EP3247952B1

EP3247952B1 - Suction grid for an air guide of a domestic hood, air guide having such grid and domestic hood having such air guide

Info

Publication number: EP3247952B1
Application number: EP16709127.1A
Authority: EP
Inventors: Gennaro Buonomo; Sandrino ROSCINI
Original assignee: Elica SpA
Current assignee: Elica SpA
Priority date: 2015-01-22
Filing date: 2016-01-20
Publication date: 2019-03-20
Anticipated expiration: 2036-01-20
Also published as: TR201905809T4; WO2016116871A1; EP3247952A1; PL3247952T3; ES2721779T3

Description

Field of the Invention

The present invention relates to a suction grid for an air guide of a domestic hood, an air guide having such grid and a domestic hood having such air guide, as defined in the preambles of claims 1, 8 and 12 respectively.

Background art

A suction grid in an air guide for a domestic hood, be it an extractor or a filter hood, is basically provided to avoid the risk that a user may touch with his/her fingers the impeller of the ventilation unit located in the air guide, or to prevent the impeller from being broken due to the intrusion of a foreign body into the impeller, or for similar purposes.
In order to ensure safety during operation of the hood, suction grids include a plurality of spokes, which define openings for the passage of the air extracted, for instance, by the ventilation unit of a domestic hood.
Prior art spokes in suction grids have a constant section throughout their length.
Particularly, the openings in the suction grid are sized in accordance with I international standards such as:

CEI EN 60335-1/EC Safety of household and similar electrical appliances - Safety Part 1: General requirements and
particularly for extractor hoods, CEI EN 60335-2-31 Safety of household and similar electrical appliances Part 2: Particular requirements for range hoods.

For example, a prior art suction grid has spokes arranged in a checkered pattern.
Further spoke arrangements are also known, such as those still having a checkered pattern but with spokes alternated with a plurality of concentric rings or arranged in a pattern that has no regular geometric shape. A suction grid according to the preamble of claim 1 is know from patent document EP-A-2530331 .
Nevertheless, while these arrangements have be found to be adequate in many aspects, they are still affected by various problems, when the suction grid is associated with the air guide of a domestic hood. These drawbacks include:

increased intake air turbulence, such that it may decrease the efficiency of the ventilation unit;
increased aerodynamic noise, such that it may hinder quite operation of the ventilation unit and other problems that would tend to reduce the efficiency of the ventilation unit of the domestic hood.

Object of the Invention

In light of the above described prior art, the object of the present invention is to provide a suction grid having such characteristics as to obviate the above mentioned drawbacks of the prior art.
According to the present invention, this object is fulfilled by a suction grid for an air guide of a domestic hood as defined in claim 1.
The present invention can provide a suction grid that has lower noise levels as well as a reduced flow turbulence, thereby affording improved performances using the same ventilation unit.
This object is also fulfilled by an air guide having the suction grid as defined in claim 8.
The object is finally fulfilled by a hood, be it a filter or an extractor hood, having the air guide with the suction grid, as defined in claim 12.

Brief description of the drawings

The characteristics and advantages of the invention will appear from the following detailed description of one preferred embodiment, which is illustrated without limitation in the annexed drawings, in which:

Figure 1 shows a top view of a suction grid of the present invention;
Figures 2A and 2B show a sectional profile along spokes of the suction grid of Figure 1;
Figure 3A shows a side view of an air guide for a domestic hood with the suction grid of Figure 1 according to the present invention;
Figure 3B shows an exploded view of the parts of the air guide of Figure 3A;
Figure 3C shows a side view of the air guide of Figure 3A;
Figure 3C' shows a sectional view of the air guide of Figure 3A;
Figure 3D shows a view of one of the two half-shells of the air guide with the suction grid of Figure 1.

Detailed description

Referring to the accompanying figures, numeral 1 designates a suction grid, particularly designed to be installed on an air guide 2, in turn located in a domestic hood, which may be either an extractor or a filter hood (not shown).
It shall be noted that the term suction grid is intended to cover any type of device that acts as a grid or as a protection member for a motor unit for extracting gases.
Referring now to Figure 1, it shall be noted that the grid 1 defines a central area 10 and a peripheral edge 11 and comprises a first plurality of spokes 12 in mutually spaced relationship.
It shall be particularly noted that each spoke of the first plurality of spokes 12 extends along a curvilinear path 13 from the central area 10 toward the peripheral edge 11 (in the direction indicated by the arrow of the curvilinear path 13 of Figure 2A).
The first plurality of spokes 12 are more closely spaced proximate to the central area 10 and become less densely spaced toward the peripheral edge 11 of the grid 1. Each spoke of the first plurality of spokes 12 defines a profile 14 that is warped around the path 13.
It shall be noted that the term warped profile is intended to designate the progressively changing angles formed by the profile section in the three dimensions along the path 13.
The grid 1 defines a vertical axis X-X that extends through a point C in the central area 10, such point representing the geometric center of the grid and the axis X-X being an axis for the grid itself.
In view of this, the first plurality of spokes 12 is periodic about said axis X-X.
Particularly, the profile 14, also referring to Figure 2A, in any section normal to the path 13 (ideally) defines a parallelogram excepting the radii of curvature.
This parallelogram has a front side 14A, a rear side 14B, opposite to the front side 14A, an underside 14C and a topside 14D, opposite to the underside 14C.
In one aspect of the present disclosure, the ratio of the front side 14A or the rear side 14B to the underside 14C or the topside 14D changes from the central area 10 toward the peripheral edge.
In other words, the ratio of the front side 14A or the rear side 14B to the underside 14C or the topside 14D at a given point of the path 13 is not the same as the ratio that is found at a point that precedes or follows the point being considered.
In one aspect:

the front side 14A has a direction of extension parallel to the direction of extension of the rear side 14B, the length of the front side 14A is equal to the length of the rear side 14B and this length remains constant along the path 13, for example as shown in Figure 2A, is "a";
the underside 14C has a direction of extension parallel to the direction of extension of the topside 14C, the length of the underside 14C is equal to the length of the topside 14D and this length increases in the direction from the central area 10 to the peripheral edge 11 of the grid 1, for example, as shown in Figure 2A, from "b₁" to "b_n".

In other words, also referring to Figure 2A, the front side 14A and the rear side 14B of the profile 14 are shown to be constant and equal to "a" in all the sections normal to the path 13, whereas the underside 14C and the topside 14D increase from the center 10 toward the peripheral edge 11, from the length "b₁" to the length "b_n".
In other words, the a to b ratio for each spoke of the first plurality of spokes 12 (i.e. the parallelogram) is not constant throughout the path 13, but decreases in the direction from the central area 10 to the peripheral edge 11 of the grid 1, which means that the ratio of the front side 14A or the rear side 14B to the underside 14C or the topside 14D proximate to the central area 10, e.g. a/b₁, is greater than the ratio of the front side 14A or the rear side 14B to the underside 14C or the topside 14D proximate to the peripheral edge, e.g. a/b_n.
In one aspect, the grid 1 comprises a plurality of rings 20, which are preferably coaxial with the axis X-X.
It shall be noted that each ring of the plurality of rings 20 is connected to the front side 14A of each spoke of the first plurality of spokes 12.
According to a preferred embodiment of the grid 1, the plurality of rings 20 comprises at least three rings, each having a diameter value D that increases from the center C toward the peripheral edge 11.
Still referring to Figure 1, it shall be noted that the grid 1 comprises a second plurality of mutually spaced spokes.
Preferably, each spoke of the second plurality of spokes 30 extends along a curvilinear path 31 from one of the aforementioned rings 20 toward the peripheral edge 11 (in the direction indicated by the arrow of the curvilinear path 13 of Figure 2A).
The second plurality of spokes 30 are more closely spaced proximate to the central area 10 and become less densely spaced toward the peripheral edge 11 of the grid 1.
The second plurality of spokes 30 is also periodic about said axis X-X.
As shown in Figure 1, each spoke of the second plurality of spokes 30 is interposed between two spokes of said first plurality of spokes 12.
Particularly, the path 31 along which each spoke of the second plurality of spokes 30 extends is substantially similar in its form to the path 13 along which each spoke of the first plurality of spokes 12 extends.
According to a preferred aspect, each spoke of the second plurality of spokes 30 defines a profile 32 that is warped around the path 31.
Particularly, the profile 32, also referring to Figure 2B, in any section normal to the path 31 (ideally) defines a parallelogram excepting the radii of curvature.
This parallelogram has a front side 32A, a rear side 32B, opposite to the front side 32A, an underside 32C and a topside 32D, opposite to the underside 32C.
In one aspect of the present disclosure, the ratio of the front side 32A or the rear side 32B to the underside 32C or the topside 32D changes from one of the aforementioned rings 20 toward the peripheral edge 11.
In other words, the ratio of the front side 32A or the rear side 32B to the underside 32C or the topside 32D at a given point of the path 31 is not the same as the ratio that is found at a point that precedes or follows the point being considered.
In one aspect:

the front side 32A has a direction of extension parallel to the direction of extension of the rear side 32B, the length of the front side 32A is equal to the length of the rear side 32B and this length remains constant along the path 31, for example as shown in Figure 2B, is "c";
the underside 32C has a direction of extension parallel to the direction of extension of the topside 32C, the length of the underside 32C is equal to the length of the topside 32D and this length increases in the direction from the central area 10 to the peripheral edge 11 of the grid 1, for example, as shown in Figure 2B, from "b1" to "bn".

In other words, also referring to Figure 2B, the front side 32A and the rear side 32B of the profile 14 are shown to be constant and equal to "c" in all the sections normal to the path 31, whereas the underside 32C and the topside 32D increase from the center 10 toward the peripheral edge 11, from the length "b1" to the length "bn".
In other words, the c to b ratio for each spoke of the second plurality of spokes 30 (i.e. the parallelogram) is not constant throughout the path 31, but decreases in the direction from the central area 10 to the peripheral edge 11 of the grid 1, which means that the ratio of the front side 32A or the rear side 32B to the underside 32C or the topside 32D proximate to the central area 10, e.g. c/b₁, is greater than the ratio of the front side 32A or the rear side 32B to the underside 32C or the topside 32D proximate to the peripheral edge, e.g. c/b_n.
Referring now to Figure 3D, as described in greater detail hereinafter, showing a half-shell of an air guide for a domestic hood with the grid 1, it will be noted that each spoke of the first or second plurality of spokes 12, 30 has:

a) an angle α ranging from 5° to 15° and preferably of 8°, such angle α being determined relative to the plane orthogonal to X-X and the lines containing the topsides 14C and 32C of the profiles 14, 32;
b) proximate to the peripheral edge 11, i.e. in the area in which each spoke of the first or second plurality of spokes 12, 30 reaches the peripheral edge 111, an angle β ranging from 25° to 35°, preferably of 30°, such angle β being determined relative to the chord that joins the ends of the paths 13 and 31;
c) proximate to the central area 10, i.e. in the area in which each spoke of the first plurality of spokes 12 reaches the central area, an angle γ ranging from 25° to 35°, preferably of 30°, such angle γ being determined relative to the chord that joins the ends of the path 13;
d) proximate to the central area 10, i.e. in the area in which each spoke of the second plurality of spokes 30 reaches the central area, an angle δ ranging from 30° to 40°, preferably of 35°, such angle γ being determined relative to the chord that joins the ends of the path 31.

Due to the conformation of the first plurality of spokes 12 a suction grid 1 is obtained, that has lower noise levels as well as a reduced flow turbulence, thereby affording improved performances using the same ventilation unit.
These results are also maximized by the presence of the second plurality of spokes 30, as shown by the tables that are given and commented hereinbelow.
The conformation of the first and second pluralities of spokes 12, 30 can define openings that comply with the aforementioned applicable standards, ensuring user safety during normal operation of the grid.
Referring now to Figures 3A to 3D, there is shown the air guide 2 for the domestic hood.
The air guide 2 has an axis of rotation R about which a housing 40 is defined, which has a first axial suction port 41 and a second axial suction port 42 opposite to the first suction port 41 and a tangential outlet port 43.
As shown by Figures 3A to 3D:

the first port 41 is closed by the suction grid 1 and, particularly, such suction grid 1 is made of one piece with the housing 40, e.g. by molding;
the second port 42 is closed by a prior art suction grid 42A or, alternatively, may be closed by the grid 1 and, particularly, such suction grid 42A may be formed separately from the housing 40 and connected thereto by usual connection techniques.

The air guide 2 comprises a drive unit 44B composed of an electric motor 44 and an impeller 45 connected with a drive shaft 44A of the electric motor 44, both located within the housing 40 that acts as an air guide.
The housing 40 has a substantially toroidal shape with two side walls 46, 47 delimiting the suction ports 41, 42, and a peripheral wall 48 (known as volute), which forms a substantially tangential portion defining the port 43.
The housing 40 is composed of two half- shells 49, 50, which are connected together along a junction line 52 in the peripheral wall 48 by complementary junction edges 52 having a step-like cross section, to thereby form a labyrinth connection interface, and a plurality of alignment pins 53 projecting out of the junction edge 52 of one of the half- shells 49, 50 respectively, and received in corresponding alignment holes 54 formed in the junction edge 52 of the other half-shell.
These characteristics afford simple, sturdy and highly accurate assembly of the housing.
According to one embodiment, the suction ports 41, 42 have a circular shape and are coaxial with the impeller 45 (which also has a circular shape) and the inside diameter D1 of the edge of the suction port 41, 42 (not considering the support portions) is smaller than the inside diameter D2 of the end of the impeller that faces it.
Particularly, also referring to Figure 3C, the first and second suction ports 41, 42 have the same axis of rotation R-R (see Figure 3B) which is also their axis of symmetry and coincides with the axis X-X of the grid 1.
The tangential port 42 has its own plane of symmetry P (see Figure 3C) perpendicular to the axis of symmetry R of the first and second axial ports 41, 42.
The axis of rotation (or symmetry) R-R and the plane of symmetry P define a center C' at their intersection.
In one aspect, the two half- shells 49, 50 of the housing 40, which compose the air guide 2 are not symmetrical, which means that they are dissymmetrical.
Therefore, advantageously the electric motor 44 is at least partially offset from such center C' toward the second port 42.
The dissymmetry of the two half- shells 49, 50 of the air guide is defined considering the plane of symmetry P (see Figure 3C) of the tangential port 43, which is orthogonal to the axis of symmetry R-R of the first and second axial ports 41, 42.
The distance between the sidewall 46 and this plane of symmetry P is typically equal to the distance between the sidewall 47 and the plane P in prior art air guides.
In the air guide 2 of the present disclosure, the distance L1 of the sidewall 47, i.e, the sidewall opposite to the first port 41, is greater than the distance L2 between the sidewall 46, i.e. the sidewall opposite to the second port 42 and the plane of symmetry P.
In other words, the distance of the sidewall 47 that delimits the second axial port 42 of the air guide 2 is greater than the distance between the sidewall 46, that delimits the first axial port 41 of the air guide 2, and the plane of symmetry P of the tangential port 43, which extends through the plane of symmetry P and is orthogonal to the axis of symmetry R-R of the first and second axial ports 41, 42.
As a result, the motor 44 will be located to a to a greater distance outside the impeller 45 than it would normally be, whereby the electric motor 44 will be at least partially offset from such center C' toward the second port 42.
In one aspect, the electric motor 44 extends at least partially beyond the predetermined length L of the impeller 45 (when considered along a direction of extension between the first port 41 and the second port 42) toward the second port 42.
These arrangements of the motor 44, taken ether individually or in combination, afford improved air extraction through the suction grid 1 thereby enhancing the fluid-dynamic efficiency of the air guide.
The air guide 2 can be advantageously mounted to a domestic hood.
Particularly, such hood comprises a housing frame in which the air guide 2 is accommodated for extracting and exhausting gases, e.g. during food preparation.
For this purpose, the housing frame of the hood comprises a gas extraction inlet and an outlet, through which the extracted gases are exhausted, with or without filtering.
As is known per se, the air guide 2 is configured to be in fluid communication with the inlet and the outlet of the hood frame, for extraction and exhaustion of gases.
In order to confirm the better performances achieved using the suction grid 1 of the present disclosure, in terms of noise level and fluid-dynamic efficiency, the Applicant made specific tests on the suction grid 1 installed on the air conveyor 2, as compared with a standard air conveyor having a standard grid, within the same hood.

The following table shows the values obtained from the tests. The table proves that the use of the suction grid 1 with the air guide 2 of the present invention affords remarkable improvements in fluid-dynamic efficiency, i.e. from 26% to 37%, and a reduction of noise from 69 dBA to 67 dBA.

AIR GUIDE	MOTOR	IMPELLER	FLOW RATE (M³/H)	POWER OVER FDE (W)	RPM FDE	FDE (%)	NOISE Lwa (dBA)	RPM
Std.	Std.	59p	670	155	2580	26	69	1530
Inventive	Std.	59p	630	140	2650	37	67	1330

Referring to Figure 3C, in one aspect of the present invention, the area of the tangential outlet edge 43, designated as a circumference 60, has a variable section, a somewhat converging conduit being so formed between the impeller 45 and the peripheral wall 48. This variable section has the purpose of reducing the perturbations induced by the presence of the outlet edge 43 on the flow, to maintain a low noise level.
Still referring to Figure 3C, in one aspect of the present invention, the involute surface of the peripheral wall 48, designated by the circle 61, is always parallel to the blades of the impeller 45. With this arrangement, the airflow extracted through the suction grid may be maintained as laminar as possible.
Those skilled in the art will obviously appreciate that a number of changes and variants may be made to the suction grid of the invention as described hereinbefore to meet specific needs, without departure from the scope of the invention, as defined in the following claims.

Claims

A suction grid (1) for an air guide (2) of a domestic hood, comprising a first plurality of mutually spaced spokes (12), said grid defining a central area (10) and a peripheral edge (11), each spoke of said first plurality of spokes (12) extending along a first curvilinear path (13) from said central area (10) toward said peripheral edge (11), each spoke of said first plurality of spokes (12) defining a profile (14), which is warped around said first curvilinear path (13), said profile (14), in any section normal to said first curvilinear path (13), defining a front side (14A), a rear side (14B), opposite to said front side (14A), an underside (14C) and a topside (14D) opposite to said underside (14C), wherein the ratio of said front side (14A) or rear side (14B) to said underside (14C) or topside (14D) changes from said central area (10) toward said peripheral edge (11),
said ratio decreasing from said central area (10) toward said peripheral edge (11), characterized in that
- said front side (14A) has a direction of extension which is parallel to the direction of extension of said rear side (14B), the length of said front side (14A) being equal to the length of the rear side (14B) and said length remaining constant along said first curvilinear path (13);

- said underside (14C) has a direction of extension parallel to the direction of extension of said topside (14D), the length of said underside (14C) being equal to the length of said topside (14D) and said length progressively increasing along said first curvilinear path (13).
A suction grid for an air guide of a domestic hood as claimed in claim 1, wherein said suction grid (1) defines an axis (X-X) and comprises a plurality of rings (20), which are coaxial with said axis (X-X), each ring of said plurality of rings (20) being connected to said front side (14A) of each spoke of said first plurality of spokes (12).
A suction grid for an air guide of a domestic hood as claimed in claim 2, wherein said plurality of rings (20) comprises at least three rings, each having a diameter (D) that increases from the center (C) toward the peripheral edge (11).
A suction grid for an air guide of a domestic hood as claimed in claim 2, comprising a second plurality of mutually spaced spokes (30), each spoke of said second plurality of spokes (30) extending along a second curvilinear path (31) from one of said rings (20) toward said peripheral edge (11), each spoke of said second plurality of spokes (30) defining a profile (32), which is warped around said second curvilinear path (31), said profile (32), in any section normal to said second curvilinear path (31), defining a front side (32A), a rear side (32B), opposite to said front side (32A), an underside (32C) and a back side (32D) opposite to said underside (32C), wherein the ratio of said front side (32A) or rear side (32B) to said underside (32C) or back side (32D) changes from one of said rings (20) toward said peripheral edge (11).
A suction grid for an air guide of a domestic hood as claimed in claim 4, wherein said ratio decreases from one of said rings (20) toward said peripheral edge (11).
A suction grid for an air guide of a domestic hood as claimed in claim 5, wherein:
- said front side (32A) has a direction of extension which is parallel to the direction of extension of said rear side (32B), the length of said front side (32A) being equal to the length of said rear side (32B) and said length remaining constant along said second curvilinear path (31);

- said underside (32C) has a direction of extension parallel to the direction of extension of the topside (32D), the length of said underside (32C) being equal to the length of said topside (32D) and said length progressively increasing along said second curvilinear path (31).
A suction grid for an air guide of a domestic hood as claimed in claim 4, wherein each spoke of said second plurality of spokes (30) is interposed between two spokes of said first plurality of spokes (12).
An air guide for a domestic hood, having an axis of rotation (R-R) and comprising:
- a housing (40) having a first axial suction port (41) and a second axial suction port (42) opposite to the first suction port (41) and a tangential outlet port (43);

- a drive unit (44B) placed in the housing (40) and having an electric motor and an impeller (45) connected with a drive shaft (44a) of the electric motor (44);

- said first port (41) comprises a suction grid (1);
characterized in that said suction grid (1) is as claimed in any of the preceding claims from 1 to 7.
An air guide for a domestic hood as claimed in claim 8, wherein said housing (40) is composed of two half-shells (49, 50) connected together, said two half-shells (49, 50) being asymmetric.
An air guide for a domestic hood as claimed in claim 9, wherein said first axial suction port (41) and said second axial suction port (42) share said axis of rotation (R-R), said tangential port (43) has its own plane of symmetry (P) perpendicular to the axis of rotation (R-R) of said first and second axial ports (41, 42), the distance (L1) of said side wall (47) that delimits said second axial port (42) is greater than the distance (L2) between said side wall (46) that delimits said first axial port (41) and a plane of symmetry (P) of the tangential port (43) which passes through said plane of symmetry (P) and is orthogonal to the axis of rotation (R-R) of said first and second axial ports (41, 42).
An air guide for a domestic hood as claimed in claim 9, wherein said impeller (45) extends through a predetermined length (L) along a direction of extension between said first axial port (41) and said second axial port (42), said electric motor (44) extending at least partially beyond said predetermined length (L) of said impeller (45) toward said second axial port (42).
A domestic hood comprising a containing frame having an inlet and an outlet, an air guide (2) being accommodated in said containing frame, said air guide (2) being in fluid communication with said inlet and said outlet for extracting and exhausting gases, characterized in that said air guide (2) is as claimed in any of the preceding claims 8 to 11.