Abstract:
A respiratory filter includes an air-permeable sleeve and at least one filter layer that is arranged in the sleeve and contains activated carbon. The activated carbon contained in the filter layers serves as a gas filter that, by absorption, at least partially removes the noxious gases that are contained in the air inhaled.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of PCT International application Serial No. PCT/DE02/01507, filed Apr. 24, 2002 which claims the benefits of German application Serial Nos. 101 20 182.6, filed Apr. 24, 2001 and 101 52 785.3, filed Oct. 29, 2001. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a respiratory air filter. 
     2. Description of Related Art 
     In the prior art, filter devices are known that have a half mask and a filter element associated therewith. When needed, a person places the half mask over the nose and mouth such that he can only inhale air that has previously flowed through the filter element into the mask. Such filter devices are relatively complex in design and not suitable for low-cost mass production. 
     Consequently, the object of the invention is to provide a respiratory air filter that is designed as simply as possible and is inexpensive to produce. 
     SUMMARY OF THE INVENTION 
     The object of the invention is achieved with a respiratory filter, with an air-permeable sleeve; and at least one filter layer that is arranged in the sleeve and contains activated carbon. 
     This respiratory air filter is very simple and is constructed from low-cost materials such that it is particularly well suited for mass production. As it only has to be large enough to adequately cover the nose and mouth of the person, it is very compact and convenient. Because of its low price and its small dimensions, it can be taken everywhere by everyone, like paper tissues or chewing gum and is thus ready for use at any time. It can, for example, be taken along with no problem in the glove compartment of an automobile in sufficient numbers for the occupants such that, in the event of a tunnel fire, they can delay poisoning by a possibly critical period of time. 
     The activated carbon contained in the filter layers serves as a gas filter that, by absorption, at least partially removes the noxious gases that are contained in the air inhaled. 
     Additional characteristics and embodiments of the invention are described in the dependent claims. 
     Provision may be made that the sleeve be made of nonwoven fabric. Of course, other textile fabrics, such as felts, knits, woven fabrics, and knitted fabrics may also be used for the sleeve; however, compared to these, nonwoven fabrics are much less expensive to produce. 
     In this case, provision may be made that the nonwoven fabric be made of polypropylene fibers. Such polypropylene fibers can be electrostatically charged particularly simply and permanently. Since this is generally known in the prior art, further details are not given here. 
     Moreover, provision may be made that the nonwoven fabric be a spun-bonded nonwoven fabric, which may be produced, for example, by melt blowing, also referred to in the prior art as the melt blown method. 
     Additionally, provision may be made that the sleeve have a weight per unit area, also referred to as density per unit area, of 30 to 40 g/m 2 , preferably of 35 g/m 2 . 
     Provision may further be made that the sleeve be electrostatically charged. Since the sleeve is electrostatically charged, it can retain particles such as soot, dust, smoke, smog, and the like particularly well. The sleeve thus acts as a particle filter. 
     Moreover, provision may be made that at least one filter layer be made of nonwoven fabric. Here also, other textile fabrics may be used; however, nonwoven fabrics are preferred because of their low price. 
     In this case, provision may be made that each filter layer made of nonwoven fabric have a weight per unit area of 170 to 210 g/m 2 , preferably of 190 g/m 2 . 
     In addition, provision may be made that at least one filter layer have activated carbon pellets that are bonded to each other. 
     In this case, provision may be made that the activated carbon pellets are bonded to each other using an adhesive. Such a filter layer can then easily have activated carbon with a weight per unit area of 1000 to 1300 g/m 2 , preferably 1265 g/m 2  and adhesive with a weight per unit area of only 300 to 400 g/m 2 , preferably 335 g/m 2 , such that the proportion of activated carbon, at approximately 79 wt.-% in the preferred case, is clearly greater than in the conventional active carbon filter mats. 
     The adhesive may be a, preferably open-cell, polyurethane foam. However, other materials may also be used as the adhesive. 
     Moreover, provision may be made that each filter layer with activated carbon pellets bonded on each other have a weight per unit area of 250 to 2700 g/m 2 , preferably 1400 to 1800 g/m 2 , preferably 1500 to 1700 g/m 2 , and preferably 1600 g/m 2 . 
     Provision may further be made that the proportion of activated carbon be between 70 and 90 wt.-%, preferably between 75 and 85 wt.-%, preferably 80 wt.-%, and the proportion of adhesive be between 10 and 30 wt.-%, preferably between 15 and 25 wt.-%, preferably 20 wt.-%. 
     Provision may also be made that at least one filter layer have a matrix material and activated carbon bonded pellets thereto. 
     In this case, provision may be made that the matrix material be a, preferably open-cell and/or reticulated, polyurethane foam. However, other materials may also be used as the matrix material. 
     In this case, provision may further be made that the activated carbon pellets be bonded with the matrix material using an adhesive. The adhesive may be an acrylate adhesive. However, other materials may also be used as the adhesive. Such a filter layer can then easily have a weight per unit area of 1000 to 1300 g/m 2 , preferably 1265 g/m 2  and matrix material and adhesive together with a weight per unit area of only 300 to 400 g/m 2 , preferably 335 g/m 2 , such that the proportion of activated carbon, at approximately 79 wt.-% in the preferred case, is clearly greater than with the conventional activated carbon filter mats. 
     Moreover, provision may be made that each filter layer with activated carbon pellets bonded with a matrix material have a weight per unit area of 250 to 2700 g/m 2 , preferably 1400 to 1800 g/m 2 , preferably 1500 to 1700 μm 2 , and preferably 1600 g/m 2 . 
     Provision may further be made that the proportion of activated carbon be between 70 and 90 wt.-%, preferably between 75 and 85 wt.-%, preferably 80 wt.-%, and the proportion of matrix material and adhesive together be between 10 and 30 wt.-%, preferably between 15 and 25 wt.-%, preferably 20 wt.-%. 
     Moreover, provision may be made that the pellets be granules and/or crystals. The granules that are also called granular pellets are in each case asymmetric aggregates of powder particles, such as crystals or crystal fragments. 
     In addition, provision may be made that the pellets have a grain size of 0.01 to 1.0 mm, preferably 0.1 to 0.5 mm. 
     Additionally, provision may be made that the activated carbon be loaded with oxygen and/or ozone. For this purpose, the activated carbon is exposed to the corresponding gas until it has absorbed the desired amount of gas, before the respiratory air filter is packaged, preferably gas-impermeably. This may take place, for example, in that the assembled respiratory air filter is stored in a corresponding gas atmosphere. During use of the respiratory air filter, the oxygen- and/or ozone-loaded activated carbon releases this into the respiratory air flowing through the filter layer such that this is enriched with oxygen and/or ozone before it is inhaled. Thus, the respiratory air filter also serves as an oxygen source. 
     Provision may also be made that at least one filter layer have a means to filter carbon monoxide. 
     In this case, provision may further be made that the means cause an oxidation from carbon monoxide to carbon dioxide. The means may include at least one hopcalite. The hopcalite may consist, for example, of 60% MnO2 and 40% CuO or of 50% MnO2, 30% CuO, 15% cobalt oxide, and 5% Ag2O. 
     Provision may also be made that at least two filter layers be arranged on top of each other and an air-permeable separation layer lie between each two adjacent filter layers. Since the filtering capability increases with the number of filter layers, it is desirable that the respiratory air to be purified must pass through as many filter layers as possible before it is inhaled. Unfortunately, with an increasing number of filter layers, flow resistance also increases; flow resistance can be clearly reduced by the separation layers compared to a stack of filter layers in which the filter layers are stacked directly on each other. 
     In this case, provision may be made that each separation layer be made of nonwoven fabric. Here again, other textile fabrics may be used; however, nonwoven fabrics are preferred because of their lower price. 
     Provision may also be made that the nonwoven fabric be made of polyester fibers. 
     In addition, provision may be made that the nonwoven fabric be a perforated spun lace fabric, i.e., a nonwoven fabric that is mechanically reinforced, for example, by needling, intermeshing, or intermingling using water jets and has a perforation pattern. Production of such perforated spun lace fabric is known in the prior art so it will not be further described here. 
     In addition, provision may be made that each separation layer have a weight per unit area of 35 to 65 g/m 2 , preferably of 50 g/m 2 . 
     Provision may also be made that the sleeve be enclosed in a gas-impermeable package. 
     In the following, preferred exemplary embodiments are described in detail with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross section of a respiratory air filter in a first embodiment that is gas-impermeably packaged; 
         FIG. 2  is a top plan view of the respiratory air filter of  FIG. 1 , held in the palm of the hand; and 
         FIG. 3  is a cross section of a respiratory air filter in a second embodiment that is gas-impermeably packaged. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  depicts a respiratory of filter  10  in a first embodiment. It has an air-permeable sleeve  11 , four filter layers  12 , and three air-permeable separation layers  13 . 
     The sleeve  11  is made of a spun-bonded nonwoven fabric that is produced from polypropylene fibers by melt spinning. The nonwoven fabric is permanently charged electrostatically and has a weight per unit area of 30 to 40 g/m 2 , preferably 35 g/m 2 . 
     Each filter layer  12  is made of a rectangular piece of nonwoven fabric that has a width of 5 to 9 cm, preferably 7 cm, a length of 9 to 13 cm, preferably 11 cm, a thickness of 1 to 3 preferably 2 mm, and a weight per unit area of 170 to 210 g/m 2 , preferably 190 g/m 2 . The nonwoven fabric of the filter layers  12  serves, for one thing, as a particle filter  20 , and for another, as a carrier for activated carbon, which, in turn, serves as a gas filter. The production of such active carbon filter mats is known in the prior art, so it is not further described here. 
     Each separation layer  13  is made of a rectangular piece of spun lace nonwoven fabric that has substantially the same width and length as the filter layers  12 , a thickness of 0.5 to 1.5 mm, preferably 1.0 mm and a weight per unit area of 35 to 65 g/m 2 , preferably 50 g/m 2 . The nonwoven fabric is made of polyester fibers and has a perforation pattern. 
     The four filter layers  12  and the three separation layers  13  are arranged alternatingly on top of each other such that they form a right parallelepiped-shaped stack in which a separation layer  13  lies between each two adjacent filter layers  12 . This stack is surrounded by the sleeve  11 , which is, in turn, gas-impermeably enclosed in a packaging film  14 . 
     When needed, the person tears open the packaging film and removes the respiratory air filter  10  therefrom. He places it in his hand, as depicted in  FIG. 2 , and presses it together on the transverse sides between the fingers and the ball of the thumb so that the side away from the hand is arched slightly concave. The person then holds the respiratory air filter  10  with this concave side on his face such that it simultaneously covers the mouth and nose. Then, when the person inhales, the air flows between the fingers to the respiratory air filter  10  and through it on into the mouth and/or nose. 
       FIG. 3  depicts a respiratory air filter  10  in a second embodiment. This second embodiment is distinguished from the first embodiment of  FIG. 1  in that, in the sleeve  11 , instead of the four filter layers  12  and the three separation layers  13 , only one filter layer  12 ′ is provided and in that this filter layer  12 ′ consists, in a first alternative, of activated carbon pellets that are bonded to each other using polyurethane foam. 
     In a second alternative, the filter layer  12 ′ may be made from a matrix material, which may, for example, be open-cell polyurethane foam, and from activated carbon pellets that are bonded to the matrix material using an acrylate adhesive. 
     The respiratory air filter  10  according to this invention is low cost, compact, and easy to use. Consequently, it can be taken along with no problem by everyone everywhere at all times like a pack of paper tissues and also, for example, be kept handy in the glove compartment of automobiles or in the night stand of hotel rooms. 
     It will be apparent from the foregoing that while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.