Patent Publication Number: US-2023157388-A1

Title: A face protection mask, a method for producing face protection masks and an apparatus for producing face protection masks

Description:
FIELD OF THE INVENTION 
     The present invention relates to a face protection mask and a method and an apparatus for producing face protection masks. 
     The invention has been developed with particular regard to producing disposable surgical masks, however, the invention can also be used for producing face protection masks of other types, such as masks having a mask body to which at least one elastic element is fixed for its use. 
     DESCRIPTION OF THE PRIOR ART 
     A widely used type of disposable surgical mask comprises a mask body, typically formed of a multilayer rectangular panel of non-woven fabric with a series of parallel folds, and two C-shaped elastic threads attached to opposite sides of the mask body, which form two loops for the ears that are placed around the users ears to hold the mask body in position in front of the users mouth and nose. Further known embodiments envisage the mask body being connected to elastic bands which—in use—are arranged around the back of the head and/or around the back of the neck. 
     Most of the known apparatuses for producing masks of this type envisage stopping the mask bodies for applying the elastic loops for the ears in semi-automatic or manual mode. These apparatuses typically have a production speed in the order of 50 pieces/minute in manual mode and can reach speeds in the order of 175 pieces/minute in semi-automatic mode. 
     These production speeds are largely insufficient for articles of this kind, especially when compared with the production speeds of the most modern machines for producing disposable sanitary articles, for example, absorbent sanitary articles, which reach production speeds in the order of 800-1000 pieces/minute. 
     Another problem of the face protection masks according to the prior art is the difficulty of supplying the elastic threads used for producing the elastic loops for the ears. 
     Another problem of the known solutions is that it is not possible to quickly and efficiently produce masks having elastic threads with different elastic properties. 
     It is known that the elastic properties of elastic threads are fixed and depend mainly on the raw material and the geometry used. This implies that known solutions are scarcely flexible. 
     The known solutions typically only allow production of one type of mask having elastic threads with predefined characteristics on which it is not possible to intervene to produce different batches of masks. 
     If it is intended to obtain batches of masks with different elastic properties, it is necessary to replace the raw material of the elastic threads and possibly make multiple changes to the apparatus for producing the masks. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The present invention aims to provide a face protection mask that can be produced with higher speeds than the face protection masks according to the prior art and that is not affected by problems of finding raw materials. 
     In particular, the invention has the object of making face protection masks by processing the elastic bands directly in line, adapting the specific elastic characteristics according to the specific batch to be made each time. 
     This increases production flexibility as it is possible to manage the elastic bands to be coupled to the masks directly in line and in the required manner. 
     According to another aspect, the invention relates to a method and an apparatus for producing face protection masks that overcome the problems of the prior art. 
     In particular, the object of the present invention is to provide a method and an apparatus for producing face protection masks, which have production speeds that are considerably higher than those of the apparatuses currently available on the market. 
     According to another aspect, the invention relates to a method and an apparatus for producing face protection masks that overcome the problems of the prior art. 
     In accordance with possible embodiments, the present invention relates to a face protection mask comprising a mask body having a longitudinal axis and two side edges, and at least one elastic band parallel to the longitudinal axis and having opposite ends fixed to the respective side edges of the mask body, wherein the at least one elastic band comprises at least one elastic element trapped between two layers of non-woven fabric. 
     According to possible embodiments, the mask body may comprise a non-woven fabric. For example, the mask body may comprise a multilayer of non-woven fabrics optionally where there are one or more additional layers of functional materials such as filter materials. 
     Thanks to the type of elastic band thus formed, it is possible to create multiple types of elastic bands having the most varied and diversified elastic properties each time. 
     According to possible embodiments, in an extended condition of the mask body the at least one elastic band is in a tension-free state. 
     This aspect makes it possible to have a face protection mask that, when not in use, does not have any bending due to the residual tension of the elastic bands that typically occurs in known methods, be they manual or semi-automatic, or even automatic. 
     In accordance with possible embodiments, at least one elastic band comprises a plurality of elastic threads. 
     This aspect makes it possible to modify the elastic properties of the elastic bands as a function of the number of elastic threads, their diameter, their intrinsic elastic properties, the mutual distance, the tension they individually have when they are trapped between the two layers of non-woven fabric and their position along the elastic band which, for example, may be linear, wavy, curved or of another type. A preferred variant envisages that the elastic threads are parallel to each other. 
     According to possible embodiments, at least one elastic band has the two layers of non-woven fabric welded together by means of a plurality of anchor welds. Each anchor weld comprises a pair of welds placed on the sides of one of the elastic threads and spaced apart by a length less than the diameter of said elastic thread at rest, so as to trap the latter between the two layers of non-woven fabric. 
     Diameter means the average diameter that the elastic thread has at rest, or in the case of several threads wound or intertwined with each other, it means the maximum equivalent diameter of the elastic thread assembly. 
     This aspect allows the elastic threads to be trapped without the aid of glue, and also allows obtainment of elastic bands with uniform and separate pleating of the required pitch. 
     In accordance with possible embodiments, at least one elastic band comprises a laminar elastic element. 
     The laminar elastic element can be a web having a width substantially equal to that of the two layers of non-woven fabric. 
     The elastic band may also comprise a plurality of laminar elastic elements, for example, they may comprise a plurality of elastic bands parallel to each other. 
     These embodiments allow obtainment of an elastic band with required elastic properties. In addition, thanks to the flattened shape of the laminar elastic element, which—in use—rests on the back of the head or neck, the elastic band is more ergonomic. 
     According to possible embodiments, the laminar elastic element comprises a plurality of holes through which the two layers of non-woven fabric are welded together. 
     This aspect allows increasing the already high breathability of the elastic bands as the holes in the laminar elastic element allow a greater passage of air. 
     In accordance with possible embodiments, at least one end of the at least one elastic band is fixed to a side edge of the mask body by means of an attachment area having an inclined extension with respect to the longitudinal axis. 
     Thanks to the inclination of the attachment areas of the elastic band, the fit of the mask is significantly improved as the mask body adheres better to the users face at the side edges where the elastic band is welded. 
     According to possible embodiments, the face protection mask comprises two elastic bands adjacent to respective longitudinal edges of the mask body and having respective opposite ends fixed to the mask body along respective attachment areas. 
     This aspect allows a more stable mask in position during use as the two adjacent elastic bands keep the mask body in position, preventing it from moving from the required position. For example, this configuration prevents the nose from being uncovered during the use of the mask while the user speaks, or moves his mouth. 
     In accordance with possible embodiments, an elastic band has a longitudinal extension at rest that is different from that of another elastic band. 
     According to possible embodiments, an elastic band is configured to extend elastically up to a maximum longitudinal extension different from that of another elastic band. By elastic extension, it is meant that the elastic band, once extended, returns to the rest configuration without having undergone a plastic deformation greater than 10% of the length of the elastic band in the rest configuration. 
     Both aspects relating to the diversification between some characteristics between the two elastic bands, whether they are considered together or taken individually, allow masks to be produced with different elastic properties that are not achievable with the known solutions. 
     In accordance with possible embodiments, the attachment areas of a lower elastic band have a greater extension in the longitudinal direction than the extension in the longitudinal direction of the attachment areas of an upper elastic band. 
     This aspect allows obtaining a reduction of the neckline of the lower elastic band to the advantage of a better fit of the mask. 
     According to possible embodiments, the layers of non-woven fabric of an elastic band are formed by a single sheet of non-woven fabric folded along a longitudinal line. 
     This aspect is advantageous since it is not necessary to manage two sheets of non-woven fabric by means of two separate unwinders trying to coordinate them so that the two sheets remain perfectly overlapped. According to this embodiment, it is possible to use a single unwinder for the sheet of non-woven fabric that is folded. 
     In accordance with possible embodiments, at least one of the layers of non-woven fabric is fastened to the mask body in a removable way. 
     This aspect is advantageous above all during the making of the masks since once the layer of non-woven fabric has been attached to the mask body it does not move, and simplifies the subsequent processing along the production line. 
     This aspect also makes it possible to prevent the elastic bands from colliding with or getting entangled in the processing units during movement along the production line. 
     The same considerations are also valid during the packaging step, since it is advantageous for the elastic bands to remain in position on the mask body. 
     To wear these masks, the user only has to break the connection that can be made, for example, by means of technical welds typical in the sector of absorbent hygienic items. 
     According to possible embodiments, the present invention relates to a face protection mask that comprises a mask body having a longitudinal axis and two side edges, and at least one elastic band parallel to the longitudinal axis, and having opposite ends fixed to respective side edges of the mask body, wherein—in an extended condition of the mask body—the at least one elastic band is in a tension-free state. 
     This allows the mask to be maintained without the elastic band exerting a pulling action that bends the mask. 
     According to possible embodiments, the at least one elastic band comprises at least one elastic element fixed between two layers of non-woven fabric. 
     This aspect allows production of masks having elastic bands with required elastic properties directly in line. 
     In other words, it is possible to adjust the elasticity of the elastic bands in relation to how the elastic band is made directly in line, and this is decidedly advantageous with respect to known solutions wherein the elastic properties of the elastic bands are predetermined by the material and shape with which they are provided, without the possibility of modifying them according to the specific needs. 
     In accordance with possible embodiments, in an extended condition of the mask body, the layers of non-woven fabric are pleated. 
     This aspect makes the elastic bands more ergonomic since—in contact with the body—they are softer and also allow greater transpiration of the head and neck compared to known solutions. 
     In accordance with possible embodiments, the present invention also relates to a method for producing face protection masks, comprising:
         forming a succession of mask bodies each having a longitudinal axis and two side edges,   forming a succession of elastic bands, each comprising at least one elastic element trapped between two layers of non-woven fabric,   attaching opposite ends of each of the elastic bands to respective side edges of a respective mask body.       

     This aspect makes it possible to manage the production of the elastic bands directly in line, adapting their characteristics in relation to specific needs. 
     According to possible embodiments, the method envisages that the elastic bands are fixed to respective mask bodies in a tension-free state. 
     This allows the mask bodies to be manipulated and conveyed with the elastic bands, without the need to consider any curvature of the mask due to some residual tension of the elastic bands. 
     In accordance with possible embodiments, the method envisages that the elastic bands are fixed to respective mask bodies while the elastic bands advance in a machine direction at a speed greater than the feed rate of the mask bodies in the same machine direction. 
     This allows attaching of the bands by reducing any residual tension and also allows attaching, again without residual tension, elastic bands longer than the longitudinal extension of the mask bodies. 
     According to possible embodiments, the method envisages that two elastic bands parallel to each other are fixed to each mask body. 
     In accordance with possible embodiments, the method envisages that the lower elastic bands are attached to respective mask bodies at attachment areas having an extension in the longitudinal direction greater than the extension in the longitudinal direction of the attachment areas of the upper elastic bands. 
     According to possible embodiments, the method comprises:
         forming a continuous sheet having a longitudinal axis,   forming at least one continuous elastic band comprising a continuous elastic element trapped between two continuous layers of non-woven fabric,   overlapping at least one continuous elastic band and the continuous sheet, with the continuous elastic band parallel to the longitudinal axis,   attaching together the continuous sheet and the at least one continuous elastic band along attachment areas, and   cutting the continuous sheet and the at least one continuous elastic band along cutting lines.       

     According to possible embodiments, the continuous sheet may comprise a non-woven fabric. According to possible embodiments, the continuous sheet may comprise a multilayer of non-woven fabric possibly in which there are one or more additional layers of functional materials such as filtering materials. 
     According to possible embodiments, the method envisages that the formation of the continuous elastic band envisages applying at least one continuous elastic element on a longitudinal portion of a single sheet of non-woven fabric, and folding the single sheet of non-woven fabric along a longitudinal line so as to trap the at least one continuous elastic element between two superimposed longitudinal portions, wherein the superimposed portions correspond to the two continuous layers of non-woven fabric. 
     In accordance with possible embodiments, the method envisages that the continuous elastic element is fixed between two layers of smooth non-woven fabric in a state stretched in the longitudinal direction, and wherein the continuous elastic band is slowed down before being attached to the continuous sheet of non-woven fabric. 
     According to possible embodiments, the method envisages that the continuous elastic element is fixed between two layers of wavy non-woven fabric. 
     According to possible embodiments, the method envisages that the continuous elastic element is fixed between the layers of wavy non-woven fabric in a non-tensioned state. 
     This allows obtaining considerably greater extensions than those known today wherein the elastic element is fixed in tension between layers of non-wavy non-woven fabric. 
     In accordance with possible embodiments, the present invention also relates to a method for producing face protection masks, comprising:
         forming a succession of mask bodies each having a longitudinal axis and two side edges,   forming a succession of elastic bands,   attaching opposite ends of each elastic band to respective side edges of a respective mask body, wherein the elastic bands are fixed to respective mask bodies in a tension-free state.       

     In accordance with possible embodiments, the method envisages that the elastic bands are pleated when they are fixed to the respective mask bodies. 
     According to possible embodiments, the method comprises:
         forming a continuous sheet having a longitudinal axis,   forming at least one continuous elastic band,   overlapping the at least one continuous elastic band and the continuous sheet, with the continuous elastic band in a tension-free state,   attaching the continuous sheet and the at least one continuous elastic band together in a tension-free state, and   cutting the continuous sheet and the at least one continuous elastic band along cutting lines.       

     In accordance with possible embodiments, the present invention also relates to an apparatus for producing face protection masks, comprising:
         a first forming unit configured to form a continuous web extending along a longitudinal axis,   a second forming unit configured to form at least one continuous elastic band comprising at least one continuous elastic element trapped between two continuous layers of non-woven fabric,   an anvil wheel on which, in use, the at least one continuous elastic band and the continuous sheet are superimposed on each other, with the continuous elastic band parallel to the longitudinal axis,   a fastening device configured to cooperate with said anvil wheel to fasten said continuous sheet and said at least one continuous elastic band together, and   a cutting unit configured for cutting the continuous sheet and the at least one continuous elastic band along cutting lines.       

     According to possible embodiments, the apparatus comprises a slowing device arranged between the second forming unit and the anvil wheel and configured to slow down the continuous elastic band upstream of the anvil wheel. 
     In accordance with possible embodiments, the present invention also relates to an apparatus for producing face protection masks, comprising:
         a first forming unit configured to form a continuous web extending along a longitudinal axis,   a second forming unit configured to form at least one continuous elastic band,   an anvil wheel on which, in use, the at least one continuous elastic band and said continuous sheet are superimposed on each other, with the continuous elastic band in a tension-free state,   a fastening device configured to cooperate with said anvil wheel to fasten said continuous sheet and the continuous elastic band together, and   a cutting unit configured for cutting the continuous sheet and the at least one continuous elastic band along cutting lines.       

     According to possible embodiments, the anvil wheel is configured to advance the at least one continuous elastic band in a machine direction at a speed greater than the speed of advancement of the continuous non-woven fabric sheet in the same machine direction. 
     The claims form an integral part of the disclosure provided here in relation to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described in detail with reference to the attached drawings, given purely by way of non-limiting example, wherein: 
         FIGS.  1  and  2    are perspective views of an embodiment of a face protection mask according to the present invention, 
         FIG.  3    is a plan view of the face protection mask of  FIGS.  1  and  2   , 
         FIG.  4    is a plan view of a second embodiment of a face protection mask according to the present invention, 
         FIGS.  5  and  6    are plan views of two embodiments of the elastic bands of a mask according to the present invention, 
         FIG.  7    is a schematic view of an apparatus for producing face protection masks according to the present invention, 
         FIGS.  8 - 14    are schematic views illustrating various method steps for producing face protection masks according to the present invention, 
         FIG.  15    is a schematic side view of an embodiment of an apparatus for forming elastic bands, 
         FIG.  16    is a schematic perspective view of an elastic band at the outlet of the apparatus in  FIG.  15   , and 
         FIG.  17    is a schematic plan view illustrating an embodiment of a system for forming elastic bands. 
     
    
    
     It will be appreciated that the various figures may not be represented on the same scale. It will also be appreciated that in some figures certain elements or components may not be illustrated to better highlight others and to simplify the understanding of the figures. 
     DETAILED DESCRIPTION 
     A detailed description of the present invention is given below with some variations. This detailed description is exemplary and not limiting, as any further embodiments have also been inserted previously with reference to the synthesis of the invention. 
     With reference to  FIGS.  1 - 3   , numeral  10  indicates a face protection mask according to an embodiment of the present invention. The mask  10  comprises a mask body  12  and at least one elastic band  14 . 
     In the examples illustrated in the figures, the mask  10  comprises two elastic bands  14 , each of which is adjacent to a respective major side of the mask body  12 . In use, the two elastic bands  14  are positioned at different heights on the users head to keep the mask body  12  in position in front of the nose and mouth. The upper elastic band  14  is positioned on the nape and the lower elastic band  14  is positioned behind the users neck. 
     In possible embodiments, the mask  10  may comprise only one elastic band  14 . The single elastic band  14  may have a greater width than each of the elastic bands  14  illustrated in  FIGS.  1 - 3   , and can be arranged in a central area of the mask body  12 . The single elastic band  14  may have a longitudinal cut that divides the elastic band into two branches that can be arranged at different heights on the users head. 
     The mask body  12  is formed by one or more layers of non-woven fabric. In an extended position, the mask body  12  has a flat shape elongated along a longitudinal axis A, and has two longitudinal edges  16  and two side edges  18 . 
     In a possible embodiment, the mask body  12  may be constituted by three layers of non-woven fabric superimposed on each other. For example, the inner layer may be made of a Thermal-Bond material, the intermediate layer of a Meltblown material and the outer layer of a Spunbond material. 
     The mask body  12  has a series of folds  20  parallel to the longitudinal axis A that extend for the entire length of the mask body  12 . 
     The mask body  12  may comprise a nose clip  21  formed by a bar of plastically-deformable material, arranged parallel to the upper longitudinal edge  16  and having the object of shaping the upper edge of the mask body  12  around the users nose. The nose clip  21  may, for example, consist of a thin metal bar coated with a plastic material, for example polyethylene. The nose clip  21  may be held inside a folded longitudinal edge  16  of the mask body  12 . The folded longitudinal edge  16  may be attached to the outer face or the inner face of the mask body  12  by ultrasonic welding, glue or thermal welding. In a possible embodiment, both longitudinal edges  16  of the mask body  12  can be folded and fixed to the outer face or the inner face of the mask body  12  by ultrasonic welding, glue or thermal welding. 
     In the example illustrated in  FIG.  1   , the mask body  12  has a rectangular shape wherein the two longitudinal edges  16  are straight and parallel to the longitudinal axis A, and the two side edges  18  are straight and perpendicular to the longitudinal axis A. In this embodiment, the elastic bands  14  have the same length as the mask body  12 . 
     In possible embodiments, the longitudinal edges  16  and/or the transverse edges  18  can be non-straight, and can be shaped in various ways. For example, in the embodiment illustrated in  FIG.  4   , the side edges  18  of the mask body  12  may have respective central recessed sections  22 , with a C-shape facing outwards. The central recessed portions  22  of the side edges  18  are comprised between the two elastic bands  14 . In this embodiment, the elastic bands  14  have a length that is greater than the length of the central part of the mask body  12  comprised between the central recessed portions  22  of the side edges  18 . 
     Each elastic band  14  is parallel to the longitudinal axis A, and may have an outer longitudinal edge parallel and aligned with a corresponding longitudinal edge  16  of the mask body. 
     The elastic bands  14  have respective opposite ends which are fixed to the mask body  12  along respective attachment areas  24 ′,  24 ″ located in the vicinity of the respective side edges  18  of the mask body  12 . The attachment of the opposite ends of each elastic band  14  to the mask body  12  may be carried out by means of glue, ultrasonic welding or thermal welding. 
     With reference to  FIGS.  3  and  4   , in a possible embodiment, the attachment areas  24 ′ of the lower elastic band  14  (the one located along the longitudinal edge  16  opposite to the one bearing the nose clip  21 ) have an extension in the longitudinal direction greater than the attachment areas  24 ″ of the upper elastic band  14  (the one located along the longitudinal edge  16  carrying the nose clip  21 ). In this way, the lower elastic band  14 , which in use is positioned on the users neck, has a lower effective length than the upper elastic band  14 , which in use is positioned on the users nape and must be lengthened to a greater extent than the lower elastic band  14 . In the embodiment illustrated in  FIG.  4   , the attachment areas  24 ′ of the lower elastic band  14  can extend substantially for the entire length of the section of the mask body  12  that extends laterally beyond the recessed part  22 . 
     The elastic bands  14  in addition to being fixed to the mask body  12  in the side attachment areas  24 ′,  24 ″ may also be fixed to the mask body  12  in intermediate areas between the side attachment areas  24 ′,  24 ″ by means of technical connecting points, for example, by means of technical welding points or by means of technical glue points, which form temporary connecting points intended to be interrupted with a weak release force. In this way, the elastic bands  14  remain adherent to the mask body  12  during production and packaging. The technical connecting points keep the elastic bands  14  neatly in the packaging and before use the technical connecting points can be easily detached. 
     In a possible embodiment, in an extended configuration of the mask body  12  the elastic bands  14  are in a non-tensioned state. Therefore, in the extended configuration of the mask body  12 , the elastic bands  14  do not apply any force to the mask body  12 . This prevents the mask body  12  from assuming an arcuate shape at rest. Therefore, at rest, the mask body  12  has a planar configuration, which simplifies the production and packaging operations. 
     Each elastic band  14  comprises two layers of non-woven fabric  26 , and at least one elastic element sandwiched between the two layers of non-woven fabric  26 . The elastic element is fixed between the two layers of non-woven fabric  26  by any of the techniques normally used for producing elastic bands in the sector of producing absorbent sanitary articles, for example, by means of glue, ultrasonic welding or thermal welding. 
     In a possible embodiment, the two layers of non-woven fabric  26  of each elastic band  14  can be formed by a single sheet of non-woven fabric folded along a longitudinal edge. 
     The layers of non-woven fabric  26  may be of Spunbonded-Meltblown-Spunbonded (SMS) material, or of Thermal Bond material, and may have a grammage measured according to the EDANA NWSP 130.1 regulation between 10 and 20 g/cm 2 , in particular, between 12 and 15 g/cm 2 . 
     In a possible embodiment, in an extended condition of the mask body  12 , the layers of non-woven fabric  26  of the elastic bands  14  can be pleated. 
     In the embodiment illustrated in  FIG.  5   , each elastic band  14  comprises a plurality of elastic threads  28 , parallel to each other, fixed to the two layers of non-woven fabric  26  by joining lines  30 . The joining lines  30  may have a transverse trend and can be spaced apart from each other in the longitudinal direction. 
     The joining lines  30  can be formed by welding points that weld the two layers of non-woven fabric  26  together and anchor the elastic threads  28  to the two layers of non-woven fabric  26 . The welding points can be spaced apart from each other in a transverse direction by a distance smaller than the diameter of the non-tensioned elastic threads. The elastic threads  28  can be arranged between the two layers of non-woven fabric  26  in a tensioned state and, while the elastic threads  28  are tensioned, the two layers of non-woven fabric  26  are welded together by means of welding points arranged on opposite sides of the tensioned elastic threads  28 , and spaced apart from each other by a distance smaller than the diameter of the non-tensioned elastic threads. When the tension of the elastic threads is released, the elastic threads remain anchored to the layers of non-woven fabric  26  at the welding points. 
     In a possible embodiment, the layers of non-woven fabric  26  may be welded together with a welding pattern comprising anchor welds spaced apart in a transverse direction by a distance less than the diameter of the non-tensioned elastic wires, and welds of containment spaced apart from each other in a transverse direction by a distance greater than the diameter of the non-tensioned elastic threads. 
     In a possible embodiment, the layers of non-woven fabric  26  can be fixed to each other by means of transverse glue lines spaced apart from each other in the longitudinal direction. 
     The elastic threads  28  can be made of Lycra® and may have a denier between 480 and 1500 dtex, or between 800 and 1200 dtex. 
     In the embodiment illustrated in  FIG.  6   , each elastic band  14  comprises a laminar elastic element  32  arranged sandwiched between the two layers of non-woven fabric  26 , and fixed thereto by means of a plurality of welding points  34 , which join together the two layers of non-woven fabric  26  on opposite sides of the laminar elastic element  32 . The welding points  34  may form corresponding through-holes  36  through the laminar elastic element  32  that make the elastic band  14  breathable. 
     The laminar elastic element may consist of an elastic polyolefin film. 
     With reference to  FIG.  7    and  FIGS.  8 - 14   , an apparatus and a method for producing face protection masks  10  of the type described above will now be described. 
     In  FIG.  7   , numeral  40  indicates a continuous flow apparatus for producing face protection masks  10 . “Continuous flow apparatus” means an apparatus in which the semi-finished products move continuously without pauses or stops until the finished product is obtained. 
     The apparatus  40  may comprise a first forming unit  42  configured for the in-line formation of a sheet of multilayer non-woven fabric  44 , for example, by overlapping three layers of non-woven fabric  45 . Alternatively, the non-woven fabric sheet  44  could be supplied in reels and fed to the apparatus  40  by unwinding devices. 
     The apparatus  40  comprises a feed unit  46  configured to advance the continuous sheet of non-woven fabric  44  along a machine direction X. 
     The apparatus  40  comprises a folding device  48  configured to form continuous folds on the continuous moving sheet  44  parallel to the machine direction X. Downstream of the folding device  48 , a pressure device  50  can be arranged to compress the continuous sheet  44  on which the continuous longitudinal folds  20  have been formed. 
     A continuous thread  52  of plastically-deformable material is unwound from a reel  54  and is fed in the machine direction X parallel to a longitudinal side of the continuous fabric  44 . A cutting and applying device  56  cuts the continuous thread  52  so as to form a succession of clips for the nose  21 , which are applied to the continuous sheet  44  in the vicinity of one of its longitudinal edges. A longitudinal folding device  58  folds the longitudinal edges of the continuous sheet  44 . Downstream of the longitudinal folding device  58 , a second pressure device  60  can be provided to compress the continuous sheet  44 . Then, the continuous sheet  44  passes through an ultrasonic welding device  62 , which carries out the ultrasonic welding of the folded longitudinal edges. Alternatively, the apparatus could be equipped with a glue applicator for attaching the folded longitudinal edges with glue or with a thermal welding device. 
       FIG.  8    illustrates the continuous sheet of non-woven fabric  44  at the outlet of the forming unit  42 .  FIG.  9    illustrates the continuous sheet of non-woven fabric  44  after the formation of the longitudinal folds  20  and the application of the nose clips  21 , and  FIG.  10    illustrates the continuous sheet of non-woven fabric  44  after folding and welding of the longitudinal edges  16 . The continuous sheet of non-woven fabric  44  in the configuration of  FIG.  10    is formed by a continuous succession of mask bodies  12 . 
     With reference to  FIG.  7   , the apparatus  40  comprises a second forming unit  64  configured for the in-line formation of at least one continuous elastic band  66 . In a possible embodiment, the second forming unit  64  is configured to form two continuous elastic bands  66  parallel to each other. 
     The second forming unit  64  is configured to enclose at least one continuous elastic element  68  between two continuous layers of non-woven fabric  70 . The continuous elastic element  68  can be formed by a plurality of continuous elastic threads parallel to each other or by a film of continuous laminar material. The second forming unit  64  may comprise two applicator rollers  72 , which apply the two continuous layers of non-woven fabric  70  on opposite sides of the continuous elastic element  68 . The continuous elastic element  68  may be fed to the applicator rollers  72  by means of a feeding device indicated schematically with  74 , which can be configured to feed the continuous elastic element  68  in a tensioned state. 
     The apparatus  40  comprises a fastening device  76  arranged downstream of the second forming unit  64 , configured to attach the two continuous layers of non-woven fabric  70  together and anchor the continuous elastic element  68  between the two continuous layers of non-woven-fabric  70 . The fastening device  76  may, for example, be formed by an ultrasonic welding apparatus. 
     In a possible embodiment, the two continuous layers of non-woven fabric  70  of each continuous elastic band  66  may be formed by a single continuous sheet of non-woven fabric folded along a longitudinal edge. 
     With reference to  FIG.  11   , downstream of the fastening device  76  two continuous elastic bands  66  parallel to each other are obtained, each of which comprises an elastic element  68  enclosed between two continuous layers of non-woven fabric  70 , wherein the continuous elastic element  68  and the layers of non-woven fabric  70  are attached together along joining lines  30 . The joining lines  30 , which can be formed by ultrasonic welding spots, can be oriented in the transverse direction and can be spaced apart from each other in the longitudinal direction. 
     In possible embodiments, the attachment of the elastic element  68  between the two continuous layers of non-woven fabric  70 , for example, by means of joining lines  30 , to form the continuous elastic bands  66 , can be obtained in the ways previously described with reference to  FIG.  5   . 
     With reference to  FIG.  7   , the apparatus  40  comprises a slowing device  78  arranged downstream of the fastening device  76 , and configured to slow down the continuous elastic bands  66 . The slowing device  78  may comprise a roller  80  on which the continuous elastic bands  66  are wound and driven in rotation with a rotation speed such that the peripheral speed of the roller  80  is less than the speed at which the continuous elastic bands  66  are fed to the roller entrance  80 . At the outlet of the slowing device  78 , the feed rate of the continuous elastic bands  66  is lower than the speed of advancement of the continuous elastic bands  66  upstream of the slowing device  78 . During the passage through the slowing device  78  the elastic tension of the continuous elastic elements  68  decreases in proportion to the reduction in the feed rate of the continuous elastic bands  66 . The slowing device  78  can be controlled so that the elastic tension of the continuous elastic bands  66  at the outlet of the slowing device  78  has a value close to zero. 
     With reference to  FIG.  12   , the reduction of the tension of the continuous elastic bands  66  causes—at the outlet of the slowing device  78 —the layers of non-woven fabric  70  of the continuous elastic bands  66  to assume a pleated or wavy shape. In the configuration of  FIG.  12   , the continuous elastic bands  66  are formed by a continuous succession of elastic bands  14  intended to be applied to respective mask bodies  12 . 
     With reference to  FIG.  7   , the apparatus  40  comprises a welding unit  82  configured to weld together the continuous sheet of non-woven fabric  44 , formed by a continuous succession of mask bodies  12 , and the continuous elastic bands  66 , formed by a continuous succession of elastic bands  14 . The welding unit  82  comprises an anvil wheel  84  rotating around its axis, and an ultrasonic welding device  86  cooperating with the outer surface of the anvil wheel  84 . The continuous sheet of non-woven fabric  44  and the continuous elastic bands  66  are fed jointly on the outer surface of the anvil wheel  84  in the machine direction X upstream of the ultrasonic welding device  86  in a superimposed condition, with the elastic bands continuous sheets  66  aligned with the respective longitudinal edges of the continuous sheet of non-woven fabric  44 . 
     With reference to  FIG.  13   , the ultrasonic welding unit  82  welds together the continuous elastic bands  66  and the continuous non-woven fabric  44  at regular intervals, and forms attachment areas  24 ′,  24 ″ between the elastic bands  14  and the respective mask bodies  12 . The ultrasonic welding unit  82  can also carry out the transversal welding of the continuous sheet of non-woven fabric  44  in the section between the two elastic bands  66  to form the welding of the side edges  18  of the mask bodies  12 . As shown in  FIG.  13   , the attachment areas  24 ′ of the lower elastic bands  14  may have an extension in the longitudinal direction that is greater than the extension in the longitudinal direction of the attachment areas  24 ″ between the upper elastic bands  14 . 
     According to a characteristic of the present invention, the ultrasonic welding unit  82  is configured to attach the elastic bands  14  to the respective mask bodies  12  with a complete absence of elastic tension of the elastic bands  14 . According to an embodiment of the present invention, the cancellation of the elastic tension of the continuous elastic bands  66  is obtained by advancing the continuous elastic bands  66  upstream of the ultrasonic welding device  86  at a speed greater than the feed rate of the mask bodies  12 . The difference between the feed rate of the continuous elastic bands  66  and that of the mask bodies  12  may be obtained by holding the continuous elastic bands  66  in contact with the outer surface of the anvil wheel  84 , and by driving the anvil wheel  84  in rotation with a rotation speed such that the peripheral speed of the anvil wheel  84  is greater than the speed of advancement in the machine direction X of the continuous web of non-woven fabric  44 . 
     Since the continuous elastic bands  66  downstream of the slowing device  78  are almost free of elastic tension, it is advisable for the continuous elastic bands  66  to be supported and guided in the path between the slowing device  78  and the anvil wheel  84 . For this object, the apparatus  40  may comprise one or more conveyors  88  arranged between the slowing device  78  and the anvil wheel  84 , and configured to guide the continuous elastic bands  66  towards the outer surface of the anvil wheel  84 . Each of the conveyors  88  may comprise two closed-loop conveyor belts that tighten the elastic bands  66  together. 
     With reference to  FIG.  13   , at the outlet of the welding unit  82 , a continuous composite sheet is obtained formed by a succession of finished masks  10  joined together. 
     With reference to  FIG.  7   , the apparatus  40  includes a cutting unit  90  configured to cut the continuous composite sheet to separate the finished individual masks  10  from each other. The cutting unit  90  cuts the continuous elastic bands  66  and the continuous non-woven fabric sheet  44  along cutting lines indicated by  92  in  FIG.  13   . At the outlet of the cutting unit  90 , individual masks  10  are obtained having the shape shown in  FIG.  14   . 
     To form the masks  10  according to the embodiment illustrated in  FIG.  4   , the cutting unit  90  makes the cut along a cutting path including two straight portions at the elastic bands  66  and a closed loop path at the continuous sheet of non-woven fabric  44  between the two elastic bands  66 . In this way, a scrap is formed with a shape corresponding to that of the closed-loop cutting path between each pair of masks  10  adjacent to each other. The scraps can be evacuated by means of a suction device. 
     In possible embodiments, the continuous sheet of non-woven fabric  44  can be cut to form individual mask bodies  12  upstream of the welding unit  82 . The continuous elastic bands  66  may be cut so as to form individual elastic bands  14  upstream or downstream of the welding device  86 . 
       FIG.  15    schematically illustrates a second embodiment of a unit  64  for forming elastic bands  66 . The forming unit  64  comprises a pair of gears  94  cooperating with each other. Each of the gears  94  cooperates in turn with an additional gear  96 . Two continuous sheets of non-woven fabric  70  are passed between each pair of wheels  94 ,  96 . The toothed wheels  94 ,  96  impart a wavy shape to the respective sheets of non-woven fabric  70 . A continuous elastic element  68  is fed by a feeding device  74  between the two gears  94 , and is enclosed between the two corrugated sheets of non-woven fabric  70 . The continuous elastic element  68  can be formed by a plurality of elastic threads  28  parallel to each other, as shown in  FIG.  16   , or by a laminar film. At the outlet of the forming unit  64 , the two wavy non-woven fabric sheets  70  are fixed together by welding or glue to anchor the elastic element  68  between the two wavy non-woven fabric sheets  70 . At the outlet of the forming unit  64 , a pleated elastic band  66  is thus obtained having the shape shown in  FIG.  16   . The forming unit  64  can be configured to form two elastic bands  66  parallel to each other. 
     In a possible embodiment, the continuous elastic element  68  can be fed between the two wavy non-woven fabric sheets  70  in a non-tensioned state. In this way, at the outlet of the forming unit  64 , at least one pleated elastic band  66  is obtained wherein the elastic elements  68  are tension-free. In this case, the at least one elastic band  66  may be fed directly to the anvil wheel  84  without first passing through a slowing device  78 . 
     In a possible embodiment, the continuous elastic element  68  can be fed between the two wavy non-woven fabric sheets  70  in a tensioned state. This can be achieved by operating the feeding device  74  so that it feeds the continuous elastic element  68  at a speed lower than the speed of the two wavy non-woven fabric sheets  70 . In this way, at the outlet of the forming unit  64 , at least one wavy elastic band  66  is obtained in which the elastic elements  68  are tensioned. This allows obtainment of elastic bands  66  wherein the undulations of the non-woven fabric sheets  70  are particularly compact. 
       FIG.  17    schematically illustrates a system that makes it possible to obtain two continuous elastic bands  66  starting from a single sheet of non-woven fabric  98 . The non-woven fabric sheet  98  is cut in a longitudinal direction so as to form two longitudinal sections  100 . On each of the two longitudinal sections  100  a continuous elastic element  68  is applied that can be formed by a plurality of elastic threads  28  parallel to each other or by a laminar elastic film. Each continuous elastic element  68  occupies only one half of the respective longitudinal section  100 . Then, each longitudinal section  100  is folded around a longitudinal line  102  so as to enclose the continuous elastic element  68  between two layers of non-woven fabric formed by two overlapping halves of the longitudinal section  100 . 
     The apparatus according to the present invention makes it possible to carry out a continuous cycle production process with a production speed in the order of 800-1000 pieces/1′. 
     The method and the apparatus according to the present invention allow production of the finished masks without any direct human contact with the products. It is, therefore, possible to pack the masks in sterile packages and ensure the absence of contamination. 
     Of course, without prejudice to the principle of the invention, the details of construction and the embodiments can be widely varied with respect to those described and illustrated, without thereby departing from the scope of the invention as defined by the claims that follow.