[0001] The invention relates to a hood extractor for extracting contaminated air from appliances.
The invention also relates to a method of operating a hood extractor.
[0002] In commercial kitchens contaminated air produced by cooking appliance is extracted
by a hood extractor mounted above the appliance. The hood extractor comprises a housing
through which air to be extracted flows. The housing has an air inlet, through which
air is conducted into the housing, and an air outlet, through which air is removed
from the housing. The air outlet is connected to an exhaust duct through which air
is discharged to an atmosphere. Air is sucked through the housing by a fan connected
to the exhaust duct. Additionally, the hood extractor comprises a fire damper arranged
in the air outlet. The fire damper prevents the spread of fire from the hood extractor
into the exhaust duct in case of fire. The hood extractor also comprises a control
damper, by which the exhaust air flow rate through the housing is set as desired.
The position of the control damper is set during the commissioning of the hood extractor
such that a desired air flow rate through the hood extractor is achieved. Thereafter,
the control damper is maintained in this position during the operation of the hood
extractor.
[0003] Since in commercial kitchens several hood extractors are connected to the exhaust
duct and the fan of the exhaust duct operates at a constant speed, the air flow rates
through hood extractors vary depending on the operational status of the cooking appliances.
For example, if the cooking appliance is switched off, the fire damper of the hood
extractor above said appliance is closed and no exhaust air flows through the hood
extractor. As a result, the exhaust air flow rate through the operative hood extractors
increases. Respectively, when said appliance is switched on, the fire damper of the
hood extractor above the appliance is opened and exhaust air flows through the hood
extractor. Consequently, the exhaust air flow rates through the other hood extractors
connected to the exhaust duct decrease.
[0004] If the exhaust air flow rates of the hood extractors are too high, energy consumption
and thus the operating costs of the ventilation system increase. On the other hand,
if the exhaust air flow rates are too low, the ventilation of kitchen is not sufficient.
[0005] The object of the present invention is to provide an improved hood extractor.
[0006] This object can be achieved by a hood extractor according to independent claim 1
and a method according to claim 10.
[0007] The hood extractor according to the invention comprises a housing through which air
to be extracted is arranged to flow, an air inlet for conducting air into the housing,
an air outlet for removing air from the housing and a fire damper arranged in the
air outlet. Additionally, the hood extractor comprises a control device for controlling
air flow rate through the housing during an operation of the hood extractor.
[0008] In the method according to the invention air to be extracted is conducted through
the housing of the hood extractor. Additionally, the air flow rate through the housing
during the operation of the hood extractor is controlled by a control device.
[0009] The hood extractor according to the invention has a number of advantages. The exhaust
air flow rate through the extractor hood can be maintained at an optimal or desired
level despite the operational status of the other hood extractors connected to the
exhaust duct. Therefore, the operation costs of the kitchen ventilation system can
be reduced. The hood extractor according to the invention can also have a simple structure,
and therefore be inexpensive to manufacture. Additionally, the invention can be utilized
both in new installations and modernizations of existing hood extractors.
[0010] In the following the invention will be described by way of examples with reference
to the accompanying drawings, in which:
Fig. 1 is a cross-sectional view of a hood extractor according to an embodiment of
the invention, and
Fig. 2 is a cross-sectional view of a hood extractor according to another embodiment
of the invention.
Figs. 1 and 2 show hood extractors 1 for extracting air from kitchens. In kitchens
contaminated air and/or steam from cooking appliance(s) 8, such as a stove, is extracted
by the hood extractor 1, which is mounted above the cooking appliance(s) 8. The hood
extractor 1 can be used in ship kitchens, land-based kitchens, such as kitchens of
restaurants and hotels, and other commercial kitchens.
[0011] The hood extractor 1 comprises a housing 2, through which air to be extracted is
arranged to flow. The housing 2 is provided with an air inlet 3 for conducting air
from the kitchen into the housing 2 and an air outlet 4 for removing air from the
housing 2. The air outlet 4 is connected to an exhaust duct 9, through which air is
conducted to the atmosphere. Air is sucked through the housing 2 by a fan 10 installed
in the exhaust duct 9. The hood extractor 1 comprises a hood 11, which prevents contaminated
air from escaping to the kitchen and directs air toward the air inlet 3.
[0012] A filter 7 such as a grease filter for collecting grease and/or other impurities
from the air flow is arranged in the housing 2 between the air inlet 3 and the air
outlet 4. The filter 7 can be a mesh or baffle filter or a hybrid of mesh filter and
baffle filter. The filter 7 is installed between a front wall and a rear wall of the
housing 2 so that all the air flowing from the air inlet 3 to air outlet 4 passes
through the filter 7.
[0013] The hood extractor 1 further comprises a fire damper 12, which is installed in the
air outlet 4. The fire damper 12 prevents the spread of fire and/or smoke from the
hood extractor 1 into the exhaust duct 9 in case of fire. The fire damper 12 is on/off
controlled. Thus, the fire damper 12 has only an open position and a closed position,
without intermediate positions between the open position and the closed position.
The fire damper 12 is gas tight in the closed position. In ships the fire damper 12
must meet the IMO/SOLAS requirements.
[0014] The hood extractor 1 comprises a control device 13, such as a control damper, for
controlling flow rate (volume flow rate) of exhaust air through the housing 2 during
the operation of the hood extractor 1. The control device 13 is arranged automatically
i.e. without human intervention to control the air flow rate through the housing 2.
The air flow rate through the housing 2 is controlled by adjusting effective cross
sectional flow area through the housing 2.
[0015] In the embodiment of fig. 1 the control device 13 is installed in the air outlet
4 and in the embodiment of fig. 2 in the air inlet 3. The control device 13 comprises
an actuator 14 by which the position of control device 13 can be adjusted. The actuator
14 can be electric, pneumatic, hydraulic or mechanical.
[0016] In the embodiment of fig. 1 the hood extractor 1 is provided with a pressure 15 sensor
for measuring air pressure inside the housing 2. The pressure sensor 15 measures the
air pressure inside the housing 2 at a location upstream of the control device 13.
The hood extractor 1 may also be provided with a further pressure sensor 16 for measuring
the air pressure outside the housing 2, for example in the room or space, such as
kitchen, where the cooking appliance 8 is installed.
[0017] The control device 13 is arranged to control the air flow rate through the housing
2 based on the air pressure in the housing 2. In this case, the control is based on
the air pressure measurement of the pressure sensor 15. The hood extractor 1 is also
provided with a controller 17 configured to receive measurement data from the pressure
sensor 15 and operate the control device 13 in response to the measurement data. The
controller 17 is configured to operate the control device 13 such that a predetermined
air pressure in the housing 2 and thus the air flow rate through the housing 2 is
achieved.
[0018] Alternatively, the control device 13 is arranged to control the air flow rate through
the housing 2 based on an air pressure difference between inside and outside of the
housing 2. In this case, the control is based on the air pressure measurement of the
pressure sensor 15 and the further pressure sensor 16. The controller 17 is configured
to receive measurement data from the pressure sensor 15 and the further pressure sensor
16 and operate the control device 13 in response to the measurement data. The controller
17 is configured to operate the control device 13 such that a predetermined air pressure
difference between the inside and outside of the housing 2 and thus the air flow rate
through the housing 2 is achieved.
[0019] In the embodiment shown in fig. 2 the hood extractor 1 comprises a flow meter 18
for measuring the air flow rate through the housing 2. The flow meter 18 is installed
in the air outlet 4. The control device 13 is installed in the air inlet 3. The control
device 13 is arranged to control the air flow rate through the housing 2 based on
the air flow rate measurement. The controller 17 is configured to receive the measurement
data from the flow meter 18. The controller 17 is configured to operate the control
device 13 in response to the measurement data such that a predetermined air flow rate
through the housing 2 is achieved or the air flow rate through the housing 2 approaches
the predetermined flow rate.
[0020] In the embodiments according to figs. 1 and 2 the controller 17 is also arranged
to operate the fire damper 12 in response to the operational status of the cooking
appliance 8. When the cooking appliance 8 is switched on, the controller 17 opens
the fire damper 12 to allow air flow through the housing 2 into the exhaust duct 9.
The controller 17 opens the fire damper 12 to fully open position. Respectively, when
the cooking appliance is switched off, the controller 17 closes the fire damper 12
immediately or after a predetermined period of time, thus preventing the air flow
through the housing 2.
[0021] The hood extractor 1 according to the embodiment of fig. 1 is operated as follows.
The cooking appliance 8 below the hood extractor 1 is switched on. The controller
17 opens the fire damper 12. Air to be extracted is conducted through the housing
2 into the exhaust duct 9. The pressure sensor 15 measures the air pressure in the
housing 2 and the controller 17 receives the measurement data from the pressure sensor
15. If the hood extractor 1 is provided with the further pressure sensor 16, the further
pressure sensor 16 measures the air pressure outside the housing 2 and the controller
17 receives the measurement data from the further pressure sensor 16. The controller
17 operates the control device 13 such that the measured air pressure in the housing
2 approaches a predetermined value or reaches the predetermined value. Alternatively,
the controller 17 operates the control device 13 such that the air pressure difference
between the inside and outside of the housing 2 approaches a predetermined value or
reaches the predetermined value. The predetermined pressure value or pressure difference
value can be defined experimentally and/or by calculations so that a predetermined
air flow rate (volume flow rate) through the housing 2 is achieved.
[0022] The operation of the embodiment according to fig. 2 is similar to that of fig. 1,
except the air flow rate through the housing 2 is directly measured by the flow meter
18 installed in the air outlet 4. The controller 17 receives the measurement data
from the flow meter 18. Based on the measurement data the controller 17 operates the
control device 13 such that a predetermined flow rate through the housing 2 is achieved.
[0023] For a man skilled in the art, it is obvious that the invention is not restricted
to the above described embodiments only, but it can be modified within the scope of
the appended claims. When necessary, such features that are in the specification connected
to other features can also be applied separately.
[0024] The control device 13 can have a mechanical actuator, which actuates the control
device 13 based on the pressure difference, without the controller 17. For example,
the actuator can be a cylinder, in which a spring loaded piston is arranged. Air pressure
prevailing in the housing 2 acts on one side of the piston and air pressure prevailing
outside the housing 2 acts on the other. The piston is in force transmission connection
with the control device 13. When the piston moves in the cylinder as a result of the
varying pressure difference, the movement is transferred to the control device 13,
which in turn controls the air flow rate through the housing 2.
[0025] Instead of air inlet 3, the control device 13 can be installed in the air outlet
4 in the embodiment according to fig. 2. In this case, the flow meter 18 is installed
in the air outlet 4 downstream of the control device 13.
1. A hood extractor (1) for extracting air from a kitchen, the hood extractor (1) comprising:
- a housing (2) through which air to be extracted is arranged to flow,
- an air inlet (3) for conducting air into the housing (2),
- an air outlet (4) for removing air from the housing (2), and
- a fire damper (12) arranged in the air outlet (4),
characterized in that the hood extractor (1) comprises a control device (13) for controlling air flow rate
through the housing (2) during an operation of the hood extractor (1).
2. The hood extractor (1) according to claim 1, characterized in that the control device (13) is arranged to control air flow rate through the housing
(2) based on an air pressure in the housing (2) or an air pressure difference between
an inside and outside of the housing (2).
3. The hood extractor (1) according to claim 1 or 2, characterized in that the hood extractor (1) comprises a pressure sensor (15) for measuring air pressure
in the housing (2), and a controller (17) configured to receive measurement data from
the pressure sensor (15) and operate the control device (13) in response to the measurement
data.
4. The hood extractor (1) according to claim 3, characterized in that the hood extractor (1) comprises a further pressure sensor (16) for measuring air
pressure outside the housing (2), and the controller (17) is configured to receive
measurement data from the further pressure sensor (16) and operate the control device
(13) in response to the measurement data from the pressure sensor (15) and the further
pressure sensor (16).
5. The hood extractor (1) according to claim 3 or 4, characterized in that the controller (17) is configured to operate the control device (13) such that the
measured air pressure in the housing (2) or the air pressure difference between the
inside and outside of the housing (2) achieves or approaches a predetermined value.
6. The hood extractor according to claim 1, characterized in that the hood extractor (1) comprises a flow meter (18) for measuring the air flow rate
through the housing (2), and the control device (13) is configured to control the
air flow rate through the housing (2) based on the flow rate measurement.
7. The hood extractor according to claim 6, characterized in that the hood extractor (1) comprises a controller (17) configured to receive measurement
data from the flow meter (18) and operate the control device (13) in response to the
measurement data.
8. The hood extractor (1) according to any of the preceding claims, characterized in that the fire damper (12) is on/off controlled.
9. The hood extractor (1) according to any of the preceding claims, characterized in that the control device (13) is installed in the air outlet (4) or the air inlet (3).
10. The hood extractor (1) according to any of the preceding claims, characterized in that the control device (13) is a control damper, which is provided with an actuator (14).
11. A method of operating a hood extractor (1), by which contaminated air is extracted
from kitchen appliance(s), the hood extractor (1) comprising:
- a housing (2) through which air to be extracted is arranged to flow,
- an air inlet (3) for conducting air into the housing (2),
- an air outlet (4) for removing air from the housing (2), and
- a fire damper (12) installed in the air outlet (4), and
in which method air to be extracted is conducted through the housing (2),
characterized in that an air flow rate through the housing (2) during the operation of the hood extractor
(1) is controlled by a control device (13).
12. The method according to claim 11, characterized in that air pressure in the housing (2) and/or outside the housing (2) is measured, and the
air flow rate through the housing (2) is controlled based on the air pressure measurement.
13. The method according to claim 11, characterized in that the air flow rate through the housing (2) is measured, and the air flow rate through
the housing (2) is controlled based on the flow rate measurement.
14. The method according to claim 12, characterized in that the control device (13) is operated such that the measured air pressure in the housing
(2) or the air pressure difference between the inside and outside of the housing (2)
achieves or approaches a predetermined value.