Abstract:
The invention relates to a textile surface for at least partially absorbing electromagnetic waves. The textile surface comprises textile elements, such as threads or fibers, of at least first and second types. The textile elements of the first and second types have electrical-conduction properties. Each textile element of the first type comprises a synthetic-material core coated with a first metal. The textile elements of the second type are made of a second metal. The invention also relates to a textile material comprising at least two textile surfaces, and to a protective device comprising a textile surface or a textile material.

Description:
TECHNICAL FIELD 
     The present invention relates to a textile surface and a textile material for at least partially absorbing electromagnetic waves, as well as a protective device against electromagnetic waves including a protection area having a textile surface or a textile material. 
     BACKGROUND 
     With the rapid growth of wireless communication means, such as mobile telephones or wireless Internet connections, there is growing concern about electromagnetic waves and the related health risks. 
     In fact, the electromagnetic waves emitted for wireless communication, and more particularly for mobile telephones, are in the microwave frequency range. This frequency range is in particular known for its interaction with the water molecule, which makes up 70% of the human body. It is therefore possible, as certain scientific studies have tended to indicate, that these waves may have a direct influence on health. 
     To protect against these risks, it is known to use textile surfaces, like those described in document U.S. Pat. No. 6,855,883, making it possible to absorb part of the electromagnetic waves and therefore, when they equip a protective device, to limit exposure to such waves. 
     Such textile surfaces are generally obtained by weaving metal conductive threads together. The absorption properties of these surfaces are directly related to the conductivity of the metal making up the threads and the density of the weave. As a result, a textile surface with good absorption properties of the electromagnetic waves requires the use of a metal with a high conductivity, such as gold, silver or copper, with a high weave density. 
     Such textile surfaces are relatively expensive, which limits their wide-scale use. 
     BRIEF SUMMARY 
     The invention aims to resolve this drawback. 
     One aim of the invention is therefore to provide a textile surface having electromagnetic wave absorption qualities similar to those of a textile surface made entirely from a metal with a low conductivity while having a much lower production cost. 
     To that end, the invention relates to a textile surface for at least partially absorbing electromagnetic waves, including textile elements, such as threads or fibers, of at least first and second types, the textile elements of the first and second types having electrical conduction properties, each textile element of the first type including a synthetic-material core covered with a first metal, the textile elements of the second type being made from a second metal. 
     Such a textile surface makes it possible, by using textile elements of a first type having a synthetic-material core covered with a metal with high conductivity, with textile elements of a second type made from a less expensive metal, to obtain an absorption quality similar to that of a textile surface made entirely from textile elements with a high-conductivity metal while having much lower production costs. In fact, the high-conductivity metal being able to be used as a coating on a synthetic-material core, it does not significantly increase the cost of the textile surface, while offering, due to its cooperation with the metal making up the textile elements of the second type, good electromagnetic wave absorption quality. 
     Advantageously, the first metal is silver. 
     Silver is a noble metal having high conductivity that therefore allows the textile surface to have a good electromagnetic wave absorption quality. 
     Preferably, the core of the textile elements of the first type is made from a polymer of the polyamide type. 
     Such material makes it possible to provide a core for the textile elements of the first type that is robust and inexpensive. 
     Preferably, the second metal is steel or a steel alloy. 
     The steel makes it possible to provide textile elements of the second type that have both good conductivity and a lower cost. 
     Advantageously, the textile surface also includes textile elements of a third type, made from electrically insulating material, such as polyester. 
     Such a third type of textile elements makes it possible to facilitate production of the textile surface, these textile elements making it possible, when they are combined with metallic textile elements, to provide threads having the necessary flexibility for weaving or knitting. 
     Advantageously, the textile surface includes covered strands or threads respectively obtained by twisting or covering at least one textile elements of the third type with at least one textile element of the first type or the second type. 
     The formation of covered strands or threads from textile elements of the third type with elements of the first or second types makes it possible to provide threads or fibers having the necessary flexibility for weaving or knitting. 
     Advantageously, the textile surface is obtained by weaving. 
     Weaving makes it possible to obtain a textile surface having, for a given thickness, a maximum density of conductive textile elements. 
     Preferably, the textile surface has weft threads including textile elements of the first or second type, the textile surface having warp threads including textile elements of a different type, from among the textile elements of the first and second types. 
     Advantageously, the textile surface is formed from polyamide threads covered with silver for the weft or warp threads and stainless steel/polyester threads for the warp or weft threads, respectively. 
     The invention also relates to a textile material for at least partially absorbing electromagnetic waves including at least two layers each made up of a textile surface according to the invention. 
     Such a textile material makes it possible to obtain high-quality absorption of electrostatic waves, since it combines the absorption of at least two layers of textile surfaces. 
     The invention also relates to a protective device against electromagnetic waves designed to house a mobile telephone, the device including:
         a housing designed to receive the mobile telephone, and   at least one protective area designed to be inserted between the head of a user and the mobile telephone, the protective area including a textile surface according to the invention or a textile material according to the invention.       

     Such a device allows the user to protect himself from the electromagnetic waves emitted by the mobile telephone during a telephone call. 
     Advantageously, the device includes a flap which, including the protective area, can be moved between an open position, in which the flap is designed to be positioned retracted from the mobile telephone received in the housing, and a closed position, in which the flap is designed to be positioned near the mobile telephone. 
     More specifically, when the flap in the closed position is positioned against the front face of the mobile telephone. Such a flap makes it possible to provide access to the mobile telephone during handling thereof offering good protection against the electromagnetic waves emitted by the mobile telephone during a telephone call. 
     In one preferred embodiment, the flap is made by stacking at least:
         a first layer forming said protective area, made in a textile surface or textile material as presented above; and   a second layer forming an outer facing, the second layer comprising at least one first orifice arranged such that when the flap is in the closed position, each first orifice is positioned centered across from a microphone of the mobile telephone.       

     Such an arrangement is advantageous insofar as it makes it possible to provide an aesthetic device in which the attenuation of the acoustic waves picked up by the microphones of the mobile telephone is minimized, when the flap is in the closed position. 
     Preferably, the second layer forming the outer facing comprises at least one second orifice arranged such that when the flap is in the closed position, each second orifice is positioned centered across from a speaker of the mobile telephone. 
     Such an arrangement is advantageous in that it makes it possible to provide an aesthetic device in which the attenuation of the acoustic waves generated by the speaker of the mobile telephone is minimized, when the flap is in the closed position. 
     For example, the second layer is made from leather or plastic. 
     According to one feature, the stack also comprises a third layer forming an inner facing, this third layer comprising at least one first orifice, and preferably at least one second orifice, arranged such that when the flap is in the closed position, each first orifice is positioned centered across from a microphone of the mobile telephone, and each second orifice is positioned centered across from a speaker of the mobile telephone. 
     For example, the third layer is made from suede cloth. 
     According to another feature, the stack also comprises a fourth, reinforcing layer, positioned between the second and third layers, this fourth layer comprising at least one first orifice, and preferably at least one second orifice, arranged such that when the flap is in the closed position, each first orifice is positioned centered across from a microphone of the mobile telephone, and each second orifice is positioned centered across from the speaker of the mobile telephone. 
     For example, the fourth layer is made from Plexiglas. 
     According to another feature, the stack comprises a fifth layer made from cardboard, this fifth layer comprising at least one first orifice, and preferably at least one second orifice, arranged such that when the flap is in the closed position, each first orifice is positioned centered across from a microphone of the mobile telephone, and each second orifice is positioned centered across from a speaker of the mobile telephone. 
     Advantageously, the housing is provided with at least one first orifice arranged to be positioned centered across from a microphone of the mobile telephone, and preferably at least one second orifice arranged to be positioned centered across from a speaker of the mobile telephone, when said mobile telephone is received in the housing. 
     Such an arrangement is advantageous insofar as it makes it possible to provide a housing perfectly gripping the mobile telephone, without attenuating the acoustic waves generated by the speaker of the mobile telephone or the acoustic waves picked up by the microphones, when the flap is in the closed position. 
     The invention lastly relates to an assembly characterized in that it comprises a mobile telephone and a device as presented above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In any case, the invention will be well understood using the following description provided in reference to the appended diagrammatic drawing, showing, as non-limiting examples, three embodiments of this textile surface and this textile material as well as two embodiments of this protective device against electromagnetic waves. 
         FIG. 1  is a diagrammatic perspective view of a first embodiment of a protective device against electromagnetic waves for a mobile telephone; 
         FIG. 2  is a diagrammatic perspective view with no mobile telephone, the trim of the part comprising the textile surface having been removed; 
         FIG. 3  is a transverse cross-sectional view of the flap; 
         FIG. 4  is a perspective view of a second embodiment of the protective device against electromagnetic waves with no mobile telephone, the trim of the part comprising the textile surface having been removed; 
         FIG. 5  is a perspective view of a third embodiment of the protective device against electromagnetic waves; 
         FIG. 6  is a first top view of the protective device of  FIG. 5 ; 
         FIG. 7  a second top view of the protective device of  FIG. 5 ; 
         FIG. 8  is a perspective view of the flap of the protective device of  FIG. 5 . 
     
    
    
     For the different embodiments, the same references will be used for identical elements or elements performing the same function, so as to simplify the description. 
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a first embodiment of a protective device  1  against electromagnetic waves assuming the form of a case housing a mobile telephone  2 . 
     The protective device  1  has a first part  3  serving to house the mobile telephone  2  and a second part assuming the form of a flap  5  or cover. 
     The first part  3  comprises a support surface  6 , with dimensions similar to those of the surface of the mobile telephone  2  to be housed, having means for maintaining the telephone on the support surface  6 . In  FIG. 1 , the maintaining means assume the form of a cradle  7  gripping the lower portion  8  of the mobile telephone  2 , but these means may assume other forms, such as elastic bands present on the lower and upper portion of the support surface  6 . 
     The support surface  6  and the maintaining means are made from a material that is transparent to the electromagnetic waves in the frequency range that is used in the mobile telephone. 
     The flap  5  of the protective device  1  is attached on the first part  3  using a strip  9  of a material similar to the support surface  6 . In this way, the flap  5  can be moved between an open position, in which it provides access to the controls of the mobile telephone  2 , and a closed position, in which it covers the front face  10  of the mobile telephone  2 , such that it is inserted between the head of a user and the mobile telephone  2  during a telephone call. 
     The flap  5  has dimensions similar to those of the surface of the mobile telephone  2 . 
     The flap  5 , as illustrated in  FIGS. 2 and 3 , includes a textile layer encapsulated between two trim surfaces  11 , such as leather, textile or synthetic material surfaces. Out of a concern for aesthetic cohesion, the trim surfaces  11  may be of the same type as the support surface  6 . 
     The textile layer may be a textile surface (not shown), or a textile material  12  including at least two textile surfaces, suitable for adsorbing electromagnetic waves. The textile layer forms a protective area  13  against the electromagnetic waves. 
     According to a first embodiment of the textile surface, the textile surface is a fabric including weft threads  14  and warp threads  15 . 
     The warp threads  15  are formed by a core (not shown), made from a polymer of the polyamide type, and covered with silver. 
     The weft threads  14  are made of strands (not shown) made by twisting a steel thread (not shown) with a polyester thread (not shown). 
     According to this embodiment, with a composition of 54% silver-covered polyamide threads, 23% stainless steel threads and 23% polyester threads, a textile material  11  including two juxtaposed textile surfaces has electromagnetic wave attenuations measured using the GAM-T20:1992 method of:
         47.4 dB for a frequency of 900 MHz,   50.4 dB for a frequency of 1800 MHz, and   54.8 dB for a frequency of 2100 MHz.       

     According to another embodiment of the textile surface, the textile surface differs from the previous embodiment in that the warp threads  15  are strands made by twisting a steel thread with a polyester thread and in that the weft threads  14  are formed by a core, made from a polymer of the polyamide type, and covered with silver. 
     According to this embodiment, with a composition of 32% silver-covered polyamide threads, 33% stainless steel threads and 35% polyester threads, a textile material  11  including two juxtaposed textile surfaces has electromagnetic wave attenuations measured using the GAM-T20:1992 method of:
         47.8 dB for a frequency of 900 MHz,   51.4 dB for a frequency of 1800 MHz, and   55.4 dB for a frequency of 2100 MHz.       

     According to another embodiment of the textile surface, the textile surface differs from the previous embodiments in that the warp threads  15  are formed by a core, made from a polymer of the polyamide type, and covered with silver, and in that the weft threads  14  are formed by 60% strands made by twisting a steel thread with a polyester thread and 40% threads formed by a core, made from a polymer of the polyamide type, and covered with silver. 
     According to this embodiment with a composition of 75% silver-covered polyamide threads, 14% stainless steel threads and 14% polyester threads, a textile material  12  including two juxtaposed textile surfaces has electromagnetic wave attenuations measured using the GAM-T20:1992 method of:
         48 dB for a frequency of 900 MHz,   51 dB for a frequency of 1800 MHz, and   55 dB for a frequency of 2100 MHz.       

     The textile surface may also be a textile surface formed using a production method other than weaving, such as knitting or forming a nonwoven surface. 
     During the use of the protective device  1 , the mobile telephone  2  is positioned in the maintaining means. Thus, the user can access the controls of the mobile telephone  2  by positioning the flap  5  retracted from the mobile telephone  2  and is also protected from electromagnetic waves emitted by the mobile telephone  2  when the flap  5  bears on the front face  10  of the mobile telephone  5 . 
       FIG. 4  illustrates a second embodiment of the protective device  1 . Such a protective device  1  differs from a protective device  1  according to the first embodiment in that it has lateral walls  16  on the edges of the flap  5 , said lateral walls having a textile layer to perfect the protection against electromagnetic waves during a telephone call. 
     This protective device  1  makes it possible both to ensure optimal protection for the user, the front face  10  of the mobile telephone  2  being encapsulated by the flap  5  and the lateral walls  16 , and allowing, via the support surface  6 , wireless communication with the closest GSM terminal. 
     The textile surfaces, and the textile materials  12  including such textile surfaces, can also be used for applications other than the protective devices  1  described above. They may be used for other protective systems against electromagnetic waves, such as clothing for pregnant women, individuals who are sensitive to electromagnetic waves, or individuals with a pacemaker. 
     The textile surfaces, and the textile materials including such textile surfaces, can also be used for applications requiring insulation against electromagnetic waves, such as shielding electronic devices, whether medical or others, or insulating a location relative to wireless communication networks. 
       FIGS. 5 to 8  illustrate a third embodiment of the protective device  1 . 
     This third embodiment is identical to the first embodiment, with the exception that the cradle  7  extends over the entire perimeter of the support surface  6 . 
     The cradle  7  is configured to allow access to a power port  31  (illustrated in  FIG. 5 ) to recharge the battery of the mobile telephone  2 . 
     The cradle  7  has orifices  32  arranged to be positioned centered across from the microphones of the mobile telephone  2 , when the latter is received in the cradle  7 . 
     The cradle  7  has an orifice  33  arranged to be positioned centered across from the speaker of the mobile telephone  2 , when the latter is received in the cradle  7 . 
     The flap  5  is made by successively stacking (illustrated in  FIG. 8 ):
         a layer  35  forming an outer facing, for example made from leather or plastic;   a reinforcing layer  36 , for example made from Plexiglas;   a layer  37  forming a protective area, made from a textile surface, or a textile material  12  including at least two textile surfaces as presented above;   a layer  38 , for example made from cardboard; and   a layer  39  forming an inner facing, for example made from suede cloth.       

     The layers  35 ,  36 ,  38  and  39  each comprise two orifices  40  arranged such that when the flap  5  is in the closed position, the orifices  40  are positioned centered across from the microphones of the mobile telephone. 
     The orifices  40  make it possible to limit the attenuation of the acoustic waves picked up by the microphone of the mobile telephone, when the flap  5  is in the closed position. 
     Furthermore, the layers  35 ,  36 ,  38  and  39  each comprise an orifice  41  arranged such that when the flap  5  is in the closed position, each orifice  41  is positioned centered across from the speaker of the mobile telephone. 
     The orifices  41  make it possible to limit the attenuation of the acoustic waves generated by the speaker of the mobile telephone, when the flap  5  is in the closed position. 
     The layer  37  has no orifices  40  and  41 , so as to prohibit the passage of the electromagnetic waves through the cover and protect the user during usage conditions. 
     The invention is of course not limited solely to the embodiments of these textile surfaces and textile materials to absorb the electromagnetic waves and protective devices described above as examples; on the contrary, it encompasses all alternative embodiments. The metals used may in particular be metals other than silver and steel.