Patent Publication Number: US-8109229-B2

Title: Spreading head particularly for spreading one or more adhesives or mixtures of adhesives

Description:
The present invention relates to a spreading head particularly for spreading one or more adhesives or mixtures of adhesives, both of the hot-melt type and of the cold type. 
     BACKGROUND OF THE INVENTION 
     Currently it is known to use, for the application of adhesives to substrates made of various materials such as for example fabrics or ribbons made of plastic material, spreading devices which comprise one or more spreading heads provided with a duct for feeding the adhesive, the delivery end of which faces, during use, a substrate which is made to advance in close contact therewith in the form of a ribbon. 
     The adhesive is introduced in the duct in the liquid state, typically by means of appropriately provided gear pumps, and can be applied either continuously or intermittently, by throttling the flow thereof by means of appropriately provided valves of a known type which are arranged in the spreading head. 
     Such valves further allow to vary the width of the region of application of the adhesive and to perform throttlings of said adhesive, with a preset pitch, transversely to the ribbon of substrate. 
     As an alternative to the valves, the variation of the width of the region of application of the adhesive can also be achieved by means of one or more inserts of a known type, which can be arranged automatically or manually within the duct so as to partially obstruct its cross-section, so as to adapt its width to the width of the tape. 
     It is also known to insert, transversely to the duct, appropriately provided contoured laminas, which are suitable to obstruct said duct partially so as to be able to obtain a chosen distribution of the adhesive transversely to the substrate; it is thus possible to achieve, for example, a distribution of the adhesive which affects uniformly the entire substrate or also a distribution of the so-called “multiline” type, which is constituted by a plurality of longitudinal layers of adhesive which are mutually parallel and spaced. 
     These known types of spreading head, however, have drawbacks: first of all, they do not allow to obtain layers of different adhesives arranged side-by-side or laterally adjacent layers of a same adhesive with different grammages. 
     Moreover, the use of these known types of head entails a waste of adhesive if an adhesive of higher value and/or grammage (therefore also having a structural function) is required only in some regions of the substrate while in other regions an adhesive of lower value and/or grammage is sufficient, since it forces to use the higher-value and/or higher-grammage adhesive for all the regions of the substrate. 
     Moreover, said known types of head allow to obtain only a uniform film of adhesive in contact with both surfaces of the materials to be coupled; this entails the need to use a high-value adhesive even if its use is required only by one of the two surfaces to be coupled, with an additional waste of material. 
     Further, if the substrate is porous, the use of known types of head entails an additional waste of high-value adhesive, since said adhesive also acts as a filler for the pores of the substrate. 
     There are also applications in which said known types of head are used to provide membranes which in some regions must have breathability characteristics, and therefore require low grammages of applied adhesive, and in other regions must instead provide a vapor barrier effect and therefore require high adhesive grammages; to obtain this embodiment, known types of head require a double passage over the substrate, which is performed either with different heads or with a same head which is modified at a later time, and this increases the production times, and therefore the production costs, of producing said membranes. 
     Moreover, in the case of adhesives that have to be mixed with catalysts before they are spread, mixing must be performed before injection into the head, and this causes severe problems if it is necessary to stop the machine, since the adhesive, after being mixed with the catalyst, must be spread onto the substrate in a short time. 
     Further, if subsequent productions require the use of adhesives with different chemical properties and/or colorings, and said properties and/or colorings are mutually incompatible, it is necessary to clean the heads before applying the new adhesive, and this requires complete disassembly of the heads and the full cleaning of all the ducts, with consequent long times and high costs for execution. 
     Moreover, since many thermoplastic adhesives have a residual stickiness after their spreading, it is not possible to apply them with a double pass. 
     In the case of cold adhesives, spreading heads are known which allow to apply a plurality of superimposed layers; however, said heads do not allow to perform combined applications, i.e., multilayer products in certain regions and single-layer products in other regions, and also do not allow intermittent and/or combined applications of the so-called “multiline” type. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to solve the above mentioned problems, eliminating the drawbacks of the cited background art, by providing a spreading head which allows to spread one or more adhesives onto a substrate, so as to obtain, in chosen regions thereof, layers of the chosen type of chosen adhesive and/or of the chosen grammage. 
     Within this aim, an object of the invention is to provide a spreading head which allows to obtain, even in a single pass, the spreading onto a substrate of two or more superimposed layers of one or more adhesives. 
     Another object of the invention is to allow the mixing of a plurality of adhesives or of an adhesive and a catalyst, limiting the head cleaning time and further reducing the waste of adhesive that has already been mixed with a catalyst if the spreading process is interrupted. 
     Another object is to provide a spreading head which allows to achieve the spreading of one or more adhesives in a plurality of layers which are arranged side-by-side and optionally mutually spaced, in which each layer has the chosen characteristics of width and/or composition and/or grammage and/or number of superimposed layers that compose it. 
     Another object of the invention is to facilitate the operations for cleaning the spreading head. 
     Another object is to provide a spreading head which allows the spreading in rapid succession of adhesives having different chemical properties and/or colorings, which may even be mutually incompatible. 
     Another object of the invention is to reduce the time and cost for producing membranes which have breathable regions and vapor-permeable regions. 
     Another object of the invention is to reduce the waste of high-value adhesive in the process for spreading it onto a substrate, even a porous one. 
     Another object of the invention is to achieve a reduction in the costs for spreading one or more adhesives onto a substrate. 
     Another object is to provide a spreading head which is structurally simple and has low manufacturing costs. 
     This aim and these and other objects, which will become better apparent hereinafter, are achieved by a spreading head particularly for spreading one or more adhesives or mixtures of adhesives, of the hot-melt or cold type, comprising a body for conveying said one or more adhesives to an extrusion tool, characterized in that said body has two or more ducts, which are all separate or of which two or more converge, and in that said tool has one or more first extrusion channels and/or one or more mixing chambers which are connected to one or more second extrusion channels, said first and/or second extrusion channels being optionally mutually superimposed and/or laterally adjacent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the invention will become better apparent from the following detailed description of a particular but not exclusive embodiment thereof, illustrated by way of non-limiting example in the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a spreading head according to the invention during its use; 
         FIG. 2  is a schematic transverse sectional view of the spreading head of  FIG. 1 , in which the valves have not been shown and the second feed channels have been highlighted, said channels actually being not visible because they are arranged on different planes; 
         FIG. 3  is a perspective view of a detail of the extrusion tool of a spreading head according to the invention; 
         FIG. 4  is a perspective view of a detail of a second embodiment of the extrusion tool of a spreading head according to the invention; 
         FIG. 5  is a perspective view of a detail of a third embodiment of the extrusion tool of a spreading head according to the invention; 
         FIG. 6  is a schematic view of the flows of adhesives in a spreading head according to the invention; 
         FIG. 7  is a transverse sectional view of a particular operating condition of a head according to the invention, in which the second feed channels have been highlighted, said channels actually being not visible because they are arranged on different planes; 
         FIG. 8  is a transverse sectional view, which highlights the second feed channels, which are actually not visible because they are arranged on different planes, of a simplified configuration of a head according to the invention, which corresponds to the particular operating condition given in the description with reference to  FIG. 7 ; 
         FIG. 9  is a perspective view of the head of  FIG. 7 ; 
         FIG. 10  is a schematic view of the path of the flows of the adhesives in the operating condition described for  FIG. 7 ; 
         FIG. 11  is a view of a detail of the extrusion tool of the simplified configuration shown in  FIG. 8 ; 
         FIG. 12  is a view of another particular operating condition of a head according to the invention in a transverse cross-section which highlights also the first extrusion channels and the fourth feed channels, which are actually not visible; 
         FIG. 13  is a transverse sectional view of a simplified configuration of a head according to the invention which corresponds to the particular operating configuration given in the description which refers to  FIG. 12 ; 
         FIG. 14  is a perspective view of the head of  FIG. 12 ; 
         FIG. 15  is a schematic view of the path of the flows of the adhesives in the operating condition of  FIG. 12 ; 
         FIG. 16  is a view of a detail of the extrusion tool of the simplified configuration shown in  FIG. 13 ; 
         FIG. 17  is a transverse sectional view of another particular operating condition of a head according to the invention, illustrating also the first extrusion channels and the fourth feed channels, which are actually not visible; 
         FIG. 18  is a transverse sectional view of a simplified configuration of a head according to the invention, which corresponds to the particular operating condition given in the description which refers to  FIG. 17 ; 
         FIG. 19  is a perspective view of the head of  FIG. 17 ; 
         FIG. 20  is a schematic view of the path of the flows of the adhesives in the operating condition of  FIG. 17 ; 
         FIG. 21  is a view of a detail of the extrusion tool of the simplified configuration shown in  FIG. 18 ; 
         FIG. 22  is a transverse sectional view of another particular operating condition of a head according to the invention; 
         FIG. 23  is a transverse sectional view of a simplified configuration of a head according to the invention, which corresponds to the particular operating condition given in the description that refers to  FIG. 22 ; 
         FIG. 24  is a perspective view of the head of  FIG. 22 ; 
         FIG. 25  is a schematic view of the path of the flows of the adhesives in the operating condition of  FIG. 22 ; 
         FIG. 26  is a view of a detail of the extrusion tool of the simplified configuration shown in  FIG. 23 ; 
         FIG. 27  is a transverse sectional view of a particular operating condition of a head according to the invention; 
         FIG. 28  is a transverse sectional view of a simplified configuration of a head according to the invention which corresponds to the particular operating condition given in the description with reference to  FIG. 27 ; 
         FIG. 29  is a view of a detail of the extrusion tool of the simplified configuration shown in  FIG. 28 ; 
         FIG. 30  is a schematic view of the provision of a double layer by using the operating condition of  FIG. 29 ; 
         FIG. 31  is a transverse sectional view of another particular operating condition of a head according to the invention; 
         FIG. 32  is a transverse sectional view of a simplified configuration of a head according to the invention, which corresponds to the particular operating condition given in the description with reference to  FIG. 31 ; 
         FIG. 33  is a view of a detail of the extrusion tool of the simplified configuration shown in  FIG. 32 ; 
         FIG. 34  is a schematic view of the provision of a triple layer by using the operating condition of  FIG. 33 ; 
         FIG. 35  is a schematic view of a different embodiment of the head according to the invention, highlighting the second feed channels, which are actually not visible because they are arranged on different planes; 
         FIG. 36  is a perspective view of a detail of the extrusion tool of the spreading head of  FIG. 35 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the exemplary embodiments that follow, individual characteristics, given in relation to specific examples, may actually be interchanged with other different characteristics that exist in other exemplary embodiments. 
     Moreover, it is noted that anything found to be already known during the patenting process is understood not to be claimed and to be the subject of a disclaimer. 
     With reference to the accompanying figures, the reference numeral  1  generally designates a spreading head, particularly for one or more adhesives or mixtures of adhesives, of the hot-melt or cold type, on an appropriately provided substrate  60  constituted for example by a tape made of fabric or plastic material. 
     The spreading head  1  is constituted by a body  2  for conveying such one or more adhesives to an extrusion tool, designated by the reference numeral  3 . 
     Advantageously but not necessarily, the body  2  is approximately shaped like a parallelepiped with a transverse cross-section which is approximately shaped like a right-angled trapezoid. 
     Two or more ducts are formed within the body  2 ; all of said ducts are separate or two or more of them converge. 
     With reference to  FIGS. 1 and 2 , the body  2  has a first duct and a second duct, designated respectively by the reference numerals  4  and  5 , which are approximately mutually parallel and affect longitudinally the body  2 , preferably along most of its width; advantageously, the first and second ducts  4  and  5  respectively have one or more first and second accesses, designated respectively by the reference numerals  4 ′ and  5 ′, from which it is possible to introduce, for example by means of appropriately provided rotary pumps, not shown in the accompanying figures, one or more adhesives or mixtures of adhesives or catalysts for adhesives. 
     Advantageously, the first and second ducts  4  and  5  mutually converge inside the body  2 ; the first and second ducts  4  and  5  are connected respectively to first and second output ducts, designated respectively by the reference numerals  6 , and  7 , which converge in pairs, with the interposition of appropriately provided first and second valves of a known type, designated respectively by the reference numerals  8  and  9 , within appropriately provided mixing channels  10 , from each of which a first feed channel  11  protrudes which is connected in output to the extrusion tool  3 . 
     Advantageously, the first and second output ducts  6  and  7  are formed along axes which are substantially perpendicular to the first and second ducts  4  and  5 ; the first and second output ducts  6  and  7  are present in a chosen number and are distributed, in a preferably equidistant arrangement, respectively along the first and second ducts  4  and  5 . 
     With reference to  FIGS. 1 and 2 , the body  2  has a third duct  12 , which is approximately parallel to the first and second ducts and again affects longitudinally the body  2  preferably along most of its width. 
     The third duct  12  has one or more third accesses  13  for an adhesive or a mixture of adhesives or catalyst for adhesives. 
     One or more second feed channels  14  exit from the third duct  12 , are connected in output to the extrusion tool  3 , and are connected to the third duct  12  by means of appropriately provided third valves  15  of a known type; advantageously, the outputs of the second feed channels  14  and of the first feed channels  11  are aligned along a same longitudinal axis with respect to the body  2 . 
     Advantageously, the second feed channels  14  are formed along axes which are substantially perpendicular to the longitudinal axis of the third duct  12 ; the second feed channels  14  are provided in a chosen number and are distributed, preferably in an equidistant configuration, along the third duct  12 . 
     The body  2  further has a fourth duct and a fifth duct, designated respectively by the reference numerals  16  and  17 , which are approximately parallel to the first, second and third ducts and affect longitudinally the body  2  preferably along most of its width; the fourth and fifth duct  16  and  17  respectively have fourth and fifth accesses, designated respectively by the reference numerals  18  and  19 , for an adhesive or a mixture of adhesives or catalysts for adhesives. 
     Respectively one or more third feed channels  20  and one or more fourth feed channels  21  exit from the fourth and fifth ducts  16  and  17 , are connected in output to the extrusion tool  3  and are connected to the respective fourth and fifth ducts respectively by means of appropriately provided fourth and fifth valves of a known type, designated respectively by the reference numerals  22  and  23 . 
     Advantageously, the outputs of the third and fourth feed channels  20  and  21  are aligned respectively along two axes which are arranged longitudinally with respect to the body  2  and are substantially parallel and spaced with respect to each other and with respect to the axis along which the outputs of the first and second feed channels  11  and  14  are aligned. 
     Advantageously, the third and fourth feed channels  20  and  21  are formed along axes which are substantially perpendicular respectively to the longitudinal axes of the fourth and fifth ducts  16  and  17 ; the third and fourth feed channels  20  and  21  are provided in a chosen number and are distributed, preferably equidistantly, respectively along the fourth and fifth ducts  16  and  17 . 
     Advantageously, the extrusion tool  3  is constituted by a lower element  24 , which can be fixed to the contiguous body  2  and is preferably shaped approximately like a parallelepiped, with a transverse cross-section shaped like a right-angled trapezoid arranged so that its shorter parallel side  25  engages the body  2  and its longer parallel side  26  is directed away from it. 
     One or more first extrusion channels, designated by the reference numerals  27   a  and  27   b , are formed in the lower element  24  of the extrusion tool  3 , and are optionally mutually superimposed and/or laterally adjacent; each channel is connected in input to one of the first and/or second and/or third and/or fourth feed channels which exit from the body  3 . 
     In the example shown in the accompanying figures, the first extrusion channels  27   a  and  27   b  are connected respectively to the third feed channels  20  and to the fourth feed channels  21  formed within the body  2 . 
     The embodiment shown in  FIG. 3  shows multiple pairs of first extrusion channels  27   a  and  27   b , which are mutually superimposed in pairs (i.e., are arranged parallel to each other and to the longitudinal axis of the lower element  24 ) and are also mutually laterally adjacent in pairs; hereinafter, the first extrusion channel  27   a , which lies closest to the perimetric edge  26   a  of the longer parallel side  26  which during use is directed toward the substrate  60  will be also referenced as front channel, and the adjacent first extrusion channel  27   b  will be also referenced as rear channel. 
     The longitudinal extension of the first extrusion channels  27   a  and  27   b  of each pair is identical, while the longitudinal extension of two laterally adjacent pairs of said first extrusion channels  27   a  and  27   b  may be different. 
     Advantageously, in each pair of first mutually superimposed extrusion channels  27   a  and  27   b  the outlet of the first extrusion channel arranged in a rearward position (the channel  27   b  with reference to  FIG. 3 ) is, with respect to the throttling plane, at a greater elevation than the adjacent first channel arranged in a forward position (the one designated in  FIG. 3  by the reference numeral  27   a ). 
     As described hereinafter, the plane of arrangement of the first (front) extrusion channel  27   a  which is adjacent to the first (rear) extrusion channel  27   b  lies at a lower level than the first (rear) extrusion channel  27   b , in order to allow to extrude two superimposed layers of adhesive which, after flowing out of the respective first channel  27   a  or  27   b , remain one on top of the other due to their different relative densities. 
     As an alternative, as shown in  FIG. 4 , there can be one or more additional first extrusion channels, designated by the reference numeral  27   c , which have different configurations and arrangements with respect to the first extrusion channels  27   a  and  27   b ; the additional first extrusion channels  27   c  are arranged along an axis which is perpendicular to the axis of the first extrusion channels  27   a  and  27   b  and is interposed between each of the pairs of the first extrusion channels  27   a  and  27   b.    
     The additional first extrusion channels  27 c extend from the perimetric edge  26   a  of the longer parallel side  26  of the lower element  24  which during use is directed toward the substrate  60 ; as described in greater detail hereinafter, this configuration of the first extrusion channels allows to obtain in output laterally adjacent layers of adhesive spaced by microlayers of reduced width. 
     Advantageously, one or more mixing chambers  28  can further be provided in the lower element  24  of the extrusion tool  3 , each chamber being connected to one or more second extrusion channels  29 , which like the first extrusion channels  27   a  and  27   b  are optionally superimposed and/or laterally adjacent with respect to each other and/or with respect to the first extrusion channels  27   a ,  27   b ; in the example shown in the accompanying figures, the second extrusion channels  29  are mutually laterally adjacent, and each channel is superimposed on a pair of first extrusion channels  27   a  and  27   b.    
     The configuration and therefore the size of the second extrusion channels  29  follow those of the first extrusion channels  27   a  and  27   b  at each of the pairs of the channels on which they are superimposed. 
     As described hereinafter, the plane of arrangement of each second extrusion channel  29  is at a higher level than the adjacent first (rear) extrusion channel  27   b , in order to allow the extrusion of three superimposed layers of adhesive which, after flowing out respectively from the second extrusion channel  29  and from the adjacent first extrusion channels  27   a  and  27   b , remain one on top of the other due to their different relative densities. 
     As illustrated schematically in  FIG. 6  (in which, for the sake of clarity, the mixing channel  10  has not been shown), each mixing chamber  28  is connected to at least one of the first and at least one of the second feed channels  11  and  14  formed within the body  2 ; in this manner, it is possible to make two or more different adhesives (shown in  FIG. 6  by means of two shadings with opposite inclinations), or a chosen adhesive and the respective catalyst, converge in the mixing chambers  28  in order to achieve mixing directly within the extrusion tool  3 . 
     As described, the various pairs of first extrusion channels  27   a ,  27   b  which are mutually superimposed and the adjacent second extrusion channels  29  may have mutually different extensions; thus, for example, as shown in  FIGS. 3 ,  4  and  5 , some pairs of first extrusion channels  27   a  and  27   b  which are mutually superimposed and the adjacent second extrusion channels  29  may have a shorter extension than the pairs of first extrusion channels  27   a  and  27   b  which are mutually superimposed and than the adjacent second extrusion channels  29 , allowing to obtain in output layers of adhesive which are laterally adjacent and have different widths. 
     Advantageously, on the longer parallel side  26  of the lower element  24  of the extrusion tool  3  there is a slit  30 , provided preferably by removing material and so as to affect the outlet of at least the first (front) extrusion channels  27   a : said slit arranges on a lower plane the outlet of the first (front) extrusion channel  27   a  with respect to the plane of arrangement of the first (rear) extrusion channel  27   b  and of the second extrusion channel  29 . 
     The slit  30  guides the outflow of the layer or layers of adhesive from the extrusion tool  3  onto the substrate  60 . 
     In another embodiment, shown in  FIG. 5 , one or more of the first extrusion channels  27   a ,  27   b  and/or of the additional first extrusion channels  27   c  and/or of the second extrusion channels  29  may have, along an axis which lies longitudinally with respect to the lower element  24 , reduced lengths so as to constitute microchannels which are designated by the reference numerals  50   a  and  50   b.    
     In the embodiment shown in  FIG. 5 , the microchannels  50   a  and  50   b  are arranged at right angles to the first and second extrusion channels, are mutually parallel and are interposed between two pairs of the first and second extrusion channels  27   a ,  27   b  and  29 . 
     The configuration of the microchannels  50   a  and  50   b  with respect to the longer parallel side  26  of the lower element  24  of the extrusion tool  3  is preferably comb-like, with teeth which advantageously have two different lengths and are arranged preferably alternately. 
     Advantageously, the extrusion tool  3  further comprises an upper element  31 , which can be fixed to the longer parallel side  26  of the lower element  24  and is preferably approximately shaped like a parallelepiped, with a transverse cross-section shaped like a right-angled trapezoid. 
     The upper element  31  therefore acts as an abutment for the adhesive or adhesives that exit from the first and second channels formed in the lower element  24 , thus guiding the adhesive or adhesives to exit from the slits  30 . 
     Operation is therefore as follows: with reference to the accompanying figures, it is possible to introduce, for example by means of appropriately provided rotary pumps, not shown in the accompanying figures, one or more adhesives or mixtures of adhesives in the liquid state, or optionally one or more appropriately provided catalysts, in one or more among the first duct  4 , the second duct  5 , the third duct  12 , the fourth duct  16  and the fifth duct  17 . 
     By adjusting appropriately the open or closed state of the first, second, third, fourth and fifth valves, it is possible to feed into the extrusion tool  3  the chosen adhesive or mixture of adhesives so as to obtain, in output from the extrusion tool  3 , a chosen configuration of the spread layer or layers of adhesive. 
     For example, with reference to  FIGS. 7 to 11 , it is possible to feed just the first duct  4  and the third duct  12  with two separate adhesives or alternately with the same adhesive having a different grammage, or also with an adhesive and an appropriately provided catalyst. 
     As shown in  FIG. 10 , by opening one or both of the first and third valves which are interposed respectively between the first duct  4 , the third duct  12  and a same mixing chamber  28 , it is possible to allow the access to the mixing chamber  28  of just one or both of the adhesives or mixture of adhesives or adhesive and catalyst that are present respectively in the first duct  4  and in the third duct  12 . 
     If, as shown in  FIG. 10 , both the first valve  8  and the third valve  15  are open, in the mixing chamber  28  mixing occurs between the two adhesives or between the adhesive and the catalyst, contained respectively in the first and third ducts; from the mixing chamber  28 , through the second extrusion channel  29 , the mixture of adhesives or the adhesive mixed with the catalyst is then extruded by the extrusion tool  3  through the slit  30 . 
     As an alternative, if only one of the first and third valves respectively of the first feed channel  11  and of the second feed channel  14  that lead into a same mixing chamber  28  is open, only one of the two adhesives flows into said chamber and therefore exits directly from the extrusions tool  3 . 
     In this manner it is therefore possible to obtain a plurality of layers of adhesive  32  which are laterally mutually adjacent and have the chosen composition; the embodiment shown in  FIG. 9 , for example, obtains a first layer  32   a  of a first adhesive, a second layer  32   b  of a second adhesive and a third layer  32   c , which is interposed laterally between the preceding ones and is constituted by a mixture thereof. 
     This distribution of the layers of adhesive in output can also be achieved with a simplified configuration of the spreading head  1  in which the body  2  has only the first duct  4  and the third duct  12 , from which a corresponding number of first and second feed channels  11  and  14  exit respectively through one or more first valves  8  and third valves  15 . 
     In this simplified configuration, the extrusion tool  3  does not have the first extrusion channels but only one or more mixing chambers  28 , each of which is connected in input to a first feed channel  11  and to a second feed channel  14  and in output to a second channel  29 ; as shown in  FIG. 11 , the various second extrusion channels  29  in this case are mutually laterally adjacent. 
     With reference to  FIGS. 12 to 16 , it is further possible to feed only the third duct  12  and the fourth duct  16  with two separate adhesives or as an alternative with a same adhesive having a different grammage. 
     As shown in  FIG. 15 , by appropriately adjusting the opening of the third valves  15  and fourth valves  22  it is possible to make the two adhesives converge within the microchannels  50   a  and  50   b  alone. 
     If, as shown in  FIGS. 13 ,  15  and  16 , in the extrusion tool  3  there are only the microchannels  50   a  and  50   b , it is possible to spread an alternation of microlayers, generally designated by the reference numeral  33 , of the two adhesives. 
     With reference to  FIGS. 13 ,  15  and  16 , the distribution of the adhesive layers in output can also be achieved with a simplified configuration of the spreading head  1 , in which the body  2  has only the third duct  12  and the fourth duct  16 , from which a corresponding number of second and third feed channels  14  and  20  protrude respectively through one or more third valves  15  and fourth valves  22 . 
     In this simplified configuration, the extrusion tool  3  is not provided with the mixing chambers  28  but only, as shown in  FIGS. 13 ,  15  and  16 , with the microchannels  50   a  and  50   b , which are arranged in a comb-like configuration, are mutually alternated and are connected in input respectively to the second feed channels  14  and to the third feed channels  20 . 
     With reference to  FIGS. 17 to 21 , it is further possible to feed only the third duct  12  and the fourth duct  16  with two separate adhesives or, as an alternative, with a same adhesive having a different grammage; as shown in  FIG. 17 , by means of the third valves  15  and the fourth valves  22  is possible to make one of the two adhesives converge into the mixing chambers  28  and from there into the second extrusion channels  29  and make the other adhesive converge into the additional first extrusion channels  27   c  which are interposed between the various second extrusion channels  29  which are arranged laterally side-by-side. 
     It is therefore possible to obtain in output from the extrusion tool  3  a series of layers of adhesive  32  which are laterally adjacent and are spaced by microlayers  33  of a different adhesive. 
     For example, with reference to the embodiment shown in  FIG. 19 , six layers  32  of a first adhesive, each enclosed between two microlayers  32  of a second adhesive, have been obtained. 
     With reference to  FIGS. 18 and 21 , this distribution of the layers of adhesive in output can also be achieved with a simplified configuration of the spreading head  1 , in which the body  2  has only the third duct  12  and the fourth duct  16 , from which a corresponding number of second and third feed channels  14  and  20  exit respectively through one or more third valves  15  and fourth valves  22 . 
     In this simplified configuration, the extrusion tool  3  does not have the first extrusion channels below the second extrusion channels  29  but has only the additional first extrusion channels  27   c , which are smaller and are arranged between the latter. 
     With reference to  FIGS. 22 to 26 , it is further possible to feed only the third duct  12  and the fourth duct  16  with two separate adhesives or, as an alternative, with a same adhesive having a different grammage; the third duct  12  and the fourth duct  16  are connected respectively to the mixing chambers  28  and therefore to the second extrusion channels  29  and to the first extrusion channels  27   b  which are contiguous to these last. 
     By acting on the open condition of the third valves  15  and the fourth valves  22  it is possible to make one or the other of the adhesives flow respectively to the second extrusion channels  29  or the contiguous first extrusion channels  27   b ; in this manner, it is possible to obtain in output from the extrusion tool  3  a series of layers of adhesive  32  which are laterally mutually adjacent and have the chosen composition. 
     In the embodiment shown in  FIG. 24 , for example, two first layers  32   a  of a first adhesive and two second layers  32   b  of a second adhesive, arranged alternately with respect to each other, have been obtained. 
     By opening both the third valve  15  and the fourth valve  22 , which control the input respectively into a second extrusion channel  29  and into a first extrusion channel  27   b  arranged below the latter, it is possible to make both adhesives exit simultaneously from said first and second superimposed extrusion channels, so as to achieve the spreading of a double layer. 
     With reference to  FIGS. 23 and 26 , this distribution of the layers of adhesive in output can also be achieved with a simplified configuration of the spreading head  1 , in which the body  2  has only the third duct  12  and the fourth duct  16 , from which a corresponding number of second and third feed channels  14  and  20  exit respectively through one or more third valves  15  and fourth valves  22 . 
     In this simplified configuration, the extrusion tool  3  has only a series of first extrusion channels  27   b  which are arranged below the second extrusion channels  29 ; one adhesive or the other can be fed respectively to a first channel  27   b  or to the overlying second extrusion channel  29  by opening or closing the respective fourth and third valves. 
     With reference to  FIGS. 27 to 30 , it is possible to feed the first duct  4  and the second duct  5  with two separate adhesives or with an adhesive and an appropriate catalyst and then the fifth duct  17  with an additional adhesive. 
     By opening the first and second valves  8  and  9 , the adhesive or adhesives and the catalyst contained respectively in the first and second ducts enter the mixing channel  10 , from which they exit, after being mixed, by means of the first extrusion channels  11 , entering the mixing chambers  28  of the extrusion tool  3  and finally exiting from it by means of the second extrusion channels  29 . 
     By opening the fifth valves  23 , the adhesive contained in the fifth duct  17  enters the fourth feed channels  21  and then exits from the first (front) extrusion channels  27 a arranged below the second extrusion channels  29 . 
     As shown in  FIG. 30 , the adhesive that exits from the second extrusion channels  29  and the adhesive that exits from the underlying first (front) extrusion channels  27   a  are extruded simultaneously; said adhesives remain one on top of the other due to their different relative densities, thus forming a double layer, designated in  FIG. 30  by the reference numeral  34 , which is composed of a lower layer  34   a  of the first adhesive (which arrives from the fourth feed channels  21 ) and an upper layer  34   b  of the second adhesive (which arrives from the first feed channels  11 ). 
     By closing the first and second valves which enter a given mixing channel  10 , or one of the fifth valves  23 , it is also possible to achieve the extrusion of a single layer of adhesive or mixture of adhesives, respectively from one of the first (front) extrusion channels  27   a  or of the second extrusion channels  29 ; it is thus possible to obtain in output a chosen distribution of adhesives, not shown in the accompanying figures, which is constituted by a series of laterally adjacent layers, one or more of which is constituted by a single layer of one adhesive or the other, and one or more of which is constituted by a double layer which is similar to the one designated by the reference numeral  34  in  FIG. 30 . 
     With reference to  FIGS. 28 ,  29  and  30 , this distribution of the adhesive layers in output can also be achieved with a simplified configuration of the spreading head  1  in which the body  2  has only the first duct  4  and the second duct  5  which mutually converge in a suitable mixing channel  10  with the interposition of the first and second valves; the body  2  further has the fifth duct  17  which is connected, by means of the fifth valves  23 , to the fourth feed channels  21 . 
     In this simplified configuration, the extrusion tool  3  has only one series of first extrusion channels  27   a  which are arranged below the second extrusion channels  29 . 
     With reference to  FIGS. 31 to 34 , it is further possible to feed the third duct  12 , the fourth duct  16  and the fifth duct  17  with separate adhesives and/or with the same adhesive at different grammages. 
     By opening the third valves  15 , the fourth valves  22  and the fifth valves  23 , these adhesives enter respectively the second feed channels  14 , the third feed channels  20  and the fourth feed channels  21  and from there flow into the extrusion tool  3 . 
     The three adhesives thus exit simultaneously respectively from the first two extrusion channels  27   a  and  27   b  and from the second extrusion channel  29  so as to be mutually superimposed, forming a triple layer, designated in  FIG. 34  by the reference numeral  35 , which is constituted by a lower layer  35   a  of the first adhesive (which arrives from the fourth feed channels  21 ), by an intermediate layer  35   b  of the second adhesive (which arrives from the third feed channels  20 ), and by an upper layer  35   c  of the third adhesive (or optionally again of the first adhesive) (which arrives from the second feed channels  14 ). 
     By closing selectively the third, fourth and fifth valves, it is further possible to achieve the extrusion of a single layer of adhesive or also of a double layer; one can thus obtain in output a distribution of adhesives, not shown in the accompanying figures, which is constituted by a series of laterally adjacent layers, of which one or more is constituted by a single layer of a chosen adhesive and optionally one or more is constituted by a double layer and one or more is constituted by a triple layer. 
     With reference to  FIGS. 32 ,  33  and  34 , this distribution of the layers of adhesives in output can also be achieved with a simplified configuration of the spreading head  1 , in which the body  2  has only the third, fourth and fifth ducts and the respective third, fourth and fifth valves, through which said ducts are connected respectively to the second, third and fourth feed channels. 
     In this simplified configuration, the extrusion tool  3  has multiple pairs of first extrusion channels  27   a  and  27   b  which are arranged below a second extrusion channel  29  and are laterally mutually adjacent. 
     It has thus been found that the invention has achieved the intended aim and objects, a spreading head having been devised which allows to apply to chosen areas of a substrate a chosen adhesive and/or different adhesives and/or a same adhesive with different grammages and/or a multiple layer of adhesives. 
     The spreading head according to the invention therefore allows to provide areas with differentiated grammage and also using differentiated adhesives, so as to be able to reduce (even by 70%, as has been found) the amount of (more expensive) structural adhesive that is required. 
     Further, the spreading head according to the invention allows to achieve the spreading on a substrate of a chosen number of layers of adhesive arranged side-by-side and having a chosen width. 
     Moreover, the spreading head according to the invention allows to mix various adhesives or an adhesive and a suitable catalyst both within the body and within the extrusion tool. 
     The spreading head according to the invention further allows to use sequentially adhesives which are chemically compatible with each other, since before applying the new adhesive it is sufficient to replace the extrusion tool; this reduces machine downtime with respect to the background art. 
     Moreover, the spreading head according to the invention allows in particular to achieve the mixing of the adhesives only in the extrusion tool, thus limiting the waste of already-mixed adhesive and the time required to clean the head, and further obviating product contaminations. 
     In the case of adhesives that must be mixed with catalysts, the spreading head according to the invention allows to provide said mixing directly in the extrusion tool, and this solves all the problems of circuit cleaning and allows to avoid wasting already-mixed product in case of machine downtime. 
     By means of the spreading head according to the invention it is further possible to achieve, even in a single pass, the spreading of a multilayer film of adhesives, so as to be able to use products with a good grip on different substrates. 
     Thanks to the possibility to achieve the spreading of adhesives in multiple layers, the need is further avoided to use high-value adhesives even if their use is required only by one of the two surfaces to which they are to be applied. 
     Moreover, in cases in which the adhesive, in addition to having a structural function, also has the task of “filling” porous surfaces (for example in the lamination of recycled products or of products on chipwood panel substrates), the spreading head according to the invention allows to reduce the waste of “high-value” product, by making a low-cost resin perform the nonstructural function and making a thin layer of high-value resin perform the structural effect. 
     Further, the spreading head according to the invention allows to provide, even with a single pass, a membrane which has breathability characteristics in certain regions and a vapor barrier effect in others. 
     Moreover, the spreading head according to the invention is suitable for use for spreading thermoplastic adhesives and cold adhesives. 
     Moreover, the spreading head according to the invention allows the alternating application of hot and cold adhesives, since transition from one type of adhesive to the other merely entails replacing the extrusion tool. 
     Moreover, the production costs of the spreading head according to the invention remain low, since it is made of components which are easy to manufacture and/or assemble. 
     The invention is of course susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. 
     Thus, for example,  FIGS. 35 and 36  illustrate a spreading head  101  in which the extrusion tool  103  is constituted by a single block which is preferably shaped, in a transverse cross-section, approximately like a right-angled trapezoid and is superimposed, with its lower surface  136 , on the underlying upper surface  137  of the body  102  at the outlets of the first feed channel  111 , of the second feed channel  114 , of the third feed channel  120  and of the fourth feed channel  121 . 
     In this embodiment, the first extrusion channels formed in the extrusion tool  103  are each constituted by a first cavity  138   a ,  138   b , which is formed in the lower surface  136  of the extrusion tool  103  and faces the outlet of one of the first, second, third and fourth feed channels formed in the body  102 . 
     In the embodiment shown in  FIGS. 35 and 36 , the first cavities  138   b  and  138   a  face respectively the third feed channels  120  and the fourth feed channels  121  formed within the body  102 . 
     In the embodiment shown in  FIG. 36 , multiple pairs of first cavities  138   a  and  138   b  are shown which are arranged so as to be mutually superimposed in pairs (i.e., arranged parallel to each other and to the longitudinal axis of the extrusion tool  103 ) and are also laterally adjacent in pairs; hereinafter, the first cavity  138   a  which during use lies closest to the substrate  160  will also be referenced as front cavity and the adjacent first cavity  138   b  will be referenced also as rear cavity. 
     As shown in  FIG. 36 , the longitudinal extension of each pair of first cavities  138   a  and  138   b  is identical, while the longitudinal extension of two laterally adjacent pairs of first cavities  138   a  and  138   b  may be different. 
     In this embodiment, each mixing chamber and the respective one or more second extrusion channels are constituted by a single second cavity  139 , which is formed in the lower surface  136  of the extrusion tool  103  and faces the outlet of one of the first, second, third and fourth feed channels formed within the body  102 . 
     In the embodiment shown in  FIGS. 35 and 36 , the second cavities  139  face respectively the first feed channels  111  and/or the second feed channels  114  which are formed within the body  102 . 
     Advantageously, each second cavity faces respectively at least one first feed channel  111  and at least one second feed channel  114 , so as to allow the simultaneous introduction therein (and the consequent mixing therein) of two different adhesives or of an adhesive and a suitable catalyst. 
     Advantageously, the second cavities  139  are optionally superimposed and/or laterally adjacent to each other and/or to the first cavities  138   a ,  138   b ; in the example shown in  FIGS. 35 and 36 , the second cavities  139  are mutually laterally adjacent, each cavity being superimposed on a pair of first cavities  138   a  and  138   b.    
     The shape, and therefore the size, of the second cavities  139  follows the shape and size of the first cavities  138   a  and  138   b  at each of the pairs thereof on which they are superimposed. 
     The various pairs of first cavities  138   a ,  138   b  which are mutually superimposed and the adjacent second cavities  139  may have mutually different extensions; thus, for example, as shown in  FIG. 36 , some pairs of first cavities  138   a ,  138   b  which are mutually superimposed and the adjacent second cavities  139  can have a shorter extension than the pairs of first cavities  138   a  and  138   b  which are mutually superimposed and of the second adjacent cavities  139 , allowing to obtain in output laterally adjacent adhesive layers of different width. 
     Advantageously, one or more recesses  140  are formed on the lower surface  136  of the extrusion tool  103 , preferably by removing material and so that each one affects a pair of first cavities  138   a ,  138   b  which are mutually superimposed and the adjacent second cavities  139 , said recesses being suitable to allow the outflow of the adhesive or of the mixture of adhesives from the extrusion tool  103 . 
     Advantageously, the one or more recesses  140  have a constant thickness and are formed along a plane which is approximately perpendicular to the lamination plane. 
     Operation is therefore as follows: with reference to  FIGS. 35 and 36 , for each pair of first mutually superimposed cavities  138   a ,  138   b  and adjacent second cavity  139  it is possible to cause the convergent flow, from the underlying first, second, third or fourth feed channels alternately into one of the first cavities  138   a  or  138   b  or into the second cavity  139 , of an adhesive or a mixture of adhesives, or also, in the case of the second cavity  139 , of an adhesive and an appropriately provided catalyst. 
     The adhesive or mixture of adhesives or adhesive and catalyst thus converge in the chosen cavity among the first or second cavities, filling it until it overflows from it; once it has exited from the respective first or second cavity, the flow of adhesive or mixture of adhesives, depending on the position of the first or second cavity from which it flows out, can be extruded directly by the tool  103 , through the recesses  140 , or can optionally enter and then exit from the contiguous first and/or second cavities to be finally extruded through the recesses  140 . 
     Of course, the materials used, as well as the dimensions that constitute the individual components of the invention, may be more pertinent according to specific requirements. 
     The various means for performing certain different functions need not certainly coexist only in the illustrated embodiment but can be present per se in many embodiments, including ones that are not illustrated. 
     Of course, the selection of the feed to the extrusion tool of the chosen type of adhesive and/or mixtures of adhesives and/or catalysts can occur not only by activating or not activating the mentioned preset valves but also by virtue of equivalent means, such as for example the interposition of appropriately provided plates which are selectively perforated between the body and the extrusion tool. 
     The characteristics indicated as advantageous, convenient or the like may also be omitted or be replaced with equivalents. 
     The disclosures in Italian Patent Application No. TV2006A000124 from which this application claims priority are incorporated herein by reference.