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(11) | EP 1 070 920 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Suction unit for a cooker hood |
| (57) A suction unit for a cooker hood comprises a casing (2) which is designed in use
to be disposed above a food cooker top, and an air outlet pipe (6) which is disposed
above the casing (2) and has at least an initial section (6a) which is substantially
vertical. The suction unit comprises a direct-current electric motor (9) with a wide
range of speeds of rotation, for example a brushless motor, and at least one fan wheel
(12;12a-12c) which is rotated by the electric motor (9). The fan wheel (12;12a-12c)
is designed to be accommodated inside the initial section (6a) of the outlet pipe. |
[0002] As is known, a cooker hood comprises a casing which is installed such that it is disposed above a cooker top, and inside which there is generally accommodated a sheet of absorbent material. The casing also accommodates a suction unit, which comprises a conveyor unit to convey air and fumes to a suction fan wheel, which is actuated by an electric motor, and conveys the air and fumes to an outlet pipe. The outlet pipe has an initial section which is substantially vertical, and, after a path which is more or less winding, but which comprises at least one elbow, opens into a flue, which is fitted through the wall.
[0004] According to a first type of known suction unit, which is designed for economical cooker hoods, the motor is a two-pole asynchronous motor, which is supplied by the mains voltage (50Hz or 60Hz), and actuates a fan wheel of the radial type, and the conveyor unit consists of a plastic or sheet metal shell, which also acts as a support for the fan wheel and motor. The fan wheel is located in a position which is eccentric relative to the axis of the outlet pipe, and rotates on a horizontal plane, i.e. it has an axis of rotation which is parallel to the axis of the outlet pipe.
[0005] In this first type of suction unit, the air and fumes are sucked vertically through an aperture in the conveyor unit, which is disposed beneath the fan wheel, and are impelled horizontally towards the aperture of the outlet pipe.
[0006] The air and fumes are then forced to follow a path in the shape of an 'S', consisting of a vertical section below the hood, a horizontal section inside the conveyor unit, and a section which is vertical once more in the outlet pipe. The hood thus introduces two elbows into the path of the air and fumes sucked up, in addition to the at least one elbow which is always provided along the outlet pipe, and to the final elbow, to which the air and fumes sucked up are conveyed at the intake of the flue. There are thus significant losses of load, which, taking into consideration also the limited number of revolutions which can be obtained by the asynchronous motor which is supplied by the mains voltage (fewer than 3000 revs/minute, with mains voltage of 50Hz), make the hood inefficient. The suction capacity of these hoods is typically approximately 200 m3/hour.
[0007] In a second type of known suction unit, which is designed for more costly hoods, the motor is always of the two-pole asynchronous type, supplied by the mains voltage, and the fan wheel which it actuates is again of the radial type. The conveyor unit, which is made of sheet metal, is on the other hand in the form of a volute. In addition, the fan wheel has dimensions larger than those of the unit of the first type previously described, and works in a vertical position, i.e. with the axis of rotation at right angles to the axis of the outlet pipe.
[0008] In this second type of suction unit, the air and fumes which enter the hood vertically are sucked inside the conveyor unit, through apertures in the lateral surfaces of the volute, and are impelled vertically into the outlet pipe. The hood introduces a single elbow in the path of the air and fumes sucked up, in addition to which, as in the previous case, there are the at least one elbow provided along the outlet pipe, and the final elbow at the intake of the flue. The hood is more efficient than the previous type, since it has a capacity which is typically equivalent to approximately 800 m3/hour. In addition, the vertical dimension of the hood is larger, owing to the vertical arrangement of the fan wheel. This conflicts with the desire of users and interior decorators to restrict as much as possible the vertical dimensions of the hood.
[0009] In view of the state of the art described, an object of the present invention is to provide a suction unit for a cooker hood, which eliminates the problems previously described according to the known art, and which in particular is efficient, whilst having reduced dimensions.
[0010] According to the present invention, this object is achieved by means of a suction unit for a cooker hood, comprising a casing which is designed in use to be disposed above a food cooker top, and an air outlet pipe which is disposed above the casing and has at least one initial section which is substantially vertical, characterized in that it comprises a direct-current electric motor with a wide range of speeds of rotation, and at least one fan wheel, which is rotated by the electric motor, the said at least one fan wheel being designed to be accommodated inside the said initial section of the outlet pipe.
[0011] The characteristics and advantages of the present invention will become more apparent from the following detailed description of a practical embodiment, and two variants, shown purely by way of non-limiting example in the attached drawings, in which:
Figure 1 shows in cross section a cooker hood which is provided with a suction unit according to the present invention;
Figure 2 is a view in cross section according to the line II-II;
Figure 3 shows highly schematically a control circuit of a motor for the suction unit in Figure 1;
Figure 4 shows a variant of the hood in Figure 1;
Figure 5 is a view in cross section according to the line V-V in Figure 4;
Figure 6 shows schematically the functioning of the hood in Figure 4; and
Figure 7 shows a further variant of the suction unit for a hood according to the invention.
[0012] With reference to Figure 1, a cooker hood, which is generally indicated as 1, comprises a box-shaped casing 2, which is closed at the base by a perforated plate 3, and inside which there is normally accommodated a sheet 4 of absorbent material. At the top, the casing has an aperture 5 for connection of an outlet pipe 6, which has an initial section 6a which is substantially vertical, and which follows a path which is more or less winding, in which there is always provided at least one elbow 7, and opens into a flue 8.
[0013] Inside the initial section 6a of the pipe 6, there is accommodated an electric motor 9, which for example is mounted suspended centrally relative to the pipe 6a, by means of three supports 10, which are at 120° (Figure 2). Via a shaft 11, the motor 9 rotates a fan 12 of an axial type, with an axis of rotation which coincides with, or more generally is substantially parallel to the axis of the initial section 6a of the outlet pipe 6. The fan 12 must have dimensions which allow it to be accommodated inside the pipe 6a, and is therefore rather small.
[0014] The motor 9 is advantageously of the brushless type, is supplied as known with direct current, is controlled by an electronic circuit board, and, although it has limited dimensions, is able to achieve very high speeds of rotation, for example of up to 15,000 revs/minute, with a domestic mains voltage of 50Hz, and which are thus much higher than the speeds which can be achieved by means of the asynchronous motors. Owing to the high speed of rotation which can be achieved, the efficiency of suction is guaranteed, despite the reduced dimensions of the fan 12. It is thus possible to obtain an air flow greater than 400 m3/hour, with a pressure of 30-40 mmH2O.
[0015] In use, the hood is installed in position above a cooker top 13. The air and fumes 14 which are produced during the process of cooking food enter the casing 2 of the hood 1 vertically via the perforated plate 3, pass through the sheet of absorbent material 4, and are then sucked by the fan 12 inside the outlet pipe 6a, and are then impelled again vertically, towards the flue 8.
[0016] Figure 3 shows schematically a supply and control circuit for the brushless motor 9. From the alternating mains voltage VAC, a rectifier and stabilization circuit 15 generates a direct voltage VCC, for supply of an electronic circuitry 16 which controls the motor 9.
[0017] Advantageously, the electronic circuitry 16 can be equipped with one or a plurality of inputs 17a-17k, for an equivalent number of sensors 18a-18n, which can detect environmental parameters, such as a temperature sensor, a smoke sensor, a gas sensor to detect any leakages, and in general sensors for physical quantities which are to be controlled. By means of the sensors and the electronic circuitry, the hood is provided with intelligence which can adapt the functioning, in terms for example of speed of rotation of the fan 12, to the environmental levels of the physical quantities controlled. For example, the speed of rotation, and even switching on of the hood, can be determined by the density of the fumes, or by their temperature, or by the presence of leakages of gas, derived for example from unforeseen extinction of the cooking flame.
[0018] The advantage of the suction unit for a hood according to the invention consists in the fact that inside the hood, the air and fumes do not have to pass via any elbow: the path of the air and fumes inside the hood is substantially entirely vertical. This reduces considerably losses of load, and increases the efficiency of suction.
[0019] In addition, since the motor and fan are accommodated in the outlet pipe 6, and it is not necessary to provide any conveyor unit, the casing 2 contains only the sheet of absorbent material. The vertical dimension of the casing 2 can thus be extremely limited, thus complying with the preferences of users and interior decorators.
[0020] In a view similar to that of Figure 1, and using identical reference numbers for parts which are the same or similar, Figure 4 shows a variant of the hood previously described. Inside the outlet pipe 6, and preferably immediately downstream from the fan 12, there is disposed a diaphragm 19, which can be seen in plan view in Figure 5, with a plurality of fins 20, which are inclined and disposed in the shape of a dial from a central hub 25 towards a peripheral ring 26. The diaphragm 19, which is secured to the inner wall of the outlet pipe 6, has a shape similar to that of an axial fan wheel. As illustrated schematically in Figure 6, the diaphragm 19 permits regular discharge of the air 21 which is impelled by the fan 12, at the same time impeding reflux of air 22 caused by friction on the inner wall of the outlet pipe 6, and by turbulence created in the vicinity of the fan 12. The effect of the diaphragm 19 is to sub-divide the space inside the outlet pipe 6 into two chambers 23a, 23b, which are distinct from one another, thus allowing the air impelled by the fan 12 to flow easily from the first chamber 23a to the second chamber 23b, but preventing the air in the chamber 23b from flowing back into the chamber 23a.
[0021] Finally, Figure 7 shows a further variant of the above-described hood, which, instead of a single fan 12 and a single diaphragm 19, uses a column of (three in the example, but optionally more) fans 12a-12c, and three respective diagrams 19a-19c, of the type shown in Figures 4 and 5. Advantageously, the three fans 12a-12c are rotated by the single motor 9, via a drive shaft 24, which extends through corresponding axial holes provided in the hubs 25a, 25b of the diaphragms 19a, 19b.
1. Suction unit for a cooker hood, comprising a casing (2) which is designed in use to
be disposed above a food cooker top, and an air outlet pipe (6) which is disposed
above the casing (2) and has at least one initial section (6a) which is substantially
vertical, characterized in that it comprises a direct-current electric motor (9) with
a wide range of speeds of rotation, and at least one fan wheel (12;12a-12c), which
is rotated by the electric motor (9), the said at least one fan wheel (12;12a-12c)
being designed to be accommodated inside the said initial section (6a) of the outlet
pipe.
2. Suction unit according to Claim 1, characterized in that the said electric motor (9)
is a brushless motor.
3. Suction unit according to Claim 2, characterized in that the said electric motor (9)
is designed to be accommodated inside the said initial section (6a) of the outlet
pipe (6), coaxially relative to an axis of rotation of the said at least one fan wheel
(12;12a-12c).
4. Suction unit according to Claim 3, characterized in that the said at least one fan
wheel (12;12a-12c) is accommodated in the initial section (6a) of the outlet pipe
(6), such as to have an axis of rotation which is parallel to an axis of the initial
section (6a) of the outlet pipe.
5. Suction unit according to Claim 4, characterized in that the said at least one fan
wheel is accommodated in the initial section (6a) of the outlet pipe (6), such that
the axis of rotation of the said at least one fan wheel (12;12a-12c) coincides with
the axis of the said initial section (6a) of the outlet pipe (6).
6. Suction unit according to Claim 4 or Claim 5, characterized in that the said at least
one fan wheel (12;12a-12c) is an axial fan.
7. Suction unit according to Claim 6, characterized in that it comprises a diaphragm
(19;19a-19c) with an arrangement in the form of a dial of inclined fins (20), which
is designed to be accommodated inside the initial section (6a) of the outlet pipe
(6), downstream from the at least one fan wheel (12;12a-12c).
8. Suction unit according to Claim 7, characterized in that it comprises, designed to
be accommodated inside the initial section (6a) of the outlet pipe (6), a column of
fan wheels (12a-12c), downstream from each of which there is disposed a respective
diaphragm (19a-19c).
9. Suction unit according to Claim 8, characterized in that the said fan wheels (12a-12c)
are all rotated by the said electric motor (9) via a drive shaft (24) which is parallel
to the axis of the initial section (6a) of the outlet pipe (6).
10. Suction unit according to any one of the preceding claims, comprising electronic control
circuitry for the said motor (9), characterized in that the said electronic circuitry
(16) comprises at least one input (17a-17k) for respective sensor means (18a-18k),
to detect environmental variables, which condition the control of the motor (9).
11. Suction unit according to Claim 10, characterized in that the said sensor means (18a-18k)
consist of one from amongst a temperature sensor, a smoke density sensor, or a gas
sensor.
12. Cooker hood, comprising a casing which is designed in use to be disposed above a food
cooker top, an air outlet pipe (6) which is disposed above the casing (2) and has
at least an initial section (6a) which is substantially vertical, and a suction unit
(9-12;9-12,19;9-11,12a-12c,19a-19c), characterized in that the said suction unit is
in accordance with any one of the preceding claims.