/vapour is being drawn into the extractor duct 4.

In Figure 3 a cross sectional view of a cooktop 1 with a downdraft extractor duct 4 according to another embodiment of the present invention is depicted. In the embodiment shown, the extractor duct 4 extends through the support surface 2 and is in a raised position with respect thereto, thereby raising the inlet end 4b higher (and as a consequence also the related area of low pressure) to facilitate vapour extraction when higher cooking pots P are used. In principle the depicted embodiment in Figure 3 is identical to the embodiment of Figure 1 except that the inlet end 4b of the extraction duct 4 extends further above the support surface 2 at a height“H”, but wherein the outlet end 4b remains below the support surface 2.

It is noted that the inlet end 4a as shown in Figure 1 need not be flush with the support surface 2. In particular, an advantageous embodiment is envisaged wherein the inlet end 4a will be slightly raised above the support surface 2 and be flush with a spill barrier 2a, i.e. a raised surface portion of the support surface 2 to avoid spill-over that could enter the extraction duct 4 whilst cooking.

In light of Figure 1 and 3, in an advantageous embodiment the extractor duct 4 may be movably arranged, in e.g. vertical direction, between a lowered configuration as shown in Figure 1 and a raised configuration as depicted in Figure 3. To that end an exemplary embodiment is provided wherein the duct wall 10 is connected to an actuation system for moving, e.g. raising and lowering, the extractor duct 4 upwards or downwards with respect to the support surface 2. By allowing the extractor duct 4 and in particular the inlet end 4a thereof to be raised and lowered with respect to the support surface 2, facilitates optimal air/vapour extraction for various cooking pots P. In alternative embodiment the extractor duct 4 may be connected to the actuation system in case no duct wall 10 is provided. Note that the actuation system may be a manual or automatic actuation system.

As mentioned earlier, according to the present invention the convex inner surface 8 facilitates smooth air flow into the inlet end 4a, smooth air flow through the extractor duct 4, and smooth air flow exiting the outlet end 4b of the extractor duct 4. The smooth air flow provided by the convex inner surface 8 when the ventilation system 6 is in operation is mostly laminar in nature so that turbulence and noise production is minimized. Furthermore, the convex inner surface 8 increases the overall efficiency of the ventilation system 6 due to lower flow resistance.

Figure 4A and 4B each show a streamline and noise level simulation, respectively, of an extractor duct 4 according to an embodiment of the present invention. As shown in Figure 4A, the convex inner surface 8 of the extractor duct 4 induces substantially parallel (curved) stream lines near the convex inner surface 8 that are indicative of laminar flow. The air flow remains attached to the convex inner surface 8 for nearly all of its length from the inlet end 4a toward the outlet end 4b and as such turbulence is reduced, keeping noise to a minimum. A somewhat louder noise zone N1 of air, wherein noise levels are the highest (54.64dB in this specific example), does exist and is indicated in Figure 4B. The noise zone N1 begins, approximately, where the inner diameter/width D of the extraction duct 4 begins to widen toward the outlet end 4b.

In the embodiments shown in Figure 4A and 4B, the convex inner surface 8 comprises an air foil shape, wherein the inlet end 4a comprises a leading edge 8a and wherein the outlet end 4b comprises a trailing edge 8b of the air foil shaped inner surface 8. The depicted stream lines of Figure 4A indicate that air flow remains attached to the air foil shaped inner surface 8 up to the trailing edge 8b, at which the air flow detaches and a trailing recirculation zone R1 develops, which is a source of turbulence and noise. However, the loudest noise zone is indicated as the zone N1 .

It is noted that flow separation occurs when a boundary layer on the convex inner surface 8 travels far enough against an adverse pressure gradient such that the velocity of the boundary layer is almost zero. Typically, an adverse pressure gradient occurs when static pressure inside the extractor duct 4 increases in the direction of flow, i.e. from the inlet end 4a to the outlet end 4b, which may occur due to widening of the inner diameter/width“D” as mentioned above. When flow separation occurs, recirculation zones tend to develop that may have negative impact on noise and performance.

When the extractor duct 4 is in a raised configuration/position with respect to the support surface 2, a wall recirculation zone may develop where the extractor duct 4 meets the support surface 2 or the spill barrier 2a when present.

Even though the convex inner surface 8, e.g. the air foil shaped inner surface, as depicted in Figures 4A and 4B significantly reduces turbulence and noise compared to prior art downdraft extraction systems, turbulence and noise can be even further reduced.

To that end reference is made to Figure 5A and 5B, showing a streamline and noise level simulation of an extractor duct 4, respectively, according to another embodiment of the present invention. In the embodiment shown, the extractor duct 4 comprises an outer surface 14 and a plurality of circumferentially distributed slots/channels 16 each of which extends from the convex inner surface 8, e.g. air foil shaped inner surface, to the outer surface 14. These slots/channels 16 allow for a secondary air flow to be provided when the extractor duct 4 is in the raised position so that the aforementioned wall recirculation zone is almost eliminated. Furthermore, the noise zone N1 as depicted in Figure 5B is considerably smaller and less loud than the noise zone N1 of Figure 4B (in the example shown, 48,51 dB). Therefore, the plurality of slots/channels 16 allow for further reduction of recirculation zones and noise generated by the extraction duct 4.

In an embodiment, the plurality of slots 16 may be located between the smallest inner diameter/width D of the extractor duct 4 and the outlet end 4b thereof. This also applies to the location of the slots/channels 16 for an air foil shaped inner surface 8.

In an advantageous embodiment, each slot of the plurality of slots 16 may be oriented downward at an acute/oblique angle with respect to the outer surface 14. This allows each slot 16 to provide an outlet opening in the convex inner surface 8 closer to the outlet end 4b of the extractor duct 4 whilst providing an inlet opening in the outer surface 14 closer to the inlet end 4a. These outlet openings ensure that air flow stays attached to the convex inner surface 8 below the outlet opening whilst providing sufficient secondary air flow through the outer surface 14 to minimize recirculation at the wall recirculation zone. To allow for improved smooth secondary air flow through the plurality of slots 16, an embodiment is provided wherein each slot is a curved slot.

Referring back to Figures 1 and 3, in an embodiment the cooktop 1 may further comprise a fluid collector housing 18 arranged underneath the support surface 2 that fluidly connects the extractor duct 4 to the ventilation system 6. The fluid collector housing 18 comprises two concave air deflection walls 22a, 22b that extend, in mirrored fashion, downward from an apex 20 of the fluid collector 18, wherein the apex 20 is centrally arranged underneath the extractor duct 4. The concave air deflection walls 22a, 22b allow for smooth sideways deflection of air flows A1 , A2 into separate sideways/laterally extending housing channels C1 , C2 when drawn air exits the outlet end 4b of the extractor duct 4. Note that the housing channels C1 , C2 allow for a reduction of an overall height of the fluid collector housing 18, leaving more space for kitchen storage beneath the support surface 2. Also, by deflecting the air flow A1 , A2 sideways allows for moist, condensation, grease, dirt etc. to be caught by the deflection walls 22a, 22b rather than the ventilation system 6. So the concave air deflection walls 22a, 22b act as moist and grease collectors.

It is noted that the concave air deflection walls 22a, 22b are outwardly curved or arched deflection walls as seen from inside the fluid collector housing 18, wherein each of the concave air deflection walls 22a, 22b comprises a highest end point/portion that connect at the apex 20 to the other deflection wall. Therefore, the concave air deflection walls 22a, 22b and apex 20 may be envisaged as forming a conical shaped bottom part of the fluid collector housing 18 which is centrally arranged below the extractor duct 4, wherein the apex 20 is proximal to the outlet end 4b of the extractor duct 4.

As further depicted, in an embodiment the aforementioned duct wall 10 may extend through the apex 20 of the fluid collector housing 18. In a further embodiment, the duct wall 10 moveably extends through the apex 20 of the fluid collector housing 1 , so when the extractor duct 4 is movable between a lowered position as depicted in Figure 1 and a raised position as depicted in Figure 3, the wall duct 10 may be configured for moving the extractor duct 4.

Figure 1 and 3 also show that in an embodiment the duct wall 10 may extend beyond the outlet end 4b of the extractor duct 4 into the fluid collector housing 18. This further facilitates convenient connection of the duct wall 10 to e.g. an actuation system for raising and lowering the extractor duct 4 upwards or downwards with respect to the support surface 2.

The air flows A1 , A2 as deflected by the concave air deflection walls 22a, 22b typically contain water vapour, oil/grease droplets etc. To reduce internal contamination throughout the fluid collector housing 18, an embodiment is provided wherein a lowest end point/portion of the two concave air deflection walls 22a, 22b comprises a leak tray 24a, 24b. The leak trays 24a, 24b allow moist, oil, grease etc. to move along the deflection wall 22a, 22b downward and be captured in the leak trays 24a, 24b, thereby preventing further dispersal through the fluid collector housing 18.

Preferably, the ventilation system 6 should remain as clean as possible to maintain efficiency and prevent extensive cleaning. To that end there is provided an embodiment wherein the fluid collector housing 18 comprises two internally arranged filter members 26a, 26b, e.g. rectangular filter members, each of which is arranged adjacent to and downstream from one of the two air deflection walls 22a, 22b and at an acute/oblique (outward) angle (a) to a longitudinal axis L of the extraction duct 4. The obliquely arranged filter members 26a, 26b as depicted allow space, e.g. sideways space, for the concave air deflection walls 22a, 22b and optionally the leak trays 24a, 24b to ensure that each of the filter members 26a, 26b remains substantially invisible through the inlet end 4a of the extraction duct 4. Also, the oblique arrangement of the filter members 26a, 26b allows for moist, oil, grease etc. to readily leak towards the concave air deflection walls 22a, 22b and in particular the leak trays 24a, 24b when present.

In an embodiment, each of the two filter members 26a, 26b comprises an upper edge and a lower edge, wherein the upper edge engages or extends toward the extractor duct 4 and wherein the lower edge engages or extends toward an outermost edge of one of the leak trays 24a, 24b. This ensures that each of the filter members 26a, 26b will be in the aforementioned oblique/angled (a) position with respect to the longitudinal axis L of the extractor duct 4. In an exemplary embodiment, the lower edge of each filter member 26a, 26b may be supported by the outermost edge of one of the leak trays 24a, 24b.

From Figure 1 and 3 it is further seen that in an embodiment the ventilation system 6 may comprise two fan motors 28a, 28b each of which is connected to the fluid collector housing 18 adjacent to and downstream from one of the two filter members 26a, 26b, and wherein each fan motor 28a, 28b comprises an axis of rotation 01 , 02 which is arranged at an acute/oblique (outward) angle (b) with respect to the longitudinal axis L.

The oblique arrangement of the axis of rotation 01 , 02 of each fan motor 28a, 28b provides advantages to flow performance and noise production. In particular, due to the oblique arrangement of fan motors 28a, 28b a projected area of an inlet opening 30a, 30b of each fan motor 28a, 28b facing a filter member 26a, 26b is increased and as a result a flow area in each of the housing channels C1 , C2 towards a fan motor 28a, 28b remains as large as possible, reducing velocities of the air flows A1 , A2 through the housing channels C1 , C2 and decreasing pressure losses.

Figure 6 shows a cross sectional side view of a cooktop 1 with one 28a of the two fan motors 28a, 28b according to an embodiment of the present invention. As indicated by the embodiment, each fan motor of the two fan motors 28a, 28b may comprise a scroll housing 32a which extends/bends out of a plane which is perpendicular to the axis of rotation 01 , 02, so wherein the scroll housing 32a bends/deviates away out of the aforementioned plane along a bend B as indicated by the arrow“B”. Such a bent scroll housing 32a allows for a compact design in which an outlet end 34a of each fan motor 28a, 28b can be conveniently connected to a vertical downdraft pipe 36 which is located, for example, behind kitchen drawers 38 of a kitchen cabinet K. The bent scroll housing 32a allows each fan motor 28a, 28b to be arranged obliquely at any desired acute angle b whilst keeping the ventilation system 6 compact. Furthermore, the bent scroll housing 32a of each fan motor 28a, 28b still allows for high volume flows and minimizes turbulence and pressure loss whilst enabling a compact connection to the vertical downdraft pipe 36.

The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims.