Ventilation – Having outlet airway – With air pump
Reexamination Certificate
2004-01-29
2004-11-09
Joyce, Harold (Department: 3749)
Ventilation
Having outlet airway
With air pump
C415S208500, C415S211200, C454S345000, C454S356000
Reexamination Certificate
active
06814661
ABSTRACT:
The present invention relates to a fan designed to be associated with a duct for extracting air from at least one room, to provide air renewal in the room.
Many rooms, whether used for living accommodation or for offices, have devices providing air renewal, with the purpose of keeping the rooms in good condition, since they must be ventilated to ensure that their constituent materials retain their properties, and also for the purpose of providing comfort for the occupants.
Present-day rooms are generally provided with controlled mechanical ventilation installations, such installations comprising an extraction unit designed to extract a certain volume of air from rooms containing sanitary and cooking facilities, such as kitchens, bathrooms, toilets, etc., an equivalent volume of air to that which has been extracted being admitted into living accommodation such as lounges or bedrooms through air intakes provided in these rooms, in the window frames for example.
Another solution, implemented particularly in older buildings, consists in the provision of an air outlet in the sanitary and cooking rooms leading to a duct with a large cross section, opening at roof level, the air being extracted by natural draft when the motive pressure due to the wind and to thermal circulation is sufficient, for example when this motive pressure is greater than that generated by the combined action of a temperature difference of 10° C. between the interior and the exterior of the rooms and a wind of 3 m/s. The natural draft can provide satisfactory results in winter when the external temperature is significantly higher than the temperature inside the room. However, in the summer there may be a temperature inversion, causing air to circulate in the reverse direction, in other words with air entering through the duct normally used for extraction.
It may therefore be useful to associate this duct with a fan, to provide a supplementary motive pressure when the natural draft is insufficient, particularly in the summer, by using an axial fan having a plurality of blades extending outward from the fan shaft, these blades having an inclination which causes a displacement of air. However, a considerable amount of motive power must be provided to drive the fan, and, when the fan is stationary to permit air renewal by natural draft, the blades create a significant pressure drop which considerably limit the flow of extracted air.
The object of the invention is to provide a fan designed to be associated with an air extraction duct whose structure is such that the fan creates only negligible pressure drops when it is stationary, thus permitting air extraction by natural draft, and which, when in operation, provides an air flow comparable to that obtained with a normal natural draft corresponding, for example, to a temperature difference of 15° C. between the interior and the exterior and a wind speed of 4 m/s, while having very low electricity consumption, thus enabling it to be supplied, if required, by a solar panel placed on the roof beside the fan. The object of the invention is therefore to provide an installation which runs permanently on natural energy, in other words the motive pressure due to the wind and to thermal circulation, particularly in the winter and in the intermediate seasons, and on solar energy which supplies the fan motor in the summer.
For this purpose, the The fan as claimed in the invention comprises:
a cylindrical shell whose inlet is connected to a coaxial cylindrical duct of smaller diameter by a radial shoulder;
an electric motor mounted axially in the shell, and having a small diameter in relation to that of the shell, an impeller consisting of blades being fixed on the motor shaft, each blade being shaped in such a way that all the cross sections of one blade in planes parallel to the axis of the shell are parallel to the said axis, the maximum diameter of the blades being between the diameter of the shell and that of the inlet of the shell and decreasing in the downstream direction, in other words from the inlet end to the other end, and
air guide vanes, integral with the inner surface of the shell, distributed over the periphery of the shell and comprising in each case at least one curved part which, being located at the inlet end of the shell, is housed in the annular space between the shell and the virtual cylindrical surface which extends the air inlet.
Because of the shape of the blades of the fan impeller, these blades offer only a very low resistance to the flow of air and generate only small pressure drops when the motor is stopped. As regards the guide vanes, their curved part is located in an area outside the flow of air, since the inlet surface of the shell is smaller than the surface of the shell. However, the The fan as claimed in the invention is highly effective when the electric motor drives the impeller, since the air moved by the impeller strikes the guide vanes which channel the air from upstream to downstream. The efficiency of this fan is very high and its consumption is low, enabling the motor to be supplied with solar energy.
In one embodiment of this fan, each blade is flat and is contained in a longitudinal plane including the axis of the shell.
In a possible embodiment, each blade has an inlet edge which is perpendicular to the axis of the shell and is extended from the point of the outlet edge of the blade located farthest upstream.
The outlet edge of each blade is at a maximum distance from the axis of the shell at the level of its junction with the inlet edge, and then follows a curve which, in the downstream direction, progressively approaches the axis of said shell.
In such a case, the surface area of each blade decreases in the downstream direction.
In another possible embodiment, each blade has an inlet edge perpendicular to the axis of the shell, which extends from the point of the outlet edge of the blade located farthest upstream over a part of the radius of the shell, this edge being extended by an edge running in the downstream and inward direction, thus delimiting a blade in the general shape of a half-crescent.
Thus it is possible to have a blade whose width increases in the downstream direction.
According to another characteristic of the invention, the upstream end of each guide vane is located in the proximity of the path of the upstream parts of the outlet edges of the blades, each vane having a curved part, in other words a part not extending axially with respect to the shell, and having an angle of attack whose orientation is similar to that of the air jets emerging from the blades of the impeller, and being located outside the main flow in natural draft conditions when the fan is stationary, and extending, for example, over a length approximately equal to the diameter of the inlet of the shell, each curved part being extended in the downstream direction by a flat part parallel to the axis of the shell.
It should be noted that, in natural draft conditions, the flow of air, which at the level of the inlet occupies the cross section of the inlet, is broadened only slightly downstream, over a distance equal to the diameter of the inlet. Therefore the curved parts of the guide vanes cause practically no perturbation of the air flow. Beyond this distance, the air flow is in contact with parts of vanes which are parallel to it and which resist it only to a negligible degree. At this level, the vanes can also be wider and their inner sides can enter the virtual cylinder located in the extension of the inlet of the shell.
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patent: 1958145 (1934-05-01), Jones
patent: 2397171 (1946-03-01), Troller et al.
patent: 3329415 (1967-07-01), Cowan
patent: 5246339 (1993-09-01), Bengtsson et al.
patent: 5785495 (1998-07-01), Springer et al.
patent: 2003/0152459 (2003-08-01), Gliebe
patent: 399 698 (1965-09-01), None
patent: 2 782 781 (2000-03-01), None
patent: 1160136 (1969-07-01), None
Conseils Etudes et Recherches en Gestion de l'Air
Joyce Harold
Oliff & Berridg,e PLC
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