Abstract:
A filter pad, particularly for a protective hood or smoke mask, has a flow distributor and an adjacent underlying filter layer. The flow distributor, which is impermeable or substantially impermeable to gas, diverts gas flow and directs flow in the underlying filter layer thus increasing or maximizing resident time for filtering in the filter layer. The filter pad may include one or more flow distributors and one or more filter layers. The filter pad may be incorporated into a protective hood that is provided for the protection of individuals in the event of fire or other disaster. The hood includes a transparent, low flammability cover having an opening therein with the filter pad exposed through the opening, the hood being disposed over and completely around the head of a wearer with a bottom thereof extending to a neck of the wearer.

Description:
TECHNICAL FIELD 
   The present invention relates to protective breathing devices, in general, and to filter pads and protective hoods, in particular. 
   BACKGROUND OF THE INVENTION 
   It is of the utmost importance that during a disastrous situation, such as a fire or toxic chemical leak, that a person caught in the disaster will have access to a protective breathing device that will provide adequate protection from smoke, gases, fumes, or other contaminants for an amount of time necessary to escape the disaster. 
   Smoke protective hoods have been provided for the protection of wearers from dangerous conditions such as smoke inhalation. For example, U.S. Pat. No. 4,411,023 to Pinson describes a hood for protecting the wearer from poisonous fumes and the like including a respirator having a portion arranged to be gripped in the mouth of the user. 
   U.S. Pat. No. 5,146,636 to De La Pena describes a heat and smoke protective hood that comprises a bag-like head covering having a filter and a skirt extending about the covering. 
   U.S. Pat. No. 4,589,408 to Singer describes a head covering having a face mask portion and a rear portion which surrounds the head of the wearer for exclusion of bacteria while retaining air permeability. 
   Though previous protective breathing devices may provide protection from the material against which protection is required, it is important that any filter pad or other filtering mechanism within the protective devices work efficiently in filtering contaminants. Further, it is important that protective devices can be efficiently stored and readily accessed by the user in his time of need. 
   Therefore, it is an object of the present invention to provide a new and improved filter pad. 
   It is an object of the present invention to provide a filter pad that provides a wearer with breathable air. 
   It is another object of the present invention to provide a new and improved protective hood. 
   It is an object of the present invention to provide a protective hood that is efficiently stored. 
   It is an object of the present invention to provide a protective hood that is readily accessed. 
   It is an object of the present invention to provide a protective hood that provides breathable air to a wearer when contaminants are present in the local environment. 
   SUMMARY OF THE INVENTION 
   Objects of the present invention have been met by a filter pad, particularly for use with a protective hood, which includes at least one flow distributor that directs gas flow, such as gas flow from smoke or other gases or noxious gases, through a flow path parallel to at least one adjacent filter layer to maximize, or at least increase, contact time between the gas and the filter material. The flow distributor is comprised of a material, such as a non-woven material, that is substantially impermeable or completely impermeable to gas. Where a material is described as completely impermeable, it can also be described as substantially impermeable. The adjacent filter element is comprised of a material, such as a woven material which may be impregnated with chemicals that remove hazardous components from the gas. The flow distributor covers a portion of the adjacent filter element of the filter pad and, due to its impermeability, diverts gas flow to the adjacent filter element portion that is uncovered by the flow distributor. This movement allows for efficient use of most or all of the filter element area. The flow distributor is advantageous in that it efficiently directs flow within a filter element of the filter pad and provides more residence time for adsorption or other types of filtering and increased filter efficiency. 
   One or more additional arrangements of one or more flow distributors, adjacent filter elements, and additional filter elements may be used in the filter pad. Once the gas has passed through the filter pad, contaminants have been removed and breathable air reaches the wearer. One or more flow distributors may be placed in different covering positions relative to each adjacent filter element to direct flow in the adjacent filter element as desired. In one embodiment of the present invention, a flow diverter is comprised of a series of flow distributors with alternating flow openings. Filter elements are located between and/or adjacent to the flow distributors. When the contaminant flow is drawn into a space between a flow distributor and an adjacent filter element, it is directed parallel to a surface of the filter pad. The result is a serpentine flow pattern that maximizes, or at least increases, the contact time between the gas and filter elements. In addition to protection against inhalation of toxic gas, the filter pad may be used to protect against a variety of contaminants, such as particulates or liquid aerosols and droplets. 
   The filter pad described above, as well other types of filter pads, may be utilized within a protective hood including a transparent, low-flammability cover having an opening therein with a filter pad exposed through the opening. The hood is disposed over and completely around the head of a wearer with a bottom thereof extending to a neck of the wearer. The hood may comprise various colors through which the user may see. 
   In one embodiment of the present invention, the protective hood of the present invention includes a filter pad that is creased along a length and along a width of the filter pad and includes a foldable covering. The creased portions facilitate folding of the filter pad, which depending on how many layers of filter are present, may be relatively thick. The entire protective hood is capable of being folded into a relatively small form which provides for easy storage and access. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a protective hood of the present invention including a front view of a filter pad of the present invention. 
       FIG. 2  is a rear view of the protective hood of  FIG. 1  without a wearer. 
       FIG. 3  is an exploded view of the filter pad of  FIG. 2 . 
       FIG. 4   a  is a perspective view of the protective hood of  FIG. 1  folded once. 
       FIG. 4   b  is a perspective view of the protective hood of  FIG. 4   a  folded. 
       FIG. 4   c  is a perspective view of the protective hood of  FIG. 4   b  folded. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to  FIGS. 1 and 2 , there is seen a protective hood  10  of the present invention featuring a filter pad  12 . The protective hood comprises a transparent, low flammability cover  14  having an opening (not shown) therein which is covered by the filter pad  12  and an opening  16  within which a user  18  inserts his head such that the cover is disposed over and completely around the head of a wearer with a bottom thereof extending to a neck of the wearer. The cover extends continuously in a single sheet to the neck of the user on either side. Adhesive tape  20  attaches the filter pad  12  to the bag to cover the opening and it is applied so that an outer surface  22  of the filter pad  12  remains exposed. The cover may comprise, for example, a soft nylon material or KAPTON. The cover is transparent so that a user may see through it. The cover may comprise colors through which the user may see. The protective hood includes a draw string  21  threaded through openings  23  around the hood at the neck area of the wearer so that the bottom of the hood may be effectively closed by drawing the hood close around the neck area of the wearer without preventing the exhaling of air by the wearer and enabling the venting of exhaled air to atmosphere through the bottom of the hood. Drawstring  21  encircles a lower portion of cover  14 . A filter pad, other than filter pad  12 , may be utilized in the protective hood, if desired. 
   In the depicted example, the protective hood cover  14  is rectangular in shape and is approximately 52 cm in length and 46 cm in width. In one example, the filter pad is approximately 30 cm in length, 9.5 cm in width, and has a thickness of approximately 6 mm. 
   With reference to  FIG. 3 , layers of the filter pad  12  are seen. Each of the various layers is disposed adjacent to the next layer and is, for example, planar or substantially planar. The layers may be attached to one another by stitching  24  ( FIG. 2 ) or a perimeter adhesive. Layer  22  of the filter pad  12  is a filter element which filters out, for example, large particulates such as soot, ash, and aerosols. In one example, layer  22  comprises a woven material, such as a cotton cloth. Layer  22  is directly exposed to the environment outside of the covering. Layer  22  is, for example, approximately 1 mm in thickness. 
   Layer  24 , adjacent to and between layers  22  and  26 , is another filter element which comprises for example, one or more woven materials. The woven materials may be chemically impregnated or not. The woven material is, for example, more closely woven than layer  22  so as to be capable of filtering smaller particulates of for example, dust, soot, ash, and aerosols. Layer  24  is approximately 0.5 mm in thickness. 
   Layer  26  is a flow distributor which is substantially impermeable to the gas being filtered and which is adjacent to and between layers  24  and  28 . It is comprised of, for example, a non-woven material such as a special non-porous paper which at least substantially, and preferably completely, blocks gas flow in addition to blocking passage of other undesirable materials such as blood, an aerosol-like particulate. Layer  26  is, for example, then and less than 0.1 mm in thickness. 
   Layer  28  is a filter element which filters, for example, noxious gases and aerosols and which is adjacent to and between layers  26  and  30 . It is comprised of, for example, a carbon impregnated material, such as carbon impregnated polyester. Filter element  28  and/or other woven filter elements may include multiple layers or multiple layers of chemically impregnated woven material. The material of layer  28  is, for example, woven. Layer  28  may be a low density woven material. In one example, layer  28  is a close netted woven cloth material. The carbon particles are, in one example, fine granulated particles that provide a large surface area to projected area ratio, such as a ratio of approximately 100 to 1 actual surface area to projected (cross-sectional) area. The carbon particles provide maximum area for a high rate of absorption. Layer  28  is approximately 1.5 mm in thickness. In one embodiment, one or more filter elements is impregnated with metal oxides to convert CO to CO 2  and thus reduce the amount of CO in the breathable air. In one example, CuO—MnO 2  or copper zinc oxides are used for filter element impregnation to convert CO to CO 2  and thus reduce the amount of CO in the breathable air. 
   Layer  30  includes flow distributors  30   a  and  30   b  which are substantially impermeable to the gas being filtered and which are adjacent to and between layers  28  and  32 . Each flow distributor  30   a  and  30   b  is comprised of, for example, a non-woven material such as a special non-porous paper which substantially blocks gas flow in addition to blocking passage of other undesirable materials such as blood. Each flow distributor  30   a  and  30   b  is less than 0.1 mm in thickness. 
   Layer  32  is a filter element which is adjacent to and between flow distributors  30   a ,  30   b , and layer  34  and which filters, for example, noxious gases and aerosols. It is comprised of, for example, a carbon impregnated material, such as the material described above with regard to layer  28 . The material of layer  32  is, for example, woven. Layer  32  is, for example approximately 1.5 mm in thickness. 
   Layer  34  is a filter element which is adjacent to and between layers  32  and  36  and which filters for example, moisture, aerosols, inhaled air and/or gases, and exhaled air and/or gases. It is comprised of, for example, a molecular sieve which may include, for example, zeolite. The material of layer  34  is, for example, woven. Layer  34  is, for example, approximately 1 mm in thickness. 
   Layer  36  is a filter element which is disposed adjacent to layer  34  and which is in, or is capable of, contact with the wearer of the protective hood or other mechanism incorporating the filter pad  12 . In one example, layer  36  is a woven material such as a cloth. It is preferable that the cloth comprise a soft material as it will likely be in contact with the wearer&#39;s face. Layer  36  is, for example, approximately 0.2 mm in thickness. 
   The filter pad  12  is provided with a mechanism which allows the filter pad to be located relative to the user in a position to filter out undesired matter, such as soot, ash, dust aerosols, other particulates and certain gases, so that the user is provided with breathable air. Typically, the filter pad is disposed in front of the user&#39;s nose and mouth. In one example, the filter pad  12  may comprise a part of the protective hood  10  and the protective hood assists in positioning the filter pad relative to the user. Alternatively, the filter pad  12  may comprise a part of another device which can be used to position and/or secure the filter pad relative to the wearer. For instance the filter pad  12  may be attached to the wearer&#39;s face by tie strings (not shown), and goggles (not shown) may be utilized to protect the wearer&#39;s eyes from harmful matter, such as noxious gases. 
   The operation of the filter pad  12  will be described below in conjunction with the protective hood  10 , though other mechanisms for positioning the filter relative to the user may be used. A user places the protective hood  10  over his head and tightens the drawstring  21  so that the bottom of the hood may be effectively closed by drawing the hood close around the neck area of the wearer  18  without preventing the exhaling of air by the wearer and enabling the venting of exhaled air to atmosphere through the bottom of the hood  10 . The closure around the neck is adequate to restrict air flow around the neck so air is preferentially inhaled through the filter. 
   As the wearer inhales, matter, such as air, that is present in the local environment is drawn through the filter pad  12  in the direction indicated by the arrows of  FIG. 3 . One or more types of matter are typically filtered at each layer of the filter pad  12 , as described above. 
   During use of the filter pad  12 , inhaled matter such as gas, is drawn in the direction of arrows a 1 , a 2  and a 3  and certain matter, as described above with regard to layer  22 , is filtered at layer  22 . Matter that was not filtered out at filter  22  is drawn in the direction of arrows b 1 , b 2 , and b 3 . 
   Matter, including for example gas, that is not filtered out at filter  24  is drawn to filter  28 , as indicated by arrows c 1  and c 2 . Layer  26  is in a covering relation with less than an entire major surface  36  of layer  28 . In the example of filter pad  12 , layer  26  is disposed on a center portion of major surface  36 . Because layer  26  is substantially or completely impermeable to one or more gases to be filtered, gas will be substantially prevented from flowing to filter  28  through flow distributor  26  as indicated by the lack of arrows directly above layer  26 . Gas flow will continue along either side of the flow distributor  26  at openings as indicated by the arrows c 1  and c 2  to the filter  28 . Therefore, most of the flow will initially contact filter  28  at portions of major surface  36  not covered by flow distributor  26 , or at portions other than the center portion which, as stated above, is covered by the flow distributor  26 . Typically, gas first flows to filter  28  at side portions uncovered by the flow distributor, as indicated by the arrows c 1  and c 2 ′ located at the sides of the distributor  26 . Gas flow is diverted by the flow distributor and is directed as indicated by arrows d 1  and d 2  parallel to, and across and/or through filter element  28 , providing more residence time for adsorption and increased filter efficiency. The contact/exposure time between the gas and filter element  28  is maximized or at least increased. 
   Matter, including for example gas, that is not filtered out of filter  28  is drawn to filter  32 , as indicated by arrows e 1  and e 2 . Flow distributors  30   a  and  30   b  are each in a covering relation with less than an entire major surface  38  of layer  32 . In this example, the two flow distributors are disposed on side portions of major surface  38 . Because flow distributors  30   a  and  30   b  are substantially or completely impermeable to one or more gases to be filtered, gas will be substantially prevented from flowing to filter  32  through flow distributors  30   a  and  30   b , as indicated by the lack of arrows directly beneath flow distributors  30   a  and  30   b . Thus, the gas flow will continue in between flow distributors  30   a  and  30   b  at an opening as indicated by arrows e 1  and e 2 . Therefore, most of the flow will initially contact filter  32  at a portion of major surface  38  not covered by flow distributors  30   a  and  30   b , or at a portion other than the side portions which, as stated above, are covered by the flow distributors  30   a  and  30   b . Typically, gas first flows to filter  32  at a center portion uncovered by the flow distributors  30   a  and  30   b , as indicated by the arrows e 1  and e 2  located at the side of the flow distributors. Gas flow is diverted by the flow distributors and is directed, as indicated by the arrows f 1  and f 2 , parallel to, and across and/or through filter element  32 , providing more residence time for adsorption and increased filter efficiency. The contact/exposure time between the gas and filter element  32  is maximized or at least increased. 
   Matter that is not filtered out at filter  32  is drawn to filter  34 , as indicated by arrows g 1 , g 2 , and g 3 . Matter that is not filtered out at filter  34  is drawn to filter  36 , as indicated by arrows h 1 , h 2 , and h 3 . Although filter  36  may provide some filtering functions, by the time the matter reaches filter,  36  it is typically breathable air for the wearer. 
   Each flow distributor may cause a pressure differential at the adjacent filter layer of the filter pad  12  which causes movement of gas in a particular direction. A pressure differential may form when the flow distributor directs gas flow away from the flow distributor and to particular portions of the adjacent filter. The invention is advantageous in at least that matter, such as gas containing contaminants, is exposed to a filter element for an increased or even a maximum amount of time as a result of the diverting action of the flow distributor. Therefore, the filter pad is highly efficient in providing breathable air to the wearer. 
   The position, number, and size of flow distributors may vary as desired. The position, number, and size of the flow distributors may cause the gas or other matter to be directed in various directions across and through filters. 
   Any desired filter pad size may be used. In one embodiment, one or more filter pads are used. In another embodiment, the filter pad may extend around an entire hood surface. Various arrangements of the flow distributor(s) may be used to selectively direct gas or other matter flow through the filter pad in various desired directions. 
   With reference to  FIGS. 1 and 2 , filter pad is creased along its length and width at creases  40  and  42 , respectively. The creases form segments  46 ,  48 ,  50 , and  52 . In the depicted example, the filter pad is creased along its entire central length and along its entire central width. The creases may be formed by folding or by stitching the layers of the filter pad  12  together so that stitches  44  form creases  40  and  42 . Adhesive  20  is also creased by folding. 
   In  FIG. 4   a , filter pad  12  is folded in half along crease  40  and cover  14 . In  FIG. 4   b , filter pad  12  is again folded in half along crease  42  and cover  14 . In  FIG. 4   c , cover  14  is folded in areas outside of pad  12 . By folding the protective hood  10  along the creases of the filter pad  12  and at various locations along the cover  14 , the protective hood is substantially decreased in size. Therefore, it can be easily stored and packaged for convenient access. Creases may be formed along various positions of the filter pad  12  and cover  14 .