Gas separation: apparatus – Solid sorbent apparatus – Plural diverse separating means
Reexamination Certificate
1999-06-10
2001-03-13
Spitzer, Robert H. (Department: 1724)
Gas separation: apparatus
Solid sorbent apparatus
Plural diverse separating means
C096S153000, C096S154000, C055S385300, C055S497000, C055S516000, C055S521000, C055SDIG005
Reexamination Certificate
active
06200368
ABSTRACT:
FIELD OF THE INVENTION
An object of the present invention is to provide a filter device of the combined type, a filter device which filters out, and retain, solid particles as well as gases. Such a filter device is more particularly intended for purification of air which is then used for ventilation and/or heating and/or air conditioning of enclosed spaces, for example the interior of a motor vehicle.
The invention also relates to a method for making such a filter device.
BACKGROUND OF THE INVENTION
Filter devices of the above general kind, as currently known in the prior art, generally comprise an element, a so-called particle filter, which arrests solid particles entrained by the air passing through the filter, together with an element in the form of an odour filter which consists essentially of activated carbon.
The activated carbon is in the form of porous granules which are disposed downstream of the particle filter. The major problem which then arises in such prior art filters is the difficulty of inserting and maintaining the activated carbon granules in the filter device.
It has been proposed to utilize linking particles mixed with the activated carbon granules, so as to fix the latter on the support in which they are placed, in practice the particle filter. However, the efficiency of such an odour filter does not have an optimum value, for two reasons. In the first place the presence of linking particles proportionally reduces the quantity of activated carbon granules. In addition, the linking particles are provided for the purpose of bonding the activated carbon granules on a support; but as a result of this bonding, a major proportion of the pores in the activated carbon granules are obstructed. This reduces the capacity of the activated carbon granules to retain gases and at the same time increases the loss of pressure in the odour filter.
DISCUSSION OF THE INVENTION
An object of the present invention is to overcome the above mentioned drawbacks of the prior art.
According to the invention in a first aspect, a combined filter device for retaining particles and gases, more particularly a filter device for purification of air for the purpose of ventilating and/or heating and/or air conditioning a space, such as the interior of a motor vehicle, is characterised in that it comprises two layers of non-woven tissue between which there are disposed granules of activated carbon, the two layers of non-woven tissue interleaved at least partially so as to trap the activated carbon granules between them.
In this way, the carbon granules are held in place without any need to bond the granules to their support. In addition, the capacity of the filter for retaining noxious gases is considerably improved. Moreover, the loss of pressure caused by the filter device in the flow of air is greatly reduced.
According to a preferred feature of the invention, at least one of the layers of non-woven tissue comprises an isotropic or anisotropic card web comprising fibres of the same nature, or a mixture of different fibres. The web is preferably made as a single layer.
The length of the fibres is preferably at least 5 mm, and no more than 120 mm.
The mean diameter of the fibres is preferably at least 1 &mgr;m.
According to another preferred feature of the invention, the fibres are selected from among the following: the group consisting of thermoplastic fibres, such as fibres of polypropylene, polyethylene, polyimide, polyester, polycarbonate and/or polyamide; the group consisting of acrylic fibres, in particular preoxidised acrylic fibres; the group consisting of aramide fibres; the group consisting of phenolic fibres; the group consisting of fluorocarbon fibres; the group consisting of mineral fibres such as those of glass; and the group consisting of metallic fibres.
In preferred embodiments of the invention, the activated carbon granules have a mean size in the range between 20 and 50 mesh, and a specific surface area (surface area per unit of mass) of 500 to 2000 m
2
/g.
In preferred embodiments, the quantity of activated carbon in the filter device represents 5 to 90% of the combined mass of the first layer of non-woven tissue, the bed of activated carbon, and the second layer of non-woven tissue.
Preferably, the surface density (mass per unit of surface area) of the combination of the first layer of non-woven tissue with the activated carbon bed and the second layer of non-woven tissue is between 50 and 600 g/m
2
.
According to the invention in a second aspect, a method of making a combined filter device, adapted to retain solid particles as well as gases, is characterised by the following steps:
(a) a first layer is made from non-woven tissue;
(b) granules of activated carbon are deposited on the first layer of non-woven tissue so as to form a bed of activated carbon;
(c) a second layer of non-woven tissue is deposited on the bed of activated carbon; and
(d) the assembly comprising the first layer of non-woven tissue, the bed of activated carbon and the second layer of non-woven tissue is subjected to a mechanical consolidating operation.
The mechanical consolidating operation is preferably a hydraulic binding operation, after which the assembly is preferably subjected to a drying operation.
According to a preferred feature of the invention in its said second aspect, the assembly comprising the first layer of non-woven material, the bed of activated carbon and the second layer of non-woven material, after having been consolidated mechanically and either before or after any subsequent drying operation, undergoes a pleating operation. After step (a) and before step (b), the first layer of non-woven tissue may undergo a mechanical consolidating operation which is preferably performed by means of a hydraulic binder. In that case, in step (b), the activated carbon granules are preferably deposited on the first layer of non-woven material with the latter being damp, which facilitates, and ensures, that the carbon granules are held in place during step (d) of the method.
In some versions of the method according to the invention, at least one of the first and second said layers of non-woven material is obtained by a carding operation performed on fibres having a length in the range between 38 mm and 120 min, and having a diameter greater than 1 &mgr;m, thereby forming an isotropic card web.
Alternatively or in addition, at least one of the first and second said layers of non-woven material is obtained by a carding operation performed on fibres having a length in the range between 5 mm and 120 mm, and a diameter greater than 10 &mgr;m, thereby forming an isotropic or anisotropic card web.
The carding operation is preferably carried out using a wool-type card, which preferably includes stirring devices of the “pell-mell” type.
In versions of the method according to the invention in which the operation of mechanical consolidation is performed by hydraulic binding, and/or in which, between steps (a) and (b), the first layer is subjected to mechanical consolidation by means of hydraulic binding, this hydraulic binding operation comprises passing the web, disposed on a rotating drum, through very fine high pressure water jets. The pressure of these water jets is preferably in the range between 40 and 200 bar.
Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of preferred embodiments of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings. The description and drawings are directed, in particular, to a practical embodiment of a filter device which is designed to be incorporated in a heating or air conditioning apparatus for a motor vehicle.
REFERENCES:
patent: 2210862 (1940-08-01), Tronstad
patent: 3406501 (1968-10-01), Watkins
patent: 4081501 (1978-03-01), Muther
patent: 4181513 (1980-01-01), Fukuda et al.
patent: 4250172 (1981-02-01), Mutzenberg et al.
patent: 4906263 (1990-03-01), Von Blücher et al.
patent: 5004487 (1991-04-01), Kowalczyk
patent: 5129929
Guerin Richard
Jacq Gerard
Legrand Claude
Morgan & Finnegan , LLP
Spitzer Robert H.
Valeo
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